Phylogeny of Osmundaceae Inferred from rbcL Nucleotide Sequences and Comparison to the Fossil Evidences

rbcL sequences of 11 of 15 extant species of Osmundaceae which represent all three genera, Osmunda, Todea and Leptopteris. Our phylogenetic analysis concluded: 1) Osmunda subg. Osmunda and subg. Plenasium are monophyletic groups, but subg. Osmundastrum is not. The genus Osmunda is not monophyletic because Todea and Leptopteris are positioned within Osmunda. 2) Osmunda cinnamomea is the most basally positioned species in Osmundaceae, and it can be called as “a living fossil” because a fossil species (O. claytoniites) with almost the same morphology as this species was recorded from the Triassic. 3) Osmunda japonica and O. regalis are very closely related with only one nucleotide difference in the rbcL gene. 4) Greater nucleotide variation (5–7 nucleotides) was found between conspecific samples of O. cinnamomea and O. claytoniana collected from Japan and United States. Each of these two species may comprise more than two biologically differentiated species. Received 7 July 1999/ Accepted in revised form 25 August 1999     

Phylogeny of Chaetanthera (Asteraceae: Mutisieae) reveals both ancient and recent origins of the high elevation lineages

Penalized likelihood analysis of previously published chloroplast DNA (cpDNA) ndhF sequences suggests that the central-southern Andean genus Chaetanthera diverged ca. 16.5 million years (my) ago, well before the uplift of the Andes to their present heights. Penalized likelihood analysis based on new nuclear ribosomal DNA (rDNA) internal transcribed spacer (ITS) sequences indicates that the most relictual lineages occupy high elevation Andean habitats that did not exist until some 10my later. This result is contrary to the expectation that younger habitats should be occupied by phylogenetically younger lineages. The results are interpreted with respect to the development of aridity in lowland habitats during the Miocene and Pliocene, which presumably extinguished the lowland relatives of the high elevation taxa or, in effect, forced them upwards in search of adequate moisture. As the more northerly lineages were being displaced upward, others diversified in the mediterranean-type climate area of central Chile, giving rise to additional high elevation taxa again, at an early date, as well as lowland taxa. Some species of Chaetanthera from lowland central Chile appear as the phylogenetically youngest taxa, suggesting secondary adaptation to lowland aridity. At the same time, at least two high elevation species, Chaetanthera peruviana and Chaetanthera perpusilla, appear to have been derived recently from a lower elevation ancestor, while some middle to low elevation taxa seem to have evolved recently out of a high elevation complex. The results suggest that the younger high elevation habitats have served as both "cradle" and "museum" for Chaetanthera lineages.     

The Relationship Between the Rate of Molecular Evolution and the Rate of Genome Rearrangement in Animal Mitochondrial Genomes

Evolution of mitochondrial genes is far from clock-like. The substitution rate varies considerably between species, and there are many species that have a significantly increased rate with respect to their close relatives. There is also considerable variation among species in the rate of gene order rearrangement. Using a set of 55 complete arthropod mitochondrial genomes, we estimate the evolutionary distance from the common ancestor to each species using protein sequences, tRNA sequences, and breakpoint distances (a measure of the degree of genome rearrangement). All these distance measures are correlated. We use relative rate tests to compare pairs of related species in several animal phyla. In the majority of cases, the species with the more highly rearranged genome also has a significantly higher rate of sequence evolution. Species with higher amino acid substitution rates in mitochondria also have more variable amino acid composition in response to mutation pressure. We discuss the possible causes of variation in rates of sequence evolution and gene rearrangement among species and the possible reasons for the observed correlation between the two rates. [Reviewing Editor: Dr. David Pollock]     

中国柽柳属和水柏枝属的分子系统学研究

对中国柽柳科 3属 2 1种植物的核糖体DNA中的内转录间隔区 (ITS)序列及 5 8SrRNA基因的 3′端序列进行测定。结果表明 ,ITS - 1片段的长度范围在 2 5 4bp～ 2 6 9bp之间 ,ITS - 2片段的长度范围在 2 2 5bp～ 2 5 3bp之间。以Reaumuriasongarica作为功能性外类群 ,运用PAUP软件分析仅得到一个最简约树。简约树步长为 4 6 6步 ,一致性指数CI =0 85 84 ,保持性指数RI=0 86 2 2。系统发育分析表明 :秀丽水柏枝不应从水柏枝属中分出。另外 ,研究分析为目前分类上存有争议的白花柽柳、短毛柽柳及甘蒙柽柳的划分提供了分子生物学证据     

Phylogeny and Rates of Molecular Evolution of Planktonic Foraminifera: SSU rDNA Sequences Compared to the Fossil Record

