Evolutionary and morphological significance of the deflecting wrinkle in the lower molars of the Hominoidea

The deflecting wrinkle is a well-known character state of the lower m2 and M1 of the human dentition, but there is little information regarding its presence in great apes. The deflecting wrinkle is more frequent on M2-3 in all extant pongid genera studied in this paper except Pan paniscus, in which M1 has the highest frequency (16.0%) and in which this wrinkle is absent on M3. In Gorilla, it is absent on M1, with only a low incidence on M2-3. Its greatest frequency in Pongo is always on M2 (20.2%), which is the greatest expression of the trait in the great apes. We interpret the presence of the deflecting wrinkle as an incidental effect and suggest that it represents a plesiomorphic character state in the Hominoidea.     

Mitochondrial complementation: a possible neglected factor behind early eukaryotic sex

Sex is ancestral in eukaryotes. Meiotic sex differs from bacterial ways of exchanging genetic material by involving the fusion of two cells. We examine the hypothesis that fusion evolved in early eukaryotes because it was directly beneficial, rather than a passive side effect of meiotic sex. We assume that the uptake of (proto)mitochondria into eukaryotes preceded the evolution of cell fusion and that Muller's ratchet operating within symbiont lineages led to the accumulation of lineage‐specific sets of mutations in asexual host cells. We examine whether cell fusion, and the consequent biparental inheritance of symbionts, helps to mitigate the effects of this mutational meltdown of mitochondria. In our model, host cell fitness improves when two independently evolved mitochondrial strains co‐inhabit a single cytoplasm, mirroring mitochondrial complementation found in modern eukaryotes. If fusion incurs no cost, we find that an allele coding for fusion can invade a population of nonfusers. If fusion is costly, there are two thresholds. The first describes a maximal fusing rate (probability of fusion per round of cell division) that is able to fix. An allele that codes for a rate above this threshold can reach a polymorphic equilibrium with nonfusers, as long as the rate is below the second threshold, above which the fusion allele is counter‐selected. Whenever it evolves, fusion increases the population‐wide level of heteroplasmy, which allows mitochondrial complementation and increases population fitness. We conclude that beneficial interactions between mitochondria are a potential factor that selected for cell fusion in early eukaryotes.     

The cancellation effect at the group level

Group selection models combine selection pressure at the individual level with selection pressure at the group level. Cooperation can be costly for individuals, but beneficial for the group, and therefore, if individuals are sufficiently much assorted, and cooperators find themselves in groups with disproportionately many other cooperators, cooperation can evolve. The existing literature on group selection generally assumes that competition between groups takes place in a well-mixed population of groups, where any group competes with any other group equally intensely. Competition between groups however might very well occur locally; groups may compete more intensely with nearby than with far-away groups. We show that if competition between groups is indeed local, then the evolution of cooperation can be hindered significantly by the fact that groups with many cooperators will mostly compete against neighboring groups that are also highly cooperative, and therefore harder to outcompete. The existing empirical method for determining how conducive a group structured population is to the evolution of cooperation also implicitly assumes global between-group competition, and therefore gives (possibly very) biased estimates.     

The effect of domestication on some life history traits of sea trout and Atlantic salmon

During the period 1968–1991, certain morphological traits of Atlantic salmon Salmo salar and sea trout S. trutta have been recorded regularly at the hatchery at Älvkarleby, central Sweden. Total body length, weight (for females both before and after stripping), number of eggs, egg size and date of ovulation. A smaller data set for fish marked and released as smolts, providing information about total body length of released smolts, time spent at sea and body size of the recovered adults, was also available for analysis. According to theory and empirical data, the process of artificial breeding results in an evolutionary divergence of the cultured strain from the wild phenotypic norm. The reason for such a divergence is that both natural and sexual selection pressures are altered or relaxed during the process of artificial breeding, as well as random genetic processes, such as founder effects and in- and outbreeding. A path analysis of both species and sexes revealed that the size of the released smolts had increased during the study period. Time spent in sea has decreased for both female and male sea trout, but not for Atlantic salmon. Adult body size for female and male trout have increased as well as female trout condition factor. The increase found in egg size of both species was greater for the salmon than for the trout, indicating that female salmon invest more in egg size with increasing body size. These results support the view that domestication probably has a significant and selective impact on the life history traits of the two salmonid species studied.     

