Meeting Abstract
Mouthbrooding is a parental care strategy in which the eggs or larvae are incubated in the mouth and has been hypothesized to have a negative influence on craniofacial diversity in multiple lineages of teleost fishes. We examined the impact of mouthbrooding on the craniofacial morphology of the cichlid fishes of Lake Tanganyika in E. Africa. This radiation consists of 200 species with a deep phylogenetic split between a clade of substrate-spawning cichlids and multiple mouthbrooding cichlid lineages. We used geometric morphometric methods and the TPS family of programs to digitize a set of 25 sliding semi-landmarks along the outline of the head in lateral photographs of Tanganyikan cichlid species. Relative warps analysis was performed and the broken stick criterion used to retain axes that explained more variation than expected by chance. We retained three axes which explained 88% of the total variation. Head elongation vs. deepening was the major axis of diversity accounting for 60% of variation. Mouth angle and mouth size accounted for the other two axes and explained 16% and 12% of the variation respectively. Morphospace occupation was determined using Morphospace Disparity Analysis to examine the occupation of both mouthbrooding and non-mouthbrooding sister lineages using 10,000 bootstrapped samples to calculate the mean Euclidean pairwise distance. We find that mouthbrooders exhibit a significantly higher mean euclidean pairwise distance and are 2.4 times more diverse than non-mouthbrooders. Our results demonstrate that contrary to previous interpretations mouthbrooding has not impeded craniofacial diversity in Tanganyikan cichlids, and may indirectly enhance diversification of mouthbrooding species because it allows them to occupy habitats not suitable for substrate brooding.
