Pre-Mating Reproductive Isolation in Tiger Beetles (Carabidae: Cicindelinae): an Examination of the Role of Visual and Morphological Feedback

Abstract

The biological species concept depends on mechanisms isolating reproduction to taxonomically define a species and to explain the disadvantages, and subsequent lack, of hybridization. In co-occurring tiger beetles (Carabidae: Cicindelinae), these between-species barriers are not readily apparent. To understand the characteristics potentially responsible for this isolation, we conducted behavioral and morphological experiments with two pairs of tiger beetle species. Choice trials showed males use visual cues to trigger the pursuit of potential mates and prefer females who appear similar in color. Geometric morphometric techniques allowed us to quantify shape differences in the mandibles of all four species. Previously, it was proposed that the mandible-coupling sulcus pairing acted as a lock-and-key mechanism to provide feedback necessary for species recognition. Our results, however, suggest that although there are significant differences in shape, these differences do not provide any feedback to the male or enhance his ability to retain his grasp on the female. Taken together, these findings suggest that vision, rather than the traditional mandibular lock-and-key hypothesis, may play a key role in reproductive isolation for co-occurring tiger beetle species.