Evol Ecol Res 15: 79-91 (2013)     Full PDF if your library subscribes.

Evidence for adaptive sex allocation in Tamalia coweni (Hemiptera: Aphididae) in response to nutrient variability in Arctostaphylos patula

George Colin Purdy and Donald G. Miller

Department of Biological Sciences, California State University, Chico, California, USA

Correspondence: D.G. Miller, Department of Biological Sciences, California State University, Chico, CA 95929–0515, USA. E-mail: dgmiller@csuchico.edu

ABSTRACT

Question: Do animal species with facultative sex allocation invest adaptively according to local environmental conditions?

Hypothesis: The Trivers-Willard hypothesis can explain maternal sex allocation patterns in response to experimental manipulations in the field.

Organisms: A galling aphid, Tamalia coweni, and its host plant, Arctostaphylos patula.

Field site: Lassen National Forest, Butte County, California, USA, 1700 m above sea level.

Methods: Using a randomized block design we enriched host plants with various concentrations of nitrogen (urea), then recorded sex ratios and mass of developing male and female offspring, as well as female fecundity.

Conclusions: Aphid foundresses respond to nitrogen enrichment by skewing brood sex ratios towards daughters. We observed no changes in T. coweni body mass or its number of presumptive ova.

Keywords: aphid, gall, nitrogen, parental investment, sex ratio, Trivers-Willard hypothesis.

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