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.

Protea花寄主腐生的Knoxdaviesia和Sporothrix真菌，它们通过授粉昆虫和鸟类传播。不同的Protea物种包含不同真菌物种的同域种群。例如，P. repens寄主S. splendens和K. proteae，而P. neriifolia寄主K. capensis和S. phasma. 尽管所有真菌都可以在替代宿主上生长旺盛并且它们共享相同的孢子载体物种，但它们很少在替代宿主上定殖。我们调查了真菌差异竞争能力对其通常和替代宿主的作用，以解释它们的宿主排他性。在 de Wit 替代系列实验中，S. splendens在由其常用宿主和替代宿主制备的培养基上胜过所有其他真菌，并随后使其过度生长。因此，S. splendens对P. repens 的宿主排他性可能是通过限制孢子载体的运动而不是在替代宿主上较弱的竞争能力来维持的。在它们喜欢的宿主上，S. splendens和S. phasma迅速过度生长Knoxdavesia物种与它们通常不共享一台主机，说明该主机独占Knoxdavesia物种。Knoxdaviesia proteae可能仅在P. repens与同域S. splendens上持续存在，前提是它较早在不同区域定殖花，或在杂草丛生之前完成其生命周期。在它们通常的P. neriifolia宿主上，K. capensis和S. phasma具有中性相互作用并且S. phasma不能过度生长K. capensis，这解释了它们的共存。saprobic的主机独占普罗蒂亚机相关Knoxdaviesia和因此，孢子丝菌可能通过孢子载体的活性和不同宿主上的差异竞争能力来维持，但不能排除其他竞争微生物和微生态位分化的影响。