Meeting Abstract
26.1 Friday, Jan. 4 Food limited butterflies �” Resting and flight metabolic rate, fecundity and longevity NIITEPOLD, K*; PEREZ, A; BOGGS, CL; Stanford University niitepold@stanford.edu
Deciding how much to invest in survival and reproduction is fundamental for all organisms, especially when the available resource pool is limited. Resource availability can be affected by small-scale disturbances such as weather conditions or herbivory, or large-scale environmental changes such as habitat loss and fragmentation, and climate change. To understand the mechanistic basis of population dynamics in a changing world we need experimental work on resource allocation under stressful conditions. We limited adult food intake in two butterfly species with different ecologies and life-history strategies: Colias eurytheme and Speyeria mormonia. Colias is multivoltine and has no larval diapause; Speyeria is univoltine and spends the winter as unfed 1st instar larvae. Females were hand-fed twice a day. We measured the unlimited sugar-water intake of control females and gave treatment females half of that. We found that body mass decreased with age in both treatments, but females fed ad lib were clearly heavier than food limited females. Mass-corrected peak flight metabolic rate was not affected by food limitation. This indicates that flight capacity is conserved, which may allow dispersal to more favorable areas. Flight is also critical for most other life-history traits. Lifespan was not affected by food reduction. Fecundity was sacrificed in both species. The decrease in fecundity was stronger in Speyeria. This may be due to a high ratio of adult-derived carbon in Speyeria eggs, a likely consequence of larvae relying on solely maternal resources during the winter. Control females had higher resting metabolic rate in early life. This may reflect the energetic cost of egg production which food limited females could not bear. Food limitation results in lower fecundity and may reduce population growth rate, but the sensitivity of each species is related to its life-history strategy.
