Habitat Units Research Articles

Microscale hydrodynamics and coherent flow structures in rivers: Implications for the characterization of physical habitat

AbstractTechniques for the rapid appraisal and documentation of water resources and habitat are increasingly utilized in a variety of legislative compliance situations and environmental management/design projects. Within river survey, the ‘physical biotope’ (i.e. riffles, runs, pools, glides) has been advocated as the basic unit of river habitat and an appropriate focus for stream reconnaissance and habitat assessments at the mesoscale of river systems. To date, however, much research into the hydraulic characterization of physical biotopes has focused on spatially‐ and temporally averaged velocity and depth measures, overlooking more detailed hydraulic parameters and variation at microscales, which may have more direct influences on the survival of individual organisms. This paper outlines the methodology, analytical techniques and initial results of a microscale exploration of the hydraulics of physical biotopes through the analysis of a range of turbulence properties. Results of the analyses offer both detailed descriptions of hydraulic habitat provided by the biotopes studied (related to various mechanisms of turbulence generation), as well as an indication of levels of ‘within‐biotope’ heterogeneity which gives rise to a conceptual classification. A continuum of increasing habitat complexity is observed from glide, to riffle, to pool biotopes, associated with the generation of turbulence and organization of flow structures and with the level of ‘internal’ spatial and temporal hydraulic heterogeneity. Physical biotope characterization approached in this way may offer a more robust and transferable classification compared to mesoscale methods, particularly if levels of within‐biotope heterogeneity are treated as an additional biotope characteristic. Copyright © 2008 John Wiley & Sons, Ltd.

Structure and Spatial‐Temporal Dynamics of Chironomidae Fauna (Diptera) in Upland and Lowland Fluvial Habitats of the Chocancharava River Basin (Argentina)

AbstractStructure of benthic Chironomidae assemblages and their spatial‐temporal dynamic were analyzed in upland and lowland habitats from the Chocancharava River basin (Córdoba, Argentina). Sampling was performed in three tributary streams and in three lowland reaches of the river during high and low rainfall periods. Characteristic taxa of upland and lowland reaches and of the different habitats in these reaches were identified using the IndVal method. Chironomidae assemblages were different between upland and lowland reaches and among habitats in each reach, as assessed by Multiresponse Permutation Procedure and Canonical Correspondence Analyses. Substrate type and current velocity were the major explanatory variables structuring the assemblages in upland reaches whereas in lowland reaches current velocity and aquatic vegetation were the most important variables. The highest richness was found in the most complex habitat units in both upland and lowland stretches as assessed by Analyses of Variance. Chironomidae larvae responded to longitudinal changes of hydraulic variables and to local variations of fluvial habitats at different reaches. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Scales of variation of gastropod densities over multiple spatial scales: comparison of common and rare species

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 354:147-160 (2008) - DOI: https://doi.org/10.3354/meps07205 Scales of variation of gastropod densities over multiple spatial scales: comparison of common and rare species M. G. Chapman*, A. J. Underwood Centre for Research on Ecological Impacts of Coastal Cities, Marine Ecology Laboratories A11, University of Sydney, New South Wales 2006, Australia *Email: gee@bio.usyd.edu.au ABSTRACT: Quantifying spatial variation of populations of animals and plants is fundamental to understanding the relative importance of different ecological processes that influence them. Small-scale patterns in marine invertebrate densities are often thought to be determined by organisms’ responses to very localized cues, e.g. quality of habitat or food. In contrast, large-scale patterns have often been attributed to much larger-scale processes, such as availability of larvae, wave-action or upwelling. However, if features of habitat (which primarily influence populations at a small scale) vary over larger spatial scales, population variation over these larger scales may be due entirely to local responses to habitat occurring at a small scale. This study used artificial units of habitat (AUHs) to standardize features of habitat, in order to measure rates of colonization of subtidal gastropods at scales of 20 cm to 4 km. Patterns were compared for 8 common and 6 rare species, in addition to the assemblage of gastropods. Many of the species that colonized these AUHs were found in similar densities to those in natural habitats. Despite the standardisation of habitat, all species showed small-scale differentiation among AUHs only 20 cm apart, again mimicking patterns in natural patches of habitat. This was most probably due to choices of whether to colonize or not, rather than passive colonization forced by local environmental factors, because different species showed different patterns of colonization among AUHs. There was little additional variation in numbers across scales from 1 m to 4 km. The rare species showed greater small-scale and less large-scale variation than did the common species, but species in each group did not show similar patterns among individual AUHs. Where there are infrequent sample units that have large numbers of individuals (or species), they affect means at larger scales, causing larger-scale variation. Understanding small-scale responses to habitat must underpin studies of broad-scale patterns, so that changes in local processes having influences over large scales can be differentiated from broad-scale processes. This also has large implications for assessments of environmental impacts and monitoring of biodiversity, two of the most important tasks for ecologists in the immediate future. KEY WORDS: Artificial habitat · Gastropoda · Patchiness · Spatial scales · Variation Full text in pdf format PreviousNextCite this article as: Chapman MG, Underwood AJ (2008) Scales of variation of gastropod densities over multiple spatial scales: comparison of common and rare species. Mar Ecol Prog Ser 354:147-160. https://doi.org/10.3354/meps07205 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 354. Online publication date: February 07, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

