Species diversity of phytoseiid mites on different ecosystems in Sari district

Mites of the Phytoseiidae family have been extensively studied as biological control agents of different mites and insect pests. Some species also feed on nematodes, fungal spores, pollen and exudates from plants and insects. About 2,300 phytoseiid species belonging to 90 genera have been described in this family (Chant and McMurtry 2007). Considerable efforts have been made in recent years to the collection and identification of the predaceous phytoseiid mites in Iran (Rahmani et al. 2010). Despite some studies on phytoseiid mites in Iran, our knowledge remains limited about their fauna and diversity in Mazandaran province. The data of these studies showed that until recently, only 75 species were reported from Iran. The objective of this study was to evaluate the species diversity of Phytoseiidae and access to effective predatory mites for biological control of injurious mite pests in Sari, the center of Mazandaran province (Southern coast of the Caspian Sea, 35 ° 47'-36 ° 35' N, 50 ° 34'-54 ° 10' E)
Samples were taken from 80 plant species belonging to 46 plant families including forest trees, orchards and farm crops representing three types of ecosystems from September 2011 to October 2012. Harvested samples of each plant were separately collected in plastic bags and labeled with region and date of collection. The bags were transported to the laboratory on the same day and stored in a refrigerator at about 4°C for up to a week, until the materials washed for mite extraction. Samples were composed of leaves, stems and shoots of different ages and the number of leaves per sample varied between plant species. In order to assimilate the samples, a volume nearly equal mass of each sample were put in a two-liter water container. The mites were floated on water by adding 1.5 liters of tap water and a few droplets of detergent. The plant leaves and shoots were shaken for several times until the mites fall from the plants into water. Plant materials then removed from the solution and discarded. Mites in the solution were separated by pouring the solution through sieves of 20, 50, 200 and 400 meshes. Mites transferred into a labeled glass jar for further processing and identification in the laboratory. The mites were cleared in Nesbitt's fluid and mounted in Hoyer’s medium on microscope slides. The slides were dried at 45 °C for 1-2 weeks. Then the edge of the coverslip was sealed with colorless nail polish to prevent absorption of the air moisture. All specimens collected were nominally identified to species level by using a Nikon phase contrast microscope (E600) and related identification keys.
The scientific names of the plants were adapted from a dictionary of Iranian plant names (Mozaffarian 1998). The ecological indices including Margalef's richness, Simpson, Shannon-Wiener and Pielou's evenness were calculated for species diversity, dominance, richness and evenness of the mites in different ecosystems. Some mite specimens were sent to Dr. E.A. Ueckermann of the ARC-Plant Protection Research Institute, Pretoria, South Africa for identification or species confirmation.
A total number of 946 mites of 19 species belonging to 8 genera of three phytoseiid subfamilies namely Amblyseiinae, Typhlodrominae and Phytoseiinae were identified (Table 1). Most individual mites collected in this study, 698 mites in total (73%), belonged to 12 species of the Amblyseiinae which 68% of them (475 in total) were Transeius caspiansis and 13% (90 mites in total) were Euseius amissibilis. Phytoseius plumifer, the single species of the Phytoseiinae and the species of Typhlodrominae amounted to 16% (152 in total) and 10% (96 in totals) of the collected mites, respectively. In this study Amblyseiinae also had the highest proportion of species (63%), while Typhlodrominae and Phytoseiinae had 31% and 5% of the species, respectively. Most phytoseiids collected in this study were mentioned above species that formed 76% (a total of 717) of the whole collected mites. These species were the most frequently found predators on varieties of plants. They were found on plants associated with tetranychid, tenuipalpid and eriophyid mites and small insect pests such as thrips and whiteflies. They were very common and were examined from 80 plant species, they observed on 59, 22 and 26 plants, respectively. It was interesting to observe these predators on some plants that there were not phytophagous mites. Therefore these species are generalist predators and are known to feed on pollen and exudates of plants and insects. Overall, mean mite's biodiversity indices of Margalef's richness, Simpson, Shannon-Wiener and Pielou's evenness were 1.656, 0.69, 1.546 and 0.525, respectively. Actually, when a community has many about equally abundant species, it is said to have high species diversity. But when a few species are present or like this study only a few species are abundant, then species diversity is low. The low Shannon-Wiener and Pielou's evenness indices also showed relatively low biodiversity in the area.
Despite that 19 phytoseiids species were found in Sari, the present study revealed a low diversity of phytoseiid mites in this region. Most phytoseiids collected in this area belonged to Transeius caspiansis, Euseius amissibilis and Phytoseius plumifer (a total of 717) species. However, it was expected that many additional species could be found by similar studies in the same area, especially when other plant species were sampled. The diversity of plants in the forest, orchards and farm crops were far greater than the number of plant species sampled in this study.
Acknowledgments: This paper is a part of MSc thesis of the senior author which was financially supported by Sari University of Agricultural Sciences and Natural Resources, Sari, Iran. Also thanks are extended to Dr. E. A. Ueckermann (Plant Protection Institute, Pretoria, South Africa who helped with the confirmation and identification of mite specimens. We also thank our colleague Dr. H. Zali for identification of some plant species.