Measuring local genetic variation in permethrin-resistant head lice (Phthiraptera: Pediculidae) from Buenos Aires, Argentina.

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.

Prevalence and Genetic Diversity of a Microsporidian Parasite in the Black Imported Fire Ant and Its Social Parasitic Ant (Formicidae: Myrmicinae: Solenopsis) in Buenos Aires Province, Argentina.

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.

Nuclear genetic diversity of head lice sheds light on human dispersal around the world.

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.

Are Ants Good Organisms to Teach Elementary Students about Invasive Species in Florida?

This study aims to evaluate the effectiveness of our outreach program "The ImportANTs of ANTs" in communicating scientific topics to elementary school children, using ants as example organisms. In this program's first phase, we focused on the concepts of native and invasive species and how invasive species affect ecosystems. The program included various active learning approaches, including presentations, handouts, crafts, and live colony viewings. At two schools (one in rural and one in suburban areas), 210 students from 5th grade were assessed using short, anonymous pre- and post-surveys. We analyzed the students' responses to questions from the following categories: general feelings about ants, ant knowledge, general care for the environment, general impact knowledge, and native/invasive species knowledge. The school populations displayed distinct opinion changes and knowledge gains; however, there was a significant increase in knowledge of native and invasive species in both populations. Our study demonstrates that ants are good models to teach children about the impact of invasive species. The project aims to drive universal responsibility by forging proactive attitudes toward protecting the environment and native species early.

A new species of planthopper in the genus Anotia Kirby (Hemiptera: Auchenorrhyncha: Derbidae) from coconut palm in Costa Rica.

An ongoing survey for planthoppers associated with palms in the Caribbean basin is being conducted with current efforts on the Caribbean lowlands of Costa Rica. In an expedition in June of 2019, a derbid was found on coconut palms in Alajuela province and was determined to be a new species belonging to the genus Anotia. The novel taxon is described and named Anotia firebugia Bahder Bartlett sp. n. Additionally, molecular barcode data (COI) is provided for the newly described taxon.

Conceptualization of the Holobiont Paradigm as It Pertains to Corals.

Corals' obligate association with unicellular dinoflagellates, family Symbiodiniaceae form the foundation of coral reefs. For nearly a century, researchers have delved into understanding the coral-algal mutualism from multiple levels of resolution and perspectives, and the questions and scope have evolved with each iteration of new techniques. Advances in genetic technologies not only aided in distinguishing between the multitude of Symbiodiniaceae but also illuminated the existence and diversity of other organisms constituting the coral microbiome. The coral therefore is a meta-organism, often referred to as the coral holobiont. In this review, we address the importance of including a holistic perspective to understanding the coral holobiont. We also discuss the ramifications of how different genotypic combinations of the coral consortium affect the holobiont entity. We highlight the paucity of data on most of the coral microbiome. Using Symbiodiniaceae data, we present evidence that the holobiont properties are not necessarily the sum of its parts. We then discuss the consequences of the holobiont attributes to the fitness of the holobiont and the myriad of organisms that contribute to it. Considering the complexity of host-symbiont genotypic combinations will aid in our understanding of coral resilience, robustness, acclimation, and/or adaptation in the face of environmental change and increasing perturbations.

Large-spored Drechslera gigantea is a Bipolaris species causing disease on the invasive grass Microstegium vimineum.

Environmentally damaging invasive plants can also serve as reservoir hosts for agricultural pathogens. Microstegium vimineum is an invasive C4 annual grass that is present throughout the midwestern and eastern United States. It can reach high densities in disturbed areas such as crop-forest interfaces, which creates the potential for pathogen spillover from M. vimineum to agricultural crops and native plants. A previous study that surveyed disease on M. vimineum found a large-spored Bipolaris species that was widespread on M. vimineum and also isolated from co-occurring native grasses. Here, we report that the large-spored fungus isolated from M. vimineum and the native grass Elymus virginicus is Drechslera gigantea, based on comparison with published descriptions of morphological traits, and establish that D. gigantea is a pathogen of M. vimineum and E. virginicus. We review the phylogenetic placement and taxonomic history of D. gigantea and propose that it be reassigned to the genus Bipolaris as Bipolaris gigantea.

Revised status of Omolicna subgenus Agoo (Hemiptera: Auchenorrhyncha: Fulgoroidea: Derbidae) with a new species from Costa Rica and new country records.

