Distance decay of community dynamics in rocky intertidal sessile assemblages evaluated by transition matrix models

It is well known that the similarity in species composition between two communities decays with the geographic distance that separates them. It is thus likely that the similarity in the dynamics of two communities also decays with distance, because the distance–decay relationship is fundamental in nature. However, the distance–decay relationships of community dynamics have not yet been revealed. We used transition matrix models to evaluate distance–decay relationships of seasonal community dynamics (from spring to summer) in rocky intertidal sessile assemblages along the Pacific coast of Japan between 31°N and 43°N. We evaluated the distance–decay relationships of whole-community dynamics and of three dynamics-related components—recruitment, disturbance, and species interaction (competition and facilitation)—for communities separated by distances ranging from several meters to thousands of kilometers. The similarity of the recruitment dynamics among communities declined rapidly with distance within the fine spatial scale, but only moderately within larger scales. The similarity of the disturbance dynamics was independent of distance, and the similarity of species interaction declined slightly with increasing distance. The similarity of whole-community dynamics declined rapidly with distance at a fine spatial scale and moderately at larger scales. The fact that the distance–decay relationship of whole-community dynamics was similar to that of recruitment may suggest that recruitment processes are the most important determinant of spatial variability of community dynamics at our study sites during the study period.     

Seasonal changes in community structure along a vertical gradient: patterns and processes in rocky intertidal sessile assemblages

Population Ecology - Here we considered two fundamental questions in community ecology regarding the relationship between seasonal changes in community structure and environmental gradients: (i)...     

Spatial patterns and coexistence mechanisms in systems with unidirectional flow

River ecosystems are the prime example of environments where unidirectional flow influences the dispersal of individuals. Spatial patterns of community composition and species replacement emerge from complex interplays of hydrological, geochemical, biological, and ecological factors. Local processes affecting algal dynamics are well understood, but a mechanistic basis for large scale emerging patterns is lacking. To understand how these patterns could emerge in rivers, we analyze a reaction-advection-diffusion model for two competitors in heterogeneous environments. The model supports waves that invade upstream up to a well-defined "upstream invasion limit". We discuss how these waves are produced and present their key properties. We suggest that patterns of species replacement and coexistence along spatial axes reflect stalled waves, produced from diffusion, advection, and species interactions. Emergent spatial scales are plausible given parameter estimates for periphyton. Our results apply to other systems with unidirectional flow such as prevailing winds or climate-change scenarios.     

Latitudinal gradient of species diversity: multi-scale variability in rocky intertidal sessile assemblages along the Northwestern Pacific coast

This study examined the latitudinal gradient of species diversity of rocky intertidal sessile assemblages on the slopes of rocks along the Northwestern Pacific coast of Japan, located between 31°N and 43°N, by explicitly incorporating an hierarchical spatial scale into the monitoring design. The specific questions were to examine: (1) whether there is a latitudinal gradient of regional diversity, (2) how spatial components of the regional diversity (local diversity and turnover diversity) vary with latitude depending on spatial scale, and (3) whether the latitudinal gradient differs between different measures of species diversity, i.e. species richness and Simpsons diversity index. We measured coverage and the presence or absence of all sessile organisms in a total of 150 census plots established at five shores in each of six regions. The results showed that there were clear latitudinal gradients in regional species richness and in species turnover among shores. However, these patterns were not reflected in smaller-scale local species richness. For Simpsons diversity index, there was no evidence of latitudinal clines either in regional diversity or in spatial components. These results suggest that relative abundance of common species does not vary along latitude, while the number of rare species increases with decreasing latitude.

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An erratum to this article can be found at     

Competitive coexistence in spatially structured environments: a synthesis

Theoretical developments in spatial competitive coexistence are far in advance of empirical investigations. A framework that makes comparative predictions for alternative hypotheses is a crucial element in narrowing this gap. This review attempts to synthesize spatial competition theory into such a framework, with the goal of motivating empirical investigations that adopt the comparative approach. The synthesis presented is based on a major axis, coexistence in spatially homogeneous vs. heterogeneous competitive environments, along which the theory can be organized. The resulting framework integrates such key concepts as niche theory, spatial heterogeneity and spatial scale(s) of coexistence. It yields comparative predictions that can guide empirical investigations.     

