Data from: Life cycle matters: DNA barcoding reveals contrasting community structure between fern sporophytes and gametophytes

Ferns are the only major lineage of vascular plants that have
nutritionally independent sporophyte (diploid) and gametophyte (haploid)
life stages. However, the implications of this unique life cycle for fern
community ecology have rarely been considered. To compare patterns of
community structure between fern sporophytes and gametophytes, we
conducted a survey of the ferns of the islands of Moorea and Tahiti
(French Polynesia). We first constructed a DNA barcode library (plastid
rbcL and trnH–psbA) for the two island floras including 145 fern species.
We then used these DNA barcodes to identify more than 1300 field-collected
gametophytes from 25 plots spanning an elevational gradient from 200 to
2000 m. We found that species richness of fern sporophytes conforms to the
well-known unimodal (i.e., mid-elevation peak) pattern, reaching a maximum
at ca. 1000 – 1200 m. Moreover, we found that fern sporophyte communities
become increasingly phylogenetically clustered at high elevations. In
contrast, species richness of fern gametophytes was consistent across
sites, and gametophytes showed no correlation of phylogenetic community
structure with elevation. Turnover of sporophyte and gametophyte
communities was closely linked with elevation at shallow phylogenetic
levels, but not at deeper nodes in the tree. Finally, we found several
species for which gametophytes had broader ranges than sporophytes,
including a vittarioid fern with abundant gametophytes but extremely rare
sporophytes. Our study highlights the importance of including diverse life
history stages in surveys of community structure, and has implications for
the possible impacts of climate change on the distribution of fern
diversity.

蕨类是唯一一类具有营养独立的孢子体（sporophyte，二倍体）和配子体（gametophyte，单倍体）生活阶段的维管植物主要类群。然而，这一独特生命周期对蕨类群落生态学的意义却鲜有研究。为比较蕨类孢子体与配子体之间的群落结构模式，我们对法属波利尼西亚的莫雷阿岛和塔希提岛的蕨类进行了调查。我们首先为这两个岛屿的植物区系构建了一个包含145种蕨类的DNA条形码库（DNA barcode library，质体rbcL和trnH–psbA基因）。随后，我们利用这些DNA条形码对来自25个样地的1300多个野外采集配子体进行了鉴定，这些样地覆盖了200至2000米的海拔梯度。我们发现蕨类孢子体的物种丰富度符合众所周知的单峰（即海拔中部峰值）模式，在约1000–1200米处达到最大值。此外，蕨类孢子体群落在高海拔地区的系统发育聚类（phylogenetic clustering）程度逐渐增强。相比之下，蕨类配子体的物种丰富度在各站点间保持一致，且配子体的系统发育群落结构（phylogenetic community structure）与海拔无相关性。孢子体和配子体群落的周转（community turnover）在浅系统发育水平上与海拔密切相关，但在系统发育树的深层节点上则无此关联。最后，我们发现若干物种的配子体分布范围比孢子体更广，其中包括一种配子体丰富但孢子体极为罕见的书带蕨类蕨（vittarioid fern）。本研究强调了在群落结构调查中纳入不同生活史阶段的重要性，并为气候变化对蕨类多样性分布的潜在影响提供了参考。