Nutrient acquisition across a dietary shift: fruit feeding butterflies crave amino acids, nectivores seek salt

Abstract

Evolutionary dietary shifts have major ecological consequences. One likely consequence is a change in nutrient limitation-some nutrients become more abundant in the diet, others become more scarce. Individuals' behavior should change accordingly to match this new limitation regime: they should seek out nutrients that are deficient in the new diet. We investigated the relationship between diet and responses to nutrients using adult Costa Rican butterflies with contrasting feeding habits, testing the hypothesis that animals will respond more positively to nutrients that are scarcer in their diets. Via literature searches and our own data, we showed that nitrogen and sodium are both at lower concentration in nectar than in fruit. We therefore assessed butterflies' acceptance of sodium and four nitrogenous compounds that ranged in complexity from inorganic nitrogen (ammonium chloride) to protein (albumin). We captured wild butterflies, offered them aqueous solutions of each substance, and recorded whether they accepted (drank) or rejected each substance. Support for our hypothesis was mixed. Across the sexes, frugivores were four times more likely to accept amino acids (hydrolyzed casein) than nectivores, in opposition to expectation. In males, nectivores accepted sodium almost three times more frequently than frugivores, supporting expectations. Together, these results suggest that in butterflies, becoming frugivorous is associated with an increased receptivity to amino acids and decreased receptivity to sodium. Nectivory and frugivory are widespread feeding strategies in organisms as diverse as insects, birds, and bats; our results suggest that these feeding strategies may put different pressures on how animals fulfill their nutritional requirements.

Structure and function of the bacterial and fungal gut microbiota of Neotropical butterflies

“…Frugivorous gut communities were better at digesting amino acids and carboxylic acids, while nectivorous gut flora outperformed frugivorous communities in catabolism of sugars and sugar alcohols. These catabolic patterns are congruent with the relative nutritional makeup of butterfly foods (Ravenscraft and Boggs ), which suggests that gut microbiota specialize in digestion of compounds abundant in the host's diet.…”

“…Nectars are 90% sugar by dry mass (Luttge ). Fruit generally contains more nitrogen than nectar: at our field site, the juice of rotting Dipteryx oleifera , the dominant food available to frugivorous butterflies during portions of the year, contains 33 times more essential amino acids and 19 times more non‐essential amino acids per unit sugar than the flower nectars fed upon by butterflies (Ravenscraft and Boggs ). Frugivorous butterflies may therefore provide a comparatively nitrogen‐rich gut environment that supports microbes capable of catabolizing amino acids, while nectivores provide a more sugar‐rich environment that favors microbes specialized on sugar catabolism.…”

“…In a broad survey of the insect gut flora, feeding guild (e.g., herbivore, omnivore, detritivore, pollenivore) explained 23% of variation in the gut flora. The comparatively small amount of variation in the butterfly gut flora explained by diet could be due in part to the broadly similar nature of butterfly foods: although they differ in content of both amino acids and secondary metabolites (Adler , Ravenscraft and Boggs ), both are fundamentally sugary liquids.…”

Mitogenome evolution in ladybirds: Potential association with dietary adaptation

“…Dietary shifts can alter the relative availability of different nutrients and are therefore associated with metabolic adaptation in animals (Babbitt, Warner, Fedrigo, Wall, & Wray, 2010;Ballard & Youngson, 2015;Li et al, 2016;Pontremolil et al, 2015;Ravenscraft & Boggs, 2016). Here, we propose that differences in diets among ladybirds should cause adaptive evolution of their mitogenomes.…”

Diet-mediated modulation on the development and phenoloxidase activity in the Alder leaf beetle larvae, Agelastica alni (L., 1758) (Coleoptera: Chrysomelidae)

“…According to nutritional ecology, animals develop mechanisms to regulate nutritional imbalances in their diet (Cotter et al, 2011;Prasad & Mukhopadhyay, 2015;Rho & Lee, 2015). Even herbivores can change the amount of consumption to compensate for nutritional imbalance (Waldbauer & Friedman, 1991;Bernays, 1998;Cotter et al, 2011;Ravenscraft & Boggs, 2016). Also, for A. alni larvae, food intake varies between artificial diets.…”