Three hundred and fifty generations of extreme food specialisation: testing predictions of nutritional ecology

Abstract

We used a strain of diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), that had been reared for approximately 350 generations in a precisely characterised environment to test hypotheses regarding the influence of nutritional heterogeneity on the evolution of nutrient regulatory responses. Caterpillars were maintained with ad libitum access to a diet that emulated that of an extreme nutritional specialist, comprising a homogeneous food of fixed nutrient composition. We measured performance (survival, development rate, and pupal mass), as well as the protein and carbohydrate intake of individual caterpillars confined to one of a range of single foods differing in their protein, carbohydrate, and water content. In a separate experiment, we measured the amount and balance of protein and carbohydrate self‐selected by caterpillars presented with nutritionally complementary foods. Results showed a close fit with three of four predictions about the nutritional responses of ‘nutrient specialist’ feeders: (1) survival, development rate, and pupal mass were highest for animals given diets with the protein:carbohydrate composition of the ancestral culture diet, and dropped off sharply with higher and lower protein:carbohydrate balance, (2) caterpillars coped poorly with dietary dilution by water, irrespective of the macronutrient balance, and (3) the self‐selected intake point corresponded with the macronutrient balance that gave peak performance (i.e., that of the ancestral culture diet). The fourth prediction, that caterpillars would be disinclined to over‐ingest nutrients on imbalanced diets, was at best weakly met. We hypothesise that the evolution and maintenance of the specialist strategy might, paradoxically, require some degree of environmental heterogeneity.

Geometric analysis of macronutrient selection in breeds of the domestic dog, Canis lupus familiaris

“…Suggestively, the standard diet of the experimental population, which had been in captivity for 75 generations, contained 32% protein, which is very similar to the 35% self-selected by these animals. An equivalent example of tight adaptation in captive-bred animals to the macronutrient composition of the diet has been described by Warbrick-Smith et al (2009).…”

Integrating ancient patterns and current dynamics of insect–plant interactions: Taxonomic and geographic variation in herbivore specialization

“…Indeed, increased plant biodiversity may directly help performance of such grazing‐type generalist herbivores (Specht et al , 2008). However, for herbivores it remains unknown and difficult to determine whether the positive result of mixed diets is due to the maintenance of nutritional balance or the dilution of allelochemical toxins in the plants (Hagele & Rowell‐Rahier, 1999; Moreau et al , 2006; but see Warbrick‐Smith et al , 2009). In contrast to Orthoptera, mixed feeding between different Lepidopteran larval instars (Grabstein & Scriber, 1982; Scriber, 1982), or within instars (Scriber, 1979b, 1981), and under field conditions (Stoyenoff et al , 1994a, 1994b), resulted in poorer or no better performance that single plants.…”

Revisiting macronutrient regulation in the polyphagous herbivore Helicoverpa zea (Lepidoptera: Noctuidae): New insights via nutritional geometry

“…Since Waldbauer et al (1984), protein and carbohydrate regulation has been tested in several lepidopteran species using the GF, including Heliothis virescens (Lee et al, 2006;Telang et al, 2001;Roeder and Behmer, 2014), Heliothis subflexa (Lee et al, 2006), Manduca sexta (Thompson and Redak, 2005), Malacasoma disseria (Despland and Noseworthy, 2006), Plutella xyostella (Warbrick-Smith et al, 2009), Spodoptera exigua (Merkx-Jacques et al, 2008), Spodoptera exempta (Lee et al, 2004b), Spodoptera littoralis (Lee et al, 2004a), and Spodoptera litura (Lee, 2010). Across these species, the ITs range from slightly carbohydrate-biased ratio for S. exempta (0.8:1) to slightly protein-biased ratio for H. virescens (1.5:1) and S. littoralis (1.3:1), with several species selecting for a balanced 1:1 p:c ratio.…”