Thursday, October 16, 2014

Foxy Phylogenetic Findings

The red fox (Vulpes spp.) is earth's most widely distributed terrestrial carnivore, its natural range encompassing North America, Eurasia, and northern Africa.  Having been introduced Down Under by British settlers, this canine is now also found throughout Australasia.  On September 25, 2014, Mark Statham et al. published a detailed phylogeography of the red fox, which answered several questions biologists have long debated about vulpine origins, evolution, and biogeography.  Their article in the journal Molecular Evolution, entitled "Range-wide multilocus phylogeography of the red fox reveals ancient continental divergence, minimal genomic exchange and distinct demographic histories", includes the following evolutionary insights:
Analyses of 697 bp of mitochondrial sequence in ~1000 individuals suggested an ancient Middle Eastern origin for all extant red foxes and a 400 kya (SD=139 kya) origin of the primary North American (Nearctic) clade. Demographic analyses indicated a major expansion in Eurasia during the last glaciations ( ~50 kya), coinciding with a previously described secondary transfer of a single matriline (Holarctic) to North America. In contrast, North American matrilines (including the transferred portion of Holarctic clade) exhibited no signatures of expansion until the end of the Pleistocene ( ~12 kya).
Samples of nuclear DNA were also sequenced from a subset of the above thousand foxes portions of whose mitochondrial DNA were sequenced.  What emerges are two long-separated phylogenetic lineages of red foxes - one North American and the other Eurasian - with no natural biological truck nor trade between them.  To adapt an observation made by Redd Foxx to make it applicable to the red fox, "Phenotype may be skin deep, but a genotype goes clear to the bone."

Improvements in the speed, efficiency, and cost of automated DNA sequencing increasingly allow huge genomic studies to reveal detailed evolutionary patterns at global scales.  Not only does such research resolve questions about red foxes, it may also shed light on the evolution of our own lineage (e.g., Fu et al. 2013) and disease-causing organisms like Ebola (e.g., Gire et al. 2014).