Light environment influences mating behaviours during the early stages of divergence in tropical butterflies

Speciation is facilitated when traits under divergent selection also act as mating cues. Fluctuations in sensory conditions can alter signal perception independently of adaptation to the broader sensory environment, but how this fine-scale variation may constrain or promote behavioural isolation has received little attention. The warning patterns of Heliconius butterflies are under selection for aposematism and act as mating cues. Using computer vision, we extracted behavioural data from 1481 h of video footage, for 387 individuals. We show that the putative hybrid species H. heurippa and its close relative H. timareta linaresi differ in their response to divergent warning patterns, but that these differences are strengthened with increased local illuminance. Trials with live individuals reveal low-level assortative mating that is sufficiently explained by differences in visual attraction. Finally, results from hybrid butterflies are consistent with linkage between a major warning pattern gene and the corresponding behaviour, though the differences in behaviour we observe are unlikely to cause rapid reproductive isolation as predicted under a model of hybrid trait speciation. Overall, our results reveal that the contribution of ecological mating cues to reproductive isolation may depend on the immediate sensory conditions during which they are displayed to conspecifics.

Light environment influences mating behaviours during the early stages of divergence in tropical butterflies

ABSTRACTSpecies divergence is facilitated when traits under divergent selection also act as mating cues. Fluctuations in sensory conditions can alter signal perception independently of adaptation to contrasting sensory environments, but how this fine scale variation affects behavioural isolation has received less attention, especially in terrestrial organisms. The warning patterns of Heliconius butterflies are under selection for aposematism and act as mating cues. Using computer vision, we extracted behavioural data from 1481 hours of video footage for 387 individuals. We show that the putative hybrid species H. heurippa and its close relative H. timareta linaresi differ in their response to divergent warning patterns, and that these differences are strengthened with increased local illuminance. Trials with live individuals reveal low-level assortative mating that are sufficiently explained by differences in visual attraction. Finally, results from hybrid butterflies are consistent with linkage between a major warning pattern gene and the corresponding behaviour, though the differences in behaviour we observe are unlikely to cause rapid reproductive isolation as predicted under a model of hybrid trait speciation. Overall, our results highlight that the role of ecological mating cues for behavioural isolation may depend on the immediate sensory conditions during which they are displayed to conspecifics.

Love at first flight: Wing interference patterns are species-specific and sexually dimorphic in blowflies (Diptera: Calliphoridae)

Wing interference patterns (WIPs) are stable structural colours displayed on insect wings which are only visible at specific viewing geometries and against certain backgrounds. These patterns are widespread among flies and wasps, and growing evidence suggests that they may function as species- and sex-specific mating cues in a range of taxa. As such, it is expected that WIPs should differ between species and show clear sexual dimorphisms. However, the true extent to which WIPs vary between species, sexes, and individuals is currently unclear, as previous studies have only taken a qualitative approach, without considering how WIPs might be perceived by the insect. Here, we perform the first quantitative analysis of inter- and intra-specific variation in WIPs across seven Australian species of the blowfly genus Chrysomya. Using multispectral digital imaging and a tentative model of blowfly colour vision, we provide quantitative evidence that WIPs are species-specific, highlight that the extent of divergence is greater in males than in females, and demonstrate sexual dimorphisms in several species. These data provide evidence that WIPs have diversified substantially in blowflies and suggests that sexual selection may have played a role in this process.

Rhyacophila dandaganu, a new caddisfly from the southern Cumberland Plateau (USA) (Trichoptera: Rhyacophilidae)

We describe a new species in the caddisfly genus Rhyacophila (Trichoptera: Rhyacophilidae) from the southern Cumberland Plateau of the United States. Rhyacophila dandaganu n. sp. is placed in the Rhyacophila lobifera Group from North America, the second known species in this group. The new species is distinguished from Rhyacophila lobifera Betten, 1934 by the shape and dimensions of several genitalic structures, as well as the absence of parameres accompanying the endotheca and the characteristic shape of the tenth segment and phallicata. We discuss the geographic range of these two species and the questions raised by the curious (apparent) lack of sympatric populations. We discuss some testable hypotheses that might determine how populations of R. dandaganu n. sp. and R. lobifera could maintain phenotypic distinctiveness, in the absence of obvious geographic barriers to gene flow, including behavioral, chemical or tactile mating cues.

Genetic dissection of assortative mating behavior

The evolution of new species is made easier when traits under divergent ecological selection are also mating cues. Such ecological mating cues are now considered more common than previously thought, but we still know little about the genetic changes underlying their evolution, or more generally about the genetic basis for assortative mating behaviors. The warning patterns of Heliconius melpomene and H. cydno are under disruptive selection due to increased predation of non-mimetic hybrids, and are used during mate recognition. We carried out a genome-wide quantitative trait locus (QTL) analysis of preference behaviors between these species and showed that divergent male preference has a simple genetic basis. Three QTLs each explain a large proportion of the differences in preference behavior observed between the parental species. Two of these QTLs are on chromosomes with major color pattern genes, including one that is tightly associated with the gene optix. Different loci influence different aspects of attraction, suggesting that behavioral isolation in Heliconius involves the evolution of independently segregating modules, similar to those for the corresponding wing pattern cues. Hybridization and subsequent sharing of wing pattern loci has played an important role during adaptation and speciation in Heliconius butterflies. The existence of large effect preference loci could similarly assist the evolution of novel behavioral phenotypes through recombination and introgression, and should facilitate rapid speciation.

Promoting sustainability in a college café by opposite-sex cashiers

Purpose People engage in green consumption for many reasons, both conscious and unconscious. This paper aims to draw on evolutionary psychology to propose that hard-wired mating strategies encourage both men and women to increase their green consumption in the presence of members of the opposite sex. Design/methodology/approach Observations were conducted on 324 students who purchased cold drinks in disposable cups from a college café. The students were offered the choice of adding 20 cents to their purchase for a bio-degradable cup. Findings Overall, 160 students agreed to pay the premium for a bio-degradable cup, with green purchases 46 per cent higher among women and 61 per cent higher among men when facing a cashier of the opposite sex. Originality/value The findings suggest that the activation of mating cues prompts students to display prosocial, altruistic behavior and/or to engage in conspicuous consumption (i.e. agreeing to pay more for the sustainable product). The study was conducted in the field using naïve participants and demonstrates the application of evolutionary psychology to green marketing. It also adds to what is a surprisingly small literature on the effect of employee–customer gender mismatch.