Range Expansion in an Invasive Small Mammal: Inﬂuence of Life-History and Habitat Quality

View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by RERO DOC Digital Library Biol Invasions (2012) 14:2203–2215 DOI 10.1007/s10530-012-0225-x ORIGINAL PAPER Range expansion in an invasive small mammal: influence of life-history and habitat quality Thomas A. White • Mathieu G. Lundy • W. Ian Montgomery • Sally Montgomery • Sarah E. Perkins • Colin Lawton • John M. Meehan • Tom J. Hayden • Gerald Heckel • Neil Reid • Jeremy B. Searle Received: 22 November 2011 / Accepted: 9 April 2012 / Published online: 18 April 2012 Ó Springer Science+Business Media B.V. 2012 Abstract Invasive species pose a major threat to demographic parameters. We subsequently modelled biodiversity but provide an opportunity to describe the the processes involved in its range expansion using a processes that lead to changes in a species’ range. The rule-based spatially explicit simulation. Habitat suit- bank vole (Myodes glareolus) is an invasive rodent ability interacted with density-dependent parameters that was introduced to Ireland in the early twentieth to influence dispersal, most notably the density at century. Given its continuing range expansion, the which local populations started to donate emigrating substantial empirical data on its spread thus far, and individuals, the number of dispersing individuals and the absence of any eradication program, the bank vole the direction of dispersal. Whilst local habitat vari- in Ireland represents a unique model system for ability influenced the rate of spread, on a larger scale studying the mechanisms influencing the rate of range the invasion resembled a simple reaction–diffusion expansion in invasive small mammals. We described process. Our results suggest a Type 1 range expansion the invasion using a reaction–diffusion model where the rate of expansion is generally constant over informed by empirical data on life history traits and time, but with some evidence for a lag period T. A. White (&) Á J. B. Searle S. Montgomery Department of Ecology and Evolutionary Biology, W5@Odyssey, 2 Queen’s Quay, Belfast BT3 9QQ, Cornell University, Corson Hall, Ithaca, NY 14853-2701, Northern Ireland, UK USA e-mail: [email protected] S. E. Perkins Cardiff School of Biosciences, Biomedical Sciences T. A. White Á G. Heckel Building, Museum Avenue, Cardiff CF10 3AX, UK CMPG Lab, Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012 Bern, C. Lawton Switzerland Martin Ryan Institute, NUI, Galway, Ireland M. G. Lundy Á W. I. Montgomery J. M. Meehan Á T. J. Hayden School of Biological Sciences, Queen’s University School of Biology & Environmental Science, University Belfast, MBC, 97 Lisburn Road, Belfast BT9 7BL, College Dublin, Belfield, Dublin 4, Ireland Northern Ireland, UK W. I. Montgomery Á N. Reid Quercus, School of Biological Sciences, Queen’s University Belfast, MBC, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK 123 2204 T. A. White et al. following introduction. We demonstrate that a two- habitat (Morgia et al. 2011;Ovaskainen2004). Indeed, parameter empirical model and a rule-based spatially the distribution and abundance of suitable habitat explicit simulation are sufficient to accurately describe predicate successful colonization (Hanski 1999). Phys- the invasion history of a species that exhibits a ical features such as water bodies and mountain ranges complex, density-dependent pattern of dispersal. may act as barriers to dispersal (Gerlach and Musolf 2000; Kozakiewicz et al. 2009). Variation in climate, Keywords Invasive species Á Reaction–diffusion Á resources and landscape connectivity generate differ- Non-commensal Á Mammal Á Island Á Landscape Á ential rates of expansion across space (Grosholz 1996; Dispersal Á Life-history Phillips et al. 2008; Urban et al. 2008;With2002). Using model systems to understand how landscape influences the spread of colonizing species is critical to Introduction making realistic predictions of the likelihood of introduction and establishment of non-native species or Species’ introductions can be highly detrimental to successful re-introductions for conservation purposes natural communities, ecosystem integrity, agriculture, (Morgia et al. 2011;Ovaskainen2004). fisheries and public health (Lee 2002). However, they Small to medium-sized mammals include some of provide an opportunity to examine the processes the most notorious invasive species (Clout and Veitch which lead to changes in a species’ range, of relevance 2002), including the house mouse (Mus musculus), to both pure and applied population biology (Lodge Rattus species (R. rattus, R. norvegicus, R. exulans), the et al. 2006; Parmesan and Yohe 2003). European rabbit (Oryctolagus cuniculus), coypu (Myc- Successful colonisation by a non-native species ocastor coypus), muskrat (Ondatra zibethicus), grey progresses through three stages: (i) inoculation, (ii) squirrel (Sciurus carolinensis) and American mink establishment (often including a lag period) and (iii) (Neovison vison). However, it is rather rare to have the range expansion (Williamson 1996). There are