Use of Resources by Adult Karner Blue Butterflies (Lycaeides melissa samuelis) in Michigan: Comparisons of Nectar Selections on Native and Non-native Species
Graduate Degree Type
The endangered Karner blue butterfly (Lycaeides melissa samuelis) is at risk due to the decline of oak barrens and dry sand prairies, the butterfly’s sole habitat. Survival depends on effective conservation of remaining habitat and creation of new viable habitats. Successful management must consider resource needs for both larval and adult stages. Information on adult nectar requirements is limited (Grundel et al. 2000, Pickens & Root 2008). Sufficient nectar increases lifespan and fecundity of butterflies (Murphy et al. 1983, Hill & Pierce 1989, Fischer & Fielder 2001), and deters emigration. Encroachment of non-native nectar species into butterfly habitat warrants further investigation into how non-natives are being utilized by Karner blues before they are eradicated. The Huron-Manistee National Forest in Michigan currently hosts some of the largest populations of Karner blue butterflies left in the wild (USFWS 2003). In order to provide optimal resources for adults, we had three main objectives: determine if occupied sites provide sufficient nectar resources for both generations, investigate possible nectar preferences and establish if adults are relying on non-native nectar species. During the summers of 2019 and 2020 we investigated nectar selection preferences of Karner blue butterflies and used logistic regression analyses to compare selected nectar species with other species available within 2 m . Additionally, we examined how non-native species were being used by adult Karner blues. Logistic regression analyses were used to compare selected nectar plants with unselected nectar plants available within a 2 m radius. Results found that during first generation flight periods, nectar sources were limited in abundance and diversity and butterflies had an affinity for Northern dewberry (Rubus flagellaris). Resources available for second generation butterflies were more abundant and diverse. However, population numbers are generally three to four times larger in this brood and additional resources may be needed (Lawrence & Cook 1989, Schweitzer 1989, Bleser 1992, Leach 1993, USFWS 2003, Pickens & Root 2008). Second generation butterflies preferred butterfly weed (Asclepias tuberosa), horsemint (Monarda punctata) and a non-native species, spotted knapweed (Centaurea stoebe). Recommendations include: bolster nectar plant abundance and diversity available during the first generation, increase abundance of butterfly weed and horsemint for second generation butterflies and restore the pollinator community with sufficient native nectar resources before eradicating spotted knapweed.
Herweyer, Afafia, "Use of Resources by Adult Karner Blue Butterflies (Lycaeides melissa samuelis) in Michigan: Comparisons of Nectar Selections on Native and Non-native Species" (2023). Culminating Experience Projects. 297.