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1.
J Med Entomol ; 2024 Apr 18.
Artículo en Inglés | MEDLINE | ID: mdl-38635291

RESUMEN

The cosmopolitan ectoparasite human head louse, Pediculus humanus capitis (De Geer)(Phthiraptera:Pediculidae), affects mostly school-aged children, with infestations reported every year mainly due to louse resistance to pyrethroids. One of the main resistance mechanisms of pyrethroids is the target site insensitivity (kdr), which is caused by single-nucleotide point mutations (SNPs) located in the voltage-sensitive sodium channel gene. In this study, we analyzed individual head lice toxicologically via the description of their susceptibility profile to permethrin and genetically through the genotypification of their kdr alleles as well as nuclear microsatellite loci. Lice were collected from 4 schools in the city of Buenos Aires, Argentina. The resistance ratios varied from 33.3% to 71.4%, with a frequency of the T917I kdr mutation of 87.31% and with 83.6% of the head lice being homozygous resistant to pyrethroids. Microsatellite data indicated that all the louse school populations had genotype proportions that deviated from Hardy-Weinberg expectations, with FIS > 0 reflecting a deficit of heterozygotes. Bottleneck analysis suggested that all louse school populations underwent a recent reduction in population sizes, while 3 of the 4 schools had gene flow values around 1, indicating ongoing gene flow among those schools. Our study suggests that school louse populations in the city of Buenos Aires may form a metapopulation, where each school represents a small population that undergoes extinction and recolonization processes under strong permethrin selection. This is the first multilevel analysis integrating toxicological, kdr-genotyping, and microsatellite data in human louse populations.

2.
Mol Biol Evol ; 41(4)2024 Apr 02.
Artículo en Inglés | MEDLINE | ID: mdl-38513084

RESUMEN

Insects have repeatedly forged symbioses with heritable microbes, gaining novel traits. For the microbe, the transition to symbioses can lead to the degeneration of the symbiont's genome through transmission bottlenecks, isolation, and the loss of DNA repair enzymes. However, some insect-microbial symbioses have persisted for millions of years, suggesting that natural selection slows genetic drift and maintains functional consistency between symbiont populations. By sampling in multiple countries, we examine genomic diversity within a symbiont species, a heritable symbiotic bacterium found only in human head lice. We find that human head louse symbionts contain genetic diversity that appears to have arisen contemporaneously with the appearance of anatomically modern humans within Africa and/or during the colonization of Eurasia by humans. We predict that the observed genetic diversity underlies functional differences in extant symbiont lineages, through the inactivation of genes involved in symbiont membrane construction. Furthermore, we find evidence of additional gene losses prior to the appearance of modern humans, also impacting the symbiont membrane. From this, we conclude that symbiont genome degeneration is proceeding, via gene inactivation and subsequent loss, in human head louse symbionts, while genomic diversity is maintained. Collectively, our results provide a look into the genomic diversity within a single symbiont species and highlight the shared evolutionary history of humans, lice, and bacteria.


Asunto(s)
Hominidae , Pediculus , Animales , Humanos , Pediculus/genética , Filogenia , Genoma Bacteriano , Evolución Molecular , Bacterias/genética , Genómica , Hominidae/genética , Insectos/genética , Simbiosis/genética
3.
Insects ; 14(12)2023 Nov 21.
Artículo en Inglés | MEDLINE | ID: mdl-38132575

RESUMEN

Microsporidia are natural pathogens of arthropods and have been used as biological control against insect pests. In the United States, efforts to control the invasive Red Imported Fire Ant, Solenopsis invicta, and Black Imported Fire Ant, Solenopsis richteri, have included the use of the microsporidium, Kneallhazia solenopsae. However, there is limited information about the genetic differences among the microsporidian variants found in S. invicta and in S. richteri. In this study, we assessed the prevalence and genetic diversity of K. solenopsae in native populations of S. richteri in Argentina (South America). Additionally, we examined the social parasitic ant, Solenopsis daguerrei, which is found in some S. richteri nests, for the presence of this microsporidium. The survey of 219 S. richteri nests revealed K. solenopsae infections in all five sites analyzed, with 28 colonies (12.8%) positive for the microsporidium. Among the 180 S. daguerrei individuals collected, seven ants (3.9%) from three sites tested positive for K. solenopsae. Phylogenetic analyses of the microsporidian variants present in S. richteri and S. daguerrei based on partial small subunit ribosomal gene sequences (SSU rRNA) showed that both ant species shared the same variant, which is different from the ones found in S. invicta. Further studies are needed to determine the pathogenicity of genetically different K. solenopsae variants among Solenopsis species.

