Hepatitis E virus genotype 3 in wild rats, United States.

The role of rodents in the epidemiology of zoonotic hepatitis E virus (HEV) infection has been a subject of considerable debate. Seroprevalence studies suggest widespread HEV infection in commensal Rattus spp. rats, but experimental transmission has been largely unsuccessful and recovery of zoonotic genotype 3 HEV RNA from wild Rattus spp. rats has never been confirmed. We surveyed R. rattus and R. norvegicus rats from across the United States and several international populations by using a hemi-nested reverse transcription PCR approach. We isolated HEV RNA in liver tissues from 35 of 446 rats examined. All but 1 of these isolates was relegated to the zoonotic HEV genotype 3, and the remaining sequence represented the recently discovered rat genotype from the United States and Germany. HEV-positive rats were detected in urban and remote localities. Genetic analyses suggest all HEV genotype 3 isolates obtained from wild Rattus spp. rats were closely related.

Invasion facilitates hybridization with introgression in the Rattus rattus species complex.

Biological invasions result in novel species interactions, which can have significant evolutionary impacts on both native and invading taxa. One evolutionary concern with invasions is hybridization among lineages that were previously isolated, but make secondary contact in their invaded range(s). Black rats, consisting of several morphologically very similar but genetically distinct taxa that collectively have invaded six continents, are arguably the most successful mammalian invaders on the planet. We used mitochondrial cytochrome b sequences, two nuclear gene sequences (Atp5a1 and DHFR) and nine microsatellite loci to examine the distribution of three invasive black rat lineages (Rattus tanezumi, Rattus rattus I and R. rattus IV) in the United States and Asia and to determine the extent of hybridization among these taxa. Our analyses revealed two mitochondrial lineages that have spread to multiple continents, including a previously undiscovered population of R. tanezumi in the south-eastern United States, whereas the third lineage (R. rattus IV) appears to be confined to Southeast Asia. Analyses of nuclear DNA (both sequences and microsatellites) suggested significant hybridization is occurring among R. tanezumi and R. rattus I in the United States and also suggest hybridization between R. tanezumi and R. rattus IV in Asia, although further sampling of the latter species pair in Asia is required. Furthermore, microsatellite analyses suggest unidirectional introgression from both R. rattus I and R. rattus IV into R. tanezumi. Within the United States, introgression appears to be occurring to such a pronounced extent that we were unable to detect any nuclear genetic signal for R. tanezumi, and a similar pattern was detected in Asia.

Lithology and disturbance drive cavefish and cave crayfish occurrence in the Ozark Highlands ecoregion.

Diverse communities of groundwater-dwelling organisms (i.e., stygobionts) are important for human wellbeing; however, we lack an understanding of the factors driving their distributions, making it difficult to protect many at-risk species. Therefore, our study objective was to determine the landscape factors related to the occurrence of cavefishes and cave crayfishes in the Ozark Highlands ecoregion, USA. We sampled cavefishes and cave crayfishes at 61 sampling units using both visual and environmental DNA surveys. We then modeled occurrence probability in relation to lithology and human disturbance while accounting for imperfect detection. Our results indicated that occurrence probability of cave crayfishes was negatively associated with human disturbance, whereas there was a weak positive relationship between cavefish occurrence and disturbance. Both cavefishes and cave crayfishes were more likely to occur in limestone rather than dolostone lithology. Our results indicate structuring factors are related to the distribution of these taxa, but with human disturbance as a prevalent modifier of distributions for cave crayfishes. Limiting human alteration near karst features may be warranted to promote the persistence of some stygobionts. Moreover, our results indicate current sampling efforts are inadequate to detect cryptic species; therefore, expanding sampling may be needed to develop effective conservation actions.

Genetic signature of reproductive manipulation in the phylogeography of the bat fly, Trichobius major.

