THE EFFECTS OF SOME ECOLOGICAL FACTORS ON CELL SIZE OF THE HOT SPRING ALGA SYNECHOCOCCUS LIVIDUS (CYANOPHYTA)1

Algae were sampled along temperature gradients of 30 thermal springs in Colorado, Idaho, Montana and Wyoming. From a maximum temperature of 74.5 C downstream, to ca. 62 C, the diversity of the algae was limited to the various forms of Synechococcus lividus Copeland; from ca. 62 to 40–45 C it coexisted with other algae. When S. lividus was in direct sunlight the mean length was greatest at the highest temperatures of its existence, becoming shorter as the water cooled; the mean reduction in length was 0.132 μm for each 1 C reduction in temperature. The cells in a shaded stream did not exhibit the reduction in size with reduced temperature, but remained about the same length from 73 C downstream to 45 C. The longer cells from the highest temperatures of their existence in any stream could not become established in the cooler water downstream, so the range of cell lengths (diversity) became less as the water cooled. Unknown dissolved substance(s) depressed the upper temperature limit in two streams and had a reverse effect on the expected length–temperature relationship; the shortest cells were at the higher temperatures. Generally, total dissolved substances had a positive effect on the length; the longest cells were in the water with the highest total dissolved solids (TDS) at the upper temperature limits of 70–74.5 C. In the temperature range of 55–60 C the higher TDS were not as effective in developing longer cells.     

EVOLUTION OF THE GENUS CHRYSOCOCCYX

Modern geological ideas on ocean-floor spreading are briefly reviewed. Pangea began to break up at the end of the Trias, but Africa, Antarctica and Australia remained together or close to each other till the end of the Cretaceous. The position of western New Guinea at the start of the Miocene could have been approximately where Arnhem Land is now, and at the start of the Pliocene somewhat north of the present-day Aru Islands. Its size until the end of the Pliocene was much smaller than it is today. Friedmann's proposal for the evolutionary spread of Chrysococcyx therefore demands that the whole process occurred since about the start of the Pliocene. There may not have been enough time in these seven million years for the evolutionary dispersal of a genus of parasitic cuckoos halfway round the world. His proposal also regards C. osculans as an awkward throw-back, and leaves a gap between species in New Guinea and southeastern Asia that is not bridged by intermediates. If a stock of cuckoos had been in Gondwanaland before it broke up, that stock could have given rise to the genus Cacomantis and the forerunners of C. osculans. The lineage of osculans would have quickly given rise to a lineage of glossy cuckoos that then divided into two branches. One could have penetrated Africa, south of where Madagascar then was, produced the species klaas, cupreus, caprius and flavigularis (an aberrant end-product), and much later, after Madagascar had drifted south from India (having been separate from Africa since the Cretaceous), colonised Asia where maculatus and xanthorhynchus would have differentiated. The other line could have differentiated, perhaps more slowly, in Australia into basalts, lucidus, ruficollis and malayanut (minutillus). When Australia had drifted near enough to the Malay Archipelago and as New Guinea grew, ruficollis and minutillus could have moved forward to colonise the islands, where minutillus would have produced the many races oimalayanus and meyerii differentiated as an aberrant end-product. This proposal overcomes some of the objections to Friedmann's theory because it arranges events to accord better with geological developments and avoids the evolutionary discontinuities of his proposal. The migratory habits of the cuckoos, thought by Friedmann to be significant, are discounted as evidence for evolutionary history. The parasitic habits are re-interpreted. Better data are presented for the parasitic behaviour of basalis and lucidus; they suggest that both species are sophisticated and probably host-specific parasites. Jensen & Jensen (1969) have already given evidence that some African glossy cuckoos are highly host-specific. There seems to be a trend of decreasing parasitic sophistication in Australian species, correlated with the possible age of the species. In Africa parasitism seems to be far in advance of that in Australia, probably because the opportunities for parasitism are far better in Africa. These trends and differences in parasitic behaviour are compatible with an evolutionary spread from Gondwanaland. The crucial question is whether the stock of Cacomantis and Chrysococcyx could have existed before the break-up of Gondwanaland, i.e. before the early Eocene. The present fossil record suggests that this is unlikely, but the paucity of fossils and the difficulties of palaeoclimates do not seem to be insuperable and it is suggested that a southern origin for these cuckoos should be considered seriously.     