Bayesian Spatial Modeling of Data from Unit‐Count Surveys of Fish in Streams

AbstractWe describe a framework for spatial modeling of data from surveys of stream‐dwelling fish species in which repeated counts are made of animals within a sample of habitat units. Using Bayesian modeling with Markov chain‐Monte Carlo (MCMC) algorithms, it is possible to estimate fish population size from repeated‐count survey data while allowing fish detection probabilities to vary across the stream. We propose the use of conditional autoregressive models for modeling the spatial dependence of density across the habitat units of the stream. The spatial dependence model can be used along with covariate models for density and detection to predict density at unsampled units and thereby estimate total abundance across the stream. We apply these models to data sampled from an intensive repeated‐count survey of juvenile coho salmon Oncorhynchus kisutch in McGarvey Creek, Northern California. Spatial dependence in fish density was detected, and models that account for spatial dependence produced more precise predictions at unsurveyed units, and thus more precise estimates of total stream abundance, than models that assumed spatial independence. Through a small simulation study, we show that ignoring heterogeneity in detection probabilities can lead to significant underestimation of total abundance. Inclusion of heterogeneity by means of a random effect in the detection component of the model can lead to numerical instability of the MCMC method, and we stress the importance of accounting for heterogeneity by incorporating covariates in modeling detection probability.

Complexity in the relationship between matrix composition and inter-patch distance in fragmented habitats

The connectivity of fragmented landscapes is a function of the physical distance between suitable habitats and the characteristics of the habitat through which the animal is moving, i.e. the matrix. Experimental manipulations done to explain how spatial arrangement and composition of habitats affects biota remain scarce, particularly in marine systems. Holdfasts of the common kelp, Ecklonia radiata, are discrete units of habitat for small invertebrates (e.g. amphipods, isopods, molluscs, annelids) that can be isolated from other holdfasts by habitat, which may be less suitable (e.g. other species of algae or relatively bare space). We compared assemblages, which colonised defaunated holdfasts in experimentally created small-scale landscapes where patches of habitat (holdfasts) were distant versus close together and which had Sargassum spp. versus relatively bare space in the matrix. We also compared colonisation across matrices of crushed fucoid algae to assess whether the structural or chemical nature of algae in the matrix had the most influence on the colonisation. Assemblages in defaunted holdfasts differed between those that were close to and those that were distant from undisturbed holdfasts, where the matrix was devoid of vegetation. Where Sargassum spp. was present in the matrix, however, this difference disappeared and was possibly due to the chemical, rather than structural, characteristics of the fucoid matrix. The extent to which matrix habitat is a barrier to movement of invertebrates among holdfasts thus depends on not only how extensive it is but what type of habitat it contains. As within terrestrial systems, the nature of the matrix is also likely to be a fundamental component of the connectivity within marine systems.

