 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. |
