海南尖峰岭热带山地雨林物种多样性空间分布格局的尺度效应

物种多样性的空间分布格局和维持机制是群落生态学的基本问题。为了探讨海南尖峰岭地区物种多样性空间分布格局的尺度效应, 以海南尖峰岭热带山地雨林60 hm²样地为研究对象, 分析了物种丰富度、物种多度、Shannon-Wiener指数、Simpson指数以及Pielou均匀度指数随6个空间取样尺度(5 m × 5 m、10 m × 10 m、20 m × 20 m、40 m × 40 m、100 m ×100 m、200 m × 200 m)的变化。结果表明: 相比Simpson指数和Pielou均匀度指数, 物种丰富度、多度以及Shannon-Wiener指数具有更为明显的空间尺度效应; 物种丰富度的方差随取样尺度增加呈现单峰分布特征, 并且在20 m × 20 m尺度上达到最大值, 而物种多度的方差随取样尺度的增加而增大; 物种丰富度和多度的正相关性随着取样尺度的增加逐渐减小甚至消失, 这可能与随取样尺度增加生境异质性增加有关; 取样尺度对3个物种多样性指数空间分布的影响可能与研究区域内稀有种的组成有关。     

Analysis of diurnal boundary layer development in boreal forests: measurements and simulations

Aims Combining field data analysis and modeling, this study investigates factors influencing the diurnal boundary layer (BL) development in boreal forest.Methods Field data analysis used both air sounding and surface flux measurements collected during the Boreal Ecosystem–Atmosphere Study field campaigns in central Canada. Model study applied a non-local transilient turbulence theory (TTT) to simulate the impact of the heterogeneous boundary conditions together with initial conditions on the BL development at the Candle Lake and Thompson release sites over boreal forests. Boundary conditions were characterized by the integrated surface flux measurements from different forest stands. The lake effect was included in constructing the surface fluxes at Candle Lake release site.Important findings Analyses of serial upper air sounding data and tower flux data indicate strong linear impacts of surface sensible heat forcing on the diurnal BL development above boreal forests. The regression slopes on the relationship between the BL development and the surface fluxes reflect the influences of initial boundary conditions to the BL developments. Both the modeled and the measured diurnal BLs show that lakes reduce sensible heat flux, leading to a shallower boundary in Candle Lake than in Thompson. Comparison of the model results and field measurements on the BL profiles indicates that the TTT model has the capability to simulate the BL development above boreal forests for sunny, rainfall or cloudy days. This study demonstrates the importance of lake on surface fluxes and BL development. The modeling effort shows the potential to couple the transilient theory with a land surface process model to study land surface and atmosphere interaction in boreal forest.     

An <Emphasis Type="Italic">S-RNase</Emphasis>-Based Gametophytic Self-Incompatibility System Evolved Only Once in Eudicots

It has been argued that the common ancestor of about 75% of all dicots possessed an S-RNase-based gametophytic self-incompatibility (GSI) system. S-RNase genes should thus be found in most plant families showing GSI. The S-RNase gene (or a duplicate) may also acquire a new function and thus genes belonging to the S-RNase lineage may also persist in plant families without GSI. Nevertheless, sequences that belong to the S-RNase lineage have been found in the Solanaceae, Scrophulariaceae, Rosaceae, Cucurbitaceae, and Fabaceae plant families only. Here we search for new sequences that may belong to the S-RNase lineage, using both a phylogenetic and a much faster and simpler amino acid pattern-based approach. We show that the two methods have an apparently similar false-negative rate of discovery (~10%). The amino acid pattern-based approach produces about 15% false positives. Genes belonging to the S-RNase lineage are found in three new plant families, namely, the Rubiaceae, Euphorbiaceae, and Malvaceae. Acquisition of a new function by genes belonging to the S-RNase lineage is shown to be a frequent event. A putative S-RNase sequence is identified in Lotus, a plant genus for which molecular studies on GSI are lacking. The hypothesis of a single origin for S-RNase-based GSI (before the split of the Asteridae and Rosidae) is further supported by the finding of genes belonging to the S-RNase lineage in some of the oldest lineages of the Asteridae and Rosidae, and by Baysean constrained tree analyses.     

Facilitation, competition, and vegetation patchiness: from scale free distribution to patterns

A new technique for the modeling of perennial vegetation patchiness in the arid/semiarid climatic zone is suggested. Incorporating the stochasticity that affects life history of seedlings and the deterministic dynamics of soil moisture and biomass, this model is flexible enough to yield qualitatively different forms of spatial organization. In the facilitation-dominated regime, scale free distribution of patch sizes is observed, in correspondence with recent field studies. In the competition controlled case, on the other hand, power-law statistics is valid up to a cutoff, and an intrinsic length scale appears.     

