Biosystematics of the True Bugs (Heteroptera) of District Swat Pakistan

Abstract

In this study 4005 specimens of the suborder Heteroptera were collected during June 2014 - October 2017 from District Swat. Different collection methods eg. Sorting litters, beating vegetation, sweep net and light trap were used to collect specimens. Forty one species belonging to 35 genera, 11 subfamilies under seven families, namely, Pentatomidae, Scutelleridae, Reduviidae, Largidae, Lygaeidae, Coreidae, Alydidae were recorded. A total of 30 species were recorded first time from District Swat. These are Andrallus spinidens, Eocanthecona furcellata, Halys dentatus, Aeliomorpha lineaticollis, Adria parvula, Acrosternum graminea, Eurydema pulchra, Plautia fimbriata, Eysarcoris inconspicuous, Dolycoris baccarum, Hotea curculionoides, Solenosthedium rubropunctatum, Scipinia horrida, Rhynocoris marginatus, R. fuscipes, Polididus armatissimus, Neophysopelta schlanbuschi, Physopelta gutta, Dieuches uniguttatus, Lachnesthus singalensis, Spilostethus pandurus, S. hospes, Graptostethus nigriceps, Homoeocerus sigillatus, Cletus punctiger, Riptortus linaries and Riptortus pedestris. Four species Perillus bioculatus, Scotinophara ochracea, Rhyparothesus dudgeoni and Homoeocerus sigillatus were reported first time from Pakistan. Diagnostic characters and keys to studied families, subfamilies and genera were formulated based on reliable distinctive and consistent characters. All the taxa were briefly described morphologically and on morphometric bases. New host plants were also recorded during the study and are mentioned with their respective species. The identified taxa were reconfirmed with the help of identified species of true bugs which were housed in National Insect Museum, Islamabad, Pakistan Forest Institute Peshawar and Natural History Museum University of Karachi. Photographic details of adult specimens and male, female genitalia have been illustrated for each species. For DNA barcoding, Cytochrome Oxidase I (COI) gene sequences of species collected in this study were obtained. Of these nine Species, namely, Andrallus spinidens (MG298982), Neohalys acuticornis (MG298985), Adria parvula (MG298986), Scotinophara ochracea (MG298989), Hotea curculionoides (MG298987), Neophysopelta schlanbuschi (MG298988), Lachnesthus singalensis (SDP602021-17), Rhyparothesus dudgeoni (MG299061) and Homoeocerus sigillatus (MG298981) were barcoded for the first time. An increase in the mean K2P divergence was observed across different taxonomic levels. The mean intraspecific divergence was lowest in family Largidae (0.25%) followed by Reduviidae (0.4%), Lygaeidae (0.5%), Pentatomidae (0.6%), Coreidae (0.8%) and Alydidae (1.5%). The mean intrespecific divergence was lowest in family Alydidae (6.8%) followed by Reduviidae (8.3%) Pentatomidae (8.8%), Largidae (9.0%), Lygaeidae (9.1%) and Coreidae (11.6%). The mean divergence between the genera of the same family was lowest in family Alydidae (14.1%) followed by Lygaeidae (15.3%), Pentatomidae (16.7%), Coreidae (18.9%) and Reduviidae (25.1%). The average divergence between families was 23.2%. The mean A+T contents were higher in family Alydidae (68.2%) followed by Largidae (68.1%), Lygaeidae (67.6%), Pentatomidae (66.2%), Coreidae (65.9%) and Reduviidae (65.7%). In the present study Neighbor Joining, Maximum Likelihood and Maximum Parsimony analyses of the Heteroptera fauna of Swat on the bases of COI gene sequences were presented. Overall the barcode gap was distinct for between species, genera and at higher taxonomic levels. No overlaps in sequence divergence were found. In the phylogenetic analyses of family Pentatomidae all taxa belonging to the same genus clustered together with 65100% bootstrap support. Thus intraspecific and interspecific phylogenetic relationships were clearly established. The phylogenetic analyses showed that identification of species on morphological characters and molecular bases are extremely consistent. Species of the subfamily Asopinae clustered together with 81% bootstrap support. Scotinophara ochracea was the sister group to subfamily Asopinae with weak support. The sister group relationship between Eocanthecona furcellata and Andrallus spinidens was supported by 64% bootstrap value. Zicrona caerulea was in a basal position to other members of subfamily Asopinae. Member of the subfamily Pentatominae clustered together with 59-65% bootstrap value. The species of genus Eurydema showed monophyly with 68-74% bootstrap support. The relationship between Eurydema pulchra and Eurydema lituriferum was supported by 100% bootstrap value. The relationship recovered between species of genus Eurydema was [(Eurydema pulchra + Eurydema lituriferum) + Eurydema ventralis + Eurydema dominulus)]. Bagrada picta forms a sister group with Eurydema with weak support. The genera Halys, Neohalys and Erthesina clustered together with 66% bootstrap support. The relationship between Halys and Neohalys was supported by 99% bootstrap value. The species of genus Acrosternum clustered with 89% support and the species of genus Plautia clustered with 81% support. Nezara antennata and Nezara viridula clustered together with 100% bootstrap support. Adria parvula clustered with Eysarcoris inconspicuous at bootstrap value of 86%. Species of genus Dolycoris clustered in separate clade with 97% support. The relationship between the subfamilies of the family Pentatomidae recovered in the present study was (Pentatominae+ (Asopinae+Podopinae)). In the phylogenetic analysis of family Reduviidae species of genus Rhynocoris clustered together with 100% bootstrap support. The interspecific genetic distance of Rhynocoris marginatus was greater with respect to other species of the genus. The species of genus Polididus clustered together with 100% bootstrap support. In Neighbor Joining tree of family Largidae species of genus Physopelta and Neophysopelta clustered together in a single clade with 88% bootstrap support. In MP tree the Physopelta and Neophysopelta were at a distance from each other. In the phylogenetic trees of the family Lygaeidae species belonging to separate subfamilies form separate clades. The species of subfamily Rhyparochrominae clustered together with 52-62% bootstrap support. Lachnesthus singalensis and Rhyparothesus dudgeoni were sister groups with 63-65% bootstrap support. The relationship of Metochus uniguttatus and Dieuches schmitzi was supported by bootstrap value of 62-90%. The species of subfamily Lygaeinae clustered together with 92-98% bootstrap support. Species of the genus Spilostethus clustered together with 50-71% bootstrap support. The relationship between Spilostethus and Graptostethus was supported by 77-84% bootstrap value. In phylogenetic analysis of family Coreidae species of the genus Cletus clustered together with 57-66% bootstrap support. Genus Coreus clustered with Cletus with 70-71 % bootstrap support. The species of the genus Homoeocerus clustered together with 90-98% bootstrap support. The relationship between Coreus and Homoeocerus was supported by 55-56% bootstrap value. In the phylogenetic analysis of family Alydidae species of the genus Riptortus clustered together with 100% bootstrap support. Species of genus Alydus clustered with 99 % bootstrap support. The relationship between Alydus, Tollius and Megalotomus was supported by 76-93% bootstrap value. The distinct barcode gap and clustering of the taxa in the present study shows that DNA barcoding is quite helpful in species level identification of the group. The database of barcodes can be used by stakeholders for the easy identification of true bugs. This study is encouraging to use DNA barcodes as complement with a morphological taxonomy for easy identification and authentication of Heteroptera species.