Acute oral toxicity of zinc phosphide:an assessment for wild house mice(Mus musculus)

Irregular plagues of house mice,Mus musculus,incur major economic impacts on agricultural production in Australia.The efficacy of zinc phosphide(ZnP),the only registered broadacre control agent for mice,is reported as increasingly variable.Have mice become less sensitive over time or are they taking a sub-lethal dose and develop-ing aversion?In this laboratory study,the sensitivity of mice(wild caught;outbred laboratory strain)was assessed using oral gavage of a range of ZnP concentrations.The estimated LD50 values(72–79 mg ZnP/kg body weight)were similar for each mouse group but are significantly higher than previously reported.The willingness of mice to consume ZnP-coated grains was determined.ZnP-coated grains(50 g ZnP/kg grain)presented in the absence of alternative food were consumed and 94%of wild mice died.Mice provided with alternative food and ZnP-coated wheat grains(either 25 or 50 g ZnP/kg grain)consumed toxic and non-toxic grains,and mortality was lower(33–55%).If a sublethal amount of ZnP-coated grain was consumed,aversion occurred,mostly when alternative food was present.The sensitivity of wild house mice to ZnP in Australia is significantly lower than previously assumed.Under laboratory conditions,ZnP-coated grains coated with a new higher dose(50 g ZnP/kg grain)were readily consumed.Consumption of toxic grain occurred when alternative food was available but was decreased.Our unambiguousfindings for house mice indicate a re-assessment of the ZnP loading for baits used for control of many rodents around the world may be warranted.

The asymmetric relationships of the distribution of conspecific saplings and adults in forest fragments

Aims With the increase of land-use change,habitat fragmentation has become a major factor affecting plant diversity.Generally,when the adult density is high,the survival rate of conspecific saplings may decline and provide more resources and space for other species to maintain a high local species diversity.Therefore,the spatial relationship of conspecific saplings and adults(SRCSA)can regulate plant diversity.However,very few studies have assessed SRCSA within fragmented forests,and we still largely unknown the relationship between SRCSA and species diversity in fragmented landscapes.Methods We calculated the mean strength of SRCSA using the spatial distribution data of saplings and adults with a log-transformed hierarchical offset-power model on 27 islands in a land-bridge island system.The higher strength of SRCSA reflects a more negative relationship between the density of conspecific saplings and adults on an island(i.e.the looser pattern of SRCSA).We tested the relationships among island attributes(i.e.island area,the distance to the mainland—MD,and the distance to the nearest island—ND),SRCSA and species diversity.Important Findings The strength of SRCSA increased with ND.Meanwhile,the species diversity significantly increased with the strength of SRCSA,and island area and the strength of SRCSA independently explained 26%and 6%of variation of species diversity,respectively,and their interactions explained 8%.Shade-intolerant and low-abundant species showed looser patterns of SRCSA.Our study suggests that SRCSA may have the effect of excluding species with a relatively low abundance in isolated island forests,which illustrates the importance of biotic interactions in maintaining plant diversity in fragmented forests.Our results also emphasize that we should consider forest connectivity when testing the conspecific negative density dependence.

An integrative bioinformatics pipeline shows that honeybee-associated microbiomes are driven primarily by pollen composition

The microbiomes associated with bee nests influence colony health through various mechanisms,although it is not yet clear how honeybee congeners differ in microbiome assembly processes,in particular the degrees to which floral visitations and the environment contribute to different aspects of diversity.We used DNA metabarcoding to sequence bacterial 16S rRNA from honey and stored pollen from nests of 4 honeybee species(Apis cerana,A.dorsata,A.florea,and A.laboriosa)sampled throughout Yunnan,China,a global biodiversity hotspot.We developed a computational pipeline integrating multiple databases for quantifying key facets of diversity,including compositional,taxonomic,phylogenetic,and functional ones.Further,we assessed candidate drivers of observed microbiome dissimilarity,particularly differences in floral visitations,habitat disturbance,and other key environmental variables.Analyses revealed that microbiome alpha diversity was broadly equivalent across the study sites and between bee species,apart from functional diversity which was very low in nests of the reclusive A.laboriosa.Turnover in microbiome composition across Yunnan was driven predominantly by pollen composition.Human disturbance negatively impacted both compositional and phylogenetic alpha diversity of nest microbiomes,but did not correlate with microbial turnover.We herein make progress in understanding microbiome diversity associated with key pollinators in a biodiversity hotspot,and provide a model for the use of a comprehensive informatics framework in assessing pattern and drivers of diversity,which enables the inclusion of explanatory variables both subtly and fundamentally different and enables elucidation of emergent or unexpected drivers.

Adaptive evolution to the natural and anthropogenic environment in a global invasive crop pest,the cotton bollworm

The cotton bollworm,Helicoverpa armigera,is set to become the most economically devastating crop pest in the world,threatening food security and biosafety as its range expands across the globe.Key to understanding the eco-evolutionary dynamics of H.armigera,and thus its management,is an understanding of population connectivity and the adaptations that allow the pest to establish in unique environments.We assembled a chromosome-scale reference genome and re-sequenced 503 individuals spanning the species range to delineate global patterns of connectivity,uncovering a previously cryptic population structure.