Rear‐edge populations are important for understanding climate change risk and adaptation potential of threatened species

Abstract

Climate change disproportionately threatens alpine species, by reducing available habitat and by isolating their populations. These pressures are particularly relevant for rear-edge populations, which typically occupy more marginal habitat compared to populations at the core of species' ranges. We studied Caucasian grouse Lyrurus mlokosiewiczi in the Caucasus ecoregion, a global biodiversity hotspot where this species is endemic, to understand potential climate change impacts on the species. Specifically, we assessed how climate change impacts rear-edge populations and how important these populations are for understanding range shifts and adaptive capacity under climate change. We used maximum entropy modeling to assess changes in the distribution of climatically suitable habitat under present and 2070 climate conditions for the representative concentration pathways 8.5 (RCP8.5). Our results revealed that ignoring rear-edge populations leads to a significant underestimation of the future range (by about 14,700 km 2). Rear-edge populations were better adapted to warmer climates compared to core populations, and ignoring them, therefore, also underestimates adaptive capacity. Preventing the loss of rear-edge populations should, therefore, be a priority for conservation planning in the face of climate change. Because the Caucasian grouse is associated with alpine mountain tops, conservation should focus on establishing connectivity between rear-edge and core populations (e.g., via transboundary corridors or assisted colonizations). Our study reveals how species distribution modeling can highlight the importance of rear-edge populations for mitigating climate change impacts on species of conservation concern.

Local ecological knowledge provides novel evidence on threats and declines for the Caucasian grouse Lyrurus mlokosiewiczi in Arasbaran Biosphere Reserve, Iran

“…We were not able to investigate all potential threats to Caucasian grouse in this study, such as possible predation by sheepdogs (Storch, 2000). This alpine species and its habitat are also likely to become progressively impacted by climate change (Habibzadeh et al, 2021). We acknowledge that we cannot directly assess the accuracy of local perceptions of grouse population dynamics and threats, as there is no comprehensive independent ecological monitoring baseline for understanding grouse population change and associated environmental change in this region to cross‐validate our data, as has been conducted in studies of other social–ecological systems (Cuyler et al, 2020; Zayonc & Coomes, 2022); indeed, this knowledge gap is the reason why we undertook this study.…”

Plant speciation in the Namib Desert: potential origin of a widespread derivative species from a narrow endemic

“…'niche overlap test' (NOT) and 'niche divergence test' (NDT), each of them including the calculation of equivalency (E) and background (B) statistics using 500 replicates. In brief, NOT determines how equivalent (or dissimilar) the occupied niches of the two species are, given their total E-space, while NDT determines significant differences in the species' shared E-space (Brown and Carnaval 2019; see also Habibzadeh et al 2021). In either instance, the E statistic compares the observed value of Schoener's (1968) D metric between the two species, ranging from 0 (no niche overlap) to 1 (complete overlap), with a null distribution obtained from the species' resampled and spatially shifted locality records.…”

Surviving on the edge: present and future effects of climate warming on the common frog (Rana temporaria) population in the Montseny massif (NE Iberia)

“…Although the climate in the Montseny is typically Mediterranean, the massif’s altitude and the northern and eastern exposure of the main hillsides provide humid and temperate conditions ( Panareda-Clopés, 1979 ), thus allowing the persistence of populations of this cold-adapted species. Thus, this massif harbours rear edge populations of the common frog, where the species experiences a small temperature buffer in comparison with most of the range, making these populations a good model to study the effects of climate change on temperate amphibians ( Hampe & Petit, 2005 ; Habibzadeh et al, 2021 ).…”