Searching strategy of the painted turtle Chrysemys picta across spatial scales

Summary1. Numerous interacting abiotic and biotic factors influence niche use and assemblage structure of freshwater fishes, but the strength of each factor changes with spatial scale. Few studies have examined the role of interspecific competition in structuring stream fish assemblages across spatial scales. We used field and laboratory approaches to examine microhabitat partitioning and the effect of interspecific competition on microhabitat use in two sympatric stream fishes (Galaxias‘southern’ and Galaxias gollumoides) at large (among streams and among sites within streams) and small (within artificial stream channels) spatial scales.2. Diurnal microhabitat partitioning and interspecific competition at large spatial scales were analysed among three sympatry streams (streams with allotopic and syntopic sites; three separate catchments) and four allopatry streams (streams with only allotopic sites; two separate catchments). Electro‐fishing was used to sample habitat use of fishes at 30 random points within each site by quantifying four variables for each individual: water velocity, depth, distance to nearest cover and substratum size. Habitat availability was then quantified for each site by measuring those variables at each of 50 random points. Diet and stable isotope partitioning was analysed from syntopic sites only. Diel cycles of microhabitat use and interspecific competition at small spatial scales were examined by monitoring water velocity use over 48 h in artificial stream channels for three treatments: (i) allopatric G. ‘southern’ (10 G. ‘southern’); (ii) allopatric G. gollumoides (10 G. gollumoides) and (iii) sympatry (five individuals of each species).3. One hundred and ninety‐four G. ‘southern’ and 239 G. gollumoides were sampled across all seven streams, and habitat availability between the two species was similar among all sites. Galaxias‘southern’ utilised faster water velocities than G. gollumoides in both the field and in channel experiments. Both species utilised faster water velocities in channels at night than during the day. Diet differences were observed and were supported by isotopic differences (two of three sites). No interspecific differences were observed for the other three microhabitat variables in the field, and multivariate habitat selection did not differ between species. Interspecific competition had no effect on microhabitat use of either species against any variable either in the field (large scale) or in channels (small scale).4. The results suggest that niche partitioning occurs along a subset of microhabitat variables (water velocity use and diet). Interspecific competition does not appear to be a major biotic factor controlling microhabitat use by these sympatric taxa at any spatial scale. The results further suggest that stream fish assemblages are not primarily structured by biotic factors, reinforcing other studies de‐emphasising interspecific competition.

Soil leakage in karst areas is an important geomorphic agent of environmental interest. There are several viewpoints concerning soil leakage ratios. One viewpoint states that the soil leakage ratio is high in karst regions, whereas others consider that it is very low. This paper’s objective is to describe the soil leakage phenomena qualitatively and quantitatively in the Chongqing Karst, China, by conventional methods such as monitoring runoff plots and paint traces drawn on piles and walls found within runoff plots, and by measuring the activity of the isotope 137Cs at small, medium, and large spatial scales. This paper’s results show that soil-filled karst cracks occurred at a small spatial scale with soil leakage ratios ranging from about 3% to about 34% at two abandoned quarries and six soil profiles with rock (karst) crack development. The soil leakage ratio was almost zero at the medium spatial scale. The soil leakage ratio was 4.50% and the surface-soil erosion ratio was 95.50% of the total soil erosion at the large spatial scale. It is concluded that soil leakage ratios in the study area were low at a large spatial scale, and that cracks in karst were filled with soil at small spatial scales. This paper’s results indicate that soil leakage phenomena vary depending on the processes acting at the small, medium, and large spatial scales.

Increasing urbanization poses significant challenges to the mental health of urban populations. Urban green spaces are known to support mental well-being by reducing stress, promoting physical activity, and fostering social interaction. However, empirical evidence on the relationship between green infrastructure and mental health remains inconsistent, partly due to methodological differences, study area characteristics and spatial scales. In selected districts of two German cities, a random sample was drawn from the local population registers, with 2,157 residents providing georeferenced residential data for the analysis. The association between greenness, measured by the Normalized Difference Vegetation Index (NDVI), and mental wellbeing, assessed using the WHO-5 Well-Being Index (WHO-5), was examined at neighbourhood level across different spatial scales. Sociodemographic factors such as gender, age, and monthly net household income were included. The mean WHO-5 score in the sample was 14.52 (SD: 4.78). NDVI values typically ranged from around 0.17 at small scales (10-25 m) to around 0.28 at larger scales (700-1,000 m). A significant association was found between NDVI and WHO-5 at small spatial scales (β = 2.97 at 10 m; β = 2.42 at 25 m) and again at larger scales (β = 2.18 at 700 m; β = 3.26 at 1,000 m), but no significant associations were observed at intermediate spatial scales (50-600 meters), with coefficients ranging from 0.30 to 1.72 and no consistent pattern. This suggests a U-shaped relationship between spatial scale and effect strength. The results indicate that while the NDVI and sociodemographic data provides valuable insights, they do not fully capture the complexity of human-environment interactions. Future studies should consider incorporating qualitative data, such as individual experiences and perceptions of green space quality, to deepen the understanding of the relationship between green infrastructure and mental health. Key messages • Mental well-being is linked to greenness at very small and large spatial scales, showing a U-shaped relationship. • Combining NDVI with additional variables provides a more comprehensive understanding of the impact of green spaces on mental well-being.

