Department of Plant Science, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand.
BMC Ecol Evol. 2024 Aug 30;24(1):115. doi: 10.1186/s12862-024-02301-7.
Rivea ornata, a rare species from the morning glory family, exhibits uncommon characteristics compared to other typical morning glories, including nocturnal flowers that fit the classic moth pollination syndrome. However, the accuracy of its predicted pollination syndrome and its mating system have never been assessed. Additionally, R. ornata flowers attract not only pollinators but also florivores, potentially reducing plant reproductive success. Therefore, this study examined two populations of R. ornata in Thailand and assessed traits related to pollinator attraction and reward, determined its mating system, identified floral visitors and effective pollinators, and investigated the effect of florivory on reproductive success.
Rivea ornata is highly fertile but self-incompatible and an obligate outcrosser, rendering it highly dependent on pollinators. Lepidopterans, particularly nocturnal hawk moths, were found to account for a significant proportion of all visits and were the sole effective pollinators of this plant species, in correspondence with its predicted pollination syndrome. Surprisingly, florivory did not significantly reduce reproductive success. This phenomenon may be explained by the strategies employed by R. ornata, which align with the optimal defense hypothesis and functional trade-offs. Specifically, R. ornata appears to invest resources in defending key floral structures while, simultaneously, guard ants are conspicuously absent from flowers, resulting in some florivore damage to non-vital floral organs but ensuring that pollinators are not deterred by ants and thus maintaining high pollinator visitation rates.
Our findings indicate that reproduction-related traits in R. ornata, including those involved in pollinator attraction and reward and florivore defense, are highly effective and work in concert to maximize plant reproductive success. Therefore, a main risk that R. ornata faces is the decline or disappearance of hawk moths and other lepidopterans given its extreme specialization and high dependence on pollinators, and conservation efforts should include habitat protection for both R. ornata and its pollinators.
茑萝，旋花科的珍稀物种，与其他典型的旋花科植物相比，具有独特的特征，包括具有典型的蛾类授粉综合征的夜间开花。然而，其预测的授粉综合征和交配系统的准确性从未被评估过。此外，R. ornata 的花朵不仅吸引传粉者，还吸引食花者，这可能会降低植物的繁殖成功率。因此，本研究在泰国考察了两个 R. ornata 种群，并评估了与传粉者吸引和奖励相关的特征，确定了其交配系统，鉴定了访花者和有效传粉者，并研究了食花对繁殖成功率的影响。
Rivea ornata 具有高度的繁殖力，但自交不亲和，是严格的异交者，使其高度依赖传粉者。鳞翅目昆虫，特别是夜间的鹰蛾，在所有访问中占很大比例，是该植物物种的唯一有效传粉者，与预测的授粉综合征一致。令人惊讶的是，食花并没有显著降低繁殖成功率。这种现象可能是由于 R. ornata 采用了与最优防御假说和功能权衡一致的策略。具体来说，R. ornata 似乎将资源投入到保护关键的花结构上，同时，守卫蚂蚁明显不在花朵上，导致一些食花者对非关键的花器官造成损害，但确保传粉者不会因蚂蚁而被吓退，从而保持高传粉者访问率。
我们的研究结果表明，R. ornata 的繁殖相关特征，包括吸引传粉者和奖励以及食花者防御的特征，非常有效，协同作用以最大限度地提高植物的繁殖成功率。因此，R. ornata 面临的主要风险是鹰蛾和其他鳞翅目昆虫的减少或消失，因为它极度特化且高度依赖传粉者，保护工作应包括保护 R. ornata 及其传粉者的栖息地。
