The morphology–diet relationship and its role in the coexistence of two species of annual fishes |
| |
Authors: | Friedrich W. Keppeler Luis Esteban K. Lanés Ana S. Rolon Cristina Stenert Pablo Lehmann Martin Reichard Leonardo Maltchik |
| |
Affiliation: | 1. Department of Ecology, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Rio Grande do Sul (RS), Brazil;2. Laboratory of Ecology and Conservation of Aquatic Ecosystems, University of Vale do Rio dos Sinos (UNISINOS), S?o Leopoldo, RS, Brazil;3. Laboratory of Ichthyology, Instituto Pró‐Pampa (IPPampa), Pelotas, RS, Brazil;4. Laboratory of Ichthyology, University of Vale do Rio dos Sinos (UNISINOS), S?o Leopoldo, RS, Brazil;5. Academy of Sciences of the Czech Republic, Institute of Vertebrate Biology, Brno, Czech Republic |
| |
Abstract: | Annual fishes, which inhabit temporary pools with extremely limited habitat complexity and niche availability, display remarkable sexual dimorphism, rapid growth, and enormous investment into reproduction, all traits associated with high energy requirement. This study tests three hypotheses for two syntopic annual fishes (Austrolebias minuano and Cynopoecilus fulgens) found in six wetlands of southern Brazil: (i) considerable morphological differences result in low dietary overlap, (ii) sexual dimorphism in both species leads to intraspecific diet segregation, and (iii) dietary richness increases during ontogenetic development, and is narrower in C. fulgens than A. minuano due to morphological limitations imposed by reduced size. The diet of 82 A. minuano and 211 C. fulgens individuals was analyzed over two annual cycles. The morphology was characterized by 26 measurements covering the entire body of both species. There was no evidence of morphological specialization related to food competition and the diet of A. minuano and C. fulgens showed high overlap. High food availability, high predator abundance, and high connectivity of adjacent wetlands are likely the main mechanisms allowing coexistence of both species. Within species, sexual dimorphism did not result in a decrease in dietary overlap, which reinforces the idea that morphological differences between the sexes did not evolve as a mechanism to decrease food competition. Large A. minuano did not have a more diverse diet than the smaller C. fulgens; however, increase in body size allowed both species to ingest larger prey. Morphological variability in both species was mainly related to ontogenetic development and reproduction. |
| |
Keywords: |
Austrolebias minuano
Cynopoecilus fulgens
niche overlap sexual dimorphism ontogeny |
|
|