Understanding the mechanisms of adaptation to spatiotemporal environmental variation is a fundamental goal of evolutionary biology. This issue also has important implications for anticipating biological responses to contemporary climate warming and determining the processes by which invasive species are able to spread rapidly across broad geographic ranges. Here, we compare data from a historical study of latitudinal variation in photoperiodic response among Japanese and U.S. populations of the invasive Asian tiger mosquito Aedes albopictus with contemporary data obtained using comparable methods. Our results demonstrated rapid adaptive evolution of the photoperiodic response during invasion and range expansion across ∼15° of latitude in the United States. In contrast to the photoperiodic response, size-based morphological traits implicated in climatic adaptation in a wide range of other insects did not show evidence of adaptive variation in Ae. albopictus across either the U.S. (invasive) or Japanese (native) range. These results show that photoperiodism has been an important adaptation to climatic variation across the U.S. range of Ae. albopictus and, in conjunction with previous studies, strongly implicate the photoperiodic control of seasonal development as a critical evolutionary response to ongoing contemporary climate change. These results also emphasize that photoperiodism warrants increased attention in studies of the evolution of invasive species.

Introduction of potential disease vectors into a new geographic area poses health risks to local human, livestock, and wildlife populations. It is therefore important to gain understanding of the dynamics of these invasions, in particular its sources, modes of spread after the introduction, and vectorial potential. We studied the population genetics of Aedes (Finlaya) japonicus japonicus (Theobald), an Asian mosquito that was recognized for the first time in the United States in 1998. We examined patterns of genetic diversity using random amplified polymorphic DNA and sequences of ND4 of mtDNA by comparing samples from populations spanning the range of this mosquito in Japan (six samples) and the United States (nine samples) as well as specimens intercepted in New Zealand in 1999. We found geographically differentiated populations in Japan, indicating limited gene flow even on small spatial scales. In the United States, we found evidence of significant genetic differentiation between samples from New York, Connecticut, and New Jersey and those from mid-Pennsylvania and Maryland. We were unable to pinpoint the source location(s) in Japan, although some of the U.S. samples are genetically close to samples from south Honshu and western Kyushu. Further studies should include samples from Korean populations. Distinct genetic signatures in U.S. populations undergoing expansion suggest the possibility of local increases in genetic diversity if and where they meet.

We used two mitochondrial loci (nicotinamide adenine dinucleotide dehydrogenase subunit 4 and cytochrome oxidase II) and a nuclear locus (28S-D2 spacer) for a total of 1337 bp to evaluate the relationships among the four subspecies of Aedes (Finlaya) japonicus Theobald. Ae. j. japonicus was recently introduced into the United States and has been expanding rapidly. We also included in our analysis a morphologically very closely related species, Aedes (Finlaya) koreicus Edwards, as well as three more distantly related species: Aedes (Finlaya) togoi Theobald, Aedes (Finlaya) hatorii Yamada, and Aedes (Aedimorphus) vexans Meigen. We found that the four subspecies in the Ae. japonicus complex are genetically quite distinct but seem to form a monophyletic group that surprisingly also includes Ae. koreicus, suggesting the need for a taxonomic reconsideration of the group. We also found that the two southern subspecies are more closely related to each other than to any of the remaining subspecies or to Ae. koreicus and may indicate an ancient north-south split of the lineage. Considering the overlap between Ae. j. japonicus and Ae. koreicus, but the stronger association between Ae. koreicus and humans, we are surprised it also has not expanded from its original range. As a proactive reaction to this possibility, we designed and tested a DNA-based rapid assay to differentiate Ae. koreicus from some of the species with which it may be confused in the United States. These Aedes are putative vectors of several important viral encephalitides.

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To determine the host-feeding patterns of mosquitoes, blood-fed mosquitoes were collected by 5 di#erent methods from various places such as mountain forests, residential areas and animal sheds of the following 5 islands, Amamioshima, Tokunoshima, Iheyajima, Okinawajima and Iriomotejima in the Ryukyu Archipelago, Japan over a 6 yr period (2005ῌ2010). A total of 975 bloodmeals derived from bloodfed mosquitoes of 35 species representing 11 genera were successfully identified by a polymerase chain reaction (PCR) based method, and 34 vertebrate species were identified as the bloodmeal hosts. Our results indicate that mosquitoes of the same genus show similar host preferences when blood source animals are classified into 5 major groups; mammals, birds, reptiles, amphibians and fishes. The genus Anopheles exhibited mammalophilic and Aedes exhibited mammalophilic, but Ae. (Geoskusea) baisasi Knight and Hull fed predominantly on fishes. Host preferences of the genus Culex were somewhat di#erent among subgenera. Subgenus Culex fed on warmblooded animals, including mammals and birds, whereas other subgenera fed on various hosts both warm-blooded and cold-blooded animals. The Uranotaenia species were amphibian-feeders and also fed on reptiles and fishes, but not on warm-blooded animals. Medical importance of mosquito species is discussed as related to their feeding patterns and transmission of mosquito-borne diseases.

Culicid and Chaoborid flies (Diptera: Culicidae and Chaoboridae) attracted to a CDC miniature frog call trap at Iriomote Island,

Abstract:e utility of cytochrome c oxidase subunit I (COI) DNA barcoding for the identi cation of 37 mosquito species belonging to the genera Anopheles (6 spp.), Aedes (14 spp.) and Culex (17 spp.) including subspecies from nine islands of the Ryukyu Archipelago, Japan was examined. A 658 bp fragment of the COI gene was sequenced from 228 specimens. Nucleotide sequence divergences were calculated using the Kimura-two parameter (K2P) distance model and a neighbor-joining (NJ) phylogenetic tree analysis was performed to provide a graphic display of the patterns in divergence among species. e mean intraspeci c variations of 35 species including the medically important vector species showed a less than 2 range with 0 1.5 divergences, but higher divergences of more than 2 were detected in Ae. aureostriatus okinawanus Bohart (2.2 ) and Cx. hayashii ryukyuanus Tanaka et al. (3.3 ). ey showed di erences in divergence between specimens from di erent islands. All 37 species were discriminated as distinct clusters in the NJ tree. e results in this study prove the utility of DNA barcoding for identi cation of mosquitoes from the Ryukyu Archipelago, Japan.