We monitored Wisconsin populations of the Karner blue (Lycaeides melissa samuelis Nabokov, Lepidoptera: Lycaenidae) during 1990-2004. We surveyed consecutive spring and summer broods in two contiguous central Wisconsin counties (Jackson, Wood), starting with three sites in summer 1990 and expanding to 14 sites by summer 1996 (“constant-site monitoring”). In northwestern Wisconsin (Burnett County), we started constant-site monitoring of consecutive summer broods with 11 sites in 1991, expanding to 15 sites by 1998. Population indices (Karner blue individuals per km on peak survey per site per brood) from constant sites were positively and significantly correlated with comparable indices for the same broods from “non-constant sites” (all other Karner blue sites we surveyed, which changed in number and location in each brood). The non-constant-site indices for summer 1998-2003 from the statewide Habitat Conservation Plan (HCP) had no significant correlations with our constant-site and non-constant-site indices, or with constant-site indices from Fort McCoy (Monroe County, central Wisconsin). Fort McCoy indices had many significant correlations (all positive) with our constant-site indices, biased toward our indices from nearer sites, but not with our non-constant-site indices. Correlations using both spring and summer indices produced more significant effects than the same tests using only summer or spring broods. Burnett County indices never correlated significantly with indices from central Wisconsin counties ca. 250 km away, while indices from the central Wisconsin counties often covaried significantly. Thus, datasets comprising constant-site indices with >6 years of surveys sampling both spring and summer broods had greater statistical power and showed stronger covariances among nearer sites.
Brood size varied more in consecutive springs than consecutive summers, and the larger the geographic scale of an index, the lower this variability was. The longer the time period sampled, the larger the coefficients of variation (CV) for the mean of the indices per site, so that monitoring for shorter time periods would underestimate Karner blue population variability.
For tests of trend (correlation of indices with year) with P < 0.10, the sign of the coefficient was always the same for a given group of sites, no matter the type of correlation (linear or non-parametric), type of index (three-year running average or individual brood), or set of seasons used (spring and/or summer). Correlations using only summer indices or using both spring and summer indices produced similar levels of significance. Correlations using only spring indices produced fewer significant results. We classified our sites by management class used in the HCP: “shifting mosaic” (SM, in forest succession) and “permanency of habitat” (PH, rights-of-way not in succession). “Reserve” (R) had management activities exceeding the minimum required by the HCP, akin to nature reserve management. R sites had non-significant or positive near-significant trends. SM and PH had many negative significant and near-significant trends, both for fewer sites over more years and more sites for fewer years. SM sites had no tree-cutting during this study, and Karner blue abundance negatively relates to forest canopy. Conversely, routine mowing and brush-cutting in PH sites are favorable for Karner blues. But most PH sites also experienced soil-exposing events in 1996 and/or 2000-2004 that destroyed vegetation. At Crex Meadows, Karner blues appeared to increase more in the permanent non-fire refugium than at other sites there, which continued in fire management with modifications favorable for Karner blues but both the refugium and other sites has similar positive significant trends.
Swengel, Ann B. and Swengel, Scott R.
"Long-Term Population Monitoring of the Karner Blue (Lepidoptera: Lycaenidae) in Wisconsin, 1990-2004,"
The Great Lakes Entomologist: Vol. 38
, Article 11.
Available at: https://scholar.valpo.edu/tgle/vol38/iss2/11