, P. R. (1982): Anorexia nervosa, visual disturbance, and Laurence-Moon-Biedl syndrome. Lancet , 22 (1) (8282): 1184.
Fernandez-Aranda, F., Crespo, J. M., Jiménez-Murcia, S., Krug, I., Vallejo-Ruiloba, J. (2006): Blindness
Authors:W. Ulrich, M. Zalewski, I. Hajdamowicz, M. Stańska, W. Ciurzycki, and P. Tykarski
The impact of disturbance on animal and plant assemblages has been described mainly in terms of aggregate community properties like species richness, abundance, or productivity. However, the question how disturbance acts on species interactions, particularly on patterns of co-occurrence, has received much less attention. Here we use a large pitfall trap sample of spiders from two complexes of lake islands in Northern Poland to show how disturbance by tourist visits affects species richness, composition and co-occurrence. On the pristine and protected islands of Lake Wigry, species co-occurrence was significantly segregated. Further, island species richness and abundances could be predicted from environmental correlates, particularly from island area, soil fertility and humidity. In turn, on the lake islands that are frequently visited by tourists, species co-occurrences were random and environmental correlates other than island area failed to predict species richness and abundances. However, species composition, α-, β-, and γ-diversities, as well as average local spider abundances did not significantly differ between both island complexes. Our results show that disturbance disassembles the structure of spider communities prior to visible richness and abundance effects. This result has implications for biological conservation. The detection of community disassembly might be an early sign for factors that act negatively on ecosystem functioning.
This research uses Principal Component Analysis (PCA) to investigate global ionospheric integrated electron content map (GIM) anomalies corresponding to Japan’s Iwate-Miyagi Nairiku earthquake on 13 June 2008 (UT) (Mj = 7.2, JMA scale). The PCA transform is applied to GIMs for 20:00 to 22:00 on June 08, 11 and 12, 2008 (UT). To perform the transform, image processing is used to subdivide the GIMs into 100 (36° long. and 18° lat.) smaller maps to form transform matrices of dimensions 2 × 1. The transform allows for principal eigenvalues to be assigned to ionospheric integrated electron content anomalies. Anomalies are represented by large principal eigenvalues (i.e., >0.5 in a normalized set). The possibility of geomagnetic storms and solar flare activity affecting the results is done through examining the Dst index for corresponding days. The study shows that for the Iwate-Miyagi Nairiku earthquake, PCA possibly determined earthquake related ionospheric disturbances for the whole region, including the epicenter.
Authors:G. Bacaro, S. Maccherini, A. Chiarucci, A. Jentsch, D. Rocchini, D. Torri, M. Gioria, E. Tordoni, S. Martellos, A. Altobelli, R. Otto, C. G. Escudero, S. Fernández-Lugo, J. M. Fernández-Palacios, and J. R. Arévalo
Invasion by alien plant species may be rapid and aggressive, causing erosion of local biodiversity. This is particularly true for islands, where natural and anthropogenic corridors promote the rapid spread of invasive plants. Although evidence shows that corridors may facilitate plant invasions, the question of how their importance in the spread of alien species varies along environmental gradients deserves more attention. Here, we addressed this issue by examining diversity patterns (species richness of endemic, native and alien species) along and across roads, along an elevation gradient from sea-level up to 2050 m a.s.l. in Tenerife (Canary Islands, Spain), at multiple spatial scales. Species richness was assessed using a multi-scale sampling design consisting of 59 T-transects of 150 m × 2 m, along three major roads each placed over the whole elevation gradient. Each transect was composed of three sections of five plots each: Section 1 was located on the road edges, Section 2 at intermediate distance, and Section 3 far from the road edge, the latter representing the “native community” less affected by road-specific disturbance. The effect of elevation and distance from roadsides was evaluated for the three groups of species (endemic, native and alien species), using parametric and non-parametric regression analyses as well as additive diversity partitioning. Differences among roads explained the majority of the variation in alien species richness and composition. Patterns in alien species richness were also affected by elevation, with a decline in richness with increasing elevation and no alien species recorded at high elevations. Elevation was the most important factor determining patterns in endemic and native species. These findings confirm that climate filtering reflected in varying patterns along elevational gradients is an important determinant of the richness of alien species (which are not adapted to high elevations), while anthropogenic pressures may explain the richness of alien species at low elevation.
Authors:E. Chaideftou, A. Kallimanis, E. Bergmeier, and P. Dimopoulos
Over millions of years there is a long-term increase in species richness, accompanied by substantial turnover in species composition. However, little is known about species temporal turnover over shorter, ecologically relevant time periods, such as years. In the present study, we examine the inter-annual temporal turnover in species composition in 100 m2 plots of the herbaceous layer in a submediterranean oak woodland over six years. We found that approximately half of the accumulated number of species over the six years is accommodated as temporal turnover. We also found that species temporal turnover in undisturbed control plots was not significantly different from that in plots where vegetation was recovering naturally without assistance, i.e., plots undergoing ecological succession. Only in the most disturbed (continuously overgrazed) plots temporal turnover was low to non-existent. We therefore suggest that diversity estimates based on a single year of observations may seriously underestimate species richness or the detrimental effects of disturbance, at least at the 100 m2 scale. Furthermore, we found that, with the exception of the heavily grazed plots, short-lived species (annuals and biennials) did not display significantly greater temporal turnover than long-lived (perennial) species. Our analysis also supports that the space for time substitution applies in the patterns of species turnover. Spatial species turnover was comparable to temporal turnover. Species that are observed in many plots are also present in many years, and vice versa. Also, the similarity in species composition decreased as the time period between observations increased, as is the case with distance decay. Overall we conclude that the patterns of species turnover in time resemble those in space, and thus temporal turnover makes an important contribution to total biodiversity that should not be ignored.
