Genetic variation and plant performance in fragmented populations of globeflowers (Trollius europaeus) within agricultural landscapes

Abstract

The management of remnant populations in highly fragmented landscapes requires a thorough understanding of the processes shaping population persistence. We investigated relationships between population characteristics (i.e. size, density and pollinator abundance), offspring performance, genetic diversity and differentiation in Trollius europaeus, a plant with a nursery pollination system. In 19 populations of different sizes and located in north-east Switzerland, an area which has undergone widespread land use changes over the last decades, we assessed neutral genetic diversity (N total = 383) using AFLPs and plant performance in a greenhouse experiment (N total = 584) using competition and control treatments. Overall genetic differentiation was low (F ST = 0.033) with a marginal significant isolation by distance effect (P = 0.06) indicating (historical) genetic connectivity among the populations. Mean expected heterozygosity was H E of 0.309 (0.0257-0.393) while inbreeding coefficients (F IS ) were significant in only three populations. Genetic diversity was not related to population size, plant density or pollinator abundance. Plant performance was reduced under competition (P \ 0.001) but the severity of competition was independent of genetic diversity and population size. In summary, remnant populations of T. europaeus retain genetic diversity and seem capable of persisting under the present conditions within an agricultural matrix. T. europaeus is a perennial herb, thus it may require several generations for the negative effects of fragmentation and isolation to manifest. Our findings indicate that small populations are as important as large populations for the conservation and management of genetic resources.

Lessons from a palm: genetic diversity and structure in anthropogenic landscapes from Atlantic Forest, Brazil

“…Our results indicate that, regardless of the amount of forest cover remaining at the landscape level, the genetic diversity of E. edulis was still high at all sampling sites and was quantitatively similar to other populations of the same species (Gaiotto et al 2003;Conte et al 2008, Carvalho et al 2015. This pattern may reflect the recent history of deforestation because land-use change is often faster than those organisms change genetically (Holzhauer et al 2006), and because small populations can may still maintain high genetic diversity due to very recent population declines (Klank et al 2012). Given this time lag of deforestation impact, high levels of genetic diversity in populations can be maintained even in less forested landscapes.…”

“…Thus, the global value of F IT remains close to zero, which can be misinterpreted as panmixia and a metapopulation connected by gene flow. An alternative but not mutually exclusive hypothesis is that the lower genetic (Klank et al 2012). As E. edulis is an allogamous and long-distance dispersed species (Gaiotto et al 2003), we believe that the efficiency in seed dispersal among forest remnants is possibly compromised by the low richness and abundance of seed dispersers (Moran and Catterall 2014).…”

The structural and functional connectivity of the grassland plant Lychnis flos-cuculi

“…In the present study, this index was based on population size, and Leimu et al (2006) showed that larger populations are generally characterised by higher genetic diversity. However, small populations may still contain substantial genetic variation if they represent remnants of recently larger populations (Landergott et al, 2001;Klank et al, 2012) and thus the relationship between population size or related indices and genetic diversity may not have re-established yet.…”

“…A previous study examining current levels of gene flow among the same populations of L. flos-cuculi as studied here revealed that present-day functional connectivity of this species is indeed low (Aavik et al, 2013), and therefore it is likely that genetic differentiation F ST rather represents historical than current functional connectivity in our study landscape. The most dramatic landscape changes in Switzerland took place in the second half of the twentieth century (Schultz and Dosch, 2005), and thus the effects of these changes on the genetic differentiation of perennial plants might only become traceable in the future (Honnay et al, 2006;Klank et al, 2012).…”

Neutral and quantitative genetic differentiation among Trollius europaeus populations within a fragmented landscape

“…Bars denote the 95 % confidence intervals (CIs) occurred (Klank et al 2012). A marginal isolation by distance effect found among more populations in the same study region by Klank et al (2012) suggests that gene flow decreases with increasing distance. In contrast, our datasets of all as well as the large populations did not indicate isolation by distance.…”