Genetic Structure in a Heterocyanic Population of Trillium sessile (Liliaceae)

Abstract

Species of Trillium in the subgenus Phyllantherum are either polymorphic for flower color, or monomorphic for flower color and related to a polymorphic species. This leads to the suggestion that polymorphic species may be the progenitors for monomorphic ones. For this to be true, it must be demonstrated that genetic divergence among flower morphs can occur within polymorphic populations. Genetic structure was assessed in a population of T. sessile that contains a polymorphism for flower color. A survey of 11 enzyme systems using starch gel electrophoresis revealed three polymorphic loci: 6PGD‐1, AAT‐1 and AAT‐2. Analysis of large and small scale spatial structure, stage classes, and flower color classes revealed significant genetic divergence in all instances. Spatial structure in the population is likely a result of genetic neighborhoods which can maintain populational variation via random genetic drift. Genetic divergence of the yellow flower color morph was probably initiated through genetic drift since the morph occurs in low frequencies. The results imply that the initial genetic divergence of species in the subgenus can arise within polymorphic populations.

Is the Baekdudaegan “the Southern Appalachians of the East”? A comparison between these mountain systems, focusing on their role as glacial refugia

“…Although for northeastern Asia there are no congeneric comparisons between species occurring on the BDDG and more northern congeners (i.e., occurring in northeastern China and/or in Russian Far East), many of such south-north congeneric comparisons are available in North America. These studies have consistently revealed lower genetic variability in northern species compared to their southern congeners (Bayer et al, 1987;Whitkus et al, 1987;Lewis and Crawford, 1995;Hannan and Orick, 2000), in agreement with the refugial role of the Southern Appalachians. For example, Lewis and Crawford (1995) found that the more southerly species of each of several closely related species of Polygonella pairs consistently had higher gene diversity, regardless of life span (annuals vs. perennials) and floral traits (hermaphroditic vs. dioecious, etc.).…”

Genetic variation in Trillium erectum (Melanthiaceae), a widespread forest herb in eastern North America

“…A geographical survey of T. grandiflorum, a predominantly outcrossing species (Broyles et al 1997;Kalisz et al 1999;Sage et al 2001) with a similar range to T. erectum, found similar overall levels of genetic diversity but less inbreeding (Griffin and Barrett 2004). In contrast, T. erectum has considerably more diversity at allozyme loci than Trillium nivale (Bayer et al 1987) and Trillium sessile (Whitkus et al 1987), two species with much smaller geographical ranges.…”

Distribution of genetic diversity among disjunct populations of the rare forest understory herb, Trillium reliquum

“…Most of the total genetic variation in T. cuneatum, is contained within populations (G ST ¼ 0.092; G ST ¼ 0.110 for loci with H T 40.10). Several studies of allopatric Trillium species reported variable levels of genetic diversity and its distribution (eg Bayer et al, 1987;Whitkus et al, 1987;Tomimatsu and Ohara, 2003;Griffin and Barrett, 2004). G ST values (or its analogs F ST and y) reported in these studies ranged from 0.095 to 0.35.…”