Variation of Nuclear DNA Content in the Biflorus Species of Lonchocarpus (Leguminosae)

This represents the first study of nuclear DNA content in alarge sample (135 spp.) from a tropical arboreal genus, in whicha large proportion of the species were examined (42 spp., 31.1%).Somatic chromosome numbers and 4C-DNA values for 51 taxa ofLonchocarpus are reported. All taxa were diploid with 2 n =22,but their DNA content ranged from 1.92 to 2.86 pg 4C nucleus,corresponding to a 48.95% variation in genome size. In the 74collections studied, no correlation was observed between DNAcontent and habitat altitude. Variation in nuclear DNA contentwas analysed at the level of genus, subgenus, section and subsection.Variation in genome size was also studied within some species,either among widely separated populations or among differentintraspecific taxa. Very little variation in genome size wasdetected between populations, subspecies, and varieties of thesame species. The taxonomic implications of variation in nuclearDNA content are discussed.Copyright 2000 Annals of Botany Company Lonchocarpus (Leguminosae), DNA content, chromosome number.     

人类休闲活动对森林鸟类群落无有害影响

我们对西班牙马德里森林深处(未受到人类干扰)、森林小路沿线(间或有徒步旅行者经过)以及森林野餐区(有较持久干扰)的鸟类进行了调查,以查明人类休闲活动对该地区鸟类群落的分布和多度的影响.结合样方法对以上3类区域鸟类群落的总体特征(如:鸟类的多度、物种的丰富度和多样性)、不同鸟类群体的特征(如:鸦科鸟类的多度,营巢或者取食集团的特征)、各鸟种的多度等参数进行了比较.结果表明:小路沿线和野餐区样方内鸟类的多度和物种丰富度比森林深处更高,已查明14种鸟类的多度在人为干扰区域比森林深处高,只有5种鸟类的多度在森林深处更高一些;在树冠层筑巢的鸟类、在树干和地面觅食的鸟类及鸦科鸟类在休闲活动区有更高的多度;地巢性鸟类在休闲区的多度较低,这种差别尤以阔叶落叶林中加明显.而森林小路的鸟类群落结构与森林内部非常相似,说明人类休闲活动对这些林区鸟类群落的影响更多缘自野餐.原因是野餐区常常具有以下特点:具有高大的乔木、中层植被稀疏、有较多的洞和缝隙以及野餐后会遗留下一些垃圾.以上结论与研究的预期目标正好相反,人类的这些休闲活动可能会降低地巢性鸟类的适宜度,但是对大多数鸟的类栖息地没有不利影响.