Temporal variation of rocky intertidal resident fish assemblages - patterns and possible mechanisms with a note on sampling protocols

In this paper we review the temporal patterns of variation of rocky intertidal resident fish assemblages and discuss possible mechanisms that may explain these patterns. These assemblages tend to be highly resilient and stable on an inter-annual basis, but tend to undergo marked seasonal fluctuations, as different species recruit and reach different phases of their life cycles. Larval supply is usually not a limiting factor suggesting that post-recruitment deterministic mechanisms exert a strong influence on assemblage organization. At methodological level, it is argued that traditional destructive sampling techniques should be avoided whenever possible. It is proposed that a deeper understanding of these assemblages requires more detailed information on intraspecific interactions between members of each constituent species, and information on the interactions between limited numbers of species for which mutually influences are particularly strong. It is argued that size, topography and biotic cover of a pool may provide a limited number of favourable sites for fishes of a given species and class size so that intraspecific competition, and possibly predation of the individuals less able to get access to best sites, may explain to a considerable extent the inter-annual stability and resilience of these assemblages.     

Position on slope,disturbance, and tree species coexistence in a Seasonal Semideciduous Forest in SE Brazil

We investigated the influence of position on a slope (plot relative elevation) and vegetation disturbance (the tallest tree height per plot) on community composition and diversity in a SE Brazilian Seasonal Semideciduous Forest (46°55′ W, 22°50′ S). Trees with dbh ≥5 cm were sampled in one hundred 10 × 10 m plots randomly placed in a 6.5-ha stand. Through partial Mantel test, floristic dissimilarities among plots (Jaccard index computed with species abundance in each plot) were correlated with environmental distances among plots (Euclidian distance index computed with relative elevation and the tallest tree height values in each plot). Relative elevation and the tallest tree per plot height were individually correlated with floristic gradients expressed by PCA axes scores using Pearson’s correlation coefficient. Through resampling, we compared diversity (richness, Berger-Parker D and Shannon H′) among plots in the drier (up) and moister (low) ends of the slope. Floristic dissimilarities were significantly correlated with environmental distances even after geographic distances among plots have been partialled out (r _m = 0.1274, p < 0.001). The first two PCA axes accounted for 22% of the total variance. After Bonferroni and Dutilleul’s corrections, axis 1 showed a marginally significant correlation with plot relative elevation (r = − 0.4097, p = 0.0309), and axis 2 was significantly correlated with the tallest tree height per plot (r = 0.2953, p = 0.0106). Position on the slope and vegetation disturbance were reliable predictors of community composition, thus suggesting the operation of niche assembly organizing processes. Richness and diversity (H′) decreased and dominance (D) increased with elevation on the slope. Dominance increase from D ₍₃₀₀₎ = 0.11 (confidence interval = 0.091–0.131) to D ₍₃₀₀₎ = 0.19 (CI = 0.165–0.210) surpassed the expected dominance increase based on the reduction of richness alone: D ₍₃₀₀₎ = 0.13 (CI = 0.110–0.140), thus highlighting the niche partitioning assembly of the community, especially among abundant species. Given the great amount of floristic variability remaining unexplained, stochastic processes, such as those related to dispersal limitation, may also have influence on the community composition. Therefore, both niche assembly and chance events can operate even on a fine local scale.     

