Stable isotope evidence for trophic overlap of sympatric Mexican Lake Chapala silversides (Teleostei: Atherinopsidae: Chirostoma spp.)

Abstract

We explore the trophic role that a diverse sympatric group of fishes in the genus Chirostoma play in a large, shallow lake in central Mexico, Lake Chapala. We use δ13C and δ15N stable isotope - based food web analyses to explore how they relate to other components of the Lake Chapala ecosystem. We find five Chirostoma species in top trophic levels of the Chapala food web compared to other fishes, relying on a combination of zooplankton, fish and benthic resources as energy sources. Food web metric analyses showed generally overlapping trophic niches for members of Chirostoma, especially in terms of δ13C. However, C. jordani had lower mean δ15N isotopic values than C. promelas. As a group, "pescados blancos" (C. sphyraena and C. promelas) also had higher δ15N signatures than "charales" (C. consocium, C. jordani and C. labarcae) reflecting greater piscivory, but these differences were not strong for all food web metrics used. Trophic overlap among species of Chirostoma in Lake Chapala raises questions about the forces that might have led to a morphologically diverse but functionally similar and monophyletic group of species.

Nutrients Affecting the Characteristics of Food-Web Structure in Aquatic Ecosystem of Pearl River

“…The δ 13 C values of E. crassipes and S. yagara ranged from −31.6‰ to −23.3‰ and from −19.6‰ to −13.9‰, respectively. The δ 13 C values of E. crassipes were similar to those reported in other studies [37][38][40][41][42]. The δ 13 C values of S. yagara were lower than those reported in previous studies [37][38][40][41][42], similar to those reported for higher aquatic plants [43,49].…”

“…The δ 13 C values of E. crassipes were similar to those reported in other studies [37][38][40][41][42]. The δ 13 C values of S. yagara were lower than those reported in previous studies [37][38][40][41][42], similar to those reported for higher aquatic plants [43,49]. Eutrophication strongly affects the δ 13 C value of higher aquatic plants.…”

“…Phytoplankton is an important primary producer in water ecosystems, and a main food source. In previous studies, the reported range of δ 13 C values of phytoplankton (Chrysophyta and Chlorophyta) was −37.2‰ to −23.6‰ [37][38][39][40][41][42]. These values are slightly different from that of zooplankton (−36.2‰), suggesting that phytoplankton are the main carbon source for zooplankton [29,39,43].…”

Genome-wide species delimitation analyses of a silverside fish species complex in central Mexico indicate taxonomic over-splitting

“…In the case of species of the humboldtianum group occurring within the Lake Chapala ( C. sphyraena , C. promelas , C. consocium , and C. lucius ), several hypotheses of ecological speciation suggest the coexistence of ecotypes in agreement with a differentiation of morphological traits (e.g., jaw shape, head length, oral gape, and gill raker structure) related to feeding habits [ 10 , 50 ], or an ecological partition that correlates with species body sizes (larger ‘peces blancos’ vs . smaller ‘charales’) [ 10 , 16 , 21 ]. However, no strong evidence showing clear patterns of differentiation between morphospecies or ecotypes has been documented to date [ 21 ].…”

“…smaller ‘charales’) [ 10 , 16 , 21 ]. However, no strong evidence showing clear patterns of differentiation between morphospecies or ecotypes has been documented to date [ 21 ].…”