DOI: 10.5061/dryad.34tmpg4hc
title: Functional traits: Adaption of ferns in forest

description: Ferns evolved from 400 million years ago show various functional traits
 and ecological strategies in extant species, and over 80% of them belong
 to the youngest order Polypodiales. How the functional traits and
 strategies of ferns have changed during their evolutionary history remains
 unexplored. Here, we measured functional traits that sensitive to
 environmental light and water availability of 345 fern species across the
 fern phylogeny, and reconstructed their evolutionary histories. We found
 that ferns, mainly Polypodiales, have developed diversified functional
 traits in response to forest environments. Terrestrial species, especially
 Thelypteridaceae and Athyriaceae in eupolypods II, showed decreased leaf
 mass per area (LMA) and area-based leaf nitrogen (Narea) but increased
 mass-based leaf nitrogen (Nmass) than early-derived polypods since the
 late Jurassic. Epiphytic species, mainly those in Polypodiaceae, showed
 reductions in Nmass and individual leaf area (Area) since the late
 Cretaceous. The adaptation of functional traits of Polypodiales to forest
 environment may have played a crucial role in fern radiation since the
 late Jurassic. Integrative analysis of functional traits especially the
 numerical ones may shed new light on plant evolution.
description:  In the field, we
 sampled 950 sporophytes of 345 fern species identified according to the
 Flora of China (Lin et al., 2013), which covers 87 genera, 28 families and
 9 out of 11 orders in the PPG I system (PPG I, 2016) (Table S1). For each
 species except a few rare ones, at least three individuals were collected
 as three samples; and for each individual three or more fully expanded and
 healthy leaves were collected. For each sampled individuals, we measured
 four numeric leaf functional traits, including LMA,
 N<sub>area</sub>, N<sub>mass</sub> and Area
 (Pérez-Harguindeguy et al., 2013), and recorded three categorical traits,
 including growth form, leaf venation type and leaf type. Each sample with
 single leaf petioles or compound leaf rachis removed was scanned using an
 image scanner (LiDE110, Cannon, Japan). Projected leaf area
 (cm<sup>2</sup>) of each sample was measured using the
 WinFOLIA system (Regent, Canada). Leaves were oven dried for at least 48 h
 at 60 °C to a constant weight, and the leaf dry mass was weighed to the
 nearest milligram. For each sample, LMA (g m<sup>-2</sup>) was
 calculated as the leaf dry mass divided by the projected area;
 N<sub>mass</sub> (mg g<sup>-1</sup>) was measured
 using an elemental analyser (Elementar, Germany);
 N<sub>area</sub> (mg m<sup>-2</sup>) was
 calculated as N<sub>mass</sub> × LMA. The growth form
 (terrestrial, lithophyte or epiphytic), leaf type (single or compound) and
 leaf venation type (open, semi-reticulate or reticulate) were also
 recorded (Table S1). The traits data at species level were averaged from
 all the sampled individuals within the species accordingly (Table
 S2). <b>Table S1.</b>
 Functional traits of 950 individuals of 345 fern species. <b>Table S2.
 </b>Functional traits of 345 fern species in Fig. 2. <b>Table S3.
 </b>Functional traits of ferns and seed plants in Fig. 3.
 <b>Data S1.</b>
 Time-calibrated phylogeny of 345 fern species in Fig. 2. <b>Figure
 S1. </b>Variation of four functional traits of ferns explained by
 three climatic factors and growth form. <b> </b>