The study examined the vegetation composition and phenotypic traits at five sites, differing in degree of disturbance, in a tropical dry deciduous forest of India. A total of 49 species and 4033 individuals (≯= 9.6 cm dbh) were enumerated in the cumulative 15-ha permanently protected area. The study revealed that the five sites represented five more or less different communities (species combinations with different dominants). On the basis of phenotypic traits, these communities or sites could not be discriminated, either by proportion of species belonging to different trait categories or by the cumulative importance value of the trait categories. As a result, disturbance did not affect the predominant traits. Evidently, all the communities shared the major phenotypic traits of the dry deciduous forest. Small leaf size, medium leaf texture, rough bark texture and medium deciduousness characterized the dry deciduous forest vegetation. Both the percent of species and importance values were larger for medium or less deciduous trait categories than for highly deciduous trait, representing a trade-off between water loss and the period of dry matter synthesis.
We used multivariate analysis to model boreal forest stand structure and dynamics at Riding Mountain National Park, Manitoba based on data from 202 sampled stands. Eight forest stand-types were recognized based on canopy composition: black spruce on peat substrates, jack pine - black spruce, bur oak, eastern deciduous (green ash - American elm - Manitoba maple), balsam fir, trembling aspen - paper birch - mountain maple, trembling aspen - balsam poplar, and white spruce. The first four stand-types occur in edaphically distinct environments, while the four remaining boreal mixedwood stand-types occur in edaphically similar environments. We found that the composition and abundance of advance regeneration were best predicted by current canopy composition (redundancy = 54.4%); this reflects both the limited dispersal of conifer seeds and the strong vegetative reproductive capacity of hardwoods. Biotically-controlled site factors such as bareground, herb and shrub cover, ungulate browsing intensity, and stand age were also reasonably good predictors f advance regeneration (redundancy = 31.7%). Edaphic variables such as soil pH, conductivity, particle size, organic horizon depth and slope proved to be poor predictors of advance regeneration, however (redundancy = 18.1%). Size-class ordination indicated that many stand-types have relatively short successional trajectories, suggesting limited change in forest canopy composition over time. There are two exceptions: in the jack pine - black spruce stand-type, black spruce will increase over time, and in the trembling aspen - paper birch - mountain maple stand-type, eastern deciduous species (green ash, American elm, Manitoba maple, and bur oak) are forecast to become increasingly dominant. We also describe a synoptic model of mixedwood boreal forest stand dynamics for the Riding Mountain area. The model includes a number of factors that we consider to be critical determinants of forest dynamics, such as seed source availability, small and large-scale disturbances, species life-history characteristics, and environmental gradients. Our succession model is more similar those described for eastern than western Canada, which may reflect the lower frequency of catastrophic fires in the Riding Mountain area compared to boreal forests further west. Our model emphasizes that successional trajectories do not converge towards a single self-perpetuating "climax". Instead, successional vectors may diverge, converge or remain cyclical, and multiple potential pathways are possible for each stand-type. Our results also illustrate that species assemblages, and the propensity for canopy change in the absence of fire, are governed by the cumulative and synergistic effects of climate, topography, disturbance frequency, size and intensity, edaphic conditions, and the proximity of parental seed sources. Fire suppression in the southern boreal forest has resulted in a paradigm shift in disturbance regime, from large, synchronous catastrophic fires to small-scale, asynchronous gap formation. A major challenge for boreal forest ecologists is to determine the long-term consequences of this paradigm shift on the composition, structure and health of boreal forest stands and landscapes.
The question whether and to what degree urbanization causes a decrease in diversity of animal and plant species and changes in community structure is still a matter of debate. While many studies used ground beetles, vertebrates, and butterflies as assumed model taxa, little work has been done with other, particularly insect, taxa. Here we report on rural and urban diversities of communities of carcass visiting destruent and predatory beetles (Coleoptera). From 8 rural and 2 city sites, we sampled 15323 destruent beetles representing 58 species and 1871 predators from 43 species. We observed a reduced diversity and changes in community structure of both beetle guilds towards the city. However, these changes were guild specific and our study gives no evidence that there are simple rules that govern rural and urban patterns of diversity. Species abundance distributions did not significantly differ between the study sites. There is also no evidence that the intermediate disturbance hypothesis might apply. Lastly, we found only little support for a homogenizing effect of urban environments on carrion visiting beetles.