Historical biogeography and modes of speciation across high-latitude seas of the Holarctic: concepts for host – parasite coevolution among the Phocini (Phocidae) and Tetrabothriidae (Eucestoda)

Abstract

Species of Anophryocephalus are host-specific parasites of pinnipeds in the Holarctic. Phylogenetic analysis of 7 species postulates A. anophrys as the basal taxon and A. inuitorum as basal to A. skrjabini; A. arcticensis is basal to A. nunivakensis and A. eumetopii + A. ochotensis (single tree; consistency index = 74.4%; homoplasy slope ratio = 36.45%). Evaluation of host and geographic distributions postulates ringed seals of the Atlantic–Arctic as ancestral hosts, and the Arctic basin as a paraphyletic area with respect to the North Pacific. Cospeciation within this assemblage was dependent on intense isolation of small effective populations of definitive hosts during the late Tertiary and Pleistocene glacial stages. Rapid modes of parasite speciation, compatible with microallopatry and peripheral isolation, appear to have been associated with isolation of pinniped populations in refugial habitats of the Arctic basin and Beringia. The biogeography of host–parasite assemblages among pinnipeds and Alcidae (Charadriiformes) during the Pliocene and Quaternary contrasts in part with the history elucidated for some free-living invertebrate taxa in the Arctic basin.