Entomologists from Russia and Germany have crossbred two closely related species of grasshoppers and received hybrids, whose songs are much more complicated and diverse than songs of both parent species. Particular song elements are inherited in different ways and depend on numerous genes. Evolutional background of two studied species might have been linked with sexual selection, based on females preferring males with most complicated and sophisticated courtship behavior.
The question of genesis mechanisms of reproductive isolation is one of the key issues of evolutional biology. When females of a population start choosing males with a certain characteristic, this can be a first step to formation of a new species, especially when sons inherit said characteristic from their fathers, and daughters inherit their mothers’ aptitude to choose partners with this certain characteristic.
Characteristics, which define male’s attractivity, are very often linked with his courtship behavior. Moreover, reproductive isolation of many insect species depends only on said behavioral patterns, thus in laboratory insects of different species are able to interbreed and give birth to alive and fertile hybrid sons and daughters, when they have no other choice.
Allied species of grasshoppers (Acridoidea), which differ in male mating songs and rarely cross in natural environment, are a perfect object for studying genetics of courtship behavior. Scientists from the Institute of Information Transfer Problems have chosen following grasshopper species for their research – Chorthippus albomarginatus and Chorthippus oschei – and published the results of several years of studying these insects in the last issue of Journal of Evolutionary Biology scientific magazine.
Research fellows have crossbred grasshoppers, caught in Russia and Germany (Ch. albomarginatus), Bulgaria and Ukraine (Ch. oschei), and then analyzed songs of hybrids. Grasshoppers sing by means of rubbing their hind legs, which have special rows of small knobs, and veins of wing cases. Hybrid songs appeared to be mosaic, consisting of elements of both parent songs. However, this song is not a simple mixture of two tunes, it often has new elements, lacking in parent sounds.
Hybrid males have more variable and diverse songs than their fathers – four measured characteristics out of seven exceed extreme values of parent species. Females of both species prefer songs of males of their own species, however, only Ch. oschei females were able to distinguish songs of hybrid males and males of their “own” species. Hybrid females are not so selective: they eagerly mate with males of both parent species, as well as hybrid males.
Authors of the research conclude that Ch. Oschei, having more complicated songs and weird leg strokes, has possibly separated from Ch. Albomarginatus as a result of sexual selection. It is not improbable that the reason was females, who preferred males with sophisticated courtship behaviour.
Source:
http://www.blackwell-synergy.com/
http://www.glaucus.org.uk
Kizilova Anna