Does island ontogeny dictate the accumulation of both species richness and functional diversity?

Abstract

Aim:The accumulation of functional diversity in communities is poorly understood.Conveniently, the general dynamic model of island biogeography (GDM) makes predictions for how such diversity might accumulate over time. In this multiscale study of land snail communities on 10 oceanic archipelagos located in various regions of the globe, we test hypotheses of community assembly in systems where islands serve as chronosequences along island ontogeny.Location: Ten volcanic archipelagos. Time period:From 23 Ma to the present.Major taxa studied: Endemic land snails.Methods: Initially, we assembled geological island characteristics of area, isolation and ontogeny for all studied islands. We then characterized island-scale biotic variables, including the species diversity and functional diversity of snail communities.From these data, we assessed relationships between island and snail community variables as predicted by the GDM, focusing initially on the islands of the Galápagos archipelago and thereafter with a broader analysis of 10 archipelagoes. Results:As in other studies of island assemblages, in Galápagos we find a humpshaped curve of species richness, with depauperate snail faunas on early-ontogeny islands, increasing species richness on mid-ontogeny islands and low species richness on islands in late ontogeny. We find exceptionally low functional diversity on early-ontogeny islands that increases through mid-ontogeny, whereas late-ontogeny islands exhibit a range of functional diversity. The analysis including all 10 archipelagos indicates a major role of archipelago-specific factors. In both sets of analyses, functional diversity is exceptionally low on early-ontogeny islands, and island ontogeny is a significant predictor of morphology.Main conclusions: Consistent patterns of functional diversity across island ontogeny on all examined archipelagos indicate a common role for habitat filtering, ecological opportunity and competition in a diversity of systems, leading to predictable changes in functional diversity and average morphology through island ontogeny, whereas patterns of species richness appear subject to archipelago-specific factors.

Evolutionary history of inshore oceanic island land snails diversified in shell colour

“…As independent variables, this study used island area, elevation, the average distance from the surrounding landmasses and the changing rate of effective population sizes (Appendix 5; Table S6). Although previous studies have demonstrated that island age affects the species richness and functional diversity of land snails (Kraemer et al, 2022; Parent & Crespi, 2006), we did not use island age because the Izu Islands are relatively young (Tani et al, 2011) and detailed geological data are unknown. The species phylogeny with the estimated divergence times was converted to a variance–covariance matrix using the ‘ape’ library on R (Paradis & Schliep, 2019; R Core Team, 2022) and added to our model.…”

“…The second variable was island elevation. Similar to island areas, elevation is also expected to increase environmental heterogeneity and contribute to species richness (Chiba et al, 2009;Parent & Crespi, 2006) and phenotypic diversity of the snail community (Kraemer et al, 2022).…”

Snailed It! Inside the Shell: Using Augmented Reality as a Window Into Biodiversity

“…However, our research team is particularly interested in exploring biodiversity in native land snails in South America (Parent and Crespi, 2006;Phillips et al, 2020;Kraemer et al, 2021). Globally, snails possess extraordinary diversity and high levels of endemism, and represent 70% of mollusk extinctions.…”

Species richness and composition of Caribbean aquatic entomofauna: role of climate, island area, and distance to mainland

“…After their complete emergence, islands are transformed by erosion processes, which causes a reduction in topographical complexity and habitat diversity affecting the rate of immigration, speciation and species extinction (Fernández-Palacios de Nascimento et al 2011, Whittaker et al 2007). As a result, lower richness should occur on the newly formed as well as on the sinking and eroding late stage islands, whereas higher richness is expected in the middle-stage islands (Kraemer et al 2022, Whittaker et al 2017, Whittaker et al 2008. Likewise, endemism rate should decrease with the increase in extinction resulting from ontogenetic changes (Chen andHe 2009, Whittaker et al 2007).…”