The bat fly (Trichobius major) is a blood-feeding ectoparasite of the cave myotis (Myotis velifer). A recent mitochondrial DNA (mtDNA) study examining population structure of T. major in the South Central United States detected a single haplotype from all individuals examined (N = 48 from 12 different caves), representing one of only a few known examples of such widespread mtDNA uniformity. We examined nuclear genetic diversity using amplified fragment length polymorphism and detected high levels of nuclear genetic diversity in all populations sampled. Amplified fragment length polymorphism analyses indicated significant levels of gene flow among caves >700 km apart, suggesting the absence of mtDNA diversity in T. major is the result of a selective sweep, not a demographic event (i.e., a recent bottleneck). One mechanism by which mtDNA sweeps occur in arthropods is through bacterial parasites that manipulate host reproduction and mtDNA inheritance. We used PCR to test for the presence of all known reproductive parasites and detected a widespread infection (91.33% infection rate) of T. major with a novel Arsenophonus bacterium, as well as the infection of 2 individuals (1.16% infection rate) with a novel strain of Rickettsia. We discuss the implications for T. major phylogeography and the necessity of a bigenomic approach in arthropod population genetics.

Faster lizards sire more offspring: sexual selection on whole-animal performance.

Sexual selection operates by acting on variation in mating success. However, since selection acts on whole-organism manifestations (i.e., performance) of underlying morphological traits, tests for phenotypic effects of sexual selection should consider whole-animal performance as a substrate for sexual selection. Previous studies have revealed positive relationships between performance and survival, that is, natural selection, but none have explicitly tested whether performance may influence reproductive success (through more matings), that is, sexual selection. Performance predicts dominance in some species, implying the effects of sexual selection, but how it does so has not been established, nor is it certain whether performance might be a by-product of selection for something else, for example, elevated circulating testosterone levels. We investigated the potential for sexual selection on sprint speed performance in collared lizards (Crotaphytus collaris), considering the potential mediating effects of circulating hormone levels. Among territorial, adult male collared lizards, only sprint speed significantly predicted territory area and number of offspring sired as determined by genetic paternity analysis. Body size, head size, and hind limb length had no effect. Neither plasma testosterone levels nor corticosterone levels correlated with sprint speed, territory area, or number of offspring sired. Thus, our results provide a direct link between whole-animal performance and reproductive success, suggesting that intrasexual selection can act directly on sprint speed performance and drive the evolution of underlying morphological traits.

A new species of Cytauxzoon from Pallas' cats caught in Mongolia and comments on the systematics and taxonomy of piroplasmids.

DNA was extracted and the 18S ribosomal RNA gene was amplified and sequenced from the blood of 2 Pallas' cats (Otocolobus manul) infected with small intraerythrocytic piroplasms. Sequences of the parasite were found to be identical with that of a previously reported Cytauxzoon-like piroplasm from a Pallas' cat. Phylogenetic analyses of the parasite DNA sequences obtained from the 3 Pallas' cats to other piroplasms revealed a sister group relationship to C. felis. The mean corrected percent sequence divergence between the Pallas' cat parasite and C. felis was 1.490%, which is greater than that for most other piroplasms in which species status has been accepted. On the basis of the sequence variation, we propose to name the Pallas' cat parasite C. manul. Phylogenetic analyses of C. manul also revealed a close relationship with the Spanish Cytauxzoon-like isolate because they exhibited only 0.389% sequence divergence, yet these sequences exhibit a mean of 1.690% sequence divergence from the New World isolate of C. felis. Our phylogenetic analyses also revealed several taxonomic problems that have impeded the development of a classification that accurately reflects evolutionary history of piroplasms. As currently arranged, Babesia and Theileria are paraphyletic taxa and are in need of reorganization.

Recent studies on the characterization of Anaplasma marginale isolated from North American bison.

Anaplasma marginale (Rickettsiales: Anaplasmataceae), a tick-borne pathogen of cattle, is endemic in tropical and subtropical regions of the world. Many geographic isolates of A. marginale occur worldwide that have been identified by major surface protein (MSP) 1a, which varies in sequence and molecular weight owing to different numbers of tandem 28-29 amino acid repeats. Although serologic tests have identified American bison, Bison bison, as being infected with A. marginale, the present studies were undertaken to confirm A. marginale infection in bison, to characterize bison isolates, and to compare the phylogenetic relationship of the bison isolates with other A. marginale isolates from North America. Nine A. marginale isolates derived from Canadian bison possessed identical msp4 sequences with one characteristic silent nucleotide change. The sequence of MSP1a was determined for one Canadian and two U.S. bison isolates of A. marginale, and these isolates contained 4 and 5 tandem repeats, respectively. One U.S. bison isolate tested for infectivity proved to be infective for cattle and transmitted by Dermacentor variabilis ticks. the results of this study demonstrated that these A. marginale isolates obtained from bison were similar to ones derived from naturally infected cattle.

