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

Abstract

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.

Keywords: Eucalyptus globulus; Nilgiris; biosystematics; citizen science; invasive; molecular identification.

Fig. 1.

Gonipterus platensis feeding on Eucalyptus globulus in the Ketti Valley, Nilgiris district, Tamil Nadu, India.

Fig. 2.

Larvae of Gonipterus platensis from Ketti Valley, Nilgiris district, Tamil Nadu, India.

Fig. 3.

Habitus and genitalia of Gonipterus platensis from Ketti Valley, Nilgiris district, Tamil Nadu, India. A) Dorsal habitus of male, B) Ventral habitus of male, C) Dorsal habitus of female, D) Penis, ventral view, E) Penis, lateral view of right side with endophallus invaginated, F) Penis, dorsal view; cs = crescent-shaped sclerites, as = apical sclerites. G) Hemisternites VIII and spiculum gastrale, ventral view; s8 = hemisternites VIII, sg = spiculum gastrale.

Fig. 4.

Photographs of Gonipterus platensis penis showing details of the endophallus. A) Penis, lateral view of left side with endophallus everted. B) Detail of apical sclerites, dorsal view. C) Detail of apical sclerites, ventral view. D) Detail of crescent-shaped sclerites, lateral view; acs = accessory sclerites; bp = basal piece, lar = left apical rod, mar = medial apical rod, mp = membranous pouch, pt = teeth on proximal margin of basal piece, rar = right apical rod, rt = teeth on dorsal surface of left apical rod.

Fig. 5.

Neighbour-joining tree of the p-distances between DNA sequences of the 3’ end of the cytochrome c oxidase mitochondrial gene region. Gonipterus platensis is shown in a single clade indicating their provenance.

Fig. 6.

Randomized minimum spanning tree of the haplotypes of the 3’ end of the cytochrome c oxidase mitochondrial gene region of Gonipterus platensis. Size of the circles indicates the number of specimens sharing that haplotype. Colours show the locality where specimens were collected. Tick marks on branches show the number of substitutions separating the haplotypes.

Fig. 7.

Map of northwestern Tamil Nadu, showing the locations where Gonipterus platensis has been found (large blue points, data in Table 1). The inset map shows the location in India. Map created using QGIS, using geographic data provided by OpenStreetMap (https://www.openstreetmap.org).