Species richness, resource availability, and disturbance are the primary factors considered in assessing the invasibility of plant communities. Nonetheless, the density of individuals in a community is a common and easy trait to measure. The ecological significance of the density of both native and invasive tree species was assessed using a systematic review and formal meta-analysis. The densities of recipient communities and invasive exotic tree species in novel ranges were identified in the published literature. In addition, we compared by means of a meta-analysis: (i) densities of invasive versus native species in invaded communities; (ii) densities of native species in invaded versus uninvaded communities; and (iii) densities of invasive species along distance gradients from initial locus of invasion. Invasive trees were found at higher densities than native species in recipient communities. Invasions by woody species were also recorded in communities with relatively low densities of natives suggesting that (i) low density forests may be more susceptible to invasion and/or (ii) density of the recipient community may be reduced during the invasion process. In addition, comparison of native species densities between invaded and uninvaded stands from the same community suggests that invasive trees negatively affect density of native trees once established. Therefore, the widely reported low density and often richness of native plants in invaded communities cannot be directly linked to ecosystem susceptibility to invasion without considering concomitant impacts. These findings suggest that density is a key preliminary determinant or factor which should be considered when assessing tree invasion dynamics.
Authors:G. Amori, S. Gippoliti, L. Luiselli, and C. Battisti
Changes in taxa composition among different communities in a landscape or along an environmental gradient are defined as β-diversity. From a biogeographic point of view, it is interesting to analyse patterns of β-turnover across latitudinal bands, and to understand whether P-diversity is significantly associated with endemism at lower latitudes, as predicted by theory. We inspected these issues by using squirrels (Rodentia, Sciuridae) as a study case. Distribution data for each genus were obtained from literature and mapped. The two hemispheres were subdivided into 23 latitudinal bands of equal area, and we calculated a β-turnover index between latitudinal bands with two formulae: Wilson and Shmida’s (1984) and Lennonetal.’s (2001) indices. We found that the peak of number of Sciuridae genera significantly corresponded to the peak in β-turnover scores at the same latitudes (25–31°N) with Wilson and Shmida’s (1984), but not with Lennon et al.’s (2001) index. We also found that the turnover between ground and tree squirrels corresponded to the grassland vegetation latitudinal bands (around 40° N), and the beginning of the latitudinal bands characterized by tropical and subtropical forests is accomplished with the occurrence of tree and flying squirrels
The importance of accurate species databases is debated in the recent literature of biodiversity assessment, considering that limited resources for conservation could be better allocated to assessment based on cost effective biodiversity features. I aimed to provide an understanding of sampling bias and provide practical advice to minimize bias either before or after data collection. I used 10×10 km
UTM grid data for 121 land snail species to account for geographic and taxonomic sampling bias in Hungary. Sampling intensity corrected for species richness varied significantly among regions, although regions were not good predictors of sampling intensity. Residuals were significantly autocorrelated in 15 km distance, indicating small scale heterogeneity in sampling intensity compared to species richness. Sampling coverage and intensity were higher close to human settlements and sampling intensity was higher within protected areas than outside. Commonness of species was positively associated with sampling intensity, while some rare species were over-represented in the records. Sampling intensity of microsnails (<3 mm) was significantly lower than that of the more detectable large species (>15 mm). Systematic effects of the collecting methods used in malacological research may be responsible for these differences. Understanding causes of sampling bias may help to reduce its effects in ecological, biogeographical and conservation biological applications, and help to guide future research.
Authors:A. Madinah, F. Abang, A. Mariana, M.T. Abdullah, and J. Mohd-Azlan
The literature regarding the diversity of ectoparasites and their interaction with their hosts remains largely inadequate in Malaysian tropical rainforest. We investigate the interaction patterns and specialization of ectoparasites infesting terrestrial small mammals (rodents and scandents) in Peninsular and Malaysian Borneo from samples made in 16 localities between 2008 and 2010. A total of 3,235 individuals of ectoparasites were collected during field surveys, resulting in an interaction network involving 47 ectoparasites that were distributed on 23 species of small mammals. The overall specialization index H2′ of all ectoparasites and host species was 0.67 which was considered moderate. Ticks appeared to be generalist with specialization index (H2′ = 0.35) while lice showed higher specialization (H2′ = 1) in selecting host species. The most diverse parasite assemblage was found on S. muelleri (Hs_w = 1.96). Specialization indices among ectoparasite species (dp) ranged from 0.03 to 1 while the indices among host species (dh) ranged from 0.20 to 1. Incomplete field data may have contributed to the high specialization indices. This study is significant as it can enhance our understanding the emergence and management of potential zoonotic diseases in Malaysia.
One of the greatest concerns in community ecology is to find how species composition patterns are related to different environmental and spatial conditions. This approach is especially interesting when applied to high diversity heterogeneous forests such as the Brazilian Atlantic Rainforest sensu lato. The present study aims to verify the existence of indicator species in four southern Atlantic Rainforest formations and identify relationships among distributions of tree species with environmental and spatial variables. For that, tree species density data of 21 phytosociological surveys were collected from the literature. The data were analyzed using indicator species and partial canonical redundancy analysis (partial RDA). Sandy coastal formation contained the greatest number of indicator species (17), followed by Atlantic rainforest (10), cloud forest (4) and Araucaria forest (3). The partial RDA analysis explained 22% of total data variation, of which 11% was assigned to the environment, 5% to space, 6% to spatial component of environmental influence, and 78% remained undetermined. The forest formations present different sets of indicator species suggesting replacement of species along the forest formations. The largest and significant fraction of variation in the composition and abundance of tree species explained by environmental variables reflects the heterogeneity and complexity of habitats throughout the region of Atlantic Forest. The low spatial influence and the environmental results indicate a pattern of structured communities due to different requirements of niches by species (niche theory).
