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Habitat Connectivity (habitat + connectivity)
Selected AbstractsHabitat connectivity and matrix restoration: the wider implications of agri-environment schemesJOURNAL OF APPLIED ECOLOGY, Issue 2 2006PAUL F. DONALD Summary 1The spread and intensification of agriculture are recognized as two of the most important global threats to wildlife. There are clear links between agricultural change and declines in biodiversity across a wide range of agricultural systems, and convincing evidence that reversing these changes leads to a recovery in wildlife populations. 2Nearly 4 billion euros are now paid annually through agri-environment schemes (AES) to farmers in Europe and North America to make environmental improvements to their land. Where appropriately designed and targeted, these schemes have proved successful in reversing declines in farmland wildlife populations. 3We argue that insights gained from island biogeography and metapopulation theory, and from theoretical and empirical assessments of landscape connectivity suggest that AES may carry substantial wider benefits, which so far have not been considered in the design and deployment of such schemes. ,Softening' agricultural land could offset some of the negative impacts on biodiversity of the loss and fragmentation of non-agricultural habitats; could allow species to adapt to climate change; could slow the spread of alien and invasive species; and could contribute positively to the coherence of key biodiversity and protected area networks. Indeed, AES might represent the only viable way to counter these threats. 4We outline a number of ways in which these wider benefits could be taken account of in the design of AES and suggest a number of characteristics of the species most likely to benefit from them. 5Synthesis and applications. Agri-environment schemes might bring significant environmental benefits to habitats other than farmland by restoring the agricultural matrix that separates them. Theoretical and empirical research suggests that matrix restoration improves a number of ecosystem functions. Where they are available, AES might therefore represent a viable mechanism for addressing a range of pandemic environmental problems such as global climate change. Little consideration has so far been given to these wider conservation applications in the design, deployment and monitoring of AES. [source] Recognising the necessity for Indo-Pacific seagrass conservationCONSERVATION LETTERS, Issue 2 2010Richard K.F. Unsworth Abstract Seagrass meadows are declining globally at an unprecedented rate, yet these valuable ecosystem service providers remain marginalized within many conservation agendas. In the Indo-Pacific, this is principally because marine conservation priorities do not recognize the economic and ecological value of the goods and services that seagrasses provide. Dependency on coastal marine resources in the Indo-Pacific for daily protein needs is high relative to other regions and has been found in some places to be up to 100%. Habitat loss therefore may have negative consequences for food security in the region. Whether seagrass resources comprise an important contribution to this dependency remains largely untested. Here, we assemble information sources from throughout the Indo-Pacific region that discuss shallow water fisheries, and examine the role of seagrass meadows in supporting production, both directly, and indirectly through process of habitat connectivity (e.g., nursery function and foraging areas). We find information to support the premise that seagrass meadows are important for fisheries production. They are important fishery areas, and they support the productivity and biodiversity of coral reefs. We argue the value of a different paradigm to the current consensus on marine conservation priorities within the Indo-Pacific that places seagrass conservation as a priority. [source] Range-wide patterns of greater sage-grouse persistenceDIVERSITY AND DISTRIBUTIONS, Issue 6 2008Cameron L. Aldridge ABSTRACT Aim, Greater sage-grouse (Centrocercus urophasianus), a shrub-steppe obligate species of western North America, currently occupies only half its historical range. Here we examine how broad-scale, long-term trends in landscape condition have affected range contraction. Location, Sagebrush biome of the western USA. Methods, Logistic regression was used to assess persistence and extirpation of greater sage-grouse range based on landscape conditions measured by human population (density and population change), vegetation (percentage of sagebrush habitat), roads (density of and distance to roads), agriculture (cropland, farmland and cattle density), climate (number of severe and extreme droughts) and range periphery. Model predictions were used to identify areas where future extirpations can be expected, while also explaining possible causes of past extirpations. Results, Greater sage-grouse persistence and extirpation were significantly related to sagebrush habitat, cultivated cropland, human population density in 1950, prevalence of severe