| Migratory individuals explore and utilize non-homogeneously distributed biological resources on the spatial and temporal scale through migration behavior during their annual life cycle.However,different stages in the annual life cycle are not completely independent.The biological manifestation of organisms in a specific period is subject to not only the instantaneous constraints of environmental conditions on a local scale,but also to the cumulative effects from a series of biological processes in other life stages.To fully understand the potential driving force of individual behavior,we need not only to consider the special survival needs of individuals in each stage,but also need to master the laws of individual movement between themThe Swan Goose(Anser cygnoides)is an IUCN vulnerable species which is endemic in Asia.Its breeding grounds are mainly located on the Mongolian Plateau with unpredictable habitat conditions,and it moves to the Yangtze River for overwintering.In recent years,the significant decline of its population size,the severe degradation of habitats en route,and the low individual survival rate all indicate that this species is facing with extremely serious survival and development threats.At present,the Swan Goose has two biological migration routes,namely inland migration route and coastal migration route.In order to solve these ecological problems related to population connectivity,this study comprehensively uses genetic methods,species distribution modelling,satellite tracking and stable isotope analysis to conduct a hierarchical analysis for either the breeding-breeding populations or the breeding-wintering populations.Based on genetic methods,the results show that the genetic differentiation levels among sampling populations are generally low in the different breeding areas of Swan Geese.There is no obvious sex-biased dispersal pattern for Swan Geese,that is,both female and male individuals can disperse away,but there is no gender bias in the direction of dispersal.We found that individuals within a distance of 0-50 km have higher genetic similarity,confirming the generally accepted theory of site fidelity in geese.The genetic component of the coastal population is similar with that of individuals from South Korea and Minjiang Estuary in Fujian Province,China.This result corroborates the results of recent satellite tracking study on migration route division.The genetic distance between the coastal population and all other inland populations is slightly further,and the effective population size of the coastal population is about 21,which further proves the urgency of protecting this management unit.Based on satellite tracking data,we found that only 32%of the females Swan Geese participate in reproduction,and the breeding success rate is about 7%.At present,the transboundry Daurial ecoregion has the largest population summering group of Swan Geese.In this area,Swan Geese breed mostly in relatively scattered waters.While during the moulting period,they concentrated in large and medium-sized lakes,such as Hulun Lake,Buir Lake,Herlen River,and Khukh Lake.Among those tracking individuals that selected these four main moulting sites,Hui River in Inner Mongolia,China is the primary breeding source.This study also found that 87.5%of the successfully hatched females did not conduct moult migration.In addition,about 30%of the breeding geese in the Daurial region do not have loyalty to the moulting area.This may be related to the declining availability of moulting habitats caused by the continuous drought for this species in their summer areaBased on the integration of citizen science data and survey data,we make predictions about the potential distribution of Swan Geese during the moulting period.Subsequently,we assign the moulting provenance for wintering individuals and museums specimens via the Bayesian modeling of stable isotopes.According to the assignment results,wintering geese in Poyang Lake have multiple breeding origin.While the summering distribution range displays a law of gradually shrinking and shifting to the south by comparing assignment results for the specimens in different periods.We plot tracking data to verify the modelling power of our prediction.And it shows that the prediction accuracy is extremely high.This research innovatively combines four methods to study the population connectivity of the Swan Goose.The main results of our study will provide technical support for the dynamic protection of the Swan Geese.The rescaling relationship between feather and precipitation stable hydrogen isotope that established by our study will shed lights on the migration connectivity research of other waterbird species in East Asia,especially for those small-bodied species that cannot be satellite-tracked. |
