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71.
Aim To investigate the biological meaning of equations used to apply the general dynamic model (GDM) of oceanic island biogeography proposed by R. J. Whittaker, K. A. Triantis and R. J. Ladle. Location Analyses are presented for 17 animal groups living on the Aeolian Islands, a volcanic archipelago in the central Mediterranean, near Sicily. Methods In addition to the mathematical implementation of the GDM proposed by Whittaker, Triantis and Ladle, and termed here logATT2 (, where S is species number or any other diversity metric, t is island age, A is island area, and a, b, c and d are fitted parameters), a new implementation based on the Arrhenius equation of the species–area relationship (SAR) is investigated. The new model (termed powerATT2) is: . For logATT2 and powerATT2 models, equations were developed to calculate (1) the expected number of species at equilibrium (i.e. when the island has reached maturity) per unit area (Seq), and (2) the time required to obtain this value (teq). Whereas the intercept in the Gleason model (S = C + z log A) or the coefficient of the Arrhenius power model (S = CAz) of the SAR can be considered measures of the expected number of species per unit area, this is not the case for the parameter a of the ATT2 models. However, values of Seq can be used for this purpose. The index of ‘colonization ability’ (CAB), calculated as the ratio , may provide a measure of the mean number of species added per unit area per unit time. Results Both ATT2 models fitted most of the data well, but the powerATT2 model was in most cases superior. Equilibrial values of species richness (Seq) varied from c. 3 species km?2 (reptiles) to 100 species km?2 (mites). The fitted curves for the powerATT2 model showed large variations in d, from 0.03 to 3. However, most groups had values of d around 0.2–0.4, as commonly observed for the z‐values of SARs modelled by a power function. Equilibration times ranged from about 170,000 years to 400,000 years. Mites and springtails had very high values of CAB, thus adding many more species per unit area per unit time than others. Reptiles and phytophagous scarabs showed very low values, being the groups that added fewest species per unit area per unit time. Main conclusions Values of equilibrial species richness per unit area are influenced by species biology (e.g. body size and ecological specialization). Theoretical and empirical evidence suggests that higher immigration rates should increase the z‐values of the Arrhenius model. Thus, in the same archipelago, groups with larger z‐values should be characterized by higher dispersal ability. Results obtained here for the parameter d conform to this prediction.  相似文献   
72.
The biogeographical analysis of Arctic and North Atlantic waters north of 30°N is based upon the distribution of 150 Mysidacea (Crustacea) species. The reasons for biogeographical divisions conducted independently by faunae of pelagic and benthopelagic mysids are adduced. The original schemes of the Arctic and North Atlantic division are proposed. Using the fauna of pelagic mysids, one biogeographical realm, one province and one transitional zone are designated in cold and temperate waters. Using the fauna of benthopelagic mysids, one biogeographical realm and four provinces are designated in those waters.  相似文献   
73.
We examined latitudinal gradients in central value and diversity of body mass of primates to increase understanding of the Forster effect (decrease in taxonomic diversity with increasing latitude) and the Bergmann effect (increase of body mass with latitude). Data are from the literature. We used species’ median body mass of females and mid-latitude (N = 164). We account for phylogenetic effects with comparative analysis by independent contrasts and analysis at differing taxonomic levels. Globally, diversity of both taxonomy and body mass declined significantly with increasing latitude. The decrease in the range of body masses with increasing latitude was caused mainly by the absence of several small-bodied clades at higher latitudes, but also by the absence there of great apes. The disappearance of the small-bodied clades caused an increase in median body mass with latitude, i.e., primates show a significant taxon-wide Bergmann effect, including with phylogenetic correction. Within the Primates, the Bergmann effect was significant within taxa that extend from the equator the farthest into temperate regions: the Old World infraorder Catarrhini, family Cercopithecidae, and subfamily Cercopithecinae; the Asian Cercopithecidae; and in Southeast Asian Sunda, Macaca. The results accord with hypotheses for the Forster effect that latitudinal gradients in taxonomic diversity result from high rates of speciation in the tropics, and ecological, and therefore evolutionary, constraints on diversity at higher latitudes. For the Bergmann effect, the results support energetic hypotheses that the very largest-bodied and the small-bodied taxa cannot survive the long periods of limited resources at higher latitudes.  相似文献   
74.