Anaplasma infection in free-ranging Iberian red deer in the region of Castilla-La Mancha, Spain.

Organisms in the genus Anaplasma are obligate intracellular pathogens that multiply in both vertebrate and invertebrate hosts. The type species, Anaplasma marginale, causes bovine anaplasmosis and infects erythrocytes of the vertebrate host and undergoes a complex developmental cycle in ticks which serve as biological vectors. Infected cattle, wild ruminants and ticks can all serve as reservoirs of A. marginale. In this study, hunter killed Iberian red deer (Cervus elaphus hispanicus) from the region of Castilla-La Mancha in southwestern Spain were tested for Anaplasma infection. We found that 10% of the deer examined were seropositive for Anaplasma. Three A. marginale strains were subsequently obtained from salivary glands of Hyalomma marginatum that were removed from these deer, and the sequence of the major surface protein (msp)4 gene was determined for each strain and used for phylogenetic studies. Maximum parsimony analyses of msp4 sequences from H. marginatum ticks in comparison with New World cattle and bison isolates reported previously, suggested different origins for these Spanish A. marginale strains. The results of this study demonstrated that Iberian red deer are naturally infected with Anaplasma, and may therefore serve as a wildlife reservoir of the pathogen. Although the link between deer infection and the strains of A. marginale identified in ticks was not established, H. marginatum and Rhipicephalus bursa were identified as potential biological vectors for A. marginale in this region and may effect transmission of A. marginale between deer and cattle populations.

Phylogeography of New World isolates of Anaplasma marginale based on major surface protein sequences.

Gene and protein sequences of major surface proteins (MSP) 1a and 4 of Anaplasma marginale (Rickettsiales: Anaplasmataceae) were used to infer phylogenetic relationships between New World isolates from Argentina, Brazil, Mexico and the United States. Seventeen isolates of A. marginale plus two outgroup taxa (A. centrale and A. ovis) were used for maximum-parsimony analysis of MSP4, while 20 isolates were used for phylogenetic analysis of MSP1a. msp4 analysis provided strong bootstrap support for a Latin American clade and, within this clade, support was detected for Mexican and South American clades. Isolates of A. marginale from the United States also grouped into two clades from the southern (isolates from Florida, Mississippi, and Virginia) and west-central (isolates from California, Idaho, Illinois, Oklahoma, and Texas) states. Although little phylogeographic resolution was detected within these higher clades, msp4 sequences appear to be a good genetic marker for inferring phylogeographic patterns of A. marginale isolates. In contrast to the phylogeographic resolution provided by msp4, MSP1a DNA and protein sequence were quite variable and did not provide phylogeographic resolution. Most variation in MSP1a sequences appeared unique to a given isolate and similar DNA sequence variation in msp1alpha was detected within isolates from Idaho and Florida and from Idaho and Argentina. The results of these studies demonstrated that msp4 provided phylogenetic information on the evolution of A. marginale isolates. In contrast MSP1a sequences appeared to be rapidly evolving and these sequences may provide phylogeographic information only when numerous isolate MSP1a sequences are analyzed from a geographic area.

Genetic diversity and molecular phylogeny of Anaplasma marginale isolates from Minas Gerais, Brazil.

Anaplasma marginale (Rickettsiales: Anaplasmataceae), a tick-borne pathogen of cattle, is endemic in tropical and subtropical regions of the world, and many isolates of A. marginale may occur in a given geographic area. Phylogenetic relationships have been reported for A. marginale isolates from the US using gene and protein sequences of MSP1a and msp4. These studies demonstrated that msp4 sequences, but not MSP1a DNA or protein sequences, provide phylogeographic information and also that MSP1a sequences are highly heterogeneous among A. marginale populations. However, little information is available on the genetic diversity of A. marginale isolates from other regions of the world. The present study was undertaken to examine genetic variation among 10 isolates of A. marginale obtained from infected cattle in the State of Minas Gerais, Brazil, where A. marginale is endemic. Neighbor-joining analysis of msp4 sequences of Brazilian and New World isolates of A. marginale from Argentina, Mexico and the US provided bootstrap support for a Latin American clade. The sequences of the MSP1a repeats of four Brazilian isolates of A. marginale were compared to sequences of Latin American and US isolates. The MSP1a repeated sequences of Latin American isolates of A. marginale had nine repeat forms, alpha-phi, which have not been reported previously in North American isolates of A. marginale. Furthermore, the repeated forms tau, sigma and mu were only present in the Brazilian isolates. The results demonstrated that the genetic heterogeneity observed among isolates of A. marginale is common in endemic areas, independent of the predominant tick vector and is consistent with previous studies in which msp4 provided phylogeographic information about A. marginale isolates, while MSP1a was found not to be a useful marker for phylogeographic characterization of A. marginale isolates.

