S. He, V. Robitzch, Jean‐Paul A. Hobbs, M.J. Travers, D. Lozano‐Cortés, M.L. Berumen, J.D. DiBattista
Ecology and Evolution, pp. 1-11, (2019)
Chromis, Connectivity, Coral reef fishes, Hybridization, Indo-West Pacific, Marine biogeography, Microsatellite, Mitochondrial DNA, Pomacentridae, Population genetics
Aim: To determine the impact of ecological and environmental histories on the evolution of coral reef damselfishes at two adjacent marine biogeographic suture zones.
Location: Indo‐West Pacific, notably including two suture zones: Socotra and
Christmas and Cocos/Keeling Islands.
Taxon: Chromis dimidiata, Chromis margaritifer, and Chromis fieldi.
Methods: We utilized a combination of nuclear and mitochondrial genetic markers in
addition to visual abundance survey data of these fishes.
Results: Despite genetic patterns consistent with incomplete lineage sorting and
relatively low genetic differentiation among the three studied Chromis species, there
is evidence of hybridization between C. margaritifer and C. fieldi at Christmas Island
based on molecular and visual identification. Introgression appears to be spreading
westwards to other C. fieldi populations based on COI haplotype comparison.
Moreover, the genetic distance between C. margaritifer and C. fieldi suggests that
Pleistocene sea‐level fluctuations may have contributed to allopatric divergence and
secondary contact between these two closely related species.
Main conclusions: Our study highlights that evolutionary processes in coral reef
fishes operate differently between suture zones, possibly due to different ecological
and environmental predispositions regulating secondary contact of sister species.
While secondary contact likely led to hybridization and introgression at Christmas
and Cocos/Keeling Islands, none of those processes seem present at Socotra for the
chocolate‐dipped damselfish. This difference is likely due to an environmental barrier
caused by hydrodynamic regimes in the Gulf of Aden.