Geography and host biogeography matter for understanding the phylogeography of a parasite

Abstract

The co-evolution between hosts and parasites has long been recognized as a fundamental driver of macro-evolutionary patterns of diversification. The effect of co-differentiation on parasite diversification is, however, often confounded by underlying geographic patterns of host distribution. In order to disentangle the confounding effects of allopatric versus host speciation, the mitochondrial cytochrome b (cyt b) gene was sequenced in seventy individuals of the parasitic nematode genus Heligmosomoides sampled in the six Apodemus mice species common in the western Palearctic region. The nuclear internal transcribed spacers (ITS) 1 and 2 were also sequenced in fifteen parasites to confirm the mitochondrial data. All lineages differentiated according to a geographic pattern and independently from the sampled host species. This suggests that host speciation did not involve concurrent parasite speciation. However, the geographic distribution range of some parasite lineages mirrors that of A. sylvaticus lineages in SW Europe, and that of A. flavicollis lineages in the Balkans and in the Middle East. Thus, regional co-differentiation likely occurred between the parasite and the two sister Apodemus hosts in different parts of their distribution range. We suggest that differences in regional abundances of A. sylvaticus and A. flavicollis are responsible for generating this pattern of regional co-differentiation. This study highlights the importance of integrating both geography and biogeographic information from potential hosts to better understand their parasite phylogeography.

Finding Them Before They Find Us: Informatics, Parasites, and Environments in Accelerating Climate Change

“…In short, parasite diversification has unfolded (in part) through episodic shifts in climate and environmental settings in conjunction with both ecological mechanisms and host switching (e.g., Hoberg and Klassen, 2002;Nieberding et al, 2008;Hoberg et al, 2012;Hoberg and Brooks, 2013). Such an ecocentric view of parasite diversification, tied to considerable complexity in ecological processes, counters more than a century of coevolutionary thinking about the nature of the development of host-parasite assemblages (for comprehensive reviews, see Brooks andMcLennan, 1993, 2002;Janz, 2011).…”

Population genetic structure of the parasitic nematode Camallanus cotti inferred from DNA sequences of ITS1 rDNA and the mitochondrial COI gene

“…Blouin et al, 1995;Presa et al, 2002;Mejía-Madrid et al, 2007;Nieberding et al, 2008). Because the mitochondrion is inherited maternally, mitochondrial markers offer the advantage of a single haplotype for each sample.…”

Heligmosomoides neopolygyrus Asakawa & Ohbayashi, 1986, a cryptic Asian nematode infecting the striped field mouse Apodemus agrarius in Central Europe

“…On the other hand, if these taxa represent distinct terminal clades, then the hypothesis that they are independent species would continue to deserve consideration. Scrutiny of the phylogeny of Nieberding et al [10] does indeed reveal an additional H. polygyrus clade (their clade 4) which lies outwith the entire sampled H. polygyrus/H. polygyrus corsicum clade.…”

“…H. costellatum from Microtus arvalis was also available from the latter site. Material of H. polygyrus corsicum, from the same collections used in a study by Nieberding et al [10,11] was also examined. H. bakeri was obtained from the Nottingham laboratory colony of this species [5].…”

“…A problem with the taxonomy of Heligmosomoides concerns the poor standards of description and lack of type material for older species such as H. polygyrus, originally described as Strongylus polygyrus by Dujardin [8]. This problem was exacerbated by the finding that, based on comparison of a fragment of the cytochrome b (cytb) mitochondrial gene, H. polygyrus exists in its wild hosts as numerous distinct and geographically discrete clades [9][10][11], which may or may not represent cryptic species. Indeed, Cable et al [5] concluded that the problem lay not with our understanding of the laboratory model H. bakeri, but with our lack of knowledge of the broader H. polygyrus clade.…”