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