Relationships of phytogeography and diversity of tropical tree

Relationships of phytogeography and diversityof tropical tree species with limestonetopography in southern BelizeSteven W. Brewer1*, Marcel Rejmanek2, Molly A. H. Webb3 and Paul V. A. Fine4

1Department of Biology, Rhodes College, Memphis, TN, 2Section of Evolution and Ecology,

University of California, Davis, CA, 3Department of Fisheries and Wildlife, Oregon State

University, Corvallis, OR and 4Department of Biology, University of Utah, Salt Lake City,

UT, USA

Abstract

Aim The flora of northern Mesoamerica conventionally has been thought to be derivedfrom taxa that emigrated from South America, but this view has recently been challengedas too simple. The dominance of limestone substrata in much of northern Mesoamerica,and its rarity in the rest of the continental Neotropics, may be one cause of thecomplexity of northern Mesoamerican floristics. Furthermore, northern Mesoamericaexperiences longer and more intense seasonal drought than the rest of the continentalNeotropics. As edaphic drought is accentuated with elevation on limestone soils, it maybe expected that different topographic features have different phytogeographicalaffinities for seasonally drought-prone areas of the Neotropics. The objective of thisstudy was to test for effects of different topographic positions on the composition,phytogeography and diversity of tree species in a limestone area of Belize.

Location Maya Mountains, Belize, Mesoamerica.

Methods The diversity and local, regional, and hemispheric distributions of tree specieson limestone valley floors, lower and upper slopes, and ridges were compared insouthern Belize using 2 · 500 m transects as sample plots.

Results Stem density increased, and percentage of large trees decreased, significantlywith elevation above the valley floors. The proportions of species that had widespreaddistributions decreased significantly with increasing elevation above the valley floors.The proportions of species having northern Mesoamerican distributions increasedsignificantly with elevation above the valley floors. All of the forests generally had thestrongest phytogeographical affinities for the Peten (Guatemala) and Mexico, butgreater affinities for the Yucatan were observed with increasing elevation above thevalley floors. Species with distributions including the Greater Antilles made up anincreasingly significant element, in terms of species and numbers of stems, withincreasing elevation above the floors of valleys. Valley floors and ridges had the highestpercentages of species unique to their topographic positions, 61% and 39% of theirspecies, respectively, and were very similar in diversity. Slope forests had the highestdiversity of trees ‡ 5 cm d.b.h. and were transitional in composition among the top-ographic positions.

Main conclusions Despite relatively small changes in elevation, the composition,diversity and physical structure of the limestone forests changed significantly withtopography. Such changes were presumably due to the greater edaphic droughtexperienced by these forests, and possibly due to lower levels of disturbance and dif-ferences in forest age, with increasing elevation above the floors of valleys.

*Correspondence: Steven W. Brewer, Department of Biology, Rhodes College, Memphis, TN 38112, USA. E-mail: [email protected]

Journal of Biogeography, 30, 1669–1688

� 2003 Blackwell Publishing Ltd

Keywords

Karst, Mesoamerica, Maya Mountains, tree species diversity, elevation gradient.

INTRODUCTION

The flora of northern Mesoamerica conventionally has beenthought to be derived from taxa that emigrated from SouthAmerica around the time of the Great American Interchange(Gentry, 1982; Cronquist, 1988). Recently, however, thisview of Mesoamerican floristics has been demonstrated to bean oversimplification. Studies evaluating floristic andpaleobotanical evidence demonstrate complex multiple ori-gins of the flora of northern Mesoamerica (Wendt, 1993;Burnham & Graham, 1999). One reason for the incompletedominance of Amazonian-derived taxa in northern Mesoa-merica may be the presence of soil types that are virtuallyabsent from South America.

Northern Mesoamerica is unique for the continentalNeotropics in being dominated by limestone substrata andkarst terrain (Snead, 1980). Tropical, limestone outcrop soilsare typically shallow and experience stronger seasonaldrought than other soils of rain forest areas. They often haverapid drainage, high fertility, and have a relatively high pHand high organic matter content compared with many othertropical soils (Beard, 1944; Wright et al., 1959; Furley &Newey, 1979; Richards, 1996). Consequently, limestonesoils appear to be occupied by unique floras (Crowther,1982; Proctor et al., 1983; Wendt, 1993; Richards, 1996),but few studies have intensively investigated tropical forestsover limestone because of the restricted distributions of thissubstrate and the difficulty of working in tropical karst ter-rain (Kelly et al., 1988; Richards, 1996).

The forests of northern Mesoamerica remain largelyundescribed, as research into the structure, composition, anddynamics of Neotropical forests has been concentratedmostly in southern Mesoamerica and South America (e.g.Gentry, 1988, 1990; Condit et al., 1998; Dallmeier &Comiskey, 1998). A noteworthy exception is the well-knownforest of Los Tuxtlas, Veracruz, Mexico (Gonzalez-Sorianoet al., 1997); this forest, however, is on a volcanic substrate.Most of the detailed studies of the floristics of tropical for-ests over limestone are from Malaysia and Indonesia (Chin,1977; Crowther, 1982; Proctor et al., 1983; Polak, 2000),China (Hua, 2002), or the Caribbean (Proctor, 1986; Kellyet al., 1988; Borhidi, 1996; Rivera et al., 2000).

Topography and associated changes in elevation are sur-rogate variables for many factors that determine plantgrowth and distribution, such as exposure to winds anddisturbance, temperature, soil depth, water availability anddrainage, and nutrient status. It is therefore not surprisingthat studies throughout the tropics consistently illustrate theinfluence of topography on the composition and distributionof tree species (Ashton, 1964; Basnett, 1992; Pitman et al.,1999; Rennolls & Laumonier, 2000). Furthermore, speciesrichness generally declines with elevation, but there are

many exceptions (Rahbek, 1995), because elevation mayrepresent multiple environmental gradients. Some observa-tions indicate that slope forests in the Neotropics are morediverse than adjacent lowland or valley floor forests (FrenchGuiana: Halle et al., 1978; Mexico: Wendt, 1993; Panama:Leigh, 1996; Bolivia: Foster, 1991; Smith & Killeen, 1998).To our knowledge, however, quantitative comparisons ofthe phytogeography and diversity of tree species amongtopographic positions have not been published for forests ofnorthern Mesoamerica.

Given the strong effects of limestone on soils and drainage(Furley & Newey, 1979; King et al., 1986), different topo-graphic positions in karst terrain are expected to have dif-ferent species composition and diversity, because smalldifferences in elevation intensify the effects of seasonaldrought. Wendt (1993) observed that compared with deepersoils nearby, limestone outcrops of southern Veracruz har-bour a greater proportion of species that are endemic tonorthern Mesoamerica. Brewer & Webb (2002) found thatthe tree flora of a limestone valley floor in Belize was domi-nated by widespread Neotropical species and was unusuallydiverse for northern Mesoamerica. Based on these studiesand preliminary observations, we hypothesized that withincreasing elevation, tree species composition on limestonewould increasingly include species restricted to northernMesoamerica (northern species) and that species diversitywould increase with elevation above the valley floors. Wethen conducted a study of the geographical distributions, andthe richness and diversity, of tree species at different topo-graphic positions on limestone in southern Belize.