A comprehensive taxonomic revision of Goniothalamus species (Annonaceae) occurring in Thailand is presented for the first time. Twenty-five species are recognized, including three that are described as new to science ( Goniothalamus aurantiacus from South-Western Thailand, Goniothalamus maewongensis from Northern Thailand, and Goniothalamus rongklanus from Northern and North-Eastern Thailand). Several taxonomic and nomenclatural misunderstandings are corrected. The name G. griffithii is shown to be widely misapplied for populations in Northern Thailand, for which the name G. calvicarpus should be applied; 'true' G. griffithii is restricted to South-Western Thailand and Myanmar. In addition, the widely used name G. marcanii is shown to be a synonym of G. tamirensis , and the name G. latestigma , previously regarded as a synonym of G. undulatus , is reinstated. Goniothalamus cheliensis is furthermore newly recorded from Thailand. Most species are restricted to Peninsular Thailand and represent a Malesian floristic component.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 156 , 355–384.  相似文献   
75.
Aim Species distribution models and geographical information system (GIS) technologies are becoming increasingly important tools in conservation planning and decision‐making. Often the rich data bases of museums and herbaria serve as the primary data for predicting species distributions. Yet key assumptions about the primary data often are untested, and violation of such assumptions may have consequences for model predictions. For example, users of primary data assume that sampling has been random with respect to geography and environmental gradients. Here we evaluate the assumption that plant voucher specimens adequately sample the climatic gradient and test whether violation of this assumption influences model predictions. Location Bolivia and Ecuador. Methods Using 323,711 georeferenced herbarium collections and nine climatic variables, we predicted the distribution of 76 plant species using maximum entropy models (MAXENT) with training points that sampled the climate environments randomly and training points that reflected the climate bias in the herbarium collections. To estimate the distribution of species, MAXENT finds the distribution of maximum entropy (i.e. closest to uniform) subject to the constraint that the expected value for each environmental variable under the estimated distribution matches its empirical average. The experimental design included species that differed in geographical range and elevation; all species were modelled with 20 and 100 training points. We examined the influence of the number of training points and climate bias in training points, elevation and range size on model performance using analysis of variance models. Results We found that significant parts of the climatic gradient were poorly represented in herbarium collections for both countries. For the most part, existing climatic bias in collections did not greatly affect distribution predictions when compared with an unbiased data set. Although the effects of climate bias on prediction accuracy were found to be greater where geographical ranges were characterized by high spatial variation in the degree of climate bias (i.e. ranges where the bias of the various climates sampled by collections deviated considerably from the mean bias), the greatest influence on model performance was the number of presence points used to train the model. Main conclusions These results demonstrate that predictions of species distributions can be quite good despite existing climatic biases in primary data found in natural history collections, if a sufficiently large number of training points is available. Because of consistent overprediction of models, these results also confirm the importance of validating models with independent data or expert opinion. Failure to include independent model validation, especially in cases where training points are limited, may potentially lead to grave errors in conservation decision‐making and planning.  相似文献   
76.
Aim The question whether free‐living protists are generally cosmopolitan is currently a matter of debate. In this study we investigate the geographical distribution of a distinctive testate amoeba species, Nebela ansata, and use our data to assess the potential for highly restricted distribution patterns in some protist species. Location Global. Methods We analysed (1) 3400 testate amoeba publications from North America and other continents, (2) unpublished slides of the Penard Collection of the Natural History Museum, London, UK, and (3) 104 Sphagnum samples from eastern North America. Non‐metric multidimensional scaling (NMDS) was used to visualize the similarities in testate amoeba community composition among 1012 North American samples, including two communities that contained N. ansata. Results We rediscovered N. ansata at a site in New Jersey located close to its type locality, and in Nova Scotia. We also report the existence of an apparently unpublished museum specimen originally collected from New Jersey. Our extensive literature survey confirmed the presence of this species only in the temperate part of eastern North America. The NMDS revealed that communities with N. ansata were less similar to each other than to communities from other parts of North America, suggesting that favourable habitats for N. ansata occur in other Sphagnum‐dominated peatlands, a habitat type that has been extensively sampled in North America and elsewhere. Main conclusions These data provide an unusually convincing case of a free‐living microorganism with a very limited distribution range in the temperate part of eastern North America. The remarkably restricted distribution of N. ansata highlights the extent of our ignorance about the natural history of free‐living microorganisms, and raises questions about the lack of attention to microbial diversity in conservation biology.  相似文献   
77.