4.
PLoS One ; 18(11): e0293409, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37939041

RESUMEN

The human louse, Pediculus humanus, is an obligate blood-sucking ectoparasite that has coevolved with humans for millennia. Given the intimate relationship between this parasite and the human host, the study of human lice has the potential to shed light on aspects of human evolution that are difficult to interpret using other biological evidence. In this study, we analyzed the genetic variation in 274 human lice from 25 geographic sites around the world by using nuclear microsatellite loci and female-inherited mitochondrial DNA sequences. Nuclear genetic diversity analysis revealed the presence of two distinct genetic clusters I and II, which are subdivided into subclusters: Ia-Ib and IIa-IIb, respectively. Among these samples, we observed the presence of the two most common louse mitochondrial haplogroups: A and B that were found in both nuclear Clusters I and II. Evidence of nuclear admixture was uncommon (12%) and was predominate in the New World potentially mirroring the history of colonization in the Americas. These findings were supported by novel DIYABC simulations that were built using both host and parasite data to define parameters and models suggesting that admixture between cI and cII was very recent. This pattern could also be the result of a reproductive barrier between these two nuclear genetic clusters. In addition to providing new evolutionary knowledge about this human parasite, our study could guide the development of new analyses in other host-parasite systems.


Asunto(s)
Infestaciones por Piojos , Pediculus , Animales , Humanos , Femenino , Pediculus/genética , Filogenia , Infestaciones por Piojos/genética , Infestaciones por Piojos/parasitología , ADN Mitocondrial/genética , Variación Genética
5.
Int J Dermatol ; 60(3): 272-280, 2021 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-32767380

RESUMEN

Head louse infestations continue to be a concern of public health in most countries, including the most developed ones. The present recommendations are intended to inform and stress the role and impact of the different authorities, institutions, industry, and the public in the control of head lice in order to reduce the prevalence of this parasite. We encourage health authorities to pursue more effective methods to correctly identify such infestations, and evaluate existing and new pediculicides, medical devices, louse repellents, and louse- and nit-removal remedies. Pediculicides and medical devices must have verifiable claims in the instructions for use and should be tested periodically to document current levels of resistance by lice to the active ingredients and to the formulated products. Where the prevalence of lice is claimed to be epidemic, children should be periodically evaluated objectively to document the actual level of prevalence. Continuing education for health providers and the general population promises to correct misinformation regarding the biology, prevention, and management of lice. Parents should regularly inspect their children for head lice and treat as necessary. Health authorities are encouraged to eliminate policies and practices that rely upon school exclusion as a means to reduce incidence and prevalence, e.g., the 'no-nit' policy which lacks scientific justification, and are counterproductive to the health and welfare of children.


Asunto(s)
Infestaciones por Piojos , Pediculus , Dermatosis del Cuero Cabelludo , Animales , Niño , Humanos , Infestaciones por Piojos/diagnóstico , Infestaciones por Piojos/tratamiento farmacológico , Infestaciones por Piojos/epidemiología , Prevalencia , Salud Pública , Dermatosis del Cuero Cabelludo/diagnóstico , Dermatosis del Cuero Cabelludo/epidemiología , Dermatosis del Cuero Cabelludo/prevención & control , Instituciones Académicas
6.
J Parasitol ; 105(4): 555-566, 2019 08.
Artículo en Inglés | MEDLINE | ID: mdl-31348717

RESUMEN

Dispersal influences the evolution and adaptation of organisms, but it can be difficult to detect. Host-specific parasites provide information about the dispersal of their hosts and may be valuable for examining host dispersal that does not result in gene flow or that has low signals of gene flow. We examined the population connectivity of the buffy flower bat, Erophylla sezekorni (Chiroptera: Phyllostomidae), and its associated obligate ectoparasite, Trichobius frequens (Diptera: Streblidae), across a narrow oceanic channel in The Bahamas that has previously been implicated as a barrier to dispersal in bats. Due to the horizontal transmission of T. frequens, we were able to test the hypothesis that bats are dispersing across this channel, but this dispersal does not result in gene flow, occurs rarely, or started occurring recently. We developed novel microsatellite markers for the family Streblidae in combination with previously developed markers for bats to genotype individuals from 4 islands in The Bahamas. We provide evidence for a single population of the host, E. sezekorni, but 2 populations of its bat flies, potentially indicating a recent reduction of gene flow in E. sezekorni, rare dispersal, or infrequent transportation of bat flies with their hosts. Despite high population differentiation in bat flies indicated by microsatellites, mitochondrial DNA shows no polymorphism, suggesting that bacterial reproductive parasites may be contributing to mitochondrial DNA sweeps. Parasites, including bat flies, provide independent information about their hosts and can be used to test hypotheses of host dispersal that may be difficult to assess using host genetics alone.


