The invasion of Tunisia by the red palm weevil, Rhynchophorus ferrugineus Oliver (Coleoptera: Curculionidae): crossing an ocean or crossing a sea?

Abstract

The red palm weevil, Rhynchophorus ferrugineus, is a highly invasive, injurious pest of palms, originating from South- and Southeast Asia. Following its accidental introduction into the Middle East, this species rapidly extended its range to include much of the Persian Gulf, Mediterranean Basin, and North Africa. This range expansion has seriously impacted the date palm industries of many countries, and led to the death of thousands of iconic ornamental palms, particularly around the Mediterranean. Rhynchophorus ferrugineus has never been recorded from the USA, but a morphologically indistinguishable congener, R. vulneratus, was detected in California, USA, in 2010 (and later eradicated). In December 2011, despite strict phytosanitary regulations, an invasive population of palm weevils was for the first time detected in ornamental palms in Tunis, Tunisia. The specific identity of the weevil population in Tunisia has not been confirmed, and this has fueled consternation over its potential origin. It has been reported that the Tunis invasion resulted from the illegal importation of infested palms from the USA. However, contradictory claims from government employees, suggest that infested palms were imported from Italy. We compared the mitochondrial haplotypes of specimens collected at multiple sites around Tunis, and compared them to haplotypes from globally distributed invasive and native populations of R. ferrugineus and R. vulneratus. We conclusively show that the Tunisian weevils are R. ferrugineus, refuting the claim that the invasion occurred as a result of importing infested palms from the USA. Moreover, we characterize the Tunisian population as having the same fixed mitochondrial haplotype ubiquitous in invasive populations throughout the neighboring regions, providing support for claims that the invasion of Tunisia by RPW occurred as a result of importing infested palms from Europe.

Key Words: invasive pest; red palm weevil; Rhynchophorus vulneratus; phytosanitary regulation; mitochondrial DNA; COI

Resumen
El gorgojo rojo de la palma, Rhynchophorus ferrugineus (Olivier) (Coleoptera: Dryophthoridae), es una plaga invasiva y nociva de palmas que ha extendido su área de distribución nativa en Asia a África, Medio Oriente y la Cuenca Mediterránea. En 2010, se detectó una especie, R. vulneratus (Panzer), morfológicamente indistinguible y luego erradicada de California, EE.UU. En 2011, se detectó una población de gorgojos de palma en palmas ornamentales en Tunis, Túnez. La incertidumbre sobre la identidad de la población de gorgojos en Túnez llevó a la especulación conflictiva de que la fuente de la población emergieron de palmas infestadas e importadas ilegalmente de los EEUU o de Italia. Se compararon los haplotipos mitocondriales de especímenes recolectados en múltiples sitios alrededor de Túnez con haplotipos de poblaciones globales de R. ferrugineus y R. vulneratus, lo que confirma que las poblaciones tunecinas eran de R. ferrugineus. Por otra parte, las poblaciones tunecinas tenían el mismo haplotipo mitocondrial fijo ubicuo en poblaciones invasoras en toda la Cuenca Mediterránea, y concluimos que las poblaciones tunecinas probablemente se originaron de palmas importadas de Europa y no de palmeras importadas de los Estados Unidos.

Palabras Clave: plaga invasiva; gorgojo rojo de la palma; Rhynchophorus vulneratus; regulación fitosanitaria; ADN mitocondrial; COI

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