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

Abstract

Species distributions have been profoundly affected by past climate change, and are expected to change considerably in response to future environmental change. To better apprehend how future climate change is likely to affect genetic diversity in marine populations, it is essential to first evaluate the processes that have shaped the current distribution of genetic diversity in the sea. The honeycomb worm is a reef-building polychaete that hosts high biodiversity. Here we show that the genetic diversity in populations of S. alveolata is highest towards the edges of the current species range and lowest at its center. Pleistocene glacial cycles likely led to extirpations of S. alveolata from central populations in the Bay of Biscay, with coalescent-based estimates of post-glacial colonization dating to the beginning of the Holocene interglacial, from 10,000 to 14,000 years ago. Meanwhile, populations in the Irish Sea and English Channel likely persisted in glacial refugia since the Eemian interglacial, 120,000 years ago. Northern populations host at least two sets of divergent haplotypes, indicating that two refugia possibly existed in the north, with Ireland being a likely second refugium. Within biogeographic regions, populations were overall well-connected, but strong genetic differentiation suggests that little exchange occurs between regions. These two unexpected reservoirs of genetic diversity at the range edges deserve greater attention as warming temperatures threaten trailing edge populations, while greater climatic variability threatens leading edge populations.

Connectivity modelling informs metapopulation structure and conservation priorities for a reef‐building species

“…James et al, 2019;Jupe et al, 2020), affecting their capacity to overcome local hydrodynamic features. Genetic data also show some degree of differentiation among populations from the north and south of the Gironde estuary (Nunes et al, 2021), supporting our interpretation that the southern populations in the Bay of Biscay could be more isolated.…”

“…The absolute numbers of dispersing larvae and settlers are dependent on the production levels of local reefs, unknown for most S. alveolata reefs. Nevertheless, assessing relative connectivity potential (regardless of local spawning potential, as here we assumed homogeneous release of larvae) holds meaningful biological interpretation as these results strongly concur with the genetic structure of S. alveolata reefs Nunes et al (2021). showed that reefs along the Bay of Biscay and the English Channel were well connected within each region, but only little exchange seems to occur between the two regions.…”

“…Furthermore, these are characterized by the highest genetic diversity among Atlantic S. alveolata reefs-another indication of large populations(Nunes et al, 2021), and are likely to contribute to wider metapopulation persistence acting as an important source of larvae to other reefs. Habitat suitability for S. alveolata is, however, predicted to significantly decline under future climate change scenarios(Curd et al, 2021), thus conservation efforts will be of critical importance to minimize local stressors and consolidate the resilience of these key connectivity hubs against anthropogenic-and climatedriven changes.Stepping-stone reefs are, on the other hand, key for connecting distant populations otherwise disconnected, and represent disproportionately important linking pathways among discrete network components(Boulanger et al, 2020).…”

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

“…This study adds to the mounting evidence that the poleward edge populations of S. alveolata are vulnerable. 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.…”

Nuevos registros de ocurrencia extienden la distribución norte de Dromiciops (Thomas, 1894) en Argentina

“…Esta área está afectada por el incremento de plantaciones forestales, ganadería, uso agrícola intensivo y por contar con una menor superficie de áreas protegidas (Otavo & Echeverría 2017). Además, las poblaciones geográficamente periféricas son de interés en biología evolutiva por su diferenciación genética y potencial evolutivo, aunque son las que tienen más probabilidades de extinción debido a eventos estocásticos o catastróficos (Lesica & Allendorf 1995;Botero-Delgadillo et al 2020;Nunes et al 2021). Así, la importancia de las poblaciones geográfica y/o ecológicamente marginales se hace especialmente pertinente en el contexto del cambio climático global (Abeli et al 2018).…”