Two new species of the genus Sectonema Thorne, 1930 (Nematoda, Dorylaimida, Aporcelaimidae) from Iran, with new insights into its evolutionary relationships.

Two new species of the genus Sectonema found in northern Iran are characterized, including morphological descriptions and molecular (18S-, 28S-rDNA) analyses. Sectonema tehranense sp. nov. is distinguished by its 7.22 - 8.53 mm long body, lip region offset by constriction and 24 - 31 µm wide with perioral lobes and abundant setae- or cilia-like projections covering the oral field, mural tooth 15.5 - 17 µm long at its ventral side, neck 1091 - 1478 µm long, pharyngeal expansion occupying 61 - 71% of the total neck length, female genital system diovarian, uterus simple and 3.9 - 4.2 times the corresponding body diameter long, transverse vulva (V = 49 - 59), tail short and rounded (44 - 65 µm, c = 99 - 162, c' = 0.6 - 0.8), spicules 111 - 127 µm long, and 7 - 10 spaced ventromedian supplements with hiatus. Sectonema noshahrense sp. nov. displays a 4.07 - 4.73 mm long body, lip region offset by constriction and 23 - 25 µm wide with perioral lobes and abundant setae- or cilia-like projections covering the oral field, odontostyle 14 - 14.5 µm long, neck 722 - 822 µm long, pharyngeal expansion occupying 66 - 68% of the total neck length, female genital system diovarian, uterus simple and 2.4 - 2.7 times the corresponding body diameter long, transverse vulva (V = 54 - 55), tail convex conoid (39 - 47 µm, c = 91 - 111, c' = 0.8 - 0.9), spicules 82 µm long, and seven spaced ventromedian supplements with hiatus. Molecular analyses confirm a maximally supported (Epacrolaimus + Metaporcelaimus + Sectonema) clade and a tentative biogeographical pattern, with sequences of Indolamayan taxa forming a clade separated from those of Palearctic ones. Parallel or convergent evolution processes might be involved in the phylogeny of the species currently classified under Sectonema. This genus is certainly more heterogeneous than previously assumed.

Description and molecular characterization of Trachactinolaimus persicus sp. n. from Iran (Nematoda, Dorylaimida, Actinolaimidae), with new insights into the taxonomy and evolutionary relationships of the genus.

A new species of the free-living nematode genus Trachactinolaimus, collected in natural habitats of northern Iran, is described, including morphological and molecular (28S-rDNA) data. Trachactinolaimus persicus sp. n. is characterized by its 1.95-2.44 mm long body, lip region weakly offset by depression and 18-20 µm wide, odontostyle 25-27 µm long, neck 540-636 µm long, pharyngeal expansion occupying one-half of the total neck length, bipartite uterus 2.6-3.9 body diameters long, vulva (V = 49-53) pore-like, tail long and filiform in both sexes (174-223 µm, c = 10.0-13.4, c' = 5.9-7.0 in females, 165-196 µm, c = 10.7-13.8, c' = 4.6-5.8 in males), spicules 68-75 µm long, and 12-14 almost contiguous ventromedian supplements with hiatus. Molecular data supports the monophyly of the genus and the hypothesis that Dorylaimidae are the sister group of actinolaims. The taxonomy of Trachactinolaimus is updated, including diagnosis, list of species, key to their identification, and a compendium of their main morphometrics. Dominiactinolaimus is regarded as its junior synonym.

The enigmatic genus Loofilaimus (Nematoda, Dorylaimida, Loofilaimidae) revisited 25 years after, with remarkable new insights into its phylogeny.

The evolutionary relationships of the nematode genus Loofilaimus are explored with an integrative approach, combining morphological and molecular (28S-rDNA) data. Never recorded since its original description in 1998, the finding of fresh specimens of its type and only species, L. phialistoma, allowed us to obtain SEM observations and sequencing, both for the first time, resulting in relevant aspects to elucidate its phylogeny. Morphologically, the genus is characterized by two autapomorphies affecting its lip region and pharynx. Molecular study revealed that it represents a very restricted evolutionary trend within Dorylaimida. The clade (Nygolaimina + (Loofilaimus + Dorylaimina)) is well supported. Loofilaimidae is accepted as a separate and valid family, which should also include Bertzuckermania.

Morphological and molecular characterization of Metaxonchium magnum sp. n. from Iran (Nematoda, Dorylaimida, Belondiridae), with new insights into the phylogeny of the genus.