Planktonic foraminifera are marine protists, whose calcareous shells form oceanic sediments and are widely used for stratigraphic and paleoenvironmental analyses. The fossil record of planktonic foraminifera is compared here to their molecular phylogeny inferred from ribosomal DNA sequences. Eighteen partial SSU rDNA sequences from species representing all modern planktonic families (Globigerinidae, Hastigerinidae, Globorotaliidae, Candeinidae) were obtained and compared to seven sequences representing the major groups of benthic foraminifera. The phylogenetic analyses indicate a polyphyletic origin for the planktonic foraminifera. The Candeinidae, the Globorotaliidae, and the clade Globigerinidae + Hastigerinidae seem to have originated independently, at different epochs in the evolution of foraminifera. Inference of their relationships, however, is limited by substitution rates of heterogeneity. Rates of SSU rDNA evolution vary from 4.0 × 10⁻⁹ substitutions/site/year in the Globigerinidae to less than 1.0 × 10⁻⁹ substitutions/site/year in the Globorotaliidae. These variations may be related to different levels of adaptation to the planktonic mode of life. A clock-like evolution is observed among the Globigerinidae, for which molecular and paleontological data are congruent. Phylogeny of the Globorotaliidae is clearly biased by rapid rates of substitution in two species (G. truncatulinoides and G. menardii). Our study reveals differences in absolute rates of evolution at all taxonomic levels in planktonic foraminifera and demonstrates their effect on phylogenetic reconstructions. Received: 21 January 1997 / Accepted: 17 April 1997     

The oldest lamprophiid (Serpentes,Caenophidia) fossil from the late Oligocene Rukwa Rift Basin,Tanzania and the origins of African snake diversity

Extant snake faunas have their origins in the mid-Cenozoic, when colubroids replaced booid-grade snakes as the dominant species. The timing of this faunal changeover in North America and Europe based on fossils is thought to have occurred in the early Neogene, after a period of global cooling opened environments and made them suitable for more active predators. However, new fossils from the late Oligocene of Tanzania have revealed an early colubroid-dominated fauna in Africa suggesting a different pattern of faunal turnover there. Additionally, molecular divergence times suggest colubroid diversification began sometime in the Paleogene, although the exact timing and driving forces behind the diversification are not clear. Here we present the first fossil snake referred to the African clade Lamprophiinae, and the oldest fossil known of Lamprophiidae. As such, this specimen provides the only potential fossil calibration point for the African snake radiation represented by Lamprophiidae, and is the oldest snake referred to Elapoidea. A molecular clock analysis using this and other previously reported fossils as calibration points reveals colubroid diversification minimally occurred in the earliest Paleogene, although a Cretaceous origin cannot be excluded. The elapoid and colubrid lineages diverged during the period of global warming near the Paleocene-Eocene boundary, with both clades diversifying beginning in the early Eocene (proximate to the Early Eocene Climate Optimum) and continuing into the cooler Miocene. The majority of subclades diverge well before the appearance of colubroid dominance in the fossil record. These results suggest an earlier diversification of colubroids than generally previously thought, with hypothesized origins of these clades in Asia and Africa where the fossil record is relatively poorly known. Further work in these regions may provide new insights into the timing of, and environmental influences contributing to, the rise of colubroid snakes.     

Estimation of adult stature from the calcaneus and talus

Calcanei and tali of 100 skeletons in the Hamann–Todd Collection at the Cleveland Museum of Natural History were measured. The skeletons represented 50 males and 50 females distributed equally by race, i.e., whites and blacks. Linear-regression equations, with standard errors ranging from 4.09 to 6.11 cm, were derived from these measurements for the purpose of estimating stature. Two independent control samples, including one comprised of remains of American servicemen lost in World War II and the Korea and Vietnam wars, were tested with relatively accurate results. © 1995 Wiley-Liss, Inc.     

The Effects of Social Structure, Geographical Structure, and Population Size on the Evolution of Mitochondrial DNA: II. Molecular Clocks and the Lineage Sorting Period

Evolutionary geneticists have increasingly used sequence variation in mitochondrial DNA (mtDNA) as a source of historical information. However, conclusions based on these data remain tentative because a sufficiently clear understanding of the evolutionary dynamics of mtDNA has yet to be developed. In this paper we present the results of computer simulations designed to illustrate the effects of social structure, geographical structure, and population size on the rate of nucleotide substitution and lineage sorting of mtDNA. The model is based in part on the social structure of macaque monkeys. Simulated populations of females were divided into 25 social groups; the animals in each were distributed in a hierarchy of four dominance rank categories. The probabilities for offspring survivorship were varied among dominance ranks to reflect the fitness consequences of social structure. Population size was varied across runs from 100 to 300 females. The pattern of female migration was also varied to mimic either the island model or the stepping-stone model. All these variables are shown to affect the lineage sorting period (LSP), and certain combinations of parameter values can cause the retention of mtDNA polymorphisms for a very long time. In addition, the simulations exhibited a negative relationship between the LSP and substitution rate over a modest and realistic range of LSP values. An important implication of these results is that estimates of time since isolation based on the assumption of a constant molecular clock may be biased and unreliable.     

