Parasitism and mating of Diaeretiella rapae (Hymenoptera: Aphidiidae) in an uncontrolled environment

Parasitism and mating activities of Diaeretiella rapae were studied in a shadehouse under ambient environmental conditions during September (early spring) and November (late spring). Before collecting the data, the parasitoid and its aphid host colonies were left to develop undisturbed on cabbage seedlings for 3 months in about 25 m2 area. The plants were highly infested with aphids (average 272±25 aphids/plant) and parasitism by D. rapae varied between 25% and 36% during the study period. There was no significant change in parasitism rate during the 10-week study period (P=0.69). Adult parasitoids emerged from aphid mummies at a rate of more than 90% with a higher number of females than males. The mean female/male parasitoid sex ratio was greater in the second 5-week (late spring) than the early 5-week period (early spring) (P<0.05). Mating activities of the parasitoids were observed at all times of the day. It was found that 49% of the mating pairs comprised a male mounted on a female and 45% were male mounted on another male. The male-female mating was more prevalent during midday compared to morning and evening (P<0.05)

Evolution of New Zealand's terrestrial fauna: a review of molecular evidence

New Zealand biogeography has been dominated by the knowledge that its geophysical history is continental in nature. The continental crust (Zealandia) from which New Zealand is formed broke from Gondwanaland ca 80 Ma, and there has existed a pervading view that the native biota is primarily a product of this long isolation. However, molecular studies of terrestrial animals and plants in New Zealand indicate that many taxa arrived since isolation of the land, and that diversification in most groups is relatively recent. This is consistent with evidence for species turnover from the fossil record, taxonomic affinity, tectonic evidence and observations of biological composition and interactions. Extinction, colonization and speciation have yielded a biota in New Zealand which is, in most respects, more like that of an oceanic archipelago than a continent

Contrasting response to Pleistocene climate change by ground-living and arboreal Mandarina snails from the oceanic Hahajima archipelago

While the genetic impact of Pleistocene climate change on temperate species has been well characterized, especially in Europe and North America, an effect on the diversification of species on oceanic islands has been less well studied. This is perhaps a surprising observation given the traditional and continuing contribution of island species (e.g. Darwin's finches, Partula snails, Lord Howe Island palms) to understand speciation. Here, we combine mitochondrial and microsatellite data from the ground-living and arboreal Mandarina snails of the oceanic, subtropical Hahajima archipelago (Ogasawara, colloquially ‘Galápagos of the Orient’) to enable a comparative approach to understand the impact of the Pleistocene glaciations on their phylogeography. Prior work suggested that several narrowly divergent, ground-living species pairs of Mandarina populations on the outlying islands, as well as the low-lying southern and central parts of Hahajima, probably underwent bottlenecks and subsequent expansions during the recent Pleistocene. Here, the most striking finding is that largely arboreal species have deeply divergent, geographically restricted mitochondrial lineages, in contrast to a census size that is at least an order of magnitude lower than ground-living snails. As populations of both types are highly polymorphic at microsatellite loci, the systematic difference at the mitochondrial locus probably indicates a contrasting effect of the Pleistocene climate cycles on the two groups. We speculate that this may have partly come about owing to a reduced efficacy of natural selection on the more greatly structured populations of arboreal snails. If so, then a prediction is that the genome of other snails, or other species with limited mobility, will show a similar response to the Pleistocene climate cycles

Biological invasions at the gene level

Despite several recent contributions of population and evolutionary biology to the rapidly developing field of invasion biology, integration is far from perfect. I argue here that invasion and native status are sometimes best discussed at the level of the gene rather than at the level of the species. This, and the need to consider both natural (e.g. postglacial) and human-induced invasions, suggests that a more integrative view of invasion biology is require