Contemporary breeding biology of critically endangered Regent Honeyeaters: implications for conservation

Identifying factors influencing the demographics of threatened species is essential for conservation, but a lack of comprehensive demographic data often impedes the effective conservation of rare and mobile species. We monitored breeding of critically endangered and semi‐nomadic Regent Honeyeaters Anthochaera phrygia (global population c. 100 pairs) over 3 years throughout their range. Overall nest success probability (0.317) was highly spatially variable and considerably lower than previous estimates for this (and many other honeyeater) species, as was productivity of successful nests (mean 1.58 juveniles fledged). Nest surveillance revealed high predation rates by a range of birds and arboreal mammals as the primary cause of nest failure. An estimated 12% of pairs either failed to establish a territory or their nests did not reach the egg stage. We also found a male bias to the adult sex ratio, with an estimated 1.18 males per female. Juvenile survival for the first 2 weeks after fledging was high (86%). Management interventions that aim to increase nest success in areas of low nest survival must be investigated to address an apparent decline in reproductive output and avoid extinction of the Regent Honeyeater. We show that temporal and spatial variation in the breeding success of rare and highly mobile species can be quantified with robust population monitoring using sampling regimens that account for their life histories. Understanding the causes of spatio‐temporal variation in breeding success can enhance conservation outcomes for such species through spatially and temporally targeted recovery actions.     

The RNase E/G-type endoribonuclease of higher plants is located in the chloroplast and cleaves RNA similarly to the E. coli enzyme

RNase E is an endoribonuclease that has been studied primarily in Escherichia coli, where it is prominently involved in the processing and degradation of RNA. Homologs of bacterial RNase E are encoded in the nuclear genome of higher plants. RNA degradation in the chloroplast, an organelle that originated from a prokaryote similar to cyanobacteria, occurs via the polyadenylation-assisted degradation pathway. In E. coli, this process is probably initiated with the removal of 5'-end phosphates followed by endonucleolytic cleavage by RNase E. The plant homolog has been proposed to function in a similar way in the chloroplast. Here we show that RNase E of Arabidopsis is located in the soluble fraction of the chloroplast as a high molecular weight complex. In order to characterize its endonucleolytic activity, Arabidopsis RNase E was expressed in bacteria and analyzed. Similar to its E. coli counterpart, the endonucleolytic activity of the Arabidopsis enzyme depends on the number of phosphates at the 5' end, is inhibited by structured RNA, and preferentially cleaves A/U-rich sequences. The enzyme forms an oligomeric complex of approximately 680 kDa. The chloroplast localization and the similarity in the two enzymes' characteristics suggest that plant RNase E participates in the initial endonucleolytic cleavage of the polyadenylation-stimulated RNA degradation process in the chloroplast, perhaps in collaboration with the two other chloroplast endonucleases, RNase J and CSP41.     

A new approach to dual-color two-photon microscopy with fluorescent proteins

Background  

Two-photon dual-color imaging of tissues and cells labeled with fluorescent proteins (FPs) is challenging because most two-photon microscopes only provide one laser excitation wavelength at a time. At present, methods for two-photon dual-color imaging are limited due to the requirement of large differences in Stokes shifts between the FPs used and their low two-photon absorption (2PA) efficiency.     

Atmospheric chemosynthesis is phylogenetically and geographically widespread and contributes significantly to carbon fixation throughout cold deserts