Mimicry and foraging behaviour of two tropical sand-flat octopus species off North Sulawesi, Indonesia

The so-called 'mimic octopuses' of tropical Indonesia are reputed to mimic up to 13 species of other local marine organisms. We tested for mimicry by allowing individuals of two species of octopus to habituate to divers, then observing and filming two species continuously as they foraged daily in the same open, featureless volcanic sand habitat. Mimicry of a local, abundant flounder occurred commonly during 5 days of natural foraging: nearly 500 episodes were analysed. Both octopus species mimicked the shape, swimming actions, speed, duration, and sometimes the coloration of swimming flounders. During flounder mimicry, octopuses were actively moving and conspicuous, whereas immediately before and after flounder mimicry, they were camouflaged and motionless (sitting or very slowly crawling). Furthermore, when motionless, octopuses assumed body patterns and postures that resembled small sponges, tube-worm tubes, or colonial tunicates, which were among the few objects in the open sand habitat. The key finding was that octopuses used flounder mimicry only when their movement would give away camouflage in this open habitat. In all cases, octopuses used mimicry as a primary defense. Several interactions with fishes and stomatopods were filmed and typical secondary defense behaviours, not mimicry, were used by the octopuses. Foraging occurred twice per day and two tactile feeding tactics were used. Dens and food were not limiting; thus, we observed a highly unusual circumstance of a guild of small, long-armed octopus species that shared the same habitat, den sources, food, activity period, and some behaviours.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 23–38.     

Spatial patterns in impacts of fishing on temperate rocky reefs: Are fish abundance and mean size related to proximity to fisher access points?

Effects of fishing on marine communities are becoming increasingly evident, yet little is known of the spatial extent of impacts, particularly for multiple impacts distributed over broad scales. We tested the common perception that commercial and recreational fishing on inshore temperate reefs generate spatial impacts that diminish with distance from fisher access points. We collected data on harvested and non-harvested reef species using underwater visual censuses at 133 shallow rocky reef sites around Tasmania and tested for relationships between assemblage and species level indices of fishing impacts and distance to the nearest boat launching ramp. Slopes of size spectra of fish communities tended to decrease with distance from the nearest boat ramp, with this relationship apparently resulting from low numbers of large fish (> 30 cm TL) and a greater number of smaller fish (< 15 cm TL) at sites closest to access points. At the species level, relationships were evident either in the abundance of legal individuals or the mean size of harvested species with distance to the nearest boat ramp, except for rock lobster. Patterns for rock lobster differed when areas in which commercial or recreational fisheries dominated were considered separately from the statewide analysis. A pattern of increasing numbers of legal lobsters with increasing distance from boat ramps was observed, but only in the areas in which the recreational fishery dominated. Observed relationships in all species were consistent with greater fishing impacts at sites closest to boat ramps, with the exception of exploited wrasses. Banded morwong, which are subject to a live export fishery, appeared to be most affected by proximity to boat ramps. Conversely, no relationships were found between the abundance or size of the most frequently occurring non-harvested species and distance to boat ramps.These results support the hypothesis that greater fishing impacts occur at more accessible sites over the entire Tasmanian coastline. The variability of results among individual species are likely, at least in part, to be related to differences in fisheries characteristics such as vessel size and range, as well as the suitability of our methods for detecting impacts. The potential of such a pattern in fishing impacts to be evident in other locations will thus likely depend on characteristics of the particular fishes and fisheries.     

Influence of chimpanzee predation on the red colobus population at Ngogo, Kibale National Park, Uganda

Frequent hunting of red colobus monkeys (Procolobus rufomitratus) takes place at all long-term chimpanzee (Pan troglodytes) study sites where both species are present. Red colobus are the most commonly selected prey of chimpanzees even when other monkey species are more abundant. In particular, the chimpanzee community at Ngogo, Kibale National Park, Uganda, preys heavily on red colobus monkeys: the chimpanzee hunting success rate is extremely high, and chimpanzees kill many individuals per successful hunt. Census data had suggested that the red colobus population is declining and that predation by chimpanzees may be contributing to this decline. In this paper, I address the impact of hunting on the red colobus population at Ngogo. To test the hypothesis that chimpanzee hunting is sustainable, I am using demographic data collected on red colobus monkeys over a period of 3 years, as well as fecundity and mortality data from previous studies of this species. I apply matrix models and vortex analyses using a sensitivity analysis approach to project future population development. Results show that current rates of hunting are not sustainable, but that chimpanzees are neither more “noble”, nor more “savage” than humans are, but that they also hunt to ensure maximum benefit without regard for the consequences for the prey population.     

Morphological variation of major human populations based on nonmetric dental traits

The patterns of inter- and intra-regional variation among 12 major geographical groups from around the world were investigated based on 15 nonmetric dental traits. The R-matrix method was applied using a pooled within-group variance-covariance matrix estimated with the maximum likelihood method (tetrachoric correlation matrix) and the threshold value for each trait estimated by univariate probit analysis. Using average heritability rates that range from 0.40 to 1.00, the inter-regional variation represented by Fst falls between 7.19% and 16.23% of the total variance. This range of variation is compatible with those obtained by genetic, craniometric, and odontometric data. Subsaharan Africans show the largest intra-regional diversity among the groups compared. The degree of intra-regional variation shows, moreover, rough clinalities from subsaharan Africa to peripheral regions. The relationship between regional variation and geographic distance from subsaharan Africa supports serial bottlenecks and the founder effect of ancient populations originating in Africa. The variation of East/Northeast Asians is relatively large, suggesting a complex population history such as possible earlier divergence and multiple migrations from outside sources. The present findings are in agreement with both the recent African model for the origin of anatomically modern humans and the current scenario for human migration history suggested by genetic analyses.