EVOLUTIONARY DIVERSIFICATION OF AUSTRALIAN GALL-INDUCING THRIPS

Author: Michael John McLeish

McLeish, Michael John, 2007 EVOLUTIONARY DIVERSIFICATION OF AUSTRALIAN GALL-INDUCING THRIPS, Flinders University, School of Biological Sciences

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Abstract

This work further elucidates processes involved in promoting and sustaining evolutionary diversification within the gall-inducing thrips that specialise on Australian Acacia. A phylogenetic approach was taken to determine modes of diversification available to these insects. The extension and revision of the gall-thrips phylogeny is central to the work and primarily focuses on cryptic populations of the Kladothrips rugosus and Kladothrips waterhousei species complexes. Parallel diversification, where the radiation of the K. rugosus and K. waterhousei lineages broadly mirror one another, offered a rare opportunity to test hypotheses of coevolution between gall-thrips and their Acacia hosts. In the absence of a reliable host Acacia phylogeny, indirect inference of insect/plant cospeciation can be arrived at as these two complexes share the same set of host species. The expectation is that if the phylogenies for the gall-thrips complexes show a significant level of concordance, then cospeciation between insect and host-plant can be inferred. Results indicate that the K. rugosus species complex comprise populations at species level. A significant level of phylogenetic concordance between the two species complexes is consistent with gall-thrips lineages tracking the diversification of their Acacia hosts. Given the less than strict form of insect/host cospeciation, factors impacting host diversification become important to gall-thrips diversification. Gall-thrips radiated over a period during the expansion of the Australian arid-zone. Cycles of host range expansion and fragmentation during the Quaternary could have played a major role in gall-thrips diversity. An interesting feature of resourse sharing amongst the K. rugosus and K. waterhousei complex members is the apparent absence of competitive exclusion between them. The persistence of this sympatry over millions of years is an unusual feature and merits further investigation.

Keywords: Cryptic species,coevolution,cospeciation,diversification
Subject: Biological sciences thesis

Thesis type: Doctor of Philosophy
Completed: 2007
School: School of Biological Sciences
Supervisor: Associate Professor Michael P Schwarz