Phylogeny, historical biogeography, and ecology of Anophryocephalus spp. (Eucestoda: Tetrabothriidae) among pinnipeds of the Holarctic during the late Tertiary and Pleistocene

Abstract

Phylogenetic systematic analyses of Anophryocephalus spp. resulted in a single most-parsimonious cladogram (consistency index: 80%). Cladograms for pinniped hosts (phocids and otariids) and Anophryocephalus spp. were highly incongruent, corroborating a hypothesis for colonization as a dominant determinant of parasite diversification. Phoca (Pusa) spp. in the Atlantic basin are postulated as the initial hosts; range expansion for hosts and parasites into the Pacific basin through the Arctic (ca. 3.0–2.5 million years ago) was followed by radiation of Anophryocephalus spp. among Phoca spp. and subsequent colonization of otariids (Eumetopias jubatus as typical hosts; ca. 2.0 million years ago). Host phylogeny and historical biogeography in conjunction with host distributions of these cestodes indicate evolution of Anophryocephalus was associated with dispersal and radiation of Phoca spp. in the Holarctic during the Late Pliocene and Pleistocene. Isolation in regional refugia and vicariance (during stadials) and subsequent range expansion and sequential colonization (interstadials) are postulated as the primary determinants of host–parasite diversification in the North Pacific during the late Tertiary and Quaternary. Colonization is regarded as a central theme in the development of cestode faunas among marine homeotherms.