Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Beetle diversity in box-gum grassy woodlands : the importance of habitat heterogeneity at multiple scales

Auteur : Barton, Philip S.

Université de soutenance : Australian National University

Grade : Doctor of Philosophy (PhD) 2010

Résumé partiel
Insects are a critical part of ecosystems, and understanding the key drivers of insect diversity is essential for informed conservation management. I examined how habitat heterogeneity at different spatial scales affected ground-dwelling beetle diversity in a remnant of critically endangered box-gum grassy woodland in south-eastern Australia. I demonstrated how beetle assemblages were influenced by macrohabitat, where shrub cover was important, and by microhabitat, where open ground, logs and tree litter influenced assemblage diversity and composition. Further investigation of beetles from the litter layer revealed differences in species richness, composition, biomass and trophic structure under two dominant eucalypt species. Here, both eucalypt species and geographic distance were important factors influencing fine-scale beta diversity. I investigated beetle responses to the experimental manipulation of kangaroo grazing via large-scale exclosure fences, and the fine-scale addition of logs. Beetle species richness and abundance increased inside exclosures with reduced kangaroo grazing levels, with positive responses by herbivores and detritivores. Logs had additional positive effects inside the exclosures, and also provided a microhabitat refuge outside exclosures where grazing levels were high. I examined the morphological traits of a diverse beetle assemblage and demonstrated how this information can complement phylogenetic information to extend our understanding of their ecology. Three new morphological traits were described that were independent of body length and family-level phylogeny. Correlations between these traits and microhabitat use were only partially explained by family membership of beetle species, and further correlations were found between morphological traits and microhabitat use within four dominant families. This indicated that differences in morphology may have functional significance, and that microhabitat acts as an environmental filter influencing beetle community structure.

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