Evolution of displays in Galápagos lava lizards: comparative analyses of signallers and robot playbacks to receivers. (November 2015)

• Record Type: Journal Article
• Authors: Clark, David L.; Macedonia, Joseph M.; Rowe, John W.; Stuart, Mark A.; Kemp, Darrell J.; Ord, Terry J.
• Is Part Of: Animal behaviour. Volume 109(2015) Supplement
• Page Start: 33
• Page End: 44
• Publication Date: 2015-11
• Subjects: communication -- Galápagos Islands -- lizard robot -- Microlophus -- push-up display -- sexual selection -- speciation; Animal behavior -- Periodicals; 591.5
• DOI: 10.1016/j.anbehav.2015.08.002
• Languages: English
• ISSNs: 0003-3472

Abstract

Abstract : Differentiation in the structure of animal signals and displays among closely related species has intrigued biologists for centuries. Such divergence is often attributed to behavioural premating isolation, where sexual selection has favoured species recognition in environments containing sympatric congeners. However, in some cases closely related taxa have undergone speciation and display differentiation in isolation, in the apparent absence of benefits afforded by species recognition. Such is the case for the lava lizards ( Microlophus spp.) endemic to the Galápagos Islands, where no two species overlap in distribution and all are thought to have evolved in allopatry from congeners. To test alternative evolutionary models, we used several phylogenetic comparative methods to assess how Microlophus displays have evolved. Results showed some potential for the influence of genetic drift, but little evidence of sexual selection (via male–male competition) or colonization history on the way displays have diverged among taxa. We then used lizard robots to test whether two representative Galápagos lava lizard species, Microlophus grayii and Microlophus indefatigabilis, would respond preferentially to a robot performing conspecific displays over those of the congener. We predicted that, in the absence of reinforcing selection, neither species would show a preference for conspecific displays. Results were mixed: whereas M. grayii showed no discrimination of conspecific over heterospecific displays, male M. indefatigabilis showed significantly stronger responses to their own displays than to those of the heterospecific. We then conducted the same experiment with a mainland congener, Microlophus occipitalis, to provide a broader view of potential responses across the group. Results revealed significant discrimination against heterospecific displays. We discuss our findings in light of hypotheses of signal differentiation, and suggest alternative interpretations for recognition of conspecific displays in species that are thought to have evolved in isolation. Highlights: We examined whether Microlophus sp. evolving in allopatry show relaxed species recognition. Analyses of male displays showed potential for drift, but little evidence of male sexual selection. One of two Galápagos species and one mainland congener showed species discrimination. Species recognition thus may not conform to expectations based on sympatry or allopatry alone. We discuss alternative interpretations of preference for conspecific displays in Microlophus .