Body size is negatively correlated with trophic position among cyprinids.
Body size has many ecological and evolutionary implications that extend across multiple levels of organization. Body size is often positively correlated with species traits such as metabolism, prey size and trophic position (TP) due to physiological and mechanical constraints. We used stable isotope analysis to quantify TP among minnows across multiple assemblages that differed in their species composition, diversity and food web structure. Body size significantly predicted TP across different lineages and assemblages, and indicated a significant negative relationship. The observed negative relationship between body size and TP is contrary to conventional knowledge, and is likely to have arisen owing to highly clade-specific patterns, such that clades consist of either large benthic species or small pelagic species. Cyprinids probably subvert the physiological and mechanical constraints that generally produce a positive relationship between body size and TP using anatomical modifications and by consuming small-bodied prey, respectively. The need for herbivorous cyprinids to digest cellulose-rich foods probably selected for larger bodies to accommodate longer intestinal tracts and thereby to facilitate digestion of nutrient-poor resources, such as algae. Therefore, body size and TP are likely to have coevolved in cyprinids in association with specialization along the benthic to pelagic resource axis.
Department of Biological Sciences and Museum of Natural History , Auburn University , 101 Life Sciences Building, Auburn, AL 36849 , USA.
Edward D
ED
Burress
Florida Fish and Wildlife Conservation Commission , Fish and Wildlife Research Institute , 7386 Northwest 71st Street, Gainesville, FL 32653 , USA.
Jordan M
JM
Holcomb
Departamento de Zoologia , Universidade Federal do Rio Grande do Sul , Instituto de Biociências, CEP 91501-970, Porto Alegre, Rio Grande do Sul , Brazil.
Karine Orlandi
KO
Bonato
Department of Biological Sciences and Museum of Natural History , Auburn University , 101 Life Sciences Building, Auburn, AL 36849 , USA.
Jonathan W
JW
Armbruster
Cyprinidae; benthic–pelagic axis; coevolution; community structure; diet