Macroecological patterns of genetic structure and diversity in the aquatic mossPlatyhypnidium riparioides

Abstract

Summary Genetic diversity and structure are described in the aquatic moss Platyhypnidium riparioides to assess its dispersal ability at a regional scale and to determine whether patterns of genetic differentiation correlate with environmental variation. Variation at six nuclear microsatellite loci from 50 populations in southern Belgium was investigated through Mantel tests, partial Mantel tests and spatial analysis of molecular variance. Overall patterns of genotypic variation showed strong differentiation among populations at a regional scale (FST = 0.57). The high values of FIS observed within populations at both the ramet and genet levels, and the higher proportion of ramets with the same genotype than expected by chance, all point to a strongly clonal or selfing mating system. A genetic discontinuity was identified between northern and southern groups of populations. Within each group, FST and geographical distances were significantly correlated. Partial Mantel tests suggest that genetic and ecological distances are significantly correlated in the southern group. The results point to strong dispersal limitation at the landscape scale and suggest that the southern and northern groups experienced different histories. Within the former, the correlation between genetic and ecological variation is suggestive of reproductive isolation among ecotypes.

Oceanic islands are not sinks of biodiversity in spore-producing plants

“…First, variation in spatial heterogeneity and habitat diversity of freshwater systems, which was identified as one of the main drivers of genetic diversification in P. riparioides (19), is lower in Macaronesian islands than on the continent, due to their volcanic origin and the physical properties of watersheds (20).…”

“…IM implements an isolation-with-migration model with two populations and six parameters (theta A , theta 1 , theta 2 ; t, m 1 , m 2 ).The neutral coalescent model involves random mating, a condition that is unlikely to be met in P. riparioides owing to its bisexual gametophytes and putatively high selfing rates (19). We therefore selected one individual from each of 72 localities (40 belonging to the continent and 32 to the island region), as advocated by Lessard and Wakeley (52).…”

Biogeography of the Lost World (Pantepui region, northeastern South America): Insights from bryophytes

“…This is best illustrated in the Macaronesian endemic bryophyte flora, wherein endemic species evolved from Neotropical, sub-Saharan Africa, or even eastern Asian ancestors rather than from European or North African ones (Vanderpoorten et al 2010b). Although landscape-scale dispersal limitations were evidenced in a few instances, possibly enhanced by local ecological specialization (Hutsemékers et al 2010), one interpretation for the recruitment of endemics from geographically remote ancestors is that the dispersability of bryophytes precludes the establishment of isolation-by-distance patterns, and hence, opportunities for allopatric speciation, at the scale of tens to hundreds of kilometers.…”

Ploidy level, genetic diversity, and differentiation in two closely related mosses,Scorpidium cossoniiandS. revolvens(Calliergonaceae)

“…there is no retention of deleterious alleles, as in diploid organisms, so that those alleles are eliminated quickly from the genomes of haploid bryophytes (Anderson, 1963). Nevertheless, high levels of genetic diversity in haploid gametophytes have been found as revealed by several kinds of genetic markers, such as RAPDs and isozymes (Cummins & Wyatt, 1981;Wyatt et al, 1989Wyatt et al, , 2005Stenøien & Så stad, 1999), ISSRs (Spagnuolo et al, 2007;Buczkowska et al, 2010), and microsatellites (Wilson & Provan, 2003;Shaw et al, 2008;Hutsemekers et al, 2010). It is suggested that genetic diversity in haploid bryophytes could be maintained by multiple-niche selections (Wyatt et al, 1989), interlocus interaction, i.e.…”

“…Diploids have also been found in the Brachytheciaceae (Platyhypnidium riparioides (Hedw.) Dixon: Hutsemekers et al, 2010) and Calliergonaceae (Warnstorfia, Scorpidium: Nagl & Ullmann, 1973;Hedenä s, 1989;Fritsch, 1991). Near or total fixation for two alleles per locus per individual leads to the assumption that polyploids in bryophytes are mainly of allopolyploid origin (Så stad, 2005;Shaw, 2009;Karlin et al, 2010a).…”