Biodiversity Evaluation of Carabidae Beetles of a Rice Field (Ahangarkola: Qaemshahr) in Mazandaran Province, Northern Iran

Rice (Oryza sativa L.) is one of the most cultivated crop in northern Iran. The rice fields, is harbor a rich composition of insect fauna inhabiting vegetation, water and soil of the rice fields. The insects in this agro-ecosystems play different roles, some are herbivore and some other are natural enemies of herbivores. Ground beetles, Carabidae, are mainly predators and could effect on pest population as biological agent in different agro-ecosystems including rice fields. Since rice has been attacked by various pests, especially stem borer, Chilo suppressalis Walker (Lep.: Pyralidae), therefore identification and protection of the natural enemies in the field are important in reduction of pesticide applications. The Carabidae beetles as polypagous predators of many pests could also take attention in integrated pest management programs (IPM). Although this family is one of the largest family of beetles, it is studied very poorly in different agricultural ecosystems in Iran. Depending on crop and sequencing of growth stages of the crop in agricultural fields, ground beetles may vary among different species. Until 2015, 955 Carabidae species were recorded from different parts of Iran such as northern. For identification of active species of Carabidae in the rice field, present study was conducted. Several samplings were taken with pitfall traps at different growth stages of rice in a one-hectare rice field (Ahangarkola: a.s.l. 11 m, 36°, 30' N, 52°, 48' E) located in the Qaemshahr city (Mazandaran), in the 2015 -crop year. Every 10 days, the contents of pitfall traps were examined and transported to the laboratory and then, the number of the collected beetles were counted and recorded. The samplings were continued till two months after rice harvesting. Percentage of abundance and species diversity (Shannon-Weiner index) were calculated. The statistical tests were performed in Excel 2013. The Shannon-Weiner index was calculated by formula (Hʹ): Where pi is number of individuals of species i/total number of samples and Ln is natural basic logarithm. In sum, 16 species from 13 genera, nine tribes, and six subfamilies of Carabids beetles were collected and identified during crop seasons and two month after rice harvesting. The identified species were Acinopus (Acinopus) picipes (Olivier 1795) (1.18%), Bembidion (Trepanes) octomaculatum (Goeze 1777) (0.59%) and Elaphropus (Tachyura) lucasi (Jacquelin da Val 1852) (1.76%), from subfamily Trechinae, Brachinus psophia (Audinet-Serville 1821) (1.18%) from Brachininae, Pterostichus (Argutor) cursor (Dejean 1828) (11.76%), Pterostichus (Platysma) niger (Schaller 1783) (1.76%) and Poecilus cupreus (Linnaeus 1758) (25.88%) from Pterostichinae, Scarites (Parallelomorphus) subcylindricus (Chaudoir 1843) (0.59%), Clivina (Leucocara) laevifrons (Chaudoir 1842) (1.18%) from Scaritinae, Harpalus distinguendus (Duftschmid 1812) (0.59%), Harpalus (Pseudoophonus) rufipes (De Geer 1774) (27.65%) Anisodactylus (Pseudodichirius) intermedius (Dejean 1829) (0.59%), Acupalpus maculatus (Schaum 1860) (4.71%), Stenolophus abdominalis persicus (Mannerheim In Chaudoir 1844) (4.12%) from Harpalinae, Chlaenius (Epomis) amarae (Andrewes 1920) (11.76%) and Chlaenius (Amblygenius) dimidiatus (Chaudoir 1842) (5.29%) from Licininae. Among them H. rufipes with 27.65% and P. cupreus with 25.88% of all collected specimens were the most frequent species. They were present in all stages of plant growths in the rice field. The species of S. subcylindricus, B. octomaculatum, H. distinguendus, A. picipes and A. intermedius had the lowest frequency and seems to be occasional species in the rice field. Among 16 species, six species B. octomaculatum, C. amarae, P. cursor, E. lucasi, S. subcylindricus and A. intermedius were new for Mazandaran fauna. During the growing season until harvesting time, the highest number of insects and species were observed during reproductive growth and clustering stage in the field, although the comparison of Shannon-Weiner species diversity index did not show a significant difference for species diversity. The population of Carabidae was severely reduced one month after rice harvest, however their maximum abundance was observed two months after harvesting rice. The results of the present study indicates that due to the presence and appropriate diversity of the carabid species in the rice field as well as their predation activity, it is necessary to know more about the role of the carabid species in biological control of rice pests, specially rice stem borer, at future researches.