New data on the aphid (Hemiptera, Aphididae) fauna of New Caledonia: some new biosecurity threats in a biodiversity hotspot

Thirty-three species of aphids are now established in New Caledonia. All species appear to have been introduced accidentally by human activity in the last century. Here, 17 aphid species are recorded for the first time: Aphiseugeniae, Aphisglycines, Aphisodinae, Aulacorthumsolani, Brachycaudushelichrysi, Cerataphisorchidearum, Greenideapsidii, Hyperomyzuscarduellinus, Hysteroneurasetariae, Lipaphispseudobrassicae, Micromyzuskatoi, Myzusornatus, Pentaloniacaladii, Rhopalosiphumnymphaeae, Rhopalosiphumrufiabdominale, Schizaphisrotundiventris, and Tetraneurafusiformis. Thirteen more species are also more or less regularly intercepted at the borders through biosecurity surveys, without further establishment. This demonstrates that aphids represent a major biosecurity threat, including a threat as potential plant virus vectors. The reinforcement of biosecurity is a priority for such biodiversity hotspots, from the perspectives of both agriculture and the native environment. Prioritisation and promotion of local development of vegetable and fruit production, rather than their risky importation from abroad, is desirable. Such an approach also should be promoted and extended to other Pacific islands, which all share the lack of native aphid fauna and their associated plant disease vector risks.

A new approach for the identification of aphid vectors (Hemiptera: Aphididae) of potato virus Y

Potato virus Y (PVY) is one of the most economically important viruses affecting potato crops worldwide. PVY can be transmitted from potato to potato by several aphid species, most of which do not colonize the potato crop. New methods including preservation of viral RNA on stylets of aphids collected from yellow pan trap samples, polymerase chain reaction detection of PVY from the stylets of one aphid, and aphid identification using DNA barcoding were used to identify possible PVY vectors from field samples. In total, 65 aphid taxa were identified from the samples that tested positive for PVY. Among those, 45 taxa had never been evaluated for their ability to transmit PVY, and 7 were previously labeled as nonvectors. These results demonstrated that the list of PVY vectors is likely longer than previously reported and that most (if not all) species of aphids could be considered as potential vectors. This premise has important implications in the management of PVY in seed potato production.

Opportunities for improved risk assessments of exotic species in Canada using bioclimatic modeling

This paper briefly reviews the process of exotic pest risk assessments and presents some examples of emerging opportunities for spatial bioclimatic modeling of exotic species in Canada. This type of analysis can support risk assessments but does not replace the need for on-going high quality field-based observations to validate and update models. Bioclimatic analysis of several exotic pests is provided to illustrate both opportunities and limits. A link is demonstrated to the National Forest Inventory to characterize timber volumes at risk for one exotic species. 'Challenges' are both scientific and administrative. More accessible and current field survey data are required to improve models. Our experience is that for many exotic species, historical, and even current, data are not always digital or quality controlled for taxonomic identity and accurate geo-referencing. This inhibits their use for integrated spatial modeling applications.

Patterns of genetic diversity in the sumac gall aphid, Melaphis rhois

In contrast to prior work on aphids, which has focused on pest species, the present study involved the analysis of genetic diversity in Melaphis rhois, a species that employs sumac and moss as alternate hosts. The life cycle involves a spring migration to sumac, with each sexual female producing a single offspring, which elicits a gall and subsequently proliferates clonally within it. Allozyme surveys at 52 sites in Ontario and Quebec established the absence of migration among galls and indicated that this species shares the low level of genetic diversity found in pest aphids. Genotypic frequencies in local populations of M. rhois showed frequent heterozygote deficits, suggesting the prevalence of inbreeding. Gene frequency divergence among populations was exceptionally pronounced, providing further evidence that gene flow was restricted. The unusual genetic attributes of this species suggest the important interaction among host-plant characteristics and the dispersal ability of aphids and their genetic systems.Key words: aphid, Melaphis, parthenogenesis, allozyme, cyclic parthenogen.