Search

A checklist of the oribatid mite species from two boreal fens in Northern Ontario, Canada is presented. 174 peat soil samples, collected between 2015–2020, yielded a heterogeneous assemblage of 80 species, 57 genera and 33 families. Species richness and diversity were significantly higher in a Sphagnum-dominated fen (69 species) compared to a Carex-dominated fen (51 species), and although 40 species were found at both sites, overall composition was significantly different between the two sites. We also present an update to the seminal work of Behan-Pelletier and Bissett (1994) on Oribatida of Canadian peatlands with 45 new species records for peatlands. Records for the parthenogenetic families Brachychthoniidae Thor, 1934 and Suctobelbidae Jacot, 1938 were considerably expanded, but other families such as Punctoribatidae, Thor, 1937 remain poorly represented in Canadian peatlands. Taken together, species richness estimates range from 86–105 species based on our sampling and the number of undescribed species recorded suggests that the oribatid mite fauna still need further examination to encompass their actual biodiversity in peatlands. We report that the oribatid mite fauna of Canadian peatlands comprise 186 species that includes all published records as of February 2021 and species presented here. [ABSTRACT FROM AUTHOR]

Questions: Climate warming has been demonstrated to shift peatland plant community composition from Sphagnum mosses to vascular plants in Sphagnum‐dominated peatlands. However, fewer studies have determined how increasing temperature affects vegetation patterns in Carex‐dominated peatlands. As plants are important determinants of carbon storage potential in peatlands, we aim to determine how climate warming alters plant community composition in peatlands of two different vegetation types. Location: Boreal peatlands in north–central Ontario, Canada. Methods: In a Sphagnum‐ and a Carex‐dominated peatland over two growing seasons, we instigated passive warming using clear open‐topped chambers, providing a modest increase (1–2°C) in temperature. In replicated plots we examined shifts in plant community composition using the point intercept method, and total above‐ground biomass using Leaf Area Index (LAI) against non‐warmed control plots. Results: While there was no difference in species diversity between control and warmed plots in either fen site, warming significantly increased above‐ground biomass in the Carex‐dominated fen and decreased moss abundance in the Sphagnum‐dominated fen. Both fens also displayed significantly different plant community composition between warming and control plots, and increased heterogeneity under warming. Conclusion: Peatlands are important global carbon stores and the plant community contributes to their carbon storage; Sphagnum mosses, in particular, are linked to high peatland carbon storage potential. Previous studies in Sphagnum‐dominated peatlands have shown concomitant declines in Sphagnum biomass and increases in vascular plant biomass, and in the short term, we show only a decline in Sphagnum. At both sites the increase in plant community heterogeneity suggests that climate warming effects on plant community composition in boreal peatlands may be more unpredictable than the literature suggests. Furthermore, this study demonstrates that plant community shifts occur even under modest warming scenarios. [ABSTRACT FROM AUTHOR]

Bumble bees are declining globally, largely due to habitat loss driven by agricultural intensification. Within agriculturally dominated landscapes, semi‐natural habitats (e.g. meadows, wetland edges) are fragmented, increasing the value of uncropped agricultural field margins for providing a source of food, nesting, and hibernation resources to bumble bees.We compared bumble bee communities sampled in agricultural field margins and semi‐natural habitats across Southwestern Ontario, Canada in order to assess differences in habitat quality. We then examined the effect of floral resources and soil characteristics on the bumble bee communities present in each site, independent of the habitat type classification.Our data revealed that bumble bee abundance, diversity, and community composition did not differ between habitat types. However, when examined independently of habitat type, bumble bee abundance and diversity increased with floral abundance, floral diversity, the number of rodent holes, and sandy soil texture.These results suggest that agricultural field margins are not inherently degraded bumble bee habitat and have the potential to provide food and nesting resources comparable to semi‐natural habitats in a fragmented agricultural landscape. Ensuring field margins contain the necessary floral resources and soil characteristics for bumble bees has implications for conservation and mitigating habitat loss caused by the agricultural fields themselves. [ABSTRACT FROM AUTHOR]