Study area

Belize encompasses c. 22,275 km2 of the base of the YucatanPeninsula, between 15 and 19�N latitude. The geology of thewet, southern half of the country is dominated by the MayaMountains, where the study area, the Bladen Nature Reserve(BNR), is located (16�24¢34¢¢–16�36¢18¢¢ N latitude). Theclimate of the area can be classified as tropical wet seasonal(Walsh, 1996), with an annual rainfall of 2500–3000 mmand a strong dry season from February to May. The BNR isc. 350 km2 in area and encompasses the watershed of theBladen Branch of the Monkey River, which runs from higherelevations in the south-west through the middle of the BNRto the north-east (Fig. 1). The south-east half of the water-shed is composed of Coban (late Cretaceous) limestone, andthe north-west half is composed of Bladen (Paleozoic) vol-canic formations, with pockets of alluvium beside the riverand its tributaries (Bateson & Hall, 1977). Evergreen forests(sensu Beard, 1944) grow on these pockets of alluvium andare surrounded by long and continuous, steep limestoneslopes that rise c. 150–200 m from the floors of the valleys to

� 2003 Blackwell Publishing Ltd, Journal of Biogeography, 30, 1669–1688

1670 S. W. Brewer et al.

the ridges. Surrounding these slopes the topography iscomplex, including cone karst (knolls), rock outcrops, pla-teaus, shallow and deep sinkholes, etc. The alluvial soils aredeep (‡ 1 m), fairly well-drained clay loams, and the soils onthe slopes are shallow (mostly < 0.5 m) and rocky, verywell-drained clay loams. The forest canopy is increasinglydeciduous with elevation above the alluvial forests.

The last significant human occupation of the area was bythe Maya on a relatively small scale in the valleysc. 1000 years before present (yr BP) (Abramiuk, 1999;P. Dunham, pers. comm.). As in most of the Neotropics,however, some mahogany (Swietenia macrophylla King) andcedar (Cedrela odorata L.) were removed from the area inmore recent times. Approximately 120 yr BP a smallmahogany logging operation was conducted in the north-eastpart of the watershed (Fowler, 1879), and c. 60 yr BP sometrees were removed from the south-western part of the BNR(P. Dunham, pers. comm.), but large mahogany trees are notuncommon throughout the BNR (S. Brewer, pers. obs.).

METHODS

Field methods and collections

Forests on valleys (alluvial forests on the floors of valleys,with < 5% inclination, indicated by a �V� prefix in theanalyses), lower slopes (forests on the lower third of theslopes next to the valley floor, �L�), upper slopes (forests on

the upper third of the slopes, �U�) and ridges (R) weresampled along elevational gradients at three sites in thewatershed in 1999 and 2002 (Fig. 1). These topographicpositions were selected because of their unambiguous defi-nition, comparative ease in location, and their relation to soilmoisture and other properties as reflected by previous studiesin Belize (Furley & Newey, 1979 and references therein). Assample plots (SPs), belt transects, rather than regular plots,were best suited to following contours that represented thetopographic positions and were more feasible for rapidsampling of the variation within and among the topographicpositions in the difficult terrain of the BNR. The methodused here was a modification of Gentry’s (1982, 1988)method, which has become one standard for rapid samplingof plant diversity in tropical forests (Phillips & Miller,2002). In the dry season of 1999, one transect 2 · 500 m(0.1 ha) was placed within each topographic position, alongcontour lines and skipping over treefall gaps in the canopy.While gaps are an important constituent of tropical forests,the irregular occurrence and highly variable physical struc-ture of gaps would require an order of magnitude increase inthe number of SPs to account for their effect on variation indiversity and composition. This was not justified given theobjectives of the study. Orientation and percentage slopewere measured at six points spaced evenly along each SP.The valley SPs were placed 50–60 m away from the base ofthe nearby slope, and the lower slope and upper slope SPswere placed in the middle of the lower and upper thirds of

Figure 1 The three study sites in Bladen Nature Reserve, in the Maya Mountains of Belize, Central America. Elevation ranges from valley

floors to ridges at sites 1, 2 and 3 are 190, 180 and 160 m, respectively. Central America image courtesy of NASA/JPL/Caltech. Insetmap � Belize Foundation for Research and Environmental Education, used with permission.


Phytogeography and limestone topography in Belize 1671

the slope face at each site, respectively. The precise locationof the beginning of a given SP was determined haphazardly.

The three sites were 10 km apart and were located in thefar north-eastern part of the BNR, where the Bladen Branchbegins to emerge from the main gorge of the watershed (site1; elevation range ¼ 60–250 m), the approximate middle ofthe watershed (site 2; elevation range ¼ 140–320 m), andthe upper part of the watershed (site 3; elevationrange ¼ 240–400 m) (Fig. 1). The sites were chosen toreduce variability, other than topographic position andsubstrate, and were selected to: (1) represent separate,approximately equally spaced locations in the watershed, (2)consist of mature-phase forest, (3) have similar orientationsof the slopes (all approximately north-facing), and (4) haveslope faces that were of similar overall inclination and totalelevation change from their respective valley forests. Treesthat were within SPs were identified and their diametermeasured at 130 cm above the soil surface (d.b.h. or diam-eter). A tree was counted if it had a d.b.h. ‡ 5 cm and if thecentre of the base of its stem was within the SP. Treesincluded all woody, free-standing plants (including palms)‡ 5 cm d.b.h. Palms with developed stems, regardless ofdiameter, were also included in the surveys. Lianas were notincluded in the surveys.

Voucher specimens were collected for all tree species, withthe exceptions of species that were common and distinctive,and for which there was no confusion about their identity(e.g. Schizolobium parahyba, Attalea cohune; see Appen-dix 1 for species names and authorities). Morphospecies thatcould not be reliably separated from known species wereincluded with the known species for the analyses (< 1% ofall stems encountered). Morphospecies that could not beidentified to family were included in the analyses of diversity;they represented < 3% of all species encountered and justfive of nearly 1800 stems sampled. Less than 6% of allspecies (10 stems) could not be identified to species. Dis-tributions of voucher specimens are available from the firstauthor.

