keys to the vascular plants of east texas - Botanical Research ...

466 ARACEAE/COLOCASIA
subsp. quinatum into subsp. pusillum, but they noted that they had not seen living material of
plants with 5 leaflets. Geraldine Watson (pers. comm.) noted that in the Big Thicket the two local
forms are recognizable both morphologically and by habitat (subsp. quinatum in drier situations)
and are distinct enough to be separate species. While the taxonomy of this complex is not settled,
because two kinds are recognizable in East TX, we are following the in-depth treatments by
Huttleston (1981, 1984) in recognizing two subspecies in East TX (not distinguished on the county
distribution map). However, hybridization between the subspecies (Huttleston 1984), morphological
intergradation, and sympatry of the subspecies over a large portion of their ranges
(Treiber 1980) do make the recognition of a single variable species without varieties or subspecies
(Thompson 2000b) an attractive option. Individual plants are long-lived, with a life span of 15–25
years (Bierzychudek 1982). Vegetative reproduction by means of stolons is apparently common
(Treiber 1980; Guzman & Guzman 2002). The fleshy fruits are eaten and dispersed by birds and
probably also mammals (Bierzychudek 1982). Pollination by fungus gnats (order Diptera; family
Mycetophilidae) (Treiber 1980) and thrips (small insects in the order Thysanoptera) (Rust 1980)
has been reported in this species. The corms were used as food and medicine by Native Americans
but can be eaten only after special preparation (Guzman & Guzman 2002). The tissues contain
injurious calcium oxalate raphides (Lampe & McCann 1985). �
1. Primary leaf divided into 5 leaflets (the lateral lobes sometimes not completely separated into
leaflets); spathe blade ovate with apiculate tip, unmarked green or yellow-green; distal portion
of spadix 2 mm or less in diam., bent, cylindric _____________________________________ subsp. quinatum
1. Primary leaf divided into 3 leaflets; spathe blade broadly lanceolate to broadly ovate with acute
to acuminate tip, usually marked with purple or red-brown; distal portion of spadix � 3 mm in
diam., straight, cylindric or usually somewhat clavate (= club-shaped) __________________ subsp. triphyllum
subsp. quinatum (Buckley) Huttl., (in fives). While the primary leaf is divided into 5 leaflets, the
typically smaller secondary leaf often has 3 leaflets. Moist woods, in similar, but often somewhat
drier habitats than subsp. triphyllum; Cherokee, Jasper, Liberty (BRIT), Hardin (TAMU),
San Jacinto (TAES), Angelina, Nacogdoches, Sabine, and San Augustine (ASTC) cos.,
Pineywoods; se U.S. from NC s to FL w to TX. [A. quinatum (Buckley) Schott]
subsp. triphyllum. Lateral leaflets occasionally lobed on the outer margins. Moist woods, widespread
in the Pineywoods; also n Gulf Prairies and Marshes; recently a large disjunct population
was discovered in Parker Co. in the Cross Timbers and Prairies (O’Kennon 16024, BRIT); se
Canada and throughout e U.S. w to ND and TX. [A. atrorubens (Aiton) Blume] This is by far the
most common subspecies in TX; large variable populations are sometimes observed (e.g., in
Cass Co.). The Parker Co. population, disjunct from East TX by 140 miles (225 kilometers), occurs
in a “rockhouse” microhabitat between sandstone/conglomerate rock walls. Few inflorescences
were observed in this population, which is apparently reproducing primarily by vegetative
means. This occurrence probably represents an “Ice Age holdover” (MacRoberts &
MacRoberts 1997a) from a colder and wetter period of the Pleistocene when vegetational areas
were shifted considerably to the south and west (Diggs & O’Kennon 2003; also see Kral 1966c,
Delcourt & Delcourt 1993, and the introduction in this volume (page 209) for a discussion of
glacial influences on plant distribution). Interestingly, another species known from this same
Parker Co. location, Carya ovata (SHAG-BARK HICKORY), is also disjunct from the e part of East
TX. Such persistence in climatically moderated “rockhouse” environments has been documented
for a variety of plant species in the e U.S., including some endemics (e.g., Walck et al.
1996; Farrar 1998). m/276
COLOCASIA Schott TARO, DASHEEN, COCO-YAM, ELEPHANT’S-EAR
AA tropical Asian genus of 7 species (Thompson 2000b) of tuberous herbs with peltate leaves;
some species are used as ornamentals and for food. � All parts of Colocasia species, except the