Asunto(s)
Distribución Animal/fisiología , Quirópteros/fisiología , Quirópteros/parasitología , Dípteros/fisiología , Infestaciones Ectoparasitarias/veterinaria , Algoritmos , Alelos , Animales , Bahamas , Teorema de Bayes , Análisis por Conglomerados , Secuencia de Consenso , ADN Mitocondrial/química , Dípteros/genética , Dípteros/microbiología , Infestaciones Ectoparasitarias/parasitología , Complejo IV de Transporte de Electrones/química , Complejo IV de Transporte de Electrones/genética , Interacciones Huésped-Parásitos , Cadenas de Markov , Alineación de Secuencia/veterinaria , Wolbachia/fisiología
7.
Ecol Evol ; 7(19): 7585-7598, 2017 10.
Artículo en Inglés | MEDLINE | ID: mdl-29043016

RESUMEN

Dispersal is a driving factor in the creation and maintenance of biodiversity, yet little is known about the effects of habitat variation and geography on dispersal and population connectivity in most mammalian groups. Bats of the family Molossidae are fast-flying mammals thought to have potentially high dispersal ability, and recent studies have indicated gene flow across hundreds of kilometers in continental North American populations of the Brazilian free-tailed bat, Tadarida brasiliensis. We examined the population genetics, phylogeography, and morphology of this species in Florida and across islands of The Bahamas, which are part of an island archipelago in the West Indies. Previous studies indicate that bats in the family Phyllostomidae, which are possibly less mobile than members of the family Molossidae, exhibit population structuring across The Bahamas. We hypothesized that T. brasiliensis would show high population connectivity throughout the islands and that T. brasiliensis would show higher connectivity than two species of phyllostomid bats that have been previously examined in The Bahamas. Contrary to our predictions, T. brasiliensis shows high population structure between two groups of islands in The Bahamas, similar to the structure exhibited by one species of phyllostomid bat. Phylogenetic and morphological analyses suggest that this structure may be the result of ancient divergence between two populations of T. brasiliensis that subsequently came into contact in The Bahamas. Our findings additionally suggest that there may be cryptic species within T. brasiliensis in The Bahamas and the West Indies more broadly.

8.
Mol Biol Evol ; 34(7): 1743-1757, 2017 07 01.
Artículo en Inglés | MEDLINE | ID: mdl-28419279

RESUMEN

Insects with restricted diets rely on symbiotic bacteria to provide essential metabolites missing in their diet. The blood-sucking lice are obligate, host-specific parasites of mammals and are themselves host to symbiotic bacteria. In human lice, these bacterial symbionts supply the lice with B-vitamins. Here, we sequenced the genomes of symbiotic and heritable bacterial of human, chimpanzee, gorilla, and monkey lice and used phylogenomics to investigate their evolutionary relationships. We find that these symbionts have a phylogenetic history reflecting the louse phylogeny, a finding contrary to previous reports of symbiont replacement. Examination of the highly reduced symbiont genomes (0.53-0.57 Mb) reveals much of the genomes are dedicated to vitamin synthesis. This is unchanged in the smallest symbiont genome and one that appears to have been reorganized. Specifically, symbionts from human lice, chimpanzee lice, and gorilla lice carry a small plasmid that encodes synthesis of vitamin B5, a vitamin critical to the bacteria-louse symbiosis. This plasmid is absent in an old world monkey louse symbiont, where this pathway is on its primary chromosome. This suggests the unique genomic configuration brought about by the plasmid is not essential for symbiosis, but once obtained, it has persisted for up to 25 My. We also find evidence that human, chimpanzee, and gorilla louse endosymbionts have lost a pathway for synthesis of vitamin B1, whereas the monkey louse symbiont has retained this pathway. It is unclear whether these changes are adaptive, but they may point to evolutionary responses of louse symbionts to shifts in primate biology.


