Darwin's error? Patrick Matthew and the catastrophic nature of the geologic record

In 1831, the Scottish horticulturalist Patrick Matthew (1790–1874) published a clear statement of the law of natural selection in an Appendix to his book Naval Timber and Arboriculture, which both Darwin and Wallace later acknowledged. Matthew, however, was a catastrophist, and he presented natural selection within the contemporary view that relatively long intervals of environmental stability were episodically punctuated by catastrophic mass extinctions of life. Modern studies support a similar picture of the division of geologic time into long periods of relative evolutionary stability ended by sudden extinction events. Mass extinctions are followed by recovery intervals during which surviving taxa radiate into vacated niches. This modern punctuated view of evolution and speciation is much more in line with Matthew's episodic catastrophism than the classical Lyellian–Darwinian gradualist view.     

Natural convection from leaves at realistic Grashof numbers

Abstract. The boundary layer resistance of model leaves was measured in still air, at a range of leaf-to-air temperature differences. The results were compared to those calculated from standard formulae for natural convection. The agreement between observed and calculated was only satisfactory when Grashof numbers exceeded about 105. At the lower Grashof numbers, which often prevail in nature, the observed rates of heat transfer considerably exceeded those calculated.     

Unravelling natural killer cell function: triggering and inhibitory human NK receptors

Natural killer (NK) cells represent a highly specialized lymphoid population characterized by a potent cytolytic activity against tumor or virally infected cells. Their function is finely regulated by a series of inhibitory or activating receptors. The inhibitory receptors, specific for major histocompatibility complex (MHC) class I molecules, allow NK cells to discriminate between normal cells and cells that have lost the expression of MHC class I (e.g., tumor cells). The major receptors responsible for NK cell triggering are NKp46, NKp30, NKp44 and NKG2D. The NK-mediated lysis of tumor cells involves several such receptors, while killing of dendritic cells involves only NKp30. The target-cell ligands recognized by some receptors have been identified, but those to which major receptors bind are not yet known. Nevertheless, functional data suggest that they are primarily expressed on cells upon activation, proliferation or tumor transformation. Thus, the ability of NK cells to lyse target cells requires both the lack of surface MHC class I molecules and the expression of appropriate ligands that trigger NK receptors.     

Engineering Natural and Synthetic Resistance for Nematode Management

Bioengineering strategies are being developed that will provide specific and durable resistance against plant-parasitic nematodes in crops. The strategies come under three categories: (i) transfer of natural resistance genes from plants that have them to plants that do not, to mobilize the defense mechanisms in susceptible crops; (ii) interference with the biochemical signals that nematodes exchange with plants during parasitic interactions, especially those resulting in the formation of specialized feeding sites for the sedentary endoparasites—many nematode genes and many plant genes are potential targets for manipulation; and (iii) expression in plant cells of proteins toxic to nematodes.     

目标树抚育对亚热带天然次生灌丛群落结构和多样性的影响

在浙江省临安市选择典型天然次生灌丛,分别进行封禁和目标树抚育,探讨灌丛恢复为乔木林的可能性.结果表明: 4年后,与未管护(对照)相比,封禁和目标树抚育后群落平均胸径分别提高1.3和2.6倍,平均高度分别提高0.5和1.1倍;目标树抚育林木出现了对照林分没有的4.5～8.5 cm径阶和4.5～8.5 m树高阶,形成了4 m高的新林层;灌木层物种丰富度和多样性指数没有因抚育而下降;封禁管理维持了群落的树种组成,遵循原有的演替方向;目标树抚育显著改变了群落的树种组成,提高了目的树种的重要值,近期有可能恢复成为针阔混交林群落.与封禁相比,目标树抚育在优势林木胸径和高度生长、树种组成改善等方面更能达到预想的目标.在有条件经营的情况下,可以选择目标树抚育模式对天然次生灌丛进行管理,从而达到加快群落恢复演替形成乔木林的目的.     

Ecological causes of morphological evolution in the three‐spined stickleback

The central assumption of evolutionary theory is that natural selection drives the adaptation of populations to local environmental conditions, resulting in the evolution of adaptive phenotypes. The three‐spined stickleback (Gasterosteus aculeatus) displays remarkable phenotypic variation, offering an unusually tractable model for understanding the ecological mechanisms underpinning adaptive evolutionary change. Using populations on North Uist, Scotland we investigated the role of predation pressure and calcium limitation on the adaptive evolution of stickleback morphology and behavior. Dissolved calcium was a significant predictor of plate and spine morph, while predator abundance was not. Stickleback latency to emerge from a refuge varied with morph, with populations with highly reduced plates and spines and high predation risk less bold. Our findings support strong directional selection in three‐spined stickleback evolution, driven by multiple selective agents.     

