Macronutrient balance mediates the growth of sexually selected weapons but not genitalia in male broad horned beetles
House, Clarissa M
Hosken, David J
Copyright © 2015 The Authors. Functional Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
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.
Royal Society University
Clarissa M. House Centre for Ecology and Conservation Biosciences Penryn Cornwall TR109EZ UK
First published online: 5 October 2015
Place of publication