2017 ESA Annual Meeting (August 6 -- 11)

COS 122-1 - Linking omnivore habitat selection to diet-mediated performance

Thursday, August 10, 2017: 8:00 AM
D133-134, Oregon Convention Center
Shelby A. Rinehart1,2 and Jeremy D. Long2, (1)Evolution and Ecology, University of California, Davis, Davis, CA, (2)Biology, San Diego State University, San Diego, CA
Background/Question/Methods

Omnivores should aggregate to habitats containing prey and non-prey resources (e.g. plant-provided

foods) that promote their performance. Despite support for this prediction, we lack studies linking

omnivore patch preference in the field, to tangible fitness benefits. This is particularly true for natural

systems, as most studies of omnivory have been conducted in artificial agricultural systems. Here we

assessed the aggregation patterns of an omnivorous salt marsh ladybeetle under field conditions to habitat

patches varying in prey (scale insects) and non-prey (cordgrass pollen) resources. Additionally, we tested

the role of olfactory perception of scale insect-infested cordgrass by ladybeetles in mediating habitat

selection over small spatial scales. We then tested the consequences of habitat selection to ladybeetle fitness

by rearing adult ladybeetles in the laboratory on several separate diets and tracked longevity, egg

production, and larval production. Similarly, we reared larval ladybeetles on the same selection of diets

and tracked larval longevity in response to individual and maternal diet.

Results/Conclusions

Adult ladybeetles preferentially aggregated to habitat patches containing scale insect prey, regardless of

the presence of cordgrass pollen, indicating that scale insects are the preferred food resource for these

insects. Adult aggregation to habitat patches containing scale insects may be facilitated by their ability to

perceive olfactory cues, as adult ladybeetles favored air from scale insect-infested leaves over non-

infested leaves in Y-maze assays. Adult ladybeetles fed both scale insects and cordgrass pollen lived

longer than adult ladybeetles fed single -item diets. However, ladybeetles only reproduced when scale

insects were present in their diets, with no added effect of consuming cordgrass pollen. Larval ladybeetle

longevity was greatest on diets containing scale insects, regardless of the presence of cordgrass pollen.

Our findings suggest that adult ladybeetles preferentially aggregate to habitat patches that enhance their

reproductive output, personal longevity, and the longevity of their offspring. In doing so, adult

ladybeetles increase the local population density of all ladybeetle life stages. At high densities, adult and

larval ladybeetles can suppress scale insect populations (even in the presence of cordgrass pollen) and

indirectly benefit salt marsh primary productivity, resulting in enhanced sediment accretion and spring

regrowth.