Genetic diversity and local population structure of fragmented populations of Trillium camschatcense (Trilliaceae)

Abstract

Trillium camschatcense, a long-lived common woodland herb, has been experiencing intensive habitat fragmentation over the last century in eastern Hokkaido, Japan. We examined the genetic diversity and population genetic structure of 12 fragmented populations with different population sizes using allozyme electrophoresis. The percentage of polymorphic loci and mean number of alleles per locus were positively related to population size, probably due to the stochastic loss of rare alleles (frequency of q <0.1) in small populations. Populations with 350 flowering plants or fewer had lost almost all of their rare alleles. While the heterozygosity and inbreeding coefficient were not related to population size, some small populations showed relatively high inbreeding coefficients. In spite of the low genetic differentiation among overall populations (F ST =0.130), local population structuring was recognized between the two geographically discontinuous population groups. Within groups, sufficient historical gene flow was inferred, whereas a low dispersal ability of this species and geographical separation could produce apparent differentiation between groups.

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

“…Contrary to the T. camschatcense investigation (Tomimatsu and Ohara, 2003) and to our expectations, our study did not reveal a significant relationship between the size of T. reliquum populations and genetic variation. Population genetics theory predicts that larger populations are more likely to have higher heterozygosity and greater allelic richness.…”

“…However, even in perennial herbs with widely disjunct populations, for example Tradescantia hirsuticaulis (Godt and Hamrick, 1993) a granite outcrop endemic with a similar geographic range to T. reliquum, or Sarracenia leucophylaf (Wang et al, 2004), another relatively rare southeastern perennial herb, such extreme population variability in genetic diversity is uncommon. In contrast, Tomimatsu and Ohara (2003) reported comparable levels of both species and population genetic diversity in Trillium camschatcense in eastern Hokaido, Japan. In their study area, previously large, continuous populations had been fragmented into smaller remnants.…”

“…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.…”

Genetic diversity and differentiation in Chinese sour cherry Prunus pseudocerasus Lindl., and its implications for conservation

“…Firstly, it was probably closely connected with its small population size and habitat fragmentation. The theory of population genetics indicates that genetic differentiation caused by genetic drift and inbreeding depression should increase in progressively smaller and isolated populations (Templeton et al 1990), as supported by previous reports (Buza et al 2000;Shea and Furnier 2002;Tomimatsu and Ohara 2003). Despite its wide geographic distribution, the habitats of P. pseudocerasus were fragmented into small patches largely due to geographic barriers and anthropogenic activities, and the sizes of the isolated populations, e.g.…”

Genetic diversity and structure in fragmented populations of the endangered species Ranunculus cabrerensis (Ranunculaceae): implications for conservation

“…Experimental and field investigations have demonstrated that fragmented populations may lose allelic richness or genetic diversity, and have increased population differentiation due to genetic drift and inbreeding depression (e.g. Buza et al 2000;Tomimatsu & Ohara 2003). Thus, an accurate estimate of the level and distribution of genetic diversity of threatened and endangered species is an important element in designing conservation programmes (Smith & Wayne 1996;Höglund 2009).…”