An integrative morphological and molecular diagnostics for Typhlodromus pyri (Acari: Phytoseiidae)

Berry species and crop management approaches affect species diversity and abundance of predatory mites (Acari: Phytoseiidae)

Berries comprise an economically important group of crops. Knowledge about their arthropod pests and biological control agents is important in the development of more efficient integrated pest management programs. Identification of potential biocontrol agents based solely on morphological attributes may be difficult and so molecular techniques should be incorporated. Here we studied the species diversity of predatory mites in the family Phytoseiidae, and how this diversity is affected by the berry species and crop management approaches, specifically pesticide application regimes. We sampled 15 orchards in the State of Michoacán, Mexico. Sites were selected based on berry species and pesticide regimes. Mite identification was achieved by combining morphological attributes and molecular techniques. Phytoseiidae diversity was compared amongst blackberry, raspberry and blueberry. Subsequently we studied the effect of berry species and pesticide regime on the abundance of the most prevalent phytoseiid species. We identified 11 species of phytoseiid mites. The greatest species diversity was found in raspberry, followed by blackberry and then blueberry. The most abundant species were Typhlodromalus peregrinus and Neoseiulus californicus. The abundance of T. peregrinus was significantly affected by pesticide application but not by berry species. In contrast, abundance of N. californicus was significantly affected by berry species but not by pesticide regime.

Drivers for mutation in amino acid sequences of two mitochondrial proteins (Cytb and COI) in Phytoseiidae mites (Acari: Mesostigmata)

Mutations in amino acid sequences can affect protein function. Such aspects have been poorly studied for arthropods. As recent studies have shown mutations in cytochrome b (Cytb) associated with geographic locations in several Phytoseiidae species, the present study aims at investigating (i) the mutation pattern in additional species for the Cytb fragment, (ii) the mutation pattern for another mitochondrial amino acid sequence, cytochrome c oxidase subunit 1 (COI), and (iii) factors affecting the mutations observed (taxonomy, plant support, climatic variables, wild vs. commercialised species). Mutations in amino acid sequences were assessed in seven Phytoseiidae species, with populations collected in contrasted environments. The DNA sequences were mainly obtained from published studies and some were newly obtained. Mutations were observed within and between the populations considered for both fragments, with higher mutation rates in Cytb than in COI sequences, confirming the robustness of this former fragment. Plant support and taxonomic position were not related to mutation patterns. A lower number of mutations was observed in commercialised populations than in wild ones. As preliminary tendencies, mutations in Cytb and COI sequences seem associated to temperature and moisture. Such a preliminary approach, attempting to relate mutation to functional adaptations, clearly opens new research tracks for better assessment of the drivers of mite adaptation, in a context of climate change.

Molecular variation of the cytochrome b DNA and protein sequences in Phytoseiulus macropilis and P. persimilis (Acari: Phytoseiidae) reflect population differentiation

Several phytoseiid mite species are important natural enemies used in biological control strategies. In the present study, Cytb mtDNA sequences of various populations of two species, Phytoseiulus macropolis and P. persimilis, were compared to determine whether the specimens collected in Brazil could belong to P. persimilis as this latter species is reported in South America but not in Brazil. The Cytb marker was used because of its high evolution rate, assumed to capture intraspecific variation. No overlap between intra- and interspecific distances was observed but the distances were quite low for interspecific variation. This can be due to the particular biology of Phytoseiulus species and this shows the difficulty to apply a universal threshold in genetic distances to conclude about the existence of one or several species. Cytb mtDNA sequences were also considered to assess intraspecific variation. The DNA sequences of P. persimilis populations were very similar, probably because they all originated from the West Palearctic region or because of a prevalence of commercialized specimens in natura. For P. macropilis, higher genetic distances were observed and differentiation was noted according to geographic location and, to a smaller extent, pyrethroid resistance. To determine how DNA variation might impact the protein function (CytB fragment considered), the amino acid compositions of the populations studied were compared. No diagnostic mutation was observed between pyrethroid resistant and susceptible populations, whereas four mutations were identified between populations of P. macropilis separated by 1300 km (different climatic conditions). The impact of such mutations is discussed but knowledge is scarce, which makes it difficult to root testable hypotheses. The protein analysis clearly opens new perspectives in Phytoseiidae studies.