Mitochondrial Dehydrogenases in Different Taxa of Tetrahymena: Effect of Insulin

Mitochondrial dehydrogenase activity was measured in seven taxa of Tetrahymena (T. pyriformis G1, T. hegewishi, T. malaccensis, T. pigmentosa, T. shapiro, T. thermophila CU-399, T. thermophila MS-1). Enzyme activity was different in the taxa investigated. Insulin reduced enzyme activity in six of the seven taxa studied. The duration of activity reduction was relatively long (5–10 min.) in most of the cases, and in T. hegewishi this lasted up to the end of the measurements (30 min.). There was no interrelation between the basic dehydrogenase activity of the taxon and the effect of insulin. There was also no correlation between the degree of relationship (of the taxa) and the dehydrogenase profile after insulin treatment.     

INTERSPECIFIC COMPETITION ALTERS NONLINEAR SELECTION ON OFFSPRING SIZE IN THE FIELD

Offspring size is one of the most important life‐history traits with consequences for both the ecology and evolution of most organisms. Surprisingly, formal estimates of selection on offspring size are rare, and the degree to which selection (particularly nonlinear selection) varies among environments remains poorly explored. We estimate linear and nonlinear selection on offspring size, module size, and senescence rate for a sessile marine invertebrate in the field under three different intensities of interspecific competition. The intensity of competition strongly modified the strength and form of selection acting on offspring size. We found evidence for differences in nonlinear selection across the three environments. Our results suggest that the fitness returns of a given offspring size depend simultaneously on their environmental context, and on the context of other offspring traits. Offspring size effects can be more pervasive with regards to their influence on the fitness returns of other traits than previously recognized, and we suggest that the evolution of offspring size cannot be understood in isolation from other traits. Overall, variability in the form and strength of selection on offspring size in nature may reduce the efficacy of selection on offspring size and maintain variation in this trait.     

Allometric constraints on stability and maximum size in flying fishes: implications for their evolution

Flying fish wing area and wing-loading both rise in strongly negative allometric fashion with increasing body length and mass. Evidence is presented to show that this occurs because: (1) the leading edge of the pectoral fin 'wing' is fixed at 24% of standard length (  L _S) from the snout, (2) the wing length cannot exceed 76% of L _S or the tips will interfere with propulsive tail beat and (3) increased mass demands faster flying and wings with better lift : drag ratios; this selects for tapered, higher aspect ratio wing shapes. A consequence of this situation is that larger flying fishes have centres of mass increasingly further behind the centre of wing pressure. Resultant longitudinal instability restricts the maximum size of the two-winged design and the pelvic fins of four-wingers act as a stabilizing tailplane. These data indicate that the accepted model of evolution of flight in flying fishes (by extension of ballistic leaps) is flawed; it is proposed that evolution of lift-supported surface taxiing in half-beaks with enlarged pectoral fins (enhanced by ground effect) was an essential preliminary; subsequent forward migration of the centre of mass to within the wing chord permitted effective gliding.     

RECURRENT AND RECENT SELECTIVE SWEEPS IN THE piRNA PATHWAY

Uncontrolled transposable element (TE) insertions and excisions can cause chromosome breaks and mutations with dramatic deleterious effects. The PIWI interacting RNA (piRNA) pathway functions as an adaptive TE silencing system during germline development. Several essential piRNA pathway proteins appear to be rapidly evolving, suggesting that TEs and the silencing machinery may be engaged in a classical “evolutionary arms race.” Using a variety of molecular evolutionary and population genetic approaches, we find that the piRNA pathway genes rhino, krimper, and aubergine show patterns suggestive of extensive recurrent positive selection across Drosophila species. We speculate that selection on these proteins reflects crucial roles in silencing unfamiliar elements during vertical and horizontal transmission of TEs into naïve populations and species, respectively.     

