A complete record from colonization to extinction reveals density dependence and the importance of winter conditions for a population of the silvery blue, Glaucopsyche lygdamus

Matthew L. Forister1a*, James A. Fordyce2b, Andrew C. McCall3c, and Arthur M. Shapiro4d

1Program in Ecology, Evolution and Conservation Biology, Department of Biology, University of Nevada, Reno
2Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville
3Department of Biology, Denison University, Granville, Ohio
4Center for Population Biology, University of California, Davis

Abstract

Butterflies in the family Lycaenidae are often the focus of conservation efforts. However, our understanding of lycaenid population dynamics has been limited to relatively few examples of long-term monitoring data that have been reported. Here, factors associated with population regulation are investigated using a complete record of a single population of the silvery blue, Glaucopsyche lygdamus Doubleday (Lepidoptera: Lycaenidae). Adults of G. lygdamus were first observed in an annual grassland near Davis, California, in 1982 and were last seen in 2003. Relationships between inter-annual variation in abundance and climatic variables were examined, accounting for density dependent effects. Significant effects of both negative density dependence and climatic variation were detected, particularly precipitation and temperature during winter months. Variation in precipitation, the strongest predictor of abundance, was associated directly and positively with butterfly abundance in the same year. Winter temperatures had a negative effect in the same year, but had a lagged, positive effect on abundance in the subsequent year. Mechanistic hypotheses are posed that include climatic effects mediated through both larval and adult plant resources.

Keywords: exotic host, Lycaenidae, population dynamics

Correspondence: a mforister@unr.edu, b jfordyce@utk.edu, c mccalla@denison.edu, d amshapiro@ucdavis.edu, *Corresponding author

Editor: David Heckel was Editor of this paper

Received: 6 November 2010 | Accepted: 5 May 2011 | Published: 3 October 2011

ISSN: 1536-2442 | Volume 11, Number 130

Forister ML, Fordyce JA, McCall AC, Shapiro AM. 2011. A complete record from colonization to extinction reveals density dependence and the importance of winter conditions for a population of the silvery blue, Glaucopsyche lygdamus. Journal of Insect Science 11:130 available online: insectscience.org/11.130


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