The behaviour of pollinators has important consequences for plant mating. Nectar-feeding birds often display behaviour that results in more pollen carryover than insect pollinators, which is predicted to result in frequent outcrossing and high paternal diversity for bird-pollinated plants. We tested this prediction by quantifying mating system parameters and bird visitation in three populations of an understory bird-pollinated herb, Anigozanthos humilis (Haemodoraceae). Microsatellite markers were used to genotype 131 adult plants, and 211 seeds from 23 maternal plants, from three populations. While outcrossing rates were high, estimates of paternal diversity were surprisingly low compared with other bird-pollinated plants. Despite nectar-feeding birds being common at the study sites, visits to A. humilis flowers were infrequent (62 visits over 21,552 recording hours from motion-triggered cameras, or equivalent to one visit per flower every 10 days), and the majority (76%) were by a single species, the western spinebill Acanthorhynchus superciliosus (Meliphagidae). Pollen counts from 30 captured honeyeaters revealed that A. humilis comprised just 0.3% of the total pollen load. For 10 western spinebills, A. humilis pollen comprised only 4.1% of the pollen load, which equated to an average of 3.9 A. humilis pollen grains per bird. Taken together, our findings suggest that low visitation rates and low pollen loads of floral visitors have led to the low paternal diversity observed in this understory bird-pollinated herb. As such, we shed new light on the conditions that can lead to departures from high paternal diversity for plants competing for the pollination services of generalist nectar-feeding birds.

传粉者的行为对植物交配具有重要影响。以花蜜为食的鸟类通常表现出比昆虫授粉者更多的花粉携带量的行为，预计这会导致鸟类授粉植物的频繁异交和高父本多样性。我们通过在林下鸟类授粉的草本Anigozanthos humilis（Haemodoraceae）的三个种群中量化交配系统参数和鸟类访问来测试这一预测。微卫星标记用于对来自三个种群的 131 株成年植株和 23 株母本植株的 211 粒种子进行基因分型。虽然异交率很高，但与其他鸟类授粉植物相比，对父本多样性的估计却出奇地低。尽管在研究地点吃花蜜的鸟类很常见，但访问A. humilis花很少见（在 21,552 记录小时内通过运动触发相机进行 62 次访问，或相当于每 10 天对每朵花进行一次访问），并且大多数 (76%) 是单一物种，即西部刺鹬Acanthohynchus superciliosus（食蚜蝇科）。来自 30 只捕获的食蜜鸟的花粉计数显示，A. humilis仅占总花粉量的 0.3%。对于 10 只西部刺鸟，A. humilis花粉仅占花粉量的 4.1%，相当于平均 3.9 A. humilis每只鸟的花粉粒。综上所述，我们的研究结果表明，在这种林下鸟类授粉的草本植物中，低访问率和花粉量低导致父本多样性低。因此，我们揭示了可能导致植物竞争多才多艺的花蜜喂养鸟类授粉服务的高父本多样性的条件。