An intraerythrocytic small piroplasm in wild-caught Pallas's cats (Otocolobus manul) from Mongolia.

During the quarantine examination of four Pallas's cats (Otocolobus manul) imported from Mongolia in October and December 2000, intraerythrocytic piroplasms were detected on Wright-Giemsa stained blood films that were morphologically indistinguishable from other small piroplasms of felids. Further characterization of this unknown organism via polymerase chain reaction amplification, sequencing of a portion of the 18S nuclear small subunit rRNA gene, and comparisons with orthologous sequences from other piroplasms, revealed similarity to Cytauxzoon felis. This is the first report of naturally occurring erythroparasitemia in Pallas's cats and the first documented case of naturally occurring piroplasm infections in a free-ranging felid from Mongolia.

Present and potential future distribution of common vampire bats in the Americas and the associated risk to cattle.

Success of the cattle industry in Latin America is impeded by the common vampire bat, Desmodus rotundus, through decreases in milk production and mass gain and increased risk of secondary infection and rabies. We used ecological niche modeling to predict the current potential distribution of D. rotundus and the future distribution of the species for the years 2030, 2050, and 2080 based on the A2, A1B, and B1 climate scenarios from the Intergovernmental Panel on Climate Change. We then combined the present day potential distribution with cattle density estimates to identify areas where cattle are at higher risk for the negative impacts due to D. rotundus. We evaluated our risk prediction by plotting 17 documented outbreaks of cattle rabies. Our results indicated highly suitable habitat for D. rotundus occurs throughout most of Mexico and Central America as well as portions of Venezuela, Guyana, the Brazilian highlands, western Ecuador, northern Argentina, and east of the Andes in Peru, Bolivia, and Paraguay. With future climate projections suitable habitat for D. rotundus is predicted in these same areas and additional areas in French Guyana, Suriname, Venezuela and Columbia; however D. rotundus are not likely to expand into the U.S. because of inadequate 'temperature seasonality.' Areas with large portions of cattle at risk include Mexico, Central America, Paraguay, and Brazil. Twelve of 17 documented cattle rabies outbreaks were represented in regions predicted at risk. Our present day and future predictions can help authorities focus rabies prevention efforts and inform cattle ranchers which areas are at an increased risk of cattle rabies because it has suitable habitat for D. rotundus.

Phylogeny and evolution of the Piroplasmida as inferred from 18S rRNA sequences.

The order Piroplasmida consists of several genera of tick-borne parasites that infect mammals, and to a lesser extent birds, and are therefore of medical and economic importance. Despite their importance, considerable confusion exists concerning the relationship among piroplasmid species, specifically concerning the number of genera and the intergeneric relationships. To examine evolutionary relationships among piroplasmids, we conducted phylogenetic analyses of 192 18S rDNA sequences from the genera Theileria, Babesia and Cytauxzoon. Our analyses revealed eight clades potentially representing distinct genera, and we distinguish the Duncani Group and Microti Group as genetically distinct groups of species requiring detailed analysis of morphology and life-history to allow formal generic description. The piroplasmid phylogeny revealed considerable host diversity and limited host specificity, suggesting piroplasmids have undergone frequent host switches during their evolution. Our analyses provide the first reported evolutionary timescale for piroplasmids independent of the assumption of parasite-host cospeciation, which is invalid for piroplasmids. Evolutionary rate analyses revealed considerable substitution rate heterogeneity, which we attribute to host switching and diversification. Finally, we call for a comprehensive phylogenetic, morphological and life-history analysis for these medically relevant taxa to resolve relationships and understand host specificity.

Detection and experimental transmission of a novel Babesia isolate in captive olive baboons (Papio cynocephalus anubis).

