Two new species of Xiphinema Cobb. 1913 (Nematoda:Dorylaimida) from high altitudes of Bhutan alongwith a key and compendium to the species of Group 1 sensu Loof & Luc, 1990

Two new species of Xiphinema collected from high altitude of Bhutan have been described and illustrated. X. bhutanense sp.n collected from the rhizosphere of Blue Pine (Pinus sp.) at an altitude of 2500 meters above sea level (ad) in West Bhutan, is characterized by having L=2390–2820 μm; a = 48–58; b = 6.2–8.1; c = 53–77; c’ = 1.2–1.5; V =21–23%. odontostyle = 118–123 μm; odontophore = 64–70 p; continuous head, mono-opisthodelphic gonad, posteriorly inclined vagina, dorasally convex conoid tail with a ventral digitate projection, 5 pairs of cervical body pores and 6 pairs of caudal pores. X. bambusi sp. n. collected from the rhizosphere of Bamboo (Bambusa sp.) at an altitude of 3270 meters asl in East Bhutan, is charcterized by having L = 2180–2395 μm; a = 41–47,; b = 5.4–6.2; c = 34–38; c’ = 1.8–2.3; V = 23–26%; odontostyle = 108–120 p; odontophore = 65–80 μm; slightly set off head, mono-opisthodelphic gonad with vagina at right angle to the body axis, dorsally convex conoid tail with a ventral digitate projection, slightly setoff lip region and 9 pairs of caudal pores. These two newly described species ha%e been categorised under Group 1 of Xiphinema sensu Loof & Luc, 1990, due to the monoopisthodelphic gonad completely devoid of pre-uterine sac. A diagnostic key and compendium to all the 12 species of this group is also provided. An amendment of the specific names of two Xiphinema species described by Sigh & Khan, 1997 is proposed: X. digicaudatum in place of X. digicaudata, and X. gracilicaudatum in place of X. gracilicaudatus.