Living to the range limit: consumer isotopic variation increases with environmental stress

PeerJ

article

Carl J. Reddin¹  Nessa E. O’Connor²  Chris Harrod³ 

[1] Faculté des Sciences et des Techniques, Université de Nantes;School of Biological Sciences, Queen’s University Belfast;Instituto de Ciencias Naturales Alexander Von Humboldt, Universidad de Antofagasta

关键词: Stress gradient;    Intertidal;    Range limit;    Littorinid;    Stable isotopes;    Trophic niche width;    Physiological condition;    Diet;    Trophic variation;    Isotopic niche;   

DOI  :  10.7717/peerj.2034

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Background: Theoretically, each species’ ecological niche is phylogenetically-determined and expressed spatially as the species’ range. However, environmental stress gradients may directly or indirectly decrease individual performance, such that the precise process delimiting a species range may not be revealed simply by studying abundance patterns. In the intertidal habitat the vertical ranges of marine species may be constrained by their abilities to tolerate thermal and desiccation stress, which may act directly or indirectly, the latter by limiting the availability of preferred trophic resources. Therefore, we expected individuals at greater shore heights to show greater variation in diet alongside lower indices of physiological condition. Methods: We sampled the grazing gastropod Echinolittorina peruviana from the desert coastline of northern Chile at three shore heights, across eighteen regionally-representative shores. Stable isotope values (δ13C and δ15N) were extracted from E. peruviana and its putative food resources to estimate Bayesian ellipse area, carbon and nitrogen ranges and diet. Individual physiological condition was tracked by muscle % C and % N. Results: There was an increase in isotopic variation at high shore levels, where E. peruviana’s preferred resource, tide-deposited particulate organic matter (POM), appeared to decrease in dietary contribution, and was expected to be less abundant. Both muscle % C and % N of individuals decreased with height on the shore. Discussion: Individuals at higher stress levels appear to be less discriminating in diet, likely because of abiotic forcing, which decreases both consumer mobility and the availability of a preferred resource. Abiotic stress might be expected to increase trophic variation in other selective dietary generalist species. Where this coincides with a lower physiological condition may be a direct factor in setting their range limit.

【 授权许可】

CC BY