Effects of Fragmentation and Sea-Level Changes upon Frog Communities of Land-Bridge Islands off the Southeastern Coast of Brazil

We investigate the composition of anuran communities of land-bridge islands off the southeastern coast of Brazil. These islands provide natural long-term experiments on the effects of fragmentation in the Brazilian Atlantic Forest (BAF). We hypothesize that Pleistocene sea-level changes, in combination with other abiotic variables such as area and habitat diversity, has affected anuran species richness and community composition on these islands. Data from the literature and collections databases were used to produce species lists for eight land-bridge islands and for the mainland adjacent to the islands. We assess the effects of area, number of breeding habitats and distance to the mainland upon anuran species richness on land-bridge islands. Additionally we use nestedness analysis to quantify the extent to which the species on smaller and less habitat-diverse islands correspond to subsets of those on larger and more diverse ones. We found that area has both direct and indirect effects on anuran species richness on land-bridge islands, irrespective of distance to the mainland. However, on islands with comparable sizes, differences in species richness can be attributed to the number and quality of breeding habitats. Anuran communities on these islands display a nested pattern, possibly caused by selective extinction related to habitat loss. Common lowland pond-breeders were conspicuous by their absence. In the BAF, the conservation of fragments with a high diversity of breeding habitats could compensate for the generally negative effect of small area upon species richness. We suggest that sea-level changes have an important role in shaping composition of anuran species on coastal communities.     

Ecological Stoichiometry and Density Responses of Plant-Arthropod Communities on Cormorant Nesting Islands

Seabirds deposit large amounts of nutrient rich guano on their nesting islands. The increased nutrient availability strongly affects plants and consumers. Consumer response differs among taxonomic groups, but mechanisms causing these differences are poorly understood. Ecological stoichiometry might provide tools to understand these mechanisms. ES suggests that nutrient rich taxa are more likely to be nutrient limited than nutrient poorer taxa and are more favored under nutrient enrichment. Here, we quantified differences in the elemental composition of soil, plants, and consumers between islands with and without nesting cormorant colonies and tested predictions made based on ES by relating the elemental composition and the eventual mismatch between consumer and resource stoichiometry to observed density differences among the island categories. We found that nesting cormorants radically changed the soil nutrient content and thereby indirectly plant nutrient content and resource quality to herbivores. In contrast, consumers showed only small differences in their elemental composition among the island categories. While we cannot evaluate the cause of the apparent homeostasis of invertebrates without additional data, we can conclude that from the perspective of the next trophic level, there is no difference in diet quality (in terms of N and P content) between island categories. Thus, bottom-up effects seemed mainly be mediated via changes in resource quantity not quality. Despite a large potential trophic mismatch we were unable to observe any relation between the invertebrate stoichiometry and their density response to nesting cormorant colonies. We conclude that in our system stoichiometry is not a useful predictor of arthropod responses to variation in resource nutrient content. Furthermore, we found no strong evidence that resource quality was a prime determinant of invertebrate densities. Other factors like resource quantity, habitat structure and species interactions might be more important or masked stoichiometric effects.     

Phylogeography and Conservation Genetics of the Common Wall Lizard,Podarcis muralis,on Islands at Its Northern Range

Populations at range limits are often characterized by lower genetic diversity, increased genetic isolation and differentiation relative to populations at the core of geographical ranges. Furthermore, it is increasingly recognized that populations situated at range limits might be the result of human introductions rather than natural dispersal. It is therefore important to document the origin and genetic diversity of marginal populations to establish conservation priorities. In this study, we investigate the phylogeography and genetic structure of peripheral populations of the common European wall lizard, Podarcis muralis, on Jersey (Channel Islands, UK) and in the Chausey archipelago. We sequenced a fragment of the mitochondrial cytochrome b gene in 200 individuals of P. muralis to infer the phylogeography of the island populations using Bayesian approaches. We also genotyped 484 individuals from 21 populations at 10 polymorphic microsatellite loci to evaluate the genetic structure and diversity of island and mainland (Western France) populations. We detected four unique haplotypes in the island populations that formed a sub-clade within the Western France clade. There was a significant reduction in genetic diversity (H_O, H_E and A_R) of the island populations in relation to the mainland. The small fragmented island populations at the northern range margin of the common wall lizard distribution are most likely native, with genetic differentiation reflecting isolation following sea level increase approximately 7000 BP. Genetic diversity is lower on islands than in marginal populations on the mainland, potentially as a result of early founder effects or long-term isolation. The combination of restriction to specific localities and an inability to expand their range into adjacent suitable locations might make the island populations more vulnerable to extinction.     