A new species of the genus Metaxonchium is described from a natural habitat in Iran. Metaxonchium magnum sp. n. is characterized by its 3.62-4.65 mm long body, lip region cap-like and offset by constriction and 13-16 µm wide, odontostyle fusiform and 14-17 µm long, neck 1016-1359 µm long, both parts of the pharynx separated by a short isthmus-like narrowing, pharyngeal expansion occupying 74.2 (73-77)% of total neck length in females and 70.4 (66-72)% in males, female genital system mono-opistho-ovarian, didelphic, anterior genital branch a large uterine sac with a small terminal mass occupying 7-14% of body length, posterior uterus long and tripartite with a Z-like differentiation, V = 50-52, caudal region short and rounded (24-41 µm, c = 99-161, c' = 0.5-0.7), spicules 90-105 µm long and 10-13 spaced ventromedian supplements with hiatus. Analysis of D2-D3 28S rDNA sequences of the new species suggests that Metaxonchium might not be a monophyletic taxon, a matter that should be confirmed after future research.

On the identity of the genus Epacrolaimus Andrássy, 2000 (Nematoda, Dorylaimida), with new insights into its phylogeny.

The type species of the genus Epacrolaimus, Epacrolaimus declinatoaculeatus, is studied from the re-examination of type material of Aporcelaimus vorax, its junior synonym, and the observation of several Iberian populations and a few Iranian specimens. Morphologically, it displays a recognizable morphological pattern characterized by, among other features, the incurved nature of its odontostyle aperture, presence of perioral liplets or lobes, lip region 24-31 µm wide, odontostyle 21-25 µm long and comparatively anterior location of S2N pharyngeal gland nuclei. Nevertheless, variations in some morphological traits (vagina shape and tail shape) and in several morphometrics (body length, uterus length, vulva position, tail length and spicule length) are also noted. Sequences of D2-D3 domains of the 28S rDNA, 18S rDNA and COI mtDNA were obtained from several Iberian populations. Their analyses, in particular those from D2-D3 sequences, revealed the existence of a highly supported clade ((Epacrolaimus + Sectonema) + Metaporcelaimus), with a closer relationship between Epacrolaimus and Palaearctic populations of Sectonema, whereas the remaining aporcelaimid genera occupied placements in other clades. These results are discussed, with especial emphasis on the intricate separation of Epacrolaimus and Sectonema, which display significantly different protruding stomatal structure in spite of their close evolutionary relationship as derived from molecular trees.

Morphological and molecular characterization of Aporcelinus abeokutaensis sp. n. (Dorylaimida, Aporcelaimidae) from Nigeria.

A new species of dorylaimid nematode, Aporcelinus abeokutaensis sp. n., collected from a watermelon field in Nigeria, is described, illustrated and molecularly (D2-D3 28S ribosomal DNA) studied. It is characterized by its 1.18-1.52-mm-long body, lip region offset by weak constriction, 15.5-17.5 µm broad with perioral liplets, odontostyle 18-21.5 µm long at its dorsal side or 1.1-1.3 times the lip region diameter, neck 333-401 µm long, pharyngeal expansion occupying 45-51% of total neck length, uterus simple and 0.7-1.5 times the corresponding body diameter long, V = 48-53, tail conical with finely rounded tip (33-52 µm long, c = 26-41, c' = 1.3-1.9) and a variably distinct dorsal concavity, and male unknown. Molecular analysis reveals that the new species grouped with other species of Aporcelinus in a highly supported clade, confirming the monophyly of the genus.

Morphological and molecular characterization of Aporcella femina sp. n. (Dorylaimida, Aporcelaimidae) from Nigeria.

A new species of the genus Aporcella collected from a watermelon field in Nigeria is described, including its morphological and molecular (small subunit (SSU) and large subunit (LSU) ribosomal DNA (rDNA)) characterization. Aporcella femina sp. n. is distinguished by its 3.21-3.64 mm-long body, inner cuticle layer with fine but distinct transverse striation, lip region offset by deep constriction, 22-25 µm broad, odontostyle 20-26 µm, neck 661-811 µm long, pharyngeal expansion occupying 52-56% of the total neck length, female genital system didelphic-amphidelphic, uterus 191-350 µm or 1.9-3.3 mid-body diameters long, V = 52-57, tail short and convex conoid (35-48 µm, c = 72-98, c' = 0.7-0.9) and males absent. Phylogenetic analyses based on the partial sequence of SSU and LSU (D2-D3) rDNA revealed a close relationship of A. femina sp. n. with other Aporcella species, confirming the monophyly of the genus as well as its association to a clade made of several taxa characterized by the absence of pars refringens vaginae.

