THE PHYSIOLOGICAL ECOLOGY OF REPTILIAN EGGS AND EMBRYOS. AND THE EVOLUTION OF VIVIPARITY WITHIN THE CLASS REPTILIA

1. Eggs of Crocodilia and Chelonia, like those of birds, have a pair of egg membranes separating a thick layer of albumen from the calcareous shell. In contrast, eggs of oviparous Lepidosauria have only a single shell membrane, upon which relatively small amounts of calcium carbonate are deposited; and the volume of albumen in eggs is extraordinarily small at the time of oviposition. 2. With the possible exception of certain geckos and some chelonians, eggs of oviparous reptiles seem always to absorb water from the substrate during the course of normal incubation. In so far as the rate of water absorption exceeds the rate of water loss by transpiration from exposed surfaces, the eggs swell during incubation. The term ‘cleidoic’ cannot be used to describe eggs of this type. 3. Embryos of lizards and snakes influence the water potential of extra-embryonic fluids contained within their eggs, thereby maintaining or increasing the gradient in water potential that drives water absorption. 4. Embryos of Crocodilia and Chelonia obtain a substantial portion of the calcium used in ossification of skeletal elements from the inner surfaces of the eggshell. In contrast, embryonic lizards and snakes draw upon extensive reserves of calcium present in the yolk, and obtain little (if any) calcium from the eggshell. 5. All reptilian embryos seem to produce substantial quantities of urea as a detoxification product of protein catabolism. Contrary to expectation, uricotelism may not be common among reptilian embryos, even in those few instances where development takes place within a hard, calcareous egg. 6. In eggs of Crocodilia and Chelonia, respiratory gases seem to pass by diffusion through pores in the calcareous eggshell and through spaces between the fibres of the pair of egg membranes. No pores have been observed in the shell of lepidosaurian eggs, and so gases presumably diffuse between the fibres of the single (multilayered) shell membrane. 7. Metabolism of reptilian embryos is temperature-dependent, as is true for most ectothermic organisms. For each species, there appears to be a particular temperature at which embryonic development proceeds optimally, and departures from this optimum elicit increases in developmental anomalies and/or embryonic mortality. 8. Viviparity has evolved on numerous occasions among species of the Squamata, but seemingly never among Crocodilia or Chelonia. Since the evolution of viviparity entails a progressive reduction in the eggshell, only those organisms whose embryos do not depend upon the eggshell as a source of calcium may have the evolutionary potential to become viviparous. 9. Evolutionary transitions from oviparity to viviparity could have been driven by selection related to (i) thermal benefits to embryos consequent upon retention of eggs within the body of a parent capable of behavioural thermoregulation; (ii) protection of the eggs from nest predators and/or soil microbes; and (iii) more effective exploitation of a seasonal food resource by early emerging young.     

线粒体DNA聚合酶的起源与演化

随着新的DNA聚合酶A家族成员的加入,家族内部的系统发育关系需要重新检查,来自大肠杆菌DNA聚合酶I(DNA Pol I)和它的细菌、噬菌体和真核细胞同源物被用来重建这个家族的系统发育史.分析显示:在真核生物演化的不同阶段,线粒体DNA聚合酶基因可能通过水平基因转移方式起源于不同类群的生物.原始真核生物线粒体DNA聚合酶基因可能来源于细菌,植物线粒体DNA聚合酶基因可能从质粒获得,而真菌和动物线粒体DNA聚合酶基因可能起源于T3/T7相关噬菌体.     

PHYLOGENY AND BIOGEOGRAPHY OF CONDEEUM GROUP (PROTURA: PROTENTOMIDAE)

Abstract  Using the Hennig 86 phylogenetic analysis program to analyse the taxa in genera related to Condeellum , the phylogenetic relationships among the species are schemed on the basis of potential synapomorphies of the adults, represented by 16 characters. The character evolution and the route of dispersal are also discussed. The cladistic biogeographic analysis is performed. The basal taxon Condeellum exhibits an Indo-Pacific distribution and the sister group Neocondeellum species exhibit a collective Oriental and Holarctic distribution. The distribution patterns and the vicariance events occurred in those areas are hypothesized.     

