DOI: 10.5061/dryad.66t1g1jzp
title: Intraspecific variation of Phragmites australis: Clinal adaption of functional traits and phenotypic plasticity vary with latitude of origin

description: 1. Widespread plant species generally have high intraspecific variation in
 functional traits, which is reflected in their great variety of
 phenotypes. This variety can result from both genetic differences due to
 local adaptation and phenotypic plasticity. With high intraspecific
 variation and nearly global distribution, the common reed Phragmites
 australis is a suitable model species for studying the underlying
 mechanisms of intraspecific trait variation.  2. In this study,
 71 genotypes of P. australis from seven phylogeographic groups were
 transplanted into two replicate common gardens located in very different
 climates: northern Europe and mid-east Asia. We measured seven functional
 traits of all these genotypes over the growing season, including shoot
 height, maximum biomass per shoot, shoot density, node number per stem,
 leaf lifespan, flowering occurrence and flowering date. Our aim was to
 assess the relative effects of genetic (phylogeographic origin) and
 environmental (common garden) status, and interactions between them, on
 intraspecific variation in functional traits of P. australis.  3.
 We found common garden having the strongest influence on most functional
 traits studied. All traits except flowering occurrence varied
 significantly across gardens, revealing the important role of phenotypic
 plasticity on trait variation of P. australis. We also found significant
 differences in trait variation among the different phylogeographic groups
 of P. australis and, thus, evidence for genetically determined
 intraspecific variation in the morphological and life-history traits
 addressed in this study. All functional traits showed significant
 (p≤0.0054), albeit minor to moderately explained (R2 ≤0.57), latitudinal
 patterns in both gardens. Covariation of multiple traits was similar in
 the two gardens. Phenotypic plasticity was trait-specific, and the
 plasticity of shoot height and maximum biomass per shoot increased towards
 higher latitude of genotypic origin. Our results indicate that the
 latitude of origin affects the evolution of functional traits, as well as
 their phenotypic plasticity.  4. Since phenotypic plasticity is a
 crucial mechanism for acclimation and evolution, our findings support the
 role of gene-based adaptive phenotypic plasticity in plant evolution. The
 intraspecific spatial variation of functional traits and their phenotypic
 plasticity can help predict species distribution, persistence and invasion
 under global climate change.
description: <i>Common
 garden setup</i> This study was
 conducted outdoors in two experimental gardens: one in Denmark (Aarhus
 University, 56°13´N; 10°07´E) and the other in China (Shandong University,
 36°25´N; 117°26´E). Both gardens were located in open spaces without
 shading. We selected 71 genotypes in total of<i> P.
 australis</i> from four different continents, covering seven
 phylogeographic groups: one European (EU, n=12), one Mediterranean (MED,
 n=12), one Far East Australian (FEAU, n=12) and four North American (NA)
 groups, comprising NA Introduced (NAint, n=12), NA Native (NAnat, n=6),
 LAND (n=11) and DELTA (n=6) (C. Lambertini et al., 2006; Carla Lambertini,
 Sorrell, et al., 2012) (Figure 1). The LAND-group,  was previously called
 the Gulf (or GC) type or <i>P. australis</i> var.
 <i>berlandieri</i> is Haplotype I and is mainly distributed
 along the Gulf Coast of North America, while the DELTA-group, is Haplotype
 M1, and is dominant in the Mississippi River Delta (Lambertini et al.,
 2012; Ward, 2010). EU, FEAU, MED and NAnat groups are native (representing
 historic adaptation and evolution), while DELTA, LAND and NAint are
 introduced (representing recent adaptation) in the areas they were sampled
 (Lambertini et al., 2012; Guo et al. 2013). Rhizomes from natural stands of different <i>P. australis</i> populations have been collected over several years, genotyped and maintained in the Danish common garden since 2001. Because of potential pot-binding, all genotypes were replanted every third year. In 2014, the rhizomes of each genotype were split into two parts: one part was transplanted into the Danish garden, the other part was transplanted into the Chinese garden. In both gardens, each genotype was planted in a pot (0.65 m diameter and 0.5 m height) containing a substrate of 50% peat soil and 50% quartz-rich sand (granule diameter of 0-2 mm). The pots were spaced 2 m apart from each other and buried into the ground to keep the soil surface at the same level with the surrounding ground. Plants were weeded manually, but no other pest control was undertaken in either garden. An automatic irrigation system using local municipal water was used to water the plants. Small holes in each pot allowed drainage of excess water to keep the water level similar among genotypes. Each pot was fertilized every two weeks from March to December with 100 mL of fertilizer containing 0.1 kg L<sup>-1</sup> macro nutrients (NPK ratio 19:5:19 + MgO) and trace elements.   <i>Functional trait measurements</i> All measurements were carried out from March 21<sup>st</sup> to November 17<sup>th</sup>, 2016, on the same dates in both gardens. Shoot height, which was measured from the top of the soil to the tallest shoot tip including the apical leaf, and node number per stem of the five tallest and healthy shoots of each genotype were measured every two weeks. To determine aboveground biomass per shoot, the five tallest and healthy shoots of each genotype were harvested at the end of the growing season when the shoot height had not changed over three consecutive measurement dates, and oven-dried at 80 °C for at least 48 hours. Shoot density, defined as the number of live shoots per pot, was measured once at the beginning and once at the end of the growing season. For leaf lifespan, one young green apical leaf was marked randomly on five different shoots per genotype in early June, recorded as the beginning of leaf development. The onset of senescence was noted as the day the marked leaves started to turn yellow and wither. The number of days from the beginning of leaf development until turning senescent was defined as leaf lifespan. For flower occurrence, we noted for each genotype whether it had flowered or not during the growing season. Flowering date was expressed as the number of days that had elapsed in 2016 until the date of observation of the first developing panicle.