Extreme habitats are characterized by the presence of extreme physiochemical stressors that require – of any organism tolerating them– costly adaptations that are absent in closely related species. Some organisms are able to cope with extreme environmental conditions and thrive in places that are hostile for most others, giving rise to unique ecological communities and proving life’s capacity to adapt to far from average conditions through natural selection. We use livebearing fishes of the family Poeciliidae, whic have colonized various toxic (hydrogen sulfide-containing) springs, as a model system to study ecological and evolutionary consequences of living in extreme environments.

Our current core research project investigates patterns and mechanisms of local adaptation and ecological speciation in poeciliids inhabiting sulfidic habitats. Using genomic, morphological, and behavioral methods, we are currently investigating (i) how the fish cope with physio-chemical stressors, (ii) whether and how living under extreme conditions leads to adaptive trait divergence and reproductive isolation,(iii) whether similar traits evolved independently in different phylogenetic groups occuring along similar environmental gradients, and (iv) what genomic changes underlie adaptation and speciation in sulfide spring fishes.

Poecilia sulphuraria from the Baños del Azufre.	Poecilia cf. mexicana from a sulfidic spring in the Rio Puyacatengo drainage.
Sulfidic habitats are characterized by extreme hypoxia, dense bacterial growth, and reduced metazoan species diversity.	Adaptations of poeciliids to sulfidic habitats include differences in morphology, physiology, and behavior. Note the lip appendages in this P. sulphuraria.