The effects of plant dispersion and prey density on parasitism rates in a naturally patchy habitat

Despite extensive research on parasitoid-prey interactions and especially the effects of heterogeneity in parasitism on stability, sources of heterogeneity other than prey density have been little investigated. This research examines parasitism rates by three parasitoid species in relationship to prey density and habitat spatial pattern. The herbivore Itame andersoni (Geometridae) inhabits a subdivided habitat created by patches of its host plant, Dryas drummondii, in the Wrangell Mountains of Alaska. Dryas colonizes glacial moraines and spreads clonally to form distinct patches. Habitat subdivision occurs both on the patch scale and on the larger spatial scale of sites due to patchy successional patterns. Itame is attacked by three parasitoids: an ichneumonid wasp (Campoletis sp.), a braconid wasp (Aleiodes n. sp.), and the tachinid fly (Phyrxe pecosensis). I performed a large survey study at five distinct sites and censused Itame density and parasitism rates in 206 plant patches for 1–3 years. Parasitism rates varied with both plant patch size and isolation and also between sites, and the highest rates of overall parasitism were in the smallest patches. However, the effects of both small- and large-scale heterogeneity on parasitism differed for the three parasitoid species. There was weak evidence that Itame density was positively correlated with parasitism for the braconid and tachinid at the patch scale, but density effects differed for different patch sizes, patch isolations, and sites. At the site scale, there was no evidence of positive, but some indication of negative density-dependent parasitism. These patterns do not appear to be driven by negative interactions between the three parasitoid species, but reflect, rather, individual differences in habitat use and response to prey density. Finally, there was no evidence that parasitism strongly impacted the population dynamics of Itame. These results demonstrate the importance of considering habitat pattern when examining spatial heterogeneity of parasitism and the impacts of parasitoids. Received: 3 June 1999 / Accepted: 4 October 1999     

Predicting wild boar damages to croplands in a mosaic of agricultural and natural areas

Crop damages by wildlife is a frequent form of human-wildlife conflict. Identifying areas where the risk of crop damages is highest is pivotal to set up preventive measures and reduce conflict. Species distribution models are routinely used to predict species distribution in response of environmental changes. The aim of this paper was assessing whether species distribution models can allow to identify the areas most at risk of crop damages, helping to set up management strategies aimed at the mitigation of human-wildlife conflicts. We obtained data on wild boar Sus scrofa damages to crops in the Alta Murgia National Park, Southern Italy, and related them to landscape features, to identify areas where the risk of wild boar damages is highest. We used MaxEnt to build species distribution models. We identified the spatial scale at which landscape mostly affects the distribution damages, and optimized the regularization parameter of models, through an information-theoretic approach based on AIC. Wild boar damages quickly increased in the period 2007-2011; cereals and legtmaes were the crops more affected. Large areas of the park have a high risk of wild boar damages. The risk of damages was related to low cover of urban areas or olive grows, intermediate values of forest cover, and high values of shrubland cover within a 2-km radius. Temporally independent validation data demonstrated that models can successfully predict damages in the future. Species distribution models can accurately identify the areas most at risk of wildlife damages, as models calibrated on data collected during only a subset of years correctly predicted damages in the subsequent year [Current Zoology 60 （2）： 170-179, 2014].     

An integrated study of the temporal and spatial variation in the supply of propagules, recruitment and assemblages of intertidal macroalgae on a wave-exposed rocky coast, Victoria, Australia

Recruitment is known to influence distributions and abundances of benthic marine organisms. It is therefore important to document patterns of variability in recruitment and how these relate to patterns in established assemblages. This study provides an integrated assessment of the temporal and spatial variation in supply and recruitment of propagules and established populations of several macroalgae. Propagules in water samples from two stages of the incoming tide, recruitment to artificial substrata and percentage cover of species established on the shore were recorded every 2 months from December 1994 to October 1995, in two zones of an intertidal, wave-exposed rocky shore. Variability in recruitment was measured at three spatial scales: 10s cm, 100s cm and 100s m. Availability and recruitment of most taxa were greatest between April and August, although many species had available propagules and recruited throughout the year. Temporal variation in the established assemblages was, however, more species-specific. Differences in established assemblages between zones were reflected in differences in availability and recruitment of propagules between zones. Recruitment could not be predicted directly from supply of propagules, but the two processes were linked. For most species, the greatest variation in recruitment occurred at the smallest spatial scale of 10s cm, although there was also considerable large-scale (between site) variation in recruitment of several species. Results indicate that while pre-and post-settlement mortality are likely to influence macroalgal distribution and abundance, the temporal and spatial variability in supply and recruitment of propagules can explain much of the patchiness in macroalgal assemblages.     

