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

Abstract

We assessed genetic diversity and its distribution in the rare southeastern US forest understory species, Trillium reliquum. In all, 21 loci were polymorphic (P S ¼ 95.5%) and the mean number of alleles per polymorphic locus was 3.05. However, genetic diversity was relatively low (H es ¼ 0.120) considering the level of polymorphism observed for this outcrossing species. A relatively high portion of the genetic diversity (29.7%) was distributed among populations. There was no relationship between population size and genetic diversity, and we did not detect significant inbreeding. These results are best explained by the apparent self-incompatibility of this species, its longevity and clonal reproduction. To address questions regarding the history of T. reliquum's rarity, we compared results for T. reliquum with that of its more common and partially sympatric congener, T. cuneatum.Despite shared life history traits and history of land use, we observed significant genetic differences between the two species. Although T. cuneatum contains slightly lower polymorphism (P s ¼ 85%), we detected significantly higher genetic diversity (H es ¼ 0.217); most of its genetic diversity is contained within its populations (G ST ¼ 0.092). Our results suggest that not only is there little gene flow among extant T. reliquum populations, but that rarity and population isolation in this species is of ancient origins, rather than due to more recent anthropogenic fragmentation following European colonization. The Chattahoochee River was identified as a major barrier to gene exchange. Heredity (2005) 95, 306-314.

Genetic diversity and differentiation in six species of the genus Rhinanthus (Orobanchaceae)

“…At the same time, our data showed that total genetic diversity at species level was higher in widespread R. angustifolius and R. rumelicus compared with the insular endemic R. osiliensis (Table 4). This result is in agreement with many other studies, which found that endemics nearly always had lower levels of genetic diversity compared with common species (Gonzales and Hamrick 2005;Gibson et al 2008;Gonzales-Perez et al 2009;Talve et al 2011). The genetic variation in populations of R. angustifolius varied considerably.…”

Genetic diversity of a relict plant species, Ligularia sibirica (L.) Cass. (Asteraceae)

“…Most of the studies on effects of habitat fragmentation are dealing with processes that occurred in the last decades or centuries due to human activities (Gonzales and Hamrick, 2005) such as changes in land use (e.g. Jacquemyn et al, 2003;Robinson and Sutherland, 2002;Stoate et al, 2001).…”

The effect of the shape of gaps on microenvironmental conditions and seedling recruitment in Molinietum caeruleae meadows

“…Secondary succession frequently leads to the fragmentation of communities and isolation of populations [5][6][7]. Small and isolated populations may suffer from a low level of genetic diversity and a high risk of individual mortality, frequently resulting in their extinction [8][9][10][11]. On the other hand, Czarnecka and Denisow [12] argued that genetic variability of small populations might be improved by long-distance moving pollinators.…”