DOI: 10.5061/dryad.xwdbrv1nv
title: Data from: Inbreeding depression affects the growth of seedlings of an African timber species with a mixed mating reproductive system, Pericopsis elata (Harms) Meeuwen

description: Selfing or mating between related individuals can lead to inbreeding
 depression (ID), which can influence the survival, growth and evolution of
 populations of tree species. As selective logging involves a decrease in
 the density of congeneric partners, it could lead to increasing biparental
 inbreeding or self-fertilization, exposing the population to higher ID. We
 assessed the influence of inbreeding on the growth of a commercial timber
 species, Pericopsis elata (Fabaceae), which produced about 54% of
 self-fertilized seedlings in a natural population of the Congo basin. We
 followed the survival and growth of 540 plants raised in a plantation
 along a gradient of plant density (0.07 to 15.9 plants per m2). Parentage
 analysis allowed us distinguishing selfed and outcrossed seedlings. The
 annual growth was higher for outcrossed than selfed plants, on average by
 10.8% for diameter and 12.9% for height growth. Based on the difference in
 above ground biomass between selfed and outcrossed seedlings after 41
 months, we estimated the level of ID at d = 0.33, while a lifetime
 estimate of ID based on the proportions of selfed plants at seedling and
 adult stages led to d = 0.7. The level of ID on growth rate did not change
 significantly with age but tended to vanish under high competition.
 Pericopsis elata is a particularly interesting model because inbreeding
 depression is partial, with about 26% of reproducing adults resulting from
 selfing, contrary to most tropical tree species where selfed individuals
 usually die before reaching adulthood. Hence, the risks of ID must be
 considered in the management and conservation of the species.
description: Seeds were harvested between 17 September and 12 December 2016 in
 the 400 ha plot of Biaro forest, where all 196 <em>Pericopsis
 elata</em> trees (diameter at breast height ≥ 10 cm) had been
 inventoried. Seed trees were retained only if they produced mature seeds
 and were sufficiently isolated to avoid any confusion of seed provenance
 (19 seed trees eventually contributed to the seed pool used). One week
 after harvesting, seeds were sowed in polyethylene bags containing soil
 with natural manure, and an ID label indicating the seed tree. The nursery
 was located next to the botanical garden of the Science Faculty campus of
 the University of Kisangani (DR Congo), under mild shading. After
 germination, we randomized the positions of the seedlings in the nursery
 and followed their growth for one year before transplantation.
 We installed three plantation trials in October 2017 according to
 the design Ia proposed by Nelder (1962), whereby plants are located along
 a set of concentric circles ensuring a gradient of sapling density. Each
 unit (Nelder 1, Nelder 2 and Nelder 3) is referred to as a replicate in
 the following sections. The experiment was carried out over an area of 135
 x 45 = 6,075 m<sup>2</sup> (including areas around each Nelder
 design) and each replicate covers an area of 908
 m<sup>2</sup>. This area was cleaned from former
 vegetation<br>(fallow land), allowing to prevent the destruction of
 the designs by uncontrolled bush fires. The replicates
 were placed next to each other to maximize the similarity of environmental
 conditions (edaphic, topographic and sun exposure). Each Nelder design
 consisted of 12 concentric circles, each one with 18 equally spaced
 saplings. The saplings located on the first and last circles formed the
 buffer zones, placed respectively at a distance of 0.6 and 15.6 m from the
 centre of the circles, so that a total of 180 saplings out of 216 were
 monitored for each replicate. The local spacing between neighbouring
 saplings ranged from 0.2 x 0.2 m to 3.8 x 3.8 m.
 Saplings from the nursery were transplanted on October 2017, when
 they had reached heights ranging from 40 cm to 160 cm (median around 65
 cm). As available sample sizes varied widely among maternal families, we
 could not conceive a well-balanced design. In Nelder 1 and Nelder 2, where
 19 and 10 families were represented, we ensured that saplings from the
 same mother tree were never contiguous. This was not feasible in Nelder 3,
 represented by seven families but with two of them constituting 88% of the
 saplings. Within each Nelder design, we ensured that represented families
 were well spread among the different circles to avoid any confounding
 effect between maternal tree and local density. Initial sapling height did
 not differ significantly among replicates. Dead saplings were replaced
 immediately when found. The total height and diameter
 at 10 cm from the collar were measured after two months and then at three
 months intervals on all saplings between December 2017 and March 2021,
 using a ruler and a caliper graduated in cm and mm, respectively. The
 total height was measured from the collar to the terminal bud of the
 longest branch. Weeding was carried out before each measurement period. We
 computed a competition index (C) for each sapling as a function of the
 distance and diameter of neighbouring saplings situated within a circle of
 radius K, according to Hegyi, 1974 and Vanclay et al., 2013.
description: # Inbreeding depression affects the growth of seedlings of an African
 timber species with a mixed mating reproductive system, *Pericopsis elata*
 (Harms) Meeuwen
 [https://doi.org/10.5061/dryad.xwdbrv1nv](https://doi.org/10.5061/dryad.xwdbrv1nv) This dataset contains data on the monitoring of seedlings of *Pericopsis elata*, a timber species from the African tropical zone, planted in the Nelder design in Kisangani, DR Congo. It includes diameter and height measurements of 540 seedlings planted in October 2017 and measured every 3 months until 2021. Each seedling was genotyped to distinguish outcrossed and selfed seedlings. ## Description of the data and file structure The database (Angbonda_et_al._2024.xlsx) contains the numbers of each Nelder design (Nelder replicate; the words in brackets are the name of the column in the sheet), of each mother tree (Mother tree) that produced the seedlings, the number of each seedling (Num_plant) and the position of each seedling on the design with the different directions of each Nelder design (Direction) and the number of each circle (Circle Number). Parentage analysis (Outcrossing) enabled us to distinguish seedlings whose probability of being outcrossed or selfed was greater than 80%. Thus, in the Outcrossing column, outcrossed and selfed seedlings are represented by 0 and 1, respectively. Unassigned seedlings were represented by #N/A. The different measurements of tree height and diameter are listed in different columns in the form: Height_4 (cm)*sept 2018, indicating the number of the measurement, here height number 4 in centimetres and the measurement date, here in September 2018. The Hegyi (1974) competition index (C) was computed using the statistical software R (R Core Team, 2022) considering the size of trees and distance between trees. More details are provided in Ilunga-Mulala et al. (2021) ([https://hdl.handle.net/2268/257065](https://hdl.handle.net/2268/257065)). The script is provided below. The studied ages in this study were 17, 29 and 41 months after planting, were calculated using date difference in Excel. The increments are represented by Δ with ΔD*(mm/year) and ΔH_(cm/year), the diameter increment in millimetres per year and the height increment in centimetres per year.