Butlerius butleri Goodey, 1929 (Rhabditida) from Iran with the Phylogenetic Position of the Species

Biocontrol of nematode pests is becoming more important as highly effective, but toxic nematicides are progressively being withdrawn from world markets (Zuckerman and Esnard, 1994; Nico et al., 2004). Butlerius constitute a genus that can play an important role in reducing population levels of plant parasitic nematodes (Khan and Kim, 2007). Moreover they also contribute toward stimulating the cycling of plant nutrients, which may enable plants to better withstand any nematode burden on their roots (Yeates and Wardle, 1996). Although members of the family Diplogasteridae occupy many different ecological niches, they are not rich in terms of species being identified (Abolafia, 2006). This group of nematodes represent predators (Khan and Kim, 2007), with Mononchoide being the most important genus (Khan and Kim, 2007). Another predator species, Butlerius degrissei however, also feeds on bacteria present in the vicinity of its niche if plant parasitic nematodes are not present (Grootaert et al., 1977). The taxanomic position of the genus Butlerius was established by Goodey in 1929. Individuals belonging to this genus are characterized by the presence of long labial setae, stomas that are divided in two parts: thorn-like teeth and filiform tails. Individuals of this species inhabit rotting materials and compost, but rarely aquatic niches (Andrassy 2005). Andrassy (1984) proposed the genus Monobutlerius to represent the monodelphic species, whereas later Ebsary (1986) proposed the genus to be Parabutlerius. Sudhaus and Furst von Lieven (2003), however, considered both these genera as Butlerius. In addition, Andrassy (2005) suggested separation of Butlerius and Monobutlerius mainly based on their female genital systems (monodelphic and amphidelphic) and presence/absence of the postvulval sac. Finally, Ahmad et al. (2009) redescribed B. butleri Goodey, 1929 and synonymized this species with B. filicaudatus Adam, 1930 and B. singularis Lordello and Zamith, 1959. Thus far, the genus Butlerius has not been studied using rDNA. Therefore, the goals of this investigation were to (i) amplify the 18S rDNA marker using deoxyribonucleic acid (DNA) from the Iranian Butlerius specimens, (ii) describe the juvenile stage of B. butleri (not described previously) from Iran, and (iii) elucidate the phylogenetic position of this B. butleri species within members of the family Diplogasteridae. The manuscript thus presents a new taxonomic report of B. butleri collected from vermicompost in Iran along with its molecular characterization and phylogenetic position based on use of the 18S rDNA marker.