Invasive Plants Disrupt Butterfly Mating

Fischer’s Blue butterfly
Threatened Tongeia fischeri species on native Orostachys japonica (Japanese Dunce Cap) flower. 
 Photo Credit: Osaka Metropolitan University

Scientific Frontline: Extended "At a Glance" Summary: Impact of Non-Native Diet on Butterfly Reproduction

The Core Concept: Feeding on non-native, invasive plant species during the larval stage significantly alters the adult wing coloration of the near-threatened Fischer's Blue butterfly (Tongeia fischeri), negatively impacting its reproductive success.

Key Distinction/Mechanism: Although an invasive diet does not affect direct life-history traits like growth or pupal weight, it chemically alters the visual and ultraviolet reflectance of the butterfly's wings. The wings appear more grayish rather than yellowish, directly disrupting the visual signals necessary to attract mates.

Major Frameworks/Components:

• Comparative Dietary Rearing: Evaluating larval development and outcomes on the native host plant (Orostachys japonica) versus an invasive host plant (Sedum sarmentosum).
• Optical Reflectance Analysis: Utilizing visible-light and ultraviolet photography, alongside reflectance spectra, to quantify physiological discoloration in adult wings.
• Behavioral Ecology Metrics: Observing mate choice frequency in the wild to establish a direct link between physical discoloration and reproductive isolation.

Branch of Science: Entomology, Ecology, Conservation Biology, and Evolutionary Biology.

Future Application: The diagnostic methodologies used in this study can serve as a predictive model to identify hidden physiological disruptions in other herbivorous insects, informing advanced conservation protocols and invasive species management.

Why It Matters: The research reveals a critical, indirect threat posed by invasive flora; even when native insects adapt to consume invasive plants without immediate physical harm, the resulting physiological changes can disrupt vital reproductive behaviors and silently threaten long-term species survival.

Diet affects developmental differences.
Butterflies that fed on non-native plants experienced discoloration and less frequent selection for mating.
Graphic Credit: Osaka Metropolitan University

A colorful and diverse garden brings joy to any gardener, but the increased popularity of nonnative plants in place of native species has brought about unprecedented changes in local wildlife.

The Fischer’s Blue, Tongeia fischeri (T. fischeri), is a near-threatened butterfly species in Japan that has been reported to use both native and nonnative plant species as hosts. Wing coloration functions as an important visual signal in butterfly mating behavior and has been theorized to vary depending on the host plant species the insects feed on during the larval stage. However, this hypothesis had not been previously tested in this species.

Therefore, a research team led by Professor Norio Hirai at Osaka Metropolitan University’s Graduate School of Agriculture hypothesized that feeding on nonnative plants during the larval stage might influence adult wing coloration and, consequently, affect reproductive behavior. The team reared larvae of T. fischeri on the native host plant, Orostachys japonica, and an invasive plant species, Sedum sarmentosum, and then compared their life-history traits. However, no significant differences in life-history traits, such as oviposition preference, growth, or pupal weight, were observed.

The researchers then took visible-light and ultraviolet photographs of the undersides of adult wings and measured their reflectance spectra for comparative analysis. The visible-light images revealed that individuals reared on the native plant appeared more yellowish, whereas those reared on the invasive plant appeared more grayish. Ultraviolet images further indicated that individuals reared on the native plant exhibited lower ultraviolet reflectance. Measurements of wing reflectance spectra revealed patterns consistent with these findings.

Furthermore, when observing the mate-choice behavior of wild T. fischeri males, the researchers found that the males made significantly more contact with individuals reared on the native plant than with those reared on the invasive plant.

“This study provides a rare example in Japan demonstrating that even when invasive plants can be used as food, they may indirectly influence the reproductive process,” said Karen Hisai, the first author of the research. “As the number of invasive species continues to increase, similar effects may potentially occur in other butterfly species and insects.”

“These findings can serve as a model case that highlights the indirect threats posed by invasive plants to herbivorous insects,” Professor Hirai concluded. “We hope that this work will contribute to the conservation of other threatened species and to the efforts aimed at addressing the broader challenges associated with invasive species.”

Funding: This research was supported by Grants-in-Aid for Scientific Research (19H02979, 23H02238, and 24H00723) from the Japan Society for the Promotion of Science and the Environment Research and Technology Development Fund (JPMEERF23S12122) of the Environmental Restoration and Conservation Agency, provided by the Ministry of the Environment of Japan.

Published in journal: Basic and Applied Ecology

Title: Effects of alien host plant on wing coloration and mating behavior of an endangered butterfly

Authors: Karen Hisai, Masaya Yago, Shouhei Ueda, Tsuyoshi Takeuchi, Masahiro Suzuki, and Norio Hirai

Source/Credit: Osaka Metropolitan University

Edited by: Scientific Frontline

Reference Number: ent051926_01

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