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Habitat Network (habitat + network)

Distribution by Scientific Domains

Life Sciences	83%

Selected Abstracts

The relationships between habitat topology, critical scales of connectivity and tick abundance Ixodes ricinus in a heterogeneous landscape in northern Spain

ECOGRAPHY, Issue 5 2003
Agustin Estrada-Peña
The habitat mosaic was used to quantify connectivity between patches of different tick density of the notorious tick species Ixodes ricinus in an attempt to determine the cause of variations in tick abundance among apparently homogeneous sites in northern Spain. The analysis revealed that patches with high tick abundance are "stepping-stone" territories that, when removed from the landscape, cause large changes in connectivity. Sites with medium tick abundance do not cause such a critical transition in connectivity. Patches with low tick abundance, but optimal abiotic conditions for survival, are located within the minimum cost corridors network joining the patches, while those sites where the tick has been intermittently collected are located at variable distances from this network. Sites where the tick is consistently absent, but where the habitat is predicted to be suitable (old, heterogeneous forests of Quercus spp.) for the tick, are very separated from this main network of connections. These results suggest that tick distribution in a zone is highly affected not only by abiotic variables (vegetation and weather) but also by host movements. Dispersal of the tick is a function of how the hosts perceive the habitat, and the habitat's permeability to host movement. Permanent tick populations seem to be supported by the existence of these critical, high density patches, located at significant places within the habitat network. [source]

Movement of two grassland butterflies in the same habitat network: the role of adult resources and size of the study area

ECOLOGICAL ENTOMOLOGY, Issue 2 2003
Christine Schneider
Abstract. 1., Movement patterns of two butterfly species (meadow brown Maniola jurtina L. and scarce copper Lycaenae virgaureae L.) were studied in a 172 ha area within a landscape with a high percentage of suitable habitats for mark,release,recapture experiments. 2., Adult resource density, but not patch size or larval food plant abundance, influenced the numbers and the fractions of residents, emigrants, and immigrants. 3., Differences between species were observed in movement frequency and maximum distances moved but not in mean distances moved. 4., The scarce copper showed much greater movement ability than expected from the results of published studies. This is believed to be a result of the comparatively large size of the study area and the high cover of suitable habitat (>50%). 5., The mean and maximum distances travelled by butterflies reflected differences in the size of the study area. [source]

Ecological dynamics of extinct species in empty habitat networks.

OIKOS, Issue 3 2003

This paper explores the relative effects of host plant dynamics and butterfly-related parameters on butterfly persistence. It considers an empty habitat network where a rare butterfly (Cupido minimus) became extinct in 1939 in part of its historical range in north Wales, UK. Surviving populations of the butterfly in southern Britain were visited to assess use of its host plant (Anthyllis vulneraria) in order to calibrate habitat suitability and carrying capacity in the empty network in north Wales. These data were used to deduce that only a portion (,19%) of the host plant network from north Wales was likely to be highly suitable for oviposition. Nonetheless, roughly 65,460 eggs (3273 adult equivalents) could be expected to be laid in north Wales, were the empty network to be populated at the same levels as observed on comparable plants in surviving populations elsewhere. Simulated metapopulations of C. minimus in the empty network revealed that time to extinction and patch occupancy were significantly influenced by carrying capacity, butterfly mean dispersal distance and environmental stochasticity, although for most reasonable parameter values, the model system persisted. Simulation outputs differed greatly when host plant dynamics was incorporated into the modelled butterfly dynamics. Cupido minimus usually went extinct when host plant were at low densities. In these simulations host plant dynamics appeared to be the most important determinant of the butterfly's regional extirpation. Modelling the outcome of a reintroduction programme to C. minimus variation at high quality locations, revealed that 65% of systems survived at least 100 years. Given the current amount of resources of the north Wales landscape, the persistence of C. minimus under a realistic reintroduction programme has a good chance of being successful, if carried out in conjunction with a host plant management programme. [source]

Complex habitat requirements and conservation needs of the only extant Baroniinae swallowtail butterfly

ANIMAL CONSERVATION, Issue 3 2004
Jorge L. León-Cortés
The unique butterfly species, Baronia brevicornis, perhaps the oldest taxon in the Papilionidae, is known to have a very restricted distribution in Mexico. Populations are restricted to southern Mexico in deciduous scrub forest where its host-plants, Acacia trees (Leguminosae), are common and widespread. Little is known of the conservation implications of its relationship with its host trees. We recorded fine scale population data for larval and adult B. brevicornis in 22 km2 of fragmented landscape in southern Mexico. Habitat associations determined from over 1319 transect walks reveal that B. brevicornis exhibited an extremely localised distribution, occupying < 1% of the study area and being mostly associated with Acacia woodlots. Detailed analyses of habitat requirements for larva and/or adult B. brevicornis suggest that it lays its eggs on Acacia pennatula and A. macracantha (two newly recorded larval host-plants), that eggs were laid disproportionately on Acacia trees with long branches (,2= 17.7, P < 0.001) and that the probability of finding adult B. brevicornis between occupied and un-occupied Acacia woodlots increased with host-plant density (,2= 18.4, P < 0.001). The results of this study suggest that conservation recommendations for B. brevicornis must consider the condition of the Acacia habitat network, given that Acacia is mostly associated with human-managed grazing systems. Effective conservation will require the establishment of connected networks of patches where natural dynamics can produce new habitats, as well as the creation of new habitats within colonisation distance. This research provides a rare case study of conservation biology of a Neotropical insect, emphasising the importance of using ecological information to provide management recommendations. [source]

Is the combination of topsoil replacement and inoculation with plant material an effective tool for the restoration of threatened sandy grassland?

APPLIED VEGETATION SCIENCE, Issue 4 2010
Carsten Eichberg
Abstract Question: Is it possible to restore dry calcareous inland sand ecosystems with their characteristic plant community structure within a 4-yr period by means of combined abiotic,biotic techniques (topsoil replacement, inoculation with raked/mown plant material from target areas)? Location: Upper Rhine valley, Germany. Methods: Two 4-year experiments were carried out on former arable land, each in the proximity of a reference area bearing a similar complex of threatened sandy grasslands (experiment 1: fine-scale; experiment 2: landscape scale). In both experiments we used nutrient-poor deep-sand substrate (abiotic approach), raked/mown inoculation material from target areas and grazing as management tool (biotic and management approach). The vegetation of the restoration and donor areas was sampled once a year and analysed by non-metric multidimensional scaling (NMDS) ordination and target-species ratios. Mixed linear models were calculated to determine effects of grazing (experiment 1) and year (both experiments). Results: NMDS revealed a continuous development of the restored sites towards the corresponding donor sites. Similarly, target-species ratios of the restored sites tended towards the ratios of the donor sites. To date, grazing effects have mainly been structural: reduction of a carpet-forming pleurocarpous moss species and of litter. In addition, cover of target species in relation to total plant cover was significantly enhanced by grazing in the last two study years. Conclusions: The combination of nutrient-poor substrate, inoculation with raked/mown plant material and grazing proved to be a very effective restoration method for dry base-rich sand ecosystems. After 4 yr the restored plant communities serve as well-developed parts of a habitat network. [source]