Centre for Ecosystem Management, Edith Cowan University, Joondalup, WA, Australia.
Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parma, Italy.
Ann Bot. 2020 Aug 13;126(3):377-386. doi: 10.1093/aob/mcaa058.
Ant-plant associations are widely diverse and distributed throughout the world, leading to antagonistic and/or mutualistic interactions. Ant pollination is a rare mutualistic association and reports of ants as effective pollinators are limited to a few studies. Conospermum (Proteaceae) is an insect-pollinated genus well represented in the south-western Australia biodiversity hotspot, and here we aimed to evaluate the role of ants as pollinators of C. undulatum.
Pollen germination after contact with several species of ants and bees was tested for C. undulatum and five co-flowering species for comparison. We then sampled the pollen load of floral visitors of C. undulatum to assess whether ants carried a pollen load sufficient to enable pollination. Lastly, we performed exclusion treatments to assess the relative effect of flying- and non-flying-invertebrate floral visitors on the reproduction of C. undulatum. For this, we measured the seed set under different conditions: ants exclusion, flying-insects exclusion and control.
Pollen of C. undulatum, along with the other Conospermum species, had a germination rate after contact with ants of ~80 % which did not differ from the effect of bees; in contrast, the other plant species tested showed a drop in the germination rate to ~10 % following ant treatments. Although ants were generalist visitors, they carried a pollen load with 68-86 % of suitable grains. Moreover, ants significantly contributed to the seed set of C. undulatum.
Our study highlights the complexity of ant-flower interactions and suggests that generalizations neglecting the importance of ants as pollinators cannot be made. Conospermum undulatum has evolved pollen with resistance to the negative effect of ant secretions on pollen grains, with ants providing effective pollination services to this threatened species.
植物与蚂蚁的共生关系广泛多样，分布于世界各地，导致两者之间存在拮抗和/或互利的相互作用。蚂蚁传粉是一种罕见的互利共生关系，而有关蚂蚁作为有效传粉者的报道仅限于少数研究。科苏梅尔属（山龙眼科）是一个在澳大利亚西南部生物多样性热点地区广泛存在的昆虫授粉属，在这里，我们旨在评估蚂蚁作为 C.undulatum 传粉者的作用。
测试了几种蚂蚁和蜜蜂与 C.undulatum 花粉接触后的花粉萌发情况，并与五种共花期物种进行了比较。然后，我们对 C.undulatum 的访花者的花粉负荷进行了采样，以评估蚂蚁是否携带了足以进行传粉的花粉负荷。最后，我们进行了排除处理，以评估飞行和非飞行无脊椎动物访花者对 C.undulatum 繁殖的相对影响。为此，我们在不同条件下测量了种子的结实率：蚂蚁排除、飞行昆虫排除和对照。
C.undulatum 及其它科苏梅尔属物种的花粉与蚂蚁接触后的萌发率约为 80%，与蜜蜂的效果没有差异；相比之下，测试的其他植物物种在经过蚂蚁处理后，萌发率下降到约 10%。尽管蚂蚁是杂食性访客，但它们携带的花粉负荷中，有 68-86%的花粉是合适的。此外，蚂蚁显著促进了 C.undulatum 的结实率。
我们的研究强调了蚂蚁与花之间相互作用的复杂性，并表明忽略蚂蚁作为传粉者的重要性的泛化是不能成立的。C.undulatum 已经进化出了对蚂蚁分泌物对花粉粒的负面影响具有抗性的花粉，而蚂蚁为这个受到威胁的物种提供了有效的传粉服务。
