The survival, development, and reproduction of Gonipterus platensis (Coleoptera: Curculionidae) on the main Eucalyptus (Myrtaceae) genotypes planted in Brazil

Observations on iNaturalist reveal the establishment of non-native Eucalyptus weevil Gonipterus platensis (Coleoptera: Curculionidae) in Tamil Nadu, India

We report the establishment of the invasive eucalyptus weevil Gonipterus platensis in the high elevation Nilgiri Plateau in the state of Tamil Nadu, India. Its presence was first brought to light by observations uploaded on iNaturalist, a citizen science platform, from Eucalyptus globulus plantations. Specimens collected from the plantations were examined morphologically and dissected to reveal the diagnostic characters of G. platensis. DNA sequences of the cytochrome c oxidase gene (COI) amplified from Indian specimens were 0.3% different from G. platensis sequences from Tasmanian populations and over 4% different from any other Gonipterus species for which DNA data are available. Sequence data from 6 invasive populations of G. platensis indicates multiple, independent invasions from a Tasmanian source population to different parts of the world. The collection of specimens, including larvae, over multiple years indicates that the population in the Nilgiris is persistent, with the earliest evidence for its presence in the region being March 2019. We recommend further monitoring and assessment of population growth and spread of Gonipterus platensis to minimize the economic impact of this potentially important pest of Eucalyptus in India. Citizen science played a critical role in this discovery, and we recommend that subject experts engage with nature enthusiasts on platforms like iNaturalist so that the wide reach of public participation is harnessed to effectively monitor biodiversity.

Polyandry contributes to Gonipterus platensis (Coleoptera: Curculionidae) rearing

Background

Gonipterus platensis Marelli, 1926 (Coleoptera: Curculionidae) is one of the main defoliating beetles in Eucalyptus plantations. Biological control with egg parasitoids is one of the main control strategies for this pest and a constant supply of fresh host eggs is required to rear the parasitoids. Polyandry can influence Gonipterus oviposition by increasing female fecundity and fertility; however, the high density of individuals in laboratory colonies can lead to male harassment, resulting in lower reproduction rate. The aim of this study was to measure the effects of monoandry and polyandry on the reproduction of G. platensis and the effects of male harassment on laboratory rearing conditions.

Methods

Reproductive parameters were compared between three treatments: monoandry, where the female was allowed to mate daily with the same male; no choice polyandry, where the female was allowed to mate daily with a different male; and polyandry with choice, where the female was allowed to mate daily, but with a choice between five different males. Another experiment varying the density of males was conducted to evaluate the effect of male harassment.

Results

Polyandry with choice resulted in the longest period of oviposition, highest fecundity and highest number of eggs per egg capsules when compared to monoandrous females. No negative effect related to male harassment in the laboratory, such as decreased fertility, fecundity, or number of eggs per egg capsule, was detected.

Conclusion

Polyandry contributes to mass rearing as it increases fecundity and oviposition period on females and there is no evidence of male harassment on G. platensis.

Presence of the Eucalyptus snout beetle in Ecuador and potential invasion risk in South America

Eucalyptus snout beetles are a complex of at least eight cryptic species (Curculionidae: Gonipterus scutellatus complex), native to mainland Australia and Tasmania, that defoliate Eucalyptus trees and are considered important pests. Since the 19th century, three species of the complex have been introduced to other continents. Here, we document the presence of Eucalyptus snout beetles in Ecuador. We used DNA data for species identification and unambiguously demonstrated that the Ecuadorian specimens belong to the species Gonipterus platensis, which has low genetic diversity compared with other species in the complex. We analyzed G. platensis' potential distribution in South America with ecological niche models and found several areas of high to intermediate climatic suitability, even in countries where the pest has not been registered, like Peru and Bolivia. Accurate identification of species in the G. scutellatus complex and understanding of their potential distribution are essential tools for improved management and prevention tactics.