droughts and historical range periphery. Extirpation of sage-grouse was most likely in areas having at least four persons per square kilometre in 1950, 25% cultivated cropland in 2002 or the presence of three or more severe droughts per decade. In contrast, persistence of sage-grouse was expected when at least 30 km from historical range edge and in habitats containing at least 25% sagebrush cover within 30 km. Extirpation was most often explained (35%) by the combined effects of peripherality (within 30 km of range edge) and lack of sagebrush cover (less than 25% within 30 km). Based on patterns of prior extirpation and model predictions, we predict that 29% of remaining range may be at risk. Main Conclusions, Spatial patterns in greater sage-grouse range contraction can be explained by widely available landscape variables that describe patterns of remaining sagebrush habitat and loss due to cultivation, climatic trends, human population growth and peripherality of populations. However, future range loss may relate less to historical mechanisms and more to recent changes in land use and habitat condition, including energy developments and invasions by non-native species such as cheatgrass (Bromus tectorum) and West Nile virus. In conjunction with local measures of population performance, landscape-scale predictions of future range loss may be useful for prioritizing management and protection. Our results suggest that initial conservation efforts should focus on maintaining large expanses of sagebrush habitat, enhancing quality of existing habitats, and increasing habitat connectivity. [source] Distribution of myrmecochorous species over the landscape and their potential long-distance dispersal by emus and kangaroosDIVERSITY AND DISTRIBUTIONS, Issue 1 2008María Calviño-Cancela ABSTRACT Topographical heterogeneity can create a mosaic of substrate types leading to the formation of isolated plant populations. Seed dispersal then becomes crucial for the colonization of such suitable but remote substrate types. We surveyed the distribution of seven elaiosome-bearing species (myrmecochores) over 5 km2 of natural heathland in southwestern Australia. Ants are the standard means of dispersal of these species, which provide limited dispersal (usually of a few metres). Six species were associated with particular substrate types (dune or swale) and all occurred as discrete populations, on average 270,500 m apart, with closest dune edges 280 m apart. We evaluated the possible roles of emus and kangaroos as alternative agents of long-distance seed dispersal between substrate types. Their droppings contained viable seeds of three of the target species, as well as other myrmecochores, and were evenly distributed over the substrate types. While migration of these plant species between preferred substrate types seems unlikely when considering only their standard dispersal agents (ants), it is highly likely in the presence of emus (in particular) and kangaroos that act as non-standard dispersers. This may have important consequences for plant species conservation by increasing habitat connectivity and favouring regional persistence. [source] Representing genetic variation as continuous surfaces: an approach for identifying spatial dependency in landscape genetic studiesECOGRAPHY, Issue 6 2008Melanie A. Murphy Landscape genetics, an emerging field integrating landscape ecology and population genetics, has great potential to influence our understanding of habitat connectivity and distribution of organisms. Whereas typical population genetics studies summarize gene flow as pairwise measures between sampling localities, landscape characteristics that influence population genetic connectivity are often continuously distributed in space. Thus, there are currently gaps in both the ability to analyze genotypic data in a continuous spatial context and our knowledge of expected of landscape genetic structure under varying conditions. We present a framework for generating continuous "genetic surfaces", evaluate their statistical properties, and quantify statistical behavior of landscape genetic structure in a simple landscape. We simulated microsatellite genotypes under varying parameters (time since vicariance, migration, effective population size) and used ancestry (q) values from STRUCTURE to interpolate a genetic surface. Using a spatially adjusted Pearson's correlation coefficient to test the significance of landscape variable(s) on genetic structure we were able to detect landscape genetic structure on a contemporary time scale (,5 generations post vicariance, migration probability ,0.10) even when population differentiation was minimal (FST,0.00015). We show that genetic variation can be significantly correlated with geographic distance even when genetic structure is due to landscape variable(s), demonstrating the importance of testing landscape influence on genetic structure. Finally, we apply genetic surfacing to analyze an empirical dataset of black bears from northern Idaho USA. We find black bear genetic variation is a function of distance (autocorrelation) and habitat patch (spatial dependency), consistent with previous results indicating genetic variation was influenced by landscape by resistance. These results suggest genetic surfaces can be used to test competing hypotheses of the influence of landscape characteristics on genetic structure without delineation of categorical groups. [source] Connectivity, non-random extinction and ecosystem function in experimental metacommunitiesECOLOGY LETTERS, Issue 5 2010Philip Staddon Ecology Letters (2010) 13: 543,552 Abstract The spatial insurance hypothesis indicates that connectivity is an important attribute of natural ecosystems that sustains both biodiversity and ecosystem function. We tested the hypothesis by measuring the impact of manipulating connectivity in experimental metacommunties of a natural and diverse microecosystem. Isolation led to the extinction of large-bodied apex predators, subsequently followed by increases in prey species abundance. This trophic cascade was associated with significantly altered carbon and nitrogen fluxes in fragmented treatments. The ecosystem impacts were characteristic of a function debt because they persisted for several generations after the initial loss of connectivity. Local extinctions and disruption of ecosystem processes were mitigated, and even reversed, by the presence of corridors in the connected metacommunities, although these beneficial effects were unexpectedly delayed. We hypothesized that corridors maintained grazer movement between fragments, which enhanced microbial activity, and decomposition in comparison to isolated fragments. Our results indicate that knowledge of habitat connectivity and spatial processes is essential to understand the magnitude and timing of ecosystem perturbation in fragmented landscapes. [source] Population structure and its implications for conservation of the great silver beetle Hydrophilus piceus in BritainFRESHWATER BIOLOGY, Issue 11 2007TREVOR J. C. BEEBEE Summary 1. The great silver water beetle Hydrophilus piceus is one of the largest aquatic insects in Europe. In Britain it is rare and endangered, and confined to a small number of low-lying marshes. Very little is known about the beetle populations in any of these areas, or the connectivity between them. 2. To investigate the population structure of H. piceus in Britain, four polymorphic microsatellite loci were identified and characterized. The genome of this beetle seems to have few microsatellites but contains a high proportion of a larger repeated sequence. 3. All six of the main British populations (Somerset, Lewes, Pevensey, Romney, North Kent and Norfolk) showed substantial genetic diversity at the microsatellite loci. However, estimates of effective population size at one site (Pevensey) were remarkably low, at <10 adults for the period 2004,05. 4. Most of the genetic diversity was partitioned within rather than among the populations, although there was, nevertheless, significant genetic sub-structuring. Almost all population pairwise Fst estimates were significantly different from zero, and there was a clear isolation-by-distance effect. Assignment tests and cluster analyses demonstrated interpopulation relationships largely consistent with their geographical separations. 5. Hydrophilus disperses by flight, and records from moth traps indicated that there was no month in which the beetles never flew, but that flight activity was highest in the spring. 6. The genetic data highlight the need to maintain or regenerate habitat connectivity within flying distance for H. piceus, and to sustain large areas of suitable breeding marshes. [source] Mammals, agri-environment schemes and set-aside , what are the putative benefits?MAMMAL REVIEW, Issue 4 2007D. W. MACDONALD ABSTRACT 1The impacts of agricultural intensification on farmland wildlife have been the subject of increasing concern, particularly over the last two decades. Population declines have occurred for a number of mammalian species, sometimes drastically so, and changes in farming practice are believed to be significant contributory factors. 2The major policy instruments for delivering environmental benefits on farmland are agri-environment schemes. These encourage farmers to adopt more environmentally sensitive farming practices to promote farmland biodiversity. Additionally, compulsory set-aside, which reduces agricultural surplus, could also have positive impacts on wildlife. In this paper we consider some of the putative benefits of agri-environment schemes and set-aside for mammals. 3We review how establishment and management options within agri-environment schemes and set-aside might affect habitat resources for mammals. For example, conservation headlands increase plant and invertebrate resources within the crop edge for mammals such as wood mice. Grassy field margins can support communities of smaller mammals, and hedgerows may act as important commuting and hunting routes. Their potential will depend on factors such as seed mixtures used, timing and severity of cutting, and length of time they have been in place. 