Geological Dates and Molecular Rates: Rapid Divergence of Rivers and Their Biotas

Abstract

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 phylogeographic 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 reciprocally 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 consistent 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 overestimated 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.

Contrasting genetic structuring between colonies of the World’s smallest penguin, Eudyptula minor (Aves: Spheniscidae)

“…These mutation rates are more rapid than those traditionally employed (e.g. 0.208 · 10 -6 changes per site per year, Quinn 1992), but seem more appropriate for populationlevel analyses (Burridge et al 2006;Ho and Larson 2006;Waters et al 2007). …”

Biogeography of Amazonian fishes: deconstructing river basins as biogeographic units

“…Biotic dispersal has been a major factor in historical hybridization and diversity generation in Amazonian rivers. This is a consequence of the importance of neotectonic activity and resulting rearrangements in the drainage network as diversity-generating factors, both in freshwater fishes in general (Burridge et al, 2006Cardoso, Montoya-Burgos, 2009;Waters et al, 2007) and neotropical fishes in particular Lima, Ribeiro, 2011;Ribeiro et al, 2013;Roxo et al, 2014;Tagliacollo et al, 2015). Those observations and ensuing conclusions prompt a reevaluation of the assumption that vicariant and dispersalist events in their pure form are the best explanation for the diversification of the neotropical fish fauna.…”

Biogeographic calibrations for the molecular clock

“…River drainage patterns change when stream sections move the direction of their flow from one catchment to another, a phenomenon known as river capture. These events tend to occur much more rapidly than other geological transformations, meaning that there is considerably more precision in calibrations based on changes in riverine connections than on other geodispersal events [35].…”