Seasonal and ontogenetic patterns of habitat use in coral reef fish juveniles

We questioned the different interpretations of ecological sexual segregation from a novel perspective, i.e., by carrying out diverse temporal and spatial scale analyses within a long-term study (1984–2003). Thus we combined spatial (small/large) and temporal (small/large) scale analyses to identify the factors generating sexual segregation in fallow deer in San Rossore, Italy. The study site was divided into an eastern sector characterized by human disturbance (DS) and a western undisturbed sector (US). According to census data, human presence increased in DS from 1984, and while females gradually abandoned it, males remained—thus supporting the predation risk hypothesis (large spatial and temporal scale)—and actually increased their presence in DS, where they seemingly benefited from a lower female density. This supported the indirect competition hypothesis. The analysis of data on a large temporal and small spatial scale confirmed that intersexual competition, in particular for grass, was higher in a crowded pasture in US. Observations by means of radio-telemetry of 23 adult females and 25 adult males (1997–2001, reduced temporal and large spatial scale) showed that large scale segregation was relevant during the day and disappeared at night, when disturbance was absent and also the females reached DS. This also supported the predation risk hypothesis. Moreover, sexes showed different habitat choices inside DS at night, thus supporting the forage selection hypothesis (small spatial and temporal scale). In conclusion, failure to address the whole set of combinations of spatial and temporal scale analyses would have led to monocausal explanations of ecological sexual segregation.

Statewide surveys of furbearers in Illinois indicate gray (Urocyon cinereoargenteus) and red (Vulpes vulpes) foxes have experienced substantial declines in relative abundance, whereas other species such as raccoons (Procyon lotor) and coyotes (Canis latrans) have exhibited dramatic increases during the same time period. The cause of the declines of gray and red foxes has not been identified, and the current status of gray foxes remains uncertain. Therefore, I conducted a large-scale predator survey and tracked radiocollared gray foxes from 2004 to 2007 in order to determine the distribution, survival, cause-specific mortality sources and land cover associations of gray foxes in an urbanized region of northeastern Illinois, and examined the relationships between the occurrence of gray fox and the presence other species of mesopredators, specifically coyotes and raccoons. Although generalist mesopredators are common and can reach high densities in many urban areas their urban ecology is poorly understood due to their secretive nature and wariness of humans. Understanding how mesopredators utilize urbanized landscapes can be useful in the management and control of disease outbreaks, mitigation of nuisance wildlife issues, and gaining insight into how mesopredators shape wildlife communities in highly fragmented areas. I examined habitat associations of raccoons, opossums (Didelphis virginiana), domestic cats (Felis catus), coyotes, foxes (gray and red), and striped skunks (Mephitis mephitis) at multiple spatial scales in an urban environment. Gray fox occurrence was rare and widely dispersed, and survival estimates were similar to other studies. Gray fox occurrence was negatively associated with natural and semi-natural land cover types. Fox home range size increased with increasing urban development suggesting that foxes may be negatively influenced by urbanization. Gray fox occurrence was not associated with coyote or raccoon presence. However, spatial avoidance and mortality due to coyote predation was documented and disease was a major mortality source for foxes. The declining relative abundance of gray fox in Illinois is likely a result of a combination of factors. Assessment of habitat associations indicated that urban mesopredators, particularly coyotes and foxes, perceived the landscape as relatively homogeneous and that urban mesopredators interacted with the environment at scales larger than that accommodated by remnant habitat patches. Coyote and fox presence was found to be associated with a high degree of urban development at large and intermediate spatial scales. However, at a small spatial scale fox presence was associated with high density urban land cover whereas coyote presence was associated with urban development with increased forest cover. Urban habitats can offer a diversity of prey items and anthropogenic resources and natural land cover could offer coyotes daytime resting opportunities in urban areas where they may not be as tolerated as smaller foxes. Raccoons and opossums were found to utilize moderately developed landscapes with interspersed natural and semi-natural land covers at a large spatial scale, which may facilitate dispersal movements. At intermediate and small spatial scales, both species were found to utilize areas that were moderately developed and included forested land cover. These results indicated that raccoons and opossums used natural areas in proximity to anthropogenic resources. At a large spatial scale, skunk presence was associated with highly developed landscapes with interspersed natural and semi-natural land covers. This may indicate that skunks perceived the urban matrix as more homogeneous than raccoons or opossums. At an intermediate spatial scale skunks were associated with moderate levels of development and increased forest cover, which indicated that they might utilize natural land cover in proximity to human-dominated land cover. At the smallest spatial scale skunk presence was associated with forested land cover surrounded by a suburban matrix. Compared to raccoons and opossums, skunks may not be tolerated in close proximity to human development in urban areas. Domestic cat presence was positively associated with increasingly urbanized and less diverse landscapes with decreased amounts of forest and urban open space at the largest spatial scale. At an intermediate spatial scale, cat presence was associated with a moderate degree of urban development characterized by increased forest cover, and at a small spatial scale cat presence was associated with a high degree of urbanization. Free-ranging domestic cats are often associated with human-dominated landscapes and likely utilize remnant natural habitat patches for hunting purposes, which may have implications for native predator and prey species existing in fragmented habitat patches in proximity to human development.