Data analyses

The species sampled in this study were classified into one ofthree major phytogeographical categories: (1) northernMesoamerican species endemic to or primarily found in thearea north of central Nicaragua (see Wendt, 1993 andGentry, 1982 for discussions of what constitutes northernCentral America), (2) species endemic to or primarilyoccurring throughout Mesoamerica, and (3) widespreadspecies reaching South America, found in Amazonia or far-ther south. For these analyses, the very rare occurrence of aspecies just outside the periphery if its primary distributionas defined above (one or two collections compared withabundant collections elsewhere) did not warrant classifyingit into a broader distribution category. Less than 5% of thespecies in this study had such distributions. Species distri-butions were determined from Neotropical floras suchas Flora Neotropica and Flora Mesoamericana, onlinetaxonomic data bases from the Missouri Botanical Garden

(e.g. TROPICOS) and the New York Botanical Garden, andfloristic lists or vegetation studies (see Table 2 for refer-ences).

Additionally, comparisons of species in this study weremade with the compositions of nearby areas of northernMesoamerica and the Caribbean, including the neighbouringstates of Mexico, the Peten of Guatemala, and Cuba,Jamaica, and Puerto Rico. For this study, we separated theYucatan biotic province into two areas: the northern pen-insula (Quintana Roo, Yucatan and Campeche) and thePeten of Guatemala. Comparisons of the forests in thoseareas and the forests of this study were made without sta-tistical analysis due to differences in sampling methodologyand differences in species density of each area. Nevertheless,such coarse comparisons allowed for examination of therelative floristic affinities of the topographic positions in theBNR with other areas of the region. Weaknesses of suchcomparisons included incomplete sampling of the forests ofthe Neotropics and splitting of poorly known taxa thatshould otherwise be lumped as one species of a broaderrange. Therefore, these comparisons may have been impre-cise, but we believe that our conclusions about relativeaffinities were fairly robust.

Three statistical approaches were used to evaluate topo-graphic effects on the phytogeography of species. First,regression analysis was employed to determine if relation-ships existed between the phytogeography of species andelevation above the valley floors, using the three broadlydefined categories of distribution. Secondly, comparisonsamong topographic positions with respect to proportions ofspecies by broad distribution category were performed usingmultivariate analysis of variance (MANOVA). Thirdly, theeffects of geographical and elevational distances on compo-sitional dissimilarities between sample plots (SPs) wereevaluated using the Mantel test (McCune & Mefford, 1999;McCune & Grace, 2002).

Cluster analysis was used to classify SPs into groups basedon the presence or absence, or relative abundance, of speciespresent. The resulting dendrograms provided a visual meansof assessing similarity among SPs, groups of SPs, and whe-ther or not groupings of SPs were consistent with topo-graphy. Agglomerative cluster analysis of SPs (Ludwig &Reynolds, 1988) was employed (Podani, 1998). Two classesof distance measures among SPs were used in the analysis:the complement of Jaccard’s index (J) (Jaccard, 1902) andchord Euclidean distance (CHD). The complement toJaccard’s index (1)J) is an expression of dissimilaritybetween individual SPs based on species presence/absence,and CHD is an expression of dissimilarity between SPs basedon the proportional abundances of species. For the analyses,the abundance of trees was expressed as stem density.

Tree richness and diversity within the SPs were evalu-ated using Fisher’s diversity index a (Fisher et al., 1943)and species–individuals curves. Fisher’s index was em-ployed as a measure of tree species diversity thataccounted for the number of individuals sampled, basedon a log-series distribution of the species abundances.Fisher’s a for each SP was calculated through an iterative



procedure, using a program written by M. Rejmanek. Thisindex varies less than species richness with sample size andhas been increasingly used as an index of diversity intropical forests (see Magurran, 1988; Condit et al., 1998;Leigh, 1999 for discussions of the advantages of thisindex). Species–individuals curves allowed for the com-parison of richness on a per-individual basis at differentsamples of individuals. Species–individuals curves weregenerated by resampling with PAST (Hammer et al.,2001). The curves were cross-checked for consistency withcumulative species–individuals curves.

As an exploratory procedure, statistical comparisons ofthe topographic positions were conducted with respect tonumbers of stems and Fisher’s a. Analysis of variance(ANOVA) with site as a blocking factor was performed onnumbers of stems and diversity indices, and post-hoc com-parisons of means were performed with Bonferroni correc-tions to P-values. All proportions were angular-transformed,and numbers of stems were log-transformed to meet theassumptions of normality and homogeneity. Analyses ofvariance were executed with the SPSS 9.0 statistical software(SPSS, 1999).

RESULTS

Physical structure/size structure

The forests were evergreen on the valleys and lower slopes,semi-evergreen (25–50% deciduous trees) on the upperslopes, and semi-deciduous (50–75% deciduous trees) on theridge (S. Brewer, pers. obs.). The slope forests had inclina-tions of 30–37%, and shallow soils (< 0.5 m), with occa-sional, exposed limestone rocks and boulders. The ridgeshad shallow soils and the most variable inclinations of thetopographic positions, from 3% to 30%. The valley forestshad inclinations of < 5% and deep soils (> 1 m).

Stem density increased significantly with elevation abovethe valleys (R2 ¼ 0.76, P ¼ 0.002, d.f. ¼ 9; quadraticfunction) (Table 1). For example, the average number ofstems ‡ 5 cm on ridges was 70% greater than the number ofstems on the upper slopes. Ridges had significantly morestems than the lower slope and valley positions and signifi-cantly more trees ‡ 10 cm d.b.h. than all other positions(P < 0.05, Table 1). Although not quantified by this study,the density and frequency of lianas were noticeably greaterin the valley forests than in the slope and ridge forests. There

are > 60 species of lianas in the forests on valley floors,while smaller numbers seem to be present on slopes andridges forests (M. Rejmanek, unpubl. data). The proportionsof trees < 10 cm d.b.h. were significantly negatively corre-lated with increase in elevation above the valley floors(R2 ¼ 0.62, P ¼ 0.002, d.f. ¼ 10; linear function) (see alsoFig. 2, Table 1). The proportions of trees 10–20 cm d.b.h.were significantly positively correlated with increase in ele-vation above the valleys (R2 ¼ 0.71, P ¼ 0.001, d.f. ¼ 10;linear function). However, the proportions of stems ‡ 20 cmdiameter (a rough estimate of canopy trees) were not signi-ficantly associated with elevation above the valleys(R2 ¼ 0.10, P ¼ 0.6, d.f. ¼ 10) and were not significantlydifferent among the topographic positions (F2,4 ¼ 0.9,P ¼ 0.8). Differences among the topographic positions weremost pronounced for trees in the smallest two size classes(Fig. 2). The slopes and valleys had similar distributions ofmedium-sized to large trees (‡ 50 cm d.b.h.) (Fig. 2), but< 1% of the ridge trees were ‡ 50 cm d.b.h.

