Warming experiments test the sensitivity of an endangered butterfly across life history stages

Introduction: The Karner blue butterfly (Lycaeides melissa samuelis, KBB) is a federally listed endangered species living in disjunct habitats within the Midwest and Eastern United States. As a hostplant specialist and an ectotherm, the KBB is likely to be susceptible to effects of climate change. Aims/Methods: We undertook warming experiments to explore the temperature sensitivity of various KBB life history stages and traits. Over a two-year period, we exposed all KBB life stages to temperature increases of +2, +4, and +6 ⁰C above historic (1952-1999) mean temperatures. We analyzed the effect of these treatments on life history parameters likely related to fitness and population size, including development time, voltinism, degree-day accumulation, body weight, and morphology. Results: Warming treatments resulted in earlier emergence and accelerated development, leading to additional generations. Warming also decreased the number of degree-days required to initiate spring hatch and eclosion. As treatment warmth increased, adult body mass, length, and area decreased and voltinism increased. Females with lower adult mass and smaller body size produced fewer eggs. Discussion: Our data suggest a trade-off between accelerated development and body size. Furthermore, an increase in adult mass and abdominal area was associated with reduced fecundity. Implications for Insect Conservation: Changes in development time and voltinism may affect phenological overlap with the species’ obligate host plant (Lupinus perennis), which could negatively affect completion of the final generation’s lifecycle in a given year, and thus that year’s overwintering population size.