Study of two species, one new and one known, of the genus Aporcella Andrássy, 2002 (Dorylaimida, Aporcelaimidae) from Iran, with a note on its phylogeny.

Two species of the genus Aporcella, one new and one previously known, collected from cultivated fields in Iran are studied. Description, morphometrics, illustrations (both line and microphotographs) and D2-D3 sequences are provided for Aporcella talebii sp. n., which is characterized by its 1.66-2.02-mm-long body, lip region offset by constriction and 15-17 µm broad, odontostyle 14-17.5 µm long, neck 412-484 µm long, pharyngeal expansion occupying 46-50% of total neck length, uterus simple and 1.6-2.0 times the corresponding body diameter long, V = 52-59, tail conical (40-50 µm, c = 37-47, c' = 1.1-1.4) with a weak but perceptible dorsal concavity at the end and male absent. Morphometrics, microphotographs and D2-D3 sequences of Aporcella simplex are also presented, this being its first Asian record. Molecular analyses confirm the monophyly of the genus, its close relationship with other taxa lacking pars refringens vaginae and the polyphyly of Aporcelaimidae.

Morphological and molecular characterization of Labronema montanum sp. n. (Dorylaimida, Dorylaimidae) from Spain.

A new species of the genus Labronema, collected in a natural mountain habitat of the southern Iberian Peninsula, in Spain, is studied, including its morphological and morphometric characterization, SEM observations, and D2-D3 28S-rRNA sequences. Labronema montanum sp. n. is distinguishable by its 1.56 to 2.08 mm long body, with lip region being offset by constriction and 19 to 24 µm broad, odontostyle 21 to 29 µm long, neck 417 to 551 µm long, pharyngeal expansion 205 to 272 µm long, the presence of three cardiac lobes at the pharyngo-intestinal junction, a long and tripartite uterus, longitudinal vulva (V = 57-60), a short and rounded caudal region (19-35 µm, c = 56-86, c = 0.5-0.8), spicules 65 to 76 µm long, and 20 to 25 nearly contiguous ventromedian supplements with hiatus.A new species of the genus Labronema, collected in a natural mountain habitat of the southern Iberian Peninsula, in Spain, is studied, including its morphological and morphometric characterization, SEM observations, and D2-D3 28S-rRNA sequences. Labronema montanum sp. n. is distinguishable by its 1.56 to 2.08 mm long body, with lip region being offset by constriction and 19 to 24 µm broad, odontostyle 21 to 29 µm long, neck 417 to 551 µm long, pharyngeal expansion 205 to 272 µm long, the presence of three cardiac lobes at the pharyngo-intestinal junction, a long and tripartite uterus, longitudinal vulva (V = 57-60), a short and rounded caudal region (19­35 µm, c = 56-86, c = 0.5-0.8), spicules 65 to 76 µm long, and 20 to 25 nearly contiguous ventromedian supplements with hiatus.

Morphological and molecular characterization of Lenonchium zanjanense sp. n. (Dorylaimida, Nordiidae) from Iran, with new insights into the phylogeny of the genus and a revision of its taxonomy.

The new species Lenonchium zanjanense sp. n. is described from a natural habitat of Zanjan province, Iran, including line, light microscopy and scanning electron microscopy illustrations and a molecular (18S, 28S) study. It is characterized by its 3.50-4.51 mm long body, rounded lip region, continuous and 13.5-15.5 µm broad, odontostyle 21-24 µm long, neck 362-490 µm long, double guiding ring, pharyngeal expansion 190-285 µm long, female genital system didelphic-amphidelphic, uterus simple and 185-320 µm long or 3.4-5.9 times the corresponding body diameter, vulva nearly equatorial (V = 45-53), tail conical-elongated to filiform (90-165 µm, c = 23-43, c' = 2.4-5.3) with three or four mucro-like projections at the tip, spicules 58-64 µm long and 16-21 contiguous ventromedian supplements ending at the level of the anterior end of the spicules. The taxonomy of the genus is updated, with an emended diagnosis, list of species, key to their identification and a compendium of their main morphometrics. Lenonchium asterocaudatum is regarded as identical and a junior synonym of L. denticaudatum. New insights into the phylogeny of the group are also provided, and the classification of Lenonchium within Nordiidae is seriously questioned.

