Does genetic variation and gene flow vary with rarity in obligate seeding Persoonia species (Proteaceae)?

Theory predicts that genetic variation is a determinant of persistence, and that the abundance and distribution of variation is strongly dependent on genetic drift and gene flow. Small, isolated populations are expected to be less diverse and more differentiated than large, inter-connected populations. Thus rare species may be more at risk of extinction. We used 389 putative AFLP loci to compare genetic variation and structuring in two pairs of closely-related common (large populations geographically widespread) and rare (small populations spatially restricted) Persoonia species. We genotyped 15–22 adult plants, from four populations, covering the geographic range of each species. Although genetic diversity was low for all four species (for long-lived outcrossing perennials), we found significantly more diversity within populations of the rare species than within those of the common species. AMOVA revealed significant levels of structure both among species (21%) and populations (15%). The proportion of inter-population variation within species did not vary consistently with rarity (Pair 1 rare 21.1% versus common 16.5%; Pair 2 rare 15.8% versus common 20.6%). However populations of the rare species were more differentiated than common species with similar geographic separation, suggesting greater gene flow between populations of the common species. Therefore, even relatively small genetically isolated populations of rare Persoonia species were more diverse than large populations of common Persoonia species. We hypothesise that common Persoonia species have undergone a rapid range expansion from a narrow gene pool, while genetic diversity is maintained in the soil seed-bank of rare remnants.     

Does phenotypic plasticity in carboxylate exudation differ among rare and widespread Banksia species (Proteaceae)?

Banksia species (Proteaceae) occur on some of the most phosphorus (P)-impoverished soils in the world. We hypothesized that plasticity in the exudation of P-mobilizing carboxylates would be greater in widespread than in rare Banksia species. Glasshouse experiments were conducted to identify and quantify carboxylate exudation in three widespread and six narrowly distributed Banksia species. High concentrations of carboxylates (predominantly malate, citrate, aconitate, oxalate) were measured in the rhizosphere of all nine species of Banksia on six different soils, but widespread species did not have greater plasticity in the composition of exuded carboxylates. Based on the evidence in the present study, rarity in Banksia cannot be explained by limited phenotypic adjustment of carboxylate exudation.     

How widespread are recruitment bottlenecks in fragmented populations of the savanna tree Banksia marginata (Proteaceae)?

Plant Ecology - Land clearing of habitat into smaller, isolated remnants is a major driver of plant and animal extinctions globally. In southeastern Australia, once widespread temperate savannas...     

Are breeding system and florivory associated with the abundance of Tillandsia species (Bromeliaceae)?

Plant species abundance is partly determined by reproductive success and the factors that limit this success. We studied the flowering phenology, breeding systems and florivory in a community of seven epiphytic Tillandsia spp. in a tropical dry forest in central Mexico. Flowering periods were distributed throughout the year, and corolla sizes suggested that most species share pollinators. The most common breeding system was self‐incompatibility (Tillandsia achyrostachys, T. caput‐medusae and T. hubertiana), T. lydiae was infertile, T. circinnatioides was partially self‐compatible and T. recurvata and T. schiedeana were self‐compatible with high autonomous self‐pollination. Floral morphology suggests that delayed selfing occurs in the autonomous self‐pollinated species, and separation between stigma and stamens could result in self‐pollination in the remaining species being avoided. Less than 5% of the inflorescences in the most abundant species (T. recurvata) suffered damage by florivores, but > 40% of inflorescences were damaged in the other species. In damaged inflorescences, fruit set decreased by up to 89%. Our data show that the dominant species (T. recurvata) is autogamous and its reproductive success is slightly reduced by resource constraints and florivory. In the less abundant species, resource limitation and florivory dramatically reduced reproductive success, but the strength of these limiting factors is season dependent. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 50–65.     

Are there real differences among aquatic and terrestrial food webs?

Recently, aquatic and terrestrial ecologists have put forward several hypotheses regarding similarities and differences in food-web structure and function among these ecosystem types. Although many of these hypotheses explore why strong top-down effects and trophic cascades might be less common in terrestrial than in aquatic ecosystems, there is little theoretical or empirical evidence available to support or refute these hypotheses. Many unanswered questions remain about potential differences across ecosystem types: progress will require empirical studies designed within a broader context that allows for more direct comparisons.     

