Structure of allozyme variation in Nordic Silene nutans (Caryophyllaceae): population size, geographical position and immigration history

Abstract

We investigated allozyme variation in 34 populations of the perennial herb Silene nutans from Sweden and northern Finland, areas that were ice-covered during the last (Weichselian) glaciation. The present geographical structure of genetic variation in S. nutans in Sweden and northern Finland appears to have been mainly shaped by ancient historical processes. Patterns of variation in allele frequencies suggest two major postglacial immigration routes into Sweden, with populations entering the area from both the south and the east and forming a contact zone with admixed populations in central Sweden. While estimates of within-population genetic diversity and allelic richness are significantly correlated with present population size and geographical position (latitude), population size is not correlated with latitude. Low genetic diversity in the northern populations is more likely to have resulted from ancient stochastic events during the process of immigration than from recent population fragmentation. F IS values are high and increase with latitude. Evidence of recent bottlenecks was detected in several southern Swedish populations: these can be interpreted in terms of population fragmentation as a result of anthropogenic disturbance. Soil pH is uncorrelated with population size and position.

Highest genetic diversity at the northern range limit of the rare orchid Isotria medeoloides

“…Another approach to separate the impacts of colonization from more contemporary forces is to consider species whose census population sizes do not decline toward the northern range limit. For example, census size of the herbaceous perennial Silene nutans is uncorrelated with latitude, allowing investigators to conclude that its poleward decline in genetic diversity is due to historical colonization processes rather than more contemporary ones (Van Rossum and Prentice, 2004). Increased genetic diversity toward the northern range limit in previously glaciated regions appears to be an unusual phenomenon.…”

Demographic History Has Influenced Nucleotide Diversity in European Pinus sylvestris Populations

“…Species with a shorter generation time accumulate mutations faster than species with a long generation time. In addition, a fragmented distribution probably results in severe bottlenecks during the colonization, which can be detected as reduced diversity (e.g., Van Rossum and Prentice 2004;Muller et al 2007).…”

Phylogeographic pattern of range expansion provides evidence for cryptic species lineages in Silene nutans in Western Europe

“…These tension zones may be associated with an environmental transition where different genotypic combinations allow differential adaptive values, resulting in a genetic-environment association and ecotypic differentiation (Barton and Hewitt, 1985;Hewitt, 1988;Bierne et al, 2011). Although in southern Belgium the genetic lineages are clearly associated with edaphic properties (for example, Van Rossum et al, 1997), to date, no evidence of such association between genetic variation and soil characteristics have been found elsewhere (Van Rossum et al, 2003;Van Rossum and Prentice, 2004). This inconsistency suggests that the divergence of the two main lineages precedes the specific adaptation to the nature of soil and indicates locally restricted association between edaphic adaptation and lineage identity.…”