It is exciting to be living at a time when the big questions in biology can be investigated using modern genetics and computing. Bauzà-Ribot et al. take on one of the fundamental drivers of biodiversity, the effect of continental drift in the formation of the world’s biota, employing next-generation sequencing of whole mitochondrial genomes and modern Bayesian relaxed molecular clock analysis. Bauzà-Ribot et al. conclude that vicariance via plate tectonics best explains the genetic divergence between subterranean metacrangonyctid amphipods currently found on islands separated by the Atlantic Ocean. This finding is a big deal in biogeography, and science generally, as many other presumed biotic tectonic divergences have been explained as probably due to more recent transoceanic dispersal events. However, molecular clocks can be problematic and we have identified three issues with the analyses of Bauzà-Ribot et al. that cast serious doubt on their results and conclusions. When we reanalyzed their mitochondrial data and attempted to account for problems with calibration [5,6], modeling rates across branches and substitution saturation, we inferred a much younger date for their key node. This implies either a later trans-Atlantic dispersal of these crustaceans, or more likely a series of later invasions of freshwaters from a common marine ancestor, but either way probably not ancient tectonic plate movements.

Sequence data from Phillips et al, Current Biology (2013)amphipods30_12_rlc3.xml