Habitat Features Affect Bluehead Sucker, Flannelmouth Sucker, and Roundtail Chub across a Headwater Tributary System in the Colorado River Basin

ABSTRACT We assessed the distributions of three species of conservation concern, bluehead sucker (Catostomus discobolus), flannelmouth sucker (Catostomus latipinnis), and roundtail chub (Gila robusta), relative to habitat features across a headwater tributary system of the Colorado River basin in Wyoming. We studied the upper Muddy Creek watershed, Carbon County, portions of which experience intermittent flows during late summer and early fall. Fish and habitat were sampled from 57 randomly-selected, 200-m reaches and 416 habitat units (i.e., pools, glides, or runs) during the summer and fall of 2003 and 2004. Among reaches, the occurrences of adults and juveniles of all three species were positively related to mean wetted width and the surface area of pool habitat, and the occurrences of adult bluehead sucker and roundtail chub were also positively related to the abundance of rock substrate. Only juvenile bluehead sucker appeared to be negatively influenced by the proportion of a reach that was dry at the time of sampling. Within individual pools, glides, and runs, the occurrences of adults and juveniles of all three species were positively related to surface area and maximum depth, and occurrences of bluehead sucker and flannelmouth sucker juveniles were more probable in pools than in glides or runs.

Models of stream habitat characteristics associated with tubificid populations in an intermountain watershed

Habitat assessments were conducted in an intermountain watershed at three spatial extents to explore ways to predict the presence of tubificid oligochaetes likely to support the parasite Myxobolus cerebralis, cause of salmonid whirling disease. Stream reaches with six different reach slope characteristics were selected using GIS. The aquatic habitat in 60 reaches selected at random was measured and classified into distinct habitat units. Within the habitat units, areas of microhabitat with depositional fine sediments were chosen, measured, and core samples were removed to characterize the sediments and benthic oligochaetes. Two tubificids, Tubifex spp. and Limnodrilus hoffmeisteri, were abundant and co-occurred in silt-clay and fine sand sediments in these habitats. Models were posed and tested to predict the presence and relative abundance of tubificids using habitat characteristics from the three spatial extents: reach, habitat unit, and microhabitat. At the reach extent, tubificids were associated with low-reach slope and with slow water habitats. Within habitat units, tubificids were associated with higher percentages of fine sediments and higher stream width:depth ratios. In microhabitat cores, the presence of silt-clay sediments was positively associated with higher average stream width:depth ratios. Since ecological relationships are often scale dependent and stream systems have a natural hierarchy, predictive habitat models such as these that use measures from several scales may help researchers and managers more efficiently identify and quantify aquatic communities at highest risk of infection by the M. cerebralis parasite.

The unpredictability of favourability: condition assessment and protected areas in England

The probability that protected areas will deliver their potential for maintaining or enhancing biodiversity is likely to be maximised if they are appropriately and effectively managed. As a result, governments and conservation agencies are devoting much attention to the management of protected areas. In the U.K., the demand for performance accountability has resulted in Public Service Agreements (PSA) that set out targets for government departments to deliver results in return for investments being made. One such target for England is to ensure that all nationally important wildlife sites are in favourable condition by 2010. Here, we tested the hypothesis, of potential strategic importance, that the ecological condition of these sites is predictable from relationships with a range of physical, environmental and demographic variables. We used binary logistic regression to investigate these relationships, using the results of English Nature’s 1997–2003 condition assessment exercise. Generally, sites in unfavourable condition tend to be larger in area, located at higher elevations, but with higher human population density and are more spatially isolated from units of the same habitat. However, despite the range of different parameters included in our models, the extent to which the condition of any given site could be predicted was low. Our results have implications for the delivery of PSA targets, funding allocation, and the location of new protected areas.

Nest selection by snow petrels Pagodroma nivea in East Antarctica : Validating predictive habitat selection models at the continental scale

