了哥王叶的结构特征及生态意义

运用冷冻切片技术,用光学显微镜对了哥王(Wikstroemia indica(L.)C.A.Mey.)叶的解剖结构进行了观察研究.结果表明,了哥王叶表现出许多旱生、阳生形态,兼具有中生特点.叶表皮由一层排列紧密形状不规则的细胞组成,细胞外壁角质膜较厚;上下表皮均无毛;气孔类型为无规则型,仅分布在下表皮且下陷,气孔密度较...     

DIVERGENCE IS FOCUSED ON FEW GENOMIC REGIONS EARLY IN SPECIATION: INCIPIENT SPECIATION OF SUNFLOWER ECOTYPES

Early in speciation, as populations undergo the transition from local adaptation to incipient species, is when a number of transient, but potentially important, processes appear to be most easily detected. These include signatures of selective sweeps that can point to asymmetry in selection between habitats, divergence hitchhiking, and associations of adaptive genes with environments. In a genomic comparison of ecotypes of the prairie sunflower, Helianthus petiolaris, occurring at Great Sand Dunes National Park and Preserve (Colorado), we found that selective sweeps were mainly restricted to the dune ecotype and that there was variation across the genome in whether proximity to the nondune population constrained or promoted divergence. The major regions of divergence were few and large between ecotypes, in contrast with an interspecific comparison between H. petiolaris and a sympatric congener, Helianthus annuus. In general, the large regions of divergence observed in the ecotypic comparison swamped locus‐specific associations with environmental variables. In both comparisons, regions of high divergence occurred in portions of the genetic map with high marker density, probably reflecting regions of low recombination. The difference in genomic distributions of highly divergent regions between ecotypic and interspecific comparisons highlights the value of studies spanning the spectrum of speciation in related taxa.     

ADAPTIVE DIVERGENCE IN DARWIN'S RACE: HOW COEVOLUTION CAN GENERATE TRAIT DIVERSITY IN A POLLINATION SYSTEM

Understanding how reciprocal selection shapes interacting species in Darwin's coevolutionary race is a captivating pursuit in evolutionary ecology. Coevolving traits can potentially display following three patterns: (1) geographical variation in matched traits, (2) bias in trait matching, and (3) bimodal distribution of a trait in certain populations. Based on the framework of adaptive dynamics, we present an evolutionary model for a coevolving pollination system involving the long‐proboscid fly (Moegistorhynchus longirostris) and the long‐tubed iris (Lapeirousia anceps). The model successfully demonstrates that Darwin's hypothesis can lead to all three patterns if costs are involved. Geographical variation in matched traits could be driven by geographical variation in environmental factors that affect the cost rate of trait escalation. Unequal benefits derived from the interaction by the fly and the flower could potentially cause the bias in trait matching of the system. Different cost rates to trait elongation incurred by the two species and weak assortative interactions in the coevolutionary race can drive divergent selection (i.e., an evolutionary branching) that leads to the bimodal distribution of traits. Overall, the model highlights the importance of assortative interactions and the balance of costs incurred by coevolving species as factors determining the eventual phenotypic outcome of coevolutionary interactions.     

THE OPPORTUNITY FOR BALANCING SELECTION IN EXPERIMENTAL POPULATIONS OF CAENORHABDITIS ELEGANS

The role of balancing selection in maintaining diversity during the evolution of sexual populations to novel environments is poorly understood. To address this issue, we studied the impact of two mating systems, androdioecy and dioecy, on genotype distributions during the experimental evolution of Caenorhabditis elegans. We analyzed the temporal trajectories of 334 single nucleotide polymorphisms, covering 1/3 of the genome, and found extensive allele frequency changes and little loss of heterozygosities after 100 generations. As modeled with numerical simulations, SNP differentiation was consistent with genetic drift and average fitness effects of 2%, assuming that selection acted independently at each locus. Remarkably, inbreeding by self‐fertilization was of little consequence to SNP differentiation. Modeling selection on deleterious recessive alleles suggests that the initial evolutionary dynamics can be explained by associative overdominance, but not the later stages because much lower heterozygosities would be maintained during experimental evolution. By contrast, models with selection on true overdominant loci can explain the heterozygote excess observed at all periods, particularly when negative epistasis or independent fitness effects were considered. Overall, these findings indicate that selection at single loci, including purging of recessive alleles, underlies most of the genetic differentiation accomplished during the experiment. Nonetheless, they also imply that maintenance of genetic diversity may in large part be due to balancing selection at multiple loci.     

Ecological and phylogenetic dimensions of cranial shape diversification in South American caviomorph rodents (Rodentia: Hystricomorpha)

Caviomorph rodents represent an excellent model to explore morphological diversification on a macroevolutionary scale, as they are ecologically and morphologically diverse. We analysed cranial shape variation using geometric morphometrics and phylogenetic comparative methods. Most variation involved the shape of the rostrum, basicranium, and cranial vault, and clearly matched the phylogenetic structure. At the same time, a strong allometric pattern was associated with the length of the rostrum and cranial vault, size of the auditory bulla, and depth of the zygomatic arch. After accounting for size influence, and taking phylogenetic structure into account, shape variation was significantly associated with habitat. Our results highlight the presence of complex relationships between morphological, phylogenetic, and ecological dimensions in the diversification of the caviomorph cranium. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 898–913.     

