Local dispersal pathways during the invasion of the cactus moth, Cactoblastis cactorum, within North America and the Caribbean

Guadalupe Andraca-Gómez,Eric Lombaert,César A Domínguez,Karina Boege,Rubén Pérez-Ishiwara,Juan Fornoni,Mariano Ordano

doi:10.1038/s41598-020-66864-3

Abstract

Cactoblastis cactorum, a species of moth native to Argentina, feeds on several prickly pear cactus species (Opuntia) and has been successfully used as a biological control of invading Opuntia species in Australia, South Africa and native ruderal Opuntia species in some Caribbean islands. Since its introduction to the Caribbean its spread was uncontrolled, invading successfully Florida, Texas and Louisiana. Despite this long history of invasion, we are still far from understanding the factors determining the patterns of invasion of Cactoblastis in North America. Here, we explored three non-mutually exclusive explanations: a) a stepping stone model of colonization, b) long distance colonization due to hurricanes, and/or c) hitchhiking through previously reported commercial routes. Genetic diversity, genetic structure and the patterns of migration among populations were obtained by analyzing 10 nuclear microsatellite loci. Results revealed the presence of genetic structure among populations of C. cactorum in the invaded region and suggest that both marine commercial trade between the Caribbean islands and continental USA, as well as recurrent transport by hurricanes, explain the observed patterns of colonization. Provided that sanitary regulations avoiding human-mediated dispersal are enforced, hurricanes probably represent the most important agent of dispersal and future invasion to continental areas.

Highlights

During the last decades, biological invasion studies have strongly benefited from the use of neutral molecular markers to disentangle routes of invasion[1,2,3]
The threat for North American deserts is that they have the highest diversity of Opuntia cacti species, which may suffer from this oligophagous moth[18]
Since moths were taken from Argentina to Australia, and to South Africa, the analysis considered a “ghost” population representing a non-sampled population that may represent this step

Summary

Introduction

Biological invasion studies have strongly benefited from the use of neutral molecular markers to disentangle routes of invasion[1,2,3] This has helped to identify source populations, frequency of invasion events, and the geographical patterns and demographic consequences of invasive species spread[4,5]. Given the risk of further spread to continental areas and the ecological, social and economic associated costs, the present study examined possible routes of local dispersal in the Caribbean and Florida to better understand the factors that may favor additional introductions of this invasive species to the continent. This approach will allow us to add a new piece of evidence to determine whether dispersal through trade, climatic events (hurricanes) or both, better account for the current genetic structure of C. cactorum in North America

Objectives

Methods

Results

Conclusion