Babesia spp. are tick-transmitted apicomplexan hemoparasites that infect mammalian red blood cells. Our purpose was to determine the prevalence of Babesia infection in a colony of captive baboons and to evaluate potential experimental routes of the transmission of the hemoparasite. DNA was extracted from the blood of baboons and tested for infection with Babesia by PCR and primers that amplify the 18s rRNA gene of the parasite. The overall prevalence of infection of Babesia in the baboon population was 8.8% (73 of 830). Phylogenetic analysis of the sequenced DNA from 2 baboons revealed that the Babesia isolate found in captive baboons was a novel species most closely related (97% to 99%) to B. leo. Blood from a Babesia-infected donor baboon was inoculated intravenously, intramuscularly, or subcutaneously into 3 naive baboons. The intravenously inoculated baboon was PCR-positive at 7 d after inoculation; the 2 baboons inoculated by other routes became PCR-positive at 10 d after inoculation. All 3 baboons remained PCR-positive for Babesia through day 31. Baboons experimentally inoculated with the new Babesia isolate did not exhibit clinical signs of babesiosis during the experiments. We demonstrated that captive baboons are infected with a novel Babesia isolate. In addition we showed that Babesia can be transmitted in the absence of the organism's definitive host (ticks) by transfer of infected blood through intravenous, intramuscular, and subcutaneous routes to naive baboons.

Multiple geographic origins of commensalism and complex dispersal history of Black Rats.

The Black Rat (Rattus rattus) spread out of Asia to become one of the world's worst agricultural and urban pests, and a reservoir or vector of numerous zoonotic diseases, including the devastating plague. Despite the global scale and inestimable cost of their impacts on both human livelihoods and natural ecosystems, little is known of the global genetic diversity of Black Rats, the timing and directions of their historical dispersals, and the risks associated with contemporary movements. We surveyed mitochondrial DNA of Black Rats collected across their global range as a first step towards obtaining an historical genetic perspective on this socioeconomically important group of rodents. We found a strong phylogeographic pattern with well-differentiated lineages of Black Rats native to South Asia, the Himalayan region, southern Indochina, and northern Indochina to East Asia, and a diversification that probably commenced in the early Middle Pleistocene. We also identified two other currently recognised species of Rattus as potential derivatives of a paraphyletic R. rattus. Three of the four phylogenetic lineage units within R. rattus show clear genetic signatures of major population expansion in prehistoric times, and the distribution of particular haplogroups mirrors archaeologically and historically documented patterns of human dispersal and trade. Commensalism clearly arose multiple times in R. rattus and in widely separated geographic regions, and this may account for apparent regionalism in their associated pathogens. Our findings represent an important step towards deeper understanding the complex and influential relationship that has developed between Black Rats and humans, and invite a thorough re-examination of host-pathogen associations among Black Rats.

Molecular systematics of Hispaniolan pupfishes (Cyprinodontidae: Cyprinodon): implications for the biogeography of insular Caribbean fishes.

We used sequence variation in the mtDNA control-region and ND2 and cyt b genes to assess the systematics and biogeography of the five species of pupfish (Cyprinodon) on Hispaniola. These include four endemics, the relatively large-bodied Cyprinodon bondi, Cyprinodon nichollsi, and Cyprinodon sp., each from a separate lake in southwestern Hispaniola, and Cyprinodon higuey from a coastal lake in eastern Hispaniola. The fifth species consists of coastal populations referable to Cyprinodon variegatus riverendi. The results indicate that Hispaniola has been invaded by at least two forms, first by a late Pliocene progenitor of Cyprinodon variegatus ovinus and the large-bodied Hispaniolan species, and, more recently, by one or more ancestral forms allied with Cyprinodon variegatus variegatus and C. v. riverendi. Levels of divergence indicate that large expanses of open sea have not acted as long-term barriers to inter-island dispersal of cyprinodontiform fishes. This study, together with the molecular systematics of other insular Caribbean fishes, indicates that most insular groups originated from late Neogene dispersal from the mainland. The patterns of mtDNA variation in Cyprinodon showed little congruence with the species/subspecies taxonomy.

Characterization of genetic diversity in Dermacentor andersoni (Acari: Ixodidae) with body size and weight polymorphism.

