The Genus Isoetes (Lycophyta) in the

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The Genus Isoetes (Lycophyta) in the Southeastern
United States
Lytton John Musselman, Rebecca D Bray W Carl
Taylor
10 April 2007
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The Genus Isoetes (Lycophyta) in the Southeastern
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 adaxial surface, four air chambers
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groove on adaxial surface, four air chambers
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diaphragm
groove on adaxial surface, four air chambers
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arising from a 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 butleri Kentucky
Isoetes stellebossiensis South Africa
Isoetes olympica Syria
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All quillworts look similar! Lots of variability
in size in most species
Isoetes hyemalis
Terrestrial
Submersed
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The exception to the spiraled leaves, corm
structure, and forked roots is Isoetes
tegetiformans
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Then and Now 1985--Three species of quillworts
in Flora 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
Promiscuous all 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 Different Scales 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
Southeast probably have/had Isoetes
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Then and Now 1985--little vegetative
reproduction 2007-- probably widespread
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Then and Now 1985--little vegetative
reproduction 2007-- probably widespread
through branching 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
for diploid species
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Megaspores confusing for most tetraploids
because of similar ornamentation
Isoetes hyemalis
Isoetes georgiana
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The Genus as Currently Understood Taxonomically
in the Southeast I. Nine Basic Diploids (2n22)
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 (2n22)
• Conservation concern
• I. mattaponica
• melanospora
• I. tegetiformans

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The Genus as Currently Understood II. Seven
Described Allotetraploids (2n44)
Isoetes acadiensis I. appalachiana I. hyemalis
I. louisianensis I. piedmontana I. riparia I.
virginica
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The Genus as Currently Understood
II. Allotetraploids (2n44) Conservation
concerns Cannot be accurately addressed until we
know more about the phylogeny of these
polyploids, at least some of which are
polyphyletic
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The Genus as Currently Understood
III. Three Described Allohexaploids
(2n66) Isoetes georgiana (includes I. boomii)
I. junciformis I. microvela
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The Genus as Currently Understood
IV. Allohexaploids (2n66) Conservation
concerns Cannot be accurately addressed until we
know more about the phylogeny of these
polyploids, at least some of which might be
polyphyletic
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The Genus as Currently Understood
IV. One Allooctoploid (2n88) Isoetes
tennesseensis of conservation concern
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The Genus as Currently Understood
V. One Allodecaploid (2n110) Isoetes lacustris
Of conservation concern in the South, abundant
across Canada
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The Genus as Currently Understood

• VI. Four named primary hybrids
• Isoetes altonharvillii (I. valida x I.
• engelmannii, 2n22)
• I. brittonii (I. engelmannii x I. riparia,
• 2n33)
• I. bruntonii (I. engelmannii x I. hyemalis,
• 2n33)
• I. carltaylorii (I. engelmannii x I.
  acadiensis,
• 2n33)

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Hybrids spores are misshapen and of varying sizes
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Hybrids exhibit heterosis
Isoetes altonharvillii
Isoetes valida
Isoetes engelmannii
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The Genus as Currently Understood
VI. New Taxa There are several diploid
populations that deserve further study, these
could be new species. We have several distinct
tetraploid populations but cannot formally name
them until we understand their phylogeny.
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How are Isoetes species identified?
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Answer With difficulty!
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Megaspores have traditionally been the most
reliable way to identify quillworts
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Until the advent of molecular techniques, megaspor
es 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 Arid Mohammad Al
Zein Jim Allison Jay Bolin Daniel Brunton Cindy
Caplen Kerry Heafner Jim Hickey David Knepper ODU
Plant Research Group Charlie Werth Joe Winstead