Within-tree distribution of nest sites and foraging areas of ants on canopy trees in a tropical rainforest in Borneo

It has been argued that canopy trees in tropical rainforests harbor species-rich ant assemblages; however, how ants partition the space on trees has not been adequately elucidated. Therefore, we investigated within-tree distributions of nest sites and foraging areas of individual ant colonies on canopy trees in a tropical lowland rainforest in Southeast Asia. The species diversity and colony abundance of ants were both significantly greater in crowns than on trunks. The concentration of ant species and colonies in the tree crown seemed to be associated with greater variation in nest cavity type in the crown, compared to the trunk. For ants nesting on canopy trees, the numbers of colonies and species were both higher for ants foraging only during the daytime than for those foraging at night. Similarly, for ants foraging on canopy trees, both values were higher for ants foraging only during the daytime than for those foraging at night. For most ant colonies nesting on canopy trees, foraging areas were limited to nearby nests and within the same type of microhabitat (within-tree position). All ants foraging on canopy trees in the daytime nested on canopy trees, whereas some ants foraging on the canopy trees at night nested on the ground. These results suggest that spatial partitioning by ant assemblages on canopy trees in tropical rainforests is affected by microenvironmental heterogeneity generated by three-dimensional structures (e.g., trees, epiphytes, lianas, and aerial soils) in the crowns of canopy trees. Furthermore, ant diversity appears to be enriched by both temporal (diel) and fine-scale spatial partitioning of foraging activity.     

基于移动窗口法的豫西山地丘陵地区景观异质性分析

研究典型区域景观异质性过程中,对特征尺度的判断尤为重要。基于3S技术,以豫西山地丘陵地区巩义市为研究区域,在分析其景观组分与结构的基础上,采用半变异函数和移动窗口相结合的方法,确定研究景观异质性的特征尺度,并在特征尺度下选取西北—东南方向和东北—西南方向两条样线,分析研究区不同干扰背景下景观异质性的空间特征。结果表明:豫西巩义地区总体上以旱地、建设用地、水浇地、草地和有林地景观类型为主,其中旱地所占比例最大(30.9%),沟渠所占比例最小(0.1%);根据特征尺度分析确定研究区巩义市景观异质性的合适尺度为1000 m;在特征尺度下,研究区景观破碎化以河谷平原和丘陵为主的巩义东部偏南区域最高,以人为干扰较少的南部低山有林地区最低,景观多样性分布特征则呈现4个聚集中心,分别为北部河谷平原农业区、城市建成区、南部低山区和东南丘陵区;不同干扰背景下,巩义地区景观异质性根据城市化程度呈现以市区为中心向外辐射发展的特征,同时受海拔高度因素影响较大,即在海拔200 m以下区域景观受人为干扰强烈,海拔200—500 m丘陵区域受海拔因子和人为干扰因子共同作用,海拔500 m以上区域海拔因子起主导作用。研究结果可为豫西山地丘陵地区及同类地区景观异质性的研究尺度、景观格局优化和土地的有效管理提供依据。     

Factors and mechanisms that explain coexistence in a Mediterranean carnivore assemblage: An integrated study based on camera trapping and diet