Are differences in productivity between native and exotic trees in N.W. Patagonia related to differences in hydraulic conductance?

Afforestation with the exotic Pinus ponderosa is currently taking place within the natural distributional area of Austrocedrus chilensis, a native conifer of N.W. Patagonia. Annual productivity of the exotic species is double the productivity of the native one. In order to test the hypothesis that these differences in productivity are, at least in part, due to differences in hydraulic characteristics of both species, we measured or estimated several ecophysiological variables in A. chilensis and P. ponderosa trees growing in the same place. Water use (WU) and diameter growth were lower in A. chilensis than in P. ponderosa. Although predawn water potential was relatively constant during the whole growing season, A. chilensis trees showed lower values of this variable than P. ponderosa in a very dry period, suggesting different water sources. Under field conditions, canopy-stomatal (gs) and whole hydraulic conductances, specific hydraulic conductivity and photosynthetic rate (A) were lower in A. chilensis than P. ponderosa. In contrast, instantaneous WU efficiency was higher in A. chilensis than in P. ponderosa. However, gs and A in A. chilensis significantly increased in cut branches of this species suggesting hydraulic limitations on photosynthesis. We hypothesize that hydraulic characteristics of P. ponderosa permit high stomatal conductance for more hours a day than A. chilensis trees, without reaching threshold values of water potential. This can explain, at least in part, differences in C fixation and thus, in productivity between species. In addition, our results suggested a secondary limitation to C fixation in A. chilensis at the photosynthetic apparatus.     

Morphometric and molecular differences among Calvertius tuberosus (Coleoptera: Curculionidae) populations associated with Andean and coastal populations of Araucaria araucana in the La Araucanía Region,Chile

Calvertius tuberosus (Curculionidae) lives exclusively on Araucaria araucana trees (commonly known as pehuen) in southern Chile. In this study, morphometric and molecular genetic analyses of Andean and coastal populations of C. tuberosus were performed to evaluate evolutionary divergence associated with the discontinuity of the Araucaria forest between the coastal and Andean regions. Specimens of C. tuberosus were collected in Nahuelbuta National Park, Villa Las Araucarias, and Malalcahuello National Reserve and were classified and stored at the Animal Biotechnology Researching Laboratory (LINBA), University of La Frontera, Temuco, Chile. Thirteen morphometric parameters and the expression patterns of ISSR (inter-simple sequence repeat) markers were analyzed. Morphometric data revealed high phenotypic similarity between coastal populations. The genetic analysis revealed a high similarity between coastal populations (genetic identity, 93%), which were differentiated from the Andean population (genetic identity, 84%). This study contributes new genotypic and phenotypic data for the C. tuberosus populations in forest ecosystems of A. araucana, and clarifies the associations between these characteristics and the geographic distributions of populations.     

Do differences in plant and flower age change mating patterns and alter offspring fitness in Raphanus sativus (Brassicaceae)?

When more pollen is present on stigmas than needed to fertilize all ovules, selection among pollen grains may occur due to effects of both pollen donors and maternal plants. We asked whether increasing plant age and flower age, two changes in maternal condition, altered the pattern of seed paternity after mixed pollination. We also asked whether changes in seed paternity affected offspring success in an experimental garden. While flower age did not affect seed paternity, there was a dramatic shift in pollen donor performance as plants aged. These differences were seen in the offspring as well, where the offspring of one pollen donor, which sired more seeds on young plants, flowered earlier in the season, and the offspring of another pollen donor, which sired more seeds on old plants, flowered later in the season. Thus, change in maternal condition resulted in altered seed paternity, perhaps because the environment for pollen tube growth was different. The pattern of seed paternity and offspring performance suggests that pollen donors may show temporal specialization.     

Are amino groups advantageous to insensitive high explosives (IHEs)?