We have developed a new persistent scatterer interferometry (dual-scale PSI) method with a simpler and more robust phase component inversion than that of the iterative linear modeling used in many commercial and scientific PSI solutions. The new method can measure displacements down to a millimetre, also for smaller interferometric stacks (~20 scenes) and strongly nonlinear motion histories. A key feature is a split of the phase signal into small and large spatial scale contributions. This is carried out via a priori creation of a “pseudo-atmospheric” stack using a strong nonlinear filter at the large spatial scale of about five times the atmospheric correlation length (~15 km). We assume the external digital elevation model used for initial flattening unbiased at the large spatial scale. The true atmospheric phase can then be separated from the large-scale surface displacement through temporal low-pass filtering. We estimate and subtract the height error from the small spatial scale phase component assuming only piece-wise “smoothness” of the displacement time series. The result is the (model-free) nonlinear displacement at small spatial scale. The simplicity of the method allows fast, automated throughput of stacks consisting of full-sized scenes; a single iteration is usually sufficient to achieve reliable results. We demonstrate the performance on a RADARSAT-1 stack over Los Angeles and compare with global positioning system (GPS) records.

Many scholars have attempted to identify the role of deterministic and stochastic processes in community assembly, but there is no consensus on which processes dominate and at what spatial scales they occur. To shed light on this issue, we tested two non-exclusive processes, scale-dependent hypotheses: (i) that limiting similarity dominates on small spatial scales; and (ii) that environmental filtering does so on a large scale. To achieve this, we studied the functional patterns of dry evergreen Afromontane forest communities along elevation gradients in southeastern Ethiopia using floristic and functional trait data from fifty-four 0.04 ha plots. We found evidence of functional overdispersion on small spatial scales, and functional clustering on large spatial scales. The observed clustering pattern, consistent with an environmental filtering process, was most evident when environmental differences between a pair of plots were maximized. To strengthen the link between the observed community functioning pattern and the underlying process of environmental filtering, we demonstrated differences in the topographical factors of the most abundant species found at lower and higher elevations and examined whether their abundance varied over time or changed with time along the elevation. We found (i) that the largest functional differences in the community (observed between lower and upper dry evergreen Afromontane forest assemblages) were primarily the result of strong topographical influence; and (ii) that the abundance of such species varied along the elevation gradient. Variation in stand structure and tree species diversity within the DAF plots shows that topography is among the important drivers of local species distribution and hence the maintenance of tree diversity in dry Afromontane forest. Our results support the conclusion that environmental filtering at large spatial scales is the primary mechanism for community merging, since functional grouping pattern was associated with species similarities in topographic variation, ultimately leading to changes in species abundances along the gradient. There was also evidence of competitive exclusion at more homogeneous and smaller spatial scales, where plant species compete effectively for resources.

