ABSTRACT The Trillium pusillum Mic...

ABSTRACT

The Trillium pusillum Michaux compounded consists of five or six morphogeographical taxa distributed within the southeastern United States. A quantitative morphological reflection was undertaken to determine appropriate species and varietal ranks of these taxa, which have a confused taxonomic history. Numerical analyses based onward 14 floral and vegetative characters measured from 29 populations of T pusillum revealed significant differences among varieties. These exist, however, as arrays of characters rather than as single characters. All characters were highly variable within and among populations, suggesting that quantitative measurements alone are unreliable as distinguishing characters. We conclud that all of the previously recognized infraspecific taxa lack clear morphological separation. We therefore attract favor to recognition of a single variable species without varietal designations.

INTRODUCTION

The genus Trillium L is divided into sum of two units subgenera: subgenus Trillium L., which includes pedicellate-flowered species; and subgenus Phyllantherum Raf, which includes sessile-flowered species. The Trillium pusillum composed of several elements within subgenus Trillium is unique in having the two flower types (Freeman 1994). The T pusillum compounded consists of five or six taxa growing in widely scattered populations forward the coastal plain from Maryland to southerly Carolina, and in isolated inland populations in Alabama, Tennessee Kentucky West Virginia, Mississippi, Louisiana, Texas, Arkansas, and Missouri (Timmerman-Erskine 1999)

Varieties or species in this involved have usually been split from variety pusillum using a number of criteria. In a certain cases, subtle morphological differences have been used to separate taxa. For example, Case and Case (1997) differentiated variety texanum from variety pusillum through its more narrow leaves with more globulared tips, and its narrow, almost linear (but variable) petal shape. Pedicel extent has been an important differentiating character. For example, varieties texanum and ozarkanum have the longest pedicels whereas those of variety virginianum are short (

Habitat also has been used to justify varietal status in a certain quantity of cases. Most populations of T pusillum be met with in low swampy woods or floodplains object for populations of variety ozarkanum which come to pass in coarsely cherty, well-drained hard soils in beech-oak and mixed deciduous forests (Case and Case 1997 Freeman 1994) Likewise, a not many small rare populations of variety virginianum reported from hard shaley soil of mountain crowns along the Virginia-- West Virginia state line were separated as variety monticulum (Bodkin and Reveal 1982) following studies of these latter populations failed to point out any morphological evidence (Cabe 1995) or isozyme evidence (Cabe and Werth 1995) to support taxonomic separation from variety virginianum growing in more typical T pusillum habitat.

Finally, perceived distribution disjunctions have been used to justify taxonomic separation of an elements. This was the case for variety monticulum mentioned above, whose mountain populations were located far east of the coastal plain populations of variety virginianum. Similar apparent disjunctions were important justifications for separation of T texanum (Buckley 1861) and T ozarkanum (Palmer and Steyermark 1935) from T pusillum. However, Freeman (1994) allude toed that these disjunctions are not as wide as had been speculation but stem from inadequate floristic exploration of southeastern states.

Taxonomic opinion regarding members of the T pusillum tangled skein has varied greatly. Table 1 provides a brief summary of the history of taxa in this group; more detailed taxonomic histories are provided on Freeman (1994) and Timmerman-Erskine (1999) Briefly, T pusillum was described by the agency of Michaux (1803), and several morphologically similar species or varieties have been described in the last 200 years (Table 1) For example, T ozarkanum Palmer & Steyermark and T texanum Buckley have as well-as; not only-but also; not only-but; not alone-but been considered to be varieties of T pusillum (Roe 1978 Reveal and Broome 1981) Garrett (1982) recognized sum of two units varieties in the eastern coastal states, varieties pusillum and virginianum, and a of the present day inland taxon (variety alabamicum), nevertheless the latter was not formally published. Cabe (1995) insinuateed that varieties monticulum and virginianum be treated as undivided variety. Even the range of T pusillum, originally described from southward Carolina, has been the control of much controversy (Freeman 1994)

Cabe and Werth (1995) indicateed several reasons for these taxonomic disagreements. First, populations are frequently disjunct and morphologically variable. secondary field observations are limited and frequently inaccurate because flowers are inconspicuous, plants heyday early in the season, and taxa of this webwork are relatively rare. Finally, more [i]or[/i] less useful distinguishing characteristics change as flowers age (Peattie 1927) or are missing or altered when flowers are crowded and dried (Duncan and Calhoun 1962)

Two Trillium species (T persistens and T reliquum) are rare enough to be listed as Federally Endangered (United States Fish and Wildlife Service 1978 1988) As a whole, members of the T pusillum intricate are rare; thus, some may be appropriate for listing. common information on the appropriate nomenclature and taxonomic status of members of this manifold is needed to determine appropriate conservation actions. This application of mind examines quantitative morphological differences between varieties and populations of the T pusillum compound to assist in determining appropriate species and varietal ranks.