Breeding of the bellbird on the Poor Knights Islands,New Zealand

Abstract

The breeding of the bellbird (Anthornis melanura) was studied intensively over three seasons on Aorangi Island, Poor Knights Islands. Adult males defended territories all year but ventured beyond them to exploit localised food resources and to obtain water; some adults defended the same territory for at least 5 years. Adult females shared a territory with a male only during the breeding season. At other times of the year adult females were joined by juveniles and immatures and formed feeding flocks. The breeding season extended from late September to late December. A few nests were built on the ground but most were in dense vegetation, usually near the canopy. Peak egg-laying extended from mid-October to mid-November and only one clutch of two to four eggs was laid. Nest building and incubation were completed by the female alone but both parents fed nestlings. Fledglings stayed in the vicinity of the nest for several days, and were fed by both parents. Incubation and nestling periods were about 15 and 19 days respectively. Comparisons are made with the breeding biology of bellbirds and other native passerines on mainland New Zealand, and the importance of the predator-free enviomment of the Poor Knights Islands is stressed.     

Bird Communities of the Arctic Shrub Tundra of Yamal: Habitat Specialists and Generalists

Background

The ratio of habitat generalists to specialists in birds has been suggested as a good indicator of ecosystem changes due to e.g. climate change and other anthropogenic perturbations. Most studies focusing on this functional component of biodiversity originate, however, from temperate regions. The Eurasian Arctic tundra is currently experiencing an unprecedented combination of climate change, change in grazing pressure by domestic reindeer and growing human activity.

Methodology/Principal Findings

Here we monitored bird communities in a tundra landscape harbouring shrub and open habitats in order to analyse bird habitat relationships and quantify habitat specialization. We used ordination methods to analyse habitat associations and estimated the proportions of specialists in each of the main habitats. Correspondence Analysis identified three main bird communities, inhabiting upland, lowland and dense willow shrubs. We documented a stable structure of communities despite large multiannual variations of bird density (from 90 to 175 pairs/km²). Willow shrub thickets were a hotspot for bird density, but not for species richness. The thickets hosted many specialized species whose main distribution area was south of the tundra.

Conclusion/Significance

If current arctic changes result in a shrubification of the landscape as many studies suggested, we would expect an increase in the overall bird abundance together with an increase of local specialists, since they are associated with willow thickets. The majority of these species have a southern origin and their increase in abundance would represent a strengthening of the boreal component in the southern tundra, perhaps at the expense of species typical of the subarctic zone, which appear to be generalists within this zone.     

Genetic Network and Breeding Patterns of a Sicklefin Lemon Shark (Negaprion acutidens) Population in the Society Islands,French Polynesia

Human pressures have put many top predator populations at risk of extinction. Recent years have seen alarming declines in sharks worldwide, while their resilience remains poorly understood. Studying the ecology of small populations of marine predators is a priority to better understand their ability to withstand anthropogenic and environmental stressors. In the present study, we monitored a naturally small island population of 40 adult sicklefin lemon sharks in Moorea, French Polynesia over 5 years. We reconstructed the genetic relationships among individuals and determined the population’s mating system. The genetic network illustrates that all individuals, except one, are interconnected at least through one first order genetic relationship. While this species developed a clear inbreeding avoidance strategy involving dispersal and migration, the small population size, low number of breeders, and the fragmented environment characterizing these tropical islands, limits its complete effectiveness.     

Patterns in the benthic communities on the shelf of the sub-Antarctic Prince Edward Islands

Summary Benthic communities at the sub-Antarctic Prince Edward Islands were sampled qualitatively with an epi-benthic sled at 57 stations over a five year period. Additional information on these communities was obtained from replicate underwater photographs. In total, 546 macrofaunal species were found. Despite the extreme isolation and geological youth of the islands, there seems to have been a diverse colonisation. A cluster-analysis based on species abundance aggregated most stations into 8 groups. Each of these groups had a unique depth and substratum combination. Thourella variabilis (Octocoralea), and Cabarea darwinii (Bryozoa) characterised deep rocky assemblages and Serpula vermicularis, Lanice conchilega (Polychaeta) and Magellania kerguelenensis (Brachiopoda) characterised soft substrata. Indicator species separating each of the 8 clusters are given. Trends in percentage cover and densities of major taxa with respect to depth and substratum, as shown by photographs, are described. Deep, rocky substrata were dominated by Porifera, Bryozoa and Cnidaria, while soft-substrata were dominated by Polychaeta, Bivalvia and Brachiopoda. Errant forms consisted predominantly of Echinodermata, with Crustacea being important in shallower habitats. Filter-feeders dominated the benthos of the islands in all habitats.     

