Abstract
A survey of nematodes associated with the red palm weevil Rhynchophorus ferrugineus was conducted in southern Italy in 2015 and 2016 in order to create a species inventory and obtain data about nematode biodiversity. A total of 70 insect samples (pupae and adults) were collected from infested Phoenix canariensis, Phoenix dactylifera, and Chamaerops humilis palms in three Italian Regions: sampling took place at 11 locations in Apulia, 1 in Basilicata, and 1 in Sardinia regions. Individual insects were dissected to determine nematode presence, and different nematode species were also recovered from red palm weevil cocoons collected at the sites in Apulia. Individual nematodes were molecularly identified by sequencing the ITS, D2‐D3 expansion domains of the 28SrRNA gene and the mitochondrial COI and inferring the phylogenetic relationships. The insect‐associated nematofauna identified belonged to the families Rhabditidae, Cephalobidae, and Diplogastridae. Just two nematode species, Teratorhabditis synpapillata and Mononchoides macrospiculum, were always found in association with adult insects and cocoons taken from all sampling sites. This paper reports on the biodiversity of the nematodes associated with R. ferrugineus and on current knowledge of the specific habitat of specialized and divergent entomophilic nematodes.
Highlights
The red palm weevil (RPW) Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) is considered the most damaging pest of several palm species of the family Arecaceae worldwide, especially in the Mediterranean area (EPPO, 2008a; Giblin-Davis, Kanzaki, & Davies, 2013; Mazza et al, 2014) and is reported to infest 19 palm species
Two nematode species phoretically associated in the hemocoel and external surface of all RPW samples from P. canariensis and P. dactylifera were molecularly identified as T. synpapillata and M. macrospiculum by their 100% sequence identity with those in the database (Kanzaki et al, 2008; Troccoli et al, 2015), while only M. macrospiculum was detected in C. humilis
The ITS tree confirmed the clustering of O. tipulae (100% support) with the corresponding O. tipulae database sequences from different geographical origins, in Italy, South America and Europe (Figure 2), and of A. nanus (100% support) with the corresponding database sequences (Figure 3a), while the Acrostichus sp. sequences obtained in this study showed sister relationships with A. palmarum and A. rhynchophori sequences (Figure 3b)
Summary
The red palm weevil (RPW) Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) is considered the most damaging pest of several palm species of the family Arecaceae worldwide, especially in the Mediterranean area (EPPO, 2008a; Giblin-Davis, Kanzaki, & Davies, 2013; Mazza et al, 2014) and is reported to infest 19 palm species. Few studies have been conducted on nematodes associated with R. ferrugineus to evaluate the possibility that all Rhynchophorus species can act as vectors of pathogenic nematodes, introducing them to new areas and new host plants. Our study used sequencing and phylogenetic approaches to investigate the biodiversity of nematodes associated with R. ferrugineus samples collected in southern Italy. The main goals of the present study were as follows: (a) to collect RPW adults, pupae, and cocoons from different sampling sites in southern Italy; (b) to use sequencing and phylogenetic profiles to identify all nematodes associated with RPW; (c) to compare nematode associates among different geographical sites and palm hosts; and (d) to understand the evolution and phylogeny of nematode species and of their host
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