Acrostichus palmarum n. sp., a cryptic species separated from A. rhynchophori by molecular sequences and hybridisation tests

Summary A new Acrostichus species is described based upon molecular sequence profiles and hybridisation testing. The new species, A. palmarum n. sp., had been previously described as local isolates (strains) of A. rhynchophori, i.e., an isolate recovered from Rhynchophorus cruentatus from South Florida (culture code RGD193) was designated as the type strain of A. rhynchophori, and other Central and South American strains (RGD194-196), recovered from R. palmarum were considered as conspecific regional isolates. However, additional sequencing of ribosomal DNA loci (near full-length of small subunit, full length of internal transcribed spacer and D2-D3 expansion segments of large subunit) and partial mitochondrial cytochrome oxidase subunit I gene and hybridisation testing suggested the independent species status of RGD194-196. Furthermore, two strains of A. palmarum n. sp., RGD194 and RGD195, showed partial reproductive isolation from each other, i.e., the fecundity of F1 progeny was obviously low, suggesting that geographical isolation within a widely-distributed species is occurring.

Nematodes associated with palm and sugarcane weevils in South Florida with a description of Acrostichus floridensis n. sp.

During a 2016 survey of the nematode associates of the native palmetto weevil,Rhynchophorus cruentatus, and the recently introduced West Indian sugarcane weevil,Metamasius hemipterus(Coleoptera: Curculionidae), from southern Florida, a new species ofAcrostichuswas cultured from a single dissectedR. cruentatusfrom Fort Pierce, FL, USA. Morphological and molecular studies showed that it was new to science and it is described herein asA. floridensisn. sp. The new species is characterised by its male tail characters, spicule morphology with rounded manubrium separated from other parts by clear constriction, smoothly ventrally curved blade, slightly dorsally recurved and pointed tip, more or less straight gubernaculum with widely rounded anterior end and a triangular (arrowhead-like) appendage at the distal tip, and the arrangement of male genital papillae, ⟨(v1, v2), v3 / v4, ad, ph, (v5, v6, v7, pd)⟩. In addition toA. floridensisn. sp. and the previously described nematode associates ofR. cruentatus,i.e.,A. rhynchophori,Teratorhabditis palmarumandMononchoidessp., we recovered a putative new species ofDemaniellaand a new association record withRhabditidoides humicolusandDiplogastrellus metamasiusin Homestead, FL. Dissections and subsequent culturing attempts withM. hemipterusrevealed the previously described nematode associates ofCaenorhabditis angariaandD. metamasiusas well as a new association withR. humicolusin Homestead, FL, USA.

Acrostichus rhynchophori n. sp. (Rhabditida: Diplogastridae): a phoretic associate of Rhynchophorus cruentatus Fabricius and R. palmarum L. (Coleoptera: Curculionidae) in the Americas

Acrostichus dauer larvae (JIII) were recovered during dissections of the palmetto weevil, Rhynchophorus cruentatus, from southern Florida, and the palm weevil, R. palmarum, from Colombia, Costa Rica and Trinidad. Based upon morphological and molecular studies, the four isolates are conspecific and are described herein as A. rhynchophori n. sp. Acrostichus rhynchophori n. sp. is characterised by narrow, flap-like dorsal tooth, female gonads not reflexed to the level of the vulva, male spicule and gubernaculum morphology, i.e., spicule with small and indistinct manubrium embedded in lamina/calomus complex, strong expansion just posterior to manubrium and smoothly curved and smoothly tapered lamina/calomus complex, and gubernaculum with claw-like anterior end in lateral view and three distal branches in ventral view. The new species is distinguished from A. superbus by morphology of the spicule and gubernaculum. Type specimens of four other Acrostichus species, originally described from bark beetles from North America, i.e., A. concolor, A. gubernatus, A. ponderosus and A. taedus, were re-examined and photo-documented.