《植物生态学报》1958,44(8):842
倒木是森林生态系统维持健康和更新的重要组成部分, 在倒木不同腐解阶段, 倒木上定植的苔藓植物组合的差异尚不清楚。为深入探讨倒木上苔藓植物组合变化规律及其影响因素, 该文对西藏色季拉山同一地点不同腐解程度的4株华山松(Pinus armandii)倒木上的苔藓植物进行了样方调查和数据分析。结果表明: 4株倒木上40个样方共有苔藓植物22科52种, 其中藓类13科38种, 苔类9科14种; 以恒有优势种为特征进行划分, 共得到14个物种组合。随着倒木腐解程度加大以及周围环境的不断改变, 生长其上的苔藓植物物种多样性逐渐增加, 但组合数量和苔藓总盖度却呈现先增大后减小的趋势。苔藓物种由耐旱性强的丛生型藓类, 如木灵藓科、白发藓科, 逐渐演替为喜阴湿环境、快速生长的垫状或毯状藓类, 如提灯藓科、羽藓科和青藓科。倒木苔藓植物组合空间结构复杂程度逐渐增大。倒木是多种苔藓植物选择的重要生长基质, 其上苔藓植物受倒木的腐解程度、水分和光照等条件的影响而发生相应的物种组合变化。  相似文献   
78.
Evolutionary biologists have often suggested that ecology is important in speciation, in that natural selection may drive adaptive divergence between lineages that inhabit different environments. I suggest that it is the tendency of lineages to maintain their ancestral ecological niche (phylogenetic niche conservatism) and their failure to adapt to new environments which frequently isolates incipient species and begins the process of speciation. Niche conservatism may be an important and widespread component of allopatric speciation but is largely unstudied. The perspective outlined here suggests roles for key microevolutionary processes (i.e., natural selection, adaptation) that are strikingly different from those proposed in previous literature on ecology and speciation. Yet, this perspective is complementary to the traditional view because it focuses on a different temporal stage of the speciation process.  相似文献   
79.
Aim To assemble a continental‐scale data set of all available anuran records and investigate trends in endemism and species richness for the Anura. Location Continental Australia. Methods 97,338 records were assembled, covering 75% of the continent. A neighbourhood analysis was applied to recorded locations for each species to measure richness and endemism for each half‐degree grid square (c. 50 km) in the continent. This analysis was performed for all anurans, and also for each of the three main anuran families found in Australia. A Monte Carlo simulation was used to test a null hypothesis that observed centres of endemism could result simply from an unstructured overlapping of species ranges of different sizes. Results Eleven main centres of anuran endemism were identified, the most important being the Wet Tropics and the south‐west near Bunbury‐Augusta and near Walpole. With the exception of south‐western Australia, all of the identified significant endemic centres are in the northern half of the continent. The regions identified as significant for endemism differed from those identified for species richness and are more localized. Species richness is greatest in the Wet Tropics and the Border Ranges. High species richness also occurs in several areas not previously identified along the east and northern coasts. Main conclusions Weighted endemism provides a new approach for determining significant areas for anuran conservation in Australia and areas can be identified that could be targeted for beneficial conservation gains. Patterns in endemism were found to vary markedly between the three main anuran families, and south‐eastern Australia was found to be far less significant than indicated by previous studies. The need for further survey work in inland Australia is highlighted and several priority areas suggested. Our results for species richness remain broadly consistent with trends previously observed for the Australian Anura.  相似文献   
80.
Bacterial assemblages from subsurface (100 m depth), meso- (200-1000 m depth) and bathy-pelagic (below 1000 m depth) zones at 10 stations along a North Atlantic Ocean transect from 60°N to 5°S were characterized using massively parallel pyrotag sequencing of the V6 region of the 16S rRNA gene (V6 pyrotags). In a dataset of more than 830,000 pyrotags, we identified 10,780 OTUs of which 52% were singletons. The singletons accounted for less than 2% of the OTU abundance, whereas the 100 and 1000 most abundant OTUs represented 80% and 96% respectively of all recovered OTUs. Non-metric Multi-Dimensional Scaling and Canonical Correspondence Analysis of all the OTUs excluding the singletons revealed a clear clustering of the bacterial communities according to the water masses. More than 80% of the 1000 most abundant OTUs corresponded to Proteobacteria of which 55% were Alphaproteobacteria, mostly composed of the SAR11 cluster. Gammaproteobacteria increased with depth and included a relatively large number of OTUs belonging to Alteromonadales and Oceanospirillales. The bathypelagic zone showed higher taxonomic evenness than the overlying waters, albeit bacterial diversity was remarkably variable. Both abundant and low-abundance OTUs were responsible for the distinct bacterial communities characterizing the major deep-water masses. Taken together, our results reveal that deep-water masses act as bio-oceanographic islands for bacterioplankton leading to water mass-specific bacterial communities in the deep waters of the Atlantic.  相似文献   
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