Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ballou, L., Brankovits, D., Chavez-Solis, E. M., Diaz, J. M. C., Gonzalez, B. C., Rohret, S., Salinas, A., Liu, A., Simoes, N., Alvarez, F., Miglietta, M. P., Iliffe, T. M., & Borda, E. An integrative re-evaluation of Typhlatya shrimp within the karst aquifer of the Yucatan Peninsula, Mexico. Scientific Reports, 12(1), (2022): 5302, https://doi.org/10.1038/s41598-022-08779-9.

Description: The Yucatán Peninsula, Mexico is a carbonate platform well-known for extensive karst networks of densely stratified aquifer ecosystems. This aquifer supports diverse anchialine fauna, including species of the globally distributed anchialine shrimp genus Typhlatya (Atyidae). Four species (T. campecheae, T. pearsei, T. dzilamensis and T. mitchelli) are endemic to the Peninsula, of which three are federally listed in Mexico. This first integrative evaluation (i.e., molecular, morphological, broad geographic and type locality sampling, and environmental data) of Yucatán Typhlatya reveals considerable species identity conflict in prior phylogenetic assessments, broad species ranges, syntopy within cave systems and five genetic lineages (of which two are new to science). Despite sampling from the type locality of endangered T. campecheae, specimens (and molecular data) were indistinguishable from vulnerable T. pearsei. Ancestral/divergence reconstructions support convergent evolution of a low-salinity ancestor for a post-Paleogene arc Yucatán + Cuba Typhlatya clade within the anchialine Atyidae clade. A secondary adaptation for the coastal-restricted euryhaline (2–37 psu), Typhlatya dzilamensis (unknown conservation status) was identified, while remaining species lineages were low-salinity (〈 5 psu) adapted and found within the meteoric lens of inland and coastal caves. This study demonstrates the need for integrative/interdisciplinary approaches when conducting biodiversity assessments in complex and poorly studied aquifers.

Description: Financial support for this study was provided by Texas A&M-CONACYT (TI, FA), TI, FA), PAPIIT IN208519 (DGAPA-UNAM) (FA), CONACYT Ciencia Básica A1-S-32846 (FA), Texas A&M University San Antonio (TAMUSA) Start-up Funds (EB), TAMUSA Research Council Grant (EB), TAMUSA Summer Faculty Grant and Fellowship (EB). NSF-REU/OCE: 1560242 supported AL and EB, and TAMU-Louis Stokes Alliance for Minority Participation (HRD: 1612776) supported SR, LS. This work was also supported by the NSF Graduate Research Fellowship Program (M1703014) and the Cave Conservancy Foundation (LB). Typhlatya sampling was sanctioned under collection permits SEMARNAT/SGPA/DGVS 05263/14, 004471/18, 05996/19.

Description: Highlights: • The holopelagic amphipod Paraphronima is shown to contain hidden genetic diversity. • Diversity appears biogeographically restricted to regional scales. • A new species is described using a morpho-molecular approach. • Compound eye characters are shown to be useful in distinguishing species. • The inclusion of compound eyes is recommended in taxonomic studies of Hyperiidea. Holopelagic animals were long assumed to have widespread geographic distributions due to the failure to recognize hydrographic species' barriers in the open ocean. As molecular genetic tools are more commonly used to study the ocean's inhabitants, diversity is found to be substantially higher than when inferred from morphological taxonomies alone. Here, we investigate the morphological and genetic diversity of hyperiid amphipods within the genus Paraphronima, currently comprising two supposedly cosmopolitan species. By combining phylogenetic analyses and four species delimitation methods (GMYC, mPTP, bPTP, ABGD), we reveal substantial species-level genetic variation. Instead of two species inhabiting multiple ocean basins, the biogeography of Paraphronima species appears to be limited to more regional scales. Moreover, there is morphological evidence to corroborate the observed genetic diversity. By using an integrative morpho-molecular approach, a third species from the Gulf of California, Paraphronima robisoni sp. nov., is described. Interestingly, the morphological characters that best distinguish the species within the genus are characters of the compound eyes, which have rarely been used for taxonomy despite being the most obvious and varied features of hyperiids. Our results warrant further investigation of presumably cosmopolitan holopelagic amphipods, while we recommend the inclusion of eye morphology in future taxonomic studies.