Scale dependency of metapopulation models used to predict climate change impacts on small mammals

Abstract

To investigate potential range shifts in a changing climate it is becoming increasingly common to develop models that account for demographic processes. Metapopulation models incorporate the spatial confi guration of occupied habitat (i.e. arrangement, size and quality), population demographics, and inter-patch dispersal making them suitable for investigating potential threats to small mammal range and abundance. However, the spatial scale (resolution) used to represent speciesenvironment dynamics may aff ect estimates of range shift and population resilience by failing to realistically represent the spatial confi guration of suitable habitat, including stepping stones and refugia. We aimed to determine whether relatively fi ne-scale environmental information infl uenced predictions of metapopulation persistence and range shift. Species distribution models were constructed for four small terrestrial mammals from southern Australia using environmental predictors measured at 0.1 ϫ 0.1 km (0.01 km 2 ) or 1.0 ϫ 1.0 km (1 km 2 ) resolution, and combined with demographic information to parameterise coupled niche-population models. Th ese models were used to simulate population dynamics projected over 40-yr under a stable and changing climate. Initial estimates of the area of available habitat were similar at both spatial scales. However, at the fi ne-scale, habitat confi guration comprised a greater number of patches (ca 12 times), that were more irregular in shape (ca 8 times the perimeter:area), and separated by a tenth of the distance than at the coarse-scale. While small patches were not more prone to extinction, populations generally declined at a higher rate and were associated with a lower expected minimum abundance. Despite increased species vulnerability at the fi ne-scale, greater range shifts were measured at the coarse-scale (for species illustrating a shift at both scales). Th ese results highlight the potential for range shifts and species vulnerability information to be misrepresented if advanced modelling techniques incorporating species demographics and dispersal inadequately represent the scale at which these processes occur.

Microhabitat comparison of swamp rabbit sites between periphery and core of the species range

“…Our comparison of such features between the core of the swamp rabbit's distribution and the edge of its geographic range documents a case of usable habitat space diminishing at peripheral locations. Understanding such microhabitat relationships and their distribution across a species' range can be invaluable in anticipating how species' ranges may shift (Haby et al , Hannah et al ) in response to forces like climate change (Anderson et al ).…”

Demographic and reproductive plasticity across the depth distribution of a coral reef fish

“…The global deterioration of natural habitats such as coral reefs, as a consequence of stressors including urban expansion, overharvest, and climate change 1 2 3 , may lead to the spatial restriction of populations of wild organisms to the periphery of their distributions 4 5 . Mesophotic habitats at the depth boundary of photosynthetic coral reefs may be buffered from storms, temperature fluctuations, and fishing pressure 5 6 , thus safeguarding subpopulations of reef organisms from numerous stressors.…”

Structural uncertainty in models projecting the consequences of habitat loss and fragmentation on biodiversity

“…A new generation of SDM that integrate process-based approaches have modified classic SDM in several ways: 1) by including physiology (Kearney and Porter 2009), species interactions (Trainor and Schmitz 2014), population dynamics (Leroux et al 2013) and movement (Vasudev et al 2015), 2) by formulating hybrid models that pair correlative models with additional ecological processes (e.g. population viability model; Haby et al 2013), and 3) by using co-occurrence data as a covariate in joint SDM (Pollock et al 2014).…”