**Abstract:** Breeding at the right place is essential for seabirds to ensure a compromise between access to the resources, being safe from predation and deal with local weather. A challenge in ecology is to predict the demographic responses of populations in a context of climate change. Understanding demographic differences between multiple populations or colonies is central to determining some of the underlying mechanisms that drive these responses. Variability in population responses occur at large spatial scales, and studies have already shown different demographic strategies between several sites, but this understanding remains fragmentary and insufficient. However, on small spatial scales, analyzes between several nearby colonies have rarely been conducted, neglecting direct weather effects of other local effects. Here, we estimated the demographic parameters between several seabird colonies at different spatial scales and then assessed the differences in the demographic responses of these populations to environmental variations. We used individual monitoring data from three nearby colonies of snow petrel to investigate small-scale differences. To investigate the large-scale differences, we used two distant populations of closely related marine predators with similar ecological requirements, the south polar skua and the brown skua. Using capture-mark-recapture models, we estimated the survival and reproductive performance of each species at different sites. Our results show that breeding performance can vary both on large and small spatial scales. In addition, for snow petrels, local weather conditions may affect colonies differently resulting in different demographic responses. Very few studies have taken into account spatial heterogeneity when studying seabird population responses and generally make inferences from a single study site. To draw general conclusions about these responses, it is necessary to study in more detail, on several sites, a greater number of species in marine ecosystems. **Authors:** Christophe Sauser¹, Nathan Pacoureau², Karine Delord¹, Christophe Barbraud¹ ¹CNRS - Centre d'étude biologique de Chizé, ²Simon Fraser University

Relationship between species richness of small mammals and primary productivity of arid and semi-arid grasslands in north China

Summary1. The aquatic snailValvata utahensis(Gastropoda: Valvatidae) is a federally endangered aquatic mollusk known only from the Snake River in southern Idaho, U.S.A. The Snake River, like many other large river systems in the western United States, has undergone substantial anthropogenic modifications in recent history that have altered water flows, changed physicochemical attributes of the water and produced an overall spatially fragmented aquatic system.2. Because little is currently known about the basic biology and life history ofV. utahensis, we conducted a detailed genetic analysis of amplified fragment length polymorphism (AFLP) and mitochondrial DNA sequence variation in this species from six locations along the Snake River. This study was designed to discern (i) levels of within‐location genetic diversity, (ii) patterns of genetic structure at small spatial scales (i.e. within sampling locations) and (iii) patterns of genetic structure at large spatial scales (among sampling locations).3. We show that comparable levels of nuclear genetic variation exist within each of the six locations examined. However, reduced mitochondrial sequence diversity was observed at Thousand Springs compared with the other locations examined.4. We further illustrate thatV. utahensisshows no genetic structure within locations over relatively small physical distances up to approximately 3 km. We suggest that active dispersal of individuals via crawling and passive dispersal because of downstream displacement or floating behaviours may have produced this pattern. However, at large spatial scales genetic structure generally followed an isolation‐by‐distance pattern. This pattern was not directly correlated with the connectivity of locations through the river corridor and suggested the possible role of episodic passive dispersal via avian waterfowl or the effects of historical floods throughout the Snake Riverc.14 000 years ago.

The mortality rates of a pomacentrid Acanthochromis polyacanthus were examined in relation to the abundance of large predatory fish (>200 mm total length, TL) at two spatial scales. Survivorship was negatively related to patterns of predator abundance at a large spatial scale (hundreds of metres) over 3 yr, but not at a small spatial scale (tens of metres) over 2 yr. On the large scale, mortality was consistently greater (14 to 30%) in locations where there were greater numbers of predators, and lower in locations where predators occurred in smaller numbers. Among these locations, spatial differences in rank abundance of surviving juveniles were primarily due to mortality, whereas temporal differences in rank abundance were primarily due to initial juvenile abundance. These data suggest that impacts of large predatory fish were likely to have been greater in space than time and at the large spatial scale than the small spatial scale.

ABSTRACTWe investigated the distribution of common murres, Uria aalge, and shearwaters, Puffinus griseus and P. tenuirostris, relative to their fish prey at two spatial scales, one of hundreds of kilometres and the other of kilometres. Data on oceanographic conditions, the distribution of sea birds and the distribution of fish in the upper water column were collected during three research surveys off Vancouver Island (British Columbia, Canada). At the large spatial scale, we found that both murres and shearwaters were more abundant inshore than offshore of the shelf break and that their fish prey were likewise more abundant in the inshore habitat. At the smaller scale, we investigated the relative importance of fronts and fish density. In contrast to what we expected based on our finding at the large spatial scale, there was a significant negative relationship between fish and both murre and shearwater density. We found that fronts, independent of fish density, did not have an effect on small‐scale murre density and had only a weak effect on small‐scale shearwater density. We suggest that the negative relationship between fish and sea bird density at the scale of kilometres may have been due to fish diving to escape foraging sea birds and thus avoiding capture in the near‐surface trawl used in this study. If this avoidance behaviour is common in pelagic fish, then sea birds may affect fish populations by driving fish away from plankton‐rich surface waters and thus negatively affecting the feeding and growth rates of their fish prey.

