Phylogenetic and functional trait-based community assembly within Pacific Cyrtandra (Gesneriaceae): Evidence for clustering at multiple spatial scales

Authors: Johnson, Melissa

Submitted to: Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2023
Publication Date: 5/4/2023
Citation: Johnson, M.A. 2023. Phylogenetic and functional trait-based community assembly within Pacific Cyrtandra (Gesneriaceae): Evidence for clustering at multiple spatial scales. Ecology and Evolution. https://doi.org/10.1002/ece3.10048.
DOI: https://doi.org/10.1002/ece3.10048

Interpretive Summary: This study suggests that Pacific Cyrtandra communities are not randomly assembled, and instead, that niche-based processes structure biodiversity at broad and fine spatial scales in diverse congeneric species assemblages. The observation of phylogenetic and phenotypic clustering within island and site communities suggests that trait-based patterns are reflective of evolutionary relatedness at both spatial scales. However, as with most recently published comparable studies, these results may be highly contingent on the choice of metrics used to assess community structure, the set of communities, and on the selection of functional traits. Studies that increase regional sampling in areas with high species diversity and incorporate estimates of abiotic variables associated with microhabitats would be needed to further address the underlying drivers of community assembly patterns described here.

Technical Abstract: 200 species of Cyrtandra, most of which are white-flowered woody shrubs that are single-island endemics. Within these island communities, multiple Cyrtandra species are commonly observed to occur sympatrically in wet forest understories, forming swarms of what appear to be ecologically similar taxa. The aim of this study was to determine if communities of these plants are randomly assembled with respect to phylogenetic relatedness and traits that are ecologically relevant. Using a combination of ten functional traits and a well-resolved species phylogeny, I examined community assembly within 34 species of Cyrtandra across three Pacific archipelagoes. Coexisting species were generally found to be more closely related and more phenotypically similar than would be expected by chance. This pattern was observed at both broad (island communities) and fine (site communities) spatial scales. The retention of phylogenetic signal in floral traits and the strong influence of these traits on the observed degree of phylogenetic clustering may indicate that pollinators act as a biotic filter for closely related species of Cyrtandra. In contrast, the absence of phylogenetic signal in most leaf traits, coupled with the lower contribution of these traits to niche clustering, suggests that environmental filtering along this trait axis is minimal in the observed communities. This study supports the theory that plant communities are not randomly assembled, and instead, that niche-based processes structure biodiversity at broad and fine spatial scales in diverse congeneric species assemblages.