Interspecific Variation

Leaf thickness plays an important role in leaf and plant functioning, and relates to a species' strategy of resource acquisition and use. As such, it has been widely used for screening purposes in crop science and community ecology. However, since its measurement is not straightforward, a number of estimates have been proposed. Here, the validity of the (SLA x LDMC)(-1) product is tested to estimate leaf thickness, where SLA is the specific leaf area (leaf area/dry mass) and LDMC is the leaf dry matter content (leaf dry mass/fresh mass). SLA and LDMC are two leaf traits that are both more easily measurable and often reported in the literature. The relationship between leaf thickness (LT) and (SLA x LDMC)(-1) was tested in two analyses of covariance using 11 datasets (three original and eight published) for a total number of 1039 data points, corresponding to a wide range of growth forms growing in contrasted environments in four continents. The overall slope and intercept of the...

Several volatile allelochemicals were identified and characterized from fresh leaf tissue of three distinct populations of the invasive perennial weed, mugwort (Artemisia vulgaris). A unique bioassay was used to demonstrate the release of volatile allelochemicals from leaf tissues. Leaf volatiles were trapped and analyzed via gas chromatography coupled with mass spectrometry. Some of the components identified were terpenes, including camphor,

Recent studies have shown that the complementary analysis of mercury (Hg) concentrations and stable isotopic ratios of nitrogen (δ15N) and carbon (δ13C) can be useful for investigating the trophic influence on the Hg exposure and accumulation in marine top predators. In this study, we propose to evaluate the interspecies variability of Hg concentrations in phocids from polar areas and to

RAPD markers were used to study variation among 20 taxa in the genus OROBANCHE: O. alba, O. amethystea, O. arenaria, O. ballotae, O. cernua, O. clausonis, O. cumana, O. crenata, O. densiflora, O. foetida, O. foetida var. broteri, O. gracilis, O. haenseleri, O. hederae, O. latisquama, O. mutelii, O. nana, O. ramosa, O. rapum-genistae and O. santolinae. A total of 202 amplification products generated with five arbitrary RAPD primers was obtained and species-specific markers were identified. The estimated Jaccard's differences between the species varied between 0 and 0.864. The pattern of interspecific variation obtained is in general agreement with previous taxonomic studies based on morphology, and the partition into two different sections (Trionychon and Orobanche) is generally clear. However, the position in the dendrogram of O. clausonis did not fit this classification since it clustered with members of section TRIONYCHON: Within this section, O. arenaria was relatively isolat...

Pitcher plants of the genusNepenthesattract and trap invertebrate prey using nectar-secreting pitchers. Pitcher morphology and spectral reflectance characteristics were investigated for sixNepenthesspecies from northwest Borneo (N. albomarginata, N. ampullaria, N. bicalcarata, N. gracilis, N. mirabilisvar.echinostomaandN. rafflesiana). Morphological measurements focused on the size of the pitcher rim (or peristome, the site of the major nectaries) in relation to pitcher length. The results show considerable interspecific variation in morphology. Spectral reflectance measurements quantified the degree of colour contrast between the peristome and pitcher body, from ultraviolet (UV) to red wavelengths. The contrast maxima for each species were compared with insect visual sensitivity maxima. The six species showed a wide range of reflectance patterns, with pitchers ofN. rafflesianapossessing the greatest degree of ‘fit’ between contrast maxima and insect sensitivity maxima, in the UV, blue and green regions of the spectrum. Based on the morphological and reflectance analyses, we hypothesized that pitchers ofN. rafflesianawould be more attractive to anthophilous (flower-visiting) invertebrates than the sympatricN. gracilis. Analysis of prey contents generally supported the hypothesis, suggesting possible interspecific resource partitioning. Morphological and spectral characteristics of the other species are discussed in relation to published studies on prey capture by those species.