Table 1 Mean (SD) species richness, number

of stems (N)*, and Fisher’s diversity index a*

for each of four topographic positions onlimestone at two minimum sampling diame-

ters, representing all trees (stems ‡ 5 cm) and

excluding understory trees (stems ‡ 10 cm)

Valley floor Lower slope Upper slope Ridge

Species ‡ 5 cm 32.7 (2.1) 40.3 (4.0) 43.3 (6.1) 42.0 (2.6)

Species ‡ 10 cm 22.7 (0.6) 28.7 (3.8) 30.7 (4.5) 33.7 (0.6)N ‡ 5 cm 112.3a (20.3) 110.7a (16.0) 136.3a,b (28.1) 236.0b (58.2)

N ‡ 10 cm 41.3a (6.8) 47.7a,b (9.3) 65.3b (7.6) 134.3c (21.0)

Fisher’s a (stems ‡ 5 cm) 15.6a (1.1) 22.9b (1.4) 22.0b (2.0) 15.1a (1.1)

Fisher’s a (stems ‡ 10 cm) 21.5a,b (4.0) 30.8b (2.0) 22.9a,b (5.2) 14.6a (1.7)

*Means in rows sharing the same superscript letter were not significantly different (P > 0.05,

Bonferroni).

0

10

20

30

40

50

60

70

5 10 20 30 40 50 60 70 80 90 100

DBH Class (cm)

Per

cent

of t

rees

Valley floor

Lower slope

Upper slope

Ridge

Figure 2 Distributions of stem diameters at the four topographicpositions by diameter at breast height (d.b.h.) class (lower limit

shown).



Phytogeography of the tree species

The ridges and valley floors were clearly distinct withrespect to composition and phytogeography, while theslopes were transitional in these features. The highestpercentages of species unique to a topographic positionwere found at the extremes of elevation: in the ridges andvalleys, 61% and 39% of their species were unique tothose positions, respectively, in contrast to 19% and 14%for the upper and lower slopes, respectively (Table 2).Slightly more than half (55.5%) of all species were foundat only one of the four topographic positions (see alsoTable 2). Of these species, 49% were found on ridges,followed by valleys (26%), upper slopes (15%), and lowerslopes (11%). Forty-one per cent of all species were foundin only one of the 12 SPs.

Table 2 and Fig. 3 show how the Neotropical distribu-tions of the sampled species varied with elevation above thevalley floors. The proportions of species having northerndistributions increased significantly with elevation above thevalleys (R2 ¼ 0.94, P < 0.001) (Fig. 3a). No significantrelationship between proportion of species of Mesoamericandistribution and elevation was detected (R2 ¼ 0.026,P ¼ 0.89) (Fig. 3b). The proportions of sample species thathave widespread distributions decreased significantly,

however, with increasing elevation above the valley floors(R2 ¼ 0.78, P ¼ 0.001) (Fig. 3c). Differences among thetopographic positions in proportions of widespread (F3,8 ¼11.1, P < 0.01) and northern species (F3,8 ¼ 54.9,P < 0.01) were statistically significant. Ridges had morenorthern species than all topographic positions (allP £ 0.02), but fewer widespread species than all positionsexcept upper slopes (all P < 0.03).

In general, all of the forests sampled were similar in theirstrong affinities for the Peten of Guatemala, sharing 89% oftheir species with that area. The forests also had strongaffinities for neighbouring Mexican forests, although forestsat greater elevations above the valleys had greater propor-tions of species that were also found on the Yucatan Pen-insula (Table 2). Ridges, for example, had 68% of theirspecies with distributions into the Yucatan Peninsula, com-pared with just 39% for the floors of valleys. Otherwise, noclear relationship between topography and proportion ofspecies shared with the neighbouring Mexican areas wasobserved.

The proportion of species having distributions that reachthe Greater Antilles was significantly, but weakly, positivelycorrelated with increasing elevation above the valleys(R2 ¼ 0.34, P ¼ 0.049; linear function, not shown)(Table 2). However, of the 10 most abundant species on the

Table 2 Summary of the phytogeographical affinities of the identified tree species within each of four topographic positions (n ¼ 3 sample

plots/position), at three scales of distribution. Percentage of species and percentage of stems (in parentheses) are provided. Unique species is the

percentage of species in a position that were censused only in that position. Regional distributions (Greater Antilles and selected northern

Mesoamerican) are not mutually exclusive, and therefore do not add to 100%. Neotropical distributions are mutually exclusive. The �allpositions� category represents all species censused at all topographic positions

Valley Lower slope Upper slope Ridge All positions

Local

Unique species 66 (39.4) 73 (14.3) 75 (19.0) 74 (61.3) 171 (55.5)

RegionalGreater Antilles 21.2 (9.3) 23.3 (11.3) 25.3 (17.2) 33.8 (51.4) 29.8 (28.6)

Cuba* 10.6 13.5 19.2 23.0 20.5

Puerto Rico� 9.1 10.8 14.1 20.3 18.6Jamaica� 26.1 34.8 14.1 17.6 14.3

Mexico

Yucatan§ 39.4 48.6 51.3 67.6 55.9

Tabasco– 43.9 45.9 47.4 41.9 46.6Chiapas** 72.7 67.6 74.4 60.8 71.4

Guatemala

Peten�� 84.8 89.2 84.6 81.1 88.8

NeotropicalNorthern Mesoamerica 19.7 (54.3) 30.1 (44.2) 33.3 (47.4) 50.7 (69.3) 33.9 (56.7)

Mesoamerica 25.8 (15.5) 28.8 (29.6) 32.0 (27.5) 24.7 (14.7) 26.3 (20.6)

Widespread 54.5 (30.2) 41.1 (26.2) 34.7 (25.1) 24.7 (15.9) 39.8 (22.7)

*Borhidi (1996).�Acevedo-Rodrıguez & Axelrod (1999), Kartesz & Meacham (1999).�Kelly et al. (1988).§Including Campeche, Yucatan and Quintana Roo: Sousa-Sanchez & Cabrera-Cano (1983), Tellez-Valdes & Cabrera-Cano (1987), Martınez-Salas et al. (2001).–Cowan (1983).

**Breedlove (1986).��Standley et al. (1946–77), TROPICOS.



ridges, seven species (representing 40% of the stems) arecommonly found in the Greater Antilles, including Acaciascleroxyla, a new species for Belize that is common inHispaniola but appears to be quite rare in mainlandMesoamerica. In fact, half of the stems on ridges (51%)belong to species with distributions reaching the GreaterAntilles, compared with just 9% of stems on the floors of thevalleys. Of the widespread species, 42% are found in theGreater Antilles, but this proportion falls to 22% for nor-thern Mesoamerican species.