An ongoing survey for novel phytoplasmas and viruses that affect palms (Arecaceae) and their potential vectors is being conducted in Costa Rica. During that survey, a new species of derbid planthopper (Hemiptera: Fulgoroidea) from the palm Astrocaryum alatum H.F. Loomis was found in Heredia State and is here described as Agoo dahliana sp. n. Omolicna dubia Caldwell and O. latens Fennah were also found on coconut palms (Cocos nucifera L.) and represent new country records. Sequence data for the cytochrome c oxidase subunit I (COI) were generated for 9 ingroup (Omolicna Fennah) and 1 outgroup (Neocenchrea Metcalf) taxa; and for 18S ribosomal RNA gene were generated for 8 ingroup plus 2 outgroup taxa (Neocenchrea, Cenchrea Westwood). These data were compiled with available data from GenBank and BOLD for maximum likelihood phylogenetic reconstruction for Omolicna. These results, plus morphological evidence, support changing the status of the genus-group name Agoo Bahder Bartlett from subgenus within Omolicna to full genus, resulting in the new combination of Agoo xavieri Bahder Bartlett. Based on the original description and illustration of the genitalia of Omolicna rubrimarginata Fennah (from Trinidad), we transfer this species to Agoo, creating the combination Agoo rubrimarginata (Fennah), and bringing the total number of species in this genus to three, with A. dahliana sp. n. and A. xavieri currently only known from Costa Rica. Based on both molecular and morphological evidence, O dubia is transferred to Anchimothon Fennah. A key to differentiate the species of Agoo is presented.

A new species of Omolicna (Hemiptera: Auchenorrhyncha: Fulgoroidea: Derbidae) from coconut palm in Costa Rica and new country records for Omolicna brunnea and Omolicna triata.

An ongoing survey for novel phytoplasmas and viruses that affect palms (Arecaceae) is being conducted in Costa Rica along with potential vectors. During that survey, a new species of derbid planthopper (Hemiptera: Fulgoroidea) in the genus Omolicna Fennah was detected from Heredia and Limón State and is here described as Omolicna xavieri sp. n. This new taxon was first found on declining coconut palms (Cocos nucifera) and subsequently on healthy coconut palms in Tortuguero National Park. Also, two additional species of Omolicna, O. brunnea and O. triata, were collected on coconut in the same habitat and represent new country records. There are no previously published records of Omolicna from Costa Rica. Sequence data for the cytochrome c oxidase subunit I (COI) and the 18S ribosomal RNA gene were obtained. In addition, novel 18S primers specific to auchenorrhynchan insects were developed and presented. The molecular data show high pairwise distances between O. xavieri sp. n. and other Omolicna species (24% to 31% and 10% using COI and 18S, respectively). Based on both morphological and sequence data, we erect and briefly describe the new subgenus Agoo for the new species to reflect the observed differences. A checklist of Omolicna species is presented.

A Survey of Declining Palms (Arecaceae) With 16SrIV-D Phytoplasma to Evaluate the Distribution and Host Range in Florida.

The 16SrIV-D phytoplasma was first identified in Florida in 2006. Since its discovery, it has spread throughout most of the state. It is most prevalent in the central part of Florida, from Hillsborough County on the west coast to St. Lucie County on the east coast. The 16SrIV-D phytoplasma is the causal agent of lethal bronzing disease (LBD), which is also known as Texas Phoenix palm decline (TPPD). It affects a variety of common and economically important ornamental palm species as well as the native and ecologically important species, Sabal palmetto. It has spread into the southern portions of Florida, where the palm species diversity is higher. The aims of this survey were to document the spread of disease in terms of geographic and host range one decade after its introduction into Florida, and to assess the risk that LBD poses to the nursery and landscaping industries. The survey included samples received from stakeholders throughout the state, covering 18 counties, as well as a systematic sampling of palms at the Fort Lauderdale Research and Education Center (FLREC), where the disease is spreading actively. The findings of this survey resulted in the detection of LBD in eight new counties, including Collier, Hernando, Jefferson, Martin, Miami-Dade, Monroe, Seminole, and St. Johns, and the expansion of LBD into four new host species, Cocos nucifera, Livistona chinensis, Butia capitata, and Carpentaria acuminata. These findings are crucial for stakeholders because they highlight new hosts of 16SrIV-D phytoplasma and the geographic expansion of the disease, indicating that vigilance is needed when surveying declining palms.

Feather mites play a role in cleaning host feathers: New insights from DNA metabarcoding and microscopy.

