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

1132 TRILLIACEAE/TRILLIUM
(1999), the majority of species “are associated with remnants of the ancient Arcto-Tertiary forests,
which have persisted with dramatic changes in geographical ranges since the early Tertiary
period in the northern hemisphere …” Three other small genera (including Paris) are
closely related (see e.g., Kato et al. 1995b), and Zomlefer (1996) speculated that phylogenetic
analyses may result in the species in these three genera being put into a more broadly delimited
genus Trillium. The genus has often been treated in the Liliaceae (e.g., Correll & Johnston 1970)
or more recently in the Trilliaceae (e.g., Zomlefer 1996; Tamura 1998d; Judd et al. 1999) or a
broadly defined Melanthiaceae (e.g., APG II 2003). Trillium has been divided into two groups
(those with pedicellate flowers versus those with sessile flowers—e.g., Freeman 1975). However,
different varieties of T. pusillum Michx. have both flower types, and pollen morphology does
not support such a division (Takahashi 1982). Recent molecular evidence indicates that the
sessile-flowered species of Tr illium form a monophyletic group, while the pedicellate-flowered
species do not (Kazempour Osaloo et al. 1999).
Morphologically, Trillium plants “produce no true leaves or stems above ground. The horizontal
rhizome produces dry, scalelike leaves (cataphylls). The above-ground plant is a flowering
scape, and technically the leaflike structures are bracts subtending the flower” (Case 2002).
Although the plants are small, some individuals can live for at least 30 years (Hanzawa &
Kalisz 1993). Pollination by dipterans (red-flowered species) and hymenopterans (white-flowered
species) has been reported (e.g., Irwin 2000), but self-pollination is probably prevalent
(Zomlefer 1996). Some species have seeds with arils or elaiosomes (= external food bodies) and
are ant-dispersed (Handel et al. 1981; Mesler & Lu 1983; Kalisz et al. 1999); such a dispersal system
is common among temperate forest herbs (Beattie & Culver 1981; Handel et al. 1981).
Elaiosomes on some Tr illium species have also been found to attract yellow jackets, which apparently
also serve as dispersal agents (Zettler et al. 2001). Flower color polymorphisms (= multiple
flower color forms) occur widely in Trillium, and in T. sessile L. (of e North America) the
polymorphism is thought to have a relatively simple genetic basis, possibly based on a single
gene mutation with incomplete dominance (Les et al. 1989). Several East TX species (e.g., T. gracile)
show similar patterns of variation in flower color. Some species have been used medicinally
(based on the presence of sapogenins) as astringents, coagulants, expectorants, and uterine
stimulants; common names such as BIRTHROOT and INDIAN-BALM reflect these uses (Zomlefer
1996; Case 2002). � According to Case (2002), “Fruits, seeds, and rhizomes of trilliums are generally
considered to be poisonous.” Trilliums are widely cultivated (Zomlefer 1996), but according
to Yatskievych (1999), they are “relatively difficult to grow from seed; plants must be several
years old before they will flower. Consequently, many of the plants sold at nurseries have been
excavated from natural populations by unscrupulous collectors. This has adversely affected
several of the species and the habitats in which they grow. Because of this and because many
such plants were excavated without proper care and will not survive transplantation, gardeners
are urged to become aware of the sources for their plants and to insist on nursery-propagated
plants grown from seeds or rhizome divisions of cultivated stocks.”
As with other native plants, many of which are becoming increasingly rare, collection of
wild material to transplant should only be done when the natural population will not be adversely
affected or will be imminently destroyed (e.g., when a natural area is to be destroyed for
development, etc.). Recent studies (Jules 1998; Jules & Rathcke 1999) of the effects of habitat
fragmentation on Trillium ovatum Pursh in the Pacific Northwest raise concerns about trilliums
in East TX. Jules (1998) found that “the process of clearcutting and subsequent conifer planting
results in the mortality of almost all trillium.” While such studies have not been done for East
TX, clearcutting, soil-shredding, and “coniferization” are widespread in East TX, and populations
of trilliums and other native species are certainly being reduced at a rapid rate. In addition,
research suggests that high deer populations “can lead to local extirpation of selected forbs
such as Trillium in forest fragments and can inhibit efforts to restore populations” (Augustine
& Frelich 1998). Trillium species exhibit considerable variation (e.g., flower color), resulting in