Molecular evidence for dispersal rather than vicariance as the origin of flightless insect species on the Chatham Islands, New Zealand

Abstract

AimThe aim was to use mitochondrial DNA sequence data to test between vicariance and oversea dispersal explanations for the origin of the Chatham Islands biota.Location New Zealand and the Chatham Islands, separated by c . 800 km in the south-west Pacific Ocean.Methods DNA sequences from the mitochondrial gene cytochrome oxidase I (COI) were obtained from four genera of relatively large and flightless insects (Coleoptera-Geodorcus , Mecodema ; Orthoptera-Talitropsis ; Blattoidea -Celatoblatta ). These were used to test alternative hypotheses for the origin of the Chatham taxa.Results Phylogenetic analysis revealed the Chatham taxa in each genus to be monophyletic. Genetic distances exhibited by these genera, between taxa found on the Chatham Islands and mainland New Zealand were relatively low (11.2, 2.8, 3.0 and 4.9%, respectively). Main conclusionsEven allowing for variation in molecular evolutionary rates, these genetic distances indicate phylogenetic separation of New Zealand and Chatham insect lineages in the Pliocene (2-6 Ma). Such dates are more than one order of magnitude too recent to be explained by vicariant (tectonic) processes. Oversea dispersal from New Zealand to the Chatham Islands is implicated and this conclusion is in keeping with the taxonomy of the endemic avifauna, flora and fossil molluscan fauna.

Molecular Insights Into the Biogeography and Species Status of New Zealand's Endemic Latrodectus Spider Species; L. Katipo and L. Atritus (Araneae, Theridiidae)

“…In the absence of datable fossil records, however, it is unlikely that the time L. katipo and L. atritus arrived in New Zealand will be precisely known. Overall, this lack of evidence for isolation between Australia and New Zealand since the Gondwanan break-up agrees with other recent studies of other New Zealand taxa, such as podocarp trees (Pole 1994), galaxiid fish (Waters et al 2000), hepialid moths (Brown et al 1999) and various flightless insects (Trewick 2000 (Stevens 1985;Stevens et al 1988;Nichols 2001;Trewick 2001). Moreover, Raven (1992) and Main (1992) suggested that L. hasselti may have only recently been introduced to eastern Australia from South Australia, which would explain the lack of genetic variation between the L. hasselti specimens.…”

Phylogeographic Structure and Cryptic Speciation in the Trans-Antarctic Moss Pyrrhobryum Mnioides

“…Molecular phylogenetic studies inferring dispersal in Australasia as a rule support eastward migration, from Australia to New Zealand, consistent with prevailing wind patterns (Waters and White 1997;Trewick 2000;Chambers et al 2001). In marked contrast, our ML analyses in P. mnioides suggest that the number of upwind migrants, from New Zealand to Australia, is nearly four times larger than the number of downwind migrants, from Australia to New Zealand.…”

New Caledonia: a very old Darwinian island?

“…the age of the more recent island. Trewick (2000) reported a similar case for New Zealand and the Chatham Islands. A contrary interpretation would require invoking either unknown or extinct mainland species closely related to those on the more recent islands, a presumption that prevents any further logical biogeographic reasoning.…”