Phylogenetic position of Ptychaphelenchus eucalypticola Hodda, 2009 within the Aphelenchoidoidea Skarbilovich, 1947 (Siddiqi, 1980) inferred from partial 18S and 28S rDNA gene sequences

At the time of description, the morphology of Ptychaphelenchus eucalypticola Hodda, 2009 indicated it could be assigned to either the Aphelenchoididae Skarbilovich, 1947 (Paramonov, 1953) or the Parasitaphelenchidae Ruehm, 1956 (Siddiqi, 1980) within the Aphelenchoidoidea Skarbilovich, 1947 (Siddiqi, 1980). Although P. eucalypticola was, tentatively, and remains assigned to the Aphelenchoididae, its relationships with other aphelenchoids have not been reassessed, and no molecular data were previously available for this species. We re-collected P. eucalypticola from its type host and locality, Eucalyptus macrorhyncha F. Muell. ex Benth., from Mount Ainslie, ACT, Australia. We performed Bayesian inference and maximum likelihood analyses of a concatenated 18S + 28S rDNA gene sequence dataset to determine the position of P. eucalypticola within the Aphelenchoidoidea, followed by 18S and 28S single-gene analyses to further assess relationships between this species and an expanded set of close relatives. All analyses indicated P. eucalypticola is correctly assigned to the Aphelenchoididae, in a clade comprising all species of Ficophagus Davies & Bartholomaeus, 2015 and some species presently assigned to Aphelenchoides Fisher, 1894, sister to Martininema Davies & Bartholomaeus, 2015 and additional species of Aphelenchoides. Our 18S single-gene analyses did not resolve the position of P. eucalypticola relative to Aphelenchoides and Ficophagus; however, our 28S single-gene analyses indicated a sister relationship between P. eucalypticola and Ficophagus. This sister relationship is plausible as the former species shares many characteristics with species of the latter genus; however, there are sufficient morphological differences to consider P. eucalypticola as representative of a distinct lineage within the Aphelenchoidoidea.

Description of Ruehmaphelenchus kuroshioi n. sp. and R. interjectus n. sp. (Tylenchomorpha: Aphelenchoididae) isolated from ambrosia beetles, Euwallacea spp. (Scolytinae), from Japan

Two Ruehmaphelenchus species were isolated from the ambrosia beetles Euwallacea kuroshio and E. interjectus, collected from Okinawa and Kagoshima, Japan, respectively. Both nematodes were successfully cultured on a lawn of the grey mould Botrytis cinerea. Morphological observation and molecular characterisation revealed that both species are undescribed; therefore, the nematodes are described herein as R. kuroshioi n. sp. and R. interjectus n. sp. Phylogenetically, both species are closely related to R. formosanus, R. fujiensis, R. digitulus and R. asiaticus. Ruehmaphelenchus kuroshioi n. sp. is characterised by a conical male and female tail, which has a terminal projection (mucron), small male spicule with a weakly-developed triangular condylus, dorsal and ventral limbs that are connected to each other by three different tissues, and clearly separated distal pairs of genital papillae (P3 and P4). However, R. kuroshioi n. sp. can be distinguished from its close relatives by a combination of male and female tail characters and its distinctive phylogenetic status. Ruehmaphelenchus interjectus n. sp. is almost identical to R. formosanus, sharing characteristic lateral spikes of the spicule; they form a well-supported phylogenetic clade. However, R. interjectus n. sp. is distinguished from R. formosanus by morphometric values and ribosomal RNA, i.e., a 6-bp difference from the ca 1.7 kb molecular sequence of the 18S ribosomal RNA of R. formosanus, which warrants independent species status.

Description of Ruehmaphelenchus americanum n. sp. (Nematoda: Aphelenchoididae) found in Loblolly pine from the USA

Ruehmaphelenchus americanum n. sp., isolated from southern yellow pine (Pinus taedae L.) from the USA is described and figured. It is characterised by a relatively stout body (a = 30 for females and males), three lines in the lateral field, both oocytes and spermatocytes arranged in two rows, male spicules relatively small (14-18 μm) with weakly developed condylus and rostrum, short tail with a bluntly pointed tip, seven papilliform genital papillae present, female vulva positioned at ca 82% of body length, vulval lips slightly protruding, post-uterine branch extending two-thirds of vulva to anus distance, tail cylindrical, ca two anal body diam. long, terminus forming a spike-like projection or mucron, 7.6-12.2 μm long, with pointed tip. The new species can be separated from 11 known species (except R. thailandae) by male genital papillae arrangement (the second and third pair adjacent vs separated). Detailed phylogenetic analysis based on 18S and 28S D2-D3 region ribosomal RNA (rRNA) sequences has confirmed the status of this nematode as a new species.

