Specific niche requirements underpin multidecadal range edge stability, but may introduce barriers for climate change adaptation

Abstract

Aim To investigate some of the environmental variables underpinning the past and present distribution of an ecosystem engineer near its poleward range edge. Location >500 locations spanning >7,400 km around Ireland. Methods We collated past and present distribution records on a known climate change indicator, the reef‐forming worm Sabellaria alveolata (Linnaeus, 1767) in a biogeographic boundary region over 182 years (1836–2018). This included repeat sampling of 60 locations in the cooler 1950s and again in the warmer 2000s and 2010s. Using species distribution modelling, we identified some of the environmental drivers that likely underpin S. alveolata distribution towards the leading edge of its biogeographical range in Ireland. Results Through plotting 981 records of presence and absence, we revealed a discontinuous distribution with discretely bounded sub‐populations, and edges that coincide with the locations of tidal fronts. Repeat surveys of 60 locations across three time periods showed evidence of population increases, declines, local extirpation and recolonization events within the range, but no evidence of extensions beyond the previously identified distribution limits, despite decades of warming. At a regional scale, populations were relatively stable through time, but local populations in the cold Irish Sea appear highly dynamic and vulnerable to local extirpation risk. Contemporary distribution data (2013–2018) computed with modelled environmental data identified specific niche requirements which can explain the many distribution gaps, namely wave height, tidal amplitude, stratification index, then substrate type. Main conclusions In the face of climate warming, such specific niche requirements can create environmental barriers that may prevent species from extending beyond their leading edges. These boundaries may limit a species’ capacity to redistribute in response to global environmental change.

Looking for diversity in all the right places? Genetic diversity is highest in peripheral populations of the reef-building polychaete Sabellaria alveolata

“…Cold winters have already led to decadal scale local extinctions of S. alveolata (Firth et al 2015) resulting in loss of genetic diversity locally. Furthermore, despite increasing sea surface temperatures near the northern range edge, which should favor range expansion, populations in Ireland have remained surprisingly stable over the past several decades, limited by unfavorable hydrodynamic conditions (Firth et al 2021). To prevent widespread loss of the species in this potentially more unstable part of the range, monitoring and preservation of populations in the British Isles should be prioritized.…”

Drivers and limits of phenotypic responses in vulnerable seagrass populations:Zostera marinain the intertidal

“…These are often neglected in broadscale seagrass distribution models that mostly focus on temperature and light availability (Jayathilake & Costello, 2018; Wilson & Lotze, 2019). As for other foundation species (Firth et al., 2021), better accounting for local drivers may lead to more accurate projections of seagrass distribution changes. In the future, combining finer scale in situ environmental data with higher resolution models will also be needed to improve our understanding and predictions of seagrass changes in the face of more frequent and intense extreme events (Oliver et al., 2018; Poppeschi et al., 2021).…”

Environmental optima for an ecosystem engineer: a multidisciplinary trait-based approach

“…Not only is this where individuals are in the poorest physiological condition, but it is also where the greatest genetic diversity 64 , and population instability 31 , are found. Taken together with the long-term stability of the poleward-most range edges both in Ireland 32 and in Britain 65 , it is likely that S. alveolata will not be able to advance beyond these edges, even under future climate change scenarios. Only by combining fine-scale data that captures local conditions and proximate physiological responses with regional scale environmental information can we gain an understanding of emergent ecological and biogeographic responses.…”

“…Dense aggregations of these tubes form biogenic reefs 29 , which are afforded statutory protection by the European Union’s Habitat Directive (Council Directive 94/43/EEC). S. alveolata is distributed in the Mediterranean from Scotland to Morocco and, as a warm-adapted species, is known to be negatively affected by cold weather spells 30 – 32 . As environmental impacts on ecosystem engineers may result in cascading effects on ecosystem structure and functioning 33 , we chose to study this species as a pragmatic first step towards gaining insight into the ecological impacts of reproductive responses to environmental stressors.…”