Taxonomy, genetic differentiation and Holarctic biogeography of Paranoplocephala spp. (Cestoda: Anoplocephalidae) in collared lemmings (Dicrostonyx; Arvicolinae)

Abstract

The present study reviews the taxonomy of anoplocephalid cestodes of collared lemmings (Dicrostonyx spp.) and describes the patterns of cestode biogeography in the Holarctic region. The morphological differentiation of cestode species is augmented with a genetic differentiation based on three independent markers. We show that collared lemmings are parasitized by five host-specific species of Paranoplocephala, three of which are described here as new P. arctica (Rausch, 1952), P. alternata sp. nov., P. serrata Haukisalmi & Henttonen, 2000,P. nordenskioeldi sp. nov. and P. krebsi sp. nov. The redescription of P. arctica shows that the original description of this species is composite. Paranoplocephala alternata, P. serrata and P. nordenskioeldi are shown to have a Holarctic distribution, whereas P. arctica and P. krebsi are restricted to the Nearctic region, including Wrangel Island. It is suggested that the Holarctic species colonized North America concomitantly with their hosts and that the appearance of the Nearctic species is connected with the subsequent divergence of collared lemmings in North America. Geographical distribution and sequence data for the first transcribed spacer (ITS1) of nuclear rDNA show thatP. alternata and P. arctica are sister taxa and that the latter species probably diverged from P. alternata in eastern Beringia. Other phylogenetic relationships among cestode species remained largely unsettled.