Little is known on the factors controlling distribution and abundance of snow petrels in Antarctica. Studying habitat selection through modeling may provide useful information on the relationships between this species and its environment, especially relevant in a climate change context, where habitat availability may change. Validating the predictive capability of habitat selection models with independent data is a vital step in assessing the performance of such models and their potential for predicting species’ distribution in poorly documented areas. From the results of ground surveys conducted in the Casey region (2002–2003, Wilkes Land, East Antarctica), habitat selection models based on a dataset of 4000 nests were created to predict the nesting distribution of snow petrels as a function of topography and substrate. In this study, the Casey models were tested at Mawson, 3800 km away from Casey. The location and characteristics of approximately 7700 snow petrel nests were collected during ground surveys (Summer 2004–2005). Using GIS, predictive maps of nest distribution were produced for the Mawson region with the models derived from the Casey datasets and predictions were compared to the observed data. Models performance was assessed using classification matrixes and Receiver operating characteristic (ROC) curves. Overall correct classification rates for the Casey models varied from 57% to 90%. However, two geomorphologically different sub-regions (coastal islands and inland mountains) were clearly distinguished in terms of habitat selection by Casey model predictions but also by the specific variations in coefficients of terms in new models, derived from the Mawson data sets. Observed variations in the snow petrel aggregations were found to be related to local habitat availability. We discuss the applicability of various types of models (GLM, CT) and investigate the effect of scale on the prediction of snow petrel habitats. While the Casey models created with data collected at the nest scale did not perform well at Mawson due to regional variations in nest micro-characteristics, the predictive performance of models created with data compiled at a coarser scale (habitat units) was satisfactory. Substrate type was the most robust predictor of nest presence between Casey and Mawson. This study demonstrate that it is possible to predict at the large scale the presence of snow petrel nests based on simple predictors such as topography and substrate, which can be obtained from aerial photography. Such methodologies have valuable applications in the management and conservation of this top predator and associated resources and may be applied to other Antarctic, Sub-Antarctic and lower latitudes species and in a variety of habitats.

Do hydraulic units define macroinvertebrate assemblages in mountain streams of central Argentina?

Methods to assess the physical habitat provide important tools for many aspects of river management. Hydraulic units (defined as a homogeneous patch of flow type and substrate) were described in mountain streams of Central Argentina and the distribution of macrozoobenthos in these habitat units was analyzed. Four streams from the upper Carcarañá River Basin (Córdoba, Argentina) were sampled in two hydrological periods. Hydraulic units (as substrate and flow type), current velocity, depth, macrophytes and macroalgae were assessed. Three benthic samples were taken in each hydraulic unit. A total of 12 hydraulic units were registered, which varied seasonally in their proportional abundance. The highest values of taxonomic richness, total abundance, diversity and evenness were found in the low-water period. The most heterogeneous hydraulic units (characterized by substrate of diverse grain size) presented the highest richness, diversity and evenness, whereas the highest total abundance was observed in hydraulic units with homogeneous substrate, such as bedrock or gravel sand. Canonical correspondence analysis grouped samples and taxa mainly in relation to the hydraulic units, and temporal variation in macroinvertebrate assemblages was observed. We found that the interaction between hydrological and geomorphological conditions affected benthic assemblages and that their organization is important at a mesoscale. Therefore, hydraulic units may be considered important tools in assessing stream integrity in lotic systems of central Argentina.

Interactions of components of habitats alter composition and variability of assemblages

1. The nature and resources supplied by different components of habitats influence species, creating variability from place to place within a habitat. 2. Experiments were done to investigate the effects of altering components of habitats on the variability of assemblages of numerous species of intertidal gastropods. 3. Artificial habitats with three levels of structure, combining different types of turf (i.e. different densities and height of fronds) were sampled 8 weeks after deployment in the intertidal. They were rapidly colonized by up to 66 species of gastropods. 4. Independently of the types of turf combined to form different habitats, there were differences in assemblages where there was more than one type of component present. Multivariate dissimilarities among units making up each habitat were also greater where there were more than one type of unit, but there was no such difference in the variance of numbers of species per unit. 5. Altering the relative abundances of different types of components made little change to the assemblages, nor their multivariate variability among units of habitat and the variance in number of species per unit in each habitat. 6. Differences in assemblages due to the different structure of habitat are complex to interpret and simple characterizations of structure of habitat are inadequate. Comparing different habitats requires appropriate experimentation to ensure that variability within habitats is also investigated.

