葱属宽叶组植物细胞分类学研究

百合科Liliaceae葱属Allium的宽叶组Sect．Anguinum包括5种3变种。通过对该组的5种1变 种的23个地方居群的研究,得出以下结果。(1)宽叶组植物的染色体基数为8,核型类型一致,为2A 型,染色体类型以及不对称系数都很相似。核型特征的共性表明该组是一个自然的分类群。(2)虽然 总体上组内的核型表现出较大的相似性,但在种间和种内各居群间也存在一定的差异。主要表现为：有 的种内存在染色体的倍性变化;B染色体的有无以及数目和形态,在种内不同居群间存在变化;随体染 色体上衔接随体的有无,在种间及种内都表现出多态性。(3)三倍体卵叶韭Allium ovalifolium高度不 育,靠新产生的地下走茎进行无性繁殖,以此扩大居群。(4)根据善葱A．victorialis分布区广而地史相 对古老的分布格局,推测它为本组的原始类群。它通过地理的(渐进的)物种形成方式,逐步演化形成现 在的各个分类群。(5)根据该组植物的分布格局和演化过程,提出我国横断山区至秦岭一带为本组植物的现代分布中心和分化中心。     

Some notes on the cytotaxonomy of two Ruppia species in South Australia

Chromosome counts were made from root tip cells of Ruppia megacarpa Mason (2n = 20 chromosomes) and of Ruppia tuberosa Davis and Tomlinson (2n = 20 and 3n = 30 chromosomes). The plants were collected in South Australia from coastal lakes, lagoons and the sea. The salinity in these waters varied from 6.9 to 67.9% total dissolved solids (TDS). We report the occurrence of Ruppia tuberosa in the tidal zone of the sea, and the occurrence of a triploid population of this species in a lagoon.     

A note on species richness and the variance of epidemic severity

Journal of Mathematical Biology - The commonly observed negative correlation between the number of species in an ecological community and disease risk, typically referred to as “the dilution...     

Aplysiid species from East Africa with notes on the Indian Ocean Aplysiomorpha (Gastropoda: Opisthobranchia)

Eleven species of the opisthobranch order Aplysiomorpha collected from East Africa and neighbouring parts of the Indian Ocean are described. Three of the species are new to science. The nineteen species of Aplysiomorpha which are reliably reported from the Indian Ocean are listed, together with a key for their identification.     

New developments in vertebrate cytotaxonomy VIII. A current list of references on avian karyology

A list of 256 references dealing with avian karyology is presented. This list is updated to April 1983 and covers 587 bird species, 385 non-passerines and 202 passerines. It includes 37 non-passerines and 29 passerines that were only studied in the period from 1902 onwards to the early 1950s using less sophisticated techniques (mostly on sectioned material of gonadal tissues). The remaining 348 non-passerines and 173 passerines were studied with more advanced techniques using colchicine-treated material of feather-pulp, embryonic tissue, bone-marrow, leucocyte or tissue culture. The species studied to date belong to 25 of the 26 avian orders and to 96 of the 160 avian families.This is the eighth in a series of articles, by different authors, to appear in this journal under the editorship of Professor Chiarelli, supplementing the data published in Cytotaxonomy and Vertebrate Evolution (A. B. Chiarelli & E. Capanna, eds. Academic Press, London & New York, 1973)-Eds.     

Karyotype evolution and cytotaxonomy in Brazilian species of Rhynchospora Vahl (Cyperaceae)

Karyotypes were analysed in 113 populations of 34 species of Rhynchospora (Cyperaceae). They showed typical holocentric chromosomes lacking primary constrictions. Nucleolar constrictions were observed in the terminal regions of a few chromosomes (except in R. nanuzae , in which they were interstitial). The chromosome numbers varied between 2 = 4 and 2n = 50. The primary base number seems to be x = 5; x = 6 and x = 9 are secondary. Dysploidy occurred at low frequency, whereas polyploidy seemed to be the predominant event in the karyotype evolution of the genus. Karyotypic differences were found in R. consanguinea var. speciosa and R. consanguinea var. rigida and the closely related R. emaciata, R. riparia and R. tenuis from section Tenues. On the other hand, karyotypic similarities occurred among sections Valderugosae, Marisculae, Stenophylku and Cemuae.