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Background/Question/Methods The positive effect of nurse-plants on beneficiary species can act as a selection process affecting competitive ability of these recipient species. The purpose of this study was to determine if there is evidence for changes in competitive ability of species that associate with nurse-plants but maintain a presence in open sites in arid ecosystems. Seeds from species found growing under shrubs and in the open in a South American Desert ecosystem were collected and grown in sets of growth chambers programmed to emulate the microenvironmental conditions of each. Each source was reciprocally planted and simple density series were used to contrast performance in germination and early seedling establishment lifestages to infer changes in competitive ability. Results/Conclusions This design is an excellent extension to the reciprocal common garden design now used to study invasive plant species from different regions and the analog of differentiation within species but at much smaller scales is an important topic to consider for the study of plant faciitation and positive interactions more generally. Importantly, density-dependent interactions between beneficiary species is an important concept in modeling community dynamics and changes in apparent competition could be an important factor that mediates the capacity for shrubs to buffer the loss of smaller plant species within arid systems. Dataset: http://bit.ly/rct-compdata
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#TheSunTheMoonTheTruth
#TheShrubTheOpenTheTruth
@cjlortie
three things that cannot be hidden
the shrub or dominants
the open or non-canopy sites
the truth
extreme variation is an important opportunity
not at all deserts at the same of course
but many have significant selection processes & gradients
the methodology of shrub-open contrasts is a convenient experimental design tool but not necessarily the whole story
Pescador et al. 2014
Pescador et al. 2014
bivariate nearest-neighbor distance distributions
dart hits
Pescador et al. 2014
facilitation in the halo
dominants do have major relative influences in these systems
Filazzola & Lortie 2014
reasonable to assume that not only can there be different species associated with dominants but that
individuals within species can exhibit ecotypic differentiation
A test for ecotypic differentiation in the competitive ability of beneficiary species found under nurse-plants and in open sites in arid
systems
lortie, filazzola, lamarque, sotomayor
@cjlortie
teamwork & collaboration
http://bit.ly/ecotype
if you have a two-phase plant system, here is our approach to exploring the following:
(we want you to join the pack)
local adaptation phenotypic plasticity
ecotypic differentiation
pilot studies
step 1. seeds
Collect seeds from 5 different species of plants that are found both under shrubs in arid systems and in the open nearby. !A total of 2000 seeds per species is recommended as a minimum.
step 1I. patterns
Measure microenvironmental conditions & record plant densities for each species. !Use micro-loggers (we used pro v2s) & record at least a season of conditions under your shrub species and nearby in the open (non-canopied sites where your target species also occur).
step III. reciprocal condition trials (rcts)
petri dish or pot trials in growth chambers (reciprocal design)
modded the reciprocal common garden protocol
shrubopen
shrubopen
seedchambers
rcts on seeds to explore seed biology & germination
first set of pilot experiments: both SA & CA
a single density each species
a
b
c
d
e
a
b
c
d
e
under each setof conditions
SA species
Sotomayor et al. 2014
methodology generated differences
rcts on seeds
but what about the potential for different competitive abilities
Hypothesis. The microsite generated by dominants in two-phase communities leads to different competitive trait sets for the associated species because of different indirect interaction networks & reduced variation in microenvironmental conditions.
Predictions. (i) ndd (negative density dependence):Individuals from understory microsites respond more strongly & negatively to increasing seed densities.
!(ii) ce (competitive effect vs response):Individuals from understory microsites exert significantcompetitive effects on individuals from the open.
(iii) pp phenotypic plasticity: Individuals from open microsites respond more strongly to reciprocal conditions than shrub individuals.
cage matching: intraspecific seed density series
Lortie et al. 2009
understory open
#TheShrubTheOpenTheTruth
same initial protocol as first set of pilot experiments
density series each species
a
b
c
d
e
a
b
c
d
e
under each setof conditions
monoculture mixed
ndd
ce
pp
implications
density-dependent interactions between beneficiary species is an important concept in modeling community dynamics
rct is an effective protocol
implications
changes in apparent competition & facilitation are important factors that mediate the capacity for shrubs to buffer the loss of smaller plant
species within arid systems
impacts in arid ecosystems are not always pretty
experimentation at finer scales & collaboration globally needed
bonus slides: species identity is important
ndd
ce
pp
