Review of Molecular Taxonomy Studies On
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Int. J. Entomol. Res. 04 (01) 2016. 25-36 Available Online at ESci Journals International Journal of Entomological Research ISSN: 2310-3906 (Online), 2310-5119 (Print) http://www.escijournals.net/IJER REVIEW OF MOLECULAR TAXONOMY STUDIES ON COLEOPTERA AQUATIC INSECTS Somayeh Gholamzadeh*, Ümit Incekara Department of Biology, Faculty of Science, Ataturk University, Erzurum- 25240, Turkey. A B S T R A C T With millions of species and their life-stage transformations, the animal kingdom makes taxonomy difficult. Insects are the most numerous group of animals, and its taxonomy is primarily based on morphological characters. However, molecular systems have been developed in recent years especially in order to discriminate closely related species and in order to identify the species which have not been distinguished by taxonomic methods currently employed. Over the last ten decades, the use of molecular methods, especially DNA sequence data has had a profound influence on taxonomy. The DNA sequences which are commonly used, occur either in the nucleus of the cell or in organelles such as mitochondria. This is a review article about molecular taxonomy studies on insects, especially Coleoptera aquatic ones. Keywords: Aquatic insects, molecular taxonomy, Coleoptera, nucleus and mitochondrial genes, review. INTRODUCTION (1,380/2,500), Hydrophilidae (1,800/2,320), Elmidae Molecular systematic studies have been started in the (1,330/1,850), Scirtidae (900/1,700) and Gyrinidae 1970 for the first time using ribosomal RNA for the (750/1,000). The Palaearctic (3,350 named as opposed classification of bacteria (Fox et al., 1980). In the last 20- to 3,900 estimated), the Neotropical (2,510/3,900) and 25 years, molecular instruments in various organism the Afrotropical (2,700/3,750) regions have the most groups are being used widely for this purpose (Baker species, followed by the Oriental (2,200/3,580) and the and Palumbi, 1994; Sperling et al., 1994; De Salle and Australasian (1,300/2,100), the Nearctic (1,420/1,550) Birstein, 1996). A final taxonomic system for the animal being by far the poorest in terms of diversity (Jäch and kingdom will probably include at least 10 million species Balke, 2008). In this article, many molecular taxonomy partitioned among more than a million genera. Given studies, was revised up from the past to the present. In such high diversity, there is a growing realization that it this context, not directly related to aquatic insects or is critical to seek technological assistance for its initial some very specific evaluation studies were excluded. description and its subsequent recognition (Godfray, The advantages and disadvantages of some 2002; Blaxter, 2003). There are 1,200,000 species of methodological differences to ensure a better insects in the world and among all insects, less than 3 understanding of the subject was discussed in detail. percent are aquatic beetles. Jäch and Balke. (2008) The application of DNA data in taxonomy and species estimate that there are currently about 18,000 species of diagnosis has aroused a great deal of controversy, but water beetle of which 70% have been described. About there is general agreement that genetic information is thirty families have aquatic representatives, 25 of them useful for associating different developmental stages of having at least half of them aquatic. The estimates for the organisms and for identifying partially preserved dominant families are, from October 2005, Dytiscidae specimens unsuitable for morphological study (Vences with_______________________________________ 3,908 species, 5,000 being estimated,___________________________ Hydraenidae et al., 2005; Wheeler 2004; Will et al., 2005). DNA data * Corresponding Author: provide a character system universal to all life stages Email: [email protected] with the potential to overcome the problems of working © 2016 ESci Journals Publishing. All rights reserved. with different semaphoronts. A DNA-based approach has 25 Int. J. Entomol. Res. 04 (01) 2016. 