A preliminary checklist of Tamaricaceae in the Indian subcontinent has been prepared on the basis of primary observations of different taxa belonging to this family in wild habitats and on secondary observations based on examining herbarium specimens and taxonomic literature. On the Indian subcontinent (comprising Bangladesh, Bhutan, Myanmar, Nepal, Pakistan, Sri Lanka and India), the family Tamaricaceae is poorly represented (20% of all species). The present paper deals with a brief review of distribution, endemism, possible fossil ancestry, economic potential and survival threat on existing taxa, etc. The present status of endemism of Tamaricaceae in Indian subcontinent (22.5% in 2002–2007) has been compared to the data of previous investigations (50% in 1939–1940) done in nineteenth century. The decreasing rate of endemism either indicates decreasing number of endemic taxa or increasing span of distribution of pan-endemic taxa belonging to this family. For better understanding of the functional aspects of species dynamics the rate of endemism in percent of a particular group of plants has been used as key index here.
A century ago, Alfred Nissle discovered that intentional intake of particular strains of Escherichia coli could treat patients suffering from infectious diseases. Since then, one of these strains became the most frequently used probiotic E. coli in research and was applied to a variety of human conditions. Here, properties of that E. coli Nissle 1917 strain are compared with other commercially available E. coli probiotic strains, with emphasis on their human applications. A literature search formed the basis of a summary of research findings reported for the probiotics Mutaflor, Symbioflor 2, and Colinfant. The closest relatives of the strains in these products are presented, and their genetic content, including the presence of virulence, genes is discussed. A similarity to pathogenic strains causing urinary tract infections is noticeable. Historic trends in research of probiotics treatment for particular human conditions are identified. The future of probiotic E. coli may lay in what Alfred Nissle originally discovered: to treat gastrointestinal infections, which nowadays are often caused by antibiotic-resistant pathogens.
Multivariate analysis of variance, based on randomization (permutation) test, has become an important tool for ecological data analyses. However, a comprehensive evaluation of the accuracy and power of available methods is still lacking. This is a thorough examination of randomization tests for multivariate group mean differences. With simulated data, the accuracy and power of randomization tests were evaluated using different test statistics in one-factor multivariate analysis of variance (MANOVA). The evaluations span a wide spectrum of data types, including specified and unspecified (field data) distributional properties, correlation structures, homogeneous to very heterogeneous variances, and balanced an unbalanced group sizes. The choice of test statistic strongly affected the results. Sums of squares between groups (Qb) computed on Euclidean distances (Qb-EUD) gave better accuracy. Qb on Bray-Curtis, Manhattan or Chord distances, the multiresponse permutation procedure (MRPP) and the sum of univariate ANOVA F produced severely inflated type I errors under increasing variance heterogeneity among groups, a common scenario in ecological data. Despite pervasive claims in the ecological literature, the evidence thus suggests caution when using test statistics other than Qb-EUD.
Authors:A. Wiater, J. Szczodrak, and M. Pleszczyńska
Conidia of TrichodermaharzianumF-340, an active producer of fungal mutanase, were mutagenized with physical and chemical mutagens used separately or in combination. After mutagenesis, the drop in conidia viability ranged from 0.004% to 71%. Among the applied mutagens, nitrosoguanidine gave the highest frequency of cultures with enhanced mutanase activity (98%). In total, 400 clones were isolated, and preliminarily evaluated for mutanase activity in flask microcultures. Eight most productive mutants were then quantified for mutanase production in shake flask cultures. The obtained results fully confirmed a great propensity of all the tested mutants to synthesize mutanase, the activity of which increased from 59 to 107% in relation to the parental T.harzianumculture. The best mutanase-overproducing mutant (T. harzianumF-340-48), obtained with nitrosoguanidine, produced the enzyme activity of 1.36 U/ml (4.5 U/mg protein) after 4 days of incubation in shake flask culture. This productivity was almost twices higher than that achieved by the initial strain F-340, and, at present, is the best reported in the literature. The potential application of mutanase in dentistry is also discussed.
This study is part of a general project to analyse the biological and ecological mechanisms that influence the invasion of Mediterranean sand dune ecosystems by alien plants. In this paper we analyse the morphological and functional traits of coastal dune wild species (natives and aliens) based mainly on information from the literature. The most common 130 wild species occurring on the recent (Holocenic) coastal dunes were included considering the invasive status of alien plants. A comparative analysis of functional groups was performed through ordination techniques (PCoA using the Gower index). This reveals four functional groups related to the most important plant communities in coastal vegetation zonation. Alien plants were found in all functional groups and no trait or set of traits was specifically related to them. This indicates that aliens show similar traits to those natives growing in different communities of the coastal dune zonation, from the small beach annuals to the evergreen taller shrubs of the Mediterranean macchia. When the invasive status of alien species was taken into account, however, some differences emerged: a) casual aliens were found in almost all groups but their traits were not interpreted as being due to any particular adaptive strategy; b) naturalised aliens were only found in the less fluctuating habitats of the inner coastal zones; c) invasive alien species were connected with two major plant strategies: annual invasive aliens (quick-to-mature low grasses and herbs) and perennial invasive aliens (taller and often strongly clonal).