To promote management and conservation, it is useful to identify the factors that determine species distribution and to understand the mechanisms that regulate the organization of species assemblages or influence the dynamics of communities. Using information provided by 842 camera-trap photos and 8175 scats, we studied the factors that favour the coexistence of European badgers (Meles meles), red foxes (Vulpes vulpes) and stone martens (Martes foina) in a Mediterranean, agroforestry environment in the Iberian Peninsula. With extensive, simultaneous occupation of the space, and simultaneous activity during a broad time period (basically nocturnal and crepuscular activity patterns), the carnivores displayed different strategies depending on the availability of resources. In summer when plant resources were abundant and easy to access, there was a high overlap in patterns of diet and activity, and the temporal avoidance of the superior competitor allowed joint use of the same plots. In autumn, when there were fewer resources (although still sufficient) that were harder to access, the maintenance of food overlap was compensated for by avoidance and a reduction in overlapping activity. In winter and spring, the differentiation in response behaviour was evident in the partial substitution of plant resources.Differentiation in niche dimensions has been linked to complementarity, the differential needs and capacities of each species, and their biology. Differentiation in response behaviour was compatible with the hierarchical structure of the carnivores: European badger; red fox; stone marten. Knowledge of these factors and mechanisms increases our understanding and can help in the prediction of responses to disturbances. Consequently, it helps to improve management and conservation actions.     

Reconstructing shifts in vital rates driven by long‐term environmental change: a new demographic method based on readily available data

Frequently, vital rates are driven by directional, long‐term environmental changes. Many of these are of great importance, such as land degradation, climate change, and succession. Traditional demographic methods assume a constant or stationary environment, and thus are inappropriate to analyze populations subject to these changes. They also require repeat surveys of the individuals as change unfolds. Methods for reconstructing such lengthy processes are needed. We present a model that, based on a time series of population size structures and densities, reconstructs the impact of directional environmental changes on vital rates. The model uses integral projection models and maximum likelihood to identify the rates that best reconstructs the time series. The procedure was validated with artificial and real data. The former involved simulated species with widely different demographic behaviors. The latter used a chronosequence of populations of an endangered cactus subject to increasing anthropogenic disturbance. In our simulations, the vital rates and their change were always reconstructed accurately. Nevertheless, the model frequently produced alternative results. The use of coarse knowledge of the species' biology (whether vital rates increase or decrease with size or their plausible values) allowed the correct rates to be identified with a 90% success rate. With real data, the model correctly reconstructed the effects of disturbance on vital rates. These effects were previously known from two populations for which demographic data were available. Our procedure seems robust, as the data violated several of the model's assumptions. Thus, time series of size structures and densities contain the necessary information to reconstruct changing vital rates. However, additional biological knowledge may be required to provide reliable results. Because time series of size structures and densities are available for many species or can be rapidly generated, our model can contribute to understand populations that face highly pressing environmental problems.     

基于生态安全格局的厦漳泉地区国土空间生态保护修复区与预警点识别

厦漳泉地区是福建省开展生态保护修复的关键区域,识别、预警国土空间生态薄弱区对实施国土空间生态修复具有重要意义。研究通过MSPA、MCR等模型方法识别2000-2018年动态稳定性与连通性兼具的生态源地,提取生态廊道、生态节点等构建该地区的生态安全格局,采用FLUS模型在生态安全格局限制下模拟2030年土地利用变化,综合划分厦漳泉地区国土空间生态保护修复区并展开预警。结果表明,厦漳泉地区生态安全格局由12个生态源地,66条潜在生态廊道、13条重要生态廊道与若干生态节点等构成,生态源地主要分布在研究区西部,生态廊道为纵横交错的网状结构,部分生境较脆弱的县（区）无生态源地与廊道分布,生态节点集聚特征显著;2030年研究区耕地、林地面积呈减少趋势,建设用地面积增幅显著,建设用地向四周的耕地与林地呈环状扩张,挤压生态空间,威胁生态源地与廊道。综上,研究划分了1个生态源地保护带、2个生态修复核心区,并明确生态保护空间预警点,可为完善国土空间生态安全格局的保护与建设等提供基础信息,对开展生态保护修复协同治理、提升区域生态环境质量与人民福祉有重要意义。