DOI: 10.5061/dryad.rr4xgxdcq
title: Resource competition drives an invasion-replacement event among shrew species on an island

description: Invasive mammals are responsible for the majority of native species'
 extinctions on islands. While most of these extinction events will be due
 to novel interactions between species (e.g. exotic predators and naive
 prey), it is more unusual to find incidences where a newly invasive
 species cause the decline/extinction of a native species on an island when
 they normally coexist elsewhere in their overlapping mainland ranges. We
 investigated if resource competition between two insectivorous small
 mammals was playing a significant role in the rapid replacement of the
 native pygmy shrew (Sorex minutus) in the presence of the recently
 invading greater white-toothed shrew (Crocidura russula) on the island of
 Ireland. We used DNA metabarcoding of gut contents from &gt;300
 individuals of both species to determine each species’ diet and measured
 the body size (weight and length) during different stages of the invasion
 in Ireland (before, during, and after the species come into contact with
 one another) and on a French island where both species have long coexisted
 (acting as a natural ‘control’ site). Dietary composition, niche width,
 and overlap, and body size were compared in these different stages. The
 body size of the invasive C. russula and the composition of its diet
 change between when it first invades an area and after it becomes
 established. During the initial stages of the invasion, individual shrews
 are larger and consume larger-sized invertebrate prey species. During the
 later stages of the invasion, C. russula switch to consuming smaller prey
 taxa that are more essential for the native species. As a result, the
 level of interspecific dietary overlap increases from between 11–14% when
 they first come into contact with each other to between 39–46% after the
 invasion. Here we show that an invasive species can quickly alter its
 dietary niche in a new environment, ultimately causing the replacement of
 a native species. In addition, the invasive shrew could also be
 potentially exhausting the local resources of larger invertebrate species.
 These subsequent changes in terrestrial invertebrate communities could
 have severe impacts further downstream on ecosystem functioning and
 services.
description: This is a metabarcoding dataset for Browett, S.S., Synnott, R.,
 O'Meara, D., Antwis, R.E., Browett, S.S., Bown, K., Wangensteen, O.,
 Dawson, D.A., Searle, J.B., Yearsley, J.M. and McDevitt, A., 2022.
 Resource competition drives an invasion-replacement event among shrew
 species on an island. <em>bioRxiv</em>. doi: https://doi.org/10.1101/2022.04.27.489660 Briefly, DNA was extracted from the gut contents of &gt;300 shrews (<em>Sorex minutus</em> and <em>Crocidura russula</em>). The COI region was amplified using a primer set referred to as Gillet. There are eight multiplexed fastq files from each of the two sequencing runs. Four forward read files and four reverse read files for each run. Samples were multiplexed using primers with dual-index 8 base pair MID tags on them. The sequences contain the primer region and MID tags. A file with the list of tags and primer sequence is included. Sequencing adapters were ligated using a PCR-free method. The final library with a total of 303 samples, five extraction blanks, and 20 PCR blanks was sequenced on two Illumina MiSeq runs using V2 2x150 bp cycle kits, both loaded at 9pM with a 5% PhiX (v3, Illumina) spike For full details on data collection, preparation and sequencing, see https://doi.org/10.1101/2022.04.27.489660 (and forwarding link to published article) and https://github.com/ShrewlockHolmes/ Further information on samples is also available from https://github.com/ShrewlockHolmes/
description: The list containing the MID tags and individual sample names for
 each library are included. The columns are 1: Primer
 used 2: Sample ID 3: Forward MID
 tag 4: Reverse MID tag 5: Forward
 primer sequence 6: Reverse primer sequence
 7:9 misc info required for pipeline used for the
 article.