Aims Anthropogenic activities have drastically increased nutrient availability, resulting in declines in species richness in many plant communities. However, most previous studies have explored only species-loss patterns and mechanisms over small sampling areas, so their results might overestimate species loss at larger spatial scales. The aim of this research was to explore species diversity change patterns and speciesloss rates at multiple scales in alpine meadow communities following nutrient enrichment. Specifically, we asked two closely related questions: (i) do changes in species diversity and species-loss patterns differ among spatial scales? and (ii) how does community compositional dissimilarity and species turnover change among spatial scale? Methods This study was implemented in an alpine meadow community, which is regarded as one of the most sensitive and vulnerable terrestrial ecosystems to anthropogenic nutrient enrichment. We conducted a fertilization experiment that involved the addition of nitrogen (N), phosphorus (P) and a mixture of both to a series of quadrats ranging from 1 to 16 m~2 over 5 years to study the variations in the patterns of species diversity in response to nutrient additions at different spatial scales. Important Findings Our results showed that the changes in species diversity and species loss were dependent on the type of fertilization and the spatial scale. After N and NP fertilization, species diversity significantly decreased at the small scale but not at the large scale, and the rate of species loss decreased as the spatial scale increased. In contrast, the differences between the P addition and control communities were negligible at both the small and large spatial scales. N fertilization caused species to be lost from the small sampling scale, but because different species were lost from different samples, there was an increase in compositional dissimilarity at larger spatial scales, which reduced the total number of species lost when measured at larger scales. These findings highlight spatial scale in evaluating the biodiversity loss after fertilization and suggest that the compositional dissimilarity might play an important role in mediating species loss after fertilization. Our study significantly improved our understanding of changes in species diversity and species loss at different spatial scales under nutrient-enrichment scenarios.

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 215:69-77 (2001) - doi:10.3354/meps215069 Measuring b-diversity using a taxonomic similarity index, and its relation to spatial scale C. Izsak, A. R. G. Price* Ecology and Epidemiology Group, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom *Corresponding author. E-mail: andrew.price@warwick.ac.uk ABSTRACT: We present a new similarity index, taxonomic similarity (ΔS), which can be used to measure β-diversity. ΔS utilises species presence/absence data, and incorporates both higher taxon richness and evenness concepts. It is derived from the average taxonomic distance (relatedness) of any 2 species from different sites. Therefore ΔS is analogous to taxonomic distinctness recently developed for biodiversity assessment at α- and γ - (landscape or seascape) scales. ΔS is a new index, although its derivation uses a concept similar to the Œoptimal taxonomic mapping statistic¹ developed independently for quantifying structural redundancy in marine macrobenthos. Using echinoderm data, we show that ΔS exhibits smoother behaviour and is less influenced by species richness, and hence sampling effort, than the widely used Jaccard coefficient of species similarity. We also believe ΔS to be a more intuitive and comprehensive measure of similarity than Jaccard and other conventional indices based solely on species held in common. Taxonomic similarity between sites is computed for echinoderms examined over 3 different spatial scales: local/small-scale (<10 km), intermediate-scale (10 to 100s km) and province/oceanic-scale (100s to 1000s km). Taxonomic similarity between sites increases progressively with spatial scale, with significantly lower values and higher β-diversity at small spatial scales. The same pattern is evident for species similarity, using the Jaccard coefficient. Possible explanations for this pattern centre on: (1) the large-scale oceanic area examined (Indo-West Pacific), representing a metapopulation of echinoderms for the 2 other, smaller areas examined within (Pula Wé, Sumatra and Lakshadweeps); (2) greater biophysical instability and unpredictability at small spatial scales. Compared with larger spatial scales, these may be characterised by greater likelihood and influence of species migrations and extinctions on a site¹s total species composition. Hence, species composition may be highly changeable at small scales, leading to high β-diversity. These findings are based on 1 set of comparative data for 1 faunal group. Any wider conclusions drawn would be premature, although corals may also show greater β-diversity at small spatial scales. The extent to which patterns observed are evident for other marine species groups is not well known. KEY WORDS: Biodiversity · β-diversity · Taxonomic similarity · Echinoderms · Indo-West Pacific Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 215. Online publication date: May 31, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.