The evolutionary ecology of poecilia mexicana in the cueva del azufre system effects of abiotic and biotic environmental conditions

Abstract

Caves, with their divergent environmental conditions, provide some of the most unusual habitats on earth and harbor a diversity of highly adapted endemic organisms. Many aspects of the ecology and evolution of cave organisms, however, are poorly understood; probably because the inaccessibility of their habitats, the often small population sizes and their conservation status, as well as the lack of closely related epigean species that would allow for comparative studies. For my thesis, I explore how divergent abiotic conditions and correlated biotic conditions affect the ecology of a small livebearing fish occurring in cave as well as in surface habitats. Furthermore, I identify the evolutionary responses to selective pressures imposed by the environment, ultimately with the goal to contribute to the understanding of the processes that lead to ecological and phenotypic diversity and speciation. My research was conducted in Cueva del Azufre system in southern Mexico where the study species (Poecilia mexicana, Poeciliidae) has occurs in four habitat types: non-sulfidic surface, sulfidic surface, non-sulfidic cave, and sulfidic cave. I documented independent and partially heritable morphological variation as well as genetic differentiation along environmental gradients, providing evidence for parapatric adaptive divergence. I also investigated aspects of the trophic ecology, host-parasite interactions, and predator-prey interactions in the system.