Description of Ruehmaphelenchus quercophilus n. sp. (Nematoda: Aphelenchoididae) from dying oak, Quercus robur, in Poland

Ruehmaphelenchus quercophilus n. sp., isolated from a dying oak, Quercus robur, in the State Forests, Łopuchówko District, Poland, is described and figured. It is characterised by three lateral lines, relatively stout body, excretory pore posterior to nerve ring, five caudal papillae, spicules relatively small (12-14 μm) with weakly developed condylus and rostrum, bursa absent, vulva positioned at ca 78% of body length, vulval flap absent, post-uterine branch extending for slightly over half of vulva to anus distance, and conoid tail with a bend at the distal end forming a terminal projection 10-14 μm long. The new species is very similar to four other described species, namely R. formosanus, R. juliae, R. thailandae, and R. sirisus. Detailed phylogenetic analysis based on 18S, 28S D2-D3 and ITS sequences has confirmed the status of this nematode as a new species.

Description of Ruehmaphelenchus juliae n. sp. (Tylenchina: Aphelenchoididae) isolated from an ambrosia beetle, Xylosandrus crassiusculus (Motschulsky), from South Florida

During a survey of nematode associates of ambrosia beetles from dead and dying red bay and avocado trees affected by the laurel wilt epidemic in southern Florida, a Ruehmaphelenchus species was isolated from the non-native ambrosia beetle, Xylosandrus crassiusculus. The new species is characterised by its possession of an oral disc at the stoma opening, three lines in the lateral field, male spicule with clear dorsal and ventral limbs connected by elongated triangular cuticle, thin membrane-like tissue and cuticular bridge-like structure, conical tail with pointed tip of males and conical tail with digitate mucro of females. The new species is very similar to four previously described species: R. asiaticus, R. digitulus, R. thailandae and R. sirisus, and can be distinguished only by some minor morphological differences in male tail characters, i.e., spicule morphology, position of genital papillae and tail tip shape, and morphometric values. However, the new species is phylogenetically unique, i.e., it is the basal taxon of the Ruehmaphelenchus clade and close to Bursaphelenchus spp. Ruehmaphelenchus juliae n. sp. is therefore proposed based on its morphological diagnostic characters and molecular sequences of near-full-length of SSU, internal transcribed spacer region, D1, D2 and D3 expansion segments of LSU ribosomal RNA and partial mitochondrial COI genes.

New plant-parasitic nematode from the mostly mycophagous genus Bursaphelenchus discovered inside figs in Japan

A new nematode species, Bursaphelenchus sycophilus n. sp. is described. The species was found in syconia of a fig species, Ficus variegata during a field survey of fig-associated nematodes in Japan. Because it has a well-developed stylet and pharyngeal glands, the species is considered an obligate plant parasite, and is easily distinguished from all other fungal-feeding species in the genus based upon these characters. Although B. sycophilus n. sp. shares an important typological character, male spicule possessing a strongly recurved condylus, with the “B. eremus group” and the “B. leoni group” of the genus, it was inferred to be monophyletic with the “B. fungivorus group”. The uniquely shaped stylet and well-developed pharyngeal glands is reminiscent of the fig-floret parasitic but paraphyletic assemblage of “Schistonchus”. Thus, these morphological characters appear to be an extreme example of convergent evolution in the nematode family, Aphelenchoididae, inside figs. Other characters shared by the new species and its close relatives, i.e., lack of ventral P1 male genital papilla, female vulval flap, and papilla-shaped P4 genital papillae in males, corroborate the molecular phylogenetic inference. The unique biological character of obligate plant parasitism and highly derived appearance of the ingestive organs of Bursaphelenchus sycophilus n. sp. expands our knowledge of the potential morphological, physiological and developmental plasticity of the genus Bursaphelenchus.

Description of two Pseudaphelenchus species (Tylenchomorpha: Aphelenchoididae) associated with Asian termites and proposal of Tylaphelenchinae n. subfam

Two new Pseudaphelenchus species were discovered from subterranean and arboreal termites from the East Asian subtropics. Pseudaphelenchus sui n. sp. isolated from Coptotermes formosanus was collected from Miyako Isl., Okinawa, Japan, and P. scheffrahni n. sp. was isolated from Nasutitermes takasagoensis collected from the Kenting National Park in Taiwan. The two new species and P. vindai, previously described from Panamanian termites, are close to each other, and are not easily distinguished morphologically, i.e., these three are almost ‘cryptic species’. However, they can be distinguished based on minor morphological differences, including shape of male bursa (clearest in P. vindai, vague in P. sui n. sp. and intermediate in P. scheffrahni n. sp.), male tail tip (P. sui n. sp. often have a small mucron but the others do not), and in the character of the female tail (the two new species have stronger ventral curvature than P. vindai, and further, P. sui n. sp. has clear annulation at distal part, while the other species do not). Molecular phylogenetic analysis based upon near-full-length sequences of the small subunit of the ribosomal RNA gene suggested that Pseudaphelenchus and Tylaphelenchus form a strongly-supported clade at the base of the family Aphelenchoididae, and that Tylaphelenchus is included in Pseudaphelenchus as an inner clade. Therefore, based on their phylogenetic status and common morphological characters, e.g., small body and spherical median bulb, a subfamily, Tylaphelenchinae n. subfam. is proposed to embrace these two genera. In addition, Ruehmaphelenchus ipidicola n. comb. (= Tylaphelenchus ipidicola) is proposed.