Parasites and other symbionts are crucial components of ecosystems, regulating host populations and supporting food webs. However, most symbiont systems, especially those involving commensals and mutualists, are relatively poorly understood. In this study, we have investigated the nature of the symbiotic relationship between birds and their most abundant and diverse ectosymbionts: the vane-dwelling feather mites. For this purpose, we studied the diet of feather mites using two complementary methods. First, we used light microscopy to examine the gut contents of 1,300 individual feather mites representing 100 mite genera (18 families) from 190 bird species belonging to 72 families and 19 orders. Second, we used high-throughput sequencing (HTS) and DNA metabarcoding to determine gut contents from 1,833 individual mites of 18 species inhabiting 18 bird species. Results showed fungi and potentially bacteria as the main food resources for feather mites (apart from potential bird uropygial gland oil). Diatoms and plant matter appeared as rare food resources for feather mites. Importantly, we did not find any evidence of feather mites feeding upon bird resources (e.g., blood, skin) other than potentially uropygial gland oil. In addition, we found a high prevalence of both keratinophilic and pathogenic fungal taxa in the feather mite species examined. Altogether, our results shed light on the long-standing question of the nature of the relationship between birds and their vane-dwelling feather mites, supporting previous evidence for a commensalistic-mutualistic role of feather mites, which are revealed as likely fungivore-microbivore-detritivore symbionts of bird feathers.

Penicillin Trunk Injection Affects Bacterial Community Structure in Citrus Trees.

Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CLas), an uncultured α-proteobacterium, is the most destructive disease of citrus trees worldwide. In previous studies, trunk injections of penicillin reduced CLas titers and HLB symptoms in citrus. However, antibiotic effects on the whole plant microbial community, which include effects on taxa that interact with CLas, have not yet been addressed. In this study, we investigated the effects of penicillin injection (0, 1000, and 6000 mg L-1) on rhizospheric and endophytic bacterial communities of grapefruit trees in field and greenhouse experiments through culture-independent high-throughput sequencing. DNA extractions from petioles and roots were subjected to 16S rRNA high-throughput sequencing, and reads were clustered by sequence similarity into operational taxonomic units (OTUs). Principal coordinates analysis based on weighted-UniFrac distances did not reveal differences in bacterial communities among treatments in any of the sample sources. However, pairwise linear discriminant analysis indicated significant differences in relative abundance of some taxa (including CLas) among treatments. Network analysis showed that penicillin produced major changes in root bacterial community structure by affecting interspecific microbial associations. This study provides new knowledge of the effect of antimicrobial treatments on interspecific relationships in citrus microbial communities.

A new genus and species of cixiid planthopper (Hemiptera: Auchenorrhyncha: Fulgoroidea) from the Reserva Privada el Silencio de Los Angeles Cloud Forest in Costa Rica.

Myxia belinda gen. et sp. nov. is established for a new taxon of Cixiidae in the tribe Oecleini collected from palms in Costa Rica. The new taxon was discovered while surveying palms for potential phytoplasma vectors. Placement in a new genus is supported by a 1,383 bp sequence of 18S that differs by 2.77% from Haplaxius, 5.20% from Myndus taffini, and 2.80% from Nymphomyndus caribbea. Intrageneric variation for 18S was found to be approximately 0.5% to 0.6% within Haplaxius. Generic level differences within the Oecleini for COI ranged from 15% to 17% with the novel taxon differing by about 16% from other genera. The new genus is most similar in appearance to Haplaxius but possesses striking sexual dimorphism, and the aedeagus is only partially surrounded by the phallobase (versus entirely enveloped in Haplaxius). The discovery of a novel taxon of cixiid on palms that is similar to Haplaxius is important because of the role that Haplaxius crudus plays in phytoplasma transmission in palm agro- and natural ecosystems.

Phylogenomic analysis supports multiple instances of polyphyly in the oomycete peronosporalean lineage.

The study of biological diversification of oomycetes has been a difficult task for more than a century. Pioneer researchers used morphological characters to describe this heterogeneous group, and physiological and genetic tools expanded knowledge of these microorganisms. However, research on oomycete diversification is limited by conflicting phylogenies. Using whole genomic data from 17 oomycete taxa, we obtained a dataset of 277 core orthologous genes shared among these genomes. Analyses of this dataset resulted in highly congruent and strongly supported estimates of oomycete phylogeny when we used concatenated maximum likelihood and coalescent-based methods; the one important exception was the position of Albugo. Our results supported the position of Phytopythium vexans (formerly in Pythium clade K) as a sister clade to the Phytophthora-Hyaloperonospora clade. The remaining clades comprising Pythium sensu lato formed two monophyletic groups. One group was composed of three taxa that correspond to Pythium clades A, B and C, and the other group contained taxa representing clades F, G and I, in agreement with previous Pythium phylogenies. However, the group containing Pythium clades F, G and I was placed as sister to the Phytophthora-Hyaloperonospora-Phytopythium clade, thus confirming the lack of monophyly of Pythium sensu lato. Multispecies coalescent methods revealed that the white blister rust, Albugo laibachii, could not be placed with a high degree of confidence. Our analyses show that genomic data can resolve the oomycete phylogeny and provide a phylogenetic framework to study the evolution of oomycete lifestyles.

