Historical Biogeography of Delphininae Dolphins and Related Taxa (Artiodactyla: Delphinidae)

Abstract

Delphinine dolphins arose via a recent, rapid radiation, probably within the last four million years. Although molecular phylogenies are increasingly well resolved, patterns of morphology-ecology-geography are hard to link to phylogeny or to translate into taxonomy. Such problems might be tackled through understanding the drivers of the delphinine radiation. Here, we examine delphinine historical biogeography using the phylogeny of McGowen et al. (Mol Phylogenet Evol 53:891–906, 2009) as our working hypothesis. We used the “Spatial Analysis of Vicariance” method to delimit modern distribution patterns, including disjunctions involving sister nodes in the Delphininae. The analysis identified disjunct sister nodes, allowing some interpretation of Delphininae biogeography. The Central American Seaway was probably an important gateway for early delphinids, but the succeeding “hard” barrier of the Panama Isthmus had little influence. Southern African waters form the Atlantic-Indo-Pacific gateway, which is sometimes considered a “soft” barrier because of the variation in the Benguela and Agulhas currents, in turn driven by tectonic changes and/or Pleistocene glacial and interglacial cycles. The latter cycles probably fragmented coastal habitats, allowing allopatric speciation. Geological patterns of turnover in Southern Ocean diatoms, which link to physical oceanic change, closely match the main cluster of delphinine divergences. The Eastern Pacific Barrier, and perhaps the associated Humboldt Current and equatorial “cold tongue,” affect modern distributions, but cause and effect are poorly understood. Future research should involve molecular-morphological phylogenetics for all species, subspecies, and ecomorphs. Complete distributions must be known for all taxa to understand how vicariance and dispersal shaped the distribution of delphinines.