There is usually a contradiction between increasing energy densities and reducing sensitivities of explosives. The explosives with both high energy densities and low sensitivities, or the so-called insensitive high explosives (IHEs), are desirable in most cases. It seems from applied explosives that amino groups are advantageous to IHE but the amount of amino groups contained IHEs is very limited. To make this clear, we present systemic examinations of the effects on the two properties stressed in IHEs after introducing amino groups to different molecular skeletons. As a result, the amino groups on resonant sites to nitro groups in conjugated systems can improve distinctly sensitivities and change energy densities in terms of oxygen balance; while the amino groups in unconjugated systems can hardly increase energy densities and usually cause increased sensitivities. It agrees well with a fact that almost all the molecules of applied amino group contained explosives possess conjugated skeletons. We therefore confirm that if amino groups are introduced resonantly to a nitro group in a conjugated system and the introduction improves OB, they are advantageous to IHEs.     

Are age differences in sleep due to phase differences in the output of the circadian timing system?

Our aim was to evaluate whether age-related changes in the phase of the output of the circadian timing system (CTS) can explain age differences in habitual bedtime/wake time and in sleep consolidation parameters. Analyses focused on a group of healthy elderly people (older than 70 years) with no sleep problems and with similar subjective sleep quality as a young control group. The 2-week sleep diary data and 24h laboratory temperature recordings were examined for 70 subjects (22 young men [YM], 19 old men [OM], 29 old women [OW]). Polysomnographic (PSG) sleep data recorded during temperature data acquisition were also available for 62 subjects. These analyses made use of our recently developed technique to demask temperature rhythm data. As expected, compared to the young subjects, older subjects showed earlier habitual bedtime and wake time, more disturbed sleep, and a tendency for an earlier minimum of the circadian temperature rhythm. Despite sleep consolidation differences, the groups showed very similar habitual phase-angle differences (interval between the time occurrence of the fitted temperature minimum and habitual wake time). Both elderly and young subjects woke up on average 3h after the temperature minimum. After controlling for the effects of age group, habitual bedtime and wake time were related to clock time phase of the circadian temperature rhythm, with an earlier phase associated with earlier habitual bedtime and wake time. None of the sleep consolidation parameters were linked to the temperature phase angle. In conclusion, sleep consolidation changes associated with healthy aging do not appear to be related to changes in the phase-angle difference between the output signal from the CTS and sleep.     

Ecological differentiation,speciation, and rarity: How do they match in Tephroseris longifolia agg. (Asteraceae)?

Tephroseris longifolia agg. is a complex group of outcrossing perennials distributed throughout Central Europe. Recent morphological study revealed six morphotypes corresponding to five previously distinguished subspecies, together with Alpine and Pannonian morphotypes of T. longifolia subsp. longifolia. The delimited morphotypes differ in relative DNA content, geographical range, and rarity. We compared ecological niches of the six morphotypes in order to assess the impact of ecological differentiation on the speciation processes within the T. longifolia agg. Further, we examined whether morphotypes with small range are more ecologically specialized than their widespread relatives. The distribution area of the aggregate includes the Alps, Apennines, Carpathians, and the Pannonian Basin. Ecological variables linked to climate, topography, soil, and vegetation were gathered from 135 circular plots recorded in 35 localities. Related variables were grouped to describe the partial ecological niches: climatic, topographic, pedological, biotic, and coenotic (based either on vascular plants or on bryophytes), each of them visualized as an envelope in the two‐dimensional nonmetric multidimensional scaling ordination space. Each partial ecological niche for a given morphotype was characterized by its position (location of the envelope centroid), breadth (surface of the envelope), and overlaps with envelopes of the other morphotypes. Mantel statistics based on Spearman correlation coefficients were used to quantify differentiation of morphotypes in ecological parameters represented by the partial ecological niches. The significant niche differentiation was confirmed for climatic, topographic, pedological, and vascular plant‐based coenotic niches. Ecological niche differentiation corresponded well to morphological and partially also to karyological differentiation. Narrowly distributed morphotypes occupied more specific habitats and had narrower ecological niches than their widespread relatives. Ecological differentiation could be considered an important driver in allopatric speciation within the T. longifolia agg. Our results demonstrate that quantification of ecological divergence is helpful in assessing evolutionary history of closely related taxa.     

