Multiple Loci Control Eyespot Number Variation on the Hindwings of Bicyclus anynana Butterflies

Redundancy analysis, genome-wide association studies and the pigmentation of brown trout (Salmo trutta L.)

The association of molecular variants with phenotypic variation is a main issue in biology, often tackled with genome-wide association studies (GWAS). GWAS are challenging, with increasing, but still limited, use in evolutionary biology. We used redundancy analysis (RDA) as a complimentary ordination approach to single- and multitrait GWAS to explore the molecular basis of pigmentation variation in brown trout (Salmo trutta) belonging to wild populations impacted by hatchery fish. Based on 75,684 single nucleotide polymorphic (SNP) markers, RDA, single- and multitrait GWAS allowed the extraction of 337 independent colour patterning loci (CPLs) associated with trout pigmentation traits, such as the number of red and black spots on flanks. Collectively, these CPLs (i) mapped onto 35 out of 40 brown trout linkage groups indicating a polygenic genomic architecture of pigmentation, (ii) were found to be associated with 218 candidate genes, including 197 genes formerly mentioned in the literature associated to skin pigmentation, skin patterning, differentiation or structure notably in a close relative, the rainbow trout (Onchorhynchus mykiss), and (iii) related to functions relevant to pigmentation variation (e.g., calcium- and ion-binding, cell adhesion). Annotated CPLs include genes with well-known pigmentation effects (e.g., PMEL, SLC45A2, SOX10), but also markers associated with genes formerly found expressed in rainbow or brown trout skins. RDA was also shown to be useful to investigate management issues, especially the dynamics of trout pigmentation submitted to several generations of hatchery introgression.

Miocene Climate and Habitat Change Drove Diversification in Bicyclus, Africa's Largest Radiation of Satyrine Butterflies

Compared to other regions, the drivers of diversification in Africa are poorly understood. We studied a radiation of insects with over 100 species occurring in a wide range of habitats across the Afrotropics to investigate the fundamental evolutionary processes and geological events that generate and maintain patterns of species richness on the continent. By investigating the evolutionary history of Bicyclus butterflies within a phylogenetic framework, we inferred the group's origin at the Oligo-Miocene boundary from ancestors in the Congolian rainforests of central Africa. Abrupt climatic fluctuations during the Miocene (ca. 19-17 Ma) likely fragmented ancestral populations, resulting in at least eight early-divergent lineages. Only one of these lineages appears to have diversified during the drastic climate and biome changes of the early Miocene, radiating into the largest group of extant species. The other seven lineages diversified in forest ecosystems during the late Miocene and Pleistocene when climatic conditions were more favourable-warmer and wetter. Our results suggest changing Neogene climate, uplift of eastern African orogens, and biotic interactions might have had different effects on the various subclades of Bicyclus, producing one of the most spectacular butterfly radiations in Africa.

Eco-evo-devo advances with butterfly eyespots

Eyespots on the wings of different nymphalid butterflies have become valued models in eco-evo-devo. They are ecologically significant, evolutionarily diverse, and developmentally tractable. Their study has provided valuable insight about the genetic and developmental basis of inter-specific diversity and intra-specific variation, as well as into other key themes in evo-evo-devo: evolutionary novelty, developmental constraints, and phenotypic plasticity. Here we provide an overview of eco-evo-devo studies of butterfly eyespots, highlighting previous reviews, and focusing on both the most recent advances and the open questions expected to be solved in the future.