Regulatory and evolutionary impact of DNA methylation in two songbird species and their naturally occurring F hybrids.

Background: Regulation of transcription by DNA methylation in 5'-CpG-3' context is a widespread mechanism allowing differential expression of genetically identical cells to persist throughout development. Consequently, differences in DNA methylation can reinforce variation in gene expression among cells, tissues, populations, and species. Despite a surge in studies on DNA methylation, we know little about the importance of DNA methylation in population differentiation and speciation.

Meiotic drive against chromosome fusions in butterfly hybrids.

Species frequently differ in the number and structure of chromosomes they harbor, but individuals that are heterozygous for chromosomal rearrangements may suffer from reduced fitness. Chromosomal rearrangements like fissions and fusions can hence serve as a mechanism for speciation between incipient lineages, but their evolution poses a paradox. How can rearrangements get fixed between populations if heterozygotes have reduced fitness? One solution is that this process predominantly occurs in small and isolated populations, where genetic drift can override natural selection.

Base Composition, Codon Usage, and Patterns of Gene Sequence Evolution in Butterflies.

Coding sequence evolution is influenced by both natural selection and neutral evolutionary forces. In many species, the effects of mutation bias, codon usage, and GC-biased gene conversion (gBGC) on gene sequence evolution have not been detailed. Quantification of how these forces shape substitution patterns is therefore necessary to understand the strength and direction of natural selection.

Nascent evolution of recombination rate differences as a consequence of chromosomal rearrangements.

Reshuffling of genetic variation occurs both by independent assortment of chromosomes and by homologous recombination. Such reshuffling can generate novel allele combinations and break linkage between advantageous and deleterious variants which increases both the potential and the efficacy of natural selection. Here we used high-density linkage maps to characterize global and regional recombination rate variation in two populations of the wood white butterfly (Leptidea sinapis) that differ considerably in their karyotype as a consequence of at least 27 chromosome fissions and fusions.

Environmental stress during larval development induces DNA methylation shifts in the migratory painted lady butterfly (Vanessa cardui).

Seasonal environmental fluctuations provide formidable challenges for living organisms, especially small ectotherms such as butterflies. A common strategy to cope with harsh environments is to enter diapause, but some species avoid unsuitable conditions by migrating. Despite a growing understanding of migration in the life cycles of some butterfly species, it remains unknown how individuals register and store environmental cues to determine whether and where to migrate.

Larger genomes show improved buffering of adult fitness against environmental stress in seed beetles.

Our general understanding of the evolution of genome size (GS) is incomplete, and it has long been clear that GS does not reflect organismal complexity. Here, we assess the hypothesis that larger genomes may allow organisms to better cope with environmental variation. It is, for example, possible that genome expansion due to proliferation of transposable elements or gene duplications may affect the ability to regulate and fine-tune transcriptional profiles.

The Effects of GC-Biased Gene Conversion on Patterns of Genetic Diversity among and across Butterfly Genomes.

Recombination reshuffles the alleles of a population through crossover and gene conversion. These mechanisms have considerable consequences on the evolution and maintenance of genetic diversity. Crossover, for example, can increase genetic diversity by breaking the linkage between selected and nearby neutral variants.

The Genome of Blue-Capped Cordon-Bleu Uncovers Hidden Diversity of LTR Retrotransposons in Zebra Finch.

Avian genomes have perplexed researchers by being conservative in both size and rearrangements, while simultaneously holding the blueprints for a massive species radiation during the last 65 million years (My). Transposable elements (TEs) in bird genomes are relatively scarce but have been implicated as important hotspots for chromosomal inversions. In zebra finch (), long terminal repeat (LTR) retrotransposons have proliferated and are positively associated with chromosomal breakpoint regions.