Search

The phylogeography of the American black bear (Ursus americanus) is characterized by isolation into glacial refugia, followed by population expansion and genetic admixture. Anthropogenic activities, including overharvest, habitat loss, and transportation infrastructure, have also influenced their landscape genetic structure. We describe the genetic structure of the American black bear in the American Southwest and northern Mexico and investigate how prehistoric and contemporary forces shaped genetic structure and influenced gene flow. Using a suite of microsatellites and a sample of 550 bears, we identified 14 subpopulations organized hierarchically following the distribution of ecoregions and mountain ranges containing black bear habitat. The pattern of subdivision we observed is more likely a product of postglacial habitat fragmentation during the Pleistocene and Holocene, rather than a consequence of contemporary anthropogenic barriers to movement during the Anthropocene. We used linear mixed‐effects models to quantify the relationship between landscape resistance and genetic distance among individuals, which indicated that both isolation by resistance and geographic distance govern gene flow. Gene flow was highest among subpopulations occupying large tracts of contiguous habitat, was reduced among subpopulations in the Madrean Sky Island Archipelago, where montane habitat exists within a lowland matrix of arid lands, and was essentially nonexistent between two isolated subpopulations. We found significant asymmetric gene flow supporting the hypothesis that bears expanded northward from a Pleistocene refugium located in the American Southwest and northern Mexico and that major highways were not yet affecting gene flow. The potential vulnerability of the species to climate change, transportation infrastructure, and the US–Mexico border wall highlights conservation challenges and opportunities for binational collaboration. [ABSTRACT FROM AUTHOR]

There are 11 species of triatomines in the USA, with seven reported in the American Southwest. These species are capable of transmitting Trypanosoma cruzi, the etiological agent of Chagas disease, but are generally sylvatic and rarely infect humans in the USA. iNaturalist is one of the most popular citizen science data portals, where users record encounters with any individual organism. As of November 2023, iNaturalist reported 722 confirmed triatomine observations in the American Southwest. Maximum entropy ecological niche modelling and bioclimatic environmental variables were used to predict zones of highest human-triatomine interaction. Models fit well for Triatoma protracta (0.85), T. rubida (0.94), and T. recurva (0.96). Precipitation in the warmest quarter was most predictive of T. protracta presence, while precipitation in the driest quarter was most predictive of T. rubida and T. recurva. Locations identified in the American Southwest with highest potential for human-triatomine interaction, and potential T. cruzi transmission, were coastal California, the Sierra Nevada foothills, southern Arizona and border areas of northern Mexico. Study findings can be used for targeted surveillance efforts to address the paucity of contemporary information regarding triatomine species diversity and geographical and ecological associations in the American Southwest., (© 2024. The Author(s).)

The transition from foraging to farming is certainly one of the most dramatic processes in human history. The use of domesticated plants and animals spread widely across Southwest Europe from the Near East. By contrast, domesticated plants solely moved across the American Southwest from Mexico. Research in Western Europe has traditionally focused on the movement of farming communities across the region which displaced or subsumed local foragers. Recently various aspects of this process have been debated including Mesolithic and Neolithic subsistence packages, continuity versus replacement, regional mobility and sedentism, the nature of early Neolithic villages, and the forager to farmer transition. We will explore this dynamic and varied process through studies conducted in Southwest Europe and the American Southwest. Although these two regions seem quite different, researchers in both areas are grappling with similar research issues. [ABSTRACT FROM AUTHOR]

The article examines the Colorado River's natural and cultural systems and the outlook for the river's viability as a renewable water source that will support human habitation in the region of the Colorado River Basin. The discussion focuses on the influence of humans on the natural world in the American Southwest, water use, sustainability, and environmental values. The disappearance of the Santa Cruz River, water consumption in cities such as Tucson in Arizona, water extraction from aquifers under the Sonoran Desert, and the occurrence of subsidence after the removal of groundwater are mentioned.