Bursaphelenchus niphades n. sp. (Tylenchina: Aphelenchoididae) amensally associated with Niphades variegatus (Roelofs) (Coleoptera: Curculionidae)

A Bursaphelenchus species was isolated from a Japanese native wood-boring weevil, Niphades variegatus, and dead Pinaceae trees. The nematode is associated with the weevils as dauer (dispersal third stage) juveniles and the dauers enter the weevil tracheal system forming an abnormal expansion on the weevil trachea (atrium). Thus, the nematode is hypothesised to be an amensal/phoretic associate of the weevil because the abnormal expansion appeared to inhibit weevil respiration. The propagative stages of the nematode are associated with dead trees (wood and bark materials) and are thought to feed there on naturally propagated fungi. Morphologically, the new species is considered an undescribed species close to B. antoniae, B. chengi and B. hylobianum. Within these four species, the new species, which is described herein as B. niphades n. sp., is closest to B. chengi, i.e., the typological character of these two species are almost identical to each other and is distinguished by some minor characters (structure of the male P4 genital papillae and spicule length). The molecular phylogenetic analysis supported the morphological observations. Bursaphelenchus niphades n. sp. formed a well supported subclade with the four species and is intermediate between B. hylobianum and B. chengi; however, it is distinguished by the molecular sequences of some ribosomal RNA genes. Because three of these four species are associated with weevil species, the subclade is considered a ‘weevil-associated’ species group.

Bursaphelenchus penai n. sp. (Tylenchomorpha: Aphelenchoididae), a phoretic associate of ambrosia beetles (Coleoptera: Scolytinae) from avocado in Florida

During an experimental host-plant survey for the invasive redbay ambrosia beetle, Xyleborus glabratus, in Homestead, Florida, it and three native species of ambrosia beetle, Xyleborus affinis, X. volvulus and Xyleborinus gracilis were found to be associated with a Bursaphelenchus species. This nematode species, isolated from ambrosia beetles from the tribe Xyleborini, was cultured on Monilinia fructicola or Botryotinia fuckeliana for further study and was determined to be new to science and a putative sister species to B. kiyoharai because of two apomorphic characters in males, viz., possession of a tail spike vs the typical bursal flap, and the apparent absence of the P1 ventral single papilla, both typically plesiomorphic characters for the genus. Additionally, B. kiyoharai is associated with X. serriatus suggesting that the host and microbiome associations that are shared between these two species, both of which are carried by ambrosia beetles, may have ecological and biological significance in their evolution and lineage radiation. Molecular phylogenetic analyses of the near-full-length small subunit (SSU: 18S) and the D2/D3 expansion segments of the large subunit (LSU: 28S) confirmed that B. penai n. sp. is very closely related to B. kiyoharai which is a member of the B. fungivorus clade that includes B. thailandae and B. willibaldi. Bursaphelenchus penai n. sp. and B. kiyoharai both share very similar overall spicule morphology with the B. fungivorus clade. The new species is described and can be typologically differentiated from B. kiyoharai by the position of the hemizonid and excretory pore and its different geographical and host associations.

Bursaphelenchus posterovulvus sp. n. (Nematoda: Parasitaphelenchidae) in packaging wood from Singapore

Bursaphelenchus posterovulvussp. n., isolated in Ningbo, P.R. China, from non-coniferous packaging wood from Singapore is described. It is characterised by a slim body (a = 24-43), lip region strongly offset, stylet with prominent and strongly sclerotised basal swellings, lateral field with four lines, excretory pore located at level of median bulb, hemizonid 30-40 μm posterior to excretory pore, vulva at 82-86% of total body length, post-uterine branch extending forcatwo-thirds of vulva-anus distance, female tail conical and short (c′ = 2.3-3.0) with a pointed terminus, spicules short (11-16 μm) and slightly arcuate, rostrum blunt and relatively short, dorsal and ventral limbs conspicuous and their distal ends separated, three pairs of ventro-sublateral papillae and a single precloacal papilla. The new species is distinguished from otherBursaphelenchusspecies by morphology, ITS-RFLP patterns and phylogenetic analyses.