Topographic effects on familial and species composition

There was no effect of geographical distance between SPs ontheir composition (Table 3). The effect of differences inabsolute elevation was marginally significant. The effect ofdifferences in relative elevations (above the valley floor ateach location), however, was highly significant (Table 3).The compositional uniqueness of the ridge and valley forestswas revealed by the agglomerative clustering of the SPs(Fig. 4a). Ridges and valleys consistently formed uniquegroups, regardless of the minimum tree diameter used (onlyresults for trees ‡ 5 cm diameter shown). The upper andlower slopes, however, separated by site rather than bytopographic position, when the analysis was based on spe-cies presence/absence (Fig. 4a). When species presence wasweighted by abundance, topographic positions formed dis-crete groupings (Fig. 4b,c); such groupings followed topog-raphy more closely when understory trees (< 10 cm d.b.h.)were excluded (Fig. 4c). Groupings based on species abun-dance (via CHD) were more consistent with those based onspecies presence/absence (via 1)J), when N rather than basalarea was used as a measure of abundance (results for basalarea not shown). Groupings formed by using trees ‡ 5 cm or‡ 10 cm d.b.h. were very similar; however the groupings ofslope SPs using the 5 cm d.b.h. minimum diameter con-formed more closely to site than did groupings based onlarger d.b.h. (results for trees ‡ 10 cm d.b.h. not shown).

A total of 181 species from 48 families were recordedfrom the SPs (1.2 ha total). The most speciose families on theridges and upper slopes were the Rubiaceae, Sapotaceae andFabaceae. The most speciose families on the lower slopesand valleys included the Moraceae, Sapotaceae, Rubiaceaeand Arecaceae (Appendix 2). In abundance (N) of trees‡ 5 cm diameter, the valleys and slopes were dominated bythe Arecaceae, due to the high abundance of Astrocaryummexicanum.

Three species, Oxandra belizensis, Pseudolmedia spuriaand Cryosophila stauracantha were encountered on alltopographic positions; these species were also well-repre-sented among SPs (eight of 12). Astrocaryum mexicanumwas the most abundant (n ¼ 331) and frequent (nine SPs)species in this study, although it was absent from ridges. Theridges commonly shared only three of their 10 most abun-dant species with another position; Pouteria reticulata,Protium copal and Nectandra coriacea were shared with theupper slopes. The upper and lower slopes shared four speciesin their 10 most abundant: Rinorea hummelii, an understorytree, and the canopy trees Oxandra belizensis, Drypetesbrownii and Sebastiania tuerckheimiana. Common but un-ique to valleys were Protium confusum, Zanthoxylumriedelianum and Zanthoxylum ekmanii (see also Appendix 1for more details on species abundance).

During the course of this study, we collected 13 speciesnot listed for Belize in Balick et al. (2000) (see Appendix 1),some of which have disjunct or limited distributions. Oneindividual, collected in sterile condition, vegetatively mat-ched Chiangiodendron mexicanum (Flacourtiaceae), amonotypic genus found in Mexico and recently discovered in

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0 50 100 150 200

Northern speciesP < 0.0001; R2 = 0.93

Mesoamerican speciesP = 0.5; R2 = 0.49

Widespread speciesP < 0.001; R2 = 0.82

Pro

port

ion

of s

peci

es

Elevation gain (m)

(a)

(b)

(c)

Site 1Site 2Site 3

Figure 3 Regressions of proportions of species of three Neotropicaldistributions with elevations above the floors of valleys (statistics but

not proportions of angular-transformed data shown). Distributions

are (a) restricted to northern Mesoamerica, (b) of Mesoamerican

distribution, or (c) widespread in the Neotropics (see text forexplanation of distribution categories).



Costa Rica (T. Wendt, pers. comm.). Acacia scleroxyla(Fabaceae), previously known only from a few collections inHonduras but abundant in Hispaniola (D. Seigler, pers.comm.), was abundant on the ridges of two sites. Ottosc-hulzia pallida (Icacinaceae) and Prunus lundelliana (Rosa-ceae) were common only to limestone ridge tops in the studyarea and have been considered restricted to the Peten andsouthern Mexico. Mortoniella pittieri (Apocynaceae), listedin Balick et al. (2000), was common in the valley forest ofsite 1 (Brewer & Webb, 2002) but was known prior to 1997only from small adjacent areas of Nicaragua and Costa Rica.

When evaluating only palms in the SPs, the ridges werecharacterized by a low number of species (three) and by thepresence and high abundance of the clonal palm Chamae-dorea schippii. The slopes were characterized by the pres-ence of Chamaedorea ernesti-augustii (observed asuncommon but not sampled in the valleys) and by a relat-ively high abundance of Cryosophila stauracantha, andSabal mauritiiformis (observed but not sampled in thevalleys). The valley forests typically had relatively highabundance of Attalea cohune, Bactris mexicana, Chamae-dorea pinnatifrons, Chamaedorea tepejilote, and Geonomainterrupta, the first two species being more abundant closerto major streams. Astrocaryum mexicanum was the mostubiquitous and abundant palm over all topographic posi-tions and sites excluding the ridges, where it was absent.Other ubiquitous species were Chamaedorea pinnatifrons,Cryosophila stauracantha, Bactris mexicana, and Desmon-cus orthacanthos. Site 3 in the upper watershed was unusualin its very high abundance of Calyptrogyne ghiesbreghtiana,which formed continuous cover < 1 m high in the valleyforests and was abundant on the slopes. Site 3 was alsounique because of the valley species Synechanthus fibrosus, aspecies not observed in the valleys of the other two sites.

Species richness and diversity

Species richness of trees increased significantly withincreasing elevation above the valley until the ridge position,where richness declined slightly (Table 1; trees ‡ 5 and

‡ 10 cm, respectively: R2 ¼ 0.63, P ¼ 0.01 and R2 ¼ 0.72,P ¼ 0.003; quadratic functions). Using different minimumsampling diameters changed the order of richness among thetopographic positions, however, with mean richness beingslightly higher for upper slopes than ridges for trees ‡ 5 cmd.b.h. and lower than ridges for trees ‡ 10 cm d.b.h.(Table 1). Slopes were significantly more diverse than theridges and valleys, respectively. The lower slopes were themost diverse position, with the valleys and ridges beingsignificantly lower in diversity (all P < 0.05). Thus, Fisher’sindex could be explained by a quadratic function of diversitywith elevation above the valleys (R2 ¼ 0.86, P < 0.001 fortrees ‡ 5 cm d.b.h.), regardless of minimum diameter sam-pled. Species–individual curves showed that slopes havegreater richness at all samples of individuals and havegreater rates of accumulation of species with individualssampled (Fig. 5). Ridges had greater initial rates of accu-mulation of species with individuals sampled than valleys;however, valleys surpassed ridges in richness in samples of60 or more individuals.

