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Life history characteristics track butterfly fauna population dynamics.

Runquist, Erik *,1, Forister, Matt2, O'Brien, Joshua1, Thorne, James1, Shapiro, Arthur1, 1 University of California, Davis, Davis, CA, USA2 The State University of New York, Stony Brook, Stony Brook, NY, USA

ABSTRACT- Long-term intensive biological surveys are rare, especially when they are conducted under a consistent protocol. For more than 30 consecutive years, one of us (A.M.S.) has repeatedly recorded presence-absence data (approximately biweekly) for butterfly populations at 10 permanent sites across a southwest-northeast transect through north-central California, and more than 5050 site-surveys have been completed to date. In response to an observed crash in overall abundance, species-level abundance data has been collected for each site-visit since 1999 at five sites across the Central Valley and Inner Coast Range. Measures of rank abundance are highly correlated with rank day-positives (surveys during which a species was verified as being present at a site) and linear regressions demonstrate that 1999 was indeed a down year when compared to the entire 32-year dataset. The analyses we describe here focus on the relationship between life history characteristics and population trends from the 1999 crash through 2004 using nested ANOVAs on log-transformed total year abundances. Multivoltine, weedy, and host generalist species have increased since 1999, while bi- and univoltine, non-weedy, and host specialist species have remained at about their 1999 level or even declined. Populations of species that overwinter as pupae or larvae have remained more stable than populations of migrant and egg and adult hibernating species. These results are largely constant across sites and demonstrate that life history characteristics are strongly correlated with population dynamics at the faunal level and support concurrent research on long-term changes in central California butterfly species composition. The consistency of these trends across heterogeneous groups of species is noteworthy.

Key words: autecology, butterfly, California, phenology

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