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The Genus Isoetes (Lycophyta) in theSoutheastern United States
Lytton John Musselman, Rebecca D BrayW Carl Taylor
10 April 2007
The Genus Isoetes (Lycophyta) in theSoutheastern United States
A quarter century review for field botanists
What is a quillwort?Field characters
Obligate hydrophyte with spirally arranged leaves with a groove on the adaxial
surface, four air chambers; arising from a “corm-like” structure bearing forked root
tips
Obligate hydrophyte with spirally arranged leaves
groove on adaxialsurface, four air chambers
groove on adaxialsurface, four air chambers
groove on adaxialsurface, four air chambers
diaphragm
arising froma “corm-like” structure bearing forked
root tips
All quillworts look similar!Size can range from 0.01 to 2.0 m
Isoetes butleri Isoetes melanopoda Isoetes mattaponica
All quillworts look similar!
Isoetes butleriKentucky
Isoetes stellebossiensisSouth Africa
Isoetes olympicaSyria
All quillworts look similar!Lots of variability in size in most species
Isoeteshyemalis
TerrestrialSubmersed
The exception to the spiraled leaves,corm structure, and forked roots isIsoetes tegetiformans
Then and Now
1985--Three species of quillworts inFlora of the Carolinas
2007--Six in Weakley
Then and Now
1985--No hybrids
2007--Isoetes are
Then and Now
1985--No hybrids
2007--Isoetes are Promiscuousall can be expected to hybridize
Then and Now
1985--few species with scales
2007-- all Isoetes have scales
Then and Now
1985--few species with scales
2007-- all Isoetes have scales
Scales and Phyllopodia are DifferentScales are modified leaves, phyllopodia
are indurated leaf bases
Then and Now
1985--considered infrequent or rare
2007-- most counties in the Southeastprobably have/had Isoetes
Then and Now
1985--little vegetative reproduction
2007-- probably widespread
Then and Now1985--little vegetative reproduction
2007-- probably widespread throughbranching of the root stock
Isoetes flaccida, Putnam Co, FL
Unnamed tetraploid, Chesterfield Co, VA
Then and Now
1985--Megaspores essential for determination
2007-- Megaspores still necessary fordiploid species
Megaspores confusing for most tetraploids because of similar
ornamentation
Isoetes georgiana
Isoetes hyemalis
The Genus as Currently UnderstoodTaxonomically in the Southeast
I. Nine Basic Diploids (2n=22)Isoetes butleri I. engelmannii I. flaccida I. mattaponica I. melanopoda I. melanospora I. “piedmontana’I. tegetiformans I. valida
The Genus as Currently Understood
I. Basic Diploids (2n=22)
Conservation concern
I. mattaponica
I. melanospora
I. tegetiformans
Isoetes acadiensisI. appalachianaI. hyemalis I. louisianensisI. piedmontanaI. ripariaI. virginica
The Genus as Currently Understood
II. Seven Described Allotetraploids (2n=44)
II. Allotetraploids (2n=44)
Conservation concerns
Cannot be accurately addresseduntil we know more about the phylogeny of these polyploids, at least some of which are polyphyletic
The Genus as Currently Understood
III. Three Described Allohexaploids (2n=66)
Isoetes georgiana (includes I. boomii) I. junciformisI. microvela
The Genus as Currently Understood
IV. Allohexaploids (2n=66)
Conservation concerns
Cannot be accurately addresseduntil we know more about the phylogeny of these polyploids, at least some of which might be polyphyletic
The Genus as Currently Understood
IV. One Allooctoploid (2n=88)
Isoetes tennesseensis
of conservation concern
The Genus as Currently Understood
V. One Allodecaploid (2n=110)
Isoetes lacustris
Of conservation concern in the South, abundant across Canada
The Genus as Currently Understood
VI. Four named primary hybrids Isoetes × altonharvillii (I. valida x I. engelmannii, 2n=22) I. × brittonii (I. engelmannii x I. riparia, 2n=33)
I. × bruntonii (I. engelmannii x I. hyemalis,2n=33)
I. × carltaylorii (I. engelmannii x I. acadiensis,2n=33)
The Genus as Currently Understood
Hybrids spores are misshapen andof varying sizes
Hybrids exhibit heterosis
Isoetes valida Isoetes engelmannii
Isoetes × altonharvillii
VI. New Taxa
There are several diploid populations that deserve further study, these could be new
species.
We have several distinct tetraploid populationsbut cannot formally name them until we
understand their phylogeny.
The Genus as Currently Understood
How are Isoetes species identified?
Answer: With difficulty!
Megaspores have traditionally been themost reliable way to identify quillworts
Until the advent of molecular techniques,megaspores were used to suggest
patterns of phylogeny
How many species have been extirpated in the past twenty five years?
Isoetes “riparia”,Alligator River,North Carolina
Acknowledgements
Khalid Al AridMohammad Al ZeinJim AllisonJay BolinDaniel BruntonCindy CaplenKerry HeafnerJim HickeyDavid KnepperODU Plant Research GroupCharlie WerthJoe Winstead