Aims With the increase of land-use change,habitat fragmentation has become a major factor affecting plant diversity.Generally,when the adult density is high,the survival rate of conspecific saplings may decline and pr...Aims With the increase of land-use change,habitat fragmentation has become a major factor affecting plant diversity.Generally,when the adult density is high,the survival rate of conspecific saplings may decline and provide more resources and space for other species to maintain a high local species diversity.Therefore,the spatial relationship of conspecific saplings and adults(SRCSA)can regulate plant diversity.However,very few studies have assessed SRCSA within fragmented forests,and we still largely unknown the relationship between SRCSA and species diversity in fragmented landscapes.Methods We calculated the mean strength of SRCSA using the spatial distribution data of saplings and adults with a log-transformed hierarchical offset-power model on 27 islands in a land-bridge island system.The higher strength of SRCSA reflects a more negative relationship between the density of conspecific saplings and adults on an island(i.e.the looser pattern of SRCSA).We tested the relationships among island attributes(i.e.island area,the distance to the mainland—MD,and the distance to the nearest island—ND),SRCSA and species diversity.Important Findings The strength of SRCSA increased with ND.Meanwhile,the species diversity significantly increased with the strength of SRCSA,and island area and the strength of SRCSA independently explained 26%and 6%of variation of species diversity,respectively,and their interactions explained 8%.Shade-intolerant and low-abundant species showed looser patterns of SRCSA.Our study suggests that SRCSA may have the effect of excluding species with a relatively low abundance in isolated island forests,which illustrates the importance of biotic interactions in maintaining plant diversity in fragmented forests.Our results also emphasize that we should consider forest connectivity when testing the conspecific negative density dependence.展开更多
文摘利用相关序列扩增多态性(SRAP)分子标记法,对千岛湖片段化生境中14个岛屿上的黄足厚结猛蚁(Pachycondyla luteipes)种群遗传结构和多样性进行研究。利用5对SRAP引物对42份材料的基因组进行扩增,共得到大小在50—800 bp之间的71个可重复位点,其中63个为多态性位点,多态性比率达88.73%。AMOVA分析结果显示,65.03%的遗传变异存在于种群间,34.97%的遗传变异来自种群内(P<0.001)。利用PopGene Version 1.32软件对SRAP多态性数据进行分析,不同岛屿种群的多态位点比例和Nei's基因多样性指数变化范围分别介于35.21%—91.55%和0.2662—0.4905之间,平均值分别为58.25%和0.3729,其中多态位点比率最高的岛屿为面积最大的JSE岛。多态位点比例和Nei's基因多样性指数与岛屿面积、海拔均无显著相关性,但与隔离度呈显著正相关关系。种群间遗传分化指数介于0.0777—0.9328之间,平均值为0.4419,基因流值介于0.0360—5.9350之间,平均值为1.0451,种群间遗传分化程度较高,基因流较低。利用UPGMA聚类分析法对14岛屿上的42个个体进行遗传聚类分析,表明地理距离较近的个体和岛屿具有优先聚在一起的趋势。Mantel检验表明黄足厚结猛蚁各种群间地理距离与遗传距离间存在显著相关性(r=0.7757,P<0.01)。以上结果表明地理隔离是影响千岛湖黄足厚结猛蚁种群遗传结构和多样性的主要因素。
基金supported by the Key Research and Development Program of Zhejiang Province(No.2017C02028)the National Natural Science Foundation of China(No.31930073,31870401 and 31901104)+1 种基金the National Key Research and Development Project(2018YFE0112800)the Fundamental Research Funds for the Central Universities(2019QNA6002).
文摘Aims With the increase of land-use change,habitat fragmentation has become a major factor affecting plant diversity.Generally,when the adult density is high,the survival rate of conspecific saplings may decline and provide more resources and space for other species to maintain a high local species diversity.Therefore,the spatial relationship of conspecific saplings and adults(SRCSA)can regulate plant diversity.However,very few studies have assessed SRCSA within fragmented forests,and we still largely unknown the relationship between SRCSA and species diversity in fragmented landscapes.Methods We calculated the mean strength of SRCSA using the spatial distribution data of saplings and adults with a log-transformed hierarchical offset-power model on 27 islands in a land-bridge island system.The higher strength of SRCSA reflects a more negative relationship between the density of conspecific saplings and adults on an island(i.e.the looser pattern of SRCSA).We tested the relationships among island attributes(i.e.island area,the distance to the mainland—MD,and the distance to the nearest island—ND),SRCSA and species diversity.Important Findings The strength of SRCSA increased with ND.Meanwhile,the species diversity significantly increased with the strength of SRCSA,and island area and the strength of SRCSA independently explained 26%and 6%of variation of species diversity,respectively,and their interactions explained 8%.Shade-intolerant and low-abundant species showed looser patterns of SRCSA.Our study suggests that SRCSA may have the effect of excluding species with a relatively low abundance in isolated island forests,which illustrates the importance of biotic interactions in maintaining plant diversity in fragmented forests.Our results also emphasize that we should consider forest connectivity when testing the conspecific negative density dependence.