Metaxonchium toroense n. sp. (Nematoda, Dorylaimida, Belondiridae) from Costa Rica, with the first molecular study of a representative of the genus.

The new species Metaxonchium toroense n. sp. from natural habitats of Costa Rica is described, including light microscopy (LM), scanning electron microscopy (SEM) and molecular (D2-D3 28S rDNA) analyses. The new species is characterized by its general size, the dimensions and appearance of its lip region, the length of the odontostyle and its fusiform aspect, the length of the neck and its pharyngeal expansion, the reduction of the anterior genital branch to a very short uterine sac without any rudiment of ovary or oviduct, tripartite and non-echinophor posterior uterus, the somewhat posterior vulva position, the length and shape of the caudal region, and the absence of males. Molecular analyses, the first to be performed on a Metaxonchium species, show a close relationship of the new species with representatives of the genera Axonchoides and Syncheilaxonchium.

Morphological and molecular characterization of two new species of the genus Aporcelinus Andrássy, 2009 (Nematoda, Dorylaimida, Aporcelaimidae) from the USA, with new insights on the phylogeny of the genus.

Two new species of the genus Aporcelinus from the USA are described and illustrated. Aporcelinus floridensis sp. n. is characterized by its 1.12-1.52 mm long body, lip region offset by marked constriction and 14.5-17.0 µm broad with perioral liplets, odontostyle 16.5-20.0 µm at its ventral side and 1.1-1.2 times the lip region diameter, neck 316-395 µm long, pharyngeal expansion occupying 43-48% of total neck length, uterus simple and 33-56 µm long or 0.8-1.2 times the corresponding body diameter, V = 48-54, female tail conical (36-49 µm long, c = 27-41, c' = 1.2-2.0) with finely rounded terminus and no hyaline portion, and male absent. Aporcelinus paolae sp. n. is characterized by its 1.29-1.80 mm long body, lip region offset by marked constriction and 14-16 µm broad, odontostyle 15-17 µm at its ventral side and 1.0-1.1 times the lip region diameter, neck 314-397 µm long, pharyngeal expansion occupying 43-53% of total neck length, uterus tripartite and 128-164 µm long or 2.6-3.6 times the corresponding body diameter, V = 53-57, female tail conical (30-39 µm long, c = 40-51, c' = 1.1-1.3) with finely rounded terminus and variably re-curved dorsad, male tail conical (27-36 µm, c = 39-59, c' = 0.9-1.2), ventrally straight and dorsally convex, spicules 48-54 µm long, and 7-9 irregularly spaced ventromedian supplements lacking hiatus. The analyses of the D2-D3 expansion segments of 28S rRNA (LSU) gene sequences of the two new species confirmed the monophyly of the genus, based upon currently available data, showing a close relationship between the genera Aporcelinus and Makatinus, and justified the placement of Aporcelaimellus, Makatinus and Aporcelinus under the subfamily Aporcelaimellinae.

Eudorylaimus kahaqensis sp. n. (Nematoda: Dorylaimida: Qudsianematidae), an interesting new species from Iran.

A new species of the genus Eudorylaimus is described from Kahaq region, Maragheh, East Azarbaijan province in Iran. Eudorylaimus kahaqensis sp. n. is characterized by its 1.40-1.75 mm long body, lip region nearly continuous and 17-21 µm wide and bearing a weakly sclerotized but distinct cephalic framework, cheilostom broad and with convex walls, odontostyle 21-23 µm long with aperture occupying 33-44% of its length, presence of a dorsal coelomocyte a short distance behind the nerve ring, neck 347-397 µm long, DN rather posterior (66-70%), pharyngeal expansion 162-205 µm or occupying 45-53% of total neck length, presence a dorsal cell mass at level of pharyngo-intestinal junction, V = 48-52, caudal region conical elongate (50-73 µm, c = 24-30, c' = 1.9-2.6 in females; 45-68 µm, c = 22-32, c' = 1.7-2.3 in males) and regularly curved ventrad with large hyaline portion, spicules 48-55 µm long and 7-9 irregularly spaced ventromedian supplements lacking hiatus.