Asunto(s)
Anoplura/genética , Pediculus/genética , Simbiosis/genética , Animales , Bacterias/genética , Evolución Biológica , Evolución Molecular , Genoma Bacteriano , Genómica/métodos , Hominidae/genética , Humanos , Pan troglodytes/genética , Filogenia , Plásmidos/genética , Primates/genética , Análisis de Secuencia de ADN/métodos
9.
Syst Biol ; 66(5): 786-798, 2017 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-28123117

RESUMEN

Novel sequencing technologies are rapidly expanding the size of data sets that can be applied to phylogenetic studies. Currently the most commonly used phylogenomic approaches involve some form of genome reduction. While these approaches make assembling phylogenomic data sets more economical for organisms with large genomes, they reduce the genomic coverage and thereby the long-term utility of the data. Currently, for organisms with moderate to small genomes ($<$1000 Mbp) it is feasible to sequence the entire genome at modest coverage ($10-30\times$). Computational challenges for handling these large data sets can be alleviated by assembling targeted reads, rather than assembling the entire genome, to produce a phylogenomic data matrix. Here we demonstrate the use of automated Target Restricted Assembly Method (aTRAM) to assemble 1107 single-copy ortholog genes from whole genome sequencing of sucking lice (Anoplura) and out-groups. We developed a pipeline to extract exon sequences from the aTRAM assemblies by annotating them with respect to the original target protein. We aligned these protein sequences with the inferred amino acids and then performed phylogenetic analyses on both the concatenated matrix of genes and on each gene separately in a coalescent analysis. Finally, we tested the limits of successful assembly in aTRAM by assembling 100 genes from close- to distantly related taxa at high to low levels of coverage.Both the concatenated analysis and the coalescent-based analysis produced the same tree topology, which was consistent with previously published results and resolved weakly supported nodes. These results demonstrate that this approach is successful at developing phylogenomic data sets from raw genome sequencing reads. Further, we found that with coverages above $5-10\times$, aTRAM was successful at assembling 80-90% of the contigs for both close and distantly related taxa. As sequencing costs continue to decline, we expect full genome sequencing will become more feasible for a wider array of organisms, and aTRAM will enable mining of these genomic data sets for an extensive variety of applications, including phylogenomics. [aTRAM; gene assembly; genome sequencing; phylogenomics.].


Asunto(s)
Clasificación/métodos , Genómica/métodos , Filogenia , Análisis de Secuencia
10.
PeerJ ; 4: e2187, 2016.
Artículo en Inglés | MEDLINE | ID: mdl-27547523

RESUMEN

Phylogenetic trees can reveal the origins of endosymbiotic lineages of bacteria and detect patterns of co-evolution with their hosts. Although taxon sampling can greatly affect phylogenetic and co-evolutionary inference, most hypotheses of endosymbiont relationships are based on few available bacterial sequences. Here we examined how different sampling strategies of Gammaproteobacteria sequences affect estimates of the number of endosymbiont lineages in parasitic sucking lice (Insecta: Phthirapatera: Anoplura). We estimated the number of louse endosymbiont lineages using both newly obtained and previously sequenced 16S rDNA bacterial sequences and more than 42,000 16S rDNA sequences from other Gammaproteobacteria. We also performed parametric and nonparametric bootstrapping experiments to examine the effects of phylogenetic error and uncertainty on these estimates. Sampling of 16S rDNA sequences affects the estimates of endosymbiont diversity in sucking lice until we reach a threshold of genetic diversity, the size of which depends on the sampling strategy. Sampling by maximizing the diversity of 16S rDNA sequences is more efficient than randomly sampling available 16S rDNA sequences. Although simulation results validate estimates of multiple endosymbiont lineages in sucking lice, the bootstrap results suggest that the precise number of endosymbiont origins is still uncertain.

