Vespidae Wasps: Importance and Genetic Diversity
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Hymenopterans play an vital role in the terrestrial ecosystems as producers, predators and pollinators. Aculeata is a subgroup of the order Hymenoptera whose significant speciality is the conversion of the female ovipositor into a venom injecting device or stinger . The members of which are commonly called as ants, bees and wasps. India has a rich fauna of Aculeata (P. Gireeshkumar et al., 2014). Bingham, (1897, 1903) was the first published a consolidated account of aculeate hymenoptera (Wasps and Bees) and (Ants and Cuckoo wasps) of india, including Burma and Ceylon. Batra, (1977), Das and Gupta (1989) and Gupta and Jonathan (2003) also made comprehensive studies on Indian species of Vespidae, Apidae and Scoliidae respectively (P. Gireeshkumar et al., 2014)
The Vespidae are a diverse (nearly 5,000 species), cosmopolitan and large family of wasps, with many solitary wasps and nearly all the known eusocial wasps (such as Polistes annularis) (Kurt M Pickett and James M Carpenter, 2010). It is divided into six subfamilies, of which three comprises of social species (Polistinae, Stenogastrinae and Vespinae) and three including solitary species (Euparigiinae, Masarinae and Eumeninae), the largest family being eumeninae with roughly 3000 species around the world. Among the six subfamilies Only, vespinae, polistinae and eumeninae are found in kerala. [kishore lambert, 2002]. The social Vespidae may have colonies with a little to thousands of individuals. Their colonies consist of, males, workers and queens. Social wasps construct their nest by making use of dead wood and vegetable fibre, they chew them into pulp to build the first cell of the nest. Caste systems of the social wasps have not evolved as those of the other major groups of social insects. (Marhal 1896, 1897) postulated that physical deviation of the queen and worker castes of Vespinae is based on nutritional inequity during larval growth. Worker castes are identified due to their large size and the extended conditions of the rear part of the head. The workers catches a wide variety of soft bodied insects to take to their nest, favouring flies, bees, both larva and adult of lepidopterans and they also visits flower to collect honey and nectar. The queen wasp is large sized (35 mm) in some species. She hibernates and transforms into the foundresses (in northern India) of colony in next spring season.
Vespids can travel in a speed of about 100 km per day during their foraging activity. They are called "true wasps". The life cycle of Vespinae and Polistinae are very similar. Vespinae are very dangerous and highly poisonous to human being. (Pereira et al.,.2007a,b).
Importance of vespidae wasps
The social wasps of vespidae are rapacious generalist predators. They are vital agents for natural biocontrol in agricultural and natural ecosystems (Ross and Matthews, 1991; Miranda et al., 1998; Gonring et al., 2003 a,b,). Adult social wasps are usually seen in agro-ecosystems (Auad et al., 2010; Brugger et al., 2011) where they check the pest populations such as lepidopteran caterpillars (Raveret and Richter 2000; Prezoto et al., 2006; Pereira et al., 2007; Bichara-Filho et al., 2009; Fernandes et al., 2010; Picanço et al., 2010). This promotes their use in biocontrol programs. For example, social wasp colony of Polistes simillimus Zikán, 1951 (Hymenoptera, Vespidae) have been transfered to maize plantings to check Spodoptera frugiperda caterpillars (Prezoto and Machado, 1999). The social wasps are typically predators of a large variety of insects of apt size. These are detained and usually partially dismembered. Some Vespinae species are quite serious predators of other Hymenopterans. Vespa mabro sometimes preys upon honeybee and Vespa orientalis sometimes make bee-keeping hard in Israel (Rivnay and Bytinski-Salz, H, 1949). Vespa tropica var. Pulchra preys solely on the larvae and pupae of Polistes and Parapolybia species (Sakagami and Fukushima, 1957). Free (1970) explained foraging activity of Vespula germanica and V. Vulgaris for dead honeybees and about their trial to enter hives to obtain honey. A number of references to hymenopterous prey was given by him, including winged ants. Kemper and Dohring (1967) listed the prey of European wasp species and Van der Vecht, 1957 of the species in the Far East. Duncan (1939) provides further records. Polistes species also have similar habits eventhough their prey is smaller. P. Fadwzgae has the habit of theiving larvae from other colonies of same species (Sakagami and Fukushima, 1957b). Some species play a minor role as predators of caterpillars which feed on various crops (Rabb, 1960; Snelling, 1954; Morimoto, 1960-1)..A significant progress in the quality and weight of cabbage in plots exposed to foragingPolistes species of wasps was observed compared with cabbage in unexposed control plots. It showed the significant reduction in numbers of largePieris rapaelarvae due to the predation of wasps. [gould et al., 1984 ].
