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UBC Theses and Dissertations

Multiple metrics of community structure and beta diversity inform investigations of community assembly in two Afromontane systems Krochuk, Billi Ann


The montane tropics harbour some of the most biodiverse bird communities globally. However, many remain poorly understood, particularly those in Africa. As such, the role of different mechanisms in driving patterns of community structure and beta diversity remain unclear. Mountains provide a unique opportunity to study the interplay between drivers due to the rapid changes in climatic conditions that take place along elevational gradients. Here, I examined how the structure and beta diversity of bird communities changed within two montane parks in the Albertine Rift, which spanned different elevations, to evaluate the strength of abiotic and biotic drivers of community assembly. I quantified and evaluated patterns of taxonomic, functional, and phylogenetic beta diversity in addition to metrics of functional and phylogenetic structure. Taxonomic beta diversity was driven by turnover in both locations and appeared to be between closely related, functionally similar species; this suggests biotic interactions were important for driving changes in composition. Biotic interactions are also likely important for structuring functional diversity communities in the lower elevation park, as indicated by high functional evenness across the gradient. However, abiotic conditions also appeared to be important for driving changes in the functional composition communities as functional beta diversity was driven by richness differences, with functional richness also declining as elevation increased in both parks. In addition, communities in both parks became progressively more compositionally similar as elevation increased, with evidence of the effective niche space becoming constrained, particularly in the higher elevation park, likely due to harsh abiotic conditions. This study underscores the importance of both abiotic conditions and biotic interactions for shaping tropical montane bird communities. As patterns observed in some metrics quantified here depart from those observed elsewhere in the tropics, this work further highlights the importance of studying multiple systems to broaden our understanding of pantropical community assembly.

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