Home ranges in moving habitats: polar bears and sea ice

Home range size estimates are often used to assess the amount of space required for animals to perform the activities essential for their survival and reproduction. However, in moving environments, traditional home range estimates may be ill suited to this task. In particular, traditional home range estimates are inaccurate representations of the space required by polar bears Ursus maritimus. The sea ice is the prime foraging platform of polar bears, and estimating the amount of ice encountered by bears may provide a better approximation of space use. We develop a technique to make these estimates. Our results confirm that polar bears use more space than terrestrial carnivores to find the resources and conditions they require. We also show that the traditional geographic home range can underestimate both the movement of bears and the amount of space encountered. Moreover, area of ice encountered increased with ice drift, indicating that bears living on highly mobile ice might be exposed to higher energetic costs, and potentially larger energetic gains, than bears inhabiting more stable ice. The methods and concepts presented here can serve as a foundation for new approaches to study the space use of the many species living in moving environments.     

The role of western Mediterranean islands in the evolutionary diversification of the spotted flycatcher Muscicapa striata,a long‐distance migratory passerine species

We investigated the evolutionary history of the spotted flycatcher Muscicapa striata, a long distance migratory passerine having a widespread range, using mitochondrial markers and nuclear introns. Our mitochondrial results reveal the existence of one insular lineage restricted to the western Mediterranean islands (Balearics, Corsica, Sardinia) and possibly to the Tyrrhenian coast of Italy that diverged from the mainland lineages around 1 Mya. Mitochondrial genetic distance between insular and mainland lineages is around 3.5%. Limited levels of shared nuclear alleles among insular and mainland populations further support the genetic distinctiveness of insular spotted flycatchers with respect to their mainland counterparts. Moreover, lack of mitochondrial haplotypes sharing between Balearic birds (M. s. balearica) and Corso‐Sardinian birds (M. s. tyrrhenica) suggest the absence of recent matrilineal gene flow between these two insular subspecies. Accordingly, we suggest that insular spotted flycatchers could be treated as one polytypic species (Muscicapa tyrrhenica) that differs from M. striata in morphology, migration, mitochondrial and nuclear DNA and comprises two subspecies (the nominate and M. t. balearica) that diverged recently phenotypically and in mitochondrial DNA and but still share the same nuclear alleles. This study provides an interesting case‐study illustrating the crucial role of western Mediterranean islands in the evolution of a passerine showing high dispersal capabilities. Our genetic results highlight the role of glacial refugia of these islands that allowed initial allopatric divergence of insular populations. We hypothesize that differences in migratory and breeding phenology may prevent any current gene flow between insular and mainland populations of the spotted flycatcher that temporarily share the same insular habitats during the spring migration.     

Competition and facilitation between Australian and Spanish legumes in seven Australian soils

This paper evaluates the relative performance and competitive ability of seven legumes from the Iberian Peninsula, Spain (one already invasive in Australia), grown singly or pairwise with seven legumes from south‐western Australia in their own soils. Indices of growth used were root, shoot and total mass and shoot dimensions. Water content, xylem water potential during drying and nodule production were also measured. The index of competition used was the intensity of competition coefficient (ICC), which is suitable for additive designs. The Australian species usually grew larger than the Spanish species, in their presence or absence, although the results were sensitive to the index of growth or resource capture used. The Australian legumes usually possessed greater total water content than the co‐occurring Spanish legumes. At least five Australian species were less reduced or not affected at all by inter‐regional competition compared with growth in isolation. Two Australian legumes performed relatively poorly in the presence of at least four Spanish legumes. The ICC identified many instances of growth promotion (facilitation) of the Australian species, which we attribute to extra nitrogen obtained through enhanced nodulation of both cohabiting species. Five of the seven Spanish species were outcompeted by the Australian species, whereas the growth of two was sometimes facilitated. Although the Spanish legumes had greater competitive ability in the more fertile Australian soils, they remained competitively inferior to the Australian legumes in their first season of growth and none is likely to displace the native legumes at this stage of growth. Longer‐term field studies are needed to fully evaluate the potential invasiveness of perennial legumes.     

Effects of light and temperature on seed germination of cacti of Brazilian ecosystems

Environmental factors are used by plants as spatio‐temporal indicators of favorable conditions for seed germination. Thus, the objective of this study was to determine the effect of light and temperature on seed germination of 30 taxa of Cactaceae occurring in northeastern Brazil and to evaluate whether fluctuations in temperature are capable of altering light sensitivity. The seeds were tested for germination under two light conditions (12 h photoperiod and continuous darkness) and 10 temperature treatments: eight constant temperatures (10, 15, 20, 25, 30, 35, 40 and 45°C) and two alternating temperatures (30/20°C and 35/25°C). The species studied showed two photoblastic responses. All cacti from the Cactoideae subfamily (22 taxa) were classified as positive photoblastic (i.e., no germination in darkness), regardless of the temperature treatment used. Likewise, temperature fluctuation did not alter the seed sensitivity to light. On the other hand, the species of the Opuntioideae (five taxa) and Pereskioideae (three taxa) subfamilies are indifferent to light (i.e., germinated both in the presence and absence of light). The cacti from the areas of Caatinga and Cerrado showed an optimal germination temperature of 30°C, while the species from Atlantic Forest and Restinga areas showed an optimal germination temperature of 25°C.     

