Ecological stoichiometry and homeostasis of plants and invertebrates on and nearby heavily fertilized cormorant nesting islands
(English)Manuscript (preprint) (Other academic)
Ecological stoichiometry has generalized the fundamental role of individual nutrient demand in all ecological processes and interactions. It implies that the elemental composition (C:N:P) of a consumer relative to the C:N:P of its resource determines its growth rate and thus secondary productivity. A central, but recently questioned, principle of ecological stoichiometry is the assumption that heterotrophs, in contrast to autotrophs, keep their elemental composition strongly homeostatic. Since neither the relationship between consumer C:N:P and its numeric response to changes in resource C:N:P nor the C:N:P homeostasis of arthropods have been extensively studied for arthropods, we used a natural gradient of N and P loads, in form of seabird and non-seabird islands, to investigate the stoichiometry and homeostasis of primary producers and invertebrates, both on and around islands. We then looked for causal relationships between stoichiometry and the level of homeostasis of a taxonomic group, respectively, and observed numerical responses to seabird fertilization. We found in accordance to principal theories that invertebrates, generally, strongly regulated their stoichiometry while autotrophs were stoichiometrically plastic. Thus, we found no causal relationship between consumer homeostasis and displayed numeric responses. Furthermore, we found only weak support for the hypothesis that the C:N:P of a taxa determines its numeric response to increased resource nutrient content (lepidopteran larvae had high P:C and high abundance on P-rich cormorant islands). We conclude that other species traits than nutrient content mainly determine the success of a taxa in a certain environment. Additionally, due to the strong effects of different level of homeostasis on ecological interactions, food web dynamics and nutrient cycles, we underline the need of further studies on the homeostasis of arthropods.
N:C ratio, P:C ratio, heterotrophs, numeric response, Galerucella
Research subject Plant Ecology
IdentifiersURN: urn:nbn:se:su:diva-43245OAI: oai:DiVA.org:su-43245DiVA: diva2:354913