Norepinephrine Turnover in the Hypothalamus of Adult Male Rats: Alteration of Circadian Patterns by Semistarvation

Norepinephrine (NE) turnover, as estimated by 3-methoxy-4-hydroxyphenylethyleneglycol concentration, was studied in the mediobasal hypothalamus of control and semistarved adult male rats at eight time points of a 24-h period. The marked circadian periodicity of NE turnover with a peak in the dark phase in control rats is completely suppressed in semistarved rats. The average 24-h concentration of the NE precursor tyrosine in brain and of tyrosine flow into brain (calculated from plasma amino acid concentrations) is reduced in semistarved rats, but both brain tyrosine and tyrosine flow show continuing circadian fluctuations.     

Patterns of introduction of non-indigenous non-marine snails and slugs in the Hawaiian Islands

The native snails of the Hawaiian Islands are disappearing. One cause is predation by introduced carnivorous snails. Habitat destruction/modification is also important, facilitating the spread of other non-indigenous snails and slugs. Eighty-one species of snails and slugs are recorded as having been introduced. Thirty-three are established: 12 freshwater, 21 terrestrial. Two or three species arrived before western discovery of the islands (1778). During the nineteenth century about one species per decade, on average, was introduced. The rate rose to about four per decade during the twentieth century, with the exception of an especially large number introduced in the 1950s as putative biocontrol agents against the giant African snail, Achatina fulica. The geographical origins of these introductions reflect changing patterns of commerce and travel. Early arrivals were generally Pacific or Pacific rim species. Increasing trade and tourism with the USA, following its annexation of Hawaii, led to an increasing proportion of American species. More general facilitation of travel and commerce later in the twentieth century led to a significant number of European species being introduced. African species dominated the 1950s biological control introductions. The process continues and is just part of the homogenization of the unique faunas of tropical Pacific islands.     

Submarine Hydrothermal Vents of the Aeolian Islands: Relationship Between Microbial Communities and Thermal Fluids

The relationship between fluid geochemistry and microbial communities was investigated for shallow (< 25 m) submarine hydrothermal vents in the Aeolian Islands (Southern Italy). Thermal waters, gases, and deposits of white filamentous material were collected from 11 sites. The geochemical analyses showed a magmatic component was present in all sampled fluids. The total microbial abundances, evaluated as direct counts of picoplanktonic cells (ranging from 0.2 to 2 mu m in diameter), were between 1.55 107 and 4.18 108 cells per liter. Picophytoplankton (total autofluorescent cells) ranged from 9.6 105 to 7.88 106 cells per liter. Yellow-orange autofluorescent prokaryotes belonging to the cyanobacteria were more abundant than red autofluorescent eukaryotic cells. Chemolithoautotrophic, sulfur-oxidizing, rod-shaped Bacteria were isolated from venting water samples and identified as Thiobacillus -like. Microscopic examination of the white mat deposits showed the presence of filamentous microorganisms.     

Transient Changes in Bacterioplankton Communities Induced by the Submarine Volcanic Eruption of El Hierro (Canary Islands)

The submarine volcanic eruption occurring near El Hierro (Canary Islands) in October 2011 provided a unique opportunity to determine the effects of such events on the microbial populations of the surrounding waters. The birth of a new underwater volcano produced a large plume of vent material detectable from space that led to abrupt changes in the physical-chemical properties of the water column. We combined flow cytometry and 454-pyrosequencing of 16S rRNA gene amplicons (V1–V3 regions for Bacteria and V3–V5 for Archaea) to monitor the area around the volcano through the eruptive and post-eruptive phases (November 2011 to April 2012). Flow cytometric analyses revealed higher abundance and relative activity (expressed as a percentage of high-nucleic acid content cells) of heterotrophic prokaryotes during the eruptive process as compared to post-eruptive stages. Changes observed in populations detectable by flow cytometry were more evident at depths closer to the volcano (~70–200 m), coinciding also with oxygen depletion. Alpha-diversity analyses revealed that species richness (Chao1 index) decreased during the eruptive phase; however, no dramatic changes in community composition were observed. The most abundant taxa during the eruptive phase were similar to those in the post-eruptive stages and to those typically prevalent in oceanic bacterioplankton communities (i.e. the alphaproteobacterial SAR11 group, the Flavobacteriia class of the Bacteroidetes and certain groups of Gammaproteobacteria). Yet, although at low abundance, we also detected the presence of taxa not typically found in bacterioplankton communities such as the Epsilonproteobacteria and members of the candidate division ZB3, particularly during the eruptive stage. These groups are often associated with deep-sea hydrothermal vents or sulfur-rich springs. Both cytometric and sequence analyses showed that once the eruption ceased, evidences of the volcano-induced changes were no longer observed.     

