| A major hallmark of the Anthropocene is the rapid transformation of more natural biomes into human-dominated landscapes because of rapid population growth and accelerated urbanization,with the latter having a negative impact on biodiversity.Amphibians are facing a rapid decline worldwide.The latest International Union for Conservation of Nature(IUCN)Red List reported that 41% of amphibian species are threatened with extinction,rendering them the most threatened vertebrates compared with mammals(26%)and birds(14%).Habitat loss,degradation of habitat quality,and habitat fragmentation caused by urbanization are the main threats to amphibian populations.Rapid urbanization has resulted in phenotypic,genetic trait,and breeding behavior changes in species in response to new environments,with variations in acoustic signals being the most obvious.Acoustic signals are the main form of communication of most adult male frogs and have an important role in sexual selection and reproductive behaviors.Many studies have confirmed that anthropogenic noise and habitat changes have a significant impact on call signals of frog,the morphological of individuals and population dynamics of species also alter their call traits.However,few studies have focused on the adaptive changes of frog acoustic signals along the rural–urban gradient and how abiotic and biotic variables influenced by urbanization affect frog advertisement calls is less known.Additionally,it is generally believed that the vigilance behavior of animals will change with the increase of human activities,but few studies have focused on the effect of urbanization on the vigilance distance of amphibians.In this study,ornamented pygmy frog(Microhyla fissipes)and rice frog(Fejervarya multistriata)were seleted as the research subjects in Shanghai,we focus on the adaptive changes of frog acoustic signals and vigilance distance along the rural–urban gradient and how biotic and abiotic variables influenced by urbanization affect frog advertisement calls.The advertisement calls of individual males from the two frog species were recorded from May to July in 2020 and 2021 during their breeding season in 34 sampling sites(UrbanSuburban-Rural)in Shanghai,China.The call of each individual male frog was recorded for at least 5 minutes.In total,100 males M.fissipes and 89 males F.multistriata were recorded.In addition,we measured the vigilance distance of 100 males M.fissipes.We focus on 5 call parameters,including call duration(CD),call interval(CI),call rate(CR),pulse rate(PR),and dominant frequency(DF).We also explored how abiotic(air temperature,air humidity,and anthropogenic noise)and biotic(chorus size,individual weight,and snout–vent length of both species)variables related to urbanization affected these calls.The main results are as follows:(1)DF of M.fissipes and PR of F.multistriata were negatively related to increasing urbanization.(2)The vigilance distance of M.fissipes was negatively related to increasing urbanization.(3)DF of both species significantly increased with their chorus size.CD and CI of M.fissipes were negatively related to air temperature,while CR and PR were positively related to air temperature.Additionally,DF,PR,and CR of M.fissipes were positively related to air humidity,but CD of M.fissipes was negatively related to air humidity.PR of F.multistriata was positively related to air temperature.We found that,although these species have different responses to urbanization,the abilities of males to attract females may increase(i.e.,lower DF and PR)with increasing urbanization.The vigilance distance of M.fissipes was negatively related to increasing urbanization which indicates the adaptive change in response to urbanization.Besides,both biotic and abiotic variables influenced by urbanization affected advertisement calls of both species,but the changes in body size of frogs didn't significantly impact the advertisement calls of either species.The results of this study would help us to better understand the adaptive mechanism of anuran breeding behaviors and have a significant meaning for anurans biodiversity conservation in the face of rapid urbanization. |
PDF Full Text Request