The Trillium pusillum Michaux Complex (Trilliaceae): Analysis of Pollen and Leaf Epidermal Micromorphology

Abstract

TIMMERMAN-ERSKINE, M., R. R. DUTE, AND R. S. BOYD (Department of Biological Sciences, Auburn University, AL 36849-5407). The Trillium pusillum Michaux complex (Trilliaceae): Analysis of pollen and leaf epidermal micromorphology. J. Torrey Bot. Soc. 129:175-186. 2002.-The T. pusillum complex consists of five or six southeastern morphogeographical taxa with a confused taxonomic history. Some authors have considered them as a single species, whereas others have split the complex into various combinations of species and varieties. Our study examined pollen and stomatal characteristics of these taxa for their utility as taxonomic characters. All T. pusillum varieties have pollen characterized by somewhat spherical and inaperturate grains with rounded granulate ornamentation. Stomatal complexes lacked subsidiary cells and were aperigenous and homostomatic. Although trends were identified in both pollen diameter and stomatal size and shape, these characters were not reliable variety-specific taxonomic characters. Only T. pusillum var. texanum exhibited both abaxial and adaxial stomata, a feature that consistently distinguished it from other putative varieties that we examined. We suggest that this complex be subdivided into two species, T. texanum Buckley and T. pusillum Michaux, based upon these stomatal distribution patterns.