Spatial scaling of forest soil microbial communities across a temperature gradient.

Temperature is an important correlate of global patterns of biodiversity, yet the mechanisms driving these relationships are not well understood. Taxa-area relationships (TARs) have been intensively examined, but the effects of temperature on TARs, particularly for microbial communities, are largely undocumented. Here we present a continental-scale description of temperature-dependent nested TARs of microbial communities (bacteria and archaea) from soils of six forest sites spanning a temperature gradient from subalpine Colorado to tropical Panama. Our results revealed that spatial scaling rates (z-values) of microbial communities varied with both taxonomic resolutions and phylogenetic groups. Additionally, microbial TAR z-values increased with temperature (r = 0.739, P < 0.05), but were not correlated with other environmental variables tested (P > 0.05), indicating that microbial spatial scaling rate is temperature-dependent. Understanding how temperature affects the spatial scaling of microbial biodiversity is of fundamental importance for preservation of soil biodiversity and management of ecosystems

Effect of the ultrastructure of chitosan nanoparticles in colloidal stability, quorum quenching and antibacterial activities

We have fabricated two types of crosslinked chitosan-based nanoparticles (NPs), namely (1) ionically crosslinked with tripolyphosphate (TPP), designated as IC-NPs and (2) dually co-crosslinked (ionically and covalently with TPP and genipin, respectively) termed CC-NPs. The two types of NPs were physichochemically characterized by means of DLS-NIBS, synchrotron SAXS and M3-PALS (zeta potential). First, we found that covalent co-crosslinking of ionically pre-crosslinked nanoparticles yielded monodisperse CC-NPs in the size range of ∼200 nm, whereas the parental IC-NPs remained highly polydisperse. While both types of chitosan nanoparticles displayed a core-shell structure, as determined by synchrotron SAXS, only the structure of CC-NPs remained stable at long incubation times. This enhanced structural robustness of CC-NPs was likely responsible of their superior colloidal stability even in biological medium. Second, we explored the antimicrobial and quorum sensing inhibition activity of both types of nanoparticles. We found that CC-NPs had lower long-term toxicity than IC-NPs. In contrast, sub-lethal doses of IC-NPs consistently displayed higher levels of quorum quenching activity than CC-NPs. Thus, this work underscores the influence of the NP’s ultrastructure on their colloidal and biological properties. While the cellular and molecular mechanisms at play are yet to be fully elucidated, our results broaden the spectrum of use of chitosan-based nanobiomaterialsin the development of antibiotic-free approaches against Gram-negative pathogenic bacteria

The role of sex separation in neutral speciation

Neutral speciation mechanisms based on isolation by distance and sexual selection, termed topopatric, have recently been shown to describe the observed patterns of abundance distributions and species-area relationships. Previous works have considered this type of process only in the context of hermaphrodic populations. In this work we extend a hermaphroditic model of topopatric speciation to populations where individuals are explicitly separated into males and females. We show that for a particular carrying capacity speciation occurs under similar conditions, but the number of species generated decreases as compared to the hermaphroditic case. Evolution results in fewer species having more abundant populations.Comment: 18 pages + 8 figure

The species-area relationship in centipedes (Myriapoda: Chilopoda): a comparison between Mediterranean island groups

The present study article examines the shapes of centipede species–area relationships (SARs) in the Mediterranean islands, compares the results of the linear form of the power model between archipelagos, discusses biological significance of the power model parameters with other taxa on the Aegean archipelago, and tests for a significant small-island effect (SIE). We used 11 models to test the SARs and we compared the quality-of-fit of all candidate models. The power function ranked first and Z-values was in the range 0.106–0.334. We assessed the presence of SIEs by fitting both a continuous and discontinuous breakpoint regression model. The continuous breakpoint regression functions never performed much better than the closest discontinuous model as a predictor of centipede species richness. We suggest that the relatively low Z-values in our data partly reflect better dispersal abilities in centipedes than in other soil invertebrate taxa. Longer periods of isolation and more recent island formation may explain the somewhat lower constant c in the western Mediterranean islands compared to the Aegean islands. Higher breakpoint values in the western Mediterranean may also be a result of larger distance to the mainland and longer separation times. Despite the differences in the geological history and the idiosyncratic features of the main island groups considered, the overall results are quite similar and this could be assigned to the ability of centipedes to disperse across isolation barriers

Population diversity and relatedness in sugarbirds (Promeropidae : Promerops spp.)

