01412nas a2200181   4500008004100000245006400041210006300105300001400168490000700182520089500189653001501084653001401099653001201113653001101125653002701136100002701163856004001190       1980                        eng d00aSexual Isolation, Speciation and the Direction of Evolution0 aSexual Isolation Speciation and the Direction of Evolution  a437–4440 v343 aVarious concepts of evolutionary biology are reviewed to emphasize the significance of premating isolation barriers in processes of speciation. Concepts such as sexual selection, genetic drift, and the Founder Principle appear to lend support to Muller's views that premating isolating mechanisms arise as by-products of natural selection in allopatry. Examples are presented in support of this view and in contrast to that held by Fisher and Dobzhansky, who envisioned such mechanisms as arising upon recontact of populations in which some postmating isolating mechanism had arisen. Additionally, a hypothesis proposed by Kaneshiro (1976) which enables interpretation of the one-sided mating preference (asymmetrical isolation) observed between populations of Drosophila is discussed. Such a hypothesis, if valid, permits inferences of direction of evolution among closely related species.10adrosophila10aevolution10ainsects10amating10areproductive-isolation1 aKaneshiro, Kenneth, Y.  uhttp://www.jstor.org/stable/240821302778nas a2200205   4500008004100000245013500041210006900176260004000245300001100285490000600296520210600302653001402408653001202422653001302434653001002447100002202457700001802479700002402497856005102521       2010                        eng d00aMultiple Origins of Elytral Reticulation Modifications in the West Palearctic Agabus bipustulatus Complex (Coleoptera, Dytiscidae)0 aMultiple Origins of Elytral Reticulation Modifications in the We  bPublic Library of SciencecFebruary  ae9034+0 v53 aThe Agabus bipustulatus complex includes one of Europe's most widely distributed and common diving beetles. This complex, which is known for its large morphological variation, has a complex demographic and altitudinal variation in elytral reticulation. The various depth of the reticulation imprint, both in smaller and larger meshes, results in both mat and shiny individuals, as well as intermediate forms. The West Palearctic lowland is inhabited by a sexually dimorphic form, with shiny males and mat females. In mountain regions, shiny individuals of both sexes are found intermixed with mat individuals or in pure populations in central and southern areas, whereas pure populations of mat individuals are exclusively found in the northern region at high altitude. Sexual selection is proposed as a driving force in shaping this variation. However, the occurrence of different types of reticulation in both sexes and disjunct geographical distribution patterns suggest an additional function of the reticulation. Here we investigate the phylogeographical history, genetic structure and reticulation variation of several named forms within the Agabus bipustulatus complex including A. nevadensis . The molecular analyses recognised several well-supported clades within the complex. Several of the named forms had two or more independent origins. Few south European populations were uniform in reticulation patterns, and the males were found to display large variation. Reticulation diversity and population genetic variability were clearly correlated to altitude, but no genetic differences were detected among populations with mixed or homogenous forms. Observed reduction in secondary reticulation in female and increased variance in male at high altitude in South Europe may be explained by the occurrence of an additional selective force, beside sexual selection. The combined effect of these selective processes is here demonstrated in an extreme case to generate isolation barriers between populations at high altitudes. Here we discuss this selective force in relation to thermal selection.10aevolution10ainsects10avenation10awings1 aDrotz, Marcus, K.1 aBrodin, Tomas1 aNilsson, Anders, N.  uhttp://dx.doi.org/10.1371/journal.pone.0009034