Geographic isolation drives speciation in Nearctic aphids.

Across herbivorous insect clades, species richness and host-use diversity tend to positively covary. This could be because host-use divergence drives speciation, or because it raises the ecological limits on species richness. To evaluate these hypotheses, we performed phylogenetic path model analyses of the species diversity of Nearctic aphids. Here, we show that variation in the species richness of aphid clades is caused mainly by host-use divergence, whereas variation in speciation rates is caused more by divergence in non-host-related niche variables. Aphid speciation is affected by both the evolution of host and non-host-related niche components, but the former is largely caused by the latter. Thus, our analyses suggest that host-use divergence can both raise the ecological limits on species richness and drive speciation, although in the latter case, host-use divergence tends to be a step along the causal path leading from non-host-related niche evolution to speciation.

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: Aphis eugeniae, Aphis glycines, Aphis odinae, Aulacorthum solani, Brachycaudus helichrysi, Cerataphis orchidearum, Greenidea psidii, Hyperomyzus carduellinus, Hysteroneura setariae, Lipaphis pseudobrassicae, Micromyzus katoi, Myzus ornatus, Pentalonia caladii, Rhopalosiphum nymphaeae, Rhopalosiphum rufiabdominale, Schizaphis rotundiventris, and Tetraneura fusiformis. 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.

RésuméTrente trois (33) espèces de pucerons sont aujourd'hui recensées de Nouvelle-Calédonie. Toutes ces espèces sont exotiques et ont été introduites accidentellement par les activités humaines. Dix-sept (17) espèces y sont ainsi recensées pour la première fois : Aphis eugeniae, Aphis glycines, Aphis odinae, Aulacorthum solani, Brachycaudus helichrysi, Cerataphis orchidearum, Greenidea psidii, Hyperomyzus carduellinus, Hysteroneura setariae, Lipaphis pseudobrassicae, Micromyzus katoi, Myzus ornatus, Pentalonia caladii, Rhopalosiphum nymphaeae, Rhopalosiphum rufiabdominale, Schizaphis rotundiventris et Tetraneura fusiformis. Par ailleurs, au moins 13 autres espèces sont régulièrement interceptées par la biosécurité sans établissement actuel de populations. Les pucerons apparaissent donc comme une menace croissante pour la biosécurité de l'archipel. Aussi, le renforcement des mesures de biosécurité aux frontières apparaît prioritaire en association à une promotion du développement local de productions maraîchères et fruitières. Ainsi, la limitation de ces importations à risque, devrait contribuer à une meilleure protection des productions agricoles et de la biodiversité. Une telle approche devrait également être promue dans les pays insulaires du Pacifique, qui se caractérisent par la même disharmonie de peuplements, l'absence de communautés natives de pucerons et du risque associé de vectorisation de maladies phytopathogènes.

DNA barcodes for Nearctic Auchenorrhyncha (Insecta: Hemiptera).

BACKGROUND: Many studies have shown the suitability of sequence variation in the 5' region of the mitochondrial cytochrome c oxidase I (COI) gene as a DNA barcode for the identification of species in a wide range of animal groups. We examined 471 species in 147 genera of Hemiptera: Auchenorrhyncha drawn from specimens in the Canadian National Collection of Insects to assess the effectiveness of DNA barcoding in this group. METHODOLOGY/PRINCIPAL FINDINGS: Analysis of the COI gene revealed less than 2% intra-specific divergence in 93% of the taxa examined, while minimum interspecific distances exceeded 2% in 70% of congeneric species pairs. Although most species are characterized by a distinct sequence cluster, sequences for members of many groups of closely related species either shared sequences or showed close similarity, with 25% of species separated from their nearest neighbor by less than 1%. CONCLUSIONS/SIGNIFICANCE: This study, although preliminary, provides DNA barcodes for about 8% of the species of this hemipteran suborder found in North America north of Mexico. Barcodes can enable the identification of many species of Auchenorrhyncha, but members of some species groups cannot be discriminated. Future use of DNA barcodes in regulatory, pest management, and environmental applications will be possible as the barcode library for Auchenorrhyncha expands to include more species and broader geographic coverage.

Barcoding bugs: DNA-based identification of the true bugs (Insecta: Hemiptera: Heteroptera).

BACKGROUND: DNA barcoding, the analysis of sequence variation in the 5' region of the mitochondrial cytochrome c oxidase I (COI) gene, has been shown to provide an efficient method for the identification of species in a wide range of animal taxa. In order to assess the effectiveness of barcodes in the discrimination of Heteroptera, we examined 344 species belonging to 178 genera, drawn from specimens in the Canadian National Collection of Insects. METHODOLOGY/PRINCIPAL FINDINGS: Analysis of the COI gene revealed less than 2% intra-specific divergence in 90% of the taxa examined, while minimum interspecific distances exceeded 3% in 77% of congeneric species pairs. Instances where barcodes fail to distinguish species represented clusters of morphologically similar species, except one case of barcode identity between species in different genera. Several instances of deep intraspecific divergence were detected suggesting possible cryptic species. CONCLUSIONS/SIGNIFICANCE: Although this analysis encompasses 0.8% of the described global fauna, our results indicate that DNA barcodes will aid the identification of Heteroptera. This advance will be useful in pest management, regulatory and environmental applications and will also reveal species that require further taxonomic research.