Mukwevho Vuledzani O, Dreyer Léanne L, Roets Francois
Department of Conservation Ecology and Entomology, Stellenbosch University, Private Bag X1, Stellenbosch, 7600, South Africa.
Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Stellenbosch, 7600, South Africa.
Antonie Van Leeuwenhoek. 2020 Dec;113(12):2187-2200. doi: 10.1007/s10482-020-01491-6. Epub 2020 Nov 22.
Protea flowers host saprobic Knoxdaviesia and Sporothrix fungi that are dispersed by pollinating insects and birds. Different Protea species contain sympatric populations of different fungal species. For example, P. repens host S. splendens and K. proteae, while P. neriifolia host K. capensis and S. phasma. Even though all fungi can grow vigorously on alternative hosts and they share the same spore vector species, they rarely colonise alternative hosts. We investigated the role of fungal differential competitive abilities on their usual and alternative hosts to explain their host exclusivity. In a de Wit replacement series experiment, S. splendens outcompeted and later overgrew all other fungi on media prepared from its usual and alternative hosts. Host exclusivity of S. splendens on P. repens may therefore be maintained by restricted movement of spore vectors rather than weaker competitive abilities on alternative hosts. On their preferred hosts, S. splendens and S. phasma rapidly overgrew Knoxdavesia species with which they do not usually share a host, explaining host exclusivity of the Knoxdavesia species. Knoxdaviesia proteae likely only persist on P. repens with sympatric S. splendens if it colonizes flowers earlier, in a different area, or completes its life cycle before being overgrown. On their usual P. neriifolia host, K. capensis and S. phasma had neutralistic interactions and S. phasma could not overgrow K. capensis, explaining their co-existence. Host exclusivity of saprobic Protea-associated Knoxdaviesia and Sporothrix may therefore be maintained by both the activities of spore vectors and differential competitive abilities on different hosts, but the influence of other competing microbes and micro-niche differentiation cannot be excluded.
普罗蒂亚花是腐生的诺克斯戴维斯菌属（Knoxdaviesia）和孢子丝菌属（Sporothrix）真菌的宿主，这些真菌通过传粉昆虫和鸟类传播。不同的普罗蒂亚物种含有不同真菌物种的同域种群。例如，伏地普罗蒂亚（P. repens）宿主华丽孢子丝菌（S. splendens）和普罗蒂亚诺克斯戴维斯菌（K. proteae），而黑叶普罗蒂亚（P. neriifolia）宿主卡普ensis诺克斯戴维斯菌（K. capensis）和幻影孢子丝菌（S. phasma）。尽管所有真菌都能在替代宿主上旺盛生长，且它们共享相同的孢子传播媒介物种，但它们很少定殖于替代宿主。我们研究了真菌在其常见宿主和替代宿主上的差异竞争能力的作用，以解释它们对宿主的专一性。在一个德威特替代系列实验中，华丽孢子丝菌在由其常见宿主和替代宿主制备的培养基上竞争并超过了所有其他真菌。因此，华丽孢子丝菌在伏地普罗蒂亚上对宿主的专一性可能是由孢子传播媒介的有限移动维持的，而不是在替代宿主上较弱的竞争能力。在它们偏好的宿主上，华丽孢子丝菌和幻影孢子丝菌迅速超过了它们通常不共享宿主的诺克斯戴维斯菌属物种，这解释了诺克斯戴维斯菌属物种对宿主的专一性。如果普罗蒂亚诺克斯戴维斯菌在更早的时候、在不同的区域定殖于花朵，或者在被覆盖之前完成其生命周期，那么它可能只与同域的华丽孢子丝菌一起在伏地普罗蒂亚上持续存在。在它们常见的黑叶普罗蒂亚宿主上，卡普ensis诺克斯戴维斯菌和幻影孢子丝菌具有中性相互作用，幻影孢子丝菌不能超过卡普ensis诺克斯戴维斯菌，这解释了它们的共存。因此，与腐生普罗蒂亚相关的诺克斯戴维斯菌属和孢子丝菌属对宿主的专一性可能是由孢子传播媒介的活动和在不同宿主上的差异竞争能力共同维持的，但其他竞争微生物和微生态位分化的影响不能排除。
