River capture, range expansion, and cladogenesis: The genetic signature of freshwater vicariance
Burridge, CP and Craw, D and Waters, JM, River capture, range expansion, and cladogenesis: The genetic signature of freshwater vicariance, Evolution: International Journal of Organic Evolution, 60, (5) pp. 1038-1049. ISSN 0014-3820 (2006) [Refereed Article]
River capture is potentially a key geomorphological driver of range expansion and cladogenesis in fresh-
water-limited taxa. While previous studies of freshwater ﬁsh, in particular, have indicated strong relationships between
historical river connections and phylogeographic pattern, their analyses have been restricted to single taxa and geo-
logical hypotheses were typically constructed a posteriori. Here we assess the broader signiﬁcance of river capture
among taxa by testing multiple species for the genetic signature of a recent river capture event in New Zealand.
During the Quaternary an upper tributary of the Clarence River system was diverted into the headwaters of the Wairau
River catchment. Mitochondrial DNA (control region and cytochrome b) sequencing of two native galaxiid ﬁshes
(Galaxias vulgaris and Galaxias divergens) supports headwater exchange: populations from the Clarence and Wairau
Rivers are closely related sister-groups, whereas samples from the geographically intermediate Awatere River are
genetically divergent. The upland bully Gobiomorphus breviceps (Eleotridae), in contrast, lacks a genetic signature
of the capture event. We hypothesize that there is an increased likelihood of observing genetic signatures from river
capture events when they facilitate range expansion, as is inferred for the two galaxiid taxa studied here. When river
capture merely translocates genetic lineages among established populations, by contrast, we suggest that the genetic
signature of capture is less likely to be retained, as might be inferred for G. breviceps. Rates of molecular evolution
calibrated against this recent event were elevated relative to traditional estimates, consistent with the contribution of
polymorphisms to branch lengths at shallow phylogenetic levels prior to ﬁxation by purifying selection and drift.
Calibration, geology, mitochondrial DNA, molecular clock, range expansion, river capture, vicariance.