Application of the functional habitat concept to the regulated Lower Ord River, Western Australia, Part I, macroinvertebrate assemblages

This paper tests the applicability of the Functional Habitat Concept (FHC) to a lowland tropical river in Australia. The underlying tenet of the FHC is that in-stream hydrological and physical processes form distinct habitats, and where these habitats support distinct macroinvertebrate assemblages they are considered ‘functional’ habitats. This concept has been employed in the northern hemisphere as a tool for river restoration and management, especially where habitats are easier to manage than species, but the FHC has yet to be tested in Australia. This study reports the application of the FHC to the regulated Lower Ord River (LOR) in the remote far north of Western Australia. Seven ‘potential’ in-stream habitat units were identified on the basis of their physical properties. Multivariate and species preference analysis of macroinvertebrate data indicated that these habitats supported six distinct macroinvertebrate assemblages, providing six ‘functional’ habitats (gravel runs and rock rapids, sand margins, mud/silt margins, flooded riparian vegetation, emergent vegetation, and submerged macrophyte beds). Macroinvertebrate preferences for particular habitats reflected the broad ecology and life-history characteristics of the species, which in turn reflected the physical attributes of the habitats. We argue that in a region where the fauna has been little studied, and for which there is little ecological information, the FHC is a valuable approach. For a river that is facing increased water abstraction, the FHC potentially aids in the preservation of macroinvertebrate diversity as it identifies critical functional habitats for managers to maintain.

Landscapes and life-histories influence colonisation of polychaetes to intertidal biogenic habitats

Patches of biogenic habitats created by algae, tubeworms and bivalves are common on intertidal rocky shores and are used as habitat by many different invertebrates. Invertebrates in mosaics of different habitats must colonise different patches either by moving from an adjacent patch of a different habitat or by dispersal through the water-column. Using polychaetes as model organisms, we tested how different biogenic habitats influence patterns of colonisation to standardised units of habitat, plastic pot-scourers placed in the biogenic habitat. In general, colonisation by polychaetes was strongly influenced by the surrounding biogenic habitats; patterns of colonisation to identical patches ( i.e. scourers) differing according to their surrounding matrix. Using fences (to exclude lateral movement from the surrounding habitat) and roofs (to restrict colonisation from the water-column), different pathways of colonisation are distinguished. Due to lack of information about specific life-histories of many species of polychaetes in the Southern Hemisphere, we used 2 broad groups based on their mobility as adults ( i.e. highly mobile “Errantia” or “Sedentaria” which have limited mobility). “Errant” polychaetes colonised scourers from the water-column, but also moved in from the surrounding habitat. “Sedentary” polychaetes were unaffected by restrictions on lateral movement because they mostly entered scourers from the water-column. Differences in and changes to the distributions, presence and relative covers of these intertidal biogenic habitats can therefore have large effects on organisms living in these patchy habitats.

Colonization of novel habitat: Tests of generality of patterns in a diverse invertebrate assemblage

Understanding colonization and use of novel habitat by diverse assemblages is increasingly important as natural habitats are disturbed or replaced. How well novel habitats will be used by biota depends on (i) how well they mimic natural habitat and (ii) how adaptable are the fauna in utilizing different types of habitat. Much of our understanding of colonization of patchy habitats is derived from studies in which colonizing fauna respond strongly to biotic stimuli. Comparisons of patterns of colonization among patches, across landscapes, over time, etc., may thus be confounded by differences in the quality of the patches themselves, which may interact with other features of the broader landscape. Intertidal boulder-fields have many features that make them ideal for extending studies of colonization by diverse assemblages because the organisms living on boulders live in naturally patchy habitats, separated by a matrix which is differentially permeable to different components of this biota. This study used standardized, novel patches of habitat as surrogates of natural boulders in order to control the physical features of these patches. These units of habitat resemble quarried rock that is frequently added to nearshore environments in the form of groynes or breakwaters, or which is commonly disposed of in urbanized estuaries. Previous work has shown that they are readily colonized and used by a similar range of taxa as are natural boulders. Here, they were added to existing boulder-fields to test specific hypotheses regarding colonization of different types of patches across replicate sites, times, periods of deployment and levels of taxonomic grouping. All tests showed extremely variable colonization, with little support for more deterministic models that have been proposed to explain species–habitat relationships. Variability in colonization mimicked natural levels of variability in these fauna reported elsewhere. Colonization of novel habitats in this system seems therefore to be strongly influenced by stochastic variation in supply of colonists and their ability of colonists to utilize and move through he surrounding matrix, rather than on the quality of habitat itself. This needs careful consideration in attempts to manage or repair damaged marine habitats.

