Aspects of the life history of the Tamesí molly, Poecilia latipunctata, from two populations in the Río Tamesí drainage in northeastern Mexico

In the face of human-induced environmental change, basic biological data for species threatened by the impacts of human activities are sorely needed to devise and execute proper conservation strategies. Here we provide aspects of basic life-history data for 2 populations of the critically endangered Tamesí molly Poecilia latipunctata (Poeciliidae), which is native to the headwaters of the Río Tamesí in northeastern Mexico. Furthermore, we compare their life historyto that of 2 syntopic species, the Atlantic molly (Poecilia mexicana) and the Amazon molly (Poecilia formosa). Life histories of P. latipunctata are largely similar to that of other mollies: male size was normally distributed in both populations, and females produced 1 clutch at a time, while relying predominantly on yolk for embryo provisioning.However, at our 2 sample sites, P. latipunctata males were smaller than P. mexicana males, and P. latipunctata females produced significantly larger offspring than either P. formosa or P. mexicana. Based on patterns of male and offspring size, we cautiously suggest that, besides anthropogenic disturbance, P. latipunctata might also be suffering from strong interspecific competition, and we call on more research into the basic biology of this species (including its competitive ability).