Broadest Scales (broadest + scale)

Distribution by Scientific Domains

Selected Abstracts

Predictive models of habitat preferences for the Eurasian eagle owl Bubo bubo: a multiscale approach

ECOGRAPHY, Issue 1 2003
Jose Antonio Martínez
Habitat preference of eagle owls Bubo bubo were examined through comparing habitat composition around 51 occupied cliffs and 36 non-occupied cliffs in Alicante (E Spain). We employed Generalized Linear Models to examine patterns of habitat preference at three different spatial scales: nest site (7 km2), home range (25 km2), and landscape (100 km2). At the nest site scale, occupied cliffs were more rugged, had a greater proportion of forest surface in the surroundings, and were further from the nearest paved road than unoccupied cliffs. Additionally, probability of having an occupied cliff increased when there was another occupied territory in the surroundings. At both the home range scale and the landscape scale, high probabilities of presence of eagle owls were related to high percentages of Mediterranean scrubland around the cliffs, which are the preferred habitat of European rabbits Oryctolagus cuniculus, the main prey of the owls. We suggest a hierarchical process of habitat selection in the eagle owl concerning suitable trophic resources at the broadest scales and adequate sites for breeding and roosting at the smallest scale. However, it should be noted that some structural features such as the proximity of roads were not necessarily avoided by the owls, but their presence were possibly constrained by systematic killing of individuals. Our paper provides new evidence for the requirement of multi-scale approaches to gain insight into both the different limiting factors for the persistence of populations and the role of individual perception of the environment in the evolution of habitat selection. [source]

Broad-scale environmental response and niche conservatism in lacustrine diatom communities

GLOBAL ECOLOGY, Issue 5 2010
Joseph R. Bennett
ABSTRACT Aim, (1) To resolve theoretical debates regarding the role of environment versus dispersal limitation, the conservatism of niches across distances and the prevalence of environmental specialists in diatom communities. (2) To provide guidance on the use of diatom communities and other microbial analogues to analyse ecological response to environmental change. Location, Eight hundred and ninety-one lakes in five regional datasets from north-western Europe and four regional datasets from north-eastern North America. Methods, Lacustrine diatom communities were analysed at three scales: inter-continental, intra-continental and regional. Nested partial redundancy analyses (RDAs) were used to determine spatial versus environmental components of community variation. Weighted-averaging (WA) regression and calibration, as well as logistic and quadratic regressions, were used to detect niche conservatism and the prevalence of environmental specialists. Results, Community patterns indicate that dispersal limitation acts predominantly at the inter-continental scale, while at the regional (less than c. 1,000,000 km2) scale, a single environmental variable (pH) explains more than five times the community variation as spatial (dispersal-related) variables. In addition, pH niche components appear to be conserved at the inter-continental scale, and environmental specialization does not impose relative rarity, as specialists apparently readily disperse to suitable environments. Main conclusions, Analysis at multiple scales is clearly important in determining the influences of community variation. For diatom communities, dispersal limitation acts most strongly at the broadest scales, giving way to environment at the scales considered by most analyses. The availability of a wide variety of propagules with consistent niches across regions indicates that diatom communities reflect the succession of taxa according to local environmental conditions, rather than disequilibrium with the environment or adaptation of local populations. While multi-scale analyses must be undertaken for other groups to resolve debates over community drivers and determine appropriate scales for prediction, for diatoms (and probably other microbial communities), responses to environmental change can be inferred using analogue datasets from large geographic areas. [source]

Diagnostic osteology and analysis of the Mid- to Late Holocene dynamics of shags and cormorants in Tierra del Fuego

D. Causey
Abstract We present here illustrated characteristics and anatomical descriptions of features that can be used to discriminate between four common skeletal elements (i.e. humerus, coracoid, femur, tarsometatarsus) of the five species of shags and cormorants known to occur in southern South America. We also present a detailed study of their distribution and abundance from about 6000 years before present to historical times as revealed by identification of faunal material excavated earlier and by re-analysis of material published previously. Our results present a high-resolution examination of the avian resource base used by early human hunters, and provide a foundation for future studies on the palaeoavifauna of Tierra del Fuego during the Mid- to Late Holocene. On the broadest scales, species diversity of the Phalacrocoracidae is qualitatively stable over space and time, a pattern that is also reflected in the larger marine bird community. On a finer scale, however, our results indicate that the abundance and distribution of cormorants and shags in Mid- and Late Holocene zooarchaeological deposits varied in a complex manner through time. These patterns do not appear to be related to proximity effects of hunters to colonies, but to other factors possibly associated with environmental change. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Chloroplast evidence for geographic stasis of the Australian bird-dispersed shrub Tasmannia lanceolata (Winteraceae)

Abstract Few chloroplast-based genetic studies have been undertaken for plants of mesic temperate forests in the southern hemisphere and fossil-based models have provided evidence of vegetation history only at the broadest scales in this region. This study investigates the chloroplast DNA phylogeography of Tasmannia lanceolata (Winteraceae), a fleshy-fruited, bird-dispersed shrub that is widespread in the mountains of southeastern Australia and Tasmania. Thirty haplotypes were identified after sequencing 3206 bp of chloroplast DNA in each of 244 individuals collected across the species' range. These haplotypes showed unexpectedly strong phylogeographic structuring, including a phylogeographic break within a continuous part of the species' range, with the distribution of four major clades mostly not overlapping, and geographic structuring of haplotypes within these clades. This strong geographic patterning of chloroplast DNA provided evidence for the survival of T. lanceolata in multiple putative wet forest refugia as well as evidence for additional wet forest species refugia in southeastern Australia. In western Tasmania lower haplotype diversity below the LGM tree line compared to above the LGM tree line suggests that glacial refugia at high altitudes may have been important for T. lanceolata. The level of geographic structuring in T. lanceolata is similar to gravity dispersed southern hemisphere plants such as Nothofagus and Eucalyptus. Behavioural traits of the birds transporting seed may have had a strong bearing on the limited transport of T. lanceolata seed, although factors limiting establishment, possibly including selection, may also have been important. [source]