基于线粒体控制区序列探讨豹属分子系统发生关系

为探讨豹属Panthera物种间的系统发生关系,测定了虎Panthera tigris、豹Panthera pardus和雪豹Panthera uncia的线粒体控制区全序列,结合其它5种猫科动物的同源序列进行分析。分别采用最大似然法(Maximum Likelihood,ML)、邻接法(Neighbor-Joining,NJ)和贝叶斯法(Bayesian Inference,BI)重建了豹属物种的分子系统发生树。结果表明:豹属除由传统的物种狮Panthera leo、虎P.tigris、豹P.pardus、及美洲虎P.onca组成外,雪豹P.uncia应并归于豹属,不支持将雪豹另立为雪豹属Uncia的观点;云豹Neofelis nebulosa与豹属具有最近的亲缘关系而构成其姊妹群物种;云豹与豹属Panthera各物种间的系统发生关系为:云豹(豹(虎(狮(美洲豹、雪豹))))。     

康蚖群的系统发生和生物地理学的研究(原尾目:始蚖科)(英文)

应用HENNIG86系统发生分析程序,选择出成虫的有代表性的16个共同衍征,分析了与康蚖属相关各属的各个种类,得出了该类群的相关系统树。同时对特征的演化以及其扩散途径等也进行了讨论。文中还应用Page 1993的COMPONENT程序进行了生物地理学的分析;得到种类—地区支序图。其中康蚖属表现为典型的印度—太平洋分布型,而其姐妹群新康蚖属则兼有东洋区和全北区的分布型。至于分布地区的相互关系和在这些地区的分衍替代事件的发生等问题也作了初步的假想。     

EVOLUTION,PHYLOGENY, SEXUAL DIMORPHISM AND MATING SYSTEM IN THE GRACKLES (QUISCALUS SPP.: ICTERINAE)

According to theory, two consequences of sexual selection are sexual dimorphism in size and secondary sexual characteristics, due to either intra- or intersexual selection. In this paper I suggest three criteria for the test of an evolutionary hypothesis involving quantitative morphological characters. First, the postulated change must be shown to have occurred in evolutionary time. Second, this change must be positively correlated with a change in the proposed selective agent. Third, given two taxa with different degrees of sexual size dimorphism and different mating system, the possible influence of drift must be rejected. If the hypothesis is not rejected by these three criteria, then we still have no proof of causality, but we can at least be more confident about its plausibility. This is applied to the particular hypothesis that sexual dimorphism in the Boat-tailed and Great-tailed grackles (Quiscalus spp; Icterinae; Aves) is caused by the highly polygynous mating system in these species. In relation to an outgroup, both species have increased disproportionately in male tarsus and tail size, creating an increased sexual dimorphism. This has cooccurred with the evolution of their particular mating system. However, the variance among species in male tarsus size can be accounted for by drift, and need not be a result of selection for increased size. In contrast, the variance among species in male tail size was much larger than expected under a null model of drift, indicating directional selection for long tails. The variance in female tail size was not larger than expected by drift, whereas the variance in female tarsus size was in fact lower than expected by drift, indicating stabilizing selection. The data are consistent with the hypothesis with regard to tail size, but not with regard to body size.     

PRELIMINARY STUDY ON MITOCHONDRIAL CYTOCHROME b DNA SEQUENCES AND PHYLOGENY OF FORMALIN FIXED SISORID FISHES (Teleostei:Siluriformes)

从９种科鱼类的福尔马林标本中获得了３３３ｂｐ的细胞色素ｂ基因片段的序列。这９个种分别代表科鱼类的８个属。３３３ｂｐ的ＤＮＡ序列经ＭＵＳＴ软件排序后,有１０１个变异位点,其中有３９个信息位点。序列在成对物种间的距离为８～４８。平均遗传距离为２４％～１４４％。简约分析产生了最大简约系统树,其步长是１６２（ＣＩ＝０７３５,ＲＩ＝０４９４）。在该系统树上,Ｂａｇａｒｉｕｓ是最原始的属,并与所有其他的物种形成姊妹群。其余８个属形成一个单系类群并分为二个姊妹群。尽管在形态上具有１３个离征,但在分子系统树上,鱼类并未形成一个单系类群。可能的原因是３３３ｂｐ序列中的星系信息位点太少;另外单从福尔马林浸制标本获得的ＤＮＡ序列的可靠性尚有待进一步验证     

