Effects of long-term climate change on the functional diversity of molluscan assemblages in the Adriatic Sea

Most studies evaluating shifts in community composition in response to environmental change focus on taxonomic diversity, while functional diversity remains underexplored, particularly in marine ecosystems, despite its relevance to ecosystem functioning. We evaluated shifts in the functional diversity of molluscan nearshore communities in the Adriatic Sea (Italy) in response to late Quaternary climate change. We applied biological traits analysis (BTA) based on a broad range of life history, behavioral, and morphological characteristics to assess these changes.

Previous research by Scarponi et al. (2022) has shown that molluscan nearshore metacommunities in the northern and central Adriatic exhibited a resilient response to large-scale climatic and sea-level fluctuations of the late Quaternary. Taxonomic composition was very similar between the last (Thyrrenian) and the present interglacial (Holocene) but shifted to a different state during the last glacial. We studied the same dataset to test whether glacial assemblages also exhibited distinct functional composition compared to their interglacial counterparts. For this purpose, we applied fuzzy correspondence analysis (FCA, Chevenet et al., 1994). Differences in functional composition were further explored using functional beta diversity (Villéger et al., 2013) between assemblages of the different time intervals. Furthermore, we evaluated changes in functional alpha diversity based on multidimensional functional space (Laliberté & Legendre, 2010).

The results of FCA and beta diversity analysis demonstrate that functional composition was different during the last glacial, whereas it was similar for the two interglacials. Traits that differ most strongly between the glacial and interglacials are attachment type and feeding guild. In addition to differences in composition, functional diversity was higher during the last glacial, when accounted for sample size, which confirms expectations based on the higher taxonomic diversity during that time documented by Scarponi et al. (2022). Our results provide valuable insights into the natural range of variability in functional diversity of nearshore communities in the Adriatic Sea during major shifts in climate and sea level, demonstrating that taxonomic turnover also affected functional composition of assemblages.

 

References

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Laliberté, E., & Legendre, P. (2010). A distance‐based framework for measuring functional diversity from multiple traits. Ecology, 91(1), 299–305. DOI: 10.1890/08-2244.1

Scarponi, D., Nawrot, R., Azzarone, M., Pellegrini, C., Gamberi, F., Trincardi, F., & Kowalewski, M. (2022). Resilient biotic response to long-term climate change in the Adriatic Sea. Global Change Biology, 28(13), 4041–4053. DOI: 10.1111/gcb.16168

Villéger, S., Grenouillet, G., & Brosse, S. (2013). Decomposing functional β-diversity reveals that low functional β-diversity is driven by low functional turnover in European fish assemblages: Decomposing functional β-diversity. Global Ecology and Biogeography, 22(6), 671–681. DOI: 10.1111/geb.12021