three opportunity to study a small mammal invasion where distinct patterns of range expansion (Shigesada and the range is continuing to expand, and where the Kawasaki 1997; Shigesada et al. 1995): Type 1 is process of invasion is not being modified by an characterised by a radial invasion range (i.e. the eradication program. Here we examine the range square-root of the area of the range) which increases expansion of a non-commensal small mammal where linearly as a function of time. Such a pattern is derived the data available allow a particularly detailed analysis from population growth and simple short-distance of the invasion process. The bank vole (Myodes diffusion or local Brownian motion (Skellam 1951). glareolus, formerly of the genus Clethrionomys)is Expansion takes place only along the edge of the range widely distributed throughout Eurasia from Iberia to because in this situation dispersing individuals settle central Siberia and from northern Scandinavia to the in the vicinity of the parent population. Type 2 is Mediterranean but was not recorded in Ireland until characterised by a biphasic expansion typically with a 1964 (Claassens and O’Gorman 1965). Analysis of slow rate of spread initially followed by a higher mitochondrial DNA and vole parasite populations constant rate and Type 3 is characterised by an supports a single colonisation event in the late 1920s exponential rate of spread i.e. accelerating increase involving a small number of founders arriving on the over time (Shigesada and Kawasaki 1997; Shigesada southern shore of the Shannon estuary (Fairley 1971a, et al. 1995). Patterns 2 and 3 occur in species capable 1997;Ryanetal.1996; Stuart et al. 2007). The latter of long-distance dispersal relative to range size where suggest that to date of introduction was 1926 at Foynes, new colonies are established far beyond the edge of the Co Limerick, where heavy, earth moving equipment range. These scenarios assume uniform dispersal was landed from Germany prior to the construction of based on demographic processes but species can often the Shannon hydroelectricity scheme. The first system- possess complex reactions to landscape and habitat atic distribution surveys established that the bank vole structure which influence their direction and rate of was restricted to south-west Ireland (Fairley 1971b; spread (Gustafson and Gardner 1996). Fairley and O’Donnell 1970) and hindcast extrapola- Dispersal rates and range expansion may vary tions suggested that the species began to expand its according to the distribution and quality of suitable range (possibly after an initial lag period) sometime 123 Range expansion in an invasive small mammal 2205 during the 1940s or 1950s, expanding in all directions at thesis), and, (iv) 2010 (T. White field data, and an estimated rate of 1.0–4.5 km year-1 (Smal and Montgomery et al. 2012). Incidental records were also Fairley 1984). Recent work suggests that the bank vole collated (Fairley 1985, 1992; Leirs et al. 1987; may have major impacts on well-established small McHugh and Boyle 2010; McHugh and Lawton mammal communities in Ireland (Montgomery et al. 2005; Smal and Fairley 1978; Smiddy and Sleeman 2012) reducing population density of the wood mouse 1994). These collated records are shown in Fig. 1. (Apodemus sylvaticus) and pygmy shrew (Sorex minutus ). Further, it interacts with another recent invader, Observed patterns of range expansion the greater-white toothed shrew Crocidura russula (Tosh et al. 2008), to bring about the extinction (or Range maps of species’ spread were created for 1969/ Sorex minutus severe reduction) of the pygmy shrew ( ), 70 (including non-systematic data collected from 1964 a rare example of invasional meltdown (Simberloff and to 1969), 1975, 1982, 1984, 1985, 1992, 2001, 2003 Von Holle 1999). Moreover, such changes in the small and 2010. Range boundaries for each time-point were mammal community are likely to alter ecosystem fitted using a-hull polygons using the R (CRAN 2011) processes at various trophic levels from plants to package alphahull where a = 1 (Burgman and Fox predators (Montgomery et al. 2012). Given the imprac- 2003). The land area occupied at each time point was ticality of eradication, it is probable that the bank vole’s calculated using the R package geosphere, and the range in Ireland will continue to expand until the whole pffiffiffiffiffiffiffiffiffi radial invasion range was calculated as A=p, where island is occupied. A is the invaded area. This assumed a circular We use an extensive dataset with detailed informa- distribution for the range area that expands equally tion on population distribution to determine the mech- in all directions. Used in an uninformed way this may anisms influencing the invasion and range spread of the be inappropriate for invasions which proceed in an bank vole in Ireland. Firstly, we examined how observed asymmetric manner, such as that of the bank vole in expansion rates fitted the expected patterns of Type 1, 2, Ireland whose invasion has been bounded in the south- and 3 invasions.

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