Population genetic structure of Megamelus scutellaris (Hemiptera: Delphacidae) and its implications for the biological control of water hyacinth (Pontederia crassipes)

Authors: SALINAS, NICOLA - Fuedei; Smith, Melissa; COETZEE, JULIE - Rhodes University; HILL, MARTIN - Rhodes University; BRENTASSI, MARIA - Fuedei; SOSA, ALEJANDRO - Fuedei

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/15/2023
Publication Date: 5/10/2023
Citation: Salinas, N., Smith, M., Coetzee, J., Hill, M., Brentassi, M., Sosa, A. 2023. Population genetic structure of Megamelus scutellaris (Hemiptera: Delphacidae) and its implications for the biological control of water hyacinth (Pontederia crassipes). Meeting Abstract.

Interpretive Summary: Lygodium microphyllum is an invasive vining fern that colonizes natural areas throughout south and central Florida. The eriophyid mite, Floracarus perrepae is the most widely distributed herbivore on L. microphyllum in the native range. Based on initial genetic surveys, the point of origin for the Florida populations was far northern Queensland, Australia and mites were collected, tested, and released from there. Following their release, the mites established in many places in Florida, but failed to establish on approximately half of the populations, with concentrations of gall-resistant material on the west coast. Utilizing Rad-seq, we found two distinct nuclear signatures with some small indication of admixture between the populations. This indicates that there were likely two separate introductions of L. microphyllum and accurately identifying the second source population and matching mite populations from there may yield higher rates of colonization.

Technical Abstract: Understanding the invasion history of introduced weeds is an important step when developing sustainable management strategies. This information is particularly crucial when selecting biological control agents, as plants introduced from different regions may respond differently to natural enemies. In this study, we assessed the genetic structure of invasive Lygodium microphyllum, a weed that causes significant ecological damage in Florida, USA. A previously released biological control agent – the leaf-galling mite Floracarus perrepae – causes noticeable damage to some populations but not others, suggesting there may be a mite-resistant L. microphyllum lineage in Florida. To test this hypothesis, we used a genotyping-by-sequencing approach to assess population structuring across the introduced range of L. microphyllum. Our genomic analyses indicate that two distinct L. microphyllum lineages were likely introduced to Florida, with these two lineages differing in their susceptibility to galling by Floracarus perrepae. These two lineages had different but overlapping distributions – with evidence of admixture between these lineages at some sites – suggesting each lineage was introduced to Florida independently. Additional research is needed to better understand the susceptibility of admixed lineages to these mites, and to identify mite lineages in the native range that will damage mite-resistant Florida L. microphyllum. In addition to having important practical implications for the management of L. microphyllum, our results highlight the value of characterising and monitoring the genetic structure of introduced invasive plants, as this approach can help identify discrete invasive lineages which may differ in their susceptibility to biological control agents and show how the susceptibility of populations may change over time.