Retracing the history and planning the future of the red squirrel (Sciurus vulgaris) in Ireland using non-invasive genetics

Abstract

The Eurasian red squirrel's (Sciurus vulgaris) history in Ireland is largely unknown, but the original population is thought to have been driven to extinction by humans in the 17 th Century, and multiple records exist for its subsequent reintroduction in the 19 th Century. However, it is currently unknown how these reintroductions affect the red squirrel population today, or may do so in the future. In this study, we report on the development of a DNA toolkit for the non-invasive genetic study of the red squirrel. Non-invasively collected red squirrel samples were combined with other samples collected throughout Ireland and previously published mitochondrial DNA (mtDNA) data from Ireland, Great Britain and continental Europe to give an insight into population genetics and historical introductions of the red squirrel in Ireland. Our findings demonstrate that the Irish red squirrel population is on a national scale quite genetically diverse, but at a local level contains relatively low levels of genetic diversity and evidence of genetic structure. This is likely an artefact of the introduction of a small number of genetically similar animals to specific sites. A lack of continuous woodland cover in Ireland has prevented further mixing with animals of different origins that may have been introduced even to neighbouring sites. Consequently, some of these genetically isolated populations are or may in the future be at risk of extinction. The Irish red squirrel population contains mtDNA haplotypes of both a British and Continental European origin, the former of which are now extinct or simply not recorded in contemporary Great Britain. The Irish population is therefore important in terms of red squirrel conservation not only in Ireland, but also for Great Britain, and should be appropriately managed.

Wildlife conservation in a fragmented landscape: the Eurasian red squirrel on the Isle of Wight

“…As S. vulgaris is an arboreal specialist, with a preference for closed canopy (Gurnell et al 2002;Samaras and Youlatos 2010), it is unsurprising that fragmentation of woodland habitats has been shown to affect the genetic diversity of red squirrels (Wauters et al 1994;Hale et al 2001b;Trizio et al 2005;Simpson et al 2013b;Rézouki et al 2014;O'Meara et al 2018). Our findings suggest that this impediment to gene flow may also be true for squirrels on the Isle of Wight.…”

Invasive genetic rescue: Dispersal following repeated culling reinforces the genetic diversity of an invasive mammal

“…This is further confounded by the species’ naturally high level of genetic diversity owing to its evolutionary history in North America where its genetic legacy appears not to have been imprinted by glacial history, limiting interpretation of its phylogeographic history (Moncrief et al 2012). Other Sciurus species have similar phylogeographic legacies including S. niger in North America and S. vulgaris in Eurasia (Grill et al 2009; Moncrief et al 2012; O’Meara et al 2018). All have a high number of mtDNA haplotypes that cannot generally be traced to commonly recognised glacial refugia.…”

“…At the time of the grey squirrel introduction, the native Eurasian red squirrel ( S. vulgaris ) population had been in a state of decline since the 1700s due to harsh winters, deforestation associated with industrialization and shipbuilding, hunting and the trade of wild animals, with red squirrels particularly popular. By the late 19 th Century, there were over 20,000 red squirrels sold annually in London markets, and such was the demand that red squirrels were imported from throughout Europe due to local shortages (Shorten 1954; O’Meara et al 2018). Grey squirrels contributed to further red squirrel population declines as a result of resource competition and the spread of squirrelpox, which is asymptomatic in grey squirrels but pathogenic in red squirrels (Chantrey et al 2014; McInnes et al 2020).…”

Density-habitat relationships of white-tailed deer (Odocoileus virginianus) in Finland

“…Telemetry data thus represents individual-level rather than population-level habitat selection. The use of non-invasive genetic methods provides the possibility to study animal space use without physically marking and recapturing them, for instance by collecting feces (Granroth-Wilding et al 2017, Hagemann et al 2018 or hair (Sun et al 2017, O'Meara et al 2018) left in specific trap or collection devices in the environment (Waits and Paetkau 2005). Spatial information of the individuals is recorded from the capture locations and individual identification is obtained by extracting DNA from the sample and genotyping the samples.…”