Phylogeography of willow grouse (Lagopus lagopus) in the Arctic: taxonomic discordance as inferred from molecular data

Using independently segregating nuclear single nucleotide polymorphisms (SNPs) and mitochondrial control region sequences, we found an east–west division among sampled willow grouse Lagopus lagopus subspecies. This division cut across the range of the subspecies with the largest distribution (lagopus) and thus contradicted existing taxonomic classifications. Russian Lagopus lagopus lagopus tended to cluster with North American willow grouse partly classified as other subspecies. Scandinavian willow grouse (L. l. lagopus) clustered with red grouse from Britain and Ireland (Lagopus lagopus scoticus and Lagopus lagopus hibernicus) but substructuring confirmed the monophyly of the latter. In North America, we could not detect any major genetic divisions apart from two birds described as alexandrae from the Heceta Island (Alaska) when using mitochondrial sequences. Other samples from North America were intermingled regardless of whether they were described as muriei, alexandrae or lagopus. A specimen described as alexandrae was to some extent distinct when analysing the SNP data. The genetic analyses indicated some concordance between genetics and taxonomy but not complete congruence. This is particularly evident for mitochondrial DNA network analyses. We suggest that the taxonomy of this species would benefit by a careful re‐examination of the available evidence for subspecies. It appears as if subspecies status is a poor proxy for assigning evolutionary significant units and management units in this species. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 77–90.     

A parallel study of different array-CGH platforms in a set of Spanish patients with developmental delay and intellectual disability

Developmental delay and intellectual disability, which occur in 1–3% of the population, account for a large number of the cases regularly seen in genetic units. Chromosomal microarray analysis has been shown to be a valuable clinical diagnostic assay and it should be the first-tier clinical diagnostic test for individuals with these conditions. However and due to several difficulties such as the platform resolution, the cost, and the inexperience with genomic data bases, the implementation of this test in many cytogenetic laboratories has been delayed. In an attempt to provide more insights of the benefits derived by using the chromosomal microarray analysis, this study presents the experience of two clinical centers using three different microarray platforms. The results obtained using a custom microarray (KaryoArray®) and two different commercial medium- and high-resolution whole-genome oligonucleotide microarrays have been compared. An overall diagnostic yield of around 15% has been obtained. However, the custom microarray platform has been shown to be more convenient for a clinical setting, since it allows the detection of more pathogenic copy number variants and less common variants.     

Comparative genome sequence analysis of Sulfolobus acidocaldarius and 9 other isolates of its genus for factors influencing codon and amino acid usage

In the present study, major constraints for codon and amino acid usage of Sulfolobus acidocaldarius, Sulfolobus solfataricus, Sulfolobus tokodali, Sulfolobus islandis and 6 other isolates from islandicus species of genus Sulfolobus were investigated. Correspondence analysis revealed high significant correlation between the major trend of synonymous codon usage and gene expression level, as assessed by the “Codon Adaptation Index” (CAI). There is a significant negative correlation between Nc (Effective number of codons) and CAI demonstrating role of codon bias as an important determinant of codon usage. The significant correlation between major trend of synonymous codon usage and GC3s (G + C at third synonymous position) indicated dominant role of mutational bias in codon usage pattern. The result was further supported from SCUO (synonymous codon usage order) analysis. The amino acid usage was found to be significantly influenced by aromaticity and hydrophobicity of proteins. However, translational selection which causes a preference for codons that are most rapidly translated by current tRNA with multiple copy numbers was not found to be highly dominating for all studied isolates. Notably, 26 codons that were found to be optimally used by genes of S. acidocaldarius at higher expression level and its comparative analysis with 9 other isolates may provide some useful clues for further in vivo genetic studies on this genus.     

Biochronology of the first hominid remains in Europe using the vole Mimomys savini: Fuente Nueva 3 and Barranco León D,Guadix-Baza Basin,south-eastern Spain

The sites of Barranco León D (BL-D) and Fuente Nueva 3 (FN-3) in the Guadix-Baza Basin (Granada, Spain), together with the site of Sima del Elefante in the Sierra de Atapuerca (Burgos, Spain), constitute one of the oldest records of the earliest hominid population in the European continent west of Dmanisi (Georgia, Lesser Caucasus). In the Guadix-Baza Basin, evidence of human occupation has been found to date in the form of lithic industry (Mode 1) and cut marks in large-mammal fossil remains (mainly of hippopotamuses and elephants), and recently a human tooth considered as the oldest in Europe has been discovered. Although in the case of Sima del Elefante there is unanimity among the scientific community regarding the chronology of the unit in which the hominid remains were found (Unit TE9c, 1.22 Ma), there is continuing debate on the chronology of the sites of the Guadix-Baza Basin (FN-3 and BL-D). This applies especially to BL-D, as the numerical datings published for this site have a very high error range (1.4 ± 0.38 Ma). In this paper, the chronology of these two sites is determined using as a marker the morphological and morphometric changes undergone by Mimomys savini in its first lower molar (m1) over the course of its evolutionary history. It has been possible to confirm that the oldest human presence in the Guadix-Baza Basin and at Sima del Elefante (Atapuerca) share a similar chronology, dated to between 1.1 and 1.4 Ma. Apparently, the oldest site with human remains in Europe is seen to be BL-D, dated to 1.26 ± 0.13 Ma, followed by Level TE9c, dated to 1.22 ± 0.16 Ma, and FN-3, dated to 1.20 ± 0.12 Ma.