Whole genome sequence of the emerging oomycete pathogen Pythium insidiosum strain CDC-B5653 isolated from an infected human in the USA.

Pythium insidiosum ATCC 200269 strain CDC-B5653, an isolate from necrotizing lesions on the mouth and eye of a 2-year-old boy in Memphis, Tennessee, USA, was sequenced using a combination of Illumina MiSeq (300 bp paired-end, 14 millions reads) and PacBio (10  Kb fragment library, 356,001 reads). The sequencing data were assembled using SPAdes version 3.1.0, yielding a total genome size of 45.6 Mb contained in 8992 contigs, N50 of 13 Kb, 57% G + C content, and 17,867 putative protein-coding genes. This Whole Genome Shotgun project has been deposited at DDBJ/EMBL/GenBank under the accession JRHR00000000.

Geographical distribution of pyrethroid resistance allele frequency in head lice (Phthiraptera: Pediculidae) from Argentina.

The human head louse, Pediculus humanus capitis De Geer (Phthiraptera: Pediculidae), is an obligate ectoparasite that causes pediculosis capitis and has parasitized humans since the beginning of humankind. Head louse infestations are widespread throughout the world and have been increasing since the early 1990s partially because of ineffective pediculicides. In Argentina, the overuse of products containing pyrethroids has led to the development of resistant louse populations. Pyrethroid insecticides act on the nervous system affecting voltage-sensitive sodium channels. Three point mutations at the corresponding amino acid sequence positions M815I, T917I, and L920F in the voltage-gated sodium channel gene are responsible for contributing to knockdown resistance (kdr). The management of pyrethroid resistance requires either early detection or the characterization of the mechanisms involved in head louse populations. In the current study, we estimated the distribution of kdr alleles in 154 head lice from six geographical regions of Argentina. Pyrethroid resistance kdr alleles were found in high frequencies ranging from 67 to 100%. Of these, 131 (85.1%) were homozygous resistant, 13 (8.4%) were homozygous susceptible, and 10 (6.5%) were heterozygous. Exact tests for the Hardy-Weinberg equilibrium for each location showed that genotype frequencies differed significantly from expectation in four of the six sites studied. These results show that pyrethroid resistance is well established reaching an overall frequency of 88%, thus close to fixation. With 30 yr of pyrethroid-based pediculicides use in Argentina, kdr resistance has evolved rapidly among these head louse populations.

Mitochondrial diversity in human head louse populations across the Americas.

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.

Nuclear genetic diversity in human lice (Pediculus humanus) reveals continental differences and high inbreeding among worldwide populations.

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.

Propagule pressure and colony social organization are associated with the successful invasion and rapid range expansion of fire ants in China.

We characterized patterns of genetic variation in populations of the fire ant Solenopsis invicta in China using mitochondrial DNA sequences and nuclear microsatellite loci to test predictions as to how propagule pressure and subsequent dispersal following establishment jointly shape the invasion success of this ant in this recently invaded area. Fire ants in Wuchuan (Guangdong Province) are genetically differentiated from those found in other large infested areas of China. The immediate source of ants in Wuchuan appears to be somewhere near Texas, which ranks first among the southern USA infested states in the exportation of goods to China. Most colonies from spatially distant, outlying areas in China are genetically similar to one another and appear to share a common source (Wuchuan, Guangdong Province), suggesting that long-distance jump dispersal has been a prevalent means of recent spread of fire ants in China. Furthermore, most colonies at outlier sites are of the polygyne social form (featuring multiple egg-laying queens per nest), reinforcing the important role of this social form in the successful invasion of new areas and subsequent range expansion following invasion. Several analyses consistently revealed characteristic signatures of genetic bottlenecks for S. invicta populations in China. The results of this study highlight the invasive potential of this pest ant, suggest that the magnitude of international trade may serve as a predictor of propagule pressure and indicate that rates and patterns of subsequent range expansion are partly determined by the interplay between species traits and the trade and transportation networks.

Global invasion history of the fire ant Solenopsis invicta.

The fire ant Solenopsis invicta is a significant pest that was inadvertently introduced into the southern United States almost a century ago and more recently into California and other regions of the world. An assessment of genetic variation at a diverse set of molecular markers in 2144 fire ant colonies from 75 geographic sites worldwide revealed that at least nine separate introductions of S. invicta have occurred into newly invaded areas and that the main southern U.S. population is probably the source of all but one of these introductions. The sole exception involves a putative serial invasion from the southern United States to California to Taiwan. These results illustrate in stark fashion a severe negative consequence of an increasingly massive and interconnected global trade and travel system.