Human disturbances are considered to break reproduction barriers among species. Significant increases in hybridization events have been reported among a large number of taxonomic groups in anthropogenic environments, providing novel insights into species evolution mechanisms and conservation management in the Anthropocene. The Eastern Golden Frog (Pelophylax plancyi) and Black-Spotted Frog (P. nigromaculatus) are two sympatric anuran species with a long history of mitochondrial genome introgression in highly urbanized continental East Asia. However, there is only limited understanding of the pattern of their contemporary hybridization and factors influencing their interspecific relationship under anthropogenic disturbances. Here, interspecific hybridization between P. plancyi and P. nigromaculatus at the population level was investigated in Shanghai. All except two haplotypes obtained from both species in Shanghai were mixed together, and located in the introgression clade, implying multiple ancient mitochondrial introgression events occurred in the populations of our study area. Asymmetric genetic introgression was detected by microsatellite markers, with 0.7% of P. plancyi and 14.6% of P. nigromaculatus identified as contemporary admixed individuals. Consistent with the trend of population density, higher genetic diversity of neutral microsatellite loci was found in the more abundant P. plancyi; however, variation in mitochondrial (Cyt-b) and nuclear (POMC) genes was higher in relatively rare P. nigromaculatus. The population density of P. plancyi and number of water patches within local habitats were significantly positively correlated with both occurrences and proportions of admixed individuals in the populations of P. plancyi and P. nigromaculatus. Considering the prevalent transformation of habitats in urbanized areas, these results imply that a high population density in isolated artificially altered habitats is likely to increase interspecific hybridization. Thus, population monitoring and improvement of landscape connectivity between habitats would be needed to control the intensity of interspecific hybridization between P. plancyi and P. nigromaculatus in anthropogenic-disturbed environments.

Aims: Habitat fragmentation and loss caused by urbanization are important factors that threaten the survival of wildlife globally.Urbanization has caused amphibians to become one of the most severely threatened groups of terrestrial vertebrates.Studying the spatial distribution pattern and exploring how landscape connectivity affects the gene flow among fragmented populations of amphibians in urban areas would provide a deeper understanding of the impacts of urbanization on wildlife and offer theoretical guidance for local biodiversity conservation.Methods: In this study, we selected the eastern golden frog (Pelophylax plancyi) as the primary research subject and obtained landscape and environmental data about land cover, normalized difference vegetation index (NDVI) and land surface temperature in the Shanghai region using Landsat-8 satellite images (http://www.gscloud.cn).Combined with the data from field population survey, we employed the maximum entropy (MaxEnt) model to predict the spatial distribution pattern of P. plancyi in the region.We evaluated the potential corridors and calculated the resistance distances between local populations using circuit theory (Circuitscape), and explored the effect of geographical and resistance distance on genetic differentiation among local populations using the Mantel test of each local populations based on the genetic distance (F ST ) matrices calculated from simple sequence repeat (SSR) and single nucleotide polymorphism (SNP).Results: The habitat suitability of P. plancyi significantly decreased along the rural-to-urban gradient.NDVI was the main factor affecting the MaxEnt modelling and indicated that the P. plancyi prefer to inhabit areas with higher vegetation coverage.There was no significant correlation between genetic distance and geographical distance, while genetic distance increased significantly with the resistance distance. Conclusions:The protection and maintenance of continuous suitable habitats in suburbs and isolated habitat patches in urban areas that still exist is the primary measure of conservation for native amphibians such as P. plancyi.Furthermore, optimizing urban landscape structure, strengthening the construction of corridors suitable for various groups of wildlife, and promoting the gene exchange among local populations are effective methods to achieve the self-sustainment of populations and long-term conservation of biodiversity in urbanized areas.

