Connectivity in fragmented populations: Abax parallelepipedus in a hedgerow network landscape

Morphological variation of central-western European populations of Abax parallelepipedus was studied in order to revise the microsystematics of this species. Original descriptions and systematic revisions published since the second half of the 18th century are discussed. Biometric variables and morphometric indexes were evaluated on 792 specimens sampled from several European countries. The data were statistically analysed in order to discriminate the populations significantly differentiated from the nominotypical form. Features of male genitalia are also discussed. The results attest that the morphological variation becomes more relevant among populations inhabiting alpine environments and the Italian ones show the most distinctive modifications of somatic and/or aedeagic traits. On the basis of these results, A. p. euganensis Schatzmayr, 1944 is resurrected from synonymy with A. p. inferior, whereas the following new synonymies are proposed:Abax parallelepipedus parallelepipedus (Piller & Mitterpacher, 1783) = A. p. subpunctatus (Dejean, 1828) syn. nov. = A. p. audouini (L. Dufour, 1851) syn. nov. = A. p. germanus Schauberger, 1927 syn. nov.Abax parallelepipedus inferior (Seidlitz, 1887) = A. p. alpigradus Schauberger, 1927 (sensu Schatzmayr, 1944) syn. nov.A phylogeographical scenario is hypothesized and discussed in the light of the collected data.

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Population size, habitat fragmentation, and the nature of adaptive variation in a stream fish

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2014.0370 ◽

2014 ◽

Vol 281 (1790) ◽

pp. 20140370 ◽

Cited By ~ 31

Author(s):

Dylan J. Fraser ◽

Paul V. Debes ◽

Louis Bernatchez ◽

Jeffrey A. Hutchings

Keyword(s):

Genetic Variation ◽

Habitat Fragmentation ◽

Population Size ◽

Brook Trout ◽

Small Populations ◽

Adaptive Genetic Variation ◽

Genetic Population ◽

Fragmented Populations ◽

Large Populations ◽

Adaptive Differentiation

Whether and how habitat fragmentation and population size jointly affect adaptive genetic variation and adaptive population differentiation are largely unexplored. Owing to pronounced genetic drift, small, fragmented populations are thought to exhibit reduced adaptive genetic variation relative to large populations. Yet fragmentation is known to increase variability within and among habitats as population size decreases. Such variability might instead favour the maintenance of adaptive polymorphisms and/or generate more variability in adaptive differentiation at smaller population size. We investigated these alternative hypotheses by analysing coding-gene, single-nucleotide polymorphisms associated with different biological functions in fragmented brook trout populations of variable sizes. Putative adaptive differentiation was greater between small and large populations or among small populations than among large populations. These trends were stronger for genetic population size measures than demographic ones and were present despite pronounced drift in small populations. Our results suggest that fragmentation affects natural selection and that the changes elicited in the adaptive genetic composition and differentiation of fragmented populations vary with population size. By generating more variable evolutionary responses, the alteration of selective pressures during habitat fragmentation may affect future population persistence independently of, and perhaps long before, the effects of demographic and genetic stochasticity are manifest.

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