Know your enemy : a molecular approach to determine how the pygmy shrew (Sorex minutus) in Ireland succumbs to the invasion of the greater white-toothed shrew (Crocidura russula)

Browett, S

Abstract

Ireland’s smallest resident mammal, the pygmy shrew (Sorex minutus) is rapidly being displaced by the invasive greater white-toothed shrew (Crocidura russula). The presence of this invasive shrew was first recorded in 2007 and they have been expanding their range at a rate of ~5km per year. Considering these two species co- inhabit other regions of Europe, this raises the question of why they seemingly cannot coexist in Ireland. This study applies DNA (and rRNA) metabarcoding to shrew gut contents to investigate the roles of resource competition and gut microbial community structure in this species replacement event. This was applied to over 300 shrews of both species sampled across radial transects in Ireland, two seasons, and a natural ‘control’ site in Belle Île (France) where both species occur together in high abundance. The results show that during the initial stage of colonisation there is little resource competition between the species allowing their ranges to overlap. Over time, interspecific competition increases as the long-term established populations of C. russula switch their diet to the core prey of S. minutus. This could be a result of C. russula exhausting local invertebrate resources, which could be damaging to Ireland’s invertebrate community structure. The Belle Île population of S. minutus can co-exist with C. russula by exploiting locally abundant key taxa, but the Irish S. minutus are not adapting their diet in response to the invader. In addition, Irish S. minutus have a different microbiome structure with a significantly reduced abundance of microbes associated with host immunity which may have left them susceptible to newly introduced stresses. No novel pathogens were detected in the invasive population of C. russula. This diet-microbiome analyses demonstrates that Irish S. minutus have not adapted to compete with another shrew species and could be completely replaced by C. russula in Ireland over time. This multi-faceted approach on this invasive system has demonstrated that subtle differences between populations of shrews can have significant effects on their ability to co-exist.

Citation

Browett, S. Know your enemy : a molecular approach to determine how the pygmy shrew (Sorex minutus) in Ireland succumbs to the invasion of the greater white-toothed shrew (Crocidura russula). (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Apr 21, 2021
• Publicly Available Date: Apr 21, 2021
• Award Date: Dec 1, 2020