Meeting Abstract

110.2  Sunday, Jan. 6  Evolvability of the cichlid jaw: New insight into the genetic basis of phenotypic integration HU, Y.*; PARSONS, K.J.; ALBERTSON, R.C.; Univ. of Massachusetts; Univ. of Glasgow; Univ. of Massachusetts Yinan@cns.umass.edu

Phenotypic integration refers to the pattern and magnitude of covariation among a set of traits, and is thought to substantially influence evolvability. Theory predicts that relatively low levels of integration will facilitate evolution as it allows distinct anatomical units (i.e., modules) to evolve independently from each other. On the other hand, high levels of integration may constrain the rate and/or direction of evolution as it presets a pattern of correlation among traits. To evaluate the genetic basis of phenotypic integration and its role in evolutionary processes, we developed a new method that estimates an individual’s integration level as the relative contribution of each individual to a population’s integration level. We then applied this metric to the lower jaws of an F2 hybrid population derived from a cross between two Lake Malawi cichlid species with alternate feeding strategies in order to genetically map integration levels. Our analysis detected two QTLs and two epistatic interactions that potentially contribute to integration within the cichlid mandible. Notably, alleles from the phenotypically derived and ecologically specialized species, which has significantly higher level of integration than the more generalized species, increase integration level in the F2 population. Our results suggest that integration of the cichlid jaw has a tractable genetic basis. They are also consistent with the hypothesis that ecomorphological specialization may arise at the expense of evolvability (i.e., high integration), shedding new light on the mechanisms that both promote and limit craniofacial diversity within this group.