Many species of Rickettsia are well-known mammalian pathogens transmitted by blood-feeding arthropods. However, molecular surveys are continually uncovering novel Rickettsia species, often in unexpected hosts, including many arthropods that do not feed on blood. This study reports a systematic molecular characterization of a Rickettsia infecting the psocid Liposcelis bostrychophila (Psocoptera: Liposcelidae), a common and cosmopolitan household pest. Surprisingly, the psocid Rickettsia is shown to be Rickettsia felis, a human pathogen transmitted by fleas that causes serious morbidity and occasional mortality. The plasmid from the psocid R. felis was sequenced and was found to be virtually identical to the one in R. felis from fleas. As Liposcelis insects are often intimately associated with humans and other vertebrates, it is speculated that they acquired R. felis from fleas. Whether the R. felis in psocids causes disease in vertebrates is not known and warrants further study.Many species of Rickettsia are well-known mammalian pathogens that are transmitted by blood-feeding arthropods via bites or feces and can cause mild to fatal diseases in humans (33). Some species are also considered potential bioterrorism agents (4). Most Rickettsia research has focused on pathogens that are found in two closely related species groups, the typhus and spotted fever groups, such as Rickettsia prowazekii, Rickettsia rickettsii, and Rickettsia typhi, the causal agents of epidemic typhus, Rocky Mountain spotted fever, and murine typhus, respectively (3, 4, 33). However, recent surveys suggest that Rickettsia bacteria are much more widespread than previously suspected and that they are being detected in novel hosts, the vast majority of which are arthropods, including many that do not feed on blood (29,45).The number of new rickettsial species that cause diseases in humans is rapidly increasing (33). One such species that has been generating much interest in recent years is Rickettsia felis, the causative agent of a murine typhus-like disease (1,2,13,16,17,28,44). The disease is often unrecognized, and even though it is considered clinically mild, it can cause severe illness and death in older patients and in cases of delayed diagnosis (2). R. felis was identified only in 1990 (1) and has since been found worldwide in fleas, where it is maintained transovarially and can reach high infection rates (e.g., 86% to 94% in cat fleas) (2, 3, 44), as well as in ticks and mites (34). While experimental infections have confirmed that R. felis is transmitted to vertebrate hosts via blood feeding and that R. felis occurs in an infectious extracellular state (39), it is not known whether transmission can also occur through contamination of broken skin by infected vector feces, as in R. typhi (3,34).A number of features distinguish R. felis from species in both the typhus and spotted fever groups. Lately, it has been proposed that R. felis be in its own group, allied with Rickettsia akari and Rickettsia australis, the causal agents of rickett...

The ranges of arctic–alpine species have shifted extensively with Pleistocene climate changes and glaciations. Using sequence data from the trnH-psbA and trnT-trnL chloroplast DNA spacer regions, we investigated the phylogeography of the widespread, ancient (>3 million years) arctic–alpine plant Oxyria digyna (Polygonaceae). We identified 45 haplotypes and six highly divergent major lineages; estimated ages of these lineages (time to most recent common ancestor, TMRCA) ranged from ∼0.5 to 2.5 million years. One lineage is widespread in the arctic, a second is restricted to the southern Rocky Mountains of the western United States, and a third was found only in the Himalayan and Altai regions of Asia. Three other lineages are widespread in western North America, where they overlap extensively. The high genetic diversity and the presence of divergent major cpDNA lineages within Oxyria digyna reflect its age and suggest that it was widespread during much of its history. The distributions of individual lineages indicate repeated spread of Oxyria digyna through North America over multiple glacial cycles. During the Last Glacial Maximum it persisted in multiple refugia in western North America, including Beringia, south of the continental ice, and within the northern limits of the Cordilleran ice sheet. Our data contribute to a growing body of evidence that arctic–alpine species have migrated from different source regions over multiple glacial cycles and that cryptic refugia contributed to persistence through the Last Glacial Maximum.

Aim Many plants, especially at high latitudes, have both widespread and highly discontinuous geographical distributions. To increase understanding of how such patterns originate, we examine genetic patterns in the arctic-alpine plant Sibbaldia procumbens. We evaluate the contributions of refugia and the role of long-distance dispersal in shaping the current range of this species.Location Northern Hemisphere, especially North America.Methods We sampled Sibbaldia from 176 localities, including 168 for S. procumbens. We analysed sequence variation in three plastid DNA non-coding regions (the atpI-atpH and trnL-trnF intergenic spacers and the trnL intron), performed Bayesian phylogenetic analyses and statistical parsimony analyses on the combined sequences, and analysed the geographical patterns of haplotype distribution and genetic diversity using data from all populations.Results Sibbaldia procumbens probably originated in the mountains of South and East Asia. We identified highly distinct clades in Europe and North America, which overlapped on oceanic islands of the North Atlantic indicating long-distance dispersal capability. The North American clade included two lineages, one in California and the other widely distributed across the continent and North Atlantic. Haplotype diversity in the latter lineage was markedly higher to the south, suggesting mid-late Pleistocene southward displacement of North American populations with subsequent migration northwards into previously glaciated regions. In Europe, disjunct geographical regions generally harboured distinct haplotypes.Main conclusions Multiple Pleistocene refugia for S. procumbens occurred in both North America and Europe. North American refugia existed in California and in the southern Rocky Mountains, but in contrast with most widespread arctic-alpine species we found no evidence for a Beringian refugium. Cryptic refugia may have existed within the Cordilleran Ice Sheet. Episodes of range expansion and contraction and long-distance dispersal have all contributed to the genetic structure and widespread but fragmented distribution of this species.

Aim We investigated genetic variation in Bistorta vivipara, a widespread Northern Hemisphere tundra species, to infer patterns of migration and where it may have survived during the Last Glacial Maximum (LGM). Location Samples came primarily from western North America, with a few from the Arctic and Eurasia. Methods We sequenced two chloroplast DNA spacer regions, trnH–psbA and trnS–G, in individuals from 199 populations and mapped haplotype distributions and their relationships using a haplotype network. We calculated genetic and molecular diversity statistics for the seven geographical regions from which we obtained samples. Results Fifteen haplotypes were detected, with very little divergence among them. The haplotypes are separated into two main groups by the presence or absence of a 22 bp tandem duplication. Four haplotypes are common, widespread and with substantial range overlap; 11 are rare and mostly unique to one region. Two rare haplotypes were found only in British Columbia (BC). Western North America and Asia have the highest levels of genetic and molecular diversity. Northern and southern BC have different haplotype complements. Main conclusions Bistorta vivipara has relatively low genetic diversity, with much less genetic structure than we expected for such a widespread species. We expected significant geographical structure due to the combined effects of genetic drift and geographical isolation. The asexual reproductive mode of B. vivipara may facilitate relatively rapid population establishment and spread compared with sexual reproduction by seed. Bistorta vivipara probably originated in Asia and spread to North America and Europe prior to the LGM. In western North America it spread to its modern distribution from Beringia and the western USA following the LGM. Populations in northern and southern BC may have different histories, possibly related to the timing and extent of glaciation. The occurrence of two unique haplotypes within BC suggests that some individuals may have survived in full glacial refugia within BC.

Silene acaulis has a highly dynamic history characterized by vicariance, regional extinction, and recolonization, with persistence in at least four refugia. Long-distance dispersal explains patterns across the Atlantic Ocean, but we found no evidence of dispersal across the Siberian range gap.