We have investigated the impact of reduced emissions due to COVID-19 lockdown measures in spring 2020 on air quality in Canada’s four largest cities: Toronto, Montreal, Vancouver, and Calgary. Observed daily concentrations of NO 2 , PM 2.5 , and O 3 during a “pre-lockdown” period (15 February–14 March 2020) and a “lockdown” period (22 March–2 May 2020), when lockdown measures were in full force everywhere in Canada, were compa...

Grasslands across the United States play a key role in regional livelihood and national food security. Yet, it is still unclear how this important resource will respond to the prolonged warm droughts and more intense rainfall events predicted with climate change. The early 21st‐century drought in the southwestern United States resulted in hydroclimatic conditions that are similar to those expected with future climate change. W...

Summary Aphids are sap‐feeding insects that host a range of bacterial endosymbionts including the obligate, nutritional mutualist Buchnera plus several bacteria that are not required for host survival. Among the latter, ‘ Candidatus Regiella insecticola’ and ‘ Candidatus Hamiltonella defensa’ are found in pea aphids and other hosts and have been shown to protect aphids from natural enemies. We have sequenced almost the entire...

The facultative endosymbiont of aphids, Hamiltonella defensa , kills parasitoid wasp larvae, allowing aphid hosts to survive and reproduce. This protection may depend on toxins that are encoded by the genomes of H. defensa and of its bacteriophage (APSE). Strains of H. defensa vary in degree of protection conferred upon Acyrthosiphon pisum (pea aphid). Although H. defensa is known to undergo some horizontal transmission among...

In many animal groups, mutualistic bacterial symbionts play a central role in host ecology, by provisioning rare nutrients and thus enabling specialization on restricted diets. Among such symbionts, genomic studies are most advanced for Buchnera , the obligate symbiont of aphids, which feed on phloem sap. The contents of the highly reduced Buchnera genomes have verified its role in aphid nutrition. Comparisons of Buchnera gene...