Towards an ecologically meaningful classification of the flow biotope for river inventory, rehabilitation, design and appraisal purposes

Recent research into the physical and ecological status of rivers has focused upon rapid field-based assessments of mesoscale habitat features in order to satisfy international regulatory requirements for habitat inventory and appraisal. Despite the low cost and time efficient nature of rapid field surveys, the robustness of such techniques remains uncertain. This paper uses data from over 4000 surveyed UK river reaches in the UK River Habitat Survey (RHS) database in order to seek linkages between surface flow conditions (flow biotopes), local channel morphology (physical biotopes) and biologically distinct vegetative and minerogenic habitat units (functional habitats). Attempts to identify one-to-one connections between surface flow types, units of channel morphology and functional habitats oversimplify a complex and dynamic hydraulic environment. Instead, a nested hierarchy of reach-scale physical and ecological habitat structures exists, characterised by transferable assemblages of habitat units. Five flow biotopes show strong correlations with functional habitats, and differing combinations of three of these account for over 60% of the distribution for all functional habitats. On this basis, a classification of environments for ecological purposes is proposed. Principal components analysis and agglomerative hierarchical clustering analysis are employed to objectively validate the proposed classification. Flow biotope assemblages may also represent reach-scale channel morphologies (step-pool, riffle-pool and glide-pool), although functional habitats exhibit differing ‘preferences’ for rougher or more tranquil environments within these. While the data and analysis are specific to the UK RHS, the methods and findings have wider application in situations, where rapid field appraisal methods and associated databases are deployed in water resource inventory and river rehabilitation design.

Testing scale variance in species–area and abundance–area relationships in a local assemblage: an example from a subtropical boulder shore

AbstractConstancy or scale variance of species–area and abundance–area relationships has rarely been considered within relatively small spatial domains of a local assemblage. Patterns of species/abundance–area relationships were experimentally investigated in a stone‐associated molluscan community on a subtropical boulder shore. In order to systematically examine the effects of variation in habitat area while maintaining other habitat characteristics constant through time, naturally occurring stones were selected and divided into different size classes according to surface area and used as habitat units for regular monitoring of a mobile molluscan community. Species richness and abundance (number of individuals and biomass) of molluscs scaled with stone area, but the power or double‐logarithmic regression was not always the best description of the species–area relationship. Seasonal scale invariance was shown by the species–area relationship, whereas scale variance was clearly recognizable in the abundance–area relationships. The latter phenomenon was generated mainly by large stones contributing disproportionately to increases in molluscan abundance in particular. Furthermore, there was a negative effect of small habitat area whereby molluscan abundance was disproportionately reduced on small stones. Some temporal variation in the observed patterns was also recognizable, with higher species richness and abundance in spring than in winter, again with larger stones showing preponderant importance. This study thus demonstrates the significance of scale variance/invariance in species/abundance–area relationships, even within relatively small spatial scales of local habitat.

Assessment for Habitat of Benthos Class by HSI Model based on Field Study of Regeneration of Tidal Flat and Eelgrass Zone in Ago Bay

As the assessment for the project of coastal regeneration, we have tried to expand HSI model (Habitat Suitability Index model) to the HSI model that is available for benthos group of class level. Inthis study, we determined the suitability ranges of IL, ratio of silt, and depth using the former model of HSI for each benthos such as ruditapes philippinarum and batillaria multiformis, and the HSI model was verified as the model for benthos group of class level such as groups of polychaeta, gastropoda, bivalvia using field data in Ago Bay. Further HU (Habitat Unit) of field study in Ago bay was calculated by these models. The result shows that the model may be a tool of general index for the project of coastal regeneration.

