Macronutrient balance mediates the growth of sexually selected weapons but not genitalia in male broad horned beetles
House, Clarissa M; Jensen, K; Rapkin, J; et al.Lane, Sarah; Okada, Kensuke; Hosken, David J; Hunt, J
Date: 5 October 2015
Journal
Functional Ecology
Publisher
Wiley
Publisher DOI
Abstract
Summary
1. Condition is defined as the pool of resources available to an individual that can be allocated
to fitness-enhancing traits. Consequently, condition could influence developmental trade-offs if
any occur. Although many studies have manipulated diet to demonstrate condition-dependent
trait expression, few studies have determined ...
Summary
1. Condition is defined as the pool of resources available to an individual that can be allocated
to fitness-enhancing traits. Consequently, condition could influence developmental trade-offs if
any occur. Although many studies have manipulated diet to demonstrate condition-dependent
trait expression, few studies have determined the contribution of specific nutrients to condition
or trade-offs.
2. We used nutritional geometry to quantify the effects of dietary protein and carbohydrate
content on larval performance and the development of adult morphology including body size
as well as a primary and secondary sexually selected trait in male broad-horned bee tles,
Gnatocerus cornutus.
3. We found that offspring survival, development rate and morphological traits were highly
affected by dietary carbohydrate content and to a lesser extent by protein content and that all
traits were maximized at a protein-to-carbohydrate ratio around 1:2. The absolute size of a
secondary sexual character, the mandibles, had a heightened response to the increased avail-
ability and ratio of both macronutrients. Male genitalia, in contrast, were relatively insensitive
to the increased availability of macronutrients.
4. Overall, while nutrition influenced trait expression, the nutritional requirements of develop-
ment rate and morphological traits were largely the same and resource acquisition seems to
implement only weak trade-offs in this species.
5. This finding contrasts with some resource constraint predictions, as beetles seem able to
simultaneously meet the nutri tional requirements of most traits.
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