MITOCHONDRIAL DNA VARIATION AND EVOLUTION OF THE DEATH VALLEY PUPFISHES (CYPRINODON,CYPRINODONTIDAE)

A phylogenetic analysis of mitochondrial DNA (mtDNA) restriction sites was used to examine the geographic history of the Cyprinodon nevadensis complex of pupfishes, a group of four species (seven extant subspp.) in two endorheic (closed) basins of the Death Valley System in California and Nevada (Owens River Valley and Ash Meadows-Death Valley). The mtDNA results suggest that the group contains mtDNAs from two divergent clades. One such clade is represented by the mtDNAs of the Owens Valley pupfish (C. radiosus) and the existing species in the Colorado River (C. macularius), while the other includes the mtDNAs of the Ash Meadows-Death Valley species (C. nevadensis, C. salinus, and C. diabolis) and a species located much farther to the east (C. fontinalis from the Guzman Basin, Chihuahua, Mexico). These results, together with evidence from other studies, suggest two separate invasions of the Death Valley System by pupfishes carrying phylogenetically divergent mtDNAs. The C. nevadensis complex apparently is either an artificial group or else it is monophyletic and its genetic history includes loss of the original mtDNA in either Owens Valley or Ash Meadows-Death Valley following genetic introgression after an invasion by a pupfish carrying a divergent mtDNA.     

FOUNDER EFFECTS AND THE RATE OF MITOCHONDRIAL DNA EVOLUTION IN HAWAIIAN DROSOPHILA

The nearly-neutral-mutation theory predicts that populations with small effective sizes will undergo more rapid molecular evolution than populations with very large effective sizes. In particular, Ohta (1976) predicted that populations of Hawaiian Drosophila that are known to have small population sizes and to experience repeated population bottlenecks due to founder events should show a more rapid rate of molecular evolution relative to the rate of molecular evolution of species with large population sizes such as the continental Drosophila. In this paper we test this prediction by comparing the rate of molecular evolution in two closely related lineages of Hawaiian Drosophila that have experienced very different evolutionary histories. Both lineages belong to the planitibia subgroup of Hawaiian Drosophila. The beta lineage (which includes D. silvestris, D. planitibia, D. differens, and D. hemipeza) has undergone repeated founder events, as evidenced by their geographic distribution and behavioral biology. On the other hand, evidence on geographic distribution and behavior indicates that the alpha lineage (which includes D. melanocephala, D. cyrtaloma, and D. neoperkinsi) has arisen from large ancestral populations without founder effects. The mitochondrial DNA data reveal that, within a lineage, the rate of molecular evolution is rather uniform, while all comparisons between the two lineages show that the rate of molecular evolution in the beta lineage is three times that of the alpha lineage. This analysis strongly supports the predictions made by Ohta.     

GENE FLOW AND MITOCHONDRIAL DNA VARIATION IN THE KILLIFISH,FUNDULUS HETEROCLITUS

Two subspecies of killifish, Fundulus heteroclitus, inhabit the Atlantic coast of the United States. The contact zones between them are typified by morphological, physiological, nuclear gene, and mitochondrial DNA clines. Considerable debate exists about the importance of restricted gene flow and natural selection in maintaining these clines. To evaluate the relative importance of these two evolutionary forces we employed analysis of mtDNA as an independent measure of gene flow. Solutions of equilibrium diffusion equations suggested that killifish dispersal must be less than 2 km to maintain previously observed allozyme frequency clines in the absence of strong selection. To determine whether populations separated by distances greater than 2 km accumulate significant genetic differences we examined a total of N = 480 individuals from five killifish populations spanning a continuous shoreline distance of 8.4 km. Distribution of the 25 detected haplotypes indicated that most of the variation was within rather than between sampling locations. No evidence of geographic structure was detected, nor were there any significant genetic differences between killifish populations. With these data, gene flow was evaluated by estimating effective migration rate (N_em) between the populations. N_em was estimated from G_st(N_em = 49.4), from F_st (N_em = 24.1), by the private alleles approach (N_em = 18.5) and via four phylogenetic analyses (N_em ranged from 11.4 to 16.9). Regardless of the analysis, N_em was greater than one; the threshold level at which gene flow is strong enough to prevent differentiation due to genetic drift. This suggests that while the characteristics that distinguish Fundulus subspecies may have arisen in isolation, the current clinal distributions exhibited along the Atlantic coast are most likely maintained by selection.     

