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Lukáš Gábor Vojtěch Barták Vincent Lecours 《International journal of geographical information science》2020,34(8):1567-1584
ABSTRACT Species distribution models (SDMs) are widely used in ecology and conservation. However, their performance is known to be affected by a variety of factors related to species occurrence characteristics. In this study, we used a virtual species approach to overcome the difficulties associated with testing of combined effects of those factors on performance of presence-only SDMs when using real data. We focused on the individual and combined roles of factors related to response variable (i.e. sample size, sampling bias, environmental filtering, species prevalence, and species response to environmental gradients). Results suggest that environmental filtering is not necessarily helpful and should not be performed blindly, without evidence of bias in species occurrences. The more gradual the species response to environmental gradients is, the greater is the model sensitivity to an inappropriate use of environmental filtering, although this sensitivity decreases with higher species prevalence. Results show that SDMs are affected to the greatest degree by the species response to environmental gradients, species prevalence, and sample size. Models’ accuracy decreased with sample size below 300 presences. Furthermore, a high level of interactions among individual factors was observed. Ignoring the combined effects of factors may lead to misleading outcomes and conclusions. 相似文献
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南四湖流域1980-2015年土地利用变化及其对流域生境质量的影响 总被引：1，自引：0，他引：1
生境质量在一定程度上决定了区域生物多样性维持能力的高低,评估区域生境质量对土地利用/覆被变化的响应,可以间接衡量区域生物多样性维持功能的时空变化,为生物多样性保护提供定量参考.本文以南四湖流域为例,运用InVEST-Habitat Quality模型模拟评价1980-2015年流域生境质量的时空变化,定量评估湖区退耕还湿还林和丘陵地区退耕还林2种政策情景对区域生境质量改善的效果.结果表明：35 a间流域耕地、林地和草地大量转化为建设用地,城市建设用地增长40.23%,湖泊面积减少35.56%,主要转化为渔业坑塘;南四湖流域整体生境质量处于较低水平,近35 a来快速发展的工农业生产和不断扩张的城市用地使得流域生境质量呈现降低趋势,当前平均生境质量为历年最低（0.20）.环境保护力度和人类活动剧烈程度的差异导致生境质量在空间上呈现出西部平原区（0.19） < 东部丘陵山区（0.44） < 南四湖湖区（0.81）的分布特征.近35 a来生境稀有度（即生境保存完整性指数）较高的区域主要是湖区主体和流域东部丘陵山区,但部分边缘湖区生境稀有度指数却极低,受人类活动干扰剧烈,主要原因在于沿湖渔业养殖和农业活动.定量评估湖区退耕还林还湿和流域丘陵旱地退耕还林2种政策情景对生境质量的改善效果,结果表明湖区退耕还湿还林能使湖区生境质量上升9.21%,而丘陵旱地退耕还林可使流域平均生境质量提高16.75%. 相似文献
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Analysis of quantitative and qualitative composition of rare phytoplankton species was performed using a data set collected over a large geographic area (four eutrophic gulfs of the Aegean Sea, E. Mediterranean Sea) during 2002–2003. We examined the effects of excluding rare species on comparisons of species richness, diversity, similarity and niche breadth as well as the regional and seasonal contribution of rare species to cell abundance and carbon biomass. Overall, the total of 401 species included 182 rare species contributing 45.1% of the total species number. However, there was a considerable variation in this relationship among the other parameters, as rare species contributed only 6.4% of total cell abundance, 13.1% of total species diversity, 21.2% of total cell biovolume and 16.6% of total carbon biomass. The results showed that rarity may be a significant issue in studies detecting and quantifying phytoplankton community structure. 相似文献
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《African Journal of Marine Science》2013,35(3):311-318
The salinity tolerances of four South African species of limpet in the genus Siphonaria were experimentally tested, in the context that one of them, S. compressa, is South Africa's most endangered marine mollusc and is restricted to two lagoonal localities that normally experience little variation in salinity. Its habitat is additionally restricted in that it occurs only on the eelgrass Zostera capensis. The other three species, S. capensis, S. concinna and S. serrata, are abundant and widespread on temperate rocky shores. We hypothesised that S. compressa would have limited tolerance to low salinities, contributing to its absence from otherwise suitable estuaries that experience regular fluctuations of salinity. The percentage survival of the limpets was recorded in salinities ranging from 2 to 35 over that period. Both salinity and species significantly affected the survival of the limpets over the 96 hours. Survival was highest in salinities close to those of normal seawater, and greatly reduced in the hypo saline waters. S. compressa had the lowest salinity tolerance of the four species, its time-to-50% mortality in hyposaline waters being significantly less than that for the other three species, which differed in a manner that could be correlated with their zonation patterns. Restriction to eelgrass, coupled with low salinity tolerance, probably explains why S. compressa is found at only two localities, both of which normally experience salinities close to that of seawater. Even there, mass mortalities of S. compressa have been recorded in association with die-backs of eelgrass after abnormal freshwater flooding or sedimentation—further emphasising the vulnerability of S. compressa to extinction. 相似文献
