Publication details

Terrestrial fishes: rivers are barriers to gene flow in annual fishes from the African savanna



Year of publication 2015
Type Article in Periodical
Magazine / Source Journal of Biogeography
MU Faculty or unit

Faculty of Science

Field Zoology
Keywords Genetic structure;geodispersal;Mozambique; Nothobranchius kadleci ; Nothobranchius kuhntae ; Nothobranchius pienaari ;phylogeography;population genetics;river morphology;vernal pool
Description Aim We compared the genetic variability and phylogeographical structure of three sympatric clades of annual killifishes (the Nothobranchius furzeri complex, N. orthonotus complex and N. rachovii complex) inhabiting annually desiccating savanna pools. Hypotheses on the mechanisms affecting intraspecific structure and speciation were tested. Location Temporary pools in Mozambique (Africa). Methods The study is based on spatially detailed samples covering the entire range of all three species complexes. A set of 12–13 microsatellites (1638 individuals, 96 populations) and cytochrome b sequences (463 fish, 152 populations) were used as genetic markers. Phylogenetic and population genetic approaches were used to describe the spatial genetic structure and to test the respective roles of river channels and river basins on diversification. Results Profound genetic differentiation among populations was evident; some populations located only a few kilometres apart were genetically very distinct, suggesting a significant role of genetic drift and low dispersal ability. Large rivers (Zambezi, Save, Limpopo) formed major barriers to gene flow, with minor differences among the three complexes. Further, the demographic expansion of previously isolated lineages was often limited by the river channel, and rivers were also confirmed as factors affecting speciation events. River basins and elevational gradient had a smaller, but non-negligible, role in population structuring. Main conclusions River channels are the main barriers to gene flow in Nothobranchius fishes. The study demonstrated low dispersal ability and congruence in the phylogeographical pattern of all three complexes. Cases where Nothobranchius appear to have crossed river channels result from the dynamics of river morphology rather than from rare dispersal events. This conclusion is supported by simultaneous crossing events across lineages. A further division, also consistent among the three complexes, was detected between drier inland and wetter coastal areas. The phylogeographical pattern of Nothobranchius is unique in that it combines features of both aquatic and terrestrial taxa.

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