Genetic variation and structure in the expanding moss Pogonatum dentatum (Polytrichaceae) in its area of origin and in a recently colonized area

Abstract

Genetic variation in the expanding moss species Pogonatum dentatum was studied using intersimple sequence repeat (ISSR) markers. The genetic consequences of range expansion were studied by comparing source populations in a mountain area with populations from a recently colonized lowland area in Sweden. Indices of genetic variation show slightly lower number of alleles per locus in the lowlands and a similar gene diversity in both areas. Three of four lowland populations had evidence of a recently passed bottleneck. Considerably higher haplotype diversity was found in the recently colonized lowlands compared to source populations in the mountains. Patterns of allelic diversity suggest that P. dentatum experiences loss of genetic variation through founder effects and genetic drift when expanding its distribution range. Higher haplotypic diversity, less linkage disequilibrium, and fewer compatible loci indicate that sexual recombination is relatively more important in the lowlands compared to the mountains. A likely explanation is higher success of establishment from spores in the lowlands, while clonal propagation predominates in the mountains. Less genetic differentiation among lowland populations indicates more gene flow in the lowland area, involving more spores and/or fragments moving among populations.

Molecular biodiversity in the moss Leptodon smithii (Neckeraceae) in relation to habitat disturbance and fragmentation

“…In addition, the high linkage among loci calculated in urban populations and the pattern of haplotypic sharing among trees could represent the result of spore dispersal in the past. All these observations maintain the hypothesis of a step-by-step dispersal of spores (Hassel et al 2005) and, in line with the results reported by coworkers (2004a, 2004b) in two Orthotrichum species and Neckera pennata, suggest a limited dispersal range for L. smithii spores, mainly affecting nearby trees. Asexual diaspores could also contribute to short-range dispersal and gene flow; in fact, it has been reported for Tetraphis pellucida that gemmae promote local colonisation (within a range of a few centimetres), whereas spores ensure long-distance dispersal (Kimmerer 1991).…”

“…Indeed, if sexually produced spores are the main agent of dispersal, no linkage among loci is expected; but high linkage value is expected if asexual reproduction by fragments is dominating (Hassel et al 2005). Multilocus linkage disequilibrium (r d ) was calculated using the index of association modified to remove the dependency of sample size (Agapow and Burt 2001).…”

“…Genetic variation is investigated by using internal simple sequence repeat (ISSR), which are molecular markers already employed by other authors Hassel et al 2005;Spagnuolo et al 2007) in studies concerning moss populations, providing easily available data, to obtain currently used molecular indices and information on the genetic structure of the investigated populations. All results are discussed in relation to population ecology and habitat disturbance and fragmentation.…”

Genetic variation in the invasive weedMikania micrantha(Asteraceae) suggests highways as corridors for its dispersal in southern China

“…First, if the weeds' expansion along highways was driven mainly by natural forces (presumably by wind, as this species produces typical achene-pappus units), then it would be restricted to short-distance (step-by-step) dispersal and would experience a series of population bottlenecks and genetic drift during colonization. Reductions in both allelic richness (AR) and genetic diversity would be expected for the roadside populations as the distance from Shenzheng (the first area invaded in mainland China by M. micrantha) increased (Hassel et al, 2005;Ma et al, 2011;Li and Geng, 2015). Second, if the expansion was facilitated by anthropogenic activity (vehicle transportation), then the weed would undergo long-distance dispersal.…”

Glacial refugia and post-glacial colonization patterns in European bryophytes

“…Pleurochaete squarrosa (Grundmann et al 2007) Rapid population growth maintaining polymorphisms in an area despite recent colonization (Waxman 2012) and/or the area being a post-glacial contact zone (Provan and Bennett 2008) High level of unique alleles and haplotypes (Ehrich et al 2008) e.g. Homalothecium sericeum (Hedderson and Nowell 2006) Admixture in contact zone leading to unique haplotypes (Hassel et al 2005) Root of gene trees or haplotype network close to haplotypes found in an area e.g. Grimmia montana (Vanderpoorten et al 2008) Several refugial areas (Laenen et al 2011) Low mutation rate and/or large effective population size causing incomplete lineage sorting (Stenøien and Såstad 1999) probable origin before the LGM (Stenøien et al 2011b).…”