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28 septembre 2017

Do linden trees kill bees ? Reviewing the causes of bee deaths on silver linden (Tilia tomentosa) [Biology Letters]

Keywords : bumblebee, ecotoxicology, pollinator decline, urban ecology

For decades, linden trees (basswoods or lime trees), and particularly silver linden (Tilia tomentosa), have been linked to mass bee deaths. This phenomenon is often attributed to the purported occurrence of the carbohydrate mannose, which is toxic to bees, in Tilia nectar. In this review, however, we conclude that from existing literature there is no experimental evidence for toxicity to bees in linden nectar. Bee deaths on Tilia probably result from starvation, owing to insufficient nectar resources late in the tree’s flowering period. We recommend ensuring sufficient alternative food sources in cities during late summer to reduce bee deaths on silver linden. Silver linden metabolites such as floral volatiles, pollen chemistry and nectar secondary compounds remain underexplored, particularly their toxic or behavioural effects on bees. Some evidence for the presence of caffeine in linden nectar may mean that linden trees can chemically deceive foraging bees to make sub-optimal foraging decisions, in some cases leading to their starvation.

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28 septembre 2017

Priority effects can persist across floral generations in nectar microbial metacommunities [Oikos]

The order of species arrival can influence how species interact with one another and, consequently, which species may coexist in local communities. This phenomenon, called priority effects, has been observed in various types of communities, but it remains unclear whether priority effects persist over the long term spanning multiple generations of local communities in metacommunities. Focusing on bacteria and yeasts that colonize floral nectar of the sticky monkey flower, Mimulus aurantiacus, via hummingbirds and other flower-visiting animals, we experimentally manipulated initial microbial dominance on plants (regarded as metacommunities) to examine whether its effects persisted across multiple generations of flowers (regarded as local microbial habitats).(...)

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28 septembre 2017

The effect of rivers, streams, and canals on property values [River Research & Applications]

Keywords : aesthetic, canal, hedonic, property value, recreation, river, stream, view

Rivers, streams, and canals support a variety of critical agricultural, industrial, transportation, ecological, and household uses. They also provide important aesthetic, recreational, and sociocultural benefits. This review paper synthesizes the evidence to date regarding the value of these linear water features as aesthetic and recreational resources to adjacent and nearby residents. Specifically, it summarizes 25 studies that have used the hedonic pricing method to calculate the effects of views of and proximity to rivers, streams, and canals on surrounding residential property values. The majority of studies indicated that significant positive property price effects are associated with river, stream, and canal view and proximity, though these effects appear less definitive in rural than urban settings. Implications of the body of evidence for planning, management, and development are discussed, and potential effects of climate change and diversion policies are highlighted. Improvements in measurement facilitated by advanced geographic information systems and rigorous spatially explicit regression techniques are noted.

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28 septembre 2017

Ananke : temporal clustering reveals ecological dynamics of microbial communities [PeerJ]

Keywords : bioinformatics, ecology, microbiology, computational science

Taxonomic markers such as the 16S ribosomal RNA gene are widely used in microbial community analysis. A common first step in marker-gene analysis is grouping genes into clusters to reduce data sets to a more manageable size and potentially mitigate the effects of sequencing error. Instead of clustering based on sequence identity, marker-gene data sets collected over time can be clustered based on temporal correlation to reveal ecologically meaningful associations. We present Ananke, a free and open-source algorithm and software package that complements existing sequence-identity-based clustering approaches by clustering marker-gene data based on time-series profiles and provides interactive visualization of clusters, including highlighting of internal OTU inconsistencies. Ananke is able to cluster distinct temporal patterns from simulations of multiple ecological patterns, such as periodic seasonal dynamics and organism appearances/disappearances.(...)

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28 septembre 2017

Historical dynamics and current environmental effects explain the spatial distribution of species richness patterns of New World monkeys [PeerJ]

Keywords : biodiversity, biogeography

Why biodiversity is not uniformly distributed on the Earth is a major research question of biogeography. One of the most striking patterns of disparity in species distribution are the biodiversity hotspots, which generally do not fit with the distribution of relevant components of the Neotropical biota. In this study, we assess the proximal causes of the species-richness pattern of one of the most conspicuous groups of Neotropical mammals, the New World monkeys the Platyrrhini. We test two complementary hypotheses : (1) there is a historical source-sink dynamic (addressed using macroevolutionary and macroecological approaches) ; (2) the large number of species in the Amazon basin is due to the constraints imposed by environmental variables occurring outside this area.(...)

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