DISCUSSION

Physical structure/size structure

Topography affects the physical structure of the forests overlimestone in the BNR, despite small changes in elevationbetween topographic positions (< 250 m at the most). Withincreasing elevation above the valleys, trees 10–20 cm d.b.h.appear to take up the space that would otherwise be occu-pied by large trees on ridges, and by smaller, understory treeson slopes and ridges, probably due to the low number ofindividuals of Astrocaryum mexicanum at these positions.The stature of the forests becomes shorter from the valleys tothe ridges, with fewer numbers of large trees, most likelybecause of increased edaphic drought enhanced by greaterdrainage and thinner soils at higher elevations (Furley &Newey, 1979), less access to groundwater, and greaterexposure to desiccating winds in the dry season. The ridgesmay be more exposed to hurricanes, further reducing the

Table 3 Mantel correlations (r) of veget-

ation dissimilarity matrices with matrices ofgeographical distances and elevational dif-

ferences (in metres). Only densities of stems

‡ 5 cm are used. Results of asymptoticapproximation procedures and randomiza-

tion tests are shown. Bonferroni levels of

significance were set at a ¼ 0.05/3 ¼ 0.017*,

0.01/3 ¼ 0.0033** and 0.001/3 ¼ 0.00033***

Matrices r Asymptotic approximation Randomization tests

Jaccard dissimilaritiesGeographical distances )0.08 n.s. n.s.

Abs. elev. differences� 0.31 n.s. *

Rel. elev. differences� 0.77 *** ***

Chord Euclidean distances

Geographical distances )0.09 n.s. n.s.

Abs. elev. differences� 0.27 n.s. n.s.Rel. elev. differences� 0.64 *** **

Euclidean distances

Geographical distances )0.12 n.s. n.s.Abs. elev. differences 0.24 n.s. n.s.

Rel. elev. differences� 0.63 *** *

�Absolute elevation change.�Elevation changes (from the valley floor) at each location.



possibility of development of a tall forest (Bellingham, 1991;Brokaw & Grear, 1991; Everham & Brokaw, 1996), but ourobservations after Hurricane Iris in 2001 are more consistentwith other studies that show greater resistance of ridge forestto hurricane damage (Scatena & Lugo, 1995).

Phytogeography of the tree species

Apparently driven by an interaction between topography andlimestone geology, large-scale phytogeographical patternsare manifested at very local scales in the Bladen watershed.The limestone forests on the valleys and ridges are composed

of tree species that have more restricted local distributionsthan those in the slope forests (Table 2). The relatively highlocal fidelity of the valley and ridge species reflects the uniquespecies compositions of these positions compared with theslopes, which are transitional in their compositions. Speciesfrom northern Mesoamerica dominate the ridges, and Neo-tropically widespread species dominate the valleys, whetheror not the measure is in stems or numbers of species repre-sented (Table 2). Such phenomena are known in Europeanliterature as demonstrations of �the Alechin’s law of preced-ence� (pravilo predvareniia; Alekhin, 1950) or �the Walter’slaw of the relative constancy of habitat� (das Ges-etzmassigkeit der relativen Standortkonstanz; Walter, 1979).

1-J

R1 R2 R3 V1L2U1 U3 L3U2L1 V2 V3

0

0.9

(a)

R1 R2 R3 V1L2U1 U3 L3 U2L1V2 V3

0

1.0

CH

D

(b)

1.0

0

CH

D

R1 R2 R3 V1L2U1 U3 L3U2 L1 V2 V3

(c)

Figure 4 Agglomerative clustering of the sample plots (SPs) at four

topographical positions (R, ridge; L, lower slope; U, upper slope; V,

valley floor) within three sites (indicated by subscripts). The com-

plement to Jaccard’s index (1)J) is an expression of dissimilaritybetween individual SPs based on species presence/absence. Chord

Euclidean distance (CHD) is an expression of distance between SPs

based on the proportional abundances of species. Dendrograms arebased on (a) trees ‡ 5 cm d.b.h., (b) trees ‡ 5 cm d.b.h. and (c) trees

‡ 10 cm d.b.h.

Slopes

Ridge

Valley floor

Valley floor

RidgeSlopes

Spec

ies

N

Slopes

Valley floor

Ridge

(a)

(b)

(c)

0 50 100 150 200

10

20

30

40

50

10

20

30

40

50

10

20

30

40

50

Figure 5 Species–individuals curves for four topographicpositions (upper and lower slopes not differentiated with labels)

within three sites (a, b, c correspond to sites 1, 2 and 3, respectively).



The widespread Neotropical distributions of the treespecies of the valleys may be due to a relatively mesic envi-ronment that is more conducive to colonization by vagile,generalist taxa that are better adapted to mesic conditions inthe lowlands of South America. A large proportion of thelowland tree taxa in Amazonia are generalists with widegeographical ranges (Pitman et al., 1999), and Gentry(1982) pointed out the preponderance of unusually wide-ranging taxa of South American origin in the lowland forestsof Mesoamerica. The alluvial soils of the BNR are deeperand more prone to disturbance in the form of flooding,erosion and deposition than the well-drained slopes; there-fore they are conducive to colonization by vagile taxa.Limestone, however, produces unique, well-drained soilsand microtopography (Furley & Newey, 1979; Richards,1996). Furthermore, karst landforms are common in nor-thern Mesoamerica but are rare in southern Mesoamericaand South America (Sweeting, 1972; Snead, 1980). Localtree species, adapted to the drier edaphic and microclimaticconditions on limestone outcrops, should therefore beexpected to have better recruitment and be better competi-tors in those environments than colonists from SouthAmerica. Thus, compared with the other topographic posi-tions, the ridges have a tree flora that is the most restricted indistribution when examined at small and large scales(Tables 1 and 2).

The ridges share a considerable proportion of their specieswith the Greater Antilles (34%), although this element is notas strong as the northern Mesoamerican element. Moreover,the floristic representation of the Greater Antilles in numbersof stems is much greater than would be expected from spe-cies alone (Table 2). Such an affinity might be expected giventhe dominance of outcrop limestone in the Greater Antillesand the associated drought-prone soils. The floristic com-parisons of this study are made on a coarse level, however,and neighbouring forests of Mexico grow on both limestoneand igneous substrata. Therefore, future studies of exposedlimestone forests in the neighbouring parts of Mesoamericamay reveal similar floristic links to the Greater Antilles.Floristic links among limestone areas in this region may bedriven more by water availability and substrate, via levels ofedaphic drought, than by proximity (Estrada-Loera, 1991;Trejo-Torres & Ackerman, 2002).

Species richness and diversity

The high species richness of ridges can be explained simplyby the fact that we sampled more stems at this position. Highstem densities on ridges are associated with a low proportionof very small (< 10 cm d.b.h.) and large trees (> 50 cmd.b.h.). Higher species diversity on the slopes (as Fisher’s a,Table 1) than valleys and ridges, however, is likely the resultof the generation and/or maintenance of greater recruitmenton slopes. A �mass effect� (Shmida & Wilson, 1985) fromnearby sources of species may be maintaining populations ofspecies that might otherwise go locally extinct due to lowand unstable population sizes. In addition, an intermediatephysical position between two unique floras would cause the

slopes to receive a higher diversity of seed inputs than thevalleys and ridges; the greater overlap observed in thecompositions of slopes with neighbouring positions maysupport this hypothesis.