4At a farm level, habitat heterogeneity may be increased through organic agriculture, which is supported by some agri-environment schemes. Studies suggest significant benefits to mammals, including wood mice and bats. However, it is increasingly recognized that effective conservation of farmland mammals must seek solutions at the landscape scale, addressing such issues as habitat connectivity between farms. One approach may be the better targeting of scheme agreements. 5We suggest that agri-environment schemes and set-aside can contribute to the conservation of mammals on farmland. Recent policy changes are likely to have further positive impacts on farmland wildlife but appropriate mammal monitoring programmes must be developed rigorously to assess their effects. [source] The colonization of Europe by the freshwater crustacean Asellus aquaticus (Crustacea: Isopoda) proceeded from ancient refugia and was directed by habitat connectivityMOLECULAR ECOLOGY, Issue 14 2005R. VEROVNIK Abstract Recent continental-scale phylogeographic studies have demonstrated that not all freshwater fauna colonized Europe from the classic Mediterranean peninsular refugia, and that northern or central parts of the continent were occupied before, and remained inhabited throughout the Pleistocene. The colonization history of the ubiquitous aquatic isopod crustacean Asellus aquaticus was assessed using mitochondrial COI and a variable part of nuclear 28S rDNA sequences. Phylogeographic analysis of the former suggested that dispersion proceeded possibly during late Miocene from the western part of the Pannonian basin. Several areas colonized from here have served as secondary refugia and/or origins of dispersion, well before the beginning of the Pleistocene. Postglacial large-scale range expansion was coupled with numerous separate local dispersions from different refugial areas. Connectivity of the freshwater habitat has played an important role in shaping the current distribution of genetic diversity, which was highest in large rivers. The importance of hydrographic connections for the maintenance of genetic contact was underscored by a discordant pattern of mtDNA and nuclear rDNA differentiation. Individuals from all over Europe, differing in their mtDNA to a level normally found between species or even genera (maximal within population nucleotide divergence reached 0.16 ± 0.018), shared the same 28S rRNA gene sequence. Only populations from hydrographically isolated karst water systems in the northwestern Dinaric Karst had distinct 28S sequences. Here isolation seemed to be strong enough to prevent homogenization of the rRNA gene family, whereas across the rest of Europe genetic contact was sufficient for concerted evolution to act. [source] Interactions between habitat quality and connectivity affect immigration but not abundance or population growth of the butterfly, Parnassius smintheusOIKOS, Issue 10 2009Stephen F. Matter Habitat geometry has been a primary focus in studies of spatially structured systems. Recent studies have indicated that a more comprehensive approach including habitat quality may be needed, however most previous studies have neglected potential interactions between quality and geometry. We investigated the effects of habitat quality for the butterfly Parnassius smintheus among a series of 17 sub-populations. Specifically, we examined how habitat connectivity and local nectar flower density affect dispersal, and local population abundance and growth. We first determined which flower species were potentially important by examining nectar flower electivity and then quantified nectar flower density in meadows over a five year period (2003,2007). These data along with meadow connectivity were compared to local population statistics derived from mark,recapture over the same time period. The number of immigrants to a meadow increased as meadow connectivity increased, but showed no direct relationship with nectar flower density; however, there was a significant interaction between meadow connectivity and nectar flower density such that meadows with high connectivity and a high density of nectar flowers received the greatest number of immigrants. The number of emigrants from a meadow increased with increasing habitat quality and connectivity, but showed no interactive effect. The abundance of butterflies increased with meadow connectivity, but showed no relationship with habitat quality or any interactive effect. Separate experiments showed that access to nectar flowers significantly increased female reproductive output, but not lifespan. Despite the effects on immigration and reproductive output, local population growth rates also showed no relationship to nectar flower density. Our results indicate that habitat quality can be important for immigration in spatially structured populations; however, effects of habitat quality may not necessarily translate into higher abundance or population growth. Additionally, habitat quality should not be considered independently from habitat isolation, particularly if it directly affects dispersal. Preserving or augmenting habitat quality will do little to bolster immigration or