Morphological and discrete genetic differences are found between geographically isolated, allopatric, tick populations. However, we have found differences in sympatric tick populations. Notable differences were found in the body size and weight of Dermacentor andersoni collected from a single location in Montana, USA. These ticks were separated in groups consisting of big (B) and small (S) individuals. The objectives of this study were: (a) to characterize genetic diversity in B and S D. andersoni individuals, (b) to evaluate transmissibility of the character associated with body size and weight, and (c) to correlate morphological differences with biological, physiological, and behavioral characteristics. We found extensive genetic variation in 16S rDNA and ITS2 loci in B and S ticks and demonstrated genetic differentiation between B and S individuals. We further provide some support for Mendelian autosomal dominant transmission of characters associated with tick body size and weight. The results reported herein show that B ticks have a better reproductive success than S ticks and suggest partial reproductive isolation of S ticks.

Utility of the dentin matrix protein 1 (DMP1) gene for resolving mammalian intraordinal phylogenetic relationships.

We sequenced exon 6 of the nuclear dentin matrix protein 1 (DMP1) gene from 19 species of bats (order Chiroptera) to assess the utility of this gene for higher-level phylogenetic studies. Bayesian analysis revealed high support (posterior probabilities >/=0.95) for monophyly of Noctilionoidea (Phyllostomidae, Noctilionidae, and Mormoopidae), all genera and most families examined. Comparison of the phylogenetic information present in DMP1 with mitochondrial rDNA and nuclear RAG2 genes indicated no significant heterogeneity. Thus, we concatenated these three data sets into a single "total evidence" phylogenetic analysis. Combined analysis was congruent with study of RAG2 and combined RAG2 and mtrDNA sequences, but improved support (Bayesian posterior probabilities) for many nodes. Our results indicate that exon 6 of DMP1 is rapidly evolving, able to tolerate non-frame shifting insertion and deletion events, is more variable than RAG2, and provides phylogenetic resolution from the interfamilial to infraclass levels in mammals.

Characterization and phylogenetic utility of the mammalian protamine p1 gene.

We sequenced the protamine P1 gene (ca. 450 bp) from 20 bats (order Chiroptera) and the flying lemur (order Dermoptera). We compared these sequences with published sequences from 19 other mammals representing seven orders (Artiodactyla, Carnivora, Cetacea, Perissodactyla, Primates, Proboscidea, and Rodentia) to assess structure, base compositional bias, and phylogenetic utility. Approximately 80% of second codon positions were guanine, resulting in protamine proteins containing a high frequency of arginine residues. Our data indicate that codon usage for arginine differs among higher mammalian taxa. Parsimony analysis of 40 species representing nine orders produced a well-resolved tree in which most nodes were supported strongly, except at the lowest taxonomic levels (e.g., within Artiodactyla and Vespertilionidae). These data support monophyly of several taxa proposed by morphologic and molecular studies (all nine orders: Laurasiatheria, Cetartiodactytla, Yangochiroptera, Noctilionoidea, Rhinolophoidea, Vespertilionoidea, Phyllostomidae, Natalidae, and Vespertilionidae) and, in agreement with recent molecular studies, reject monophyly of Archonta, Volitantia, and Microchiroptera. Bats were sister to a clade containing Perissodactyla, Carnivora, and Cetartiodactyla, and, although not unequivocally, rhinolophoid bats (traditional microchiropterans) were sister to megachiropterans. Sequences of the protamine P1 gene are useful for resolving relationships at and above the familial level in bats, and generally within and among mammalian orders, but with some drawbacks. The coding and intervening sequences are small, producing few phylogenetically informative characters, and aligning the intron is difficult, even among closely related families. Given these caveats, the protamine P1 gene may be important to future systematic studies because its functional and evolutionary constraints differ from other genes currently used in systematic studies.

Utility of chromosomal position of heterochromatin as a biomarker of radiation-induced genetic damage: a study of Chornobyl voles (Microtus sp.).

Biomarkers that effectively document effects of chronic multi-generational exposure to contaminated environments on chromosomes would be valuable in risk assessment, remediation, and environmental decisions. Native, free-ranging populations of voles inhabiting the highly radioactive regions surrounding Reactor 4 of the Chornobyl Nuclear Power Station provide a model system to evaluate biological and chromosomal effects of chronic multi-generational exposure to radioactivity and other reactor meltdown-related pollutants. Here, we explore the utility of heterochromatic elements as potentially informative biomarkers for genetic damage in voles from the radioactive environments surrounding Chornobyl. We analyzed chromosomal positions of heterochromatin from Microtus arvalis and M. rossiaemeridionalis using fluorescent in situ hybridization. Although intrapopulational variation existed in chromosomal position and abundance of heterochromatin, none of that variation could be assigned to environmental exposure.