Fossil lizard from central Europe resolves the origin of large body size and herbivory in giant Canary Island lacertids

The endemic Canary Island lizard clade Gallotia, which includes the largest members of Europe's dominant reptile group, Lacertidae, is one of the classic examples of insular gigantism. For the first time we use fossil data to test the evolutionary reasons for the association between gigantism and herbivory. We describe an almost completely preserved skeleton of J anosikia ulmensis comb. nov. from the early Miocene of Ulm, Germany (MN 2a, ～ 22 Mya). We show that this species and Oligocene Pseudeumeces cadurcensis (Filhol, 1877) are in fact crown lacertids, and the first known pre‐Quaternary record of the total clade of Gallotia. Pseudeumeces confirms the early origin of crown Lacertidae in the Palaeogene of Europe. More importantly, these fossil taxa show that large body size was already achieved on the European mainland by the early Miocene. Furthermore, Pseudeumeces and Janosikia were faunivorous, thus demonstrating that insularity, not large body size, was crucial to the evolution of herbivory in this lineage. Body size change in Gallotia was more complex than previously thought, encompassing size increase [e.g. in the extinct Gallotia goliath (Mertens, 1942)], but more commonly involving miniaturization. The physical environment may play a crucial role in modulating the evolution of body size in this natural laboratory.     

Molecular Phylogeny of the Chipmunks Inferred from Mitochondrial Cytochrome b and Cytochrome Oxidase II Gene Sequences

There are currently 25 recognized species of the chipmunk genus Tamias. In this study we sequenced the complete mitochondrial cytochrome b (cyt b) gene of 23 Tamias species. We analyzed the cyt b sequence and then analyzed a combined data set of cyt b along with a previous data set of cytochrome oxidase subunit II (COII) sequence. Maximum-likelihood was used to further test the fit of models of evolution to the cyt b data. Other sciurid cyt b sequence was added to examine the evolution of Tamias in the context of other sciurids. Relationships among Tamias species are discussed, particularly the possibility of a current sorting event among taxa of the southwestern United States and the extreme divergences among the three subgenera (Neotamias, Eutamias, and Tamias).     

Molecular identification of predation by carabid beetles on exotic and native slugs in a strawberry agroecosystem

Generalist predators have the capacity to exert significant pressure on prey populations. However, integrating them into biological control programs relies on a detailed understanding of their foraging behavior and the levels of trophic connectedness with pest species. Carabid beetles are important predators of slugs, pests of agricultural, floricultural and horticultural crops worldwide, but these interactions have been rarely studied outside the Western Palearctic ecozone. Diagnostic molecular gut-content analysis was used to examine the strength of trophic pathways between a community of carabid beetles and two slug species, the exotic Deroceras reticulatum and native Deroceras laeve, in strawberry agroecosystems. Strawberries were grown according to standard horticultural practices for central Kentucky, following traditional bare ground planting or with the addition of detrital subsidies, to quantify the impact of habitat management on the abundance of pests and the strength of these trophic pathways. Following laboratory characterization of species-specific molecular markers targeting both Deroceras species, carabid beetles collected from a strawberry agroecosystem were screened for slug DNA. Field collections revealed important food web pathways existed between Harpalus pensylvanicus and D. reticulatum, with 7.2% screening positive for these prey yet none screening positive for D. laeve. In contrast, Chlaenius tricolor was found to feed on both slug species in the field, with 16% screening positive for both Deroceras. Despite below normal rainfall limiting slug densities in the field, the results presented here reveal the potential importance of carabid beetles in slug population dynamics in the Nearctic.     

Molecular development of fibular reduction in birds and its evolution from dinosaurs

Birds have a distally reduced, splinter‐like fibula that is shorter than the tibia. In embryonic development, both skeletal elements start out with similar lengths. We examined molecular markers of cartilage differentiation in chicken embryos. We found that the distal end of the fibula expresses Indian hedgehog (IHH), undergoing terminal cartilage differentiation, and almost no Parathyroid‐related protein (PTHrP), which is required to develop a proliferative growth plate (epiphysis). Reduction of the distal fibula may be influenced earlier by its close contact with the nearby fibulare, which strongly expresses PTHrP. The epiphysis‐like fibulare however then separates from the fibula, which fails to maintain a distal growth plate, and fibular reduction ensues. Experimental downregulation of IHH signaling at a postmorphogenetic stage led to a tibia and fibula of equal length: The fibula is longer than in controls and fused to the fibulare, whereas the tibia is shorter and bent. We propose that the presence of a distal fibular epiphysis may constrain greater growth in the tibia. Accordingly, many Mesozoic birds show a fibula that has lost its distal epiphysis, but remains almost as long as the tibia, suggesting that loss of the fibulare preceded and allowed subsequent evolution of great fibulo–tibial disparity.     

