Abstract
Cuticular hydrocarbons (CHCs) are important in mate choice in many insects, and may be used for species recognition if CHC profiles differ between potentially hybridizing species. In the sibling field cricket species Gryllus campestris and G. bimaculatus, females of G. bimaculatus are tolerant towards G. campestris males and can mate with them. However, G. campestris females are highly aggressive towards heterospecific G. bimaculatus males, and matings between them never happen. We examined whether cricket females might use CHCs to determine the species identity of their potential mates. We firstly analyzed the cuticular chemical profile by gas chromatography and mass spectrometry to assess the potential of CHCs to be used for species recognition in these crickets. We then manipulated females’ ability to detect chemical cues by carrying out chemical ablation of the antennae, and measured changes in aggressive responses to heterospecific males. We show that there are significant interspecies differences in CHC expression for both sexes, and that females with chemically ablated antennae reduce aggressive behavior towards heterospecific males. Our findings support the prediction that cuticular semiochemicals can play a key role in reproductive isolation between closely related insect species.
Highlights
Mate choice decisions are based upon the traits of potential partners
Based on values of diagnostic power, we found a subset (48%) of the cuticular hydrocarbons (CHCs) to be >2.17 times more variable between species than within species
We show that there are significant species differences in CHC expression for both sexes, and that species identity could be determined on the basis of an individual’s CHC profile
Summary
If gene flow is restricted between two populations, mating traits and preferences may diverge (Panhuis et al, 2001). Individuals from divergent populations may no longer be recognized as potential mates, at which point speciation has occurred (Mayr, 1942). Information about the traits used in species recognition can be received through a range of sensory modalities, for example using auditory, visual or tactile cues, likely in combination (Hebets and Papaj, 2005). Chemoreception (comprised of olfactory and gustatory systems) is thought to be the most ubiquitous of the sensory modalities (Ache and Young, 2005), and is used for species recognition across a broad range of taxa (reviewed by Smadja and Butlin, 2008). Olfactory signals found in urine are used to discriminate between individuals, with Mus musculus musculus preferring the urine of conspecifics to urine
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