The Genus Isoetes (Lycophyta) in the Southeastern United States
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The Genus Isoetes (Lycophyta) in theSoutheastern United States
Lytton John Musselman, Rebecca D BrayW Carl Taylor
10 April 2007
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The Genus Isoetes (Lycophyta) in theSoutheastern United States
A quarter century review for field botanists
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What is a quillwort?Field characters
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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
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Obligate hydrophyte with spirally arranged leaves
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groove on adaxialsurface, four air chambers
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groove on adaxialsurface, four air chambers
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groove on adaxialsurface, four air chambers
diaphragm
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arising froma “corm-like” structure bearing forked
root tips
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All quillworts look similar!Size can range from 0.01 to 2.0 m
Isoetes butleri Isoetes melanopoda Isoetes mattaponica
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All quillworts look similar!
Isoetes butleriKentucky
Isoetes stellebossiensisSouth Africa
Isoetes olympicaSyria
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All quillworts look similar!Lots of variability in size in most species
Isoeteshyemalis
TerrestrialSubmersed
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The exception to the spiraled leaves,corm structure, and forked roots isIsoetes tegetiformans
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Then and Now
1985--Three species of quillworts inFlora of the Carolinas
2007--Six in Weakley
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Then and Now
1985--No hybrids
2007--Isoetes are
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Then and Now
1985--No hybrids
2007--Isoetes are Promiscuousall can be expected to hybridize
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Then and Now
1985--few species with scales
2007-- all Isoetes have scales
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Then and Now
1985--few species with scales
2007-- all Isoetes have scales
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Scales and Phyllopodia are DifferentScales are modified leaves, phyllopodia
are indurated leaf bases
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Then and Now
1985--considered infrequent or rare
2007-- most counties in the Southeastprobably have/had Isoetes
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Then and Now
1985--little vegetative reproduction
2007-- probably widespread
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Then and Now1985--little vegetative reproduction
2007-- probably widespread throughbranching of the root stock
Isoetes flaccida, Putnam Co, FL
Unnamed tetraploid, Chesterfield Co, VA
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Then and Now
1985--Megaspores essential for determination
2007-- Megaspores still necessary fordiploid species
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Megaspores confusing for most tetraploids because of similar
ornamentation
Isoetes georgiana
Isoetes hyemalis
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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
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The Genus as Currently Understood
I. Basic Diploids (2n=22)
Conservation concern
I. mattaponica
I. melanospora
I. tegetiformans
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Isoetes acadiensisI. appalachianaI. hyemalis I. louisianensisI. piedmontanaI. ripariaI. virginica
The Genus as Currently Understood
II. Seven Described Allotetraploids (2n=44)
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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
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III. Three Described Allohexaploids (2n=66)
Isoetes georgiana (includes I. boomii) I. junciformisI. microvela
The Genus as Currently Understood
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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
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IV. One Allooctoploid (2n=88)
Isoetes tennesseensis
of conservation concern
The Genus as Currently Understood
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V. One Allodecaploid (2n=110)
Isoetes lacustris
Of conservation concern in the South, abundant across Canada
The Genus as Currently Understood
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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
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Hybrids spores are misshapen andof varying sizes
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Hybrids exhibit heterosis
Isoetes valida Isoetes engelmannii
Isoetes × altonharvillii
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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
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How are Isoetes species identified?
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Answer: With difficulty!
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Megaspores have traditionally been themost reliable way to identify quillworts
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Until the advent of molecular techniques,megaspores were used to suggest
patterns of phylogeny
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How many species have been extirpated in the past twenty five years?
Isoetes “riparia”,Alligator River,North Carolina
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Acknowledgements
Khalid Al AridMohammad Al ZeinJim AllisonJay BolinDaniel BruntonCindy CaplenKerry HeafnerJim HickeyDavid KnepperODU Plant Research GroupCharlie WerthJoe Winstead