Date of Award


Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)


Ecology and Environmental Sciences


Judith Rhymer

Second Committee Member

Frank Drummond

Third Committee Member

Cynthia Loftin


The Clayton's copper butterfly (Lycaena dorcas claytoni) (Brower 1940) was described as a distinct subspecies in 1940, presumed to be morphologically distinct from the nominate species, Dorcas Copper (Lycaena dorcas dorcas) (Kirby 1837). In 1997, Clayton's copper was listed as endangered in Maine because it is known from few sites statewide, to be abundant at only 1-2 sites, occurs in an uncommon habitat type, and it's global range is nearly confined to Maine (Swartz et al. 2001). This research aimed to address fundamental questions about Clayton's copper, specifically to clarify it's taxonomic status and to estimate density of subpopulations in Maine. These data will aid in determining the global conservation status of Clayton's copper and inform conservation efforts at the state level.

Concern about the subspecific validity of Clayton's copper was the impetus for exploring it's taxonomic status in relation to the Dorcas Copper. This led to a comprehensive study that included other putative L. dorcas subspecies and a closely related congener, the purplish copper, L. helloides. I conducted multivariate statistical analyses of morphological characters using traditional characteristics detailed in the original subspecies description and geometric characters derived from a size-free analysis of wing shape. Additionally, two independent molecular genes were sequenced: one mitochondrial, cytochrome oxidase sub-unit I (COI) and one nuclear, elongation factor lα(EFlα).

Morphometric analysis indicated that traditional morphological characters supplemented with geometric landmarks delimit taxonomic boundaries in most cases, including the subspecific status of Clayton's copper butterfly. There was little or no variation, however, among all L. dorcas subspecies and many purplish copper specimens based on phylogenetic relationships among COI and EFlαDNA sequences. Incongruence between morphological and molecular data suggests that some taxonomic revision may be required, however, delimiting boundaries is not clear-cut. Incongruence might be explained by use of conservative genetic markers, ongoing or recent divergence of taxa, and/or environmental influence on phenotypic variation among groups.

I conducted field studies in 2007 and 2008 to increase understanding of distribution and density of eight Clayton's copper sub-populations in Maine. With the exception of Maine's largest occurrence, censuses to estimate site-specific population density had not previously been done (Webster and Swartz 2006). I quantified the area of shrubby cinquefoil (Dasiphora fruticosa) host plant patches at each site, and estimated site-specific population abundance and dispersion patterns with distance sampling using line transects.

Distance sampling was a useful method for calculating baseline density estimates (with associated error) of Clayton's copper subpopulations at sites with different vegetation structures. Density estimates from distance sampling can also be back-calculated into simpler Pollard indices if required. Analysis of dispersion patterns indicated that butterflies are aggregated both in habitat patches within sites and between sites. Estimates of Clayton's copper population density at eight of the nine known sites (one of which has apparently gone extinct) will aid state personnel in prioritizing sites for management. These results provide baseline information for future study of butterfly and host plant population dynamics at each site.