11.
Appl Environ Microbiol ; 82(11): 3185-97, 2016 06 01.
Artículo en Inglés | MEDLINE | ID: mdl-26994086

RESUMEN

UNLABELLED: Roughly 10% to 15% of insect species host heritable symbiotic bacteria known as endosymbionts. The lice parasitizing mammals rely on endosymbionts to provide essential vitamins absent in their blood meals. Here, we describe two bacterial associates from a louse, Proechinophthirus fluctus, which is an obligate ectoparasite of a marine mammal. One of these is a heritable endosymbiont that is not closely related to endosymbionts of other mammalian lice. Rather, it is more closely related to endosymbionts of the genus Sodalis associated with spittlebugs and feather-chewing bird lice. Localization and vertical transmission of this endosymbiont are also more similar to those of bird lice than to those of other mammalian lice. The endosymbiont genome appears to be degrading in symbiosis; however, it is considerably larger than the genomes of other mammalian louse endosymbionts. These patterns suggest the possibility that this Sodalis endosymbiont might be recently acquired, replacing a now-extinct, ancient endosymbiont. From the same lice, we also identified an abundant bacterium belonging to the genus Rickettsia that is closely related to Rickettsia ricketsii, a human pathogen vectored by ticks. No obvious masses of the Rickettsia bacterium were observed in louse tissues, nor did we find any evidence of vertical transmission, so the nature of its association remains unclear. IMPORTANCE: Many insects are host to heritable symbiotic bacteria. These heritable bacteria have been identified from numerous species of parasitic lice. It appears that novel symbioses have formed between lice and bacteria many times, with new bacterial symbionts potentially replacing existing ones. However, little was known about the symbionts of lice parasitizing marine mammals. Here, we identified a heritable bacterial symbiont in lice parasitizing northern fur seals. This bacterial symbiont appears to have been recently acquired by the lice. The findings reported here provide insights into how new symbioses form and how this lifestyle is shaping the symbiont genome.


Asunto(s)
Anoplura/microbiología , Enterobacteriaceae/aislamiento & purificación , Enterobacteriaceae/fisiología , Rickettsia/aislamiento & purificación , Simbiosis , Animales , Enterobacteriaceae/genética , Lobos Marinos/parasitología , Genoma Bacteriano
12.
J Clin Sleep Med ; 12(2): 263-6, 2016 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-26194727

RESUMEN

ABSTRACT: Inconsistency in operationally defining sleep efficiency (SE) creates confusion with regard to the conceptualization and use of the construct by researchers and clinicians. The source of the inconsistency is the denominator of the widely published operational definition of SE: ratio of total sleep time (TST) to time in bed (TIB) (multiplied by 100 to yield a percentage). When taken literally, TIB includes non-sleep-related activity (e.g., reading, texting, conversing with a partner, watching television) both prior to initiating sleep and after the final awakening. However, the construct of SE refers to TST compared to the amount of time spent attempting to initially fall asleep and sleep discontinuity. Non-sleep related activities in bed do not reflect that construct. Also, time out of bed during nighttime awakenings, a manifestation of sleep discontinuity, should be included in the SE denominator. Using TIB as the denominator can also create a methodological problem when SE is an outcome measure in sleep intervention research. It is proposed that research and practice would benefit by clarifying and adopting a consistent operational definition that more accurately captures the construct of SE. An alternate denominator, duration of the sleep episode (DSE), is suggested, where DSE = sleep onset latency (SOL) + TST + time awake after initial sleep onset but before the final awakening (WASO) + time attempting to sleep after final awakening (TASAFA). The proposed formula for SE would be: SE = TST / DSE (× 100). DSE can be easily calculated using standard sleep diary entries along with one item from the Expanded Consensus Sleep Diary. Implications for insomnia research and practice are discussed.


Asunto(s)
Sueño/fisiología , Humanos , Higiene del Sueño/fisiología , Medicina del Sueño/métodos , Medicina del Sueño/normas , Factores de Tiempo
13.
G3 (Bethesda) ; 4(11): 2189-95, 2014 Sep 11.
Artículo en Inglés | MEDLINE | ID: mdl-25213693

RESUMEN

The obligate-heritable endosymbionts of insects possess some of the smallest known bacterial genomes. This is likely due to loss of genomic material during symbiosis. The mode and rate of this erosion may change over evolutionary time: faster in newly formed associations and slower in long-established ones. The endosymbionts of human and anthropoid primate lice present a unique opportunity to study genome erosion in newly established (or young) symbionts. This is because we have a detailed phylogenetic history of these endosymbionts with divergence dates for closely related species. This allows for genome evolution to be studied in detail and rates of change to be estimated in a phylogenetic framework. Here, we sequenced the genome of the chimpanzee louse endosymbiont (Candidatus Riesia pediculischaeffi) and compared it with the closely related genome of the human body louse endosymbiont. From this comparison, we found evidence for recent genome erosion leading to gene loss in these endosymbionts. Although gene loss was detected, it was not significantly greater than in older endosymbionts from aphids and ants. Additionally, we searched for genes associated with B-vitamin synthesis in the two louse endosymbiont genomes because these endosymbionts are believed to synthesize essential B vitamins absent in the louse's diet. All of the expected genes were present, except those involved in thiamin synthesis. We failed to find genes encoding for proteins involved in the biosynthesis of thiamin or any complete exogenous means of salvaging thiamin, suggesting there is an undescribed mechanism for the salvage of thiamin. Finally, genes encoding for the pantothenate de novo biosynthesis pathway were located on a plasmid in both taxa along with a heat shock protein. Movement of these genes onto a plasmid may be functionally and evolutionarily significant, potentially increasing production and guarding against the deleterious effects of mutation. These data add to a growing resource of obligate endosymbiont genomes and to our understanding of the rate and mode of genome erosion in obligate animal-associated bacteria. Ultimately sequencing additional louse p-endosymbiont genomes will provide a model system for studying genome evolution in obligate host associated bacteria.


