Courtney Schreiner, a student at the University of Idaho, collaborated with fellow REU student Taryn Waite, along with Nicole Solano, Dr. Courtney Murdock, and Dr. Craig Osenberg.
Abstract: We were interested in studying the effects of larval density on the fitness of the Asian tiger mosquito (Aedes albopictus). Aedes albopictus live all around Georgia and in various types of habitats that can support varying amounts of larvae. This creates competition which can effect downstream traits like fitness and disease transmission. Our experiment took place in a semi-field enclosure. We had 7 different larval density treatments that ranged from 5 to 240 larvae in each jar, for a total of 92 jars. Daily emergence, sex ratio and wing size were all recorded for all emerged mosquitoes. Overall we found that the proportion that survived, proportion female, fecundity, and wing size all decreased as density increased. We calculated the intrinsic growth rate using these estimates and found that lower densities have a higher intrinsic growth rate than those at lower densities. This told us that mosquitoes have a higher fitness at lower densities. Which also means that higher disease transmission would also be found in lower densities.
Taryn Waite, a student at Colby College, collaborated with REU student Courtney Schreiner, Nicole Solano, Dr. Craig Osenberg, and Dr. Courtney Murdock.
Conspecific density in larval habitats is an important factor affecting adult
fitness in Aedes albopictus mosquitoes, as it drives competition for
food and space. We conducted a larval density experiment wherein mason jars
containing leaf infusion and varying numbers of larvae were placed in a field
enclosure, developmental stage was recorded daily, and emerged adults were
collected. Nonlinear regressions were performed on the data for survival to
adulthood, sex ratio of adults, and wing length of females, and fecundity was
inferred from wing length. Using these regressions, an equation was created to
predict short-term population dynamics in habitats with varying conspecific
densities. What determines the densities that will actually occur in various
larval habitats is where females choose to lay their eggs. Female mosquitoes
have the ability to skip-oviposit, which entails spreading their eggs out among
multiple habitats instead of dumping them all in one habitat. The population
dynamics equation was used to evaluate the theoretical consequences of skip-
versus non-skip- oviposition, using scenarios with varying numbers of
egg-laying females and a fixed number of available larval habitats. We found
that at low densities of ovipositing females, skip-oviposition produces more
short-term population growth than non-skip-oviposition. At higher densities,
non-skipping becomes more productive than skipping, though there is less
divergence between the outcomes. This simulation demonstrates a way in which
patterns of density-dependence could act as a link between oviposition behavior
and population dynamics. Due to the effects that we found of density dependence
in larval habitats, individual females’ oviposition behavior could have
consequences for short-term population dynamics.