Denise Navia

The invasive coconut mite Aceria guerreronis (Acari: Eriophyidae): origin and invasion sources inferred from mitochondrial (16S) and nuclear (ITS) sequences.

Over the past 30 years the coconut mite Aceria guerreronis Keifer has emerged as one of the most important pests of coconut and has recently spread to most coconut production areas worldwide. The mite has not been recorded in the Indo-Pacific region, the area of origin of coconut, suggesting that it has infested coconut only recently. To investigate the geographical origin, ancestral host associations, and colonization history of the mite, DNA sequence data from two mitochondrial and one nuclear region were obtained from samples of 29 populations from the Americas, Africa and the Indo-ocean region. Mitochondrial DNA 16S ribosomal sequences were most diverse in Brazil, which contained six of a total of seven haplotypes. A single haplotype was shared by non-American mites. Patterns of nuclear ribosomal internal transcribed spacer (ITS) variation were similar, again with the highest nucleotide diversity found in Brazil. These results suggest an American origin of the mite and lend evidence to a previous hypothesis that the original host of the mite is a non-coconut palm. In contrast to the diversity in the Americas, all samples from Africa and Asia were identical or very similar, consistent with the hypothesis that the mite invaded these regions recently from a common source. Although the invasion routes of this mite are still only partially reconstructed, the study rules out coconut as the ancestral host of A. guerreronis, thus prompting a reassessment of efforts using quarantine and biological control to check the spread of the pest.

Genetic diversity of Bemisia tabaci (Genn.) Populations in Brazil revealed by RAPD markers

Bemisia tabaci (Genn.) was considered a secondary pest in Brazil until 1990, despite being an efficient geminivirus vector in beans and soybean. In 1991, a new biotype, known as B. tabaci B biotype (=B. argentifolii) was detected attacking weed plants and causing phytotoxic problems in Cucurbitaceae. Nowadays, B. tabaci is considered one of the most damaging whitefly pests in agricultural systems worldwide that transmits more than 60 different plant viruses. Little is known about the genetic variability of these populations in Brazil. Knowledge of the genetic variation within whitefly populations is necessary for their efficient control and management. The objectives of the present study were to use RAPD markers (1) to estimate the genetic diversity of B. tabaci populations, (2) to study the genetic relationships among B. tabaci biotypes and two other whitefly species and (3) to discriminate between B. tabaci biotypes. A sample of 109 B. tabaci female individuals obtained from 12 populations in Brazil were analyzed and compared to the A biotype from Arizona (USA) and B biotype from California (USA) and Paraguay. Trialeurodes vaporariorum and Aleurodicus cocois samples were also included. A total of 72 markers were generated by five RAPD primers and used in the analysis. All primers produced RAPD patterns that clearly distinguished the Bemisia biotypes and the two other whitefly species. Results also showed that populations of the B biotype have considerable genetic variability. An average Jaccard similarity of 0.73 was observed among the B biotype individuals analyzed. Cluster analysis demonstrated that, in general, Brazilian biotype B individuals are scattered independently in the localities where samples were collected. Nevertheless, some clusters were evident, joining individuals according to the host plants. AMOVA showed that most of the total genetic variation is found within populations (56.70%), but a significant portion of the variation is found between crops (22.73%). The present study showed that the B biotype is disseminated throughout the sampled areas, infesting several host plants and predominates over the A biotype.

Survey of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) biotypes in Brazil using RAPD markers

Em 1991, um novo biotipo de Bemisia tabaci denominado de raca B, mosca branca da poinsetia ou mosca da folha prateada foi detectado no Brasil. Esta praga trouxe muitos prejuizos e danos a agricultura nacional, por ser mais agressiva do que a existente anteriormente, conhecida como B. tabaci ou B. tabaci biotipo BR (nao B). A relacao taxonomica entre B. tabaci e B. tabaci biotipo B nao e clara e nao existem evidencias morfologicas consistentes que possam distinguir esses dois biotipos. RAPD-PCR tem sido utilizada para identificacao de biotipos presentes nas populacoes, utilizando-se, como padroes de referencia, adultos de Bemisia tabaci das racas A e B provenientes dos Estados Unidos. As coletas de mosca branca foram feitas em 27 culturas e plantas daninhas em 57 localidades do pais. As populacoes foram entao analisadas, observando-se que a populacao predominante em 20 estados brasileiros e de B. tabaci biotipo B. Os biotipos BR e B foram encontrados coabitando a mesma regiao, em tres diferentes localidades: Jaboticabal, SP; Rondonopolis e Cuiaba, MT e Goiânia, GO.

