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Ecology and evolution of ant communities in tropical ecosystems

Final Report Summary - ANT BIODIVERSITY (Ecology and evolution of ant communities in tropical ecosystems)

The aim of this project was to create a comprehensive data set which will allow studies of ecology and evolution of tropical ants at the community, species and population levels.
The specific objectives were
1) To examine how interactions between ants and other organisms affect the structure and diversity of species’ communities.
2) To reconstruct phylogenetic, phylogeographic and population relationship among selected ant taxa from Melanesia and South Pacific to assess the effects of geography, habitat and life history on the current patterns of species diversity.
3) To integrate morphology and DNA-based approaches to diversity inventories and develop resources for effective sharing of species information.
4) To implement novel methods for large-scale generating of molecular data for population and species level genetic studies.

Our results confirm that the diversity of ant species in Melanesia and South Pacific is higher than anticipated and that many species originally considered as widespread, may consist of closely related, cryptic species. Broadly speaking, our results can be divided in three spatial scales, communities, species and populations.
At the community level, we identified main drivers behind diversity of ant assemblages associated with different levels of habitat disturbance. We assessed the effects of succession-related determinants on arboreal ants, by conducting a complete census of ant nests from all trees 0,3-ha plots in primary and one secondary lowland forest in New Guinea. Our study shows that reduction in plant taxonomic diversity in secondary forests is not the main driver of the reduction in canopy ant species richness. The majority of arboreal species losses in secondary tropical forests are attributable to simpler vegetation structure and to lower turnover of nesting microhabitats between trees.
In a complementary study, we used a novel approach for manipulating local diversity of ants. We used treated canopy bait stations to exclude ants from the patches of lowland rainforest. Our study demonstrated that it is possible to selectively eradicate most of the foraging ants in a structurally complex tropical forest. We propose whole-forest manipulation as a novel tool for studying the role of ants in shaping plant–insect food webs.

We tested novel phylogenetic approaches to investigate interspecific interactions in ant communities along climatic gradients. We identified that in low altitudes ant communities in are mostly structured by competition among species, while at high elevations they are highly influenced by environmental filtering caused by low temperatures.

At the species level we used a novel regional dataset on ant species distribution, to analyze the scaling of exotic richness with area, native richness, and human impacts across tropical Pacific and Melanesian archipelagoes. We found exotic species richness as a single positive function of land area across scales, and evidence for a scale-specific biotic resistance effect operating on larger islands. The non-random patterns of exotic introductions have tightened the overall species-area relationship by mediating the effects of island isolation on species richness, indicating that exotic species are ‘filling’ empty regions of the species area curve.

By reconstructing phylogenetic relationships of ants from Camponotus maculatus-group, we identified novel dispersal pathways and revealed complex biogeographic scenarios in which different ant lineages colonized areas of Melanesia and South pacific. We identified the origin of endemic species from several isolated islands and described convergent changes in morphology and coloration in different phylogenetic lineages. This study provided us with new insights into the Eurasian-origin hypothesis of Melanesian species and described the degree of biogeographic heterogeneity on younger and more remote regions of the South Pacific.

At the population level, we reconstructed phylogeographic history of a widespread weaver ant Oecophylla smaragdina using a combination of DNA sequences and whole-genome SNP markers. The biogeographic reconstruction suggests ant dispersal from continental Asia into the islands of Sundaland and through Sulawesi to the New Guinea and Australia. Despite their broad distribution the Oriental and Australasian populations are surprisingly genetically differentiated from each other. In New Guinea, there is a clear differentiation between inland and coastal populations of weaver ant. These phylogeographic patterns suggest two independent colonizations of Australia and effective dispersal pathways along the coast of New Guinea.

In a complementary phylogeographic study of widely distributed ant Acropyga acutiventris we found quite a different pattern of population-genetic structuring. For populations distributed across a continuous lowland rainforest, we found the evidence of gene flow only in the populations situated less than 80 Km apart from each other. This is in contrast with the earlier assumptions that the common widespread species living in interconnected habitat will likely exhibit high migration rates among populations.

During the course of the whole project over 9.000 ant specimens representing over 700 species were processed. We assembled distributional data and generated molecular genetic data for over 5000 specimens. This information has been made available through several public databases, along with high-resolution photographic documentation. Two highly innovative methods for massive generating of molecular-genetic data for species and population level biodiversity studies along with a range of novel analytical approaches and programs for analysing molecular data were implemented in the laboratory of the returning researcher.

The Ant Diversity project and the scientific training provided by returning researcher resulted in successful participation of associated researchers and students in other scientific-educational activities, including research stays, training courses, conferences and seminars. New collaborations with researchers at Harvard University, Rockefeller University, American Museum of Natural History, Mexican Institute for Genomic and Biodiversity and with Okinawa Insitute of Techonology established by researcher during the outgoing phase of this fellowship led to the broad scientific collaborations, preparation of joint manuscripts and exchange of students.