An understanding of epiphyte richness and the factors controlling it is fundamental for conserving the diversity of natural mesic forests. Host tree size is a determinant of epiphyte occurrence; however, previous studies have produced opposing results regarding the spatial distribution (patchy or random) of diversity. This study assessed the relationship between host tree size preference and the distribution of vascular epiphytes in a mature broadleaf evergreen forest in Kochi, southern Japan. The host tree size preferences of epiphytes occurring on more than eight of 247 host trees were assessed using generalized linear mixed models. We established a 0.59-ha forest census plot in a valley bottom with abundant epiphytes, and used Ripley’s L function and envelope simulations to assess the spatial distribution patterns for an epiphyte species showing lower size preference, and the large trees to which many epiphyte species were expected to adhere. We found that Davallia mariesii, Loxogramme salicifolia, Bulbophyllum inconspicuum, Dendrobium moniliforme, Eria japonica, and Ribes ambiguum showed higher host size preferences. The large trees to which these epiphytes were expected to adhere were randomly distributed. By contrast, Lemmaphyllum microphyllum and Lepisorus onoei showed lower host size preferences. The spatial distribution of trees with L. microphyllum showed a clustered pattern. These results imply that host size preference may vary among epiphyte species depending on their ecological traits and be reflected in their spatial distributions. Therefore, epiphyte distributions are not necessarily either random or clustered spatially.

了解附生植物的丰富性及其控制因素，对于保护天然斜生林的多样性至关重要。寄主树的大小是附生植物发生的决定因素。但是，先前的研究在多样性的空间分布（零散或随机）方面产生了相反的结果。这项研究评估了日本南部高知的成熟阔叶常绿森林中寄主树大小偏好与维管附生植物分布之间的关系。使用广义线性混合模型评估了247棵宿主树中超过八棵的附生植物的宿主树大小偏好。我们在有丰富的附生植物的山谷底部建立了一个0.59公顷的森林普查区，并使用Ripley's L功能和包络模拟，以评估表现出较低尺寸偏好的附生种以及预期附有许多附生种的大树的空间分布模式。我们发现，大麦，旱莲，无花粉，石D石D，粳稻和Ri菜显示出较高的寄主大小偏好。这些附生植物预期附着的大树是随机分布的。相比之下，小叶小球藻和小Lepisorus onoei表现出较低的寄主大小偏好。小叶柳桉树的空间分布显示出集群模式。这些结果表明，寄主大小偏好可能因附生植物种类而异，具体取决于其生态特征，并反映在其空间分布中。因此，附生植物分布不一定在空间上是随机的或成簇的。