Chromosomal rearrangements (e.g., fusions/fissions) have the potential to drive speciation. However, their accumulation in a population is generally viewed as unlikely, because chromosomal heterozygosity should lead to meiotic problems and aneuploid gametes. Canonical meiosis involves segregation of homologous chromosomes in meiosis I and sister chromatid segregation during meiosis II. In organisms with holocentric chromosomes, which are characterized by kinetic activity distributed along almost the entire chromosome length, this order may be inverted depending on their metaphase I orientation. Here we analyzed the evolutionary role of this intrinsic versatility of holocentric chromosomes, which is not available to monocentric ones, by studying F1 to F4 hybrids between two chromosomal races of the Wood White butterfly (Leptidea sinapis), separated by at least 24 chromosomal fusions/fissions. We found that these chromosomal rearrangements resulted in multiple meiotic multivalents, and, contrary to the theoretical prediction, the hybrids displayed relatively high reproductive fitness (42% of that of the control lines) and regular behavior of meiotic chromosomes. In the hybrids, we also discovered inverted meiosis, in which the first and critical stage of chromosome number reduction was replaced by the less risky stage of sister chromatid separation. We hypothesize that the ability to invert the order of the main meiotic events facilitates proper chromosome segregation and hence rescues fertility and viability in chromosomal hybrids, potentially promoting dynamic karyotype evolution and chromosomal speciation.

BackgroundPredators preferentially attack vital body parts to avoid prey escape. Consequently, prey adaptations that make predators attack less crucial body parts are expected to evolve. Marginal eyespots on butterfly wings have long been thought to have this deflective, but hitherto undemonstrated function.Methodology/Principal FindingsHere we report that a butterfly, Lopinga achine, with broad-spectrum reflective white scales in its marginal eyespot pupils deceives a generalist avian predator, the blue tit, to attack the marginal eyespots, but only under particular conditions—in our experiments, low light intensities with a prominent UV component. Under high light intensity conditions with a similar UV component, and at low light intensities without UV, blue tits directed attacks towards the butterfly head.Conclusions/SignificanceIn nature, birds typically forage intensively at early dawn, when the light environment shifts to shorter wavelengths, and the contrast between the eyespot pupils and the background increases. Among butterflies, deflecting attacks is likely to be particularly important at dawn when low ambient temperatures make escape by flight impossible, and when insectivorous birds typically initiate another day's search for food. Our finding that the deflective function of eyespots is highly dependent on the ambient light environment helps explain why previous attempts have provided little support for the deflective role of marginal eyespots, and we hypothesize that the mechanism that we have discovered in our experiments in a laboratory setting may function also in nature when birds forage on resting butterflies under low light intensities.

While focus in oil-producing microalgae is normally on nutrient deficiency, we addressed the seasonal variations of lipid content and composition in large-scale cultivation. Lipid content, fatty acid profiles and mono-di-and triglycerides (MAGs, DAGs, and TAGs) were analyzed during May 2007-May 2009 in Nannochloropsis oculata grown outdoors in closed vertical flat panels photobioreactors. Total lipids (TL) ranged from 11% of dry weight (DW) in winter to 30% of DW in autumn. 50% of the variation in TL could be explained by light and temperature. As the highest lipid content was recorded during autumn indicating an optimal, non-linear, response to light and temperature we hypothesize that enhanced thylakoid stacking under reduced light conditions resulted in more structural lipids, concomitantly with the increase in glycerides due to released photo-oxidative stress. The relative amount of monounsaturated fatty acids (MUFA) increased during autumn. This suggested a synthesis, either of structural fatty acids as MUFA, or a relative increase of C16:1 incorporated into TAGs and DAGs. Our results emphasize the significant role of environmental conditions governing lipid content and OPEN ACCESSEnergies 2012, 5 1578 composition in microalgae that have to be considered for correct estimation of algal oil yields in biodiesel production.

The sister species Leptidea reali and L. sinapis have partitioned their niches differently in different parts of their sympatric distribution. In Spain and France L. sinapis is a widespread generalist whereas L. reali is specialized on high altitude open areas. Interestingly, the reverse is true in Ireland and the Czech Republic where L. reali is widespread and L. sinapis specialized on meadows. In Sweden, L. reali is a habitat specialist confined to meadows, whereas L. sinapis is a habitat generalist also inhabiting forests. Ultimately, the geographic mosaic of niche separation is the result of local processes in each contact zone or a secondary effect of the host plant distribution, if L. sinapis and L. reali prefer different legume host plants. Hence, in Sweden L. sinapis might utilize the forest habitat either due to a wider habitat preference or due to a wider host plant preference than L. reali. Studies of wild butterflies showed that L. sinapis laid 26% of their eggs on forest-associated legumes compared to 6% in L. reali, although laboratory experiments showed that both species had virtually identical host plant preferences strongly preferring the meadow-associated legume Lathyrus pratensis. Furthermore, flight duration tests in a variety of temperatures demonstrated a between-species difference; L. sinapis females reached their flight optimum at a lower temperature than L. reali females. The lower L. sinapis flight temperature optimum is most probably a secondary effect due to habitat-specific selection, and therefore a consequence rather than the cause of the habitat partitioning. The finding that habitat choice precedes host plant choice suggests that the European geographic mosaic of niche separation, with L. sinapis and L. reali shifting habitat specialist/generalist roles, is not caused by rigid between-species differences in a related niche parameter, but instead is a result of local processes within each secondary contact zone.Co-evolving with angiosperms, phytophagous insects have radiated into one of the most diverse functional groups on earth. Among lepidopterans alone, there are at least 150 000 described species (Kristensen 1999), and when adding herbivorous beetles, hemipterans, heteropterans, hymenopterans and other representatives of herbivorous insects, the functional group constitutes more than one fourth of the total number of species on earth (Grimaldi and Engel 2005).The traditional view of speciation, being a large scale passive process of populations becoming genetically isolated by geographic barriers, has recently been challenged as theoretical models of sympatric speciation have become more comprehensive and sophisticated (Dieckmann and Doebeli 1999, van Doorn et al. 2004) than the pioneering models of speciation without geographic isolation proposed in the 1960s (Maynard-Smith 1966). Many theoretical and empirical examples of adaptive speciation have concerned herbivorous insects, and the occurrence of host plant shifts (Berlocher and Feder 2002, Bush andButlin 2004), and both t...

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