No abstract

No abstract

Mosquito sugar-feeding and host-seeking rhythms were recorded in the laboratory using remote sensors. In all five species studied, the two rhythms were nearly synchronous. In Anopheles quadrimaculatus Say, Culex quinquefasciatus Say, and Aedes triseriatus (Say), host-seeking activity increased slightly earlier than sugar feeding in the evening. The evening sugar-feeding period was longer than the evening host-seeking period in Aedes aegypti (L.), but the two periods were of similar duration in Aedes albopictus (Skuse). In the morning, the only clear difference between the two behaviors occurred in Cx. quinquefasciatus, which had a host-seeking peak but lacked a sugar-feeding peak. When exposed concurrently to both host and sugar stimuli, sugar feeding practically ceased in Ae. albopictus and Ae. aegypti. In the presence of host stimuli, the sugar-feeding rhythms of An. quadrimaculatus, Cx. quinquefasciatus, and Ae. triseriatus differed from those obtained in the absence of host stimuli by having an earlier onset of evening activity, a relatively smaller evening activity peak, and a more irregular activity pattern during early scotophase, respectively. We concluded that inseminated, nulliparous females have nonspecific appetitive feeding periods, and that the order in which sugar and blood are sought largely may be a function of factors other than differences in diel rhythms.

No abstract

Ecological speciation via host-shifting is often invoked as a mechanism for insect diversification, but the relative importance of this process is poorly understood. The shift of Rhagoletis pomonella in the 1850s from the native downy hawthorn, Crataegus mollis, to introduced apple, Malus pumila, is a classic example of sympatric host race formation, a hypothesized early stage of ecological speciation. The accidental human-mediated introduction of R. pomonella into the Pacific Northwest (PNW) in the late-1970"s allows us to investigate how novel ecological opportunities may trigger divergent adaptation and host race formation on a rapid timescale. Since the introduction, the fly has spread in the PNW, where in addition to apple, it now infests native black hawthorn, C. douglasii, and introduced ornamental hawthorn, C. monogyna. We use this "natural experiment" to test for genetic differentiation among apple, black and ornamental hawthorn flies co-occurring at three sympatric sites. We report evidence that populations of all three host-associations are genetically differentiated at the local level, indicating that partial reproductive isolation has evolved in this novel habitat. Our results suggest that conditions suitable for initiating hostassociated divergence may be common in nature, allowing for the rapid evolution of new host races when ecological opportunity arises.