Recent decades have seen a major surge in the study of interspecific variation in functional traits in comparative plant ecology, as a tool to understanding and predicting ecosystem functions and their responses to environmental change. However, this research has been biased almost exclusively towards vascular plants. Very little is known about the role and applicability of functional traits of non-vascular cryptogams, particularly bryophytes and lichens, with respect to biogeochemical cycling. Yet these organisms are paramount determinants of biogeochemistry in several biomes, particularly cold biomes and tropical rainforests, where they: (1) contribute substantially to above-ground biomass (lichens, bryophytes); (2) host nitrogen-fixing bacteria, providing major soil N input (lichens, bryophytes); (3) control soil chemistry and nutrition through the accumulation of recalcitrant polyphenols (bryophytes) and through their control over soil and vegetation hydrology and temperatures; ...

Large interspecific differences exist in the potential relative growth rate (RGR) of plants. Which physio- logical, morphological, chemical and/or allocation-related factors explain this variation in growth rate? In a first experiment growth of eight herbaceous wild species was analysed, varying twofold in RGR. No correlation was found between RGR and the rate of photosynthesis per unit leaf area. The growth

The genus Tulasnella comprises important orchid mycobionts. Molecular phylogenetic studies on nrITS-5.8S sequences of Tulasnella species previously isolated from mycorrhizas of epiphytic orchids from a tropical Andean forest showed genomic variability among clones which was difficult to interpret as intra- or interspecific variations or to correlate with described Tulasnella species. To improve this situation, we collected basidiomata of Tulasnella in an Andean forest, studied part of the sequences of fungal ribosomal genes and correlated molecular data with the morphology of the specimens. Within five basidiomata displaying slight morphological variability, we found inter-specimen nrITS1-5.8S-ITS2 variability corresponding to proportional differences of less than 1% except for one clone with 5.1% divergence. Results indicate that the slightly variable basidiomata should be considered as one species, which is morphologically tentatively assigned to the Tulasnella pruinosa complex. However, comparison of nrITS1-5.8S-ITS2 sequences, including sequences of T. pruinosa from other origins, indicate that Tulasnella sp. is only distantly related to the T. pruinosa specimens included in the analyses. Sequences of all morphologically similar and taxonomically well-identified species are required to decide whether the basidiomata analyzed in the present study represent a new species. The new sequences are rather similar to sequences obtained previously from mycorrhizae of epiphytic orchids of the same area indicating mycorrhizal potential of this fungus.

Intraspecific and interspecific variations have been observed across many taxa with respect to resistance to natural environmental stressors. It has already been well documented that amphibians are sensitive to habitat degradation and are regarded as bioindicators of aquatic and agricultural ecosystems. In southern Spain, different toxic substances, including copper sulphate, which is used to control Cycloconium oleaginum (Fungi, Ascomycota, Venturiaceae) during spring and autumn, are used in intensive olive tree agriculture. In this context, many wetlands are affected by a diffuse pollution process. Thus, toxicological studies using different species living in wetlands surrounded by agricultural activity are needed to understand the alterations suffered by these ecosystems. To achieve this understanding, individuals of five amphibian species (Bufo bufo, Epidalea calamita, Discoglossus jeanneae, Pelobates cultripes, and Pelophylax perezi) at Gosner developmental stages 19 and 25 were exposed to different copper sulphate concentrations in 96 h acute toxicity tests. Exposure to copper sulphate had a negative effect on total larval length reached at the end of the experimental period and generated approximately 30% of growth reduction respect to control treatments. P. perezi was the most tolerant species studied and showed no mortality at the maximum concentration tested (0.20 mg Cu L−1), whereas the most sensitive species (B. bufo, E. calamita, and D. jeanneae) showed approximately 90% mortality at the same concentration. These results indicates that the sole presence in wetlands of P. perezi, the most abundant species in southeast of Iberian Peninsula, might be correlated with its high tolerance to agrochemicals.

... NATIVE RODENTS IN SOUTHEASTERN AUSTRALIA Sharon J. Downes,* Kathrine A. HandasydeMark A. Elgar ... Ageclasses of mam mals were defined by body weight and reproductive condition (Tanton, 1969 ... a key predator of the eggs of small birds (Major Gowing, 1994), and ...