Is fertility reduced among men exposed to radiofrequency fields in the Norwegian Navy?

The effects of radiofrequency fields on human health are not well understood, and public concern about negative health effects has been rising. The aim of this study was to examine the relationship between workers exposed to electromagnetic fields and their reproductive health. We obtained data using a questionnaire in a cross-sectional study of naval military men, response rate 63% (n = 1487). We asked the respondents about exposure, lifestyle, reproductive health, previous diseases, work and education. An expert group categorized the work categories related to electromagnetic field exposure. We categorized the work categories "tele/communication," "electronics" and "radar/sonar" as being exposed to electromagnetic fields. Logistic regression adjusted for age, ever smoked, military education, and physical exercise at work showed increased risk of infertility among tele/communication odds ratio (OR = 1.72, 95% confidence interval 1.04-2.85), and radar/sonar odds ratio (OR = 2.28, 95% confidence interval 1.27-4.09). The electronics group had no increased risk. This study shows a possible relationship between exposure to radiofrequency fields during work with radiofrequency equipment and radar and reduced fertility. However, the results must be interpreted with caution.     

Are age and sex differences in brain oxytocin receptors related to maternal and infanticidal behavior in naïve mice?

This article is part of a Special Issue “Parental Care”.There is significant variability in the behavioral responses displayed by naïve young and adult mice when first exposed to pups. This variability has been associated with differences in the expression of oxytocin receptors (OXTRs) in the brain in several species. Experiment I investigated the behavioral responses of juvenile, adolescent, and adult CB57BL/6 males and females when first exposed to pups. We found an age increase in maternal females (11% of juveniles, 20% of adolescents, and 50% of young adults), and infanticidal males (0% of juveniles, 30% of adolescents, 44.5% of young adults, and 100% of older adults). Experiment II investigated OXTR density in the brain of juvenile and adult mice. Our results revealed an age decline in the density of OXTR in several brain regions, including the lateral septum, cingulated and posterior paraventricular thalamic nucleus in both males and females. Adult females had higher OXTR density in the ventromedial nucleus/postero-ventral hypothalamus (VMH) and the accessory olfactory bulb (AOB), but lower density in the ventral region of the lateral septum (LSv) than juveniles. Males had lower OXTR density in the anterior olfactory area (AOA) compared to juveniles. No age or sex differences were found in the medial preoptic area, and amygdaloid nuclei, among other brain regions. This study suggests that 1) maturation of parental and infanticidal behavioral responses is not reached until adulthood; 2) the pattern of development of OXTR in the mouse brain is unique, region specific, and differs from that observed in other rodents; 3) either up or down regulation of OXTR in a few brain regions (VMH/AOB/LSv/AOA) might contribute to age or sex differences in parental or infanticidal behavior.     

Are nest-detection probability methods relevant for estimating turtle dove breeding populations? a case study in Moroccan agroecosystems

Knowing the population size of game is a basic prerequisite to determining adequate hunting management and conservation strategies and setting up appropriate hunting quotas. This study compared three methods complete count, capture–recapture and N-mixture modelling to estimate a turtle dove Streptopelia turtur breeding population using nest counts. We randomly sampled 143 fruit farms (60 orange orchards and 83 olive orchards) situated in an irrigated area in Morocco at the peak of breeding activity. We calculated the probability of detecting active turtle dove nests using information from two observers who independently searched the same sample plots. We found that (a) the capture–recapture method provided more precise results of nest abundance than N-mixture modelling, and that (b) the probability of nest detection was noticeably different between the two study orchards—higher in the orange orchards than in the olive orchards. Although these two methods are easy to implement and cost-effective for estimating population abundance on a large spatial scale, our results demonstrate that the resulting estimates are prone to bias depending on the tree height of the plantations. Of the three methods for estimating turtle dove abundance, complete counts were preferable for assessing population size. Using the complete counts, the density of turtle dove nests was found to be 2.96 nests/ha in the orange orchards and 0.93 nests/ha in the olive orchards. A density extrapolation to the entire surface area of the Tadla Region indicated a minimum breeding population size of 58,969 pairs (95 % confidence interval: 48,550–69,353).     

