The negative effects of habitat loss on biodiversity are undisputed,while the effect of habitat configuration,i.e.,the spatial arrangement of habitat area,has been debated for decades.To develop a more comprehensive u...The negative effects of habitat loss on biodiversity are undisputed,while the effect of habitat configuration,i.e.,the spatial arrangement of habitat area,has been debated for decades.To develop a more comprehensive understanding,it is important to know when and how configuration matters.In this study,we tested whether forest configuration influences the richness of species in groups characterized by varying shade tolerance in different ways and how such effects are related to habitat amount(i.e.,the percentage of forest cover)at the landscape scale.Based on 104 survey plots(each measuring 1km^(2))of vascular plants on the Swiss Plateau,and using two statistical approaches(i.e.,multiple regression and path analysis),we modeled the effects of habitat amount and configuration(measured as number of forest patches,total edge length,and proximity index)across all the plots and separately for three habitat amount classes:<10%,10%–30%,and>30%forest cover.When we modeled all plots together,we found that,after controlling for habitat amount,the forest configuration significantly affected species richness.When we considered the different habitat amount classes separately,most of the significant effects of habitat configuration on species richness occurred only for habitat amounts of<10%forest cover.Additionally,the response to forest configuration differed among species with different shade tolerances.When forest area was<10%,the effects of the number of patches and the total edge length on the species richness of light-demanding forest species were greater than the effect of habitat amount,whereas neither configuration metric affected the richness of shade-tolerant species.In conclusion,our findings highlight the importance of configuration in landscapes with a small amount of habitat.At the same time,they demonstrate that considering the confounding factors(e.g.species traits)is important for understanding the effects of forest configuration on biodiversity and that generalizations remain a challenge for landscape ecology.展开更多
Genetic diversity within and among six subpopulations of Larix decidua Mill. from two altitudinal transects of Swiss Alps was investigated using 6 enzyme systems coding for 8 loci. Globally, the mean proportion of pol...Genetic diversity within and among six subpopulations of Larix decidua Mill. from two altitudinal transects of Swiss Alps was investigated using 6 enzyme systems coding for 8 loci. Globally, the mean proportion of polymorphic loci was 22.9%, the average number of alleles per locus was 1.3, and the mean expected heterozygosity was 0.095. Only 5.8% of the genetic variation resided among populations. The mean genetic distance was 0.006. Several significant differences of gene frequencies were found between different age classes. Positive values of the species mean fixation index observed in this study suggested a considerable deficit of heterozygotes in the populations of L. decidua of Swiss Alps. At one of the sites (Arpette), the highest subpopulation in elevation gave the lowest level of genetic diversity (as evidenced by the lowest proportion of polymorphic loci and the lowest mean expected heterozygosity) and the largest value of genetic distance when compared to other subpopulations. The genetic differences between the highest subpopulation and the other ones suggest that the founder effect may be an important factor influencing genetic differentiation of L. decidua populations at Arpette transect.展开更多
基金Yiwen Pan holds a research grant from the China Scholarship Council(CSC)supported by the National Natural Science Foundation of China(grant no.31860120)。
文摘The negative effects of habitat loss on biodiversity are undisputed,while the effect of habitat configuration,i.e.,the spatial arrangement of habitat area,has been debated for decades.To develop a more comprehensive understanding,it is important to know when and how configuration matters.In this study,we tested whether forest configuration influences the richness of species in groups characterized by varying shade tolerance in different ways and how such effects are related to habitat amount(i.e.,the percentage of forest cover)at the landscape scale.Based on 104 survey plots(each measuring 1km^(2))of vascular plants on the Swiss Plateau,and using two statistical approaches(i.e.,multiple regression and path analysis),we modeled the effects of habitat amount and configuration(measured as number of forest patches,total edge length,and proximity index)across all the plots and separately for three habitat amount classes:<10%,10%–30%,and>30%forest cover.When we modeled all plots together,we found that,after controlling for habitat amount,the forest configuration significantly affected species richness.When we considered the different habitat amount classes separately,most of the significant effects of habitat configuration on species richness occurred only for habitat amounts of<10%forest cover.Additionally,the response to forest configuration differed among species with different shade tolerances.When forest area was<10%,the effects of the number of patches and the total edge length on the species richness of light-demanding forest species were greater than the effect of habitat amount,whereas neither configuration metric affected the richness of shade-tolerant species.In conclusion,our findings highlight the importance of configuration in landscapes with a small amount of habitat.At the same time,they demonstrate that considering the confounding factors(e.g.species traits)is important for understanding the effects of forest configuration on biodiversity and that generalizations remain a challenge for landscape ecology.
文摘Genetic diversity within and among six subpopulations of Larix decidua Mill. from two altitudinal transects of Swiss Alps was investigated using 6 enzyme systems coding for 8 loci. Globally, the mean proportion of polymorphic loci was 22.9%, the average number of alleles per locus was 1.3, and the mean expected heterozygosity was 0.095. Only 5.8% of the genetic variation resided among populations. The mean genetic distance was 0.006. Several significant differences of gene frequencies were found between different age classes. Positive values of the species mean fixation index observed in this study suggested a considerable deficit of heterozygotes in the populations of L. decidua of Swiss Alps. At one of the sites (Arpette), the highest subpopulation in elevation gave the lowest level of genetic diversity (as evidenced by the lowest proportion of polymorphic loci and the lowest mean expected heterozygosity) and the largest value of genetic distance when compared to other subpopulations. The genetic differences between the highest subpopulation and the other ones suggest that the founder effect may be an important factor influencing genetic differentiation of L. decidua populations at Arpette transect.