FEMALE FECUNDITY IN A HYBRID ZONE BETWEEN TWO CHROMOSOME RACES OF THE SCELOPORUS GRAMMICUS COMPLEX (SAURIA,PHRYNOSOMATIDAE)

Individuals of the F5 and FM2 cytotypes of the Sceloporus grammicus complex form a narrow zone of parapatric hybridization near Tulancingo, Hidalgo, Mexico. Reproductive parameters were examined among chromosomally parental and hybrid females to assess the degree to which reduced clutch size is correlated with the level of chromosomal heterozygosity. Although clutch size in the two parental groups was highly correlated with female body size, this was not the case for females with intermediate karyotypes. These females displayed increased levels of infertility manifested as smaller clutches and as inviable embryos. F₁ females produced the smallest average clutches and suffered the most precipitous fecundity loss (up to 75%). The number of heterozygous marker chromosomes and heterozygosity at chromosome 2 had significant effects on the number of viable embryos. Analysis of embryo karyotypes revealed the production of triploid offspring and an excess number of embryos heterozygous at chromosome 1. Differences in viability, among females heterozygous for the same number of chromosomes, suggest that genetic background of the female and/or sire may be an important factor in determining reproductive success.     

天牛科昆虫高级分类阶元实体的进化研究(英文)

本文从生物地理学、形态学、生态学、行为学、生理学、天牛—寄主植物的相互关系、地质学、气候变迁等诸方面,探讨了天牛科高级分类阶元实体的进化证据,提出了各阶元实体进化关系的新假说。研究结果表明,沟胫天牛亚科、锯天牛亚科和天牛亚科可能于侏罗纪在冈瓦纳古陆上分化出来;花天牛亚科和幽天牛亚科于白垩纪在劳亚古陆上分化出来。各亚科的进化顺序有两种可能:(1)沟胫天牛亚科、锯天牛亚科、天牛亚科、花天牛亚科、幽天牛亚科;(2)沟胫天牛亚科、天牛亚科、锯天牛亚科;花天牛亚科、幽天牛亚科。文章最后还讨论了各亚科的系统发育关系。     

樟科木姜子属群的起源与演化

论述了樟科木姜子属群的起源与演化,认为该属群起源于古北大陆南部和古南大陆北部,以及古地中海周围热带地区,起源时间不早于中白垩纪。这一自然属群明显存在着平行进化情况,其核心的木姜子属和山胡椒属极可能是同地起源于共同祖先,我国南部至印度马来西亚可能是这两属的起源和分化中心,并从这里向热带美洲及大洋洲扩散。其余的属可能从这一核心演化出来。     

THE GENETIC STRUCTURE OF A HYBRID ZONE BETWEEN TWO CHROMOSOME RACES OF THE SCELOPORUS GRAMMICUS COMPLEX (SAURIA,PHRYNOSOMATIDAE) IN CENTRAL MEXICO

The F5 (2n = 34) and FM2 (2n = 44–46) chromosome races of the Sceloporus grammicus complex form a parapatric hybrid zone in the Mexican state of Hidalgo, characterized by steep concordant clines among three diagnostic chromosome markers across a straight-line distance of about 2 km. Here, we show that this zone is actually structured into local patches in which hybridization extends over an extremely irregular front. The distribution of hybrid-index (HI) scores across the transect reveals some hybridization at almost all localities mapped in a central 7 km × 3 km area. Pooling the central samples produces both a strong heterozygote deficit for all diagnostic markers and strong linkage disequilibria between all pairwise combinations of these (unlinked) markers. Moreover, a highly significant association exists between the habitat on which each individual was caught and its karyotype (F5 chromosomes are more likely to be found on oak). Analysis of genotype frequencies over a range of spatial scales shows that there is no significant heterozygote deficit or habitat association within local areas of less than about 200 m; however, there is significant linkage disequilibrium over the smallest scales (R = D (pquv)^1/2 = 0.29, support limits, 0.18–0.36) over 100 m. These patterns suggest that lizards mate and choose habitats randomly within local patches. This conclusion is supported by mark-recapture estimates of dispersal (≈ 80 m in a generation) and by inference of matings from embryo and maternal karyotypes. Closer examination of the two-dimensional pattern reveals a convoluted cline for all three markers, with a width of 830 m (support limits 770 m–930 m). This cline width, combined with the strength of local linkage disequilibrium, implies a dispersal rate of σ = 160 m in a generation and an effective selection pressure of 30% on each chromosome marker. The proportion of inviable embryos is greater in females from the center of the hybrid zone; this is caused by effects associated with both karyotype and location. The hybrid zone is likely to be maintained by selection against chromosomal heterozygotes, by other kinds of selection against hybrids, and by selection adapting the chromosome races to different habitats. The structure of the contact may be caused by both random drift and by selection in relation to habitat.     

