The Genetics of a Behavioral Speciation Phenotype in an Island System

Abstract

Mating behavior divergence can make significant contributions to reproductive isolation and speciation in various biogeographic contexts. However, whether the genetic architecture underlying mating behavior divergence is related to the biogeographic history and the tempo and mode of speciation remains poorly understood. Here, we use quantitative trait locus (QTL) mapping to infer the number, distribution, and effect size of mating song rhythm variations in the crickets Laupala eukolea and Laupala cerasina, which occur on different islands (Maui and Hawaii). We then compare these results with a similar study of an independently evolving species pair that diverged within the same island. Finally, we annotate the L. cerasina transcriptome and test whether the QTL fall in functionally enriched genomic regions. We document a polygenic architecture behind the song rhythm divergence in the inter-island species pair that is remarkably similar to that previously found for an intra-island species pair in the same genus. Importantly, the QTL regions were significantly enriched for potential homologs of the genes involved in pathways that may be modulating the cricket song rhythm. These clusters of loci could constrain the spatial genomic distribution of the genetic variation underlying the cricket song variation and harbor several candidate genes that merit further study.

Insights into the genomic evolution of insects from cricket genomes

“…This possibility is consistent with the results of multiple quantitative trait locus (QTL) studies done in cricket species from the genus Laupala, which identified genomic regions associated with mating song rhythm variations and female acoustic preference 71 . The 179 scaffolds that the authors reported being within one logarithm of the odds (LOD) of the seven QTL peaks, contained five pickpocket genes, three of them from class V and two from class IV.…”

Physical linkage and mate preference generate linkage disequilibrium for behavioral isolation in two parapatric crickets

“…; Blankers et al. ). The fact that only carrier frequency and not pulse rate has X‐linked QTL is particularly puzzling, especially in the light of strong signatures of X‐linkage for pulse rate in reciprocal interspecific hybrids.…”

Predictability in the evolution of Orthopteran cardenolide insensitivity

“…In Drosophila melanogaster , expression of ATPα2 is limited to larval imaginal discs and adult male testes and accessory glands; RNAi and P-element knock-outs of the gene are homozygous viable but male-sterile (http://www.flybase.org/reports/FBgn0267363). Furthermore, we failed to recover an ortholog of ATPα2 from the Locusta migratoria genome assembly [47], and several other Orthopteran assemblies [48,49], suggesting that the ATPα1/α2 duplication may have arisen after the split of Orthopterans from the other insects we have surveyed ( Figure 1A ). We thus decided to focus on ATPα1, which shows clear orthology across taxa and a strong correlation between evolution at known cardenolide-sensitivity sites in the protein and specialisation on cardenolide-containing Apocynaceae plants [30].…”