SUNY-ESF, Syracuse, NY 13210, USA.
Mycorrhiza. 2012 Nov;22(8):647-52. doi: 10.1007/s00572-012-0442-2. Epub 2012 May 9.
Pisonia grandis (Nyctaginaceae), a widespread tree of Pacific coral atolls and islands, displays one of the more restrictive ranges of ectomycorrhizal (ECM) fungus associates among autotrophic plants. Only five ECM fungi are currently known associates; our study adds one. In many habitats, P. grandis is restricted to large seabird colonies where nitrogen and phosphorus inputs in the form of guano are substantial. It has been suggested that the ECM specificity displayed by P. grandis is the result of the unusual nutrient-rich habitat in which P. grandis grows. On Rota, Commonwealth of the Northern Mariana Islands, P. grandis grows in habitats heavily influenced by guano additions and also in upland forests where seabirds do not roost or nest. To test the hypothesis that the ECM specificity displayed by P. grandis is the result of nutrient-related or toxicity-related factors associated with guano inputs, we sampled P. grandis growing in both guano-rich and guano-poor habitats on Rota, Commonwealth of the Northern Mariana Islands. We identified ECM symbionts of P. grandis from both habitats as well as two symbionts of Intsia bijuga (Fabaceae) from nutrient-rich habitats. We identified three ECM symbionts of P. grandis from Rota; all three were found in both guano-rich and guano-poor habitats. No differences in community diversity were detected between guano-rich and guano-poor habitats. We also detected two ECM fungal species associating with I. bijuga but not associating with P. grandis inside guano-rich habitats. From these results, we infer that edaphic factors are not responsible for limiting the ECM community associating with P. grandis to its observed level of specificity.
大花第伦桃（夹竹桃科）是太平洋珊瑚环礁和岛屿上广泛分布的树种，其外生菌根（ECM）真菌伴生物种的范围相对较窄。目前已知的 ECM 真菌伴生物种只有五种；我们的研究增加了一个。在许多栖息地，大花第伦桃仅限于大型海鸟聚居地，这些地方以鸟粪的形式提供大量的氮和磷。有人认为，大花第伦桃所表现出的 ECM 特异性是由于其生长的特殊养分丰富的栖息地所致。在北马里亚纳群岛联邦的罗塔岛，大花第伦桃生长在受鸟粪大量影响的栖息地，也生长在海鸟不栖息或筑巢的高地森林中。为了检验大花第伦桃所表现出的 ECM 特异性是由于与鸟粪输入相关的养分相关或毒性相关因素的假设，我们在北马里亚纳群岛联邦的罗塔岛采集了在富含鸟粪和鸟粪贫化的生境中生长的大花第伦桃样本。我们从这两个栖息地鉴定了大花第伦桃的 ECM 共生体，以及两种来自养分丰富栖息地的 Intsia bijuga（豆科）的共生体。我们从罗塔岛鉴定了三种大花第伦桃的 ECM 共生体；这三种共生体都存在于富含鸟粪和贫化鸟粪的生境中。在富含鸟粪和贫化鸟粪的生境中，没有检测到群落多样性的差异。我们还检测到两种与 I. bijuga 相关但不与 P. grandis 相关的 ECM 真菌物种存在于富含鸟粪的生境中。根据这些结果，我们推断土壤因素不是导致与 P. grandis 相关的 ECM 群落局限于其观察到的特异性水平的原因。