Markers of life history traits: variation in morphology, molecular and amino acid sequences within Typhlodromus (Anthoseius) recki Wainstein (Acari: Mesostigmata: Phytoseiidae)

In this study we investigated morphological and molecular variation within the predatory mite Typhlodromus (Anthoseius) recki, and their relationships to ecological features. In total, 42 morphological characters were measured on 87 specimens from seven populations in the south of France and Sicily living on plants of four families. DNA sequences (two mitochondrial markers) and the amino acid sequences of the CytB protein were assessed. A relationship between morphological variation and plant families was observed. The 12S rRNA gene showed differentiation that appeared to be related to feeding habit, in agreement with the findings for two other Phytoseiidae species. CytB mitochondrial DNA showed variation related to geographical location. Four amino acid mutations separated the Sicilian and the French populations. CytB amino acid sequences were analysed for three other Phytoseiidae species, and again diagnostic mutations associated with geographical location were observed, as already shown for Phytoseiulus macropilis. The population differentiation observed for each marker (morphological, DNA fragments) appeared to be related to ecological/biological features, revealing new perspectives for forecasting functional characteristics based on morphotypes and genotypes. However, additional studies are needed to confirm these observations and to explain such functional relationships.

Evidence of trans-generational developmental modifications induced by simulated heat waves in an arthropod

Heat waves are considered to pose a greater risk to arthropods with their limited thermoregulation abilities than the increase of mean temperatures. Theoretically, within- and trans-generational modifications may allow populations to keep pace with rapidly occurring heat waves. Here, we evaluated this assumption using individuals of predatory mite Amblydromalus limonicus from the F1 and F2 generation, which were exposed to summer or simulated heat wave conditions during juvenile development. Independent of generation, survival and male body size were insensitive to heat waves. Heat stress elongated juvenile development of F1 males and females, and lowered the F1 female size at maturity indicating non-adaptive within-generational effects. Trans-generational modifications speeded up the development of F2 males and females and resulted in larger body size of F2 females deriving from the heat wave-experienced F1 generation. Faster F2 development should be adaptive, because it reduces the exposure time to heat waves and promotes an early beginning of mating activities. Being large at extreme high temperatures maybe a benefit for the F2 females, because large individuals are less vulnerable to dehydration and overheating. Thus, the potential fitness loss from reduced F1 growth should be compensated by increased fitness in the F2 indicating adaptive trans-generational modifications.

Molecular and morphological characterization of the predatory mite Amblyseius largoensis (Acari: Phytoseiidae): surprising similarity between an Asian and American populations

The accurate characterization of biological control agents is a key step in control programs. Recently, Amblyseius largoensis from Thailand were introduced in Brazil to evaluate their efficiency for the control of the red palm mite, Raoiella indica. The aim of this study was to confirm their identification and to characterize the population from Thailand, comparing it to populations of the Americas and Indian Ocean islands. In addition, a population of A. largoensis from New Caledonia, Oceania, of which DNA sequences were available, was included in phylogenetic analyses. Morphometric data obtained for the population of A. largoensis from Thailand were compared to those of populations from Reunion Island and the Americas through univariate and multivariate analyses. Two DNA fragments were amplified and sequenced: the nuclear ribosomal region ITSS and the mitochondrial 12S rRNA. Haplotypes (12S rRNA) and genotypes (ITSS) were identified and phylogenetic analyses using both fragments were conducted separately and combined using maximum likelihood and the Bayesian information criterion. The integrative approach reveals morphometric and molecular variabilities among populations of A. largoensis and shows that the population identified as A. largoensis collected in Thailand, as well as that from New Caledonia, are conspecific to the populations of the Americas and Indian Ocean islands. Populations from the Americas and Asia are more related to each other than with that from the Indian Ocean islands. Hypotheses to explain this clustering are proposed. Data on the molecular intraspecific variability of this predatory mite from remote areas will be helpful for the development of molecular diagnosis.

