The rivers found in the eight countries in southern North America are exceptionally ecologically and culturally diverse. In this chapter, we focus on a small number of the rivers found in the largest of these countries, Mexico. Remarkable variation in climate and topography generates differences in orographic factors that produce diverse precipitation regimes throughout the country, subsequently influencing patterns in runoff and temporal and spatial variation in Mexican rivers (Hudson et al., 2005; INEGI, 2020a). Mexico is 1.96 million km2, or approximately only20% the size of the United States, yet it is home to 84% of the total number of Level II ecoregions found in the United States and is characterized by exceptional heterogeneity in surface water resources. Some of the wettest (e.g., the Lacand´on Forest in Chiapas) and driest (e.g., the deserts of Sonora) places on the continent are found in Mexico. The Mexican population is growing and so is the Mexican economy (World Bank, 2020). As seen in many regions of the world, the population is urbanizing with growth concentrated in larger cities; approximately 80% of the Mexican population is urban. Population density is approximately 65 people/km2, and annual population growth is currently estimated to be 1.1%. Like many other North American basins, agricultural development, industri-alization, and hydroelectric development threaten the quality and quantity of water flowing through Mexican rivers. Mexico is currently home to at least 25 major Indigenous groups (INEGI, 2020a), many of whom also have long and complex relationships with rivers and streams. It is widely accepted that land-use change and infrastructure development by early civilizations had large impacts on basin-level processes. The Olmec, the earliest known major civilization in Mesoamerica, constructed the first conduit drainage system in the Americas (Doolittle, 2011). As it still does today, forest conversion to slash and burn agriculture by early Mexican civilizations accel-erated soil erosion, potentially compromising freshwater quality. The Mayans reached a population of approxi-mately five million people, peaking around 700 CE They depended on travel and trade conducted along the Grijalva-Usumacinta River, one of the largest drainages in Mesoamerica (Beach et al., 2015).

Insular habitats have played an important role in developing evolutionary theory, including natural selection and island biogeography. Caves are insular habitats that place extreme selective pressures on organisms due to the absence of light and food scarcity. Therefore, cave organisms present an excellent opportunity for studying colonization and speciation in response to the unique abiotic conditions that require extreme adaptations. One vertebrate family, the North American catfishes (Ictaluridae), includes four troglodytic species that inhabit the karst region bordering the western Gulf of Mexico. The phylogenetic relationships of these species have been contentious, and conflicting hypotheses have been proposed to explain their origins. The purpose of our study was to construct a time-calibrated phylogeny of Ictaluridae using first-occurrence fossil data and the largest molecular dataset on the group to date. We test the hypothesis that troglodytic ictalurids have evolved in parallel, thus resulting from repeated cave colonization events. We found that Prietella lundbergi is sister to surface-dwelling Ictalurus and that Prietella phreatophila + Trogloglanis pattersoni are sister to surface-dwelling Ameiurus, suggesting that ictalurids colonized subterranean habitats at least twice in evolutionary history. The sister relationship between Prietella phreatophila and Trogloglanis pattersoni may indicate that these two species diverged from a common ancestor following a subterranean dispersal event between Texas and Coahuila aquifers. We recovered Prietella as a polyphyletic genus and recommend P. lundbergi be removed from this genus. With respect to Ameiurus, we found evidence for a potentially undescribed species sister to A. platycephalus, which warrants further investigation of Atlantic and Gulf slope Ameiurus species. In Ictalurus, we identified shallow divergence between I. dugesii and I. ochoterenai, I. australis and I. mexicanus, and I. furcatus and I. meridionalis, indicating a need to reexamine the validity of each species. Lastly, we propose minor revisions to the intrageneric classification of Noturus including the restriction of subgenus Schilbeodes to N. gyrinus (type species), N. lachneri, N. leptacanthus, and N. nocturnus.

Fish occurrence data are widely scattered and mostly not published as data readily utilizable by computers. Global biodiversity aggregating services (e.g. GBIF, iDigBio, Fishnet) now aggregate and serve whatever data are submitted to them in the standard Darwin Core format, but their data are often replete with errors, minimally normalized, lacking content across standard fields, and served via generic mapping services lacking linkages to local and aquatic ecology-relevant resources (i.e., for fishes, they are ignorant of hydrography). In contrast, Fishes of Texas (FoTX) includes the same data and much more, including unpublished data from more diverse sources. FoTX’s rigorous quality-control measures, including specimen-based ID verifications, checking of legacy georeferencing, and flagging suspicious records has combined to greatly reduce errors. The custom FoTX website provides interactive exploration and data summarization, within the context of geopolitical and, now geographically-expanded hydrographic coverages, thus facilitating visualization and discovery of conservation-relevant histories and trends over time. The site allows viewing of derivative products, such as niche models, estimates of native ranges, checklists, data dashboards, and Native Fish Conservation Areas. The site also serves extensive image collections, collectors’ field notes, and links to digitized, formerly inaccessible unpublished agency reports. Finally, core FoTX data fields are also published to GBIF as Darwin Core to make it available to the world.