Asunto(s)
Enterobacteriaceae/genética , Evolución Molecular , Genoma Bacteriano , Simbiosis/genética , Animales , Enterobacteriaceae/patogenicidad , Eliminación de Gen , Proteínas de Choque Térmico/genética , Humanos , Pan troglodytes/parasitología , Ácido Pantoténico/biosíntesis , Ácido Pantoténico/genética , Phthiraptera/microbiología , Phthiraptera/patogenicidad , Tiamina/biosíntesis , Tiamina/genética
14.
Proc Biol Sci ; 281(1777): 20132174, 2014 Feb 22.
Artículo en Inglés | MEDLINE | ID: mdl-24403325

RESUMEN

The rate of DNA mutation and divergence is highly variable across the tree of life. However, the reasons underlying this variation are not well understood. Comparing the rates of genetic changes between hosts and parasite lineages that diverged at the same time is one way to begin to understand differences in genetic mutation and substitution rates. Such studies have indicated that the rate of genetic divergence in parasites is often faster than that of their hosts when comparing single genes. However, the variation in this relative rate of molecular evolution across different genes in the genome is unknown. We compared the rate of DNA sequence divergence between humans, chimpanzees and their ectoparasitic lice for 1534 protein-coding genes across their genomes. The rate of DNA substitution in these orthologous genes was on average 14 times faster for lice than for humans and chimpanzees. In addition, these rates were positively correlated across genes. Because this correlation only occurred for substitutions that changed the amino acid, this pattern is probably produced by similar functional constraints across the same genes in humans, chimpanzees and their ectoparasites.


Asunto(s)
Pan troglodytes/genética , Pan troglodytes/parasitología , Pediculus/fisiología , Animales , Evolución Molecular , Femenino , Genoma Mitocondrial , Humanos , Datos de Secuencia Molecular , Pediculus/genética , Alineación de Secuencia , Análisis de Secuencia de ADN , Uganda
15.
Am J Phys Anthropol ; 152(1): 118-29, 2013 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-23900879

RESUMEN

Anthropological studies suggest that the genetic makeup of human populations in the Americas is the result of diverse processes including the initial colonization of the continent by the first people plus post-1492 European migrations. Because of the recent nature of some of these events, understanding the geographical origin of American human diversity is challenging. However, human parasites have faster evolutionary rates and larger population sizes allowing them to maintain greater levels of genetic diversity than their hosts. Thus, we can use human parasites to provide insights into some aspects of human evolution that may be unclear from direct evidence. In this study, we analyzed mitochondrial DNA (mtDNA) sequences from 450 head lice in the Americas. Haplotypes clustered into two well-supported haplogroups, known as A and B. Haplogroup frequencies differ significantly among North, Central and South America. Within each haplogroup, we found evidence of demographic expansions around 16,000 and 20,000 years ago, which correspond broadly with those estimated for Native Americans. The parallel timing of demographic expansions of human lice and Native Americans plus the contrasting pattern between the distribution of haplogroups A and B through the Americas suggests that human lice can provide additional evidence about the human colonization of the New World.