Upon arrival, these propagules and resulting seedlings mayhave a greater probability of survival on slopes. The forestsof valley floors appear to experience more intense seed pre-dation by terrestrial mammals, especially small rodents(Brewer & Rejmanek, 1999), than occurs on the slopes(S. Brewer & M. Rejmanek, unpubl. data). Halle et al.(1978) suggest that the discontinuous nature of the canopyon slopes, and the angled incidence of light, results in morelight penetration through the canopy therefore promotingthe survival of smaller, shade intolerant tree species. Smallsample sizes in this study preclude a rigorous test of Halleet al.�s (1978) hypothesis. On Barro Colorado Island,Panama, greater soil moisture on the slopes than the adja-cent forests is believed to be a cause of higher tree diversityin those forests (Leigh, 1996). The soils on upper limestoneslopes in Belize, however, produce stronger edaphic droughtcompared with valley soils (Wright et al., 1959; Furley &Newey, 1979). The slopes occupy a broader moisture gra-dient and may have more microtopographic variation thanthe valleys and ridges, thus providing a greater variety ofmicrohabitats for species with more restricted requirementsfor recruitment and/or more limited competitive ability.

Finally, greater age of forests on slopes, like some sites inBolivia (Smith & Killeen, 1998), allows for greater netimmigration of species over time. Valley forests were clearedand cultivated until c. 1000 yr BP (Abramiuk, 1999), a shorttime for long-lived trees (Chambers et al., 1998), whereasthe nearby slopes would be too steep and their soils tooshallow for agriculture. Furthermore, the valley floor soilsare likely subject to more frequent and stronger disturbancevia changes in nearby watercourses and periodic, massivefloods. Hurricanes may also have a greater impact on valleysthan slopes, due to the shallow rooting of trees in valleys(Scatena & Lugo, 1995).

Conservation implications

Although limestone valley forests on alluvium in the BNRhave neither unique floristics nor diversity when examined atthe Neotropical scale – indeed, their composition is domin-ated by widespread Neotropical species – intact forests ofthis kind are rare in the region because of their valuable soilsfor agriculture and easy access for timber and wildlifeextraction. On the other topographic extreme, ridge forestshave the lowest diversity index, but they contain the mostunusual floristic assemblage and have significant affinities forlimestone forests in the Caribbean. Ridges also occupy asmall proportion of the land area in the region and may serveas important sources of propagules for the recolonization ofsimilar, restricted forests that have been disturbed by fire orhurricanes. Future vegetation studies should examine thephytogeography as well as diversity of the forests in theregion, and should attempt to identify those variables, suchas finer-scale topography and substrate type, that may be



useful in the identification of forest types that require pro-tection. One of the potential consequences of these findingsfor the conservation of biodiversity in northern Mesoamer-ica is that phytogeographical considerations in weighting theuniqueness of floristic composition – in addition to measuresof diversity – must be considered in the delineation, priori-tization, and management of potential protected areas.Thus, biodiversity surveys in this region may benefit fromsurrogate variables, such as topography, for phytogeo-graphical elements of vegetation.

Although Belize is one of the least populated countries inthe Neotropics, the recent construction of a paved highwaythrough southern Belize will certainly lead to growth inhuman populations that will extract many kinds of resourcesfrom the forests of the Maya Mountains. Limestone areasare particularly valuable sources of minerals and rich agri-cultural land, and for this reason have become increasinglyvulnerable to human activity (e.g. Day, 1993). Future deci-sions about the delimitation and management of protectedareas in this region will require a better understanding of thepatterns and composition of the biodiversity of limestoneforests.

ACKNOWLEDGMENTS

We thank the Conservation Unit of the Forest Depart-ment, Ministry of Natural Resources, Belmopan, Belize forpermission to conduct research in the Bladen NatureReserve. J.L. Zarucchi (MO), F. Barrie (MO, F),G. Davidse (MO), R. Leisner (MO), J. Ricketson (MO),G.E. Schatz (MO), D.S. Seigler and J.E. Ebinger (ILL),C.M. Taylor (MO), H. van der Werff (MO), and G.L.Webster (DAV) kindly provided help with determinationsof some herbarium specimens collected during this study.Determinations of a number of other herbarium specimenswere made possible with guidance from William Burgerand Robin Foster and with visiting scholar funds toS. Brewer from the Field Museum of Natural History(Chicago, IL, USA). Jean Shepard, Ellen Dean and TomStarbuck of the UC Davis Herbaria were especially helpfulwith specimen processing. Previous versions of thismanuscript were greatly improved by comments from TomWendt, Keith Rennolls and two anonymous reviewers.Field work was supported by grants from the UC DavisCenter for Biosystematics and the Davis Herbaria Societyto S. Brewer. Accommodations and logistical support wereprovided by the Belize Foundation for Research andEnvironmental Education (BFREE).

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BIOSKETCHES

Steven W. Brewer is interested in testing hypothesesabout landscape patterns of tree diversity and phyto-geography, examining the dynamics of seed predationand dispersal in plant recruitment, and the conservationof plant communities.

Marcel Rejmanek conducts research on predicting andquantifying the risk of invasions by plants, plantcommunity classification and dynamics, and the ecologyof seed dispersal and regeneration of tropical forests.

Molly A. H. Webb is an Assistant Professor of research atOregon State University, where she studies the repro-ductive physiology and endocrinology of sturgeon.

Paul V. A. Fine is finishing his dissertation on habitatspecialization of Amazonian trees. He is especiallyinterested in the effects herbivores may have on the originand maintenance of patterns of high beta-diversity acrossdifferent soil types.



Ap

pen

dix

1A

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BA

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A2

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10

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10

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10

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nia

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rophyl

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ing

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2

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0

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chil

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60

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ilia

mosc

hat

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71

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59

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10

00

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Tri

chil

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lida

Sw

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0

Men

isper

mace

ae

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na

mex

ican

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iers

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00

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19

20

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ceae

Bro

sim

um

alic

astr

um

Sw

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30

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20

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tilla

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tica

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1



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us

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insi

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0

Pouls

enia

arm

ata

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59

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18

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66

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10

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51

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phis

mex

ican

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ure

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yri

stic

ace

ae

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pso

neu

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ola

kosc

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1

Myrt

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16

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69

12

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83

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nia

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38

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25

8

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2O

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cace

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S.F

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81

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30.0

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40.0

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20

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amen

sis

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arn

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1

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Poly

gonace

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mex

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nce

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10

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10

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0



Ap

pen

dix

1co

nti

nued

Taxon

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ope

Upper

slope

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ge

BA

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1B

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BA

3N

3B

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BA

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BA

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BA

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chotr

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10

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50

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20

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m.)

