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.

城市化是两栖动物种群衰退的主要诱因。栖息于溪流的无肺螈科（plethodontid）蝾螈因水质下降与水文格局改变，对城市化胁迫尤为敏感，但目前针对城市环境中该类群的研究仍较为匮乏。北部暗爪蝾螈（Desmognathus fuscus）曾广泛分布于纽约都会区，但近数十年来该区域内其种群已出现显著衰退。本研究采用5个四核苷酸微卫星（tetranucleotide microsatellite）位点，对纽约市境内暗爪蝾螈的5个残存城市种群展开分析，以探究种群分化、遗传变异水平以及种群瓶颈效应。此类遗传检测指标可反映种群隔离程度、近交发生频率、种群存续的长期前景，以及应对未来环境变化的演化响应潜力。所有种群彼此间均存在遗传分化，其中曼哈顿岛内最为孤立的种群遗传变异水平极低（即杂合度不足20%）。多数种群均呈现遗传瓶颈的遗传学证据。上述研究结果与已发表的相关结论存在显著差异：后者在相似或更大空间尺度下采样的其他无肺螈亚科蝾螈种群中，观测到较高的种群内遗传变异，且种群间无明显遗传结构。遗传变异水平的下降，大概率源于纽约市境内的种群局部灭绝，以及溪流与陆地扩散廊道的退化。受人类开发活动隔离的种群所出现的遗传多样性丧失，可能是美国东北部城市化区域内该物种衰退的一个未被充分认知的诱因，同时也是其衰退的后果之一。