Genome Characteristics,Phylogeny and Varying Host Specificity of Polish Kra and Ros Isolates of Tomato torrado virus

The genome sequences of two Polish Kra and Ros isolates of Tomato torrado virus (ToTV) were determined and compared with data of previously described ToTV isolates and other Torradovirus members. Whole‐genome sequence comparisons revealed 97.0–99.6% nucleotide sequence identities and close relatedness, with other known ToTV isolates. The high homology between Kra, Ros and Wal'03 ToTVs is likely responsible for the similar symptoms observed on infected plants. However, the symptoms differed in intensity and various host specificity. We report that Kra ToTV caused a milder expression of symptoms on Solanum tuberosum than Wal'03. We hypothesize this may be a result of the significant variability observed within the 3′‐UTR of RNA1 of Kra as well as of Ros ToTV isolates. In the light of this fact, potato may be considered an indicator plant for distinguishing Kra and Wal'03 ToTV isolates.     

Morphological,Molecular and Pathological Characterization of Phytophthora amaranthi sp. nov. from Amaranth in Taiwan

In the spring of 2007, a serious disease on amaranth was noticed in several farms in the major amaranth production area in central Taiwan. Abundant oospores were found in the disease tissues. A species of Phytophthora was consistently isolated from disease tissues. The organism formed abundant oospores with smooth walls and with amphigynous antheridia in single culture. Sporangia were partially deciduous with short‐ to medium‐length pedicels. Morphological characteristics of this organism did not match any reported Phytophthora species, and the organism was named Phytophthora amaranthi. Pathogenicity tests and molecular characterization confirmed the identity of the organism as a new pathogen of amaranth and a new species of Phytophthora.     

Sub-chronic iron overload triggers oxidative stress development in rat brain: implications for cell protection

This work was aimed to test the hypothesis that sub-chronic administration of iron-dextran (Fe-dextran) (six doses of 50 mg Fe-dextran/kg) to rats triggers a transient oxidative stress in brain and mechanisms of cellular antioxidant defence. After 2 h of administration of the 6th dose, a significant increase of total Fe, the labile Fe pool (LIP), the lipid radical (LR^?)/α-tocopherol (α-T) content ratio were observed, as compared to values in control brain homogenates. The ascorbyl radical (A^?)/ascorbate (AH^?) content ratio and the oxidation rate of 2′,7′-dichlorodihidrofluorescein (DCFH-DA) were significantly higher in Fe-dextran treated rats, as compared to values in brain from control rats after 4 h treatment. An increase in both catalase (CAT) and superoxide dismutase (SOD) activity was observed at 8 and 1–2 h, respectively. No significant changes were detected in the nuclear factor-κB (NF-κB) levels in nuclear extracts from rat brains after 1–8 h of Fe-dextran administration. After 2 h of Fe administration Fe concentration in cortex, striatum and hippocampus was significantly increased as compared to the same areas from control animals. Both, CAT and SOD activities were significantly increased in cortex after Fe administration over control values, without changes in striatum and hippocampus. Taken as a whole, sub-chronic Fe administration enhances the steady state concentration of Fe in the brain LIP that favors the settlement of an initial oxidative stress condition, both at hydrophilic and lipophilic compartments, resulting in cellular protection evidenced by antioxidant enzyme upregulation.     

Ornament size and colour as alternative strategies for effective communication in gliding lizards

Sexual ornamentation needs to be conspicuous to be effective in attracting potential mates and defending territories and indeed, a multitude of ways exists to achieve this. Two principal mechanisms for increasing conspicuousness are to increase the ornament's colour or brightness contrast against the background and to increase the size of the ornament. We assessed the relationship between the colour and size of the dewlap, a large extendible throat‐fan, across a range of species of gliding lizards (Agamidae; genus Draco) from Malaysia and the Philippines. We found a negative relationship across species between colour contrast against the background and dewlap size in males, but not in females, suggesting that males of different species use increasing colour contrast and dewlap size as alternative strategies for effective communication. Male dewlap size also increases with increasing sexual size dimorphism, and dewlap colour and brightness contrast increase with increasing sexual dichromatism in colour and brightness, respectively, suggesting that sexual selection may act on both dewlap size and colour. We further found evidence that relative predation intensity, as measured from predator attacks on models placed in the field, may play a role in the choice of strategy (high chromatic contrast or large dewlap area) a species employs. More broadly, these results highlight that each component in a signal (such as colour or size) may be influenced by different selection pressures and that by assessing components individually, we can gain a greater understanding of the evolution of signal diversity.