25-36 already been used to associate different developmental they typically present fewer alignment issues than stages in order to identify agricultural pests and invasive ribosomal genes (Danforth et al., 2005). On the other species (Ball and Armstrong, 2006; Harper et al., 2005; hand, these genes do not always contain reliable priming Miller et al., 1999; Rao et al., 2006; Scheffer et al., 2006), sites, they can be present in multiple paralogous copies, forensically important insects (Wells and Sperling, and they may contain lengthy introns that complicate 2001), larval parasitoids (Agusti et al., 2005) and amplification, alignment, and sequencing (Sanderson endangered species in their early life stages (DeSalle and and Shaffer, 2002). Wild and Maddison. (2008) used the Birstein, 1996). Initial attempts have also been made to nuclear protein-coding genes for beetle systematics. survey larval or mixed larval and adult assemblages with After screening 24 genes for phylogenetic potential, they DNA methods (Barber and Boyce, 2006; Paquin and selected eight of these for sequencing across 31 test taxa Hedin, 2004). The increasing taxonomic content of DNA of coleoptera. databases and rapid sequencing technology now permit Eukaryotic nuclear genes encoding for ribosomal RNA tree construction at ever larger scales (Hibbett et al., subunits are organized intandemly repeated units which 2005; Kallersjo et al., 1998; McMahon and Sanderson, consist of the genes for the 18S, the 5.8S and the 2006; Soltis et al., 1999). However, traditional 28SrRNA subunits, separated by transcribed (ETS, ITS1 phylogenetic methodologies struggle to accommodate and ITS2) and non-transcribed (IGS) spacers. The 28S these huge data sets, whilst newly developed techniques, subunit is the largest one and it has been shown to be a more capable of coping with largescale analyses, have mosaic of core regions and hypervariable ''expansion not become generally established. In the last decade, segments'' (Clark et al., 1984), also called ''Divergent technical progresses in molecular biology (e.g. Saiki et Domains'' (Hassouna et al., 1984). Core segments have al., 1985; Mullis et al., 1986) have allowed evolutionary precise counterparts in prokaryotic rRNAs. They are biologists to collect large DNA sequence data sets in a thought to play an essential role in the ribosome reasonably short amount of time. This has opened the function and have very conserved nucleotide sequences way for extensive studies on the pattern of evolution of even among distantly related taxa. Divergent Domains several mitochondrial and nuclear genes (Simon et al., do not have precise counterparts in prokaryotic rRNAs 1994) and for using DNA sequences to reconstruct and they vary considerably across taxa in both primary phylogenetic relationships at different taxonomic levels sequence and length. Traditionally, 12 divergent (Thomas et al., 1989; Swofford et al., 1996). domains are recognized in metazoan 28S rRNA which Molecular markers can be divided into DNA markers and have been named D1 to D12 (Hassouna et al., 1984; protein markers. DNA markers have been widely used Michot et al., 1984). The D7 domain can be furtherly due to the disadvantages of allozymes and isozymes divided into the domains D7a and D7b (Hassouna et al., which can be referred as protein markers. The 1984). Single-stranded rRNA sequences have the thousands of protein-coding genes in the eukaryotic property of folding, bending and pairing within nuclear genome present the richest untapped source of themselves using stretches of complementary sequence. genetic data for phylogenetic research. These genes Therefore they assume a secondary structure consisting show a number of favorable properties for phylogenetic of paired regions, called stems, interrupted with analysis (Wiegmann et al., 2000). They evolve more unpaired regions (loops and bulges). Map of 28S rDNA of slowly and are less prone to base-composition bias than Drosophila melanogaster (Hancock et al., 1988) with mitochondrial markers (Lin and Danforth, 2004), and divergent domains indicated in black (Figure 1.). Figure 1. Map of 28S rDNA of Drosophila melanogaster. 1 2 3 4 5 6 7 8 9 10 11 12 5’ 3’ 0 500 1000 1500 2000 2500 3000 3500 4000bp 26 Int. J. Entomol. Res. 04 (01) 2016. 25-36 Within beetles sequences of 18S rDNA were used to the technical feasibility of sequencing their entirety reconstruct phylogeny of Adephaga (Shull et al., 2001), (Hwang et al., 2001; Yamauchi et al., 2004). This Hydradephaga (Ribera et al., 2002) and Carabidae increasing availability of mtgenome data invites (Maddison et al., 1998), and to clarify the comparative study. In addition to the large amount of interrelationships between the suborders of Coleoptera nucleotide data that is useful for deep-level phylogenetic (Caterino et al., 2002). It contains both slow- and fast- studies (Gray et al., 1999; Nardi et al., 2003; Cameron et evolving sections and is potentially useful for resolving al., 2004; Cameron et al., 2006; Cameron et al., 2007), relationships over a wide hierarchical range (Ribera et mtgenomes possess a number of evolutionarily al., 2002). This gene also yielded a good resolution interesting features such as length variation (Boyce et within Histeridae, as more than the ′normal′ sequence al., 1989), altered tRNA anticodons or secondary variation was found within this taxon (Caterino and structures (Steinberg and Cedergren, 1994; Eddy, Vogler, 2002). However, it should also be mentioned that