<scp>Pleistocene–Holocene</scp> vicariance, not Anthropocene landscape change, explains the genetic structure of American black bear (<i>Ursus americanus</i>) populations in the American Southwest and northern Mexico

Gould, Matthew J.; Cain, James W.; Atwood, Todd C.; Harding, Larisa E.; Johnson, Heather E.; Onorato, Dave; Winslow, Frederic; Roemer, Gary W.

doi:10.1002/ece3.9406

Cited by 3 publications

(1 citation statement)

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“…Our results and previous studies that demonstrated declines in genetic diversity in the Great Basin compared to the Sierra Nevada (Malaney et al., 2018 ) indicates that this population of black bears generally conforms to the center–periphery hypothesis with ecologically marginal habitats on the range edge. Although the large geographic range of American black bears means that several different factors limit their distribution among regions, throughout much of western North America, black bears inhabit high elevation mountains surrounded by desert (Gould et al., 2022 ). Piñon‐juniper also occurs in the fringes of these mountains throughout the southwest, suggesting that similar processes, declining reproduction toward the periphery, limit black bear populations elsewhere and not only the availability of habitat.…”

Section: Discussionmentioning

confidence: 99%

Spatial patterns of reproduction suggest marginal habitat limits continued range expansion of black bears at a forest‐desert ecotone

Sultaire,

Montgomery,

Jackson

et al. 2023

Ecology and Evolution

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Investigating spatial patterns of animal occupancy and reproduction in peripheral populations can provide insight into factors that form species range boundaries. Following historical extirpation, American black bears (Ursus americanus) recolonized the western Great Basin in Nevada from the Sierra Nevada during the late 1900s. This range expansion, however, has not continued further into the Great Basin despite the presence of additional habitat. We aimed to quantify whether reduced reproduction toward the range edge contributes to this range boundary. We analyzed black bear detections from 100 camera traps deployed across black bear distribution in western Nevada using a multistate occupancy model that quantified the probability of occupancy and reproduction (i.e., female bears with cubs occupancy) in relation to changes in habitat type and habitat amount toward the range boundary. We detected a strong effect of habitat amount and habitat type on the probability of black bear occupancy and reproduction. At similar levels of landscape‐scale habitat amount (e.g., 50%), estimated probability of occupancy for adult bears in piñon‐juniper woodlands near the range boundary was 0.39, compared to ~1.0 in Sierra Nevada mixed‐conifer forest (i.e., core habitat). Furthermore, estimated probability of cub occupancy, conditional on adult bear occupancy, in landscapes with 50% habitat was 0.32 in Great Basin piñon‐juniper woodlands, compared to 0.92 in Sierra Nevada mixed‐conifer forest. Black bear range in the western Great Basin conforms to the center–periphery hypothesis, with piñon‐juniper woodland at the range edge supporting ecologically marginal habitat for the species compared to habitat in the Sierra Nevada. Further geographic expansion of black bears in the Great Basin may be limited by lower occupancy of reproducing females in piñon‐juniper woodland. Center–periphery range dynamics may be common in large carnivore species, as their dispersal ability allows them to colonize low‐quality habitat near range edges.

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Section: Discussionmentioning

confidence: 99%

Spatial patterns of reproduction suggest marginal habitat limits continued range expansion of black bears at a forest‐desert ecotone

Sultaire,

Montgomery,

Jackson

et al. 2023

Ecology and Evolution

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International border fences and walls negatively affect wildlife: A review

Sennett,

Chambers

2025

Biological Conservation

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USA-Mexico border wall impedes wildlife movement

Harrity,

Traphagen,

Bethel

et al. 2024

Front. Ecol. Evol.

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Geopolitical boundaries can present challenges to wildlife conservation because of varying environmental regulations, and increasingly, the existence of border barriers. As of 2024, approximately 1,023 km of border walls (i.e., steel bollard walls 5.5-9.1 m tall with interstitial spaces ≤10 cm) and 169 km of vehicle barriers (i.e., variable steel structures designed to stop vehicles but not pedestrians) exist along the USA-Mexico border. Some small wildlife passages (21.5 x 27.8 cm) were installed in border walls but few other accommodations for wildlife connectivity exist. As such, ecological consequences of border barriers may be severe and documenting the ability of wildlife to traverse these barriers will be essential to conservation efforts. We placed 36 wildlife cameras across 163.5 km of the USA-Mexico border in Arizona, USA and Sonora, MX to evaluate crossing rates through border barriers for 20 terrestrial species. We observed 9,240 wildlife events, including 1,920 successful crossing events. All focal species crossed through vehicle barriers, whereas white-tailed deer, mule deer, American black bear, American badger, wild turkey, and mountain lion appeared unable to cross through interstitial spaces in border walls. Small wildlife passages improved crossing rates for several species, including American badger, collared peccary, coyote, and mountain lion. Yet, small wildlife passages were scarce with only 13 along >130 km of continuous border wall and failed to allow American black bear, deer, and wild turkey to cross. Additional research on the impacts of border barriers and potential mitigation strategies will be critical for effective transboundary conservation.

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Pleistocene–Holocene vicariance, not Anthropocene landscape change, explains the genetic structure of American black bear (Ursus americanus) populations in the American Southwest and northern Mexico

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 3 publications

References 135 publications

Spatial patterns of reproduction suggest marginal habitat limits continued range expansion of black bears at a forest‐desert ecotone

Spatial patterns of reproduction suggest marginal habitat limits continued range expansion of black bears at a forest‐desert ecotone

International border fences and walls negatively affect wildlife: A review

USA-Mexico border wall impedes wildlife movement

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