Australian Termite Diversity
Open AccessThere are over 3000 species of termites across the globe with the greatest diversity and abundance in tropical regions. Termite species perform important ecosystem services such as nutrient cycling, breaking down materials and soil loosening, as well as feeding on a variety of substrates. Despite their global distribution, each biogeographic region has a distinctive composition of termites with resulting consequences for ecosystems. In Australia, there are over 300 species of termites with distributions that have been shaped by vicariance, human actions, and oceanic dispersal. Yet there are many termites groups, such as soil-feeding termites and fungus-farming termites, that are not present in Australia. In this dissertation, I investigate patterns of termite diversity in Australia at three different scales, and possible causes and consequences of these patterns. First, I compared termite assemblages across a precipitation gradient in the tropics of North Queensland, Australia. I found that termite mound presence and wood activity decreases with an increase in rainfall, and scarcity of termites in rainforest systems provides evidence for the Australian termite diversity anomaly. Feeding group diversity is also tied to precipitation, with savanna termites feeding on wood, litter, grass, dung and soil, while rainforest termites are limited to feeding on wood. This finding suggests that termites may be limited as decomposers in Australian rainforests. Next, I investigated how the Australian termite communities assembled through phylogenetic and evolutionary trait transition analysis. I found that termites have likely transitioned to or from Australia at least 26 times with the highest transition rates from termite species that already had widespread distributions. However, termite transitions out of Australia are more common than termite transitions to Australia. I also tested the “rafting colony” hypothesis, that all Australian Termitidae are descendants of wood-feeding termites that rafted across the ocean in their food-homes. I found that transitions to Australia were highest from wood-feeding termites, but that grass, litter and soil-feeding termites likely originated from generalist or wood/soil-feeding termites. These findings show that ancestral feeding group is an important predictor of current species distributions. Finally, I analyzed the diversity present in termite gut microbiomes. Microbial communities within termite guts are essential to their ability to decompose lignocellulose substrates, and are affected by host evolutionary relationships and feeding. However, the effect of environmental factors on termite gut microbiome has not been analyzed. I performed 16S amplicon sequencing and analysis on the gut microbiomes of five species of termites across space and habitat types. I found that gut microbial communities shift across geographic space, but the response varies by host species. Together these findings provide insights into the diversity and community assembly of Australian termites and their effects on ecosystem processes.
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