Tropical ecosystems can show remarkable seasonal variability in temperature and in the quantity and distribution of rainfall. This variability in abiotic factors often explains insects' population fluctuations. Information on the effects of seasonality in insect abundance is critical for understanding insects' community structure and population biology. The present study deals with 3 species of butterflies Hermeuptychia hermes, Paryphthimoides phronius, and Yphitymoides affinis (Nymphalidae: Satyrinae) which experience a noticiable seasonal climate, with a warm-wet season from September to April and a cold-dry season from May to August. A mark release and recapture program was performed to verify how climate seasonality variables affect the population biology of these species. The study was performed in three different areas on the Campinas State University campus in southeastern Brazil as part of a large project that intends to evaluate the natural history of butterflies adapted to live the urban areas. The vegetation of the study site consisted of grass lawns with some scattered trees and bushes. Butterflies were captured with a net and received an exclusive number in the ventral face of the forewings. Sex, age, class, and size of the wing were logged for each individual. Although Lincoln Petersen population size estimations were calculated for all species the low recapture ratios for P. phronius and Y. affinis considerably increased errors, making population size estimates highly variable. Thus, number of individuals presented per day (NIPD) was used as a proxy for abundance. Regression analyses were used to verify the relationship between climate variables and NIPD.
Results/Conclusions
Results show that highest abundance estimates occurred between January and May for H. Hermes and P. phronius, and March to April for Y. affinis. Sex ratio was male biased for H. hermes (X2 = 268.04, p < 0.0001) and P. phronius (X2 = 30.9, p < 0.0001) but not for Y. affinis (X2 = 1.04, p = 0.31). Males of all species had a slightly greater mean resident time and a longer life expectancy than females. A significant relationship between abundance and accumulated precipitation on the previous month for H. hermes and P. phronius but not for Y. affinis. Other studies carried out in tropical areas have shown similar results in which population abundance if affected by a delayed climate variable. Unsuitable abitotic conditions for larval development during the dry season, such as low quality of host plant, could potentially explain the seasonal abundance fluctuations for these species.
