[PhD Thesis Presentation] - Liu Cong - Understanding the ecological and evolutionary processes shaping ant biodiversity across spatiotemporal scales

Title: Understanding the ecological and evolutionary processes shaping ant biodiversity across spatiotemporal scales

Speaker: Liu Cong

Affiliation: PhD Student - Biodiversity and Biocomplexity Unit (Economo Unit)

Abstract:

Ecological and historical evolutionary processes together generate biodiversity patterns across geographies and across the tree of life. However, understanding the relative importance of, and the interplay between ecological mechanisms and evolutionary processes in shaping biodiversity patterns is still a challenge due to the different spatiotemporal scales on which they are operating. Therefore, a fundamental goal of biodiversity research is to use different research approaches to investigate how the ecological processes (dispersal, competition, and environmental filtering), as well as long-term evolutionary processes (adaptation and speciation), contribute to the community assembly and biodiversity patterns. In this thesis, I investigate ant biodiversity patterns and underlying eco-evolutionary processes across multiple systems (tropical agroecosystem, complex mountainous landscape, and Pacific archipelago), providing a comparative framework to understand the eco-evolutionary processes driving biodiversity patterns. I first present results from an ant biodiversity survey in Xishuangbanna, Yunnan, China, where I found 213 species/morphospecies of ants from 10 subfamilies and 61 genera. Forty species represent new records for Yunnan province and 17 species are newly recorded for China. In addition, I describe one new species, Aenictus yangi. When examining the changes in taxonomic, functional, and phylogenetic ant biodiversity after conversion to rubber plantation, I found a sharp decline of species richness in rubber plantation with lower than expected taxonomic and functional beta diversity. This suggested a strong environmental filtering driving ant biodiversity in the rubber plantation. I then investigate the variation in taxonomic and phylogenetic ant diversity patterns along a geographic transect spanning 5000m in elevational range in the Hengduan mountains, where environmental gradients and spatial connectivity are intertwined as a complex process that might shape biodiversity patterns. I found that environmental gradients dominate variation in both alpha and beta diversity in this landscape, with alpha diversity strongly declining with elevation and beta diversity driven by elevational differences. Finally, I apply a comparative phylogeographic framework to examine the evolution of the hyperdiverse ant genus Strumigenys in Fiji archipelago using RAD sequencing. My results revealed the history of Strumigenys species that colonized to Fiji archipelagoes in Miocene (10.5-7.5 Ma), following by two independent radiations across the whole archipelago, leading to the emergence of 11 endemic species. The population structure and demographic history of each endemic species consistently support the idea of deterministic macroevolutionary processes that drive the diversity dynamic of ants in Fiji archipelago. Together, this study highlights the need for a pluralistic framework that integrates different approaches to understanding the eco-evolutionary drivers of biodiversity patterns across scales.