A Method for Separating Cuticular and Stomatal Components of Gas Exchange by Amphistomatous Leaves: I MODEL SOLUTION

A new technique for estimating the cuticular component of epidermalgas exchange by a stomatous leaf side is proposed. It is basedon the process of elimination of stomatal diffusion by mass(viscous) flow of air applying an air pressure gradient acrossthe leaf. This technique was designed to enable a reliable estimationof the cuticular component irrespective of stomatal opening. A model solution of diffusive and mass flow counteraction interms of general substance fluxes is presented. Water vapourloss and CO₂ uptake by a model leaf was simulated by varyingboth stomatal diffusion resistance and viscous flow of air throughthe stomatal pores in physiologically and experimentally relevantranges. Depending on stomatal opening, elimination of the stomatalcontribution to epidermal vapour and CO₂ exchange by the viscousflow of air ranged from small to practically complete. It supportsthe relevance of the procedure for cuticular vapour loss estimationunder conditions of partially open stomata. Modification of the model CO₂-uptake patterns due to expectedchanges in intercellular CO₂ concentration, , was evaluated. Net CO₂ flux under the diffusive-viscous flowscounteraction is sensitive to the changes mentioned above. Nevertheless,the changes in , evaluated by a simple model, were too small to cause significant departures from the CO₂-uptakeelimination curves by constant . The relevance of the method for the determination of cuticular CO₂-uptakeis discussed. Key words: Cuticular transpiration, cuticular CO₂-uptake, methods, diffusive-viscous flows counteraction, model     

Plant and Bird Presence Strongly Influences the Microbial Communities in Soils of Admiralty Bay,Maritime Antarctica

Understanding the environmental factors that shape microbial communities is crucial, especially in extreme environments, like Antarctica. Two main forces were reported to influence Antarctic soil microbes: birds and plants. Both birds and plants are currently undergoing relatively large changes in their distribution and abundance due to global warming. However, we need to clearly understand the relationship between plants, birds and soil microorganisms. We therefore collected rhizosphere and bulk soils from six different sampling sites subjected to different levels of bird influence and colonized by Colobanthus quitensis and Deschampsia antarctica in Admiralty Bay, King George Island, Maritime Antarctic. Microarray and qPCR assays targeting 16S rRNA genes of specific taxa were used to assess microbial community structure, composition and abundance and analyzed with a range of soil physico-chemical parameters. The results indicated significant rhizosphere effects in four out of the six sites, including areas with different levels of bird influence. Acidobacteria were significantly more abundant in soils with little bird influence (low nitrogen) and in bulk soil. In contrast, Actinobacteria were significantly more abundant in the rhizosphere of both plant species. At two of the sampling sites under strong bird influence (penguin colonies), Firmicutes were significantly more abundant in D. antarctica rhizosphere but not in C. quitensis rhizosphere. The Firmicutes were also positively and significantly correlated to the nitrogen concentrations in the soil. We conclude that the microbial communities in Antarctic soils are driven both by bird and plants, and that the effect is taxa-specific.     

Land-Bridge Calibration of Molecular Clocks and the Post-Glacial Colonization of Scandinavia by the Eurasian Field Vole Microtus agrestis

Phylogeography interprets molecular genetic variation in a spatial and temporal context. Molecular clocks are frequently used to calibrate phylogeographic analyses, however there is mounting evidence that molecular rates decay over the relevant timescales. It is therefore essential that an appropriate rate is determined, consistent with the temporal scale of the specific analysis. This can be achieved by using temporally spaced data such as ancient DNA or by relating the divergence of lineages directly to contemporaneous external events of known time. Here we calibrate a Eurasian field vole (Microtus agrestis) mitochondrial genealogy from the well-established series of post-glacial geophysical changes that led to the formation of the Baltic Sea and the separation of the Scandinavian peninsula from the central European mainland. The field vole exhibits the common phylogeographic pattern of Scandinavian colonization from both the north and the south, however the southernmost of the two relevant lineages appears to have originated in situ on the Scandinavian peninsula, or possibly in the adjacent island of Zealand, around the close of the Younger Dryas. The mitochondrial substitution rate and the timescale for the genealogy are closely consistent with those obtained with a previous calibration, based on the separation of the British Isles from mainland Europe. However the result here is arguably more certain, given the level of confidence that can be placed in one of the central assumptions of the calibration, that field voles could not survive the last glaciation of the southern part of the Scandinavian peninsula. Furthermore, the similarity between the molecular clock rate estimated here and those obtained by sampling heterochronous (ancient) DNA (including that of a congeneric species) suggest that there is little disparity between the measured genetic divergence and the population divergence that is implicit in our land-bridge calibration.     