中国麻黄属的地理分布与演化

中国现有麻黄属植物１５种,２变种和１变型,这些种属于膜果麻黄组和麻黄组中的麻黄亚组,没有原始类型藤麻黄亚组的代表。我国除长江中下游及珠江流域的省区处,其他省区都有分布。麻黄花粉的化石－麻分在地层中的分布说明,麻黄在过去曾遍布我国各地,发现的最早时期是在侏罗纪,到白垩纪－早第三纪时,种类较现在丰富,将近５０种,根据麻黄粉在世界各地地层中的分布和时期,结合大陆飘移和海底扩张板块构造学说推断,原麻黄在各     

EXPERIMENTAL EVOLUTION OF HSP70 EXPRESSION AND THERMOTOLERANCE IN DROSOPHILA MELANOGASTER

To examine whether recent evolutionary history affects the expression of Hsp70, the major heat-induced-heat shock protein in Drosophila melanogaster, we measured Hsp70 expression, thermotolerance, and hsp70 gene number in replicate populations undergoing laboratory evolution at different temperatures. Despite Hsp70's ancient and highly conserved nature, experimental evolution effectively and replicably modified its expression and phenotype (thermotolerance). Among five D. melanogaster populations founded from a common ancestral population and raised at three different temperatures (one at 18°C, two each at 25°C and 28°C) for twenty years, Hsp70 expression varies in a consistent pattern: the replicate 28°C lines expressed 30–50% less Hsp70 than the other lines at a range of inducing temperatures. This modification was refractory to acclimation, and correlated with thermotolerance: the 28°C lines had significantly lower inducible tolerance of 38.5°C and 39°C. We verified the presence of five hsp70 genes in the genome of each line, excluding copy number variation as a candidate molecular basis of the evolved difference in expression. These findings support the ability of Hsp70 levels in D. melanogaster populations to change over microevolutionary time scales and implicate constancy of environmental temperature as a potentially important selective agent.     

HERITABILITY OF EXPRESSION OF THE 70KD HEAT-SHOCK PROTEIN IN DROSOPHILA MELANOGASTER AND ITS RELEVANCE TO THE EVOLUTION OF THERMOTOLERANCE

The principle inducible heat-shock protein of Drosophila melanogaster, Hsp70, contributes to thermotolerance throughout the entire life cycle of the species but may also reduce fitness in some life stages. In principle, selection might maximize the benefits of Hsp70 expression relative to its costs by adjusting the magnitude of Hsp70 expression for each life-cycle stage independently. Therefore we examined whether the magnitude of Hsp70 expression varied during the life cycle and the relationship of this variation to several life-history traits. For 28 isofemale lines derived from a single natural population, estimates of heritable variation in Hsp70 expression ranged between 0.25 and 0.49, and the association among variation in first- and third-instar larvae and in adults correlated highly. Thus, Hsp70 expression is genetically coupled at these developmental stages. A line engineered with extra copies of the hsp70 gene produced more Hsp70 and survived heat shock much better than did a control strain. Among natural lines, Hsp70 expression was only weakly related to tolerance of heat shock and to larva-to-adult survival and developmental time at permissive temperatures. Additionally, lines with high adult survival developed slowly as larvae, which is a possible trade-off. These and other findings suggest that trade-offs may maintain quantitative variation both in heat-shock protein expression and in life-history traits that associate with thermotolerance.     

COLOR EVOLUTION IN THE HUMMINGBIRD GENUS COELIGENA

The remarkable diversity of coloration and species present in hummingbirds has been considered the result of sexual selection. I evaluate if color differences among species in the genus Coeligena are consistent with expectations from sexual selection theory. If sexual selection on color is important for speciation, closely related species should be markedly different in the colors of feather patches associated with aggression and breeding. I evaluate this prediction through a statistical assessment of the phylogenetic signal of colors from five feather patches: crown, gorget, belly, upper back, and rump. The first two are associated with aggressive and courtship displays and are expected to be under sexual selection, whereas the others are not. Contrary to expectations, the crown and gorget were the only patches with significant phylogenetic signal. Furthermore, I assess if populations of dichromatic species are more divergent in coloration and therefore have reduced gene flow. Color distances among dichromatic subspecies were larger than among monochromatic subspecies, but the magnitude of phenotypic differentiation was not related to levels of gene flow. These results support a role for sexual selection in shaping color variation among populations, but these differences alone are not sufficient to explain speciation.     

