Colonization of Ireland: revisiting ‘the pygmy shrew syndrome’ using mitochondrial, Y chromosomal and microsatellite markers

Abstract

There is great uncertainty about how Ireland attained its current fauna and flora. Long-distance human-mediated colonization from southwestern Europe has been seen as a possible way that Ireland obtained many of its species; however, Britain has (surprisingly) been neglected as a source area for Ireland. The pygmy shrew has long been considered an illustrative model species, such that the uncertainty of the Irish colonization process has been dubbed 'the pygmy shrew syndrome'. Here, we used new genetic data consisting of 218 cytochrome (cyt) b sequences, 153 control region sequences, 17 Y-intron sequences and 335 microsatellite multilocus genotypes to distinguish between four possible hypotheses for the colonization of the British Isles, formulated in the context of previously published data. Cyt b sequences from western Europe were basal to those found in Ireland, but also to those found in the periphery of Britain and several offshore islands. Although the central cyt b haplotype in Ireland was found in northern Spain, we argue that it most likely occurred in Britain also, from where the pygmy shrew colonized Ireland as a human introduction during the Holocene. Y-intron and microsatellite data are consistent with this hypothesis, and the biological traits and distributional data of pygmy shrews argue against long-distance colonization from Spain. The compact starburst of the Irish cyt b expansion and the low genetic diversity across all markers strongly suggests a recent colonization. This detailed molecular study of the pygmy shrew provides a new perspective on an old colonization question.

Revisiting the phylogeography and demography of European badgers (Meles meles) based on broad sampling, multiple markers and simulations

“…The only securely dated badger fossil in Ireland dates to 1554 BP (P Woodman and M O'Dowd, personal communication) and other fossils are of a Bronze Age context (4000-1500 BP;McCormick, 1999). Therefore, humanmediated introduction(s), which has been reported for other Irish mammals (see, for example, McDevitt et al, 2011), is the most likely scenario and our genetic results support this. Early introductions Figure 6 Inference of the current effective population size, log(N 0 ), of simulated data sets using MSVAR.…”

“…The question of how the island acquired its fauna and flora has long presented a problem (McDevitt et al, 2011). Using data from a shorter fragment of the control region and six microsatellites, O'Meara et al (2012) recently concluded that badgers have colonised Ireland naturally, but failed to identify how and when this occurred.…”

“…We show here that Irish badgers share the majority of their haplotypes with Scandinavia but are closely related to Britain at the microsatellite level (Figures 2a and 3). Natural colonisation from an Iberian source (as we have proposed for Scandinavia) is unlikely because of the absence of evidence for suitable landbridges post LGM (McDevitt et al, 2011) or appropriate fossil evidence before the presence of humans in Ireland (McCormick, 1999). The only securely dated badger fossil in Ireland dates to 1554 BP (P Woodman and M O'Dowd, personal communication) and other fossils are of a Bronze Age context (4000-1500 BP;McCormick, 1999).…”

“…Therefore, it is clear that continent-wide sampling-including adequate sampling of putative refugia-is vital for accurate inference of the phylogeographic history of European species. Furthermore, over recent years phylogeographic studies have included data from multiple markers in order to gain new insights into complex colonisation histories (McDevitt et al, 2011) and processes over different time scales (Avise, 2004).…”

Influence of the human MIF promoter polymorphism on hepatocellular carcinoma prognosis

“…Given the results of our study, it is obvious that high-repetitive-sequence genotypes have a high positive correlation to malignancy grade. McDevitt et al (2011) discovered that Saharan people have a higher frequency of MIF-794CATT promoter microsatellite repetitive sequences. The lowrepetitive-sequence genotype is related to low morbidity of pernicious malaria complications, which suggests that MIF-794CATT 5 is a protective genotype against these complications.…”