The International Biogeography Society is excited to announce the IBS 2021 Dissertation Awardee:

 

Antonia Salces-Castellano

 

Spanish National Research Council / University of La Laguna

 

Dissertation committee members:
Sara Varela, Jean-Philippe Lessard and Rute Andreia Rodrigues da Fonseca.
Chaired by Julia Heinen, IBS Student-at-large

Spatial structure of biodiversity:
Local and regional patterns in an insular ecosystem

Synopsis

What forces drive the origin and maintenance of biodiversity?
This is a central question in biology, and an important challenge, particularly in oceanic islands, which harbour singular and threatened biodiversity. Within island biodiversity, arthropods are an ecologically important group but typically with only limited biological data. The present dissertation contributes to our understanding of insect biodiversity in oceanic islands through two core objectives: (i) describe spatial and temporal patterns of relatedness and similarity (from the level of genetic diversity through to community assemblages), and (ii) identify the variables and processes that shape diversity, focusing on non-adaptive evolutionary pathways to speciation. Using an integrative approach combining genomic, geographical, ecological and historical data, in a metaphylogeographic framework (i.e. multiple species are simultaneously analysed at intra- and interspecific levels), I have been able to explore important drivers of species diversification in an insular context, such as dispersal limitation, topography, climatic variation, and niche conservatism, acting at multiple spatial scales. Within the first dissertation chapter (Salces-Castellano et al. 2021A, Proceedings of the Royal Society), dispersal limitation, specifically flightlessness, is demonstrated to be an important driver promoting the structuring of beetle communities, and diversification of beetle lineages within the Canary Islands. At the archipelago scale, this is mainly due to isolation by resistance induced by oceanic barriers. Within islands, and at a very limited spatial scale, the thesis work identified an interaction of topography and local climatic variation as the main driver for a shared pattern of geographic isolation by niche conservatism across an unprecedented number of codistributed species within a cloud forest ecosystem. The data suggested this pattern to be potentially derived from a dynamic of isolation and secondary contact over Quaternary climatic cycles, pointing to a shared evolutionary dynamic acting across entire communities (second dissertation chapter, Salces-Castellano et al. 2020, Ecology Letters). In the third dissertation chapter (Salces-Castellano et al. 2021b, Evolution), a novel framework for testing among competing demographic models across a hybrid zone is described, in which genomic data from a species of beetle restricted to montane cloud forest is used to determine how its habitat responds to climate change. The results provide support for a Quaternary model of montane cloud forest dynamics that has not been considered in previous evolutionary and ecological analyses, pointing to a downward drift of the montane cloud forest under global warming. Overall, the three chapters fit together to compose a novel and integrative dissertation, exploring multiple layers of diversity within an ecological and evolutionary framework to understand what generates and structures diversity within insular insect biotas.

References

Salces-Castellano A, et al. 2020. Climate drives community-wide divergence within species over a limited spatial scale: evidence from an oceanic island. Ecology Letters 23:305–315. doi:10.1111/ele.13433.

Salces-Castellano A, et al. 2021a. Flightlessness in insects enhances diversification and determines assemblage structure across whole communities. Proceedings of The Royal Society B. 288(1945): 20202646. doi:10.1098/rspb.2020.2646.

Salces-Castellano A, et al. 2021b. Long-term cloud forest response to climate warming revealed by insect speciation history. Evolution: 75(2):231-244. doi:10.1111/evo.14111.

 

Statement of significance

The present dissertation highlights the power of combining community level sampling with genomic and environmental data to understand general principles of how dispersal, niche, climate and landscape interact to shape biodiversity pattern. It achieves this through the application of novel methods to provide robust results and defendable integrative insights for the otherwise poorly understood invertebrate diversity of oceanic islands, delivering a timely contribution pushing forward the frontiers of knowledge in island biogeography. A standardized protocol for the molecular inventory of arthropod diversity is developed and implemented, removing otherwise complicating taxonomic impediments, and leading to an effective quantification of complete insect assemblages at the genetic level. The community-wide genetic (and genomic) data generated is exploited using a novel framework of metaphylogeography to explore archipelago and intra-island level processes governing diversification in the insect fauna. The results demonstrate the important role of flightlessness for both species diversification and community structure within island insects, and reveal a prevalent role of non-adaptive evolutionary pathways to speciation, with unprecedented results relating microclimatic variation during the Quaternary periods as one of the main drivers of species diversification within islands, at very small spatial scales. The results also provide support for a Quaternary model of montane cloud forest dynamics that has not been previously proposed, pointing to downslope shifts of montane cloud forests under global warming with important conservational implications for this habitat type globally, and the regionally endemic biotas that characterise them.

Links to the dissertation chapters