Behavioural studies on eriophyoid mites: an overview

Eriophyoid mites are excellent candidates for ethological research using the approaches of behavioural ecology and sociobiology. These tiny haplodiploid mites are highly specialized plant parasites, producing galls, forming nests, inhabiting refuges or living freely on plants. They reproduce via spermatophores deposited on a substrate and without pairing, which is a fascinating, though still poorly understood, mode of reproduction widespread in some groups of arthropods. Eriophyoid males can be involved in external sperm competition. In some species they also guard pre-emergent females and deposit spermatophores beside them. Although slow-walking, the minute eriophyoid mites can disperse for long distances on air currents or specific animal carriers. After landing on a plant they can distinguish between suitable and unsuitable hosts. Biological observations on a deuterogynous species indicate that parasociality could occur among eriophyoid mites. Many eriophyoids are of economic importance. Knowledge of their behaviour may promote understanding their ecology, may resolve problems in their phylogeny and may help developing methods for their control. In this paper, attention is directed to dispersal modes of eriophyoid mites, their feeding and host acceptance, spermatophore deposition and mating, defence against predators, and social behaviour.

A critical review on some closely related species of Tetranychus sensu stricto (Acari: Tetranychidae) in the public DNA sequences databases

Taxonomic misidentification of the specimens used to obtain DNA sequences is a growing problem reported for different groups of organisms, which threatens the utility of the deposited sequences in public DNA databases. This paper provides new evidence of misidentifications in molecular DNA public databases in phytophagous mites of the Tetranychidae family belonging to the group Tetranychus (Tetranychus). Several species in this group are of economic and quarantine importance in agriculture and among them Tetranychus urticae, a highly polyphagous mite causing outbreaks in many crops worldwide, is certainly the most studied. We analyzed and evaluated the identity of 105 GenBank accessions of ITS2 rDNA and 138 COI mtDNA sequences which were deposited as T. urticae and those of 14 other taxa morphologically closely related to Tetranychus sensu stricto. In addition, ITS2 and COI sequences of 18 T. urticae samples collected for this study and identified by morphological criteria, were generated and included in the analyzed dataset. Among the deposited sequences in the GenBank database, numerous cases of apparently mistaken identities were identified in the group Tetranychus s. str., especially between T. urticae, T. cinnabarinus, T. kanzawai and T. truncatus. Unreliable sequences (misidentified or dubious) were estimated at nearly 30%. In particular the analysis supports the invalidity of the controversial species status of T. cinnabarinus. More generally, it highlights the need of using combined morphological and molecular approaches to guarantee solid species diagnostics for reliable sequence accessions in public databases.

Wheat curl mite, Aceria tosichella, and transmitted viruses: an expanding pest complex affecting cereal crops

The wheat curl mite (WCM), Aceria tosichella, and the plant viruses it transmits represent an invasive mite-virus complex that has affected cereal crops worldwide. The main damage caused by WCM comes from its ability to transmit and spread multiple damaging viruses to cereal crops, with Wheat streak mosaic virus (WSMV) and Wheat mosaic virus (WMoV) being the most important. Although WCM and transmitted viruses have been of concern to cereal growers and researchers for at least six decades, they continue to represent a challenge. In older affected areas, for example in North America, this mite-virus complex still has significant economic impact. In Australia and South America, where this problem has only emerged in the last decade, it represents a new threat to winter cereal production. The difficulties encountered in making progress towards managing WCM and its transmitted viruses stem from the complexity of the pathosystem. The most effective methods for minimizing losses from WCM transmitted viruses in cereal crops have previously focused on cultural and plant resistance methods. This paper brings together information on biological and ecological aspects of WCM, including its taxonomic status, occurrence, host plant range, damage symptoms and economic impact. Information about the main viruses transmitted by WCM is also included and the epidemiological relationships involved in this vectored complex of viruses are also addressed. Management strategies that have been directed at this mite-virus complex are presented, including plant resistance, its history, difficulties and advances. Current research perspectives to address this invasive mite-virus complex and minimize cereal crop losses worldwide are also discussed.

Cryptic species within the wheat curl mite Aceria tosichella (Keifer) (Acari : Eriophyoidea), revealed by mitochondrial, nuclear and morphometric data

Abstract. The wheat curl mite (WCM), Aceria tosichella (Keifer, 1969), is one of the primary pests of wheat and other cereals throughout the world. Traditional taxonomy recognises WCM as a single eriophyoid species; however, a recent study suggested that two genetic lineages of WCM in Australia might represent putative species. Here, we investigate WCM populations from different host plants in Australia, South America and Europe and test the hypothesis that WCM is, in fact, a complex of cryptic species. We used morphological data in combination with nucleotide sequences of the mitochondrial cytochrome c oxidase subunit I (COI) and nuclear D2 region of 28S rDNA and internal transcribed spacer region (ITS1, ITS2) sequences. The molecular analyses did not support the monophyly of A. tosichella because the outgroup A. tulipae (Keifer, 1938) is grouped within WCM. The molecular datasets indicated the existence of distinct lineages within WCM, with the distances between lineages corresponding to interspecific divergence. Morphological analyses failed to clearly separate WCM populations and lineages, but completely separated A. tulipae from A. tosichella. The results suggest that what has been recognised historically as a single species is, in fact, a complex of several genetically isolated evolutionary lineages that demonstrate potential as cryptic species. Hence, their discrimination using solely morphological criteria may be misleading. These findings are particularly significant because of the economic importance of WCM as a direct pest and vector of plant viruses.

