A colorful and diverse garden brings joy to any gardener, but the increased popularity of non-native plants in place of native species has brought about unprecedented changes in the 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 non-native plant species as hosts. Wing coloration is known to function as an important visual signal in butterfly mating behavior and has been theorized to vary depending on the host plant species they fed on during the larval stage. However, this hypothesis had not been tested previously 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 non-native plants during the larval stage may 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, then compared traits related to their life-history characteristics. However, no significant differences in life-history traits, such as oviposition preference, growth, or pupal weight, were shown.
The researchers then took visible-light and ultraviolet photographs of the underside 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 showed that individuals reared on the native plant showed lower ultraviolet reflectance. Measurements of wing reflectance spectra showed patterns consistent with these findings.
Furthermore, when they observed the mate choice behavior of wild T. fischeri males, it was found that they 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 this study. "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."
The findings were published in Basic and Applied Ecology.
