International Journal of Biodiversity and Conservation Vol. 3(12), pp. 637-649, November 2011 Available online at http://www.academicjournals.org/IJBC ISSN 2141-243X ©2011 Academic Journals Full Length Research Paper Oak gall wasps (Hymenoptera: Cynipidae) species composition using diversity and similarity indexes across different locations of Oak forest, West- Azerbaijan, Iran Mohammed-Reza Zargaran*, Sargon Odisho, Farokh-Takin Babakhani and Bagher Hoseinpour Agicultural and Natural Resources Research Center of West-Azerbaijan, Uremia, Iran. Accepted 27 September, 2011 Patterns of the distribution of species diversity are the result of ecological, physical and historical factors. Beta diversity is an important property of ecosystems because it provides information about the partitioning of habitats by species. The objectives of this study were to determine the level of oak gall wasps diversity present in five different locations and to study the similarity among these locations. The highest amount of Simpson (0.95) and Shannon (2.6) entropy index were recorded in Ghabre-hossein and Dare-ghabr. The Jaccard and Sorensen coefficients revealed extremely close results with multiple site similarity. The multiple-similarity measures indicated that similarity in gall composition and community between collecting sites was generally between 0.25 and 0.97. Our results suggest that more oak gall wasps species had an aggregated distribution, and gall wasps diversity shows a strong beta diversity component. Presence of the rare gall wasps species affected on multiple site similarity value. Difference in the local distribution of oak species, especially oak subspecies, and the climate of the locations shall be considered as one main factor in species diversity and the distribution of gall wasp species in different locations. Key words: Diversity, gall, wasps, similarity, community, distribution. INTRODUCTION The number of equally-common species required to give a particular value of an index is called the "effective number of species". This is the true diversity of the community. Converting indices to true diversities (effective numbers of species) gives a set of common behaviors and properties. After conversion, diversity is always measured in units of the number of species (Jost, 2006). Beta diversity is generally thought of as the change in diversity among various Alpha diversities (variation in species composition among geographic regions) (Magurran, 2004). There exists a wide variety of methods for measuring Beta diversity, among which similarity measures are the simplest and the most commonly used for calculating Beta diversity from *Corresponding author. E-mail: Zargaran391@yahoo.com. Tel: 00989149371708. Fax: 00984412622221. abundance or presence/absence data (Wolda, 1981; Koleff et al., 2003). Both diversity and similarity indices can be used to compare differences between communities or samples from communities (Peet, 1974; Koleff et al., 2003, Magurran, 2004). The classical Jaccard (1912) and Sorensen (1948) indices were based on both the number of species present in samples and the numbers only seen in each of them (Koleff et al., 2003). Sorenson’s measure is regarded as one of the most effective presence/absence similarity measures (Sørensen, 1948; Wolda, 1981). Lennon et al. (2001) noted that if samples differ greatly in terms of their species richness, Sorenson measures will always be large. Another simple mathematical equation that measures the similarity of pairs of sites is the Jaccard index (Magurran, 1988). The widely used Sorensen and Jaccard similarity index led to identification of species composition in each of the two sites and the species shared between them (Novotny and Weiblen, 2005). Morisita index