磷脂酰甘油对光系统Ⅱ放氧活性的影响

The dependence of oxygen evolution in PS Ⅱ from spinach Spinacia oleracea L. on the content of exogenous anionic phosphatidylglycerol (PG) at pH 6.0 was investigated through reconstitution experiment. It was found that there was a steady increase in oxygen evolution. With increasing PG/PS Ⅱ ratio up to a maximum at concentrations ranging from 10-22 mg PG/mg chlorophyll (Chl). Then, further addition of PG resulted in the inhibitions of oxygen evolution. With a PG/PS Ⅱ ratio of 40 mg PG/mg Chl, the oxygen-evolving activity of PS Ⅱ decreased to 40% of the untreated PS Ⅱ. It is suggested that a stimulation of oxygen evolution at a low PG/Chl ratio was resulted from the structural optimization of PS Ⅱ by PG while an inhibitory effect on oxygen evolution at higher values of this ratio was ascribed to the structural changes of extrinsic proteins of PS Ⅱ owing to osmotic pressure.     

Review. Studying cumulative cultural evolution in the laboratory

Cumulative cultural evolution is the term given to a particular kind of social learning, which allows for the accumulation of modifications over time, involving a ratchet-like effect where successful modifications are maintained until they can be improved upon. There has been great interest in the topic of cumulative cultural evolution from researchers from a wide variety of disciplines, but until recently there were no experimental studies of this phenomenon. Here, we describe our motivations for developing experimental methods for studying cumulative cultural evolution and review the results we have obtained using these techniques. The results that we describe have provided insights into understanding the outcomes of cultural processes at the population level. Our experiments show that cumulative cultural evolution can result in adaptive complexity in behaviour and can also produce convergence in behaviour. These findings lend support to ideas that some behaviours commonly attributed to natural selection and innate tendencies could in fact be shaped by cultural processes.     

Fitness consequences of maternal and grandmaternal effects

Transgenerational effects are broader than only parental relationships. Despite mounting evidence that multigenerational effects alter phenotypic and life‐history traits, our understanding of how they combine to determine fitness is not well developed because of the added complexity necessary to study them. Here, we derive a quantitative genetic model of adaptation to an extraordinary new environment by an additive genetic component, phenotypic plasticity, maternal and grandmaternal effects. We show how, at equilibrium, negative maternal and negative grandmaternal effects maximize expected population mean fitness. We define negative transgenerational effects as those that have a negative effect on trait expression in the subsequent generation, that is, they slow, or potentially reverse, the expected evolutionary dynamic. When maternal effects are positive, negative grandmaternal effects are preferred. As expected under Mendelian inheritance, the grandmaternal effects have a lower impact on fitness than the maternal effects, but this dual inheritance model predicts a more complex relationship between maternal and grandmaternal effects to constrain phenotypic variance and so maximize expected population mean fitness in the offspring.     

Evolutionary coupling between the deleteriousness of gene mutations and the amount of non-coding sequences

The phenotypic effects of random mutations depend on both the architecture of the genome and the gene-trait relationships. Both levels thus play a key role in the mutational variability of the phenotype, and hence in the long-term evolutionary success of the lineage. Here, by simulating the evolution of organisms with flexible genomes, we show that the need for an appropriate phenotypic variability induces a relationship between the deleteriousness of gene mutations and the quantity of non-coding sequences maintained in the genome. The more deleterious the gene mutations, the shorter the intergenic sequences. Indeed, in a shorter genome, fewer genes are affected by rearrangements (duplications, deletions, inversions, translocations) at each replication, which compensates for the higher impact of each gene mutation. This spontaneous adjustment of genome structure allows the organisms to retain the same average fitness loss per replication, despite the higher impact of single gene mutations. These results show how evolution can generate unexpected couplings between distinct organization levels.     

