Sex-specific nutrient use and preferential allocation of resources to a sexually selected trait in Hyalella amphipods

Abstract

Although sexually dimorphic traits are often well studied, we know little about sex-specific resource use strategies that should underlie such dimorphism. We measured sex-specific responses in acquisition and assimilation of two fundamental resources, carbon (C) and phosphorus (P) in juvenile and mature Hyalella amphipods given low and high supplies of inorganic phosphate, analogous to oligotrophic and eutrophic conditions, respectively. Additionally, we quantified allocation of resources to sexual traits in males. Dual radiotracer ( 14 C and 33 P) assays revealed substantial age-and sexspecific differences in acquisition and assimilation. Furthermore, a phenotypic manipulation experiment revealed that amphipods fed low-P food allocated more C to all traits than those fed high-P food. Importantly, we found that amphipods preferentially allocated more C to the development of a sexually selected trait (the posterior gnathopod), compared with a serially homologous trait (the fifth pereopod) not under sexual selection. Substantial differences in how the sexes use fundamental resources, and the impact of altered nutrient supply on such differences, illuminate sexual dimorphism at the lowest level of biological organization. Such information will be important in understanding how sex-and age-specific life history demands influence nutrient processing in a biosphere characterized by rapidly changing alterations to biogeochemical cycles.

Diet composition and social environment determine food consumption, phenotype and fecundity in an omnivorous insect

“…Although density-dependent effects on insect development are wellstudied phenomena [10,12,84,125], the results presented here demonstrate that accounting for the nutritional dimension can yield interesting and divergent results as nutrient quality would modulate the effects of the social environment on insect performance. Additionally, findings in this and previous studies [54][55][56] highlight the relevance of assessing sex-specific responses in studies dealing with the nutritional requirements of organisms.…”

“…The sexual dimorphism in nutrient acquisition and investment evidenced in this study might be a general phenomenon in most insect taxa as sexes may have different nutritional interests derived from disparate life strategies [54,55]. While females would gather resources during their development to afford future investment into reproduction [24], males would invest heavily in secondary sexual traits [56,[105][106][107].…”

“…For instance, males and females would differ in patterns of food selection due to their specific needs (reviewed in [54]). Whereas males may allocate more resources for exaggerated morphological or behavioural traits [54,55], females would invest considerably more resources into reproduction in most invertebrate and vertebrate species [24,54]. By manipulating the social environment, we tangentially address an implicit bias in former nutritional ecology experiments which, in most cases, confined the model species in solitary.…”

In search of an honest butterfly: sexually selected wing coloration and reproductive traits from wild populations of the cabbage white butterfly

“…One example is an increased frequency in the production of interspecific hybrids when individuals are no longer able to distinguish conspecifics as a result of increases in human disturbances (Van der Sluijs et al 2011, Grabenstein and Taylor 2018). Evidence that humans are also affecting such mating signals and systems through nutritional changes to natural and modified landscapes is growing (Snell-Rood et al 2015, Goos et al 2016, Espeset et al 2019). In this study we looked at differences in the relationship between wing coloration and testes size among populations in the cabbage white butterfly, a species with extensive exposure to anthropogenic habitats.…”

“…In disturbed areas, such modification comes about through food waste (Robb et al 2008), road salting (Snell-Rood et al 2014), vehicle-associated aerial chemical deposition, and fertilizer application, among other processes. Fertilizer deposition and pollution are flooding natural and disturbed areas with once-limiting nutrients, such as phosphorous and nitrogen (Vitousek et al 1997, Smil 2000, Galloway et al 2008, Yuan et al 2018), and our understanding of the implications of such nutritional changes on sexually selected characteristics is growing (Snell-Rood et al 2015), especially in terms of honest signaling and sexual selection (Goos et al 2016, Espeset et al 2019).…”