本研究使用GPS卫星跟踪技术,以本地区最常见的斑嘴鸭(Anas poecilorhyncha)(5只)和绿头鸭(A.platyrhynchos)(4只)为研究对象,研究了冬季斑嘴鸭和绿头鸭在浦东的栖息地空间利用特征.利用固定核空间法(FKE)测得越冬季个体的平均活动范围为(15.073 士 25.390)km2,没有明显的种间差异.两种鸭属鸟类的主要栖息地类型为滩涂、沟渠、农田和内陆水体,观测到的利用率分别为38.45％、32.46％、19.88％和8.85％,滩涂和沟渠是最主要的栖息地类型且昼、夜均利用.农田是研究区域主要的栖息地类型,是鸭属鸟类冬季重要的取食地,但只有部分个体使用,且多在夜间.所有监测个体均在夜间保持较高的活动强度,且活动高峰出现在清晨与黄昏.本研究比较系统地揭示了上海地区冬季斑嘴鸭和绿头鸭的栖息地利用和活动节律、活动范围等时空特征,为高度城市化地区的鸟类保护和管理提供了基础资料.

Abstract Understanding the mechanisms of how urbanization influences the evolution of native species is vital for urban wildlife ecology and conservation in the Anthropocene. With thousands of years of agriculture‐dominated historical urbanization followed by 40 years of intensive and rapid urbanization, Shanghai provides an ideal environment to study how the two‐stage urbanization process influences the evolution of indigenous wildlife, especially of anuran species. Therefore, in this study, we used mitochondrial Cyt‐b gene, microsatellite (SSR), and single nucleotide polymorphism (SNP) data to evaluate the demographic history and genetic structure of the eastern golden frog (Pelophylax plancyi), by sampling 407 individuals from 15 local populations across Shanghai, China. All local populations experienced bottlenecks during historical urbanization, while the local populations in urban areas maintained comparable contemporary effective population sizes (Ne) and genetic diversity with suburban and rural populations. Nevertheless, the rapid modern urbanization has already imposed significant negative effects to the integrity of populations. The 15 local populations were differentiated into eight genetic clusters, showing a spatial distribution pattern consistent with the current urbanization gradient and island–mainland geography. Although moderate gene flow still occurred from the rural peripheral cluster to urban and suburban clusters, population fragmentation was more serious in the urban and suburban populations, where higher urbanization levels within 2‐km radius areas showed significant negative relationships to the Ne and genetic diversity of local populations. Therefore, to protect urban wildlife with limited dispersal ability, improving conditions in fragmented habitat remnants might be most essential for local populations living in more urbanized areas. Meanwhile, we highlight the need to preserve large unfragmented rural habitats and to construct corridor networks to connect discrete urban habitat remnants for the long‐term wildlife conservation in intensively urbanizing environments.

两柄动物是衡量城市生态系统环境质量的指标类群.郊野公园是上海城市生态系统中重要的两栖类栖息地.2015年5-9月,采用样线法对上海市6个郊野公园的无尾两栖类物种种群数量进行调查,采用样方法采集15种微生境变量数据.通过主成分分析和冗余分析了解各无尾两栖类物种对微生境因子的利用特征,并用卡方适合度检验分析无尾两栖类的不同种间分布重叠度.结果表明,优势度由高到低为泽陆蛙Fejervarya multistriata、金线侧褶蛙Pelophylax plancyi、中华蟾蜍Bufo gargarizans、饰纹姬蛙Microhyla fissipes、黑斑侧褶蛙P.nigromaculatus,适宜的水质和结构合理的水生植被是其生存、繁衍的基础,坡度较小的自然坡岸是无尾两栖类自由往返水陆之间的重要保障.陆生植被的重要性次于水生植被,仅与金线侧褶蛙和黑斑侧褶蛙的分布有显著正相关.不同无尾两柄类物种对水体大小的适应能力不尽相同,郊野公园的水体比较开阔,不利于饰纹姬蛙的生存.本研究建议根据不同无尾两栖类的栖息地利用特征,建设具有不同物种特异性的栖息地景观,在保护好无尾两栖类的同时进一步提升公共绿地的综合生态服务效能.