A Method for Separating Cuticular and Stomatal Components of Gas Exchange by Amphistomatous Leaves: II. EXPERIMENTAL SOLUTION

The apparent cuticular component of transpiration of stomatabearing leaf epidermis was estimated by restricting stomataldiffusion by mass flow of air in the opposite direction. Thiswas achieved by applying an air pressure gradient across theamphistomatous leaf. Some assumptions of the previously suggestedmethod (antrcek and Slav?k, 1990) were experimentally verifiedusing maize leaves. The technique makes possible a quantitativeestimation of cuticular water loss including that of the externalperistomatal (i.e. vapour not passing through the pores) andthe respective conductance when the stomata are partially open. In addition to the fact that the cuticular portion of the totalleaf vapour loss (i.e. relative cuticular transpiration) dependson stomatal opening, even the absolute value of apparent cuticulartranspiration was (1) increased by lower vapour pressure deficitand (2) decreased with closing stomata. These changes, inducedby variations in a vapour pressure deficit of 2.45?0.35 kPa,ranged between 0.66?0.14µg cm ^–2 s^–1. Theabsolute value of apparent cuticular transpiration changed onaverage by a factor of 2.3 due to stomata opening or closingwhich was induced by turning the light on or by exogenous ABAapplication. Possible interference by residual vapour diffusingthrough the stomatal pore was evaluated by the model application.An attempt was also made to assess the cuticular component ofCO₂-uptake rate. Experimental results are discussed in contextwith the feedforward response of stomata to air humidity. Key words: Cuticular transpiration, cuticular CO₂-uptake, feedforward response, maize     

Influence of Winter Ranging Behaviour on the Social Organization of a Cooperatively Breeding Bird Species, The Apostlebird

Most cooperative breeding bird species live in family groups that are formed through the prolonged association of offspring with their parents. Research into cooperative families has in particular investigated the balance between cooperation and conflict over reproductive decisions. As a consequence of this research focus, social interactions among group members outside the breeding season are rarely studied, despite the fact that they are likely to be crucial for social decisions. We investigated the social dynamics and ranging behaviour of the family group living cooperatively breeding apostlebird ( Struthidea cinerea ) outside the breeding season. Group size changed between, but not within, the seasons, being smaller during the breeding season than in the winter season. This change in group size was a consequence of breeding groups merging after breeding, then splitting again before the next breeding season. While breeding groups used small, non-overlapping home ranges (      = 113 ha) around the nesting site, during winter groups moved up to 1200 ha (      = 598 ha), and interacted frequently with up to four other winter groups. In particular large groups often joined together during winter and spent up to 50% of their time associating with other large winter groups. This apparent fission-fusion system facilitated the exchange of group members, offering the possibility to form new breeding coalitions and new groups. The results of this study suggest that behaviour outside the breeding season can be of considerable importance to the social dynamics of both families and cooperative breeding in such systems.     

Effect of Incubation on Bacterial Communities of Eggshells in a Temperate Bird,the Eurasian Magpie (Pica pica)

Inhibitory effect of incubation on microbial growth has extensively been studied in wild bird populations using culture-based methods and conflicting results exist on whether incubation selectively affects the growth of microbes on the egg surface. In this study, we employed culture-independent methods, quantitative PCR and 16S rRNA gene pyrosequencing, to elucidate the effect of incubation on the bacterial abundance and bacterial community composition on the eggshells of the Eurasian Magpie (Pica pica). We found that total bacterial abundance increased and diversity decreased on incubated eggs while there were no changes on non-incubated eggs. Interestingly, Gram-positive Bacillus, which include mostly harmless species, became dominant and genus Pseudomonas, which include opportunistic avian egg pathogens, were significantly reduced after incubation. These results suggest that avian incubation in temperate regions may promote the growth of harmless (or benevolent) bacteria and suppress the growth of pathogenic bacterial taxa and consequently reduce the diversity of microbes on the egg surface. We hypothesize that this may occur due to difference in sensitivity to dehydration on the egg surface among microbes, combined with the introduction of Bacillus from bird feathers and due to the presence of antibiotics that certain bacteria produce.