Members of the family Circoviridae, specifically the genus Circovirus, were thought to infect only vertebrates; however, members of a sister group under the same family, the proposed genus Cyclovirus, have been detected recently in insects. In an effort to explore the diversity of cycloviruses and better understand the evolution of these novel ssDNA viruses, here we present five cycloviruses isolated from three dragonfly species (Orthetrum sabina, Xanthocnemis zealandica and Rhionaeschna multicolor) collected in Australia, New Zealand and the USA, respectively. The genomes of these five viruses share similar genome structure to other cycloviruses, with a circular 1.7 kb genome and two major bidirectionally transcribed ORFs. The genomic sequence data gathered during this study were combined with all cyclovirus genomes available in public databases to identify conserved motifs and regulatory elements in the intergenic regions, as well as determine diversity and recombinant regions within their genomes. The genomes reported here represent four different cyclovirus species, three of which are novel. Our results confirm that cycloviruses circulate widely in winged-insect populations; in eight different cyclovirus species identified in dragonflies to date, some of these exhibit a broad geographical distribution. Recombination analysis revealed both intra-and inter-species recombination events amongst cycloviruses, including genomes recovered from disparate sources (e.g. goat meat and human faeces). Similar to other well-characterized circular ssDNA viruses, recombination may play an important role in cyclovirus evolution. The GenBank/EMBL/DDBJ accession numbers for the genome sequences of dragonfly cycloviruses identified in this study are KC512916-KC512920. One supplementary figure and two supplementary tables are available with the online version of this paper.

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Here, we show that the last century of fire suppression in the western U.S. has resulted in fire intensities that are unique over more than 900 years of record in ponderosa pine forests (Pinus ponderosa). Specifically, we use the heat-sensitive luminescence signal of archaeological ceramics and tree-ring fire histories to show that a recent fire during mild weather conditions was more intense than anything experienced in centuries of frequent wildfires. We support this with a particularly robust set of optically stimulated luminescence measurements on pottery from an archaeological site in northern New Mexico. The heating effects of an October 2012 CE prescribed fire reset the luminescence signal in all 12 surface samples of archaeological ceramics, whereas none of the 10 samples exposed to at least 14 previous fires (1696–1893 CE) revealed any evidence of past thermal impact. This was true regardless of the fire behavior contexts of the 2012 CE samples (crown, surface, and smoldering fires). It suggests that the fuel characteristics from fire suppression at this site have no analog during the 550 years since the depopulation of this site or the 350 years of preceding occupation of the forested landscape of this region.

In archaeology, thermoluminescence is used to estimate the number of years since an artifact or feature made of geological sediment was last exposed to heat. Many types of archaeological samples are datable by thermoluminescence. By dividing the amount of ionizing radiation accumulated over time in a sample, called the equivalent dose, by the total environmental dose rate from alpha, beta, gamma, and cosmic particles, a luminescence specialist calculates its thermoluminescence age.