Spatial and trophic interactions between Gambusia sexradiata and Gambusia puncticulata yucatana (Pisces: Poeciliidae) in Belize, Central America

" The spatial and trophic interactions between two morphologically similar species of mosquitofishes (Gambusia sexradiata and Gambusia puncticulata yucatana) in the savannah ponds of Belize, Central America are examined. G. sexradiata is most commonly found in rivers of northern Belize but moves out over the flooded savannah areas in the rainy season and can be found in ponds, particularly those with a heavy cover of sedges and rushes, for part or all of the year. G. p. yucatana is seldom found in rivers; it is normally associated with savannah ponds in northern Belize and is most abundant where there is little or no vegetation. In savannah ponds with mixed habitats the two species may cooccur, and although G. sexradiata is more abundant in vegetated areas there is considerable spatial overlap as both species are predominantly found within two meters of the shoreline. In these circumstances, subtle microhabitat and feeding-behavior differences may allow coexistence. G. sexradiata feeds closer to shore on benthic, vegetation-associated items and on terrestrial shoreline organisms; G. p. yucatana, although overlapping to some degree in diet, tends to take greater proportions of organisms associated with the water column surface farther from shore. A comparison of this situation with that of two morphologically dissimilar species of Gambusia suggests when conspicuous morphological differences exist, major habitat differences can separate coexisting species, whereas when species are morphologically very similar, separation by habitat is less but is still sufficient to allow behavioral separation along a food axis "