Abstract The genus Spondias has a wide variety of sexual systems, with complete monoecious to polygamodioecious species. Spondias macrocarpa (Anacardiaceae) is an endemic species from Brazil, previously described as hermaphroditic, and considered vulnerable due to massive deforestation. However, to our knowledge, no further details on the breeding system or morphological studies are available. Herewith, we examine the floral morpho-anatomy and breeding system of this species to better understand the sexual function of different floral morphologies and the role of pollinators in its reproduction. We used light and scanning electron microscopy to study the morphology and anatomy of the flowers. Additionally, we carried out experiments on pollen viability, stigmatic receptivity, and controlled pollinations. We found both bisexual and male flowers in the same inflorescence, with the staminate flowers presenting cryptic unisexuality. Investment in bisexual flowers was higher than in male ones, although more than 70% of the inflorescence was made up of male flowers. Most male flowers are present in the proximal region of the inflorescence, and there is no temporal separation between male and female functions in bisexual flowers. We show that S. macrocarpa is andromonoecious with cryptic-monoecy and a self-incompatibility system. Under natural conditions, S. macrocarpa is probably a pollinator generalist, with small bees being its main floral visitors. High levels of pollen robbing and low levels of crossing by floral visitors may result in the observed low fruit set. Further studies on the pre- and post-pollination barriers and on the reproductive ecology of extant natural populations should elucidate the reason for such a low fruit set.

中文翻译：

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Spondias macrocarpa Engl 的花卉形态解剖学和生殖生态学。（漆树科），一种脆弱的新热带雄性花序树

摘要 Spondias 属具有多种性系统，具有完全雌雄同株至多交雌雄异株的物种。Spondias macrocarpa (Anacardiaceae) 是一种来自巴西的特有物种，以前被描述为雌雄同体，并且由于大规模的森林砍伐而被认为是脆弱的。然而，据我们所知，没有关于育种系统或形态研究的更多细节。因此，我们检查了该物种的花卉形态解剖和繁殖系统，以更好地了解不同花卉形态的性功能以及传粉者在其繁殖中的作用。我们使用光学显微镜和扫描电子显微镜来研究花朵的形态和解剖结构。此外，我们还进行了花粉活力、柱头可受性和控制授粉的实验。我们在同一个花序中发现了双性花和雄花，雄花呈现出神秘的单性。对双性花的投资高于雄花，尽管 70% 以上的花序由雄花组成。大多数雄花存在于花序的近端区域，两性花的雄性和雌性功能在时间上没有分离。我们表明 S. macrocarpa 是雄性雌雄同株的，具有神秘的雌雄同株性和自交不亲和系统。在自然条件下，S. macrocarpa 可能是传粉者的通才，小蜜蜂是其主要的花卉访客。高水平的花粉抢劫和低水平的花客杂交可能导致观察到的低坐果率。