Paternity Analyses for the Planning of SIT Projects against the Red Palm Weevil

Simple Summary The red palm weevil Rhynchophorus ferrugineus is an invasive pest insect that feeds on more than 20 species of palms, many of which are widely grown for food and ornamental use. Due to its vast spread and the huge economic damage this pest can cause, it is very important to find sustainable and effective eradication strategies. Sterile insect techniques are biological control approaches based on the release of mass-reared sterilized males that could improve the likelihood of successful pest control. However, for the successful implementation of these approaches, it is necessary to develop a deep understanding of the insect's mating system. For this purpose, we built a paternity assignment strategy based on previously developed microsatellite loci to help the future study of the reproductive mechanisms of this species in laboratory-controlled mating experiments. We evaluated the reliability of our genetic tool using a simulation approach that aimed to explore its resolution power in paternity tests, both in the laboratory and in nature. The red palm weevil Rhynchophorus ferrugineus is an invasive pest from southeastern Asia and Melanesia that has spread widely across the Middle East and the Mediterranean Basin over the last 30 years. Its endophagous larvae cause huge amounts of damage to several palm tree species from the Arecaceae family. Many of these palms are economically important for agricultural and ornamental purposes. Therefore, a lot of attention has recently been focused on studying this species with the aim of identifying sustainable and effective eradication strategies. Sterile insect techniques are biological control strategies that are currently being investigated for their potential to eradicate this pest in selected invasion areas. Mating system features (e.g., polyandry and related features) can affect the success and suitability of these approaches. The main goal of this research was to assess the performance of a previously developed microsatellite panel in terms of the paternity assignment of progeny from laboratory mating experiments. Using a simulation approach, we evaluated the reliability of the microsatellite markers in the paternity tests both in complex laboratory experiment scenarios and on the progeny of wild-caught gravid females to help future studies on the RPW mating system. As a case study of the simulation results, we performed two double-mating experiments, genotyped the progeny and estimated the P-2 values to compare to the expected progeny genotypes according to the crossing scheme of each experiment. The results of our simulations on laboratory experiments showed that it was possible to carry out paternity assignments for all progeny with reliable statistical confidence using our 13 microsatellites set. On the contrary the low genetic variability measured in red palm weevil populations in invaded areas made the resolution power of our loci too low to carry out paternity analyses on natural populations. Results of laboratory crossing were completely congruent with the expectations from the Mendelian laws.

Automated summary

The red palm weevil is an invasive pest that can cause significant economic damage to palm trees. In order to find effective eradication strategies, researchers developed a paternity assignment strategy using microsatellite markers to study the mating system of this insect. They evaluated the reliability of their genetic tool through simulation approaches and found that it was successful in laboratory experiments but not in natural populations.