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Courtship Complexity and Selection for Cognitive Traits

schiz ornamentation

The wolf spider genus Schizocosa contains at least 23 species in North America and they are characterized by their great diversity of courtship displays and male morphologies (Hebets, Vink, Sullivan-Beckers, and Rosenthal 2013). In some species, the forelegs of males are pigmented and/or accentuated by brushes of setae (or hairs). In other species, males look nearly identical to the unornamented females (see photo above). Not only does foreleg ornamentation, a visual signal, differ between species, but the display itself also differs. In some species, the males use visual signals (e.g. leg waving) in addition to various seismic components (e.g. stridulation, drumming). In most of the species, males have a complex multimodal display that incorporates more than one of the visual or seismic components.

Previous experiments revealed that by attending to cues from females, males can adjust their behavior to optimize their displays and increase mating success (Sullivan-Beckers & Hebets 2011, 2014). However, these experiments were conducted with a rather unusual species for the genus, S. rovneri. Schizocosa rovneri males do not have a visual display or any foreleg ornamentation. In contrast to other species, these males use a unimodal seismic signal, which is strongly dependent on the males effectively positioning themselves in the environment to ensure transmission of this simple signal. This reliance on attention and responsiveness to female feedback cues could have driven positive selection on the cognitive skills of S. rovneri. In other words, these males with their unimodal seismic signals, which are fully dependent on the signaling substrate for transmission of the signal, should be more likely to use female seismic feedback to identify an effective signaling channel. In contrast, species that can use multiple communication channels have multiple options to increase attractiveness. Thus, I hypothesize that males of species using multi-modal, multi-component displays have had weaker selection for enhanced cognitive ability in the context of attending to and responding to female feedback cues. This hypothesis is being tested in a comparative framework by testing the ability to learn from female feedback for males with a range of ornamentation and display types. 

 

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