Sugarbirds are a family of two socially-monogamous passerine species endemic to southern Africa. Cape and Gurney’s Sugarbird (Promerops cafer and P. gurneyi) differ in abundance, dispersion across their range and in the degree of sexual dimorphism in tail length, factors that affect breeding systems and potentially genetic diversity. According to recent data, P. gurneyi are in decline and revision of the species’ IUCN conservation status to a threatened category may be warranted. It is therefore necessary to understand genetic diversity and risk of inbreeding in this species. We used six polymorphic microsatellite markers and one mitochondrial gene (ND2) to compare genetic diversity in P. cafer from Cape Town and P. gurneyi from Golden Gate Highlands National Park, sites at the core of each species distribution. We describe novel universal avian primers which amplify the entire ND2 coding sequence across a broad range of bird orders. We observed high mitochondrial and microsatellite diversity in both sugarbird populations, with no detectable inbreeding and large effective population sizes.https://peerj.comam2018BiochemistryGeneticsMicrobiology and Plant Patholog

Pre-fledging energy requirements of the nocturnally fed semi-precocial chicks of the Spotted Thick-knee (Burhinus capensis)

Studies of pre-fledging growth and energetics in precocial ( self-feeding) shorebird species have shown that chicks expend large amounts of energy on thermoregulation and activity. We investigated the pre-fledging growth and energetics of Spotted Thick- knee ( Burhinus capensis) chicks, which are semi- precocial ( fed by their parents), near Cape Town, South Africa, to determine whether semi- precocial development would reduce the energy expenditure of chicks and enable them to grow faster. In addition, because Spotted Thick- knees are nocturnally feeding shorebirds, we hypothesised that their more limited foraging time ( compared with diurnal feeders) would negatively influence growth and energy expenditure of chicks during their spring - summer breeding season. The growth- rate coefficient, resting metabolic rate, peak daily metabolisable energy and total metabolisable energy of Spotted Thick- knee chicks were similar to the values predicted for birds of their size. Therefore, the potential negative impact of nocturnal feeding on growth of chicks may be being countered by reduced chick energy expenditure on thermoregulation and activity owing to parental feeding, and adults potentially extending their foraging time into the day as their chicks become larger. The relative energy requirements of growing Thick- knee chicks were greater than those of precocial shorebird chicks in the same climate of the Western Cape, but lower than those of shorebirds breeding in temperate or arctic zones. The semi- precocial mode of development of Spotted Thick- knees did not result in reduced energy expenditure or faster growth than anticipated for shorebirds in general, but their relative growth was greater than that of precocial species at the same latitude. Therefore, semi- precocial development benefits the growth of Spotted Thick- knees

The energetic implications of precocial development for three shorebird species breeding in a warm environment

We investigated the effect of body size, parental behaviour and timing of breeding on the chick growth and energetics of three precocial shorebird (Charadrii) species in a warm sub-tropical environment: the Kittlitz's Plover Charadrius pecuarius, Blacksmith Lapwing Vanellus armatus, and Crowned Lapwing V. coronatus. The three species exhibited slower growth, longer pre-fledging periods and lower energy expenditure during the pre-fledging period than Arctic and temperate zone relatives of similar size. It was found that relative growth rates of charadriid and scolopacid species increased by 1.77% per degree latitude. Blacksmith and Crowned Lapwings are of similar size (i.e. about 160 g), about four times the mass of Kittlitz's Plovers. Taking body mass into account, the resting metabolic rate and daily energy expenditure of the three study species were similar. The relative amounts of energy needed for chicks to grow from a hatchling to a fledgling were low for the three species studied. The relative amount of energy needed to complete growth in charadriid and scolopacid species increased by 2.54% per degree latitude. Because Crowned Lapwings exhibited faster growth than Blacksmith Lapwings but similar daily energy expenditure we suggest that Blacksmith Lapwings compensate for greater energy expenditure in colder weather by growing more slowly. We suggest that small growth rate coefficient, low resting metabolic rate and low daily energy expenditure are adaptations to lower food availability and milder ambient temperatures in sub-tropical breeding habitats compared to temperate or Arctic regions

Energetics of growth in semi-precocial shorebird chicks in a warm environment:The African black oystercatcher, Haematopus moquini

We studied prefledging growth, energy expenditure and time budgets of African Black Oystercatcher, Haematopus moquini, chicks on Robben Island, Western Cape, South Africa. The aim of the study was to investigate the effect of parental feeding on the growth and energetics of semi-precocial shorebird chicks. Chicks reached mean fledging mass, 463 g, in 40 days. The growth rate coefficient of African Black Oystercatcher chicks was 2% below the predicted value for a shorebird species of their body mass, but it was smaller than that of other precocial and semi-precocial shorebirds to date. Resting metabolic rate (RMR, measured through respirometry), daily metabolisable energy (DME), defined as daily energy expenditure (DEE, measured with doubly labelled water) plus energy deposited into tissue (E-tis), and total metabolisable energy (TME) of African Black Oystercatcher chicks were similar to those expected for a species of their body size. DEE was not influenced by weather (ambient temperature, operative temperature and wind speed), therefore, variations in DEE may be explained by body mass alone. The relative RMR of the African Black Oystercatcher was greater, their TME was approximately the same, their average daily metabolisable energy (ADME) was less, and they spent less time foraging (short periods of parental feeding) and more time inactive than three precocial species in the Western Cape. Therefore, the semi-precocial mode of development of African Black Oystercatcher chicks reduced energy costs from thermoregulation and activity, and they were able to grow relatively faster than precocial, self-feeding shorebird species in similar climatic conditions. The growth rate coefficient of African Black Oystercatcher chicks was smaller than that of Eurasian Oystercatcher, Haematopus ostralegus, chicks, which may be a consequence of differences in body size and latitudinal effects. (c) 2007 Elsevier GmbH. All rights reserved