DNA barcoding and traditional taxonomy: an integrated approach for biodiversity conservation

Biological diversity is depleting at an alarming rate. Additionally, a vast amount of biodiversity still remains undiscovered. Taxonomy has been serving the purpose of describing, naming, and classifying species for more than 250 years. DNA taxonomy and barcoding have accelerated the rate of this process, thereby providing a tool for conservation practice. DNA barcoding and traditional taxonomy have their own inherent merits and demerits. The synergistic use of both methods, in the form of integrative taxonomy, has the potential to contribute to biodiversity conservation in a pragmatic timeframe and overcome their individual drawbacks. In this review, we discuss the basics of both these methods of biological identification (traditional taxonomy and DNA barcoding), the technical advances in integrative taxonomy, and future trends. We also present a comprehensive compilation of published examples of integrative taxonomy that refer to nine topics within biodiversity conservation. Morphological and molecular species limits were observed to be congruent in ∼41% of the 58 source studies. The majority of the studies highlighted the description of cryptic diversity through the use of molecular data, whereas research areas like endemism, biological invasion, and threatened species were less discussed in the literature.

Which molecular markers for assessing which taxonomic level? The case study of the mite family Phytoseiidae (Acari: Mesostigmata)

The use of molecular markers for resolving systematics issues has improved our knowledge of life history. However, for the taxa studied herein-the predatory mite family Phytoseiidae-molecular phylogeny is impeded by a lack of suitable markers for deeper taxonomic levels. This study aims (i) to establish DNA amplification protocols for molecular markers known to resolve supraspecific nodes in other taxa, (ii) to determine their individual performance in assessing the clustering of species, genera, tribes and subfamilies, and (iii) to characterize the additional information provided when markers are concatenated. A new phylogenetic index is proposed based on ecological concepts, considering trees as a community of nodes. New and efficient protocols for DNA amplification of six molecular markers are provided. The concatenated tree globally provides more robust and reliable information, especially for deeper nodes. However, for assessing species identification and within-genera phylogenies, the combined use of six markers does not seem necessary, underlining the need to resize experiments depending on their taxonomic objectives. Finally, this study lays the methodological foundations with which to test the present Phytoseiidae classification as the first phylogeny obtained shows incongruence with the present morphological classification.

Haplotype identification and detection of mitochondrial DNA heteroplasmy in Varroa destructor mites using ARMS and PCR-RFLP methods

In the present study, amplification refractory mutation system (ARMS) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods were used for identification of recently described Serbia 1 (S1) and Peshter 1 (P1) mitochondrial haplotypes of Varroa destructor. Based on single nucleotide polymorphisms (SNPs) within cytochrome oxidase 1 (cox1) and cytochrome b (cytb) gene sequences, a total of 64 adult V. destructor females were analyzed from locations where the S1 and P1 haplotypes had been detected previously. Results of haplotype identification obtained by ARMS and PCR-RFLP methods were completely consistent with the sequencing data. Furthermore, in some analyzed samples the occurrence of site heteroplasmy at haplotype-defining sites was detected, as it was confirmed by double peaks in the sequence chromatograms. Neither mites with simultaneous nucleotide variability, nor those with combined SNP and heteroplasmy in cox1 and cytb were found. Given that this is the first occurrence of site heteroplasmy in V. destructor, the origin of this phenomenon and possible specific traits of heteroplasmic mites have yet to be determined.