The Masarinae, Eumeninae and Euparagiinae are solitary to primitively social (nest-sharing without a workercaste), whereas Stenogastrinae, Polistinae and Vespinae are eusocial (group-living With sterile workers)(Spradbery, 1973b). Marcel G. Hermes and Andreas Köhler (2006) studied the flower visiting activity of polistine wasps. In flowers of 36 species of angiosperms (20 families) in the Green Belt, , and also on flowers of 54 species of angiosperms (21 families) in the CPCN pro mata, the presence of Foraging social wasps were seen. They observed Asteraceae as the most visited plant family on both localities studied. They also provided the list of plant species which was frequently visited by polistes wasps. So the vespids can be considered as good pollinators of plants.
Analysis of genetic diversity of wasps
Genetic diversity is central to the breeding success of most populations (Stiling, 2000). Diclining genetic variation can greatly affect or weakens a population growth and can renounce the recovery of endangered species. The DNA sequences in organisms are maintained throughout generations with very minor changes. Although such genetic stability is vital for the survival of species, considering in broader time scale, the survival of the species may depend on genetic variation for adapting to environmental changes. Thus an important charecterestic of the DNA in cells is their ability to endure rearrangements which could vary a specific gene combination present in any individual genome, as well as the timing and the expression level of these genes. Molecular tools are becoming progressively more common for applications in the field of entomology, including species identification (Roques et al., 2009), identification of immature life stages (Dittrich-Schroder et al., 2009),identification of pest insects like fruit flies (Armstrong et al., 1997), identification of forensically important insects like sarcophagid flies (Wells et al., 2001), identification of medically important insects like mosquitoes (Besansky et al., 2003) and, in a broader outlook, the establishment of deoxyribonucleic acid (DNA) barcoding libraries (Hajibabaeiet al., 2005). The sequence variations in the genomes of speciees can be used for their molecular barcoding and unambiguous identification.(Hajibabaeiet al., 2006)
An appraisal of the genetic diversity of wasp fauna of India can facilitate their accurate identification, determination of interspecies relationship and delineation of their phylogeny. Molecular barcoding data of wasps of India are unavailable for their accurate characterization despite their economic value as a predator of insect pests.[Kottickal L.V., 2013]
A trustworthy and accessible classification of species is elementary to research in biodiversity ecology, evolutionary biology and conservation biology. While a 1.5 million species have been described so far, this represents only a tiny fraction of the actual diversity present on Earth (Tudge, 2000; Wilson, 2003). Owing to the constant threat of loss of biodiversity, there is an increasingly urgent requirement to accelerate the pace of discovery of species and taxonomic databasing (Godfray, 2002). Even the routine identification of recognised species seems difficult, often demanding a highly specialized knowledge, hence becoming one of a limiting factor in ecological studies and biodiversity inventories (Monaghan et al., 2005). In response, recently, many new proposals have called for a more prominent role of competent DNA-based methods in the delineation and identification of species (Blaxter, 2004; Floyd et al., 2002; Hebert et al., 2003a; Tautz et al., 2003). Reactions to such proposals have widely ranged, from strongly supportive (Janzen, 2004; Proudlove and Wood 2003; Stoeckle, 2003) to strongly opposed (Lipscomb et al., 2003; Seberg et al., 2003; Wheeler, 2004; Will and Rubinoff, 2004). Using DNA-based methods for the delineation and discovery of new species, and thus their crucial role in taxonomy, represents an especially contentious issue in this regard. Unfortunately, much of this debate remained theoritical, with limited expirimental assessment of the benefits and restrictions of a DNA-based programme of discovery of species.
