Meeting Abstract

113-4   14:15 - 14:30  The impact of salinity on an estuarian species interaction: How biotic and abiotic factors contribute to the range limit of the Trinidadian guppy Zeller, KR*; Mauro, A; Ghalambor, CK; Colorado State University ; University of California, Berkeley; Colorado State University kyndall_zeller@sbcglobal.net

A classic paradigm in ecology is that large-scale species distributions are primarily dependent on abiotic factors acting via physiological constraints, while biotic interactions refine ranges on a local scale. Yet, interactions between abiotic and biotic factors can be crucial in setting range limits at multiple scales. Here, we explore how a biotic/abiotic interaction contributes to the range limit of the Trinidadian Guppy, Poecilia reticulata, by investigating if a competitive interaction between P. reticulata and Poecilia picta is context dependent. On Trinidad, P. reticulata is restricted to freshwater despite living in brackish water elsewhere, whereas P. picta is found in fresh and brackish water. We previously showed that this pattern is partially due to the presence of P. picta in brackish water, as P. reticulata survival was reduced in brackish water only in the presence of P. picta. We examine why this species interaction appears to contribute to the range limit of P. reticulata by assessing how the interaction is altered by the salinity in which it occurs and by the salinity P. reticulata are raised in. To do this, we recorded aggressive interactions and changes in body condition in experimental tanks in which P. reticulata raised in either fresh or brackish water competed against conspecifics or P. picta in fresh or brackish water. We found that freshwater raised P. reticulata were subordinate to P. picta in brackish water but not freshwater. We also found that brackish water raised P. reticulata performed worse than their freshwater raised counterparts, suggesting that developmental plasticity cannot alter this species interaction in an adaptive manner. Our results indicate that salinity mediates the interaction between P. reticulata and P. picta and plays a role in constraining P. reticulata to freshwater.