BUCKLEY, D.*; BONETT, R. M.; WAKE, M. H.; Univ. of California, Berkeley; Univ. of California, Berkeley; Univ. of California, Berkeley: Evolution of Viviparity and Speciation Patterns in Vertebrates

The evolution of viviparity (here defined as development through metamorphosis of offspring within the mother with maternal nourishment) in vertebrate lineages has been traditionally studied from ecological, physiological, and developmental points of view. More recently, it has been argued that the evolution of viviparity can be better understood under a tug-of-war scenario between mothers and their developing offspring. Hypotheses such as the �viviparity-driven conflict�, �parent-offspring conflict�, or �genetic incompatibility avoidance� stress the conflict of interest between parental investment and offspring demand in the evolution of this derived reproductive strategy. These hypotheses predict, among other things, that the tug-of-war conflict will rapidly select for postzygotic isolation mechanisms, leading to an increase of speciation rates and a decrease of hybridization in viviparous lineages. We gather data on recently published vertebrate phylogenetic hypotheses to compare rates and modes of speciation and levels of hybridization between pairs of viviparous and non-viviparous sister groups. We analyze those data in a phylogenetic framework to test for correlation of traits or morphological and physiological constraint among lineages, shedding more light on the features that are related to the evolution of viviparity in the different vertebrate clades. We argue that the study of the evolution of an adaptive trait such as reproductive modes may be improved when approached from a historical (phylogenetic) and internalist (mechanistic) point of view rather than from a purely externalist or adaptationist point of view.