中华鳖太湖养殖种群和日本引进种群线粒体DNA Cyt b基因片段序列分析及分子进化初探

对中华鳖太湖养殖种群和日本引进种群共38个个体的线粒体DNA细胞色素b基因中间部分序列进行测定,比较其同源性,计算碱基组成,并用乌龟为外群构建不同单倍型的UPGMA和NJ分子系统树.在获得的408bp的序列中,A T约占58.8%,其中15个核苷酸位点存在变异(约占3.7%).两种群共有6种单倍型(haplotype),其中太湖养殖种群有4种单倍型,日本引进种群有2种单倍型.由系统树显示,中华鳖太湖种群的4种单倍型聚合成一大支,日本引进种群的2种单倍型以很高的置信度(99%)聚成一支.两种群序列上的差异,可以成为种群鉴别的分子标记.     

四种犬科（Canidae）动物线粒体DNA分子进化

以９种限制性内切酶分析家犬,狼,赤狐,貉共７只动物的一粒体ＤＮＡ限制性片段长度多态性（ｍｔＤＮＡＲＦＬＰ）,通过双酶解法构建各种动物的限制性内切酶图谱,用ＵＰＧ法,ＮＪ法和简略法分析这些动物之间的遗传关系。结果表明,１．犬的个体差异小,而赤弧的个体间遗传分化程度非常高;２．犬和狼的亲缘关系很近,应是同一种动物;３．在属间关系中,犬属与狐属的关系较接近,貉属是一个较早分化的独立分支。     

有关节肢动物系统发育若干问题的研究进展

近年来对节肢动物系统发育问题的认识有了相当大的变化,尤其是支序分析研究方法的使用,以及来自分子系统学和分子发育生物学的证据,成为继比较形态学之后有力的研究手段,近年来的研究显示线虫,缓步类和有爪类是节肢动物的近缘类群,而非以前绝大多数学者所认为的软体动物的环节动物,对于节肢动物门的单系性及其内部类群间关系的问题,目前倾向于认为（1）节肢动物为单系群;（2）由甲壳类,六足类和多足类联合形成单系群－具颚类;（3）与六足类分子系统学两方面研究的支持;对第3点的争议虽较大,但就论据而言确为优势观点。     

鲤亚科鱼类的系统发育

鲤亚科是由原始的鲃亚科派生的一个单源群,因此,把鲤亚科各属筛选出的性状与纪亚科的相应性状比较,以确定其性质,即该性状为祖征,还是为离征。经比较,发现25项性状在鲤亚科的5个属中呈镶嵌分布。根据性状的镶嵌分布情况和简约性原则,推导出鲤亚科的属间系统发育分支图。以往的观点认为,鲃鲤属与原鲤属的关系较近。现在系统发育关系分析的结果与此全然不同,原鲤属与鲤属的关系较近,而纪鲤属在鲤亚科内是较早分化出的一支,与亚科内其他4个属的关系相对较远。最后,依化石资料分析了鲤亚科的分化时间。     

朱雀类和朱鹀的分子系统发生分析

基于细胞色素b基因对13种朱雀Carpodacus spp.进行了系统发育分析,并结合核基因对单型属朱鹀属Urocynchramus的系统分类地位做了进一步探讨.研究发现朱雀属为一多系群,其中Carpodacus nipalensis和Leucosticte tephrocotis较朱雀属的其它成员有更近的亲缘关系.本文研究结果还进一步支持了朱鹀应该独立成为一个科的观点.