Molecular signatures of lineage‐specific adaptive evolution in a unique sea basin: the example of an anadromous goby Leucopsarion petersii

Climate changes on various time scales often shape genetic novelty and adaptive variation in many biotas. We explored molecular signatures of directional selection in populations of the ice goby Leucopsarion petersii inhabiting a unique sea basin, the Sea of Japan, where a wide variety of environments existed in the Pleistocene in relation to shifts in sea level by repeated glaciations. This species consisted of two historically allopatric lineages, the Japan Sea (JS) and Pacific Ocean (PO) lineages, and these have lived under contrasting marine environments that are expected to have imposed different selection regimes caused by past climatic and current oceanographic factors. We applied a limited genome‐scan approach using seven candidate genes for phenotypic differences between two lineages in combination with 100 anonymous microsatellite loci. Neuropeptide Y (NPY) gene, which is an important regulator of food intake and potent orexigenic agent, and three anonymous microsatellites were identified as robust outliers, that is, candidate loci potentially under directional selection, by multiple divergence‐ and diversity‐based outlier tests in comparisons focused on multiple populations of the JS vs. PO lineages. For these outlier loci, populations of the JS lineage had putative signals of selective sweeps. Additionally, real‐time quantitative PCR analysis using fish reared in a common environment showed a higher expression level for NPY gene in the JS lineage. Thus, this study succeeded in identifying candidate genomic regions under selection across populations of the JS lineage and provided evidence for lineage‐specific adaptive evolution in this unique sea basin.     

Consequences of adaptive foraging in diverse communities

1.  Selective pressures acting on foraging activities constrain the strength of interaction, hence the stability and energetic availability in food webs.
2.  Because such selective pressures are usually measured at the individual level and because most experimental and theoretical works focus on simple settings, linking adaptive foraging with community scale patterns is still a far stretch.
3.  Some recent models incorporate foraging adaptation in diverse communities. The models vary in the way they incorporate adaptation, via evolutionary or behavioural changes, and define individual fitness in various ways.
4.  In spite of these differences, some general results linking adaptation to community structure and functioning emerge. In the present article, I introduce these different models and highlight their common results.
5.  Adaptive foraging provides stability to large food web models and predicts successfully interaction patterns within food webs as well as other topological features such as food chain length.
6.  The relationships between adaptive foraging and other structuring factors particularly depend on how well connected the local community is with surrounding communities (metacommunity aspect).     

Diet of the gracile mouse opossum (Gracilinanus microtarsus) (Didelphimorphia: Didelphidae) in a Brazilian cerrado: patterns of food consumption and intrapopulation variation

The diet of the gracile mouse opossum Gracilinanus microtarsus was studied in a cerrado remnant in south-eastern Brazil through the analysis of faeces sampled from adult individuals. Patterns of food resource consumption were assessed using the statistics of per cent occurrence. Intrapopulation variation in the number of food items detected in faeces as a function of relevant factors was inferred using generalized linear models. The latter statistical formalism also allowed variation in the number of food items detected in faeces to be interpreted in terms of rate ratios among levels of significant factors. Insects, spiders, snails and fruits were detected in the faeces of G. microtarsus , with insects, particularly termites, beetles and ants, being the most frequently detected food resource. These food resources were consumed in proportion to their relative abundance in the cerrado, suggesting that G . microtarsus is an opportunistic forager feeding primarily on insects. The generalized linear model identified sex, season and food resource as significant factors affecting the number of food items detected in faeces, as well as interactions between sex and season and season and food resource. Rate ratios calculated between sexes within seasons showed that the number of food items detected in the faeces of males was larger than that detected in the faeces of females in the warm-wet and cool-dry seasons. Rate ratios calculated between seasons within sexes showed different trends in the number of food items detected in faeces for each significant food resource. It is suggested that differences in the number of food items detected in faeces between sexes within season and between seasons within sexes are related to energetic requirements associated with reproduction.     

Can whisker spot patterns be used to identify individual polar bears?

Studies of population dynamics, movement patterns and animal behavior usually require identification of individuals. We evaluated the reliability of using whisker spot patterns to noninvasively identify individual polar bears Ursus maritimus . We obtained the locations of polar bear whisker spots from photographs taken in western Hudson Bay, tested the independence of spot locations, estimated the complexity of each spot pattern in terms of information and determined whether each whisker spot pattern was reliable from its information content. Of the 50 whisker spot patterns analyzed, 98% contained enough information to be reliable, and this result varied little among observers. Photographs taken <50 m from polar bears were most useful. Our results suggest that individual identification of polar bears in the field based on whisker spot pattern variations is reliable. Researchers studying polar bear behavior or estimating population parameters can benefit from this method if proximity to the bears is feasible.