Nutrients in fruit increase fertility in wild-caught females of large and long-lived Euphaedra species (Lepidoptera, Nymphalidae)

Abstract

Fruit-feeding butterflies can experience a more nutrient rich adult diet than nectar-feeding species, and can be expected to use these nutrients for egg production. Here we compare life span, and reproduction parameters of wild-caught females of large and long-lived species on either a sucrose or a mashed banana diet. With small sample sizes per species, but rich longitudinal data for each individual, we examined the longitudinal reproduction pattern, egg size and hatchability of these butterflies in captivity. Diet significantly affected mortality in captivity in a time-dependent manner. On average, we found that butterflies fed mashed banana laid 1.855 times more eggs than those fed sugar. They laid significantly more eggs when they laid and conserved egg size with age while butterflies fed sucrose showed significantly declining egg sizes. Egg hatchability was not significantly affected by diet. Long pre-oviposition periods, significantly smaller first eggs, and absence of age at capture effects on intensity of reproduction indicate low reproduction rates in the field that are due to low food availability. With our small sample sizes, we did not detect significant differences between the species in their response to the diet treatments.

Fig. 1

Kaplan–Meier plots for wild-caught female E. alacris, E. harpalyce and E. medon with butterflies fed sugar (grey) and mashed banana (black).

Fig. 2

Reproduction of wild-caught female butterflies in captivity. The median is indicated by the solid line in each box, whose lower and upper bounds are the first and third quartiles. The difference between the first and third quartiles is referred as inter quartile range (IQR). Data points which are 1.5 IQR smaller than the first quartile or 1.5 IQR bigger than the third quartile are indicated by circles and referred to as outliers. A whisker connects the boundary of the box with the largest value which is not an outlier. Censored observations are indicated with plus signs.

Fig. 3

Longitudinal egg reproduction of butterflies in sugar and banana cohorts. The smoothed mean curves were created from the raw data of all species combined using the “loess” function in R, which is a local polynomial smoothing technique, and the 95% point-wise bootstrap confidence intervals for combined species were derived from the 1000 bootstrap samples.

Fig. 4

Daily parity plots for wild-caught E. medon fed sugar (left) and mashed banana (right), where black regions represent the proportion of butterflies laying more than 10 eggs on a day, grey 1–10 eggs, and white region 0 eggs.