First report of the red palm mite, Raoiella indica Hirst (Acari: Tenuipalpidae), in Brazil

The presence of the red palm mite, Raoiella indica Hirst, is reported for the first time in Brazil. This invasive mite was found in July 2009 infesting coconut palms and bananas in urban areas of Boa Vista, State of Roraima, in northern Brazil. Comments on the possible pathways of R. indica into the country, present and potential impact of its introduction and mitigating measures to prevent or to delay the mite spread in Brazil are presented.

DNA-based methods for eriophyoid mite studies: review, critical aspects, prospects and challenges.

Besides their potential for species identification, DNA-based methods are also routinely used for addressing ecological, evolutionary, phylogenetic and genetic questions to study several groups of Acari. However, in contrast to other plant-feeding mites and despite the economical relevance of many species of Eriophyoidea, very few scientists have dared so far to use DNA methods for the study of this group of mites; their very small size certainly has influenced this. In this review we examine the main techniques that have been used to study eriophyoid mites and discuss the results from the literature where DNA methods have provided significant advances to address several essential questions of the eriophyoid biology, e.g., to clarify suspect synonymies, to test hypothesis of cryptic species, to examine the occurrence of biotypes, especially in relation to virus ability or host-plant associations, to understand colonization patterns of invasive species, and for uses as biological control agents against invasive plants. We discuss these questions which might be related to agricultural issues, together with more fundamental aspects as the revision of the phylogeny of the Eriophyoidea. We discuss on the advantages as well as limitations of the most commonly used genetic markers and emphasize prospects and challenges of new molecular approaches. Much is now expected from molecular techniques in many fields of biology and for virtually all taxa. Eriophyoids should not be the exception.

First Report of Raoiella Indica (Acari: Tenuipalpidae) in Colombia

Raoiella indica Hirst (Acari: Tenuipalpidae), the red palm mite, is a phytophagous mite that recently invaded the Western Hemisphere. This mite was first detected in Martinique (Flechtmann & Etienne 2004) and it rapidly spread to multiple islands of the Caribbean [St. Lucia and Dominica (Kane et al. 2005), Guadeloupe and Saint Martin (Etienne & Flechtmann 2006), Puerto Rico and Culebra Island (Rodrigues et al. 2007), and Cuba (de la Torre et al. 2010) among other islands]. In 2007, the mite was found in West Palm Beach, Florida (FDACS 2007), and in the state of Sucre, Venezuela (Vasquez et al. 2008), and more recently, reported in the northern state of Roraima in Brazil (Marsaro Jr. et al. 2009), and Isla Mujeres and Cancun, Mexico (NAPPO 2009). In January 2010, high populations of R. indica were found attacking coconut (Cocos nucifera L.), banana (Musa acuminata Colla) and heliconia (Heliconia sp.) plants in the Tayrona National Park located in the Colombian Caribbean littoral, near the city of Santa Marta, Magdalena. The presence of multigenerational colonies and exuvia was confirmed in 18 coconut palms, 4 heliconias and multiple banana plants located near the coast in the northern part of the park (11°18’44”N 73°56’04”W). In further surveys R. indica infestations were detected in commercial coconut and banana groves in June 2010 at Los Naranjos, Magdalena (11°17’49”N -73°53’49”W), approximately 6 km East of the Tayrona Park along the coast. In this locality the predatory mite Amblyseius largoensis Muma (Acari: Phytoseiidae) was found showing a conspicuous red coloration of the alimentary tract indicating recent feeding on R. indica. Previous studies indicated that populations of A. largoensis increased in numbers after the arrival of R. indica to Florida and some areas in the Neotropics (Pena et al. 2009; Carrillo et al. 2010). Raoiella indica and A. largoensis specimens were collected (70% ethanol) and subsequently slide mounted, identified, and deposited in the collections of the Laboratory of Plant Quarantine reference collection, Embrapa Genetic Resources and Biotechnology, Brasilia, Brazil, and the Laboratory of Acarology from the Instituto Agroforestal Mediterraneo, Universidad Politecnica of Valencia, Spain. The experienced negative effects of R. indica on coconut production in the Caribbean, where yield reduction has been estimated in over 50% at some locations (CARDI 2010), indicate the importance of adopting regulatory and other control measures in areas of recent invasion. The establishment of chemical practices needed to allow movement of host plant material, and continuous surveying (pre and post-invasion) using sentinel sites, have been adopted to prevent R. indica’s rapid dissemination in Florida (Roda et al. 2008). An integrated approach combining all available control tactics should be adopted and natural enemies identified for managing this species (Pena et al. 2009; Carrillo et al. 2010). In addition, studies are needed to determine the potential host plant range of R. indica in Colombia and the rest of the Neotropical region. Strict sanitary measures and other management tactics should be implemented to minimize the damage caused by R. indica in Colombia and other countries in South and Central America.