Origin and evolution of the Robertsonian populations of the house mouse (Rodentia, Muridae) in Tunisia based on allozyme studies

The central coastal region of Tunisia harbours two chromosomal races of the house mouse (2 n  = 22, 22Rb; 2 n  = 40, 40Std), which are genetically differentiated and show a high level of reproductive isolation. This study presents an allozyme analysis of house mice from the inland city of Kairouan 75 km from the coastal region. Results showed that the 22Rb and 40Std mice from Kairouan shared the same high degree of variability, and were not genetically differentiated. This contrasts with the genetic data registered for the two chromosomal races from the coastal towns, in which a particularly low genic diversity was observed in the 22Rb populations. As the two races in Kairouan show the same low hybridization rates as the populations in the coastal region, these results argue in favour of a local differentiation of the Rb race in Tunisia, most likely originating in Kairouan. The data further suggest that the decrease in variability observed in the coastal 22Rb populations is related to a founder effect or a bottleneck following the introduction of mice from Kairouan into one of these localities, prior to their dispersion throughout the coastal region.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 515–521.     

Microwave Quasi-Solid State to Construct Strong Metal-Support Interactions with Interfacial Electron-Enriched Ru for Anion Exchange Membrane Electrolysis

Regulating the metal-support interaction of the anchored metal nanoclusters is recognized as valid approach to optimize the electrocatalytic performance through tuning the interfacial electronic structure. However, developing novel support and understanding the interfacial electron accumulation on modulating the reaction kinetics are still elusive. Herein, highly-dispersed Ruthenium (Ru) nanoclusters anchored onto phosphorous doped molybdenum boride (Ru/P-MoB) is developed through ultrafast microwave-plasma (60 s) approach. The synthesized Ru/P-MoB impressively promote the hydrogen evolution with low overpotentials of 34, 45, and 40 mV to drive 10 mA cm⁻² in alkaline freshwater, alkaline seawater and acid media. Specially, it presents superior turnover frequency and mass/specific activity relative to Pt/C, Ru/C, and Ru/MoB. Moreover, the anion exchange membrane (AEM) electrolyzer cell based on Ru/P-MoB can achieve 500 and 1000 mA cm⁻² with small voltages of 1.71 and 1.78 V with good durability. Experimental and density functional theoretical (DFT) analysis reveal that the strong metal-support interactions (Ru─Mo and Ru─P bonds) with generated interfacial electron-enriched Ru, and then favoring the water-molecule adsorption/dissociation and optimal H intermediate adsorption free energy. This work provides novel designing avenue to exploit electrocatalysts with outstanding catalytic performance under high current density at practical high-temperature.     

基于遥感的城市绿色空间演化过程的温度效应研究——以福州主城区为例

以福州主城区绿色空间为研究对象,基于遥感手段,研究绿色空间的复杂演化对地表温度扰动的影响。研究发现:(1)1993—2016年,福州主城区下垫面绿色空间损失和扩张面积分别为46.50km²和4.73km²,面积差达到41.77km²。(2)不同温度区的分布格局发生了较大变化,冷岛区面积大幅减少,热岛区面积显著增加。从各温度等级内的土地利用分布来看,低温区内分布较多湿地和水体,次低温区以林/草地为主。(3)城市热岛重心与城市重心的迁移方向有关;而城市冷岛重心与城市绿色空间的分布关系密切。(4)不同绿色空间演化过程引起的降温效应大小依次为:绿色空间扩张>绿色空间不变>绿色空间交换>绿色空间损失。绿色空间扩张带来的平均降温幅度约为5.0℃,而绿色空间损失引起的平均增温约为7.0℃。不同的演化过程下,通过增加等面积的绿色空间,并不能抵消先前绿色空间损失带来的升温。因此,科学合理的绿色空间规划对于有效缓解城市热岛至关重要。     

