半干旱区沙生植物繁殖对策

沙丘生态系统受到强烈的沙埋和风蚀干扰。虽然多数生态学家认为植物更倾向于借助繁殖对策适应干扰,但是沙生植物具备何种繁殖对策以适应风沙干扰鲜为人知。鉴于此,作者以生长在半干旱科尔沁沙地的典型沙生植物沙蓬(Agriophyllum squarrosum)、乌丹蒿(Artemisia wudanica)、芦苇(Phragmites communis)、黄柳(Salix gordejevii)为研究对象,通过开展系统研究,阐释了沙生植物2种提高繁殖体可获得性机制(抗远距离传播和繁殖体持续供应)、2种无性繁殖适应机制(“固守型”机制和“游走型”机制)、4种风蚀适应机制(流动沙丘上的有性繁殖机制、丘间低地的有性繁殖机制、沙丘上的有性+无性繁殖机制、丘间低地的无性繁殖机制)、4种繁殖与风沙活动互馈机制(风蚀和沙埋促进沙丘植物有性繁殖机制、风蚀和沙埋促进丘间低地植物有性繁殖机制、风蚀和沙埋促进沙丘植物无性繁殖机制、风蚀和沙埋调整丘间低地植物无性繁殖机制)。本文对生长在半干旱区的沙生植物的适沙繁殖对策进行了概念化和体系化总结。

Availability of Myoglobin as a Molecular Marker for Phylogenetic Relationships of Fish

In order to elucidate the phylogenetic relationship of fish, DNA and deduced amino acid sequences of myoglobin （Mb） were used for the phylogenetic analyses based on different approaches, namely, maximum likelihood （ML）, neighbor joining （NJ）, unweighted pair group method with arithmetic means （UPGMA） and maximum parsimony （MP） methods in comparison with the conventional molecular markers, mitochondrial cytochrome b （cyt-b） and cytochrome c oxidase subunit I （COI）. The phylogenetic trees drawn based on Mb sequences were similar to those by the traditional classification based on the other molecular markers. The primary and secondary structures, as well as the modeled tertiary structures of Mbs were similar to each other, but were clearly distinguishable among those species. Such differences in structure would be associated with adaptation of Mb molecule to the physiological conditions of each species. These results suggest that Mb can be a molecular marker for the phylogenetic relationship of fish.