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nce

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10

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0

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bel

izen

sis

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ndl.

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99

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um

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tn.

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40

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p.junip

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16

10.0

25

20

00

00

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dac

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ophyl

us

cam

pto

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1

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1

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izen

sis

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ndl.

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20

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10

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2

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10

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n.

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10

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icle

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tier

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30

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20

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40

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kar

ast

amin

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laG

illy

00

00

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00

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30

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5

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pota

(L.)

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00

00

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10

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0

Poute

ria

amyg

dal

ina

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ndl.

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ni

00

00

00

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20

00

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47

30.0

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30

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2

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cam

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na

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00

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10

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30

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ni)

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10

00

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10

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25

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10

00

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0

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sis

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ni

00

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42

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10

00

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10

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0

Poute

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ta(E

ngl.

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00

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20.0

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19

Sider

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izen

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n.

00

00

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00

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10

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40

20.1

30

50

0

Ste

rculiace

ae

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um

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am

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00

00

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26

10

00

00

00

00

00

00

0

Theo

phra

stace

ae

Deh

erai

nia

smar

agdin

a(P

lanch

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den

)D

ecne.

00

00

00

00

00

00

00

00

0.0

03

10

00

00

0

Jacq

uin

ialo

ngi

foli

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ndl.

00

00

00

00

00

00

00

00

00

00

0.0

28

10

0T

ilia

ceae

Hel

ioca

rpus

amer

ican

us

L.

00

00

00

00

00

00

00

00

0.0

45

10

00.0

11

20

0

Mort

onio

den

dro

nve

stit

um

Lundel

l*0

00

00

00

00

00

00

00.0

16

10

00

00

00

0



Tri

chosp

erm

um

grew

iifo

lium

(A.

Ric

h.)

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erm

.

0.1

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10

00

00.1

16

10

00

00

00

00

00

00

00

0

Ulm

acea

e

Am

pel

oce

rahott

lei

(Sta

ndl.)

Sta

ndl.

0.0

04

10.0

48

10

00.0

04

10

00.1

03

20.3

39

50.0

95

10

00

00

00

0U

rtic

ace

ae

Ver

ben

ace

ae

Vit

exga

um

eri

Gre

enm

.0

00

00

00

00

01.3

27

10

00

00

00

00

00

0

Vio

lace

ae

Rin

ore

ahum

mel

iiSpra

gue

00

0.0

03

10.0

05

10.0

11

30.0

32

80.0

69

15

00

0.0

08

30.0

66

15

00

00

00

Indet

.

Indet

.1

00

00

00

0.0

45

10

00

00

00

00

00

00

00

0In

det

.2

00

00

00

00

0.1

37

10

00

00

00

00

00

00

0

Indet

.3

00

00

00

00

00

00

00

00

00

00

0.1

29

10

0

Indet

.4

00

00

00

00

00

00

00

00

00

00

00

0.1

16

1

Indet

.5

00

00

00

00

00

00

00

00

00

00

00

0.0

23

1

BA

,basa

lare

a(m

2);

N,

num

ber

of

stem

s.*N

ot

pre

vio

usl

ypubli

shed

(in

Bali

cket

al.,

2000)

for

Bel

ize.



Ap

pen

dix

2T

he

top

25

fam

ilie

son

the

topogra

phic

posi

tions

as

ranked

by

num

ber

of

spec

ies

Vall

eyL

ow

ersl

ope

Upper

slope

Rid

ge

Fam

ily

SN

Fam

ily

SN

Fam

ily

SN

Fam

ily

SN

Mora

ceae

933

Rubia

ceae

725

Rubia

ceae

926

Fabace

ae9

31

Rubia

ceae

614

Sapota

ceae

711

Sapin

dac

eae

847

Rubia

ceae

846

Fabace

ae6

12

Mora

ceae

624

Fabace

ae8

15

Sapota

ceae

568

Sapota

ceae

416

Are

cace

ae

490

Mel

iace

ae7

10

Euphorb

iace

ae

432

Laura

ceae

47

Mel

iace

ae4

14

Are

cace

ae

3111

Sapin

dace

ae

414

Are

cace

ae

3166

Fabace

ae

48

Mora

ceae

337

Anaca

rdia

ceae

330

Mel

iace

ae

315

Annonace

ae

314

Annonace

ae

319

Mora

ceae

36

Apocy

nace

ae

37

Fla

court

iace

ae

34

Laura

ceae

37

Anaca

rdia

ceae

34

Ruta

ceae

28

Laura

ceae

34

Euphorb

iace

ae

227

Myrt

ace

ae

289

Myri

stic

ace

ae

26

Bom

bac

ace

ae

221

Ola

cace

ae

216

Poly

gonace

ae2

83

Euphorb

iace

ae

25

Euphorb

iace

ae

221

Bom

bac

ace

ae

28

Burs

erace

ae

249

Mel

ast

om

ata

ceae

24

Apocy

nace

ae

25

Cel

ast

race

ae

25

Fla

court

iace

ae

238

Annonace

ae

23

Clu

siace

ae

25

Fla

court

iace

ae

25

Laura

ceae

219

Bom

baca

ceae

22

Anaca

rdia

ceae

23

Sapin

dac

eae

24

Cel

ast

race

ae

218

Burs

erace

ae

120

Com

bre

tace

ae

23

Malp

ighia

ceae

22

Clu

siac

eae

212

Anaca

rdia

ceae

16

Malp

ighia

ceae

22

Til

iace

ae

22

Mel

iace

ae

29

Com

bre

tace

ae

14

Mel

ast

om

ata

ceae

22

Vio

lace

ae

118

Malp

ighia

ceae

27

Cel

tidace

ae

13

Vio

lace

ae1

26

Apocy

nace

ae

19

Nyct

agin

ace

ae

27

Clu

siac

eae

12

Ola

cace

ae

121

Burs

erace

ae

16

Apocy

nace

ae

22

Fla

court

iace

ae

12

Ara

liace

ae1

5U

lmac

eae

16

Icaci

nace

ae

169

Ola

cace

ae

12

Burs

erace

ae

14

Clu

siac

eae

15

Rham

nace

ae1

15

Ulm

acea

e1

2O

leace

ae

14

Ara

liace

ae

14

Rosa

ceae

111

Vio

lace

ae

12

Ulm

ace

ae1

3C

om

bre

tace

ae

13

Eben

ace

ae

18

Cappari

dace

ae

11

Act

inid

iace

ae

12

Nyct

agin

ace

ae1

3A

reca

ceae

17

Cari

cace

ae

11

Cel

ast

race

ae

11

Eben

ace

ae

12

Bom

baca

ceae

17

Tota

l66

348

75

332

78

408

77

704

S,num

ber

of

spec

ies;

N,

num

ber

of

stem

s‡

5cm

d.b

.h.



Documents

Relationships of phytogeography and diversity of tropical tree