Speciation in Extreme Cave Ecosystems: Morphometric Analyses Reveal Novel Diversity

In Mexico’s Yucatán peninsula, a variety of endemic invertebrates inhabit an intricate network of submerged anchialine caves, unique ecosystems that contain a layer of marine water overlain by a layer of freshwater. Anchialine habitats have varied in connectivity over time due to fluctuations in sea level, creating periods of isolation for cave-dwelling fauna.  Here, we sought to determine whether such isolation has caused allopatric speciation events in cave shrimp of the genus Typhlatya.  To address this hypothesis, the biodiversity and distribution of Typhlatya spp. in Yucatan caves were investigated.  Geometric morphometric analyses of carapace shape, performed on images of 70 Typhlatya specimens collected from seven different cave sites, revealed distinctive grouping of populations by geographic location, providing supporting evidence for the existence of previously undescribed cryptic species of cave shrimp.  Phylogenetic analyses of nuclear (28s, h3) and mitochondrial (CO1, 16s) genes are currently in progress to complement morphometric analyses in evaluating species differentiation in anchialine cave endemic shrimp.