1. Ecological specialisation is an important mechanism enhancing species coexistence within a given community. Yet, unravelling the effect of multiple selective evolutionary and ecological factors leading the process of specialisation remains a key challenge in ecology. Subterranean habitats provide highly replicated experimental arenas in which to disentangle the relative contribution of evolutionary history (convergent evolution vs character displacement) and ecological setting (environmental filtering vs competitive exclusion) in driving community assembly.
2. We tested alternative hypotheses about the emergence of ecological specialisation using the radiation of a lineage of sheet-weaver cave-dwelling spiders as model system. We observed that at the local scale, a differential specialisation to cave microhabitats generally parallels moderate levels of morphological similarity and close phylogenetic relatedness among species. Conversely, geographic distance contributed little in explaining microhabitat occupation, possibly mirroring a limited role of competitive exclusion. Yet, compared to non-coexisting species, co-occurring species adapted to different microhabitats showed lower morphological niche overlap (i.e. higher dissimilarity) and deeper genetic distance.
3. The framework here developed suggests that in the subterranean domain, habitat specialisation is primarily driven by environmental filtering, secondarily by convergent evolution, and only marginally by character displacement or competitive exclusion. This pattern results in the establishment of replicated communities across geographical space, composed by ecologically equivalent species. Such process of community assembly well explains the numerous adaptive radiations observed in subterranean habitats, an eco-evolutionary pattern well documented in oceanic islands or mountain summit communities.
Data and R script associated with this publication:
Mammola S, Arnedo MA, Fišer C, Cardoso P, Dejanaz AJ, Isaia M. (2020) Environmental filtering and convergent evolution determine the ecological specialisation of subterranean spiders. Functional Ecology.
- db_traits.csv (tab-delimited file containing morphological measures on the spiders)
- db_coord.csv (geographic coordinates of the different species)
- pruned_tree.phy (pruned phylogenetic tree used to calculate patristic distances between species)
- altitude.tif (Altitudinal raster needed for calculating altitudinal range overlap)
- Analyses_Code.R (R script to generate the analyses)
Please refer to the main publication for further details.
Compagnia di San Paolo, Award: Bando per l’Internazionalizzazione della Ricerca – Anno 2018
Compagnia di San Paolo, Award: CSTO162355
University of Turin, Award: CSTO162355
Spanish Ministry of Economy and Competitivity, Award: CGL2016-80651-P
Catalan Government, Award: 2017SGR83
Slovenian Research Agency, Award: Programme P1-0184