Evolutionary divergence of lineages is one of the key mechanisms underpinning large scale
patterns in biogeography and biodiversity. Island systems have been highly influential in shaping
theories of evolutionary diversification and here I use the insular Zosteropidae of the south west
Pacific to investigate the roles of ecology and biogeography in promoting evolutionary
divergence.
Initially I build a phylogenetic tree of the study group and use it to reveal the pattern of
colonisation and diversification. My results suggest a complex history of dispersal with the
observed pattern most likely a result of repeated bouts of colonisation and extinction. I then use
the new phylogeny to quantify the diversification rates of the Zosteropidae. I find a very high rate
of lineage divergence and suggest the most likely explanation relates to extensive niche
availability in the south west Pacific. I also find evidence for an overall slowdown in diversification
combined with repeated bursts of accelerated speciation, consistent with a model of taxon
cycles. I do not find evidence for sympatric speciation, however. Finally I combine morphological
and phylogenetic data to investigate the mode of evolution, evidence for character displacement
and influence of biogeography on trait evolution. I find little support for the traditional theory of
character displacement in sympatric species. I do, however, find some support for biogeographic
theories.
Taken together my results do not support traditional theories on the ecological and
biogeographical basis of divergence, even in those cases where Zosterops have been used as
exemplars. This appears to be because those theories assume rather simple patterns of
colonisation and a static ecological system. Instead, my results suggest that evolutionary
diversification is dominated by recurrent waves of colonisation and extinction, which, viewed at
any particular moment, tend to obscure any underlying ecological rules
