Nov 11, 2018
Tyson researchers, Katie Westby and Lexie Beckermann, traveled to Vancouver, BC, Canada November 11-14 to present their research at the 2018 Joint Annual Meeting of the Entomological Society of America.
Dr. Katie Westby, a postdoc in the Medley lab at Tyson, presented her research on abundance patterns of Aedes albopictus along an urban to rural gradient in St. Louis. Lexie Beckermann, an undergraduate at Tyson in the Medley lab, presented her research about native mosquito and invasive mosquitos susceptibility to predation
Dr. Katie Westby:
Larval Aedes albopictus populations along an urban to rural gradient in Saint Louis, MO: Are abundance patterns related to differences in artificial larval habitat quality by land-use type?
As one of the most invasive species globally, Aedes albopictus (Skuse) has become a major nuisance species and, in some instances has displaced native mosquito species where it has invaded. In temperate North America, however, Ae. albopictus remains rare in forested and rural habitats. To explore this pattern, we monitored larval abundance of Ae. albopictus in 2017 and 2018 along an urban to rural land-use gradient in St. Louis, MO. We established four 900 mL black oviposition cups at multiple urban, suburban, and rural locations. We collected larvae and pupae from each cup weekly from May – September and returned them to the laboratory for identification. At the end of the surveillance period, we collected ovipostion cups and quantified water volume, total nitrogen, total tannins, and pH for each habitat. Ae. albopictus was significantly more abundant in urban and suburban habitats compared to rural habitats, and most abundant in suburban habitats. We also detected significant differences in water chemistry; total nitrogen was significantly higher in cups placed in rural habitats, pH was higher in urban cups and urban cups had significantly greater water loss compared to suburban and rural habitats. These data suggest that the types of larval habitats created along a land-use gradient do differ in some key components. These differences did not, however, relate to survival of an experimental cohort of Ae. albopictus added to the habitats in a follow up laboratory study nor was larval survival related to the land-use type the cup originated from.
Native mosquito's vulnerability to predation is reduced in the presence of invasive mosquito
Larvae of the predatory mosquito Toxorhynchites rutilus (Coquillet) consume other arthropods within discrete container habitats, including Aedes japonicus (Theobald) and Aedes triseriatus (Say). Vulnerability to predation by Tx. rutilus has been studied for both Ae. japonicus and Ae. triseriatus, but previous laboratory predation studies are conflicting on whether there are differences in vulnerability between these two species, and do not include important elements common in containers in the field such as habitat structure and chemical predation cues. To evaluate the impact of these factors on vulnerability to Tx. rutilus predation, we created laboratory microcosms with the following treatments: presence/absence of predator cues and presence/absence of habitat structure; and we created larval assemblages with three species combinations: Ae. japonicus larvae or Ae. triseriatus larvae alone, and both prey species together. We then added one Tx. rutilus to each microcosm and counted prey larvae every 24 h until no prey remained. In microcosms containing both prey species, Ae. japonicus was more vulnerable to predation than Ae. triseriatus; when reared separately, however, Ae. japonicus was less vulnerable to predation than Ae. triseriatus. Both species, held together or singly, were less likely to be preyed upon in the presence of predation cues. We detected no effect of habitat structure on prey vulnerability. These results clarify the nuances between the conflicting literature on the differences in prey vulnerability of Ae. japonicus and Ae. triseriatus to Tx. rutilus. Furthermore, these results suggest the presence of an invasive congener assists Ae. triseriatus by prolonging time to predation.