The predatory mite Neoseiulus paspalivorus (Phytoseiidae) in Brazil: taxonomic status, reproductive compatibility and morphological and molecular variability

The predatory mite Neoseiulus paspalivorus (De Leon) is often found in association with the coconut mite, Aceria guerreronis Keifer. The identification of natural enemies is essential for the definition of biological control strategies. Therefore, the present study aimed to confirm whether the mite populations from different Northeastern Brazilian states identified as N. paspalivorus belong to the same species. This determination was accomplished through the study of morphometric variability in 33 anatomical characters and of molecular variability in two DNA fragments: Internal Transcribed Spacer (ITS) rDNA and cytochrome c oxidase subunit I (COI) mtDNA. This study also determined whether there is reproductive isolation between the two most morphologically distinct populations (Rio Grande do Norte and Paraíba). Intraspecific morphometric variability was observed among the five populations of N. paspalivorus. Despite this variability, the crosses and backcrosses of the most morphologically distinct populations did not show reproductive incompatibility. The molecular analysis indicated the absence of genetic differences among the N. paspalivorus populations for the ITS fragment. Three haplotypes were identified for the COI fragment, and the genetic distance ranged from 0 to 0.2 %. Despite the morphometric differences, the results of the molecular and biological analysis corroborate the previous identification of N. paspalivorus for all of the studied populations. The present study contributes to the systematics of Phytoseiidae predatory mites and to the biological control of A. guerreronis by the accurate identification and characterization of one of its main natural enemies along extensive areas in Brazil.

Is Neoseiulus wearnei the Neoseiulus californicus of Australia?

Species of the family Phytoseiidae are known as predatory mites, some of them being used in crops to control mite pests, all around the world. Neoseiulus (=Cydnodromus) californicus is among the most commonly used Phytoseiidae species in biological control programs, especially in vineyards, orchards and vegetable fields. This species is distributed world-wide but has never been reported from Australia. On the other hand, specimens morphologically close to N. californicus have been assigned to a species called Neoseiulus wearnei, only reported from Australia. Investigations based on morphological and molecular comparisons were carried out to investigate whether these two taxa are conspecific. Morphological analyses showed no significant difference between specimens identified as N. wearnei and N. californicus. Similarly, genetic distances between these taxa were null, showing that all these specimens belong to the same species. Although it is not yet possible to conclude that all the specimens identified as N. wearnei are N. californicus, we can conclude that N. californicus is present in Australia. The information about the biology of N. californicus can thus now be applied to the Australian population of this species for biological control purposes.

Obtaining molecular data for all life stages of Typhlodromus (Typhlodromus) exhilaratus (Mesostigmata: Phytoseiidae): consequences for species identification

Several species of the family Phytoseiidae are known to control mite pests in many crops worldwide. However, biological control success greatly depends on the accurate identification of these predatory mites. Species diagnostics is essentially based on the morphological characters of females. Thus, when only immature stages and/or males are collected, their identification is poorly supported. Molecular tools could be of great help to overcome these difficulties, as molecular sequences are assumed to be identical for the life stage considered. However, one of the essential points is to extract a sufficient DNA amount from a single specimen of immature stages (eggs, protonymphs, deutonymphs) and males (less than 300 μm in length) to amplify and sequence DNA. The markers used were two mitochondrial DNA fragments (12S rRNA and Cytb mtDNA) and the species studied were Typhlodromus (Typhlodromus) exhilaratus and T. (T.) phialatus, two cryptic species, reported to control mite pests in crops of southern Europe and commonly found on the same plants. Despite a low quantity of DNA extracted, particularly for the egg, larva and protonymph stages, DNA was amplified and sequences were obtained from all the life stages considered with the two mtDNA fragments. Sequences from all the developmental stages of T. (T.) exhilaratus were identical and well differentiated from those of its sister-species. However, contaminations were observed especially for eggs and DNA amplified with the Cytb mt marker. Utility of the present results are discussed and protocol improvements are proposed.