Citizen scientists add to understanding of harmful monarch butterfly parasite

Thanks to nearly 100 volunteers, University entomologists are rethinking how Ophryocystis elektroscirrha and wing deformity are connected.

Te Herenga Waka—Victoria University of Wellington researchers have thanked the nearly 100 volunteer citizen scientists around Aotearoa New Zealand who provided samples from monarch butterflies to help determine how many of the popular insects have been harmed by a potentially deadly parasite.

The only previous survey for the parasite Ophryocystis elektroscirrha (OE) in New Zealand sampled six butterflies, but the citizen scientists enabled Professor Phil Lester and Dr Mariana Bulgarella from the University’s Te Kura Mātauranga Koiora—School of Biological Sciences to look at more than 550.

As a result, the entomologists are rethinking how OE and wing deformity in the butterflies are connected.

OE can harm monarch butterflies in many ways, including their pre-adult survival, adult body mass, mating ability, fecundity, flight ability, and adult lifespan.

The citizen scientists, ranging in age from 4–86 years, responded during last year’s COVID-19 Alert Level 4 lockdown to a callout in media and elsewhere by Professor Lester and Dr Bulgarella.

Between mid-April and late-July, from Dunedin to Doubtless Bay in Northland, they used clear sticky tape to collect spores from the abdomens of the butterflies—a harmless process when following the researchers’ instructions—and also recorded their physical condition and sex.

Based on the citizen scientists’ contributions, Professor Lester and Dr Bulgarella have now published a research paper in the journal Ecological Entomology.

In it, they outline how they found wing deformities in the butterflies increased with lower temperatures, while the prevalence of OE decreased, with the parasite preferring higher temperatures. No OE were observed in the coldest locatation of Dunedin, but all samples were infected in the warmest one of Doubtless Bay. The prevalence of OE and wing deformities did not vary with the sex of the butterfly.

The researchers had expected wing deformities to increase with parasitism rates, as in international studies, but their findings did not show this.

By way of possible explanation, Professor Lester says, “We believe temperature affects both the parasite and the butterfly independently. Cold temperatures during development cause wing deformities in these butterflies, which is why you see more deformities the further south you go. The parasite also seems unable to tolerate cold conditions. In the warmth of Northland, it is abundant, but environments like Dunedin appear too cold for OE.”

As a result of their findings, Professor Lester and Dr Bulgarella suggest the butterflies may perform better at intermediate temperatures and conservation approaches may therefore need to be tailored regionally.

“These are important findings and they would not have been possible without so many New Zealanders volunteering to help us,” says Professor Lester. “This project emphasises the value of citizen scientists for researchers and we cannot thank those who took part enough. Because of you, we are a step further in our understanding of monarch butterflies and the threat OE poses to them.”

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