Multidisciplinary fingerprints: forensic reconstruction of an insect reinvasion

Abstract

An unexpected outbreak of boll weevils, Anthonomus grandis , an insect pest of cotton, across the Southern Rolling Plains (SRP) eradication zone of west-central Texas, USA, was detected soon after passage of Tropical Storm Erin through the Winter Garden district to the south on 16 August 2007. The synchrony and broad geographic distribution of the captured weevils suggest that long-distance dispersal was responsible for the reinvasion. We integrated three types of assessment to reconstruct the geographic origin of the immigrants: (i) DNA fingerprinting; (ii) pollen fingerprinting; and (iii) atmospheric trajectory analysis. We hypothesized the boll weevils originated in the Southern Blacklands zone near Cameron, or in the Winter Garden district near Uvalde, the nearest regions with substantial populations. Genetic tests broadly agree that the immigrants originated southeast of the SRP zone, probably in regions represented by Uvalde or Weslaco. The SRP pollen profile from weevils matched that of Uvalde better than that of Cameron. Wind trajectories supported daily wind-aided dispersal of weevils from the Uvalde region to the SRP from 17 to 24 August, but failed to support migration from the Cameron region. Taken together the forensic evidence strongly implicates the Winter Garden district near Uvalde as the source of reinvading boll weevils.

Population Structure and Genetic Diversity of the Boll Weevil (Coleoptera: Curculionidae) onGossypiumin North America

“…The appropriate response by an eradication program depends in part on whether the captured weevils are from local populations infesting commercial cotton or long-distance migrants from cultivated or wild hosts (Kim et al 2010). Diagnostic markers to indicate source areas would be an important tool in helping management ofÞcials determine appropriate control tactics (Roehrdanz 2001).…”

Forensic pollen geolocation techniques used to identify the origin of boll weevil re-infestation

“…Increasing the amount of the SRP residue examined increased the number of pollen grains and taxa encountered. The number of grains increased from 158 to 192 and the number of taxa from 33 to 39 (Jones et al, 2009;Kim et al, 2010).…”

“…The glycerine/stain drop was covered with a glass cover slip and the edges were sealed by painting a coat of fingernail polish along the edges. After the initial report on these weevils (Jones et al, 2009;Kim et al, 2010), additional slides of the pollen residue were made and examined of the SRP weevils to enhance their pollen-print. Micrographs of the Cameron and Uvalde boll weevils were re-examined and unknown taxa identified.…”

“…The initial reports on this event used DNA, meteorological and palynological techniques to determine the possible origin of the SRP weevils (Jones et al, 2009;Kim et al, 2010). The purpose of this research was to examine additional pollen residue from the collected weevils, identify as many of the unknown taxa as possible, and examine the palynological challenges of this type of research.…”

“…This eradication zone had been essentially weevil-free since 2003. In order to mitigate this unexpected re-invasion, expenses of more than one million US dollars (USD) were incurred to increase the number of traps and insecticide applications during the fall of 2007 (Jones et al, 2009;Kim et al, 2010). The synchrony and broad distribution of captured weevils along the southern perimeter of the SRP eradication zone suggest long-distance dispersal was responsible for the re-invasion.…”