Similar feeding habits of two morphs of Munida gregaria (Decapoda) evidence the lack of trophic polymorphism

PATRICIA PÉREZ-BARROS; M. CAROLINA ROMERO; JAVIER CALCAGNO; GUSTAVO LOVRICH

REVISTA DE BIOLOGIA MARINA Y OCEANOGRAFIA

INST OCEANOLOGIA

Año: 2010 vol. 45 p. 461 - 470

0717-3326

So far, collected evidences regarding the existing taxonomic conflict between Munida gregaria and M. subrugosa do not support the hypothesis that M. gregaria and M. subrugosa from southern South America are two different biological species. However, the existence of extrinsic (ecologic) postzygotic barriers to gene flow still remains unexplored. We hypothesized that the distinct shapes of the third maxillipeds and of the mandible of both morphospecies may be related to different feeding habits. Adults of M. gregaria and M. subrugosa were captured in the Beagle Channel during November 2004. The dietary overlap between morphospecies was high. Both occupied the same trophic position in the food web of the Beagle Channel, presenting the same feeding habits. As predators they fed mainly on crustaceans and algae, and as deposit feeders they ingested particulate organic matter and organisms associated with the superficial layer of the sediment. However, the relative abundance of crustaceans was higher in stomachs of M. subrugosa than in those of M. gregaria, a higher proportion of stomachs of M. gregaria contained more algae than in M. subrugosa, and a greater frequency of occurrence of unicellular preys was found in the diet of M. gregaria. Notwithstanding these differences, this study provided no evidences to support the existence of extrinsic postzygotic isolation between M. gregaria and M. subrugosa at least based on the feeding habit of adults. Munida gregaria and M. subrugosa do not support the hypothesis that M. gregaria and M. subrugosa from southern South America are two different biological species. However, the existence of extrinsic (ecologic) postzygotic barriers to gene flow still remains unexplored. We hypothesized that the distinct shapes of the third maxillipeds and of the mandible of both morphospecies may be related to different feeding habits. Adults of M. gregaria and M. subrugosa were captured in the Beagle Channel during November 2004. The dietary overlap between morphospecies was high. Both occupied the same trophic position in the food web of the Beagle Channel, presenting the same feeding habits. As predators they fed mainly on crustaceans and algae, and as deposit feeders they ingested particulate organic matter and organisms associated with the superficial layer of the sediment. However, the relative abundance of crustaceans was higher in stomachs of M. subrugosa than in those of M. gregaria, a higher proportion of stomachs of M. gregaria contained more algae than in M. subrugosa, and a greater frequency of occurrence of unicellular preys was found in the diet of M. gregaria. Notwithstanding these differences, this study provided no evidences to support the existence of extrinsic postzygotic isolation between M. gregaria and M. subrugosa at least based on the feeding habit of adults.