Asunto(s)
ADN Mitocondrial/genética , Infestaciones por Piojos/parasitología , Pediculus/clasificación , Américas , Análisis de Varianza , Animales , Antropología Física , Ciclooxigenasa 1/genética , ADN Mitocondrial/análisis , Emigración e Inmigración , Evolución Molecular , Genes de Insecto , Variación Genética , Haplotipos , Humanos , Pediculus/genética , Filogenia
16.
BMC Evol Biol ; 13: 109, 2013 May 31.
Artículo en Inglés | MEDLINE | ID: mdl-23725492

RESUMEN

BACKGROUND: Many groups of insects have obligate bacterial symbionts that are vertically transmitted. Such associations are typically characterized by the presence of a monophyletic group of bacteria living in a well-defined host clade. In addition the phylogeny of the symbiotic bacteria is typically congruent with that of the host, signifying co-speciation. Here we show that bacteria living in a single genus of feather lice, Columbicola (Insecta: Phthiraptera), present an exception to this typical pattern. RESULTS: The phylogeny of Columbicola spp. symbionts revealed the presence of three candidate clades, with the most species-rich clade having a comb-like topology with very short internodes and long terminal branches. Evolutionary simulations indicate that this topology is characteristic of a process of repeated symbiont replacement over a brief time period. The two remaining candidate clades in our study exhibit high levels of nucleotide substitution, suggesting accelerated molecular evolution due to relaxed purifying selection or smaller effective population size, which is typical of many vertically transmitted insect symbionts. Representatives of the fast-evolving and slow-evolving symbiont lineages exhibit the same localization, migration, and transmission patterns in their hosts, implying direct replacement. CONCLUSIONS: Our findings suggest that repeated, independent symbiont replacements have taken place over the course of the relatively recent radiation of Columbicola spp. These results are compatible with the notion that lice and other insects have the capability to acquire novel symbionts through the domestication of progenitor strains residing in their local environment.


Asunto(s)
Bacterias/clasificación , Fenómenos Fisiológicos Bacterianos , Ischnocera/microbiología , Ischnocera/fisiología , Filogenia , Simbiosis , Animales , Bacterias/genética , Bacterias/aislamiento & purificación , Secuencia de Bases , Evolución Molecular , Datos de Secuencia Molecular
17.
Ecol Evol ; 3(6): 1603-13, 2013 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-23789071

RESUMEN

We evaluated the mtDNA divergence and relationships within Geomys pinetis to assess the status of formerly recognized Geomys taxa. Additionally, we integrated new hypothesis-based tests in ecological niche models (ENM) to provide greater insight into causes for divergence and potential barriers to gene flow in Southeastern United States (Alabama, Florida, and Georgia). Our DNA sequence dataset confirmed and strongly supported two distinct lineages within G. pinetis occurring east and west of the ARD. Divergence date estimates showed that eastern and western lineages diverged about 1.37 Ma (1.9 Ma-830 ka). Predicted distributions from ENMs were consistent with molecular data and defined each population east and west of the ARD with little overlap. Niche identity and background similarity tests were statistically significant suggesting that ENMs from eastern and western lineages are not identical or more similar than expected based on random localities drawn from the environmental background. ENMs also support the hypothesis that the ARD represents a ribbon of unsuitable climate between more suitable areas where these populations are distributed. The estimated age of divergence between eastern and western lineages of G. pinetis suggests that the divergence was driven by climatic conditions during Pleistocene glacial-interglacial cycles. The ARD at the contact zone of eastern and western lineages of G. pinetis forms a significant barrier promoting microgeographic isolation that helps maintain ecological and genetic divergence.

18.
PLoS One ; 8(2): e57619, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-23460886

RESUMEN

Understanding the evolution of parasites is important to both basic and applied evolutionary biology. Knowledge of the genetic structure of parasite populations is critical for our ability to predict how an infection can spread through a host population and for the design of effective control methods. However, very little is known about the genetic structure of most human parasites, including the human louse (Pediculus humanus). This species is composed of two ecotypes: the head louse (Pediculus humanus capitis De Geer), and the clothing (body) louse (Pediculus humanus humanus Linnaeus). Hundreds of millions of head louse infestations affect children every year, and this number is on the rise, in part because of increased resistance to insecticides. Clothing lice affect mostly homeless and refugee-camp populations and although they are less prevalent than head lice, the medical consequences are more severe because they vector deadly bacterial pathogens. In this study we present the first assessment of the genetic structure of human louse populations by analyzing the nuclear genetic variation at 15 newly developed microsatellite loci in 93 human lice from 11 sites in four world regions. Both ecotypes showed heterozygote deficits relative to Hardy-Weinberg equilibrium and high inbreeding values, an expected pattern given their parasitic life history. Bayesian clustering analyses assigned lice to four distinct genetic clusters that were geographically structured. The low levels of gene flow among louse populations suggested that the evolution of insecticide resistance in lice would most likely be affected by local selection pressures, underscoring the importance of tailoring control strategies to population-specific genetic makeup and evolutionary history. Our panel of microsatellite markers provides powerful data to investigate not only ecological and evolutionary processes in lice, but also those in their human hosts because of the long-term coevolutionary association between lice and humans.