Electrogenic Glutamate Transporters in the CNS: Molecular Mechanism,Pre-steady-state Kinetics,and their Impact on Synaptic Signaling

Glutamate is the major excitatory neurotransmitter in the mammalian CNS. The spatiotemporal profile of the glutamate concentration in the synapse is critical for excitatory synaptic signalling. The control of this spatiotemporal concentration profile requires the presence of large numbers of synaptically localized glutamate transporters that remove pre-synaptically released glutamate by uptake into neurons and adjacent glia cells. These glutamate transporters are electrogenic and utilize energy stored in the transmembrane potential and the Na⁺/K⁺-ion concentration gradients to accumulate glutamate in the cell. This review focuses on the kinetic and electrogenic properties of glutamate transporters, as well as on the molecular mechanism of transport. Recent results are discussed that demonstrate the multistep nature of the transporter reaction cycle. Results from pre-steady-state kinetic experiments suggest that at least four of the individual transporter reaction steps are electrogenic, including reactions associated with the glutamate-dependent transporter halfcycle. Furthermore, the kinetic similarities and differences between some of the glutamate transporter subtypes and splice variants are discussed. A molecular mechanism of glutamate transport is presented that accounts for most of the available kinetic data. Finally, we discuss how synaptic glutamate transporters impact on glutamate receptor activity and how transporters may shape excitatory synaptic transmission.     

家蚕滞育生物钟蛋白质Ease A4的纯化及其分子结构分析

ＥａｓｅＡ４是家蚕卵的一种滞育生物钟蛋白质．产下后２ｄ的家蚕Ｃ１０８品种滞育性卵,经过丙酮脱脂、８５℃热处理、硫酸铵沉淀和ＳｅｐｈａｄｅｘＧ－２５凝胶过滤层析初步分离,进一步经过Ｓｅｐ－ＰａｋＣ１８脱盐浓缩,ＨＰＬＣ（柱为ＹＭＣ－ＰａｃｋＰｒｏｔｅｉｎ－ＲＰ）分离,通过ＳＤＳ－ＰＡＧＥ和ＭＡＬＤＩＭＳ方法鉴定,纯化得到ＥａｓｅＡ４蛋白质．从１０ｇ蚕卵最终得到了１１．８μｇＥａｓｅＡ４．ＥａｓｅＡ４由从Ｈｉｓ到Ｔｙｒ的１５５个氨基酸残基构成,蛋白质部分的分子量为１６６０１．其２２位氨基酸残基Ａｓｎ处有一个Ａｓｎ－Ｘ－Ｔｈｒ糖基化场所,并有糖基结合在该部位,糖基的分子量约为７６０．ＥａｓｅＡ４的６１位和１５０位的两个Ｃｙｓ氨基酸残基之间存在二硫键．糖基和二硫键的存在不仅有利于酶蛋白的分离,还可能与酶活性有关     

Correlations between leaf constituent levels and the densities of herbivorous insect guilds in an Australian forest

Abstract Significant correlations were found between herbivorous insect densities and leaf constituent levels across 18 species of understorey shrub in an Australian forest. In general, insect densities were positively correlated with nitrogen and water and negatively correlated with fibre and its constituents (cellulose and lignin), but not all insect guilds were significantly correlated with all leaf constituents. When mature leaf traits were considered, total herbivore density among plant species was most strongly correlated with levels of nitrogen and water. However, when insects were divided into functional guilds, only densities of sucking insects were significantly correlated with mature leaf nitrogen and water, whereas chewing insect densities were significantly correlated with mature leaf fibre and lignin. Low leaf nitrogen levels were recorded for all plants surveyed (among the lowest reported for woody angiosperms), and many plant species also had high levels of leaf fibre. These features are characteristic of Australian forests and have been linked to the generally nutrient‐poor soils of this continent. Levels of new leaf nitrogen (% fresh weight) were generally less than or equal to levels of mature leaf nitrogen (% fresh weight). Hence the new leaf preference of several herbivore guilds could not be explained by higher levels of leaf nitrogen. However, significant negative correlations were found between chewer densities and levels of leaf fibre, cellulose and lignin for new and mature leaves, suggesting that higher levels of fibre, cellulose and lignin in mature leaves may be contributing more strongly to the new leaf preference of chewers than leaf nitrogen levels. Despite the significant correlations between leaf constituent levels and the densities of individual guilds, multivariate analyses found no significant relationship between leaf constituent levels and the taxonomic or guild composition of herbivorous insect assemblages.