The evolution of dung beetle assemblages
Author(s)
Inward., Daegan J. G.
Type
Thesis
Abstract
Dung beetles (Scarabaeinae) are a well studied group, not least because of their clearly defined taxonomic and ecological boundaries. The majority of preceding studies have taken a limited local-level view of dung beetle systems, where local species interactions have been assumed to play the main role in structuring assemblages. Many other generally accepted hypotheses regarding scarabaeine evolution also remain untested. This includes the notion that the two main functional nesting groups, the rollers and the tunnellers, are monophyletic sister taxa. This is the first study to investigate the processes acting upon assemblage structure at both local and regional levels, using a number of different approaches, including molecular phylogenetics and analyses of functional diversity and ecomorphology. Based on sequence information from three gene regions (COI, 16S rRNA, and 28S rRNA) and 200 taxa, the molecular phylogenetic hypothesis suggested rolling and tunnelling each originated on multiple occasions in the Scarabaeinae, and that significant parts of the higher level taxonomy of the group were misleading. Perhaps most importantly, the phylogeny was seen to be closely associated with continental biogeographic history. Using morphometric techniques, dung beetle assemblages were characterised by the gross functional morphology of their component species, and compared within and across regions. Whilst species richness of assemblages was seen to influence species packing, the total area of ecomorphological space (niches) occupied remained consistent. Functional groups were clearly separated from each other in morphospace, and were seen to be largely constrained by phylogenetic ancestry. However, convergence in function was seen to be accompanied by convergence in morphology where strong environmental pressures or ecological opportunity prevailed. Small-scale species interactions were seen to be of lesser importance in structuring assemblages than large-scale historical processes. Within regions, habitat was the main driver, but across regions, phylogenetic history was the key structuring force.
Version
Open Access
Date Awarded
2003
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Vogler, Alfried
Publisher Department
Department of Life Sciences
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)