Are there differences in body dimensions among children from matings at different exogamic levels?

The aim of this study was to investigate if there are differences in body dimensions among children from matings of different levels of exogamy. The cross-sectional sample consisted of 285 children, 136 males and 149 females, 6 to 10 years old, attending elementary schools in Tortoli, a town in east-central Sardinia. The children were divided into four groups according to the level of exogamy. One of them included the children of parents born in the same Sardinian village is highly endogamous. For each sex, the Kruskal-Wallis test revealed no significant differences among the four groups of children for the 35 anthropometric variables considered, with the exception of head circumference in the male sample. In particular, there were no significant differences among the four groups of children for some anthropometric variables that are considered to be indirect indicators of nutritional status: sum of skinfolds, waist/hip ratio, body mass index, total upper arm area, upper arm muscle area, upper arm fat area. We conclude that Sardinian children from marriages of different levels of exogamy do not differ in body dimensions if they have similar nutritional conditions.     

Mycorrhizal responses to biochar in soil – concepts and mechanisms

Experiments suggest that biomass-derived black carbon (biochar) affects microbial populations and soil biogeochemistry. Both biochar and mycorrhizal associations, ubiquitous symbioses in terrestrial ecosystems, are potentially important in various ecosystem services provided by soils, contributing to sustainable plant production, ecosystem restoration, and soil carbon sequestration and hence mitigation of global climate change. As both biochar and mycorrhizal associations are subject to management, understanding and exploiting interactions between them could be advantageous. Here we focus on biochar effects on mycorrhizal associations. After reviewing the experimental evidence for such effects, we critically examine hypotheses pertaining to four mechanisms by which biochar could influence mycorrhizal abundance and/or functioning. These mechanisms are (in decreasing order of currently available evidence supporting them): (a) alteration of soil physico-chemical properties; (b) indirect effects on mycorrhizae through effects on other soil microbes; (c) plant–fungus signaling interference and detoxification of allelochemicals on biochar; and (d) provision of refugia from fungal grazers. We provide a roadmap for research aimed at testing these mechanistic hypotheses.     

Intimin and the host cell--is it bound to end in Tir(s)?

Intimate bacterial adhesion to the intestinal epithelium is a pathogenic mechanism shared by several human and animal enteric pathogens, including enteropathogenic and enterohaemorrhagic Escherichia coli. Two bacterial protein partners involved in this intimate association have been identified, intimin and Tir. Some key remaining questions include whether intimin specifically interacts with one or more host-cell-encoded molecules and whether these contacts are a prerequisite for the subsequent intimate intimin-Tir association. Recent data support the hypothesis that the formation of a stable intimin-Tir relationship is the consequence of intimin protein interactions involving both host and bacterial components.     

Are there differences in immune function between continental and insular birds?

Generally, immune system architecture varies with different environments, which presumably reflect different pathogen pressures. Specifically, populations from relatively disease-free, oceanic islands are expected to exhibit reorganized immune systems, which might be characterized by attenuated responses, given the costs of immune function. Some insular animals exhibit an 'island syndrome,' including increased susceptibility to disease, and some insular populations have declined when they failed to resist infection by introduced pathogens. I measured eight indices of immune function (haemolysis, haemagglutination, concentration of haptoglobin and concentration of five leukocyte types) in 15 phylogenetically matched pairs of bird populations from North America and from the islands of Hawaii, Bermuda and the Galápagos. Immune responses were not attenuated in insular birds, and several indices, including the concentration of plasma haptoglobin, were elevated. Thus, I find no support for the specific hypothesis that depauperate parasite communities and the costs of immune defences select for reduced immune function. Instead, I suggest that life on islands leads to an apparent reorganization of immune function, which is defined by increases in defences that are innate and inducible. These increases might signal that systems of acquired humoral immunity and immunological memory are less important or dysfunctional in island populations.