Evolution and diversification of ants

Ants (Hymenoptera: Formicidae) are amongst the most ecologically successful organisms with over 11,000 known species in 20 subfamilies originating 115-170 million years ago. Recent work has advanced our understanding of the evolutionary relationships of this group, giving us a greater appreciation of the evolution of ant social structures, life histories and threats. Despite this research, fundamental questions about ant evolution remain. This PhD project uses phylogenetic comparative methods to address fundamental macroevolutionary and macroecological questions within this group. The student will collate data on ant phylogenetic histories to produce the first ant 'supertree', along with data on social structures, life histories, geographic distributions and threats. These data will be used to test the hypotheses within the following objectives: Objective 1: To quantify the diversification rate shifts in the supertree to identify when the major diversification shifts have occurred in ants and which taxa are particularly responsible. We will test the hypotheses that (1) a more complete phylogeny will not alter the diversification shift at 60-100 MYA detected in ants by a previous study using an incomplete tree, and (2) ant subfamilies which are species-rich (e.g., Myrmicinae, Formicinae and Dolichoderinae) have experienced significant independent shifts in diversification rate which are independent of diversification rate shifts in other parts of the phylogeny. Objective 2: To quantify the factors responsible for the diversification rate shifts identified. We will test the hypothesis that (3) a correlate of species diversification is the degree of, or nature of, caste differentiation. Ants show a large range of caste structures, with variation in the degree of morphological differentiation both between queen and workers and among workers. This hypothesis posits that such diversity is correlated with ecological and evolutionary success at the colony level and thence at the level of species diversification. Objective 3: To determine the distribution and determinants of ant spatial biodiversity and how to prioritise conservation effort most effectively. We will test the hypotheses that (4) areas of ant species-richness and threatened species-richness and associated ecological and environmental determinants are similar to those of other groups, (5) current protected areas adequately conserve ant species-richness and threatened species-richness 'hotspots', and (6) EDGE ant species are not different to those identified as threatened by IUCN, and current IUCN rankings adequately protect ant evolutionary history. As regards Hypothesis 6, ants are cornerstone species in many ecosystems providing a number of essential ecosystem services. By understanding the processes determining their distributions, we can provide priorities for where conservation effort should be focused. We will provide new priorities for species-based conservation efforts by combining IUCN rankings with phylogenetic distinctiveness to create a list of Evolutionary Distinct and Globally Endangered (EDGE) ants fitting into current ZSL-led priority schemes (www.edgeofexistence.org).