山茶属植物的进化与分布

山茶属Ｃａｍｅｌｌｉａ植物在其进化过程中,以雄芯不定数、在某些类群中存在心皮离生至合生的中间过渡,认为是山茶科中较原始的一属,分布于亚洲东部和东南部,中国长江以南广袤的亚热带地区是该属的现代分布中心,中南半岛和我国云南、广西南部的热带地区种类虽少,却集中了本属原始或较原始的类群和种类。本属演化上的近缘属或姐妹群－核果茶属Ｐｙｒｅｎａｒｉａ（包括石笔木属Ｔｕｔｃｈｅｒｉａ）分布区大致与本属相似,其原     

杜鹃属的系统发育与进化

本文以形态学为基础,结合一些新的有关资料,如解剖学、细胞学、化学等方面的证据讨论了杜鹃属的系统发育与进化问题,认为常绿杜鹃亚属在本属系统发育中处于原始地位,其中的云锦杜鹃亚组、耳叶杜鹃亚组、大叶杜鹃亚组和杯毛杜鹃亚组等4个亚组是原始类群,也即是其祖先的直接后裔。本属的原始祖先是具常绿习性,各部无毛(也无鳞片),花部不定数,具复合三叶隙构造的乔木,即类似现存原始类群的植物,它们生长于白垩纪至早第三纪古北大陆南缘,大约在我国西南部的热带山区森林环境中。随着地史的变迁,杜鹃属在漫长的进化过程中平行进化和发展为两个进化枝,一枝分化成各部被鳞片的热带附生类群或高山类群(包括4个亚属),另一枝演变为多少被毛的温带林下的半常绿至落叶类群(3个亚属),有鳞的髯花杜鹃组及落叶的日本马银组和落叶杜鹃组是两个进化枝演化上的高级类群。     

RANDOM-FRAGMENT HYBRIDIZATION ANALYSIS OF EVOLUTION IN THE GENUS NEUROSPORA: THE STATUS OF FOUR-SPORED STRAINS

A random-fragment hybridization method employing nuclear DNA has been developed to explore phylogenetic relationships in the genus Neurospora. Four cloned fragments and repetitive rDNA sequences were examined for restriction-fragment polymorphisms among 14 strains representing four species. The findings demonstrate that variation among randomly selected nuclear fragments can be employed to group related taxa with a higher degree of resolution than has been obtained with other DNA hybridization methods, isozyme electrophoresis, or restriction analysis of repetitive DNA. Based on our analysis of cloned fragments, we conclude that four-spored, secondarily-homothallic strains collected worldwide represent a monophyletic group. Trees constructed on the basis of restriction-fragment cataloging and coarse-structure restriction-site maps are for the most part consistent with the present mating-based species concept. We are encouraged that this method will provide an additional important experimental tool for evolutionary studies.     

鄱阳湖的中国水华蓝藻新记录属气丝藻属

2012年4月和10月在江西省鄱阳湖进行野外调查时, 发现一种浮游的丝状蓝藻。通过分离纯培养, 获得了6个纯化藻株。根据藻株主要形态学特征及其16S rRNA基因序列与比较, 鄱阳湖这些藻株与老挝的2株Aerosakkonema funiforme较为相近, 其中16S rRNA基因序列的相似度达到98%。鉴于这些藻株不同于颤藻目中其他属的藻株, 因此确定为我国一水华蓝藻新记录属气丝藻属Aerosakkonema Nanda Watanabe 2012, 模式种为索状气丝藻Aerosakkonema funiforme Nanda Watanabe 2012。       

金线鲃属鱼类的起源及其适应演化

根据地史和东亚地区鱼类区系演化史,推测了金线属鱼类的起源时代及其与当时古地质和古气候事件的关系,认为该类群的原始祖先可能在第三纪晚期已经存在于云贵高原一带;较系统地研究了金线属鱼类的洞穴适应演化趋势,表明该类群在穴居适应过程中既表现出穴居鱼类的共同演化趋势,也表现出其独特的穴居适应方式。       

DNA POLYMORPHISM WITHIN THE WH7803 SEROGROUP OF MARINE SYNECHOCOCCUS SPP. (CYANOBACTERIA)1,2

Genetic differences among ten strains of chroococcoid cyanobacteria (Synechococcus spp.) were identified by Southern blot hybridization. Data on shared number of restriction fragment length polymorphisms were used to identify the pattern and degree of genetic relatedness among the strains by two different methods of phylogenetic analysis. All the marine strains in the study contained phycoerythrin (PE) and cross-reacted with antisera directed against strain WH7803. Five contained a PE composed of phycourobilin (PUB) and phycoerythrobilin (PEB) Chromophores, and three contained a PE composed of only PEB chromophores. Two freshwater strains which do not contain PE and do not cross-react with the anti-WH7803 serum were included in the study for comparison. Dollo Parsimony analysis and cluster analysis showed that the WH7803 serogroup includes at least four widely separated genetic lineages. Strains within each lineages were closely related but the differences between lineages were as great as those between any of the marine lineages and the freshwater lineage. Strains cultured simultaneously from the same water mass were associated with different lineages. Thus, we conclude that natural assemblages of marine. Synechococcus are, at least occasionally, composed of individuals as genetically distinct from each other as members of different species or genera in other taxa.