Arnold A Elizabeth, Lutzoni F
Department of Biology, Duke University, Durham, North Carolina 27708, USA.
Ecology. 2007 Mar;88(3):541-9. doi: 10.1890/05-1459.
Fungal endophytes are found in asymptomatic photosynthetic tissues of all major lineages of land plants. The ubiquity of these cryptic symbionts is clear, but the scale of their diversity, host range, and geographic distributions are unknown. To explore the putative hyperdiversity of tropical leaf endophytes, we compared endophyte communities along a broad latitudinal gradient from the Canadian arctic to the lowland tropical forest of central Panama. Here, we use molecular sequence data from 1403 endophyte strains to show that endophytes increase in incidence, diversity, and host breadth from arctic to tropical sites. Endophyte communities from higher latitudes are characterized by relatively few species from many different classes of Ascomycota, whereas tropical endophyte assemblages are dominated by a small number of classes with a very large number of endophytic species. The most easily cultivated endophytes from tropical plants have wide host ranges, but communities are dominated by a large number of rare species whose host range is unclear. Even when only the most easily cultured species are considered, leaves of tropical trees represent hotspots of fungal species diversity, containing numerous species not yet recovered from other biomes. The challenge remains to recover and identify those elusive and rarely cultured taxa with narrower host ranges, and to elucidate the ecological roles of these little-known symbionts in tropical forests.
真菌内生菌存在于所有主要陆地植物谱系的无症状光合组织中。这些隐秘共生体的普遍存在是显而易见的，但其多样性规模、宿主范围和地理分布尚不清楚。为了探究热带叶片内生菌的假定超多样性，我们比较了从加拿大北极地区到巴拿马中部低地热带森林的广泛纬度梯度上的内生菌群落。在此，我们使用来自1403个内生菌菌株的分子序列数据表明，从北极到热带地区，内生菌的发生率、多样性和宿主广度都在增加。高纬度地区的内生菌群落的特征是来自许多不同子囊菌纲的物种相对较少，而热带内生菌组合则由少数几个纲主导，其中内生菌物种数量众多。热带植物中最容易培养的内生菌具有广泛的宿主范围，但群落由大量宿主范围不明的稀有物种主导。即使只考虑最容易培养的物种，热带树木的叶子也是真菌物种多样性的热点，包含许多尚未在其他生物群落中发现的物种。挑战仍然是恢复和鉴定那些宿主范围较窄、难以捉摸且很少培养的分类群，并阐明这些鲜为人知的共生体在热带森林中的生态作用。
