Molecular data reveals California as the potential source of an invasive leafhopper species, Macrosteles sp. nr. severini, transmitting the aster yellows phytoplasma in Hawaii

A species of aster leafhopper (Macrosteles sp.) became established in 2001 on Oahu, Hawaii, and through the transmission of the aster yellows phytoplasma, caused devastating losses to the island's watercress industry. DNA sequence data were analysed from two mitochondrial genes [cytochrome oxidase subunit 1(CO1) and nicotinamide adenine dinucleotide 1 (NADH1)] and one nuclear gene (wingless, Wg) (combined total of 1874 bp) to reconstruct phylogenetic relationships between putative US mainland source populations of aster leafhoppers and those introduced to Hawaii. These data were applied to elucidate the origin(s) and identity of Hawaiian infestations and the amount of genetic diversity within introduced invasive populations. Both phylogenetic search criteria (Bayesian and maximum likelihood models) converged onto similar tree topologies for all three gene regions and suggested that Hawaii infestations represent a single undescribed leafhopper species unrelated to the common aster leafhopper, Macrosteles quadrilineatus. An exact haplotype match was found from a specimen intercepted from watercress shipped to Hawaii from Los Angeles, California, suggesting this region as the potential source for Hawaiian infestations. Two mitochondrial haplotypes were identified in Hawaii suggesting two or perhaps just a single introduction of more than one female.