Population genetics of threatened wild plants in Japan

Abstract

Approximately one-fourth of Japan's native plant species are threatened with extinction. To conserve these species, it is critical to evaluate genetic diversity at specieslevel and population-level. Some factors, including population size and geographic distribution, are known to influence the population genetic diversity of wild plant species. This article briefly reviews the population genetic studies that have been conducted on wild threatened plants in Japan. A large population size or wide geographic distribution does not always lead to large genetic diversity, suggesting that historical factors such as speciation processes and population expansion often play more important roles in determining genetic diversity than the number of remnant individuals. The mating system of a species also affects genetic diversity; predominantly selfing species tend to have smaller genetic diversity than outcrossing congeners. Another issue of concern in the conservation genetics of wild plants in Japan is the genetic diversity of insular endemics, because Japan consists of many islands, and the insular flora contains many endemic and threatened species. Previous studies on endemic plants on the Bonin and the Ryukyu Islands are reviewed. Compared to the cases of the Bonin Islands or other oceanic islands, there is much larger genetic diversity in plants endemic to the Ryukyu Islands. This difference is probably the result of the differences in the geological history of these islands.

Environmental determinants of genetic diversity inCaragana microphylla(Fabaceae) in northern China

“…Genetic variation is nonrandomly distributed among populations and species (Nevo, ), with the distribution of alleles and genotypes over space and time often affected by numerous factors such as breeding system, seed dispersal mechanism, geographical range, life form and natural selection (Hamrick & Godt, ; Hamrick et al ., ; Maki, ; Meloni et al ., ).…”

The biogeography of plant reproduction: potential determinants of species’ range sizes

“…Tests of these hypotheses have been limited by the large scales involved and by difficulties in quantifying the relevant parameters. For example, studies aimed at understanding plant distribution patterns often compare rare vs. common plants for suites of traits that are correlated to their status as rare or common, although most authors readily admit that generalized conditions of rarity or abundance are unlikely to be attributable to any one factor (Watson, 1833;Cruden, 1977;Karron, 1987;Murray et al, 2002;Maki, 2003;Lavergne et al, 2004Lavergne et al, , 2005Shapcott et al, 2005) As a result of these methodological difficulties, a general explanation for range size variation has yet to emerge.…”

“…The mating system of a species has also been correlated with the level of genetic diversity maintained in populations and across species (Levin, 1968;Carr & Fenster, 1994;Charlesworth & Charlesworth, 1995;Hamrick & Godt, 1996). Diploid species that self-fertilize tend to reduce the allelic diversity in a population and thus are associated with lower population-level genetic diversity (Hamrick & Godt, 1990;Maki, 2003;Pound et al, 2004). The consequences of mating system on genetic diversity in polyploids are less clear, because the features of selffertilization in diploids that would lead to fixation for alleles do not operate in the same way.…”

Higher ploidy is associated with reduced range breadth in the Potentilleae tribe

“…Identifying the factors that determine species' distributions can inform predictions of how ranges will respond to global change (Karron, 1987;Maki, 2003;Lavergne et al, 2005;Jiménez-Valverde et al, 2011). Key factors that are associated with plant range size include abiotic limitations, biotic interactions, and intrinsic species characteristics (e.g., mating system [Lowry and Lester, 2006;Johnson et al, 2014;Grossenbacher et al, 2015], genetic diversity [Karron, 1987;Pound et al, 2004], and functional traits [Walker et al, 1999;Díaz and Cabido, 2001]).…”