Cichlid Evolution: Lessons in Diversification

Abstract

This is the second special issue on cichlid evolution hosted by the International Journal of Evolutionary Biology. Once more, we are overwhelmed by the vivid responses to our call for contributions, and thank the authors for their great work. The thirteen papers in this issue, including two reviews, span geographically from Africa to South America and address a wide variety of evolutionary topics including speciation and hybridization, phenotype evolution, and reproductive behaviour. Papers are summarized below in the order in which they appear in this special issue. Linking Diversification to the Physical Environment. The East African cichlid radiations represent the most spectacular vertebrate radiations known to date, and a multitude of studies have sought to elucidate the phylogenetic relation-ships among extant East African cichlid lineages. The East African rift valley is also extremely dynamic from a geological perspective, and numerous studies have aimed at clarifying the geologic, hydrologic, and climatic history of this region. However, while these fields have enormous potential to inform one another, a uniting synthesis combining evidence from studies on geology/hydrology/climatology and cichlid phylogeny/phylogeography has been lacking. In their review " The impact of the geologic history and paleoclimate on the diversification of East African cichlids, " P. D. Danley et al. provide an up-to-date synthesis of the geologic history and paleoclimate of the East African Great Lakes (and surround-ing water bodies) and the evolution of the region's endemic cichlid species assemblages. They discuss how tectonic pro-cesses and climatic changes changed the hydrological systems in East Africa and affected the diversification of cichlid fishes.