Predicting the distribution of an introduced fish in an endemic hotspot, Cuatro Cienegas, in Coahuila, Mexico

Background/Question/Methods

Invasive species are among the top three greatest threats to global biodiversity, yet our understanding of the characteristics that make a species a good invader or a habitat more susceptible to invasion is limited.  Understanding these mechanisms can aid in predicting areas with a high invasion risk.  Cuatro Cienegas, in Coahuila, Mexico is an oasis in the Chihuahua desert and an endemic hotspot.  A common aquarium trade fish, the West African jewel cichlid (Hemichromis guttatus), was introduced in 1995 and is a potential competitor (based on preliminary isotope data) of two endemic, threatened fishes, the Cuatro Cienegas cichlid (Herichthys minckleyi) and the two-line pupfish (Cyprinodon bifasciatus).  H. guttatus is present in large numbers in parts of the valley and continues to increase its range.    In this study, we investigate the factors associated with H. guttatus presence and attempt to predict areas with a high risk of invasion by H. guttatus and other Hemichromis species.  A survey was performed in the summer of 2010 across the Cuatro Cienegas basin in which H. guttatus presence and environmental parameters (pH, temperature, depth, vegetation cover and salinity) were recorded.  Maxent niche modeling will be performed with several Hemichromis species using environmental and topographic data.

Results/Conclusions

Preliminary analyses suggest that microhabitat temperature and depth are associated with H. guttatus presence, with H. guttatus never being present in any trap set in water less than 26 ºC or at depths greater than 1.8 m.  Percent vegetation cover is hypothesized to be important as well.  Niche modeling will be performed using Maxent for several species of the genus Hemichromis, all of which are commonly sold in the aquarium trade and thus are high risk species for introduction into the environment.  At the local scale, by characterizing the microhabitat characteristics associated with H. guttatus presence and absence, we will be able to suggest more efficient management strategies for preventing its further spread within the Cuatro Cienegas basin.  At a larger scale, we use the niche modeling results to predict areas with a high risk of invasion globally.