colonization without adequate connectivity. [source] Phylogeography of the Angolan black and white colobus monkey, Colobus angolesnsis palliatus, in Kenya and TanzaniaAMERICAN JOURNAL OF PRIMATOLOGY, Issue 8 2010Monica M. McDonald Abstract Little is known about genetic variation in the 6,8 subspecies of Colobus angolensis, currently distinguished by pelage differences. We present a comparative genetic analysis of one of these subspecies, C. a. palliatus, in Kenya and Tanzania that assesses evolutionary relationships and patterns of mitochondrial genetic diversity in 103 individuals across its geographic range. Fecal samples from approximately 156 individuals were collected in four localities: (1) Diani Forest, Kenya; (2) Shimoni, Kenya; (3) Udzungwa Mountains National Park, Eastern Arc Mountains, Tanzania; and (4) Mount Rungwe, Southern Highlands, Tanzania. These samples represent at least six groups, with 5,15 samples from each. Comparative sequence analysis of a 1,795 base pair mtDNA fragment revealed 19 unique haplotypes in four populations. Phylogenetic analyses suggest that sampled Kenyan haplotypes are paraphyletic, with one Kenyan haplotype basal to all other sampled haplotypes. Analysis of molecular variance (AMOVA) suggests high levels of genetic variation among populations (,ST 0.72, P<0.001). Genetic data are concordant with a subspecies level differentiation between C. a. palliatus populations in Kenya and those in Central and southern Tanzania, as earlier suggested based on pelage differences. This study highlights the evolutionary distinctiveness of Kenyan populations of C. a. palliatus relative to Tanzanian populations. Although C. a. palliatus habitat in Tanzania is currently better protected than in Kenya, our results suggest Kenyan and Tanzanian populations should be considered distinct units, and the protection of C. a. palliatus habitat in Kenya, as well as habitat connectivity between Kenyan populations, should be prioritized for conservation and management. Am. J. Primatol. 72:715,724, 2010. © 2010 Wiley-Liss, Inc. [source] Structures, dynamics and stability of reef fish assemblages in non-reefal coral communities in Hong Kong, ChinaAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2009Tze-Wai Tam Abstract 1.A detailed study on the spatial and temporal patterns of reef fish assemblages associated with non-reefal coral communities at A Ma Wan (AMW) and A Ye Wan (AYW) in Tung Ping Chau, Hong Kong, China, was carried out using an underwater visual census method from January 1998 to December 1999. 2.The study identified a total of 106 species (76 genera in 39 families) of fish in the study sites, in which 88 species were recorded in AMW and 78 species in AYW. Seasonal patterns in the abundance and species richness of all reef fishes and most of the frequently encountered families/trophic groups in both study sites were observed. Seasonal fluctuation of macroalgae, the influence of recruitment of larvae, and the possible seasonal variation in the behaviour of fish may all contribute to these observed seasonal patterns. 3.Multidimensional scaling (MDS) ordinations demonstrated that there were spatial variations in the fish community structures within and between sites. Such spatial patterns were possibly related to the spatial variation of the coral community structures in the study sites. The ordinations also showed that the fish community structures in the study sites were not seasonally stable. Such temporal instability of the fish community structures may be partly due to habitat isolation among the fish communities around the island. 4.These results imply that preservation and enhancement of habitat connectivity of the coral communities should be one of the main conservation strategies for the reef fish communities of Tung Ping Chau, and those of Hong Kong in general. This strategy may be equally applicable to other non-reefal coral communities elsewhere around the world. Copyright © 2008 John Wiley & Sons, Ltd. [source] Flower visitors and pollination in the Oriental (Indomalayan) RegionBIOLOGICAL REVIEWS, Issue 3 2004Richard T. Corlett ABSTRACT Current knowledge of flower visitors and pollination in the Oriental Region is summarised. Much less is known about pollination than seed dispersal and the coverage of habitats and taxa in the region is very uneven. The available evidence suggests that pollination in lowland forests is dominated by highly social bees (mainly Trigona and Apis species), with beetles probably the next most important group, followed by other bees and flies. In comparison with the better-studied Neotropics, large solitary bees, moths, Lepidoptera and vertebrates are relatively less important. These differences are greatest in the canopy of the lowland dipterocarp forests of Southeast Asia, where they probably reflect the unique temporal pattern of floral resource availability resulting from,general flowering'at supra-annual intervals. Apis bees (but not Trigona species) are also important in most montane, subtropical and non-forest habitats. Apart from the figs (Ficus spp.), there are few well-documented examples