19th century woodland structure controls stand‐scale epiphyte diversity in present‐day Scotland

ABSTRACTAxioms developed from island biogeography theory (i.e. species–area relationships, effects of fragmentation and isolation) are central to the development of conservation strategy. Within this context, the ‘extinction debt’ hypothesis brings into question an often assumed relationship between species richness and present‐day spatial habitat structure (i.e. extent, fragmentation), suggesting instead that the richness and composition of biological communities may lag behind spatial changes in habitat. We examined evidence for an extinction debt among epiphytic lichens, a highly diverse biological group of significant conservation concern. Using sites in Scotland, we compared epiphyte species richness in smaller‐scale habitat units (aspen stands) to larger‐scale woodland structure (extent and fragmentation) measured at two spatial scales (1 km2and 4 km2) and for two timeframes, modern (1990s to 2000s) and historic (1860s to 1880s). Species richness was positively related to woodland extent and negatively related to woodland fragmentation; however, richness was explained better by historic woodland structure at a 1‐km2scale, than by modern woodland structure. The results indicate: (1) a coupling of stand‐scale epiphyte assembly and dynamics of the wider woodland ecosystem, and (2) a significant lag in the response of epiphyte species richness to habitat spatial structure. However, the effect of spatial habitat structure is different between species groups with contrasting traits. The effect of decreasing woodland extent on epiphyte richness is generally more severe for microlichens (comprising a greater number of rare and specialist species) than the more generalist macrolichens.

Support for mending the matrix: resource seeking by butterflies in apparent non-resource zones

In conserving organisms, a bipolar view has generally been adopted of landscapes, in which resources are allocated to patches of habitats and the matrix ignored. Allocating additional resources to the matrix would depend on two conditions: first, that organisms search for resources in landscapes regardless of differences in vegetation types and resource availability; second, that when resources occur in the matrix they are used by species. Behavioural data linked to biotope and substrate types, on three pierid species (Pieris brassicae, P. rapae, P. napi), have been examined to explore the relationship between flight modes and resource availability. Search flight and resource use, taken as measures of resource quests, occur extensively in all biotopes and over all substrates in addition to direct linear flight, more typical of butterflies when migrating between habitat units. Resource seeking and using even exceed direct flight in some biotopes that have been regarded generally as lacking in resources for these butterflies. For example, such is the case for P. brassicae in woodland and for P. rapae in scrub. This finding supports the view for repairing the matrix and enhancing the general countryside outside habitat patches with resources increasingly being made for organisms. The proviso is that species’ requirements are adequately researched and resourced so as not to become sinks.

Experimental analysis of recruitment patterns of coral reef fishes in seagrass beds: Effects of substrate type, shape, and rigidity

Habitat choice of reef fish larvae at settlement is one of the mechanisms proposed to explain spatial patterns in the distribution of fishes and the corresponding spatial structure of communities. Field experiments using Pomacentridae were conducted at Iriomote Island, southern Japan, in order to determine if rare recruitment of coral reef fishes in seagrass beds is due to larval settlement preference. When three types of natural patch treatments (branching coral patch, seagrass patch, and control without patches) were established in cleared seagrass squares in the center of a seagrass bed, four pomacentrid species, Amblyglyphidodon curacao, Dischistodus prosopotaenia, Cheiloprion labiatus, and Dascyllus aruanus, recruited exclusively onto the coral patches, indicating that larvae distributed in the seagrass bed may have preferred a coral rather than seagrass substrate as a settlement habitat. The effects of differences in physical shape (grid structure for branching coral vs. vertical structure for seagrass leaves) and rigidity (rigid substrate for coral vs. flexible substrate for seagrass) between coral and seagrass substrates on such recruitment patterns were investigated using artificial coral and seagrass units. When artificial habitat units with predator exclusion cages were established in the cleared seagrass squares as above, high densities of A. curacao and D. prosopotaenia recruits were observed on the rigid rather than flexible habitat units (both unit types having similar shape), whereas differences in recruit numbers of the two species were unclear in differently shaped units. These results demonstrated that even though pomacentrid larvae are distributed in the seagrass bed, they do not settle on the seagrass substrate owing to their habitat choice being partially based on a preference for substrate rigidity. Moreover, non-recruitment of C. labiatus and D. aruanus on artificial habitat units suggested that the presence of living coral substrates rather than physical shape/rigidity of substrates are an important cue for habitat choice of these fishes.