Reconciling fossils and molecules: Cenozoic divergence of cichlid fishes and the biogeography of Madagascar

Abstract

Aim The biogeographical origins of the extant vertebrates endemic to Madagascar are largely unsolved, but have often been related to vicariance in the context of fragmentation of the supercontinent Gondwana in the Mesozoic. Such hypotheses are especially appealing in the case of cichlid ®shes, which show phylogenetic relationships re¯ecting the temporal successions of the breakup of Gondwana. We used molecular clock data to test this assumption.Location Fragments of the 16S rRNA gene and of the nuclear Tmo-4C4 locus, partly obtained from Genbank from South American, African, Malagasy and Indian cichlids were analysed.Methods Based on monophyletic cichlid radiations in African lakes, we calibrated a molecular clock. The obtained rates were used to estimate the age of divergence of the major cichlid clades. ResultsThe results agreed better with a Cenozoic than with a Mesozoic divergence, and were in accordance with the fossil record. Sequence divergences of the 16S and 12S rRNA genes of most lineages of Malagasy terrestrial and freshwater vertebrates from their non-Malagasy sister groups were below saturation and many were relatively similar to those of cichlids.Main conclusions A Cenozoic dispersal from continental landmasses may explain the origin of most extant Malagasy vertebrate groups better than a Jurassic/Cretaceous vicariance.

Age of Cichlids: New Dates for Ancient Lake Fish Radiations

“…First, we employed 3 Gondwanan fragmentation events as calibration points. Following Vences et al (2001), we used the separation of East and West Gondwana 121-165 MYA, the separation of Africa from South America 86-101 MYA, and the separation of Madagascar and India 63-88 MYA. Second, we employed 8 cichlid fossil calibrations (table 1 and fig.…”

“…Moreover, few spiny-rayed teleost fish (Acanthomorpha) fossils are known between their first appearances in the Late Cretaceous and the Late Palaeocene/ Early Eocene when they became common in the fossil record, exhibiting extensive diversity in morphology (Patterson 1993;Chakrabarty 2004). If the earliest cichlid fossils are approximately coincident with the origin of the family, their present distribution must be explained by intercontinental marine dispersal and not vicariance during the breakup of Gondwana (Vences et al 2001).…”

“…Addressing these questions is of fundamental importance for understanding the causes and dynamics of adaptive radiation in this textbook evolutionary system. Until now, attempts to date African cichlid evolutionary events have been predominantly based on rates of molecular evolution extrapolated from mammals (Meyer et al 1990), assumptions of monophyletic origins of cichlid radiations within lake catchments of known age (Vences et al 2001), or assumptions of lineage splitting being synchronized with lake-level changes (Sturmbauer et al 2001;Verheyen et al 2003). Although these published date estimates are informative, they do have the potential to be misleading because of inconsistencies in rates of molecular evolution among evolutionary lineages, uncertainties over the timing, extent and biological implications of lake-level changes, and the possibility that lake radiations may have been founded by multiple colonizers.…”

Multiple colonization of Madagascar and Socotra by colubrid snakes: evidence from nuclear and mitochondrial gene phylogenies

“…An origin by ancient vicariance has been invoked for Madagascar's freshwater fishes and frogs (Richards & Moore 1996;Murphy & Collier 1997;Farias et al 2001; but see Vences et al 2001). By contrast, dispersalist explanations prevail for mammals (e.g.…”

Independent Gene Phylogenies and Morphology Demonstrate a Malagasy Origin for a Wide-Ranging Group of Swallowtail Butterflies

“…For example, several Malagasy birds show clear affinities with Oriental groups that are unknown in Africa (Dorst 1972). The presence of some lineages of plants and animals in Madagascar may be explained by Cretaceous dispersals to the island from India or South Africa, and floral and faunal exchange with the remains of Gondwana via Antarctica during the time of the initial radiation of the angiosperms (Koechlin 1972;Schatz 1996;Vences et al 2001). This scenario may account for the evolution of seven endemic plant families and three recently extinct ratite species (Cooper et al 2001).…”