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Taxonomic sufficiency and the influence of rare species on variation partitioning analysis of a polychaete community 
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下载免费PDF全文 Variation partitioning is an important tool to investigate the importance of spatial structure to species distribution in communities, but its use is lacking in marine ecosystems. The influence of rare species and the level of taxonomic resolution are important features to be considered when planning sampling designs and efforts for community studies. We tested the significance of spatial and environmental components to species distribution of a polychaete community, considering how the results varied among models with increasingly rare species (and contrasting metrics), and among models with distinct taxonomic levels. For all models evaluated, both spatial and environmental components significantly explained the structure of species distribution. However, spatial processes explained a higher percentage of variance than environmental ones in almost all models. The inclusion of rare species did not influence the outcome in most models, with the exception of a Chi‐square distance model with all species included. Family taxonomic level was sufficient to detect the relative contribution of both components, but the number of environmental variables included in the model was higher for the genus level. The influence of rare species was related to the metric applied to the analysis. If weight to rare species is not desirable, the use of a few dominant species coupled with the Hellinger function can provide a good surrogate to the whole sampled community in variation partition analysis. The genus level is suggested as an appropriate taxonomic level with which to evaluate the relevance of spatial and environmental components in polychaete community studies. 相似文献
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Abstract. Small-scale patterns of low-, mid- and high-shore intertidal species density, richness and abundance were systematically examined to assess the potential influence of 'mobility' on spatial community dynamics and diversity. Mobile taxa outnumbered sessile species by approximately 2:1, whereas sessile individuals were over 12 times as numerous as mobile ones over the entire study site. Patterns of density, richness and abundance differed with shore level and substratum. The results also highlighted the importance of clearly distinguishing between species density and species richness when examining spatially quantitative data. The rank order of habitats from highest to lowest species density was not the same when analysed in order of species richness. The potential for the mobile proportion of assemblages to influence small-scale diversity assessment through movement was greater at mid- and high-shore zones because the ratio of mobile species was higher and abundance (relative to the lower shore) was low. These observations might reflect the relative influence of the land–sea gradient of immersion on diversity and mobility in intertidal communities. The influence of mobile organisms on marine ecosystem function may be significant because small-scale patterns of movement are known to positively influence biodiversity. High richness paired with low abundance, however, may result in underestimating the functional role of mobile intertidal species. 相似文献
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Fluctuations and Variations in Coastal Marine Environments 总被引：2，自引：0，他引：2
Abstract. The manifold aspects of variability of coastal marine ecosystems are reviewed, with special reference to the response of species and communities. Fluctuations are defined as recurrent modifications in community structure, for instance due to seasonality, whereas variations are defined as changes permanently leading from a given community to a different one. Both patterns are described and linked to the interaction between life history traits and environmental factors. Resting stages are proposed to play a still underestimated role in the dynamics of coastal communities, especially for plankton. Rare species are considered as an essential constant of communities, being the source of potential variation and alternance in the contribution to the standing biomass. 相似文献
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翠华山山崩地貌,类型齐全,山崩活动具有多期性,可以识别出三期,断裂及地震是形成山崩的主因。得天独厚的地质地理条件使得山崩遗迹得以完整保留,巨石景观资源十分珍稀。经与全世界山崩地质遗迹比较,翠华山单个崩石体积居世界第一位;崩石堆积总体积居中国第一位、世界第三位;山崩地貌遗迹景观旅游资源居世界第一位,它是大自然留给人类的宝贵遗产。 相似文献
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