赣西三市热环境时空演变特征及影响因素

以赣西三市为研究区域, 采用2002、2016年2个时段的TM/OLI/TIRS影像数据, 获得辐射亮度温度和土地利用/覆被分类数据, 借此分析热环境时空演变特征、热力景观格局指数变化以及影响热环境演变的因素, 旨在为改善赣西城市热环境问题提供科学的依据。结果表明: 随着城市化发展, 近15年(2002—2016年)来, 赣西三市热岛效应明显增强, 但不同区域发展程度有所不同, 热岛效应强度总体增加的趋势为: 萍乡 > 宜春 > 新余; 从热环境分布来看, 三市南部地区低温与次低温面积范围相对较多, 且呈现扩大趋势; 从热环境景观格局演变来看, 三市的中温区斑块优势度降低明显, 破碎化程度加强, 宜春和新余市区次低温与次高温斑块优势增多并且有形成大斑块的趋势; 从热环境贡献指数来看, 建设用地对热环境贡献最大, 水体和林地则对城市热岛效应有显著的抑制作用。     

Genetically idiosyncratic responses of Drosophila melanogaster populations to selection for improved learning ability

To what extent is adaptive evolution over short timescales repeatable? To address this question, we studied the performance of crosses between replicate Drosophila melanogaster lines previously subject to selection for improved learning response in the context of oviposition substrate choice. Of the 10 pairwise F₁ crosses among the five selection lines, four performed in the original learning assay similarly to the parental lines, whereas the remaining six showed learning scores significantly below the average of the parental lines. In particular, four F₁ crosses (three involving the same line) showed no detectable learning, on a par with unselected control lines. This indicates that the response to selection in some lines involved allelic substitutions at different loci. Additional assays of crosses between two selection lines indicated that the loss of performance in hybrids generalized to another type of learning assay, and held for both short‐ and long‐term memory. Joint analysis of first‐ and second‐generation crosses between these two lines supported the hypothesis that the response to selection in these different lines was based on the spread of recessive alleles at different loci. These results show that the evolutionary trajectories of populations of the same origin subject to uniform selection may sometimes diverge over very short evolutionary timescales.     

Using comparative genomic data to test for fast-X evolution

Genes may acquire nonsynonymous substitutions more rapidly when X-linked than when autosomal, but evidence for "fast-X evolution" has been elusive. Fast-X evolution could explain the disproportionate contribution of X-linked genes to hybrid sterility and other traits. Here, we use a comparative genomic approach, with sequences of 30-110 genes in four Drosophila species, to test for fast-X evolution. Specifically, the 3L autosome arm in D. melanogaster and D. simulans is homologous to the right arm of the X chromosome in D. pseudoobscura and D. miranda. We executed two paired comparisons to determine how often genes on this chromosome arm exhibit higher rates of nonsynonymous substitution in the D. pseudoobscura species group, as predicted by fast-X evolution. We found a statistically significant pattern consistent with fast-X evolution in one comparison and a similar trend in the other comparison. Variation in functional constraints across genes may have masked the signature of fast-X evolution in some previous studies, and we conclude paired comparisons are more powerful for examining rates of evolution of genes when X-linked over autosomal.     

Experimental models for testing hypotheses about cumulative cultural evolution

The rapid appearance (over evolutionary time) of the cognitive skills and complex inventions of modern humans has been attributed to “cumulative cultural evolution” (CCE), the accumulation of knowledge and skills over generations. To date, researchers have only been able to speculate about the reasons for the apparent absence of this phenomenon in nonhumans, and it has not been possible to test hypotheses regarding the mechanisms underlying it. Here, we show that it is possible to demonstrate CCE under laboratory conditions by simulating generational succession through the repeated removal and replacement of human participants within experimental groups. We created “microsocieties” in which participants were instructed to complete simple tasks using everyday materials. In one of our procedures, participants were instructed to build a paper aeroplane which flew as far as possible, and in the other, they were instructed to construct a tower of spaghetti which was as tall as possible. We show that, in both cases, information accumulates within the groups such that later generations produce designs which are more successful than earlier ones. These methods offer researchers a window to understanding CCE, allowing for experimental manipulation and hypothesis testing.