Asunto(s)
Núcleo Celular/genética , Variación Genética , Geografía , Endogamia , Pediculus/genética , Animales , Bases de Datos de Ácidos Nucleicos , Flujo Génico/genética , Sitios Genéticos/genética , Genética de Población , Humanos , Repeticiones de Microsatélite/genética , Familia de Multigenes/genética , Filogenia , Polimorfismo Genético , Selección Genética
19.
Phytopathology ; 102(10): 924-36, 2012 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-22957819

RESUMEN

This is the first comprehensive study of a collection of Ralstonia solanacearum strains from the southeastern United States to be characterized based on biovar, pathogenicity, hypersensitive reaction on tobacco, and phylogenetic analyses of the egl sequence. Rigorous phylogenetic analysis of the commonly used egl gene produced robust phylogenies that differed significantly from a neighbor-joining tree differed from and previously published phylogenies for R. solanacearum strains. These robust trees placed phylotype IV within the phylotype I clade, which may suggest that phylogenies based solely on egl may be misleading. As a result of phylogenetic analyses in this study, we determined that U.S. strains from Georgia, North Carolina, South Carolina, and older Florida strains isolated from solanaceous crops all belong to phylotype II sequevar 7. However, many strains recently isolated in Florida from tomato and other crops were more diverse than the southeastern United States population. These unique Florida strains grouped with strains mostly originating from the Caribbean and Central America. One of the exotic strains, which in a previous study was determined to be established in northern Florida, was characterized more extensively. Upon using Musa-specific multiplex polymerase chain reaction, this strain produced a unique banding pattern, which has not previously been reported. Inoculation of this strain into Musa spp. did not result in wilt symptoms; however, the plants were stunted and root masses were significantly reduced. Furthermore, following root inoculation, the bacterium, unlike a typical Florida race 1 biovar 1 strain, was recovered from the roots and stems, indicating systemic movement. This is the first report of an R. solanacearum strain isolated in the United States that is deleterious to the growth of Musa plants.


Asunto(s)
Ralstonia solanacearum/aislamiento & purificación , Filogenia , Reacción en Cadena de la Polimerasa , Ralstonia solanacearum/genética , Sudeste de Estados Unidos
20.
J Parasitol ; 98(5): 930-7, 2012 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-22509906

RESUMEN

Parasitic lice have been valuable informants of their host's evolutionary history because they complete their entire life cycle on the host and move between hosts primarily through direct host-to-host contact. Therefore, lice are confined to their hosts both in ecological and evolutionary time. Lice on great apes have been studied to examine details of their host's evolutionary history; however, species of Pedicinus, which parasitize the Old World monkeys, are less well known. We sampled lice from 2 groups of red colobus (Procolobus spp.) in Kibale National Park in Uganda and from red colobus and black and white colobus (Procolobus polycomos) in Taï National Park in Côte d'Ivoire. We used next-generation sequencing data analysis and the human body louse (Pediculus humanus humanus) genome to search for microsatellites for population genetic studies of Pedicinus lice. The 96 primer sets for microsatellite loci designed from the human body louse genome failed to amplify microsatellites in Pedicinus sp., perhaps due to the fast rate of evolution in parasitic lice. Of 63 microsatellites identified by next-generation sequencing data analysis of Pedicinus sp., 12 were variable among populations and 9 were variable within a single population. Our results suggest that these loci will be useful across the genus Pedicinus. We found that the lice in Uganda are not structured according to their hosts' social group; rather, 2 non-interbreeding populations of lice were found on both groups of red colobus. Because direct host-to-host contact is usually required for lice to move among hosts, these lice could be useful for identification and study of behavioral interactions between primate species.


Asunto(s)
Anoplura/genética , Colobus/parasitología , Infestaciones por Piojos/veterinaria , Repeticiones de Microsatélite/genética , Enfermedades de los Monos/parasitología , Alelos , Animales , Anoplura/clasificación , Côte d'Ivoire , ADN/química , ADN/aislamiento & purificación , Complejo IV de Transporte de Electrones/genética , Genética de Población , Genoma de los Insectos , Heterocigoto , Humanos , Infestaciones por Piojos/parasitología , Funciones de Verosimilitud , Desequilibrio de Ligamiento , Mitocondrias/enzimología , Filogenia , Análisis de Secuencia de ADN , Uganda
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