Population dynamics of Dremomys pernyi and Callosciurus erythraeus in protective and non-protective pine forests at different ages

Four pine forests(6-10,11-15,16-20,and 31-40 year-old)located in the Cangshan Mountain and Erhai Lake National Reserve and 7 pine forests(1-5,6-10,11-15,1620,21-30,31-40,and more than 50 year-old)located in the non-protective area near the national reserve were selected.Three replications of each forest was set and a total of 33 sites were investigated.At each site,we quantified 6 habitat variables(species richness,abundance,and percentage of grasses and shrubs coverage respectively at the bottom layer of forests)within randomly determined 5 mx5 m areas.One hundred cages were set in five lines at each site to trap small mammals,whose species and numbers were recorded.Domi-nance of Dremomys pernyi and Callosciurus erythraeus in small mammal communities,time niche breadth,and time niche overlap between the two small mammals were calcu-lated,respectively.Step-wise regression was used to analyze the relationship between small mammals and habitat factors.Our results indicated that D.pernyi occurred earlier than C.erythraeus in protective pine forests.D.pernyi was captured in 6-10 year-old forest initially,and C.erythraeus was captured in 16-20 year-old forest initially.D.pernyi and C.erythraeus were captured in the 31-40 and 21-30 year-old forests initially in the non-protective area,respectively.Populations of D.pernyi and C.erythraeus in the 31-40 year-old protective forests were 3 and 3.75 times of those in the same-aged non-protective forests,respectively.Shrubs significantly influenced the populations of the two small mammals.The population of D.pernyi was positively correlated with the density of shrubs;the population of C.allosciurus erythraeus was positively correlated with the coverage of shrubs,and negatively correlated with the coverage of grasses.D.remomys pernyi and C.allosciurus erythraeus were important for pine forests to scatter pine seeds.Human activities in the non-protective pine forests decreased the vegetation heterogeneity at the bottom layer of pine forests,postponed the occurrence of D.pernyi and C.erythraeus,and decreased the populations of the two small mammals.

Preventing species invasion:A role for integrative taxonomy?

Integrative taxonomy,a multi-disciplinary approach adding modern techniques to traditional morphology-based methods(e.g.molecular and morphological criteria),can play an important role in bioinvasion research to identify introduced taxa,discover pathways of introduction and inform authorities to control and prevent fu­ture introductions.The present study is the first on introduced populations of Callosciurus,Asiatic tree squir­rels,known as potentially invasive species in Europe(Italy,Belgium and France).We combined molecular(mi­tochondrial DNA markers:CoxI,D-loop)and morphometric analysis on skulls,comparing them to the widest morphological and molecular datasets ever assembled for Callosciurus.Squirrels collected in Italy and Belgium share the same haplotypes and skull characteristics,but are conspicuously different from the French population in Antibes.Genetic data revealed close similarity between French squirrels and Pallas’s squirrels,Callosciurus erythraeus,from Taiwan,China.Italian and Belgian squirrels formed an independent taxonomic lineage in ge­netic analyses,whose taxonomic rank needs further investigation.The morphological and morphometric charac­teristics of these 2 populations are,however,similar to known specimens assigned to Callosciurus erythraeus.These results may indicate a common origin for the populations found in Belgium and Italy.In contrast,French specimens suggest an independent introduction event of squirrels originating from Asia.