Abstract Anolis lizards are important models in studies of ecology and evolution. Here we describe 13 polymorphic microsatellites for use in population screening in the St Lucia anole, Anolis luciae , that can be used as a natural replicate to Anolis roquet on Martinique to study processes involved in population differentiation and speciation. Genotyping of 32 individuals using M13 tails and FAM‐labelled universal M13 primers showed that all loci were polymorphic with high genetic diversity, averaging at 16.8 alleles per locus. Genotypic frequencies conformed to Hardy–Weinberg expectations, and there were no instances of linkage disequilibrium between loci.
Abstract Populations of the Caribbean lizard, Anolis roquet , are thought to have experienced long periods of allopatry before recent secondary contact. To elucidate the effects of past allopatry on population divergence in A. roquet , we surveyed parallel transects across a secondary contact zone in northeastern Martinique. We used diagnostic molecular mitochondrial DNA markers to test fine‐scale association of mitochondrial DNA lineage and geological region, multivariate statistical techniques to explore quantitative trait pattern, and cline fitting techniques to model trait variation across the zone of secondary contact. We found that lineages were strongly associated with geological regions along both transects, but quantitative trait patterns were remarkably different. Patterns of morphological and mitochondrial DNA variation were consistent with a strong barrier to gene flow on the coast, whereas there were no indications of barriers to gene flow in the transitional forest. Hence, the coastal populations behaved as would be predicted by an allopatric model of divergence in this complex, while those in the transitional forest did not, despite the close proximity of the transects and their shared geological history. Patterns of geographical variation in this species complex, together with environmental data, suggest that on balance, selection regimes on either side of the secondary contact zone in the transitional forest may be more convergent, while those either side of the secondary contact zone on the coast are more divergent. Hence, the evolutionary consequences of allopatry may be strongly influenced by local natural selection regimes.
Abstract Many wood‐dwelling beetles rely on old hollow trees. In Europe, oaks are known to harbour a species‐rich saproxylic beetle fauna, while less is known regarding other broad‐leaved tree species. Furthermore, the extent to which saproxylic insect species have specialised on different tree species remains unknown. In this study, we sampled beetles through pitfall traps and window traps in four different tree species in a landscape with many old oaks. We recorded 242 saproxylic beetle species of which 27 were red‐listed. After eliminating the species recorded only on a single tree, few cases among the 171 remaining species in the data set were confined to a single tree species. Using odds ratios, we showed that 19 of the 171 beetle species showed significant associations with Quercus robur in at least one of the two trap types. For Acer platanoides, Fraxinus excelsior and Tilia cordata , the corresponding numbers were 6, 2 and 5, respectively. One species showed a negative association with Q. robur . Using meta‐analysis, we quantified the degree of association between the beetle species and the tree species. The associations were most profound among species classified as obligate saproxylic rather than facultative in lifestyle. Overall, a significant association was only found with Q. robur . We conclude that the saproxylic fauna is dominated by non‐specialist species but includes a small proportion of truly host‐tree‐specific species. Furthermore, other broad‐leaved trees can be important as supporting habitats for many saproxylic organisms that have had presumed associations with oaks to date.
Gene flow is often considered to be one of the main factors that constrains local adaptation in a heterogeneous environment. However, gene flow may also lead to the evolution of phenotypic plasticity. We investigated the effect of gene flow on local adaptation and phenotypic plasticity in development time in island populations of the common frog Rana temporaria which breed in pools that differ in drying regimes. This was done by investigating associations between traits (measured in a common garden experiment) and selective factors (pool drying regimes and gene flow from other populations inhabiting different environments) by regression analyses and by comparing pairwise F(ST) values (obtained from microsatellite analyses) with pairwise Q(ST) values. We found that the degree of phenotypic plasticity was positively correlated with gene flow from other populations inhabiting different environments (among-island environmental heterogeneity), as well as with local environmental heterogeneity within each population. Furthermore, local adaptation, manifested in the correlation between development time and the degree of pool drying on the islands, appears to have been caused by divergent selection pressures. The local adaptation in development time and phenotypic plasticity is quite remarkable, because the populations are young (less than 300 generations) and substantial gene flow is present among islands.
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