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We highlight a novel molecular clock calibration system based on geologically dated river reversal and river capture events. Changes in drainage pattern may effect vicariant isolation of freshwater taxa, and thus provide a predictive framework for associated phylogeographic study. As a case in point, New Zealand’s Pelorus and Kaituna rivers became geologically isolated from the larger Wairau River system 70 to 130 kyr BP. We conducted mitochondrial DNA phylogeo- graphic analyses of two unrelated freshwater-limited fish taxa native to these river systems (Gobiomorphus breviceps, n = 63; Galaxias divergens, n = 95). Phylogenetic analysis of combined control region and cytochrome b sequences yielded re- ciprocally monophyletic clades of Pelorus-Kaituna and Wairau haplotypes for each species. Calibrated rates of molecular change based on this freshwater vicariant event are substantially faster than traditionally accepted rates for fishes but con- sistent with other recent inferences based on geologically young calibration points. A survey of freshwater phylogeographic literature reveals numerous examples in which the ages of recent evolutionary events may have been substantially over- estimated through the use of "accepted" calibrations. We recommend that—wherever possible—biologists should start to reassess the conclusions of such studies by using more appropriate molecular calibrations derived from recent geological events. [Biogeography; calibrations; coalescent; fish; freshwater; geomorphology; geology; molecular clock; mutation rate; palaeogeography; Pleistocene; purifying selection; refugia; time dependency; vicariance]

Item Type:	Refereed Article
Research Division:	Biological Sciences
Research Group:	Evolutionary biology
Research Field:	Biogeography and phylogeography
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the biological sciences
UTAS Author:	Burridge, CP (Associate Professor Christopher Burridge)
ID Code:	59463
Year Published:	2007
Web of Science® Times Cited:	54
Deposited By:	Zoology
Deposited On:	2009-12-02
Last Modified:	2009-12-09
Downloads:	2 View Download Statistics