Morphological and molecular characterization of Tarantobelus arachnicida gen. n., sp. n. (Nematoda, Rhabditida, Brevibuccidae), a parasitic nematode of tarantulas.

A new genus and new species, Tarantobelus arachnicida, was found in the oral opening of tarantula spiders bred in captivity in Poland. The new species is characterized by having a small body (0.77-0.95 mm long in females and 0.66-0.84 mm in males), cuticle poorly annulated by transverse incisures, lateral field inconspicuous, lips separated with small cuticular flaps topping each lip, stoma panagrolaimoid with gymnostom well developed with robust and refringent rhabdia, pharynx panagrolaimoid with isthmus slightly longer than the basal bulb, intestine with cardiac (anterior) and rectal (posterior) areas with narrower walls. Mature females with intestinal cells including needle crystal packs, excretory pore at isthmus level, female reproductive system panagrolaimoid with post-vulval sac 0.4-0.8 times the length of the corresponding body diameter and having very thick walls, vulva very prominent, female rectum 0.8-1.3 times the length of the anal body diameter, female tail conical with acute tip with phasmids at 58-62% of its length. Male tail conical with long and thin mucro, spicules ventrad bent having rounded manubrium and thick gubernaculum. Description, measurements and illustrations of the new species are provided. Molecular analyses show its relationship with Brevibucca and Cuticonema. On the other hand, Medibulla and its corresponding subfamily Medibullinae, previously in Osstellidae, are transferred to Panagrolaimidae, being Shahnematinae, the junior synonym of Medibullinae. Indocephalobus, recently proposed and located in the family Panagrolaimidae, is considered a junior synonym of Diplogastrellus (Diplogasteromorpha), and its only species, I. zebrae, is considered a junior synonym of D. gracilis. In addition, a key to identification of panagrolaimoid genera is included.

Molecular and morphological characterization of Belondira coomansi n. sp. (Nematoda: Dorylaimida, Belondiridae) from Iran.

A new species belonging to the genus Belondira is described from natural areas in Iran. Belondira coomansi n. sp. is characterized by its general size, the dimensions and appearance of its lip region, presence of distinct labial and post-labial sclerotization, the length of the odontostyle and its inconspicuous lumen and aperture, the length of the neck and its pharyngeal expansion, the reduction of the female anterior genital branch to a simple uterine sac, a very short posterior uterus, the anterior position of the vulva, the length and shape of the caudal region with distinctly thick cuticle at its tip, the length of the spicules, and the presence of only one pair of ventromedian supplements. The new species is close to Belondira brevibulba, B. sacchari, B. tenuidens and B. thornei, and it is compared to them. Molecular characterization (D2-D3 expansion segments of the rRNA large subunit) of the new species is also provided, representing only the second species of this genus for which any DNA sequence data are available.

Re-description of three species of the genus Sectonema Thorne, 1930 (Nematoda: Dorylaimida: Aporcelaimidae) originally studied by E. Altherr.

Three species of the genus Sectonema, namely S. demani, S. heynsi and S. macrospiculum, originally described by E. Altherr, are re-described on the basis of type material. Detailed descriptions, morphometrics and illustrations, including line drawings and/or LM pictures, diagnoses and remarks about their identity and later reports are provided for each species. Sectonema demani is characterized by its 6.78-7.24 mm long body, lip region 27-28 µm broad, mural tooth 19-20 µm long at its ventral side, pharyngeal expansion 834-875 µm long or 68-69% of total neck length, uterus a simple tube-like structure 2.1-2.2 times the corresponding body diameter, V = 49-52, tail short and rounded conoid (51-55 µm, c = 123-143, c' = 0.7-0.8), and male unknown. Sectonema heynsi is distinguished by its body 6.45 mm long, lip region 28 µm broad, circumoral area bearing cilia- or seta-like structures, mural tooth-like structure 20 µm long, pharyngeal expansion 856 µm long or 68% of total neck length, uterus a tube-like structure ?1.7 times the corresponding body diameter, V = 50, tail short and rounded to conoid (54 µm, c = 120, c' = 0.7), and male unknown. And S. macrospiculum is characterized by its 4.07-5.06 mm long body, lip region 27-28 µm broad, ventral side of the odontostyle 15 µm long, pharyngeal expansion 555-640 µm long or 67-68% of total neck length, uterus a simple tube-like structure 1.9-2.1 times the corresponding body diameter, V = 53, female tail short and convex conoid with rounded terminus (62 µm, c = 82, c' = 0.7), male tail more conoid than that of female and with the ventral side visibly more straight (58 µm, c = 71, c' = 0.8), spicules 107 µm long, and eight irregularly spaced ventromedian supplements bearing hiatus.

