Sexual Dimorphism in the Multielemental Stoichiometric Phenotypes and Stoichiometric Niches of Spiders

Abstract

Nutritional limitations may shape populations and communities of organisms. This phenomenon is often studied by treating populations and communities as pools of homogenous individuals with average nutritional optima and experiencing average constraints and trade-offs that influence their fitness in a standardized way. However, populations and communities consist of individuals belonging to different sexes, each with specific nutritional demands and limitations. Taking this into account, we used the ecological stoichiometry framework to study sexual differences in the stoichiometric phenotypes, reflecting stoichiometric niches, of four spider taxa differing in the hunting mode. The species and sexes differed fundamentally in their elemental phenotypes, including elements beyond those most commonly studied (C, N and P). Both species and sexes were distinguished by the C:N ratio and concentrations of Cu, K and Zn. Species additionally differed in concentrations of Na, Mg and Mn. Phosphorous was not involved in this differentiation. Sexual dimorphism in spiders’ elemental phenotypes, related to differences in their stoichiometric niches, suggests different nutritional optima and differences in nutritional limitation experienced by different sexes and species. This may influence the structure and functioning of spider populations and communities.

How to really help bees: nutrient demand and supply in a changing environment

“…It has also been hypothesized that O. bicornis females collect pollen species in proportions that re ect the sex-speci c nutritional needs of their daughters and sons 10,42 . Sex-speci c differences in stoichiometric phenotypes that can be re ected in stoichiometric niches have also been detected in other invertebrates, including amphipods and spiders 31,43 . Our preliminary experiment showed that the scarcity of speci c nutrients in a larval diet indeed impacted bee development in a sex-dependent manner 18 , as predicted by theoretical calculations based on stoichiometric phenotypes and stoichiometric mismatches between consumers and their food 10 .…”

“…The demand for resources for growth and development, as re ected in organismal stoichiometry, is usually studied by comparing different species, but research has also started to focus on individual variations in the chemical compositions of bodies; much of this variation is expected to be attributable to sex differences 19,31,32 . This is expected because processes involved in life history evolution and population dynamics are likely to differentially affect females and males, thus imposing sex-speci c nutritional limitations 27,32 .…”

“…Both concepts share similar ideas and focus on changes in the availability of particular atoms that are needed in speci c proportions to build and maintain organisms as a factor driving the evolution of life and structuring the environment (hereafter, the term "stoichiometric niche" will be used). The stoichiometric niche is de ned as a multivariate niche space occupied by a group of individuals with similar stoichiometries; speci c species occupy speci c niches, and each niche is stoichiometrically explicit [29][30][31] .…”

“…To obtain stoichiometrically balanced food, various organisms with speci c optimal elemental phenotypes (also called ionomes) may prefer various food sources that provide nutrients in proportions that re ect their nutritional demand 31 . Feeding on stoichiometrically unbalanced food, which would result in decreased concentrations of some elements and therefore an unbalanced stoichiometric ratio, may negatively affect bee tness 18 .…”

“…Feeding on stoichiometrically unbalanced food, which would result in decreased concentrations of some elements and therefore an unbalanced stoichiometric ratio, may negatively affect bee tness 18 . Nutritional niches (irrespective of the speci c de nition applied) may differ between sexes, imposing sex-speci c nutritional constraints on organisms 31,32 . It has been suggested that in the case of wild bees, sexual dimorphism in nutritional demand may be an important factor for and should be considered in bee conservation efforts that focus on providing balanced diets to bees [17][18][19] .…”