MITOCHONDRIAL GENE TREES AND THE EVOLUTIONARY RELATIONSHIP OF MALLARD AND BLACK DUCKS

We assayed restriction site differences in mitochondrial DNA (mtDNA) within and among allopatric populations of the Mallard (Anas platyrhynchos) and the American Black Duck (A. rubripes). The observed mtDNA clones grouped into two phylogenetically distinct arrays that we estimate differ by about 0.8% in nucleotide sequence. Genotypes in one clonal array were present in both species, while genotypes in the other array were seen only in Mallards. In terms of the mtDNA “gene tree,” the assayed Mallards exhibit a paraphyletic relationship with respect to Black Ducks, meaning that genealogical separations among some extant haplotypes in the Mallard predate the species separation. Evidence is advanced that this pattern probably resulted from demographically based processes of lineage sorting, rather than recent, secondary introgressive hybridization. However, haplotype frequencies were most similar among conspecific populations, so the Mallard and Black Ducks cluster separately in terms of a population phenogram. The results provide a clear example of the distinction between a gene tree and a population tree, and of the distinction between data analyses that view individuals versus populations as operational taxonomic units (OTUs). Overall, the mtDNA data indicate an extremely close evolutionary relationship between Mallards and Black Ducks, and in conjunction with the geographic distributions suggest that the Black Duck is a recent evolutionary derivative of a more broadly distributed Mallard-Black ancestor.     

伊维菌素在环境中的降解及其对七种水生生物的急性毒性研究

伊维菌素作为一种高效的抗寄生虫兽药,在畜禽业有着广泛的应用。但药物随着畜禽动物的代谢产物的排放而进入自然生态系统也成为逐渐显现的环境问题。由于药物具有在自然环境中难以快速降解和对水生枝角类高毒性的特点,因此流入天然水体的伊维菌素存在着影响水生态平衡的风险。为了比较全面评估药物对水生动物潜在的毒害作用,研究模拟天然河道环境,对药物在底质中的降解速率进行了测定,并选取7种占据不同生态位的水生生物作为试验对象,通过关于急性毒性的国家标准试验方法来初步评价药物对水生态系统的风险。结果显示伊维菌素在自然水体中降解缓慢,在泥水混合25℃恒温条件下,70d的降解率仅为28.3%。急性毒性试验结果显示伊维菌素对发光细菌(Photobacterium)并不表现出毒性,对淡水小球藻(Chlorella vulgaris)的96h EC50=19.80 mg/L,属中毒;而对其他实验生物则表现出了较高的毒性,伊维菌素对斑马鱼(Brachydanio rerio)、食蚊鱼(Gambusia affinis)和鲫鱼鱼苗(Carassius carassius)的96h LC50分别为40.48、34.81和13.79μg/L,对罗氏沼虾(Macrobrachium rosenbergii)的96h LC50=7.87μg/L,对大型溞(Daphniamagna)的24h LC50=4.81 ng/L,均属极高毒。因此残留在天然水体的伊维菌素对水生态中的生物有较大影响,对含伊维菌素的废弃物排放进行监控和科学管理非常必要。     

VIABILITY OF SEEDS UP TO 211 YEARS OLD EXTRACTED FROM ADOBE BRICK BUILDINGS OF CALIFORNIA AND NORTHERN MEXICO

Seeds recovered from adobe walls of historic buildings in California and Northern Mexico were assayed for viability and germinability. Seven of the approximately 40 species tested had one or more viable seeds. These were (age of seeds in parentheses) Medicago polymorpha (200), Malva parviflora (200, 195, 183), Hordeum leporinum (200), Trifolium sp. (193), Melilotus indicus (183), Chenopodium murale (183), and C. album (143). Additionally, 41-yr-old seeds of Lotus corniculatus collected from living plants were found to be viable. Seeds of Medicago polymorpha and Lotus corniculatus germinated and produced normal seedlings. The importance of seed longevity in weedy species is briefly discussed.     

菽麻种子多糖的分离及应用

从菽麻种子里分离出一种半乳甘露多糖,mp.285℃,[a]_D~(25)+43.5,半乳糖和甘露糖的克分子比为1:2.3。该多糖和它的羧甲基衍生物与 Na_2B_4O_7KAl(SO_4)_2交联成冻胶,用作石油工业水基冻胶压裂液的原料。     

滑桃树种子的美登素类成分

从西双版纳产滑桃树(Trewia nudiflora L.)种子中分离鉴定了两个新的美登素类化合物,根据光谱数据推定它们的结构为10-表特利奴定(10-epitrenudine)和4′,5′-二乙酰特利奴定(4′,5′-diacetyl trenudine),后者为一工作产物。此外,还得到特利回生(trewiasine),特利福洛林(treflorine),特利奴定(trenudine)和咖啡因(caffeine)。     

MIGRATION AND DISPERSAL OF AUDOUIN'S GULL LARUS AUDOUINII FROM THE EBRO DELTA COLONY

Oro, D. & Martinez, A. 1994. Migration and dispersal of Audouin's Gull Larus audouinii from the Ebro Delta colony. Ostrich 65:225-230.

Migratory paths and dispersal patterns of Audouin's Gulls (Larus audouinii) born in the Ebro Delta have been studied, as well as their degree of philopatry. The gulls always disperse southwards from the colony, and only the juveniles seem to disperse in other directions. Dispersal patterns of 2y, 3y and older gulls are similar, wintering mainly on Iberian Mediterranean and Moroccan Atlantic coasts. Juveniles migrate before the rest of the age classes and they winter south of older gulls, in the Senegambia region. However, conclusions on Audouin's Gulls movements are difficult to draw, owing to the large differences in resighting and recovery efforts. Data presented also suggest that Audouin's Gulls do not appear to breed before the age of four years.     

TISSUE PREPARATION AND FINE STRUCTURE OF THE RADICLE APEX FROM COTTON SEEDS

A comparative methodological study was made of the fine structure of apical cortical cells in excised radicles from cotton (Gossypium hirsutum L. var M-8) seeds. Radicles from dry seed had 12% moisture content and were prepared for electron microscopy using several different techniques. These included different methods of chemical fixation or freeze-fracture and etching of unfixed tissue for transmission electron microscopy (TEM) and cryofracturing of fixed and dehydrated radicles for scanning electron microscopy (SEM). Cortical cells had a similar appearance regardless of the method used in tissue preparation. Cell walls had a pronounced waviness which was particularly evident in SEM images of cells lining the elongated intercellular air spaces. The plasma membrane (PM) delimited the cytoplasm of each cell as an intact unit membrane. Single layers of tightly-packed lipid bodies (LB) were apposed to the PM and protein bodies (PB). Distension of cells, membranous organelles and LB was observed in radicles fixed by immersion in aqueous solutions, suggesting that a certain amount of hydration occurred during fixation. This interpretation was supported by the compact appearance of cells and organelles in tissue prepared by freeze-etch or vapor fixation. We conclude that freeze-fracture and etching of unfixed tissue provided the best information for cell morphology and structure of membranes and organelles in dry tissue. Complementary data on the fine details of nuclei and cytoplasmic organelles were best observed with TEM of fixed tissue. These data when viewed collectively indicate the advantage of using several techniques to obtain analogous and complementary information essential for establishing a baseline level of information on the fine structure of cells in dry tissue.