Free-living soil nematodes span several trophic levels and play a key role in soil food webs. As such, the relative abundances and diversity of nematode feeding groups, along with nematode body size that is correlated with trophic transfer efficiency may provide useful information in understanding carbon and nitrogen cycling in soil systems. Yet, despite their role in soil carbon dynamics, there is a lack of knowledge regarding nematode trophic diversity in high carbon storage systems such as boreal peatlands. Here we assessed nematode communities using feeding groups (bacterivores, fungivores, herbivores, omnivores, and predators) based on mouthpart morphology, and their body sizes (length and mass) in two contrasting boreal peatlands in Northern Ontario, Canada that differ in vegetation (Sphagnum vs Carex), hydrology, nutrient availability, and microbial decomposition. We found that nematode trophic diversity was higher in the Sphagnum -dominated fen, and that the dominant nematode group corresponded to the dominant microbial group at each site. Predatory nematodes were significantly more abundant and larger in the Sphagnum -dominated fen, consistent with greater food web complexity, but the average body size of nematodes (all feeding groups included) was not significantly different between the fens. Taken together, these observed trends in nematode feeding groups and body sizes, along with higher microbial biomass in the Sphagnum -dominated fen supports the idea that the two sites may differ ecologically, and generally follow differences in microbial communities. Our study provides important baseline information for understanding peatland soil food web dynamics and their implications for carbon and nutrient dynamics. • Nematode feeding group and body size were explored at contrasting peatlands. • Predators were more abundant and larger in a Sphagnum -dominated fen. • Nematode functional diversity parallels overall soil food web trophic structure. • Nematode communities from contrasting peatlands imply different ecological function. [ABSTRACT FROM AUTHOR]

• Oribatid mite community composition is driven to an extent by interactions between temperature and moisture. • Communities in the Sphagnum- and Carex -dominated fens showed contrasting responses to warming. • Warming-induced soil moisture reduction facilitated the establishment of terrestrial species and impacted semi-aquatic species. Climate warming is expected to disproportionately affect high latitude and alpine systems such as boreal peatlands. Previous studies observing changes in both plant and microbial communities suggest boreal peatlands may shift from carbon sinks to sources under warming. But few studies have investigated oribatid mites (Acari: Oribatida) under climate change scenarios in peatland systems, despite oribatid mites being well represented in terms of diversity in boreal peatlands. We performed a large-scale experimental field manipulation of warming in two contrasting peatland sites in Northern Ontario, Canada, and sampled oribatid mites over four years following three years of passive warming and one full growing season of active warming. We found that warming had contrasting effects on the oribatid mite community at both peatland sites, and depended on the peatland type. Specifically, we observed an increase in species richness at the drier, Sphagnum -dominated site and a reduction in species richness at the wetter, Carex -dominated site. That said, we suggest that these outcomes arise from the same mechanism, namely warming-induced reductions in soil moisture that impacted semi-aquatic species and facilitated the establishment of new species, likely from surrounding forests. We also observed increases in small-bodied species suggesting direct metabolic effects from warming. As such, we show that peatland oribatid mite community composition is driven to an extent by interactions between temperature and moisture but dependant on peatland type. As oribatid mite communities are responsive to multiple environmental changes, and play important mid-trophic level roles in soil food webs, changes in oribatid mite community composition may have consequences for carbon flux in peatland systems. [ABSTRACT FROM AUTHOR]

Ecological communities show extremely complex patterns of variation in space, and quantifying the relative importance of spatial and environmental factors underpinning patterns of species distributions is one of the main goals of community ecology. Although we have accumulated good knowledge about the processes driving species distributions within metacommunities, we have few insights about whether (and how) environmental and spatial features can actually generate consistent species distributional patterns across multiple metacommunities. In this paper we applied the elements of metacommunity structure (EMS) framework to identify and classify metacommunities according to multiple but discrete patterns of species distributions. Given that each pattern has unique underlying structuring mechanisms, exploring and comparing such patterns across multiple metacommunities spanning large geographical areas provides a way to test the existence of general principles underlying species distributions within metacommunities. In this study, we applied the EMS framework into a data set containing about 9000 lakes distributed across 85 fish metacommunities across Ontario, Canada, and estimated the relative importance of local and spatial factors in explaining their distributional patterns. Nested and Clementsian gradients were the patterns that fitted most metacommunities; nested metacommunities were distributed throughout the province, while Clementsian gradient metacommunities were concentrated in the southeastern region. Sixty-five percent of nested metacommunities were located in low-energy watersheds (i.e., colder climate and shorter growing season), whereas metacommunities representing Clementsian gradients were present in high-energy watersheds (i.e., relatively warmer climate and longer growing season). Taken together, our results reveal that the environmental and spatial properties in which metacommunities are embedded are at least partially responsible for their species distributional patterns.