Colonisation dynamics during range expansion is poorly predicted by dispersal in the core range

Abstract

The potential ranges of many species are shifting due to changing ecological conditions. Where populations become patchy towards the range edge, the realised distribution emerges from colonisation–persistence dynamics. Therefore, a greater understanding of the drivers of these processes, and the spatial scales over which they operate, presents an opportunity to improve predictions of species range expansion under environmental change. Species reintroductions offer an ideal opportunity to investigate the drivers and spatial scale of colonisation dynamics at the range edge. To this effect, we performed and monitored experimental translocations of water voles to quantify how colonisation and local persistence were influenced by habitat quality and occupancy. We used a novel statistical method to simultaneously consider effects across a range of spatial scales. Densely occupied neighbourhoods were highly persistent and frequently colonised. Persistence was more likely in high quality habitat, whereas the influence of habitat quality on colonisation was less clear. Colonisation of suitable habitat in distant, sparsely occupied areas was much less frequent than expected from the well documented high dispersal ability of the species. Persistence of these distant populations was also low, which we attribute to the absence of a rescue effect in sparsely populated neighbourhoods. Our results illustrate a mismatch between the spatial scales of colonisation dynamics in the core and edge of a species’ range, suggesting that recolonisation dynamics in established populations may be a poor predictor of colonisation dynamics at the range edge. Such a mismatch leads to predictions of long lags between the emergence and colonisation of new habitat, with detrimental consequences for a species’ realised distribution, conservation status and contribution to ecosystem function. Conservation translocations that also reinforce existing populations at the range edge might stimulate the rescue effect and mitigate lags in expansion.

Fishing for mammals: Landscape‐level monitoring of terrestrial and semi‐aquatic communities using eDNA from riverine systems

“…This is particularly relevant in the context of recovery of water vole populations post‐translocation or in situations where remnant populations are bouncing back after invasive American mink Neovison vison control has been instigated. On a local scale, finding signs of water voles through latrine surveys is not necessarily difficult, but monitoring the amount of potential habitat (especially lowland) for a species which has undergone such a massive decline nationally is a huge undertaking (Morgan, Cornulier, & Lambin, ).…”

Mating system induced lags in rates of range expansion for different simulated mating systems and dispersal strategies: a modelling study

“…Predicting how metapopulations will change when in disequilibrium with the environment is made more challenging because key population processes and individual traits may vary from the core to the edge of the species range (Hargreaves and Eckert 2014 ; Morgan et al 2019 ). We extended previous findings that post-dispersal mate-finding requirements led to a higher proportion of unmated females (Shaw and Kokko 2015 ) by revealing large spatial variation in mating success from the core to the edge of the range.…”

Spatiotemporal connectivity dynamics in spatially structured populations

“…While individual variability can account for some variation in effective dispersal (Baguette et al, 2013 ), the spatiotemporal distribution of the disperser pool among habitat patches will likely contribute greatly to the observed variation in effective dispersal. Inclusion of such information into connectivity metrics will better describe observed colonization and occupancy, especially if those population dynamics are thought to be influenced through demographic processes such as the rescue effect (Brown & Kodric‐Brown, 1977 ), Allee effects (Amarasekare, 1998 ) or conspecific attraction (Morgan et al, 2019 ).…”