The database of insect sequences is growing swiftly. Genbank now claims nearly 100,000 insect sequences. Though 80,000 of those are sequences of Drosophila genes, a significant fraction of them is being used in Phylogenetic studies. Studies on insect systematics have now examined around 40 protein-coding genes, each of the major work on additional loci, majority of which are nuclear protein-coding, making the jump from Drososphila studies to more broader general application. The diversity of markers available has undenialbly furthered the cause of insect molecular systematics. However, this superfluity of markers also brings with it a risk of pluralism, in that the use of various estimators among studies makes comparison and synthesis tidious or unattainable. The most commonly sequenced regions in insect systematics are mitochondrial DNA (mtdna) and nuclear ribosomal DNA (rdna). As adjacent segments of DNA, they lend themselves for an easy comparison . (Michael S Caterino et al., 2000).
Mitochondrial DNA (mtdna) analysis has been used in the evolutionary study of animal species for more than 30 years (Brown et al., 1979; Mindell et al., 1997; Avise and Walker, 1999). Its higher rate of mutation and lower effective population size compared to nuclear DNA make mtdna a potent tool to probe for substantiation of reproductive isolation among lineages. This fact motivated a proposal to regiment DNA-based species identification by analyzing a consistent segment of the mitochondrial genome. By this approach, a sequence library from taxonomically established voucher specimens can be used as DNA identifiers for species, in a word, DNA barcodes (Hebert et al.,. 2003).
For animals, researches focused on a 648-bp segment of the mitochondrial gene called cytochrome coxidase I(COI). It can be quickly recovered from diverse species using a limited set of primers. Some commonly used regions are present for both mitochondrial and ribosomal genes, but never consistent across all taxa. In many cases a typical gene itself is being sequenced across for several studies, but, with regions sequenced for related taxa, this regions often do not found overlapping. For mitochondrial DNA the most recurrently sequenced genes are cytochrome oxidase 1 (COX1), COXII and 16s rdna, with 12s rdna not less. Of these COX1 and COXII has been sequenced over the widest variety of taxa, with homologous sequences. However due to its length, the exact region chosen changes for each study. A region of 16s gene equivalent roughly to position 12900- 13400 has been frequently sequenced across most taxa with the omission of Lepidoptera. In fact most of the protein coding genes perform approximately uniformly well, given alike length fragments. Nuclear rdna is of greater stability. Sequencing much or all of the 18s rdna gene became normal for most higher-level studies, although there are exceptions: the internal transcribed spacer and 28s regions dominate in studies of dipterans and hymenopterans. Phylogenetic studies using nuclear protein- coding genes are far less in number than of either mtdna or nuclear rdna. However, a few loci are becoming widely used, Of which EF- 1α has been the most popular. Its sequences have proven very useful for studies among specious groups and genera with in families. (Michael S Caterino et al., 2000)
DNA barcoding translates expert taxonomic knowledge of indicative morphologic characters into a broadly available format, enabling more people to identify species. In addition to assigning specimens to an identified species, DNA barcoding can fasten the new species discovery, as large sequence variations in animal mtdna generally indicate species status. For this method to be effective, it must be promising to Distinguish between mtdna variation in intraspecific and interspecific levels. Preservation of ancestral polymorphisms, , Pseudogenes, hybridization and the idiosyncrasies of mtdna inheritance posess potential problems. (Benasson et al., 2001; Moritz and Cicero, 2004; Thalman et al., 2004; Will et al., 2005). Investigations on various vertebrate and invertebrate groups showed that COI barcodes discriminate more than 95% of species (Ward et al., 2005; Hajibabaei et al., 2006). The discovery of new, cryptic species from existing, morphologically indiscriminate groups using DNA is neither controversial nor novel (Knowlton, 1993), and potential taxonomic reviews motivated by DNA barcoding results have been naturally left to experts for resolving based on morphological basis, behaviour and other salient features (Hebert et al., 2004b). It is to be anticipated that a successful global DNA barcoding program would provide a complete barcoding inventory for a greater part of described taxa in the foreseeable future, facilitating the systematic discovery of cryptic species. However, with 85% or more of species still unidentified in science, a great challenge lies in the potential application of DNA-based methods in the process of discovery and delineation of new species in poorly characterized taxa. [Michael T. Monaghan et al., 2005]
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