Microsatellite variation and structure of 28 populations of the common wetland plant, Lychnis flos‐cuculi L., in a fragmented landscape

Abstract

Habitat fragmentation is known to cause genetic differentiation between small populations of rare species and decrease genetic variation within such populations. However, common species with recently fragmented populations have rarely been studied in this context. We investigated genetic variation and its relationship to population size and geographical isolation of populations of the common plant species, Lychnis flos-cuculi L., in fragmented fen grasslands. We analysed 467 plants from 28 L. flos-cuculi populations of different sizes (60 000-54 000 flowering individuals) in northeastern Switzerland using seven polymorphic microsatellite loci. Genetic differentiation between populations is small (F(ST) = 0.022; amova; P < 0.001), suggesting that gene flow among populations is still high or that habitat fragmentation is too recent to result in pronounced differentiation. Observed heterozygosity (H(O) = 0.44) significantly deviates from Hardy-Weinberg equilibrium, and within-population inbreeding coefficient F(IS) is high (0.30-0.59), indicating a mixed mating breeding system with substantial inbreeding in L. flos-cuculi. Gene diversity is the only measure of genetic variation which decreased with decreasing population size (R = 0.42; P < 0.05). While our results do not indicate pronounced effects of habitat fragmentation on genetic variation in the still common L. flos-cuculi, the lower gene diversity of smaller populations suggests that the species is not entirely unaffected.

Genetic variation and differentiation in populations of a threatened tree, Magnolia stellata: factors influencing the level of within-population genetic variation

“…Many studies have reported significant relationships between population size and genetic variation (for example, Young et al, 1999;Galeuchet et al, 2005;Gao, 2005;Leim et al, 2006). However, a previous study on M. stellata published by Nakashima and Sakai (2003) did not detect such a relationship, possibly because the measure of population size they used was not the number of reproductive individuals but the number of individuals within populations.…”

“…Since it is more difficult to measure the Genetic variation in Magnolia stellata populations I Tamaki et al degree of population isolation than population size, good measures for quantifying the degree of population isolation have not yet been established. However, we detected significant relationships between the degree of population isolation and genetic variation, using the number of surrounding populations as the measure of isolation, whereas the distance from the nearest population was used in many previous studies (for example, Llorens et al, 2004;Galeuchet et al, 2005;Lu et al, 2005). Thus, the detection of a significant relationship in this study, and the failure of many of the cited studies to detect such relationship, supports the assertion by Moilanen and Nieminen (2002) that the number of surrounding populations is a much better indicator of isolation than the distance from the nearest population.…”

“…Thus, it is important to consider the effects of these variables in analyses of genetic variation, but choosing the best measures for them is not straightforward. Many authors have used the actual number of individuals within investigated populations as a measure of population size, assuming that it is correlated with their effective population size, and found stronger relationships between this variable and genetic variation (for example, Young et al, 1999;Galeuchet et al, 2005;Gao, 2005;Leim et al, 2006). The degree of population isolation can be quantified by measuring positional relationships between a focal population and its surrounding populations.…”

“…The simplest way of doing this is to measure the distance to the nearest population. This approach has been used by various authors (for example, Llorens et al, 2004;Galeuchet et al, 2005;Lu et al, 2005), but few have found significant relationships between this parameter and genetic variation (Lu et al, 2005), probably because it provides a too simplistic indication of isolation (Moilanen and Nieminen, 2002). The cited authors studied possible connectivity measures in spatial ecology and recommended use of a 'buffer measure' based on the number of populations within a given radius around the focal population rather than simply the distance to the nearest population.…”

Microsatellite diversity and population genetic structure of redfin culter (Culter erythropterus) in fragmented lakes of the Yangtze River

“…Nonetheless, there are inherent difficulties in detecting genetic consequences of recent habitat fragmentation on natural populations due to complex reasons such as the influence of historical population structure (Avise et al, 1987;Cunningham & Moritz, 1998) or the dispersal characteristics of species itself (Keyghobadi et al, 2005). Some scientists claimed that human-induced habitat fragmentation might be too recent to detect pronounced genetic effects in some situations, especially for high gene flow species (Sumner et al, 2004;Galeuchet et al, 2005). On the other hand, given the appropriate control populations, some scientists still have identified the effect of recent habitat fragmentation in terms of decreased genetic diversity and increased differentiation (Williams et al, 2003;Keller & Largiader, 2003).…”