Evolution of genes involved in feeding preference and metabolic processes in Calliphoridae (Diptera: Calyptratae).

BACKGROUND: The genotype-phenotype interactions among traits governing feeding preference are of fundamental importance to behavioral genetics and evolutionary biology. The genetic basis of behavioral traits has been explored in different taxa using different approaches. However, the complex nature of the genetic mechanisms undergirding behavior is poorly understood. Here, we present an evolutionary study of candidate genes related to parasitism in Calliphoridae (Diptera: Calyptratae). Closely related species in this family exhibit distinct larval feeding habits, most notably necro-saprophagy and obligate parasitism.

METHODS: To understand the genetic and molecular bases underlying these habits, expression levels of eight candidate genes for feeding behavior-Cyp6g2, foraging, glutamate dehydrogenase, Jonah65aiv, Malvolio, PGRP-SC2, RPS6-p70-protein kinase, and smooth-were measured in four species using qPCR. Moreover we used expression values and sequence information to reconstruct the relationship among species and the dN/dS rate to infer possible sites under selection.

RESULTS: For most candidate genes, no statistically significant differences were observed, indicating a high degree of conservation in expression. However, Malvolio was differentially expressed between habits. Evolutionary analyses based on transcript levels and nucleotide sequences of Malvolio coding region suggest that transcript levels were correlated to feeding habit preferences among species, although deviations under a strictly neutral model were also observed in statistical tests.

DISCUSSION: Malvolio was the only gene demonstrating a possible connection to feeding habit. Differences in gene expression may be involved in (or be a result of) the genetic regulation of Calliphoridae feeding habit. Our results are the first steps towards understanding the genetic basis and evolution of feeding behavior in Calliphoridae using a functional approach.