Data from: Conservation genetics of extremely isolated urban populations of the Northern Dusky Salamander (Desmognathus fuscus) in New York City

Urbanization is a major cause of amphibian decline. Stream-dwelling plethodontid salamanders are particularly susceptible to urbanization due to declining water quality and hydrological changes, but few studies have examined these taxa in cities. The northern dusky salamander (Desmognathus fuscus) was once common in the New York City metropolitan area, but has substantially declined throughout the region in recent decades. We used five tetranucleotide microsatellite loci to examine population differentiation, genetic variation, and bottlenecks among five remnant urban populations of dusky salamanders in NYC. These genetic measures provide information on isolation, prevalence of inbreeding, long-term prospects for population persistence, and potential for evolutionary responses to future environmental change. All populations were genetically differentiated from each other, and the most isolated populations in Manhattan have maintained very little genetic variation (i.e. < 20% heterozygosity). A majority of the populations also exhibited evidence of genetic bottlenecks. These findings contrast with published estimates of high genetic variation within and lack of structure between populations of other desmognathine salamanders sampled over similar or larger spatial scales. Declines in genetic variation likely resulted from population extirpations and the degradation of stream and terrestrial paths for dispersal in NYC. Loss of genetic variability in populations isolated by human development may be an underappreciated cause and/or consequence of the decline of this species in urbanized areas of the northeast USA.

城市化进程是导致两栖动物种群衰减的核心驱动因素。栖息于溪流的无肺螈科（Plethodontidae）蝾螈因水质下降与水文格局改变，对城市化胁迫尤为敏感，但目前针对城市生境中此类类群的研究仍较为匮乏。北部暗脊蝾螈（Desmognathus fuscus）曾广泛分布于纽约都会区，但近数十年来该区域内的种群数量已出现显著衰减。本研究选取5个四核苷酸微卫星位点（tetranucleotide microsatellite loci），对纽约市境内5个残存的城市生境暗脊蝾螈种群展开了种群分化、遗传变异与遗传瓶颈的分析。上述遗传指标可用于解析种群隔离程度、近交发生频率、种群存续的长期潜力，以及应对未来环境变化的进化响应潜能。所有种群之间均存在显著的遗传分化，其中位于曼哈顿岛的最隔离种群仅保留了极低的遗传变异水平（即杂合度低于20%）；多数种群均表现出遗传瓶颈的遗传信号。本研究结果与已发表的相关结论存在显著差异：此前在相似或更大空间尺度下采样的其他颊颚螈亚科（Desmognathinae）蝾螈种群，均表现出较高的内部遗传变异，且种群间无明显遗传结构。纽约市境内的种群局部灭绝事件，以及溪流与陆地扩散廊道的退化，可能是导致该种群遗传变异水平下降的主要原因。在美国东北部城市化区域中，受人类开发活动隔离的种群出现的遗传多样性丧失现象，可能是该物种种群衰减的一个被低估的诱因与/或伴随后果。