Shrub encroachment is altering the structure and species composition of natural communities across the globe. However, little research has focused on how shrub encroachment influences wetland vertebrates, including small mammals. We sought to determine how vegetative structure and shrub cover influenced the occurrence of a threatened semiaquatic mammalian subspecies, the Sanibel Island rice rat (Oryzomys palustris sanibeli). We evaluated the influence of vegetation and metrics of inundation on probability of occurrence and localized seasonal colonization and extinction rates of the Sanibel Island rice rat over a 3-year period. We found Sanibel Island rice rats on 18 (33.3%) of our 54 sites. Their occurrence was positively associated with greater sand cordgrass (Spartina bakeri) cover and increased elevation, but negatively associated with greater shrub cover. Their probability of localized colonization was negatively associated with greater shrub cover. Localized extinction probabilities for Sanibel Island rice rats were positively associated with increased rainfall totals in the preceding 3 months and greater shrub cover. Using aerial photography from across the Sanibel Island rice rat’s range, we found 5.5-fold greater shrub cover in 2015 than in 1944. We suggest that increases in shrub cover and reduced cordgrass cover may be driving the decline of this once ubiquitous endemic species and that the encroachment of freshwater wetlands requires greater attention due to its potential to imperil wetland-dependent wildlife.

中文翻译：

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灌木侵占威胁着地方性岛屿湿地啮齿动物的持续存在

灌木侵占正在改变全球自然群落的结构和物种组成。然而，很少有研究关注灌木侵占如何影响湿地脊椎动物，包括小型哺乳动物。我们试图确定植物结构和灌木覆盖如何影响受威胁的半水生哺乳动物亚种 Sanibel 岛稻鼠 (Oryzomys palustris sanibeli) 的发生。我们评估了植被和淹没指标对萨尼贝尔岛稻鼠在 3 年内发生概率和局部季节性定殖和灭绝率的影响。我们在 54 个站点中的 18 个（33.3%）处发现了萨尼贝尔岛稻鼠。它们的出现与更大的沙线草（Spartina bakeri）覆盖率和海拔升高呈正相关，但与更大的灌木覆盖呈负相关。它们的局部定植概率与更大的灌木覆盖率呈负相关。萨尼贝尔岛稻鼠的局部灭绝概率与前 3 个月的总降雨量增加和灌木覆盖面积增加呈正相关。使用整个萨尼贝尔岛稻鼠分布范围的航空摄影，我们发现 2015 年的灌木覆盖率是 1944 年的 5.5 倍。我们认为，灌木覆盖率的增加和软草覆盖率的减少可能会导致这种曾经无处不在的特有物种的减少，并且淡水湿地的侵占需要更多的关注，因为它有可能危及依赖湿地的野生动物。萨尼贝尔岛稻鼠的局部灭绝概率与前 3 个月的总降雨量增加和灌木覆盖面积增加呈正相关。使用整个萨尼贝尔岛稻鼠分布范围的航空摄影，我们发现 2015 年的灌木覆盖率是 1944 年的 5.5 倍。我们认为，灌木覆盖率的增加和软草覆盖率的减少可能会导致这种曾经无处不在的特有物种的减少，并且淡水湿地的侵占需要更多的关注，因为它有可能危及依赖湿地的野生动物。萨尼贝尔岛稻鼠的局部灭绝概率与前 3 个月的总降雨量增加和灌木覆盖面积增加呈正相关。使用整个萨尼贝尔岛稻鼠分布范围的航空摄影，我们发现 2015 年的灌木覆盖率是 1944 年的 5.5 倍。我们认为，灌木覆盖率的增加和软草覆盖率的减少可能会导致这种曾经无处不在的特有物种的减少，并且淡水湿地的侵占需要更多的关注，因为它有可能危及依赖湿地的野生动物。