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Ecology of ants along elevational rainforest gradients in the tropics
MOSES, Jimmy
The thesis investigates the community ecology and species diversity of tropical ants on tropical mountains. The primary focus is on the changes in the ground-dwelling ant communities along elevational rainforest gradients, and how their elevational patterns are influenced by various biotic and abiotic factors. First, we investigated how elevation, leaf litter depth and their interaction affect the abundance, species richness and composition of ground-dwelling ants on Mt. Wilhelm (Papua New Guinea). Next, we investigated how ant communities change with forest succession in time along an extensive tropical elevational gradient in Southern Papua New Guinea. The aim was to assess both spatial and temporal trends in the ant communities and whether these changes could serve as indicators towards ecological recovery after human-induced forest disturbance. Finally, we assessed the relationships of ant species richness and activity, and their relative use of six nutrients, with elevation and season in three different tropical mountain regions (New Guinea,Tanzania and Ecuador).
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Why so specious? The role of pollinators and symbionts in plant population structure and speciation along elevational gradients.
SOUTO VILARÓS, Daniel
This thesis explores the role mutualist pollinators and their symbionts play in the genetic structuring and speciation of their host plants along an elevational gradient in Papua New Guinea. Using the fig and fig-wasp mutualism as a model system, we employed high-throughput sequencing techniques to explore fine-scale population genomics of both fig and wasps along their elevational range. We found there to be clear lowland and highland clustering of tree populations along the gradient, often with a mid-elevation contact zone. In the case of the pollinating wasps, we retrieved the same clustering except in this case, the genetic difference between clusters was high enough as to consider them as separate species. This result supports evidence from other studies challenging the cospeciation paradigm of one wasp species per fig species. In addition, we explore ecological traits which may promote, or at least, maintain, reproductive isolation between fig (sub)species along with behavioural preference tests from pollinating wasps. In order to further investigate the mechanisms promoting wasp speciation along the gradient, we describe Wolbachia infection status as well as strain type. Wolbachia-induced cytoplasmic incompatibility (CI) is often invoked as a possible speciation agent since it can rapidly provoke and maintain reproductive isolation between otherwise freely interbreeding insect populations. Finally, we explore non-pollinating fig wasp (NPFW) diversity along the gradient for a subset of our focal species. Our study reveals that there is a tight relationship between NPFW diversity and host species, and a mid-elevation peak.
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