DOI: 10.5061/dryad.j6q573n9t
title: Data from: Pollen limitation in the endangered Chinese endemic species Sinocalycanthus chinensis

description: Pollen limitation negatively impacts endangered and endemic plants with
 small fragmented populations, such as Sinocalycanthus chinensis, an
 endangered plant endemic to China. In this study, we analyzed the pollen
 limitation of the S. chinensis Damingshan (DMS) population in 2006, 2009,
 and 2010, and crossed plants with mates separated by different distances,
 both within and between populations. The DMS population exhibited strong
 pollen limitation in fruit set, seed set, and seeds per fruit in 2006,
 2009, and 2010. The average accumulated pollen limitation (for fruit set
 times seeds per fruit) was 0.510 ± 0.180. Progeny crossed with pollen from
 intermediate neighboring plants within the same population (separated by
 30 – 50 m from pollen recipients) had the lowest fitness. No optimal
 outcrossing distance was found within the DMS population. Progeny from
 crosses with the SXW and DLS populations performed relatively better,
 while those from crosses with QLF and LXS populations performed worse.
 Compared with average reproductive success, outbreeding depression was
 found in progeny from crosses with the LXS and QLF populations.
 Reproductive success from pure self-pollination indicated S. chinensis is
 self-compatible. Geitonogamous selfing increased reproductive success.
 Based on geitonogamous selfing, the proportion of selfed offspring was
 relatively high. These results provide basic references for the
 conservation of this species.
description: Study site This study was conducted at
 Damingshan Mountain (DMS, 30º02′N, 118º59′E), Linan City, Zhejiang
 Province, China (Table 1), the location of the largest known extant
 population (Liu, Zhou, Huang, Bao & Zhao, 2016). The pollen donor
 plants were located in the main DMS population and the other five
 populations were located at Tashajiang Village (TSJ), Shunxiwu Village
 (SXW), and Qingliangfeng Mountain (QLF) in Linan City, Zhejiang Province,
 Daleishan Mountain (DLS) in Tiantai County, Zhejiang Province, and
 Longxushan Mountain (LXS) in Jixi County, Anhui Province (Table 1). Among
 these populations, the population size of SXW and QLF were relatively
 large (Table 1). Experimental design
 Pollen limitation As a woody shrub, the age
 class of <em>S. chinensis</em> can be estimated from the
 volume calculated as <em>d</em> from the formula
 <em>d</em>=<em>a×b×c</em>, where
 <em>a</em> is the height of the tallest stem,
 <em>b</em> is the crown width along the longitudinal axis, and
 <em>c</em> is the width along the perpendicular axis (Yang et
 al., 2006). For <em>S. chinensis</em> in the DMS population,
 the age class ranged from 0 to 3 (Li, Jin & Liu, 2012). In May
 2006, 19 mature plants in age class III (2 &lt; <em>d
 </em>£ 3) and with similar phenologies that were located in the
 center of the DMS population and separate from each other by distances of
 more than 10 m were chosen as pollen recipients. Pollen grains were also
 collected from 15 pollen donor plants in age class III and with similar
 phenologies that were located within the same population and separated
 from each other by a distance of more than 10 m by rubbing a toothpick
 against newly dehisced anthers. The pollen grains were then mixed in a
 small plastic vial and stored at 4°C on ice bags in a plastic box, and
 then the pollen grains were transferred to recipient stigmas within 2
 hours (Irwin, 2001). In total, 30 flowers were used for each pollen
 supplementation, and 30 flowers among 19 naturally open-pollinated DMS
 plants were selected as the control (Bossuyt, 2007; Holmes, James
 & Hoffmann, 2008). In October 2006, fruits from all tested plants
 were collected. Fruit set was calculated as the number of mature fruits
 divided by the number of treatment flowers. Seed set was estimated as the
 average number of mature seeds divided by the number of fruits within a
 treatment. (Seeds have a dark, shiny, thickened seed coat when mature. If
 ovules are not fertilized or aborted, the seeds are very thin,
 transparent, and whitish in color). The mean number of seeds per fruit was
 also measured. Similar experiments were conducted in
 May and October in 2009 and 2010 to obtain two biological replicates. In
 2009 and 2010, 100 and 30 flowers for each treatment were used,
 respectively. We calculated the pollen limitation of the species by
 averaging PL values over the three years. Optimal
 outcrossing distance In May 2009, before <em>S.
 chinensis </em>flowers were open, emasculation and bagging was
 conducted to protect the stigma, then a pollen supplementation experiment
 was conducted by pollinating flowers with pollen grains collected from
 different populations separated by nine different distances (Table 1) to
 determine the optimal outcrossing distance. Nine treatments were conducted
 as follows. (1) Geitonogamous selfing was conducted by supplementary
 hand-pollination with geitonogamous pollen from the same plant. (2)
 Immediate neighbor treatments were conducted by supplementary
 hand-pollination with xenogamous pollen collected from plants within the
 same population separated by distances of 1 to 20 m. (3) Intermediate
 neighbor treatments were conducted by supplementary hand-pollination with
 xenogamous pollen collected from plants within the same population
 separated by distances of 30 to 50 m. (4) Remote neighbor treatments were
 conducted by supplementary hand-pollination with xenogamous pollen
 collected from plants within the same population separated by distances of
 80 to 100 m and thus unlikely to interact via open pollination. The
 within-population distances from the center of the DMS population were
 measured with tape measures. (5–9) Between population treatments were
 conducted by supplementary hand-pollination with xenogamous pollen
 collected from plants in the TSJ, SXW, QLF, LXS, and DLS populations,
 respectively. Geographical distances were calculated using Earth Explorer
 4.0, and a detailed summary of the nine treatments is provided in Table 1.
 Thirty flowers from 19 mature plants in age class III (2 &lt;
 <em>d </em>£ 3), with similar phenologies, and that were
 located in the center of the DMS population and separated from each other
 by a distance of more than 10 m were chosen as pollen recipients for each
 treatment. Pollen grains were collected from 15 pollen donor plants in age
 class III, with similar plant phenologies, separated from each other by a
 distance of more than 10 m, and located in the different populations in
 Table 1 by rubbing a toothpick against newly dehisced anthers. The pollen
 grains were then mixed in a small plastic vial and stored at 4°C on ice
 bags in a plastic box, and then the pollen grains were transferred
 immediately to recipient stigmas. According to a previous study by Zhang
 and Jin (2007), the pollen viability of <em>S. chinensis
 </em>lasts for five days after collection (no significant difference
 was detected among pollen of different days). The within-population pollen
 grains were used for hand-pollination within 2 hours, while the
 between-population pollen grains were used for hand-pollinations within 6
 hours, without an observed decrease in the viability of the pollen grains.
 All hand-pollinated stigmas were saturated with pollen grains. After
 treatment, bagging was conducted on the flowers to avoid the contamination
 of other pollens.
description: # Data from: Pollen limitation in the endangered Chinese endemic species
 Sinocalycanthus chinensis 
 ## Description of the data and file structure Table 1 Fruit set, seed set,
 and seeds per fruit produced by naturally open-pollinated flowers
 (control), under xenogamous pollen supplementation treatments in
 Sinocalycanthus chinensis. Table 2 Fruit set, seed set, and seeds per
 fruit under the nine pollen supplementation treatments in Sinocalycanthus
 chinensis.