Cold desert soil microbiomes thrive despite severe moisture and nutrient limitations. In Eastern Antarctic soils, bacterial primary production is supported by trace gas oxidation and the light-independent RuBisCO form IE. This study aims to determine if atmospheric chemosynthesis is widespread within Antarctic, Arctic and Tibetan cold deserts, to identify the breadth of trace gas chemosynthetic taxa and to further characterize the genetic determinants of this process. H₂ oxidation was ubiquitous, far exceeding rates reported to fulfill the maintenance needs of similarly structured edaphic microbiomes. Atmospheric chemosynthesis occurred globally, contributing significantly (p < 0.05) to carbon fixation in Antarctica and the high Arctic. Taxonomic and functional analyses were performed upon 18 cold desert metagenomes, 230 dereplicated medium-to-high-quality derived metagenome-assembled genomes (MAGs) and an additional 24,080 publicly available genomes. Hydrogenotrophic and carboxydotrophic growth markers were widespread. RuBisCO IE was discovered to co-occur alongside trace gas oxidation enzymes in representative Chloroflexota, Firmicutes, Deinococcota and Verrucomicrobiota genomes. We identify a novel group of high-affinity [NiFe]-hydrogenases, group 1m, through phylogenetics, gene structure analysis and homology modeling, and reveal substantial genetic diversity within RuBisCO form IE (rbcL1E), and high-affinity 1h and 1l [NiFe]-hydrogenase groups. We conclude that atmospheric chemosynthesis is a globally-distributed phenomenon, extending throughout cold deserts, with significant implications for the global carbon cycle and bacterial survival within environmental reservoirs.Subject terms: Soil microbiology, Microbial ecology, Microbial genetics, Metagenomics, Microbiome     

Natural dispersal to sub-Antarctic Marion Island of two arthropod species

Distinguishing between species that are recent natural colonists, recent anthropogenic introductions, or previously unknown, but long-term resident native species, is a challenge for those who manage the conservation of the Antarctic region. Here, we report the discovery of two new arthropod species on sub-Antarctic Marion Island—Nabis capsiformis Germar (Heteroptera: Nabidae) and Tetragnatha sp. (Araneomorphae: Tetragnathidae). On the basis of their habitat use, dispersal abilities, historic biodiversity survey records, and limited information on genetic diversity, we conclude that the colonization events were natural.     

Rapid commencement of ecosystem recovery following aerial baiting on sub‐Antarctic Macquarie Island

Introduced rabbits have severely impacted the terrestrial ecosystem of sub‐Antarctic Macquarie Island. Here we describe first observations of rapid recovery of an important plant species following the commencement of a vertebrate pest eradication plan. The tussock grass Poa foliosa, a major component of the Macquarie Island landscape, has been severely impacted by rabbit grazing with large‐scale reductions in cover across the island observed at times over the last 50 years. Preliminary aerial baiting for rabbits and rodents commenced in winter 2010, and within 6 months, we observed substantial regrowth of tussock grass. The rapid re‐emergence of this grass over such a short time period following localised removal of rabbits has positive implications for the island’s recovery and provides insight for restoration monitoring.     

Using long-term population trends of an invasive herbivore to quantify the impact of management actions in the sub-Antarctic

Accurate, long-term population estimates of invasive vertebrate pests are a key element of ecosystem management. Not only can they clarify the role of invasive species in changing ecosystem dynamics, they are also necessary to evaluate and assess management actions. Rabbits were first introduced to sub-Antarctic Macquarie Island in the 1870s, and since the 1960s have been targeted and influenced by a range of management programs. Here, for the first time, we model population trends of rabbits on Macquarie Island from the beginning of these management actions to the end of a recent, successful eradication attempt. We show that over a 38-year time frame, the population has undergone substantial fluctuations, peaking at over 350,000 individuals (27 indiv ha^?1) in the late 1970s, before declining to less than 30,000 individuals (2–3 indiv ha^?1) through the 1980s and early 1990s. From the late 1990s to 2005, the population increased relatively rapidly, this time peaking at approximately 221,000 individuals. After the commencement of eradication operations in 2010, the population dropped sharply, decreasing from 135,707 ± 25,995 to effectively zero in just over 12 months. This research contributes to our understanding of the complex population dynamics of sub-Antarctic invasive species and highlights the importance of monitoring in planning, understanding and assessing management actions. The development of models described here allowed population trends to be identified on Macquarie Island, despite ‘noise’ in the data from seasonality or sporadic observations. In consequence, the impacts of both long- and short-term management actions could be quantified. These techniques are applicable to other locations and species where long-term census data exist.