The austral biflagellate Chloromonas rubroleosa (Chlorophyceae) is the closest relative of the unusual quadriflagellate genus Chlainomonas, both found in snow.

The quadriflagellate genus Chlainomonas frequently dominates red snow globally. It is unusual in several respects, with two separated pairs of flagella, apparent cell division via extrusion of cytoplasmic threads, and being nested phylogenetically within the biflagellate genus Chloromonas. Here, we showed that the austral species Chloromonas (Cr.) rubroleosa, originally described from Antarctic red snow, is a close biflagellate relative of Chlainomonas, challenging the monophyly of Chlainomonas as currently conceived. Sequences of the 18S rRNA gene robustly linked Cr. rubroleosa with near-identical environmental sequences from Antarctic red snow and Chlainomonas from North America, Japan, and Europe. Furthermore, the 18S rRNA and rbcL gene sequences of Cr. rubroleosa were almost identical to New Zealand and North American collections of Chlainomonas. Cr. rubroleosa and New Zealand Chlainomonas are separated by only a single-base substitution across the ITS1-5.8S-ITS2 rRNA loci (and according to ITS2, the North American collection is the next closest relative). This again raises the possibility that Chlainomonas is a life-cycle stage of vegetatively biflagellate organisms, although this remains confounded by the scarcity of biflagellates in field populations, the apparent cell division by quadriflagellates, and the absence of Chlainomonas-type cells in cultures of Cr. rubroleosa. The latter species is broadly similar to Chlainomonas, being poor at swimming, with similar pigment, chloroplast arrangement and ultrastructure, and is relatively large. Increased size is a feature of the wider clade of "Group D" snow algae. A synthesis of field and laboratory investigations may be needed to unravel the life cycle and correct the systematics of this group.

Nectar resources affect bird-dispersed microbial metacommunities in suburban and rural gardens.

As cities expand, understanding how urbanization affects biodiversity is a key ecological goal. Yet, little is known about how host-associated microbial diversity responds to urbanization. We asked whether communities of microbial (bacterial and fungal) in floral nectar and sugar-water feeders and vectored by nectar-feeding birds-thus forming a metacommunity-differed in composition and diversity between suburban and rural gardens. Compared to rural birds, we found that suburban birds vectored different and more diverse bacterial communities. These differences were not detected in the nectar of common plant species, suggesting that nectar filters microbial taxa and results in metacommunity convergence. However, when considering all the nectar sources present, suburban beta diversity was elevated compared to rural beta diversity due to turnover of bacterial taxa across a plant species and sugar-water feeders. While fungal metacommunity composition and beta diversity in nectar were similar between suburban and rural sites, alpha diversity was elevated in suburban sites, which mirrored the trend of increased fungal alpha diversity on birds. These results emphasize the interdependence of host, vector, and microbial diversity and demonstrate that human decisions can shape nectar microbial diversity in contrasting ways for bacteria and fungi.

Soil microbial sensitivity to temperature remains unchanged despite community compositional shifts along geothermal gradients.

Climate warming may be exacerbated if rising temperatures stimulate losses of soil carbon to the atmosphere. The direction and magnitude of this carbon-climate feedback are uncertain, largely due to lack of knowledge of the thermal adaptation of the physiology and composition of soil microbial communities. Here, we applied the macromolecular rate theory (MMRT) to describe the temperature response of the microbial decomposition of soil organic matter (SOM) in a natural long-term warming experiment in a geothermally active area in New Zealand. Our objective was to test whether microbial communities adapt to long-term warming with a shift in their composition and their temperature response that are consistent with evolutionary theory of trade-offs between enzyme structure and function. We characterized the microbial community composition (using metabarcoding) and the temperature response of microbial decomposition of SOM (using MMRT) of soils sampled along transects of increasing distance from a geothermally active zone comprising two biomes (a shrubland and a grassland) and sampled at two depths (0-50 and 50-100 mm), such that ambient soil temperature and soil carbon concentration varied widely and independently. We found that the different environments were hosting microbial communities with distinct compositions, with thermophile and thermotolerant genera increasing in relative abundance with increasing ambient temperature. However, the ambient temperature had no detectable influence on the MMRT parameters or the relative temperature sensitivity of decomposition (Q10 ). MMRT parameters were, however, strongly correlated with soil carbon concentration and carbon:nitrogen ratio. Our findings suggest that, while long-term warming selects for warm-adapted taxa, substrate quality and quantity exert a stronger influence than temperature in selecting for distinct thermal traits. The results have major implications for our understanding of the role of soil microbial processes in the long-term effects of climate warming on soil carbon dynamics and will help increase confidence in carbon-climate feedback projections.

Fast-tracking bespoke DNA reference database generation from museum collections for biomonitoring and conservation.

Despite recent advances in high-throughput DNA sequencing technologies, a lack of locally relevant DNA reference databases limits the potential for DNA-based monitoring of biodiversity for conservation and biosecurity applications. Museums and national collections represent a compelling source of authoritatively identified genetic material for DNA database development, yet obtaining DNA barcodes from long-stored specimens may be difficult due to sample degradation. Here we demonstrate a sensitive and efficient laboratory and bioinformatic process for generating DNA barcodes from hundreds of invertebrate specimens simultaneously via the Illumina MiSeq system. Using this process, we recovered full-length (334) or partial (105) COI barcodes from 439 of 450 (98%) national collection-held invertebrate specimens. This included full-length barcodes from 146 specimens which produced low-yield DNA and no visible PCR bands, and which produced as little as a single sequence per specimen, demonstrating high sensitivity of the process. In many cases, the identity of the most abundant sequences per specimen were not the correct barcodes, necessitating the development of a taxonomy-informed process for identifying correct sequences among the sequencing output. The recovery of only partial barcodes for some taxa indicates a need to refine certain PCR primers. Nonetheless, our approach represents a highly sensitive, accurate and efficient method for targeted reference database generation, providing a foundation for DNA-based assessments and monitoring of biodiversity.

Soil Nitrogen Treatment Alters Microbiome Networks Across Farm Niches.

Agriculture is fundamental for food production, and microbiomes support agriculture through multiple essential ecosystem services. Despite the importance of individual (i.e., niche specific) agricultural microbiomes, microbiome interactions across niches are not well-understood. To observe the linkages between nearby agricultural microbiomes, multiple approaches (16S, 18S, and ITS) were used to inspect a broad coverage of niche microbiomes. Here we examined agricultural microbiome responses to 3 different nitrogen treatments (0, 150, and 300 kg/ha/yr) in soil and tracked linked responses in other neighbouring farm niches (rumen, faecal, white clover leaf, white clover root, rye grass leaf, and rye grass root). Nitrogen treatment had little impact on microbiome structure or composition across niches, but drastically reduced the microbiome network connectivity in soil. Networks of 16S microbiomes were the most sensitive to nitrogen treatment across amplicons, where ITS microbiome networks were the least responsive. Nitrogen enrichment in soil altered soil and the neighbouring microbiome networks, supporting our hypotheses that nitrogen treatment in soil altered microbiomes in soil and in nearby niches. This suggested that agricultural microbiomes across farm niches are ecologically interactive. Therefore, knock-on effects on neighbouring niches should be considered when management is applied to a single agricultural niche.