of plant species visited by a single potential pollinator and most plant-pollinator relationships in the region appear to be relatively generalised. The small sizes of most pollinators and the absence of direct human exploitation probably make pollination mutualisms less vulnerable to failure as a result of human impacts than dispersal mutualisms, but more subtle impacts, as a result of altered gene flows, are likely to be widespread. On current evidence, pollination systems in the Oriental Region do not require any specific conservation action, but this review reinforces arguments for making the preservation (or restoration) of habitat connectivity the major focus of Oriental conservation. [source] Distribution Patterns of Migrant and Resident Birds in Successional Forests of the Yucatan Peninsula, Mexico,BIOTROPICA, Issue 1 2001Andrea L. Smith ABSTRACT Increasing human activity in the Yucatan peninsula has led to declines in older stages of successional forest, threatening regional habitat diversity. To determine potential effects of this habitat loss on the region's avifauna, we examined the relative use of different forest stages by resident and migrant birds during the nonbreeding season. We used the fixed-width transect method to compare the distribution, abundance, and diversity of forest birds in early (five to ten years old), mid (15,25 years), and late (<50 years) successional forests in the state of Campeche, Mexico, in the south-central part of the peninsula. All stages of successional forest had highly similar bird assemblages and did not differ in bird abundance or diversity. Both migrant and resident birds occurred across the successional gradient. The majority of habitat specialists, however, were resident birds restricted to late-successional forest, indicating that early secondary growth may not be suitable for all species. Furthermore, resident birds that typically participate in mixed-species flocks attained their greatest densities in the oldest forest habitat. Rapid recovery of pre-disturbance physiognomic features, in addition to high levels of habitat connectivity in the region, may contribute to similar bird communities across a range of successional stages. The high degree of edge characterizing much of the forest mosaic also may allow birds access to different serai stages. Loss of late-successional forest, however, is likely to adversely affect the subset of resident avifauna that depends on unique features of mature habitat such as snags, large trees, and climatic buffering. Conservation efforts in Campeche should focus on the specialized requirements of the most habitat-restricted species while preserving the current landscape mosaic characteristic of the small-scale shifting cultivation system. RESUMES El aumento de la actividad humana en el uso del suelo en la Peninsula de Yucatán, ha resultado en la disminución de la regeneración de la selva a etapas más maduras de sucesión, amenazando la diversidad regional de habitats. Para determinar los efectos de esta pérdida sobre la avifauna de la región, estudiamos el uso de diferentes etapas de sucesión de la selva por aves residentes y migratorias durante la temporada no reproductiva. Usamos el método de transecto linear de anchura fija para comparar la distributión, abundancia y diversidad de aves en vegetaclón sucesional (acahuales) de diferentes edades, incluyendo acahual joven (cinco a diez años de edad), acahual de edad media (15-25 afios) y selva (>50 afios) en el sur del estado de Campeche, Mexico. Diferentes etapas de sucesión de la selva tuvieron composition de aves muy similares y no variaron en la abundancia y la diversidad. Tanto las especies migrantes como residentes, estuvieron presentes a travél del gradiente sucesional. Sin embargo, la mayoría de los especialistas fueron aves residentes restingidas a etapas más viejas de sucesión de selva, indicando que la vegetatión sucesional temprana no es favorable para todas las especies. En adicion, las aves residentes que tipicamente participan en bandadas mixtas tuvieron sus densidades más altas en la selva de mayor edad de sucesión. La rápida recuperatión de la selva a sus caracteristicas de estado primario, en adición al alto grado de conectividad de habitat en la región, puede permitir a muchas especies nativas encontrarse en diferentes etapas de vegetatión sucesional. El alto grado de efecto de borde que caracteriza la mayor pane del mosaico de bosque tambíen puede permitir a las aves el acceso a los diferentes tipos de vegetación sucesional. Sin embargo, la pérdida de selva en etapa más madura de sucesión, probablemente rendrá un efecto más adverso sobre el grupo de aves residentes que depende de características únicas de selva madura, tales como árboles secos, árboles grandes y amortiguamiento climático. Los esfuerzos de conservatión deberían enfocarse sobre las especies sensibles con requerimientos especializados de hábitat, preservando selva nativa a la vez que las características actuates de mosaico del paisaje, manteniendo las actividades de roza-tumba y quema a pequena escala. [source] | ||||||||||||||||||||||