Metaxonchium persicum sp. n. from Iran (Nematoda, Dorylaimida, Belondiridae), with an updated taxonomy of the genus.

A new species of the genus Metaxonchium is described from natural habitats in Iran. The new species is characterized by having body length of 2.46-3.12 mm, lip region offset by constriction and 8-11 µm wide, odontostyle fusiform and 10-12 µm long, neck 773-1150 µm long, anterior portion of pharynx bearing a spindle-shaped thickening with valve-like structures inside, both parts of the pharynx separated by a short isthmus-like narrowing, pharyngeal expansion 531-825 µm long and occupying up to three-fourths of total neck length, female genital system monodelphic-opisthodelphic, anterior genital branch reduced to a large uterine sac and a small terminal mass, posterior uterus long and tripartite with an intermediate region bearing apophyses, V = 53-57, caudal region conoid with broadly rounded terminus (24-35 µm, c = 79-105, c' = 0.6-0.9), spicules 92-103 µm long and 7-10 spaced ventromedian supplements, at least two of them within the range of spicules. The taxonomy of the genus Metaxonchium is updated, including a list of its species, a key to their identification and a compendium of their morphometrics. Four species are transferred from Axonchium to Metaxonchium: M. coxi, M. japonicum, M. mizukuboi and M. zealandicum.

Nematodes of the Order Rhabditida from Andalucía Oriental, Spain. The Genera Protorhabditis (Osche, 1952) Dougherty, 1953 and DiploscapterCobb, 1913, with Description of P. spiculocrestata sp. n. and a Species Protorhabditis Key.

A new species of the genus Protorhabditis is described from natural areas in the SE Iberian Peninsula. Protorhabditis spiculocrestata sp. n. is distinguished by its body length 387-707 mum in females and 375-546 mum in males, lip very low and flattened, stoma 14-22 mum long, female tail conical-elongate (48-100 mum, c = 6.4-8.3, c' = 4.8-7.5), phasmid near anus, male tail conical (20-27 mum, c = 18.3-22.3, c' = 1.4-1.5), bursa peloderan closed anteriorly and bears eight papillae (1+2+1+1+3), spicules 23-26 mum long, and gubernaculum 10-16 mum long. Diploscapter coronatus is also presented. Description, measurements and illustrations, including SEM photographs, are provided. A key to species of Protorhabditis is also given as well a compendium of their measurements.

Description and SEM Observations of Stegelletina coprophila sp.n. (Nematoda: Rhabditida) from Caves of Andalucía Oriental, Spain.

A new species of the genus Stegelletina is described from caves of Andalucía Oriental (SE Iberian Peninsula). Stegelletina coprophila sp. n. is characterized by its body 386 to 536 mum long in females and 391 and 521 mum in males, lateral field with three incisures, lips bearing four tines, labial probolae 4 to 6 mum long and bifurcate, pharyngeal corpus 1.5 to 2.9 times isthmus length, spermatheca 18 to 43 mum long, postvulvar sac 0.5 to 1.6 times the corresponding body diameter long, female tail conical (24-34 mum, c = 14.2-17.2, c' = 1.7-2.3), male tail conical (26-35 mum, c = 12.1-17.1, c' = 1.4-1.8), spicules 20 to 25 mum long, and gubernaculum 10 to 13 mum long. Descriptions, measurements and illustrations, including SEM photographs, are provided for the species.

Spatial distribution of dorylaimid and mononchid nematodes from the southeast iberian peninsula: environmental characterization of chorotypes.

The aim of this study was to determine the incidence of 18 environmental variables in the spatial distribution of 30 chorotypes (species groups with significantly similar distribution patterns) of dorylaimid and mononchid nematodes by means of logistic regression in a natural area in the southeastern Iberian Peninsula. Six variables (elevation, color chroma, clay content, nitrogen content, CaCO, and plant community associated) were the most important environmental factors that helped explain the distribution of chorotypes. The distribution of most chorotypes was characterized by some (one to three) environmental variables; only two chorotypes were characterized by five or more variables, and four have not been characterized.