Ecologia populacional de Anaea ryphea(LEPIDOPTERA: NYMPHALIDAE) : fatores a tuando nas fases imaturas

AUTOR(ES)
DATA DE PUBLICAÇÃO

1993

RESUMO

Population studies developed in São Paulo and Panama showed striking differences in the main regulating factors of the continuously breeding tropical butterfly Anaea ryphea. The butterfly occurs from southern Brazil to Mexico, and uses different primary larval food plants in different regions: Croton floribundus at Campinas, São Paulo, Brazil and Croton billbergianus at La Galeta, Colón, Panama. To evaluate larval mortality, I marked individual food plants, censused mapped eggs and larvae at intervals and analyzed mortality data for factors correlated with duration of life cycle, feeding behavior and known sources of mortality. Three years of data from southeastern Brazil showed that: a) The populations of immatures are highly seasonal, with high densities, occurring from approximately November to May (late spring to mid-autumn), with a peak within this period and a reproductive hiatus during winter (dry season). At the Panama site, the species occurred at low densities from approximately August to December, but with no clear peak. b) The time and amplitude of the peak at Campinas vary from year to year. c) Rainfall seems to act as the main factor promoting seasonal differences in mortality of first and second instar larvae, and together with seasonality it influences host plant quality. Life-table k-values suggest that predation (not actually observed) and parasitism (of eggs by trichogrammatid wasps and of fourth instar larvae by braconid wasps) play important roles in the density variation within the seasons. In Panama the k-values are high and similar for all instars, perhaps due to increased predation. Also severe rain storms during the rainy season may help keep densities low (because of mechanical mortality). Diminishing rainfall allows the increase of the population in October. d) A high percentage of eggs disappear at both places, but in Panama it is 50% higher. The percentage of non-fertile and parasitized eggs, on the other hand, is higher in Campinas. The proportion of hatched eggs, as a consequence, is 50% the value of Panama. No parasitism of larvae by Braconidae wasps was observed in Panama, while at Campinas it is the main mortality factor for 4th instar larvae. e) The mortality factors acting on the populations did not show any density-dependence with the present data. The life cycle of the butterfly has the same characteristics in each locality, differing mainly in the duration of the stages, due to low temperatures, and in the wing patterns of the males

ASSUNTO(S)

ecossistema borboleta inseto - população

ACESSO AO ARTIGO

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