Data from: Reproductive success, fruit removal and local distribution patterns in the early-flowering shrub Daphne mezereum

  

This is the data from the article 

Reproductive success, fruit removal and local distribution patterns in the early-flowering shrub Daphne mezereum

(DOI: XXXXXX)

Matilda Arnell, Ove Eriksson and Johan Ehrlén

DESCRIPTION

In this study we mapped the spatial distribution of individuals in a population of the early flowering, fleshy-fruited shrub Daphne mezereum, in a forest in boreo-nemoral Sweden for three consecutive years (2016-2018). For all mapped individuals we collected data on numbers of flowers and fruits and fruit removal. In one year, 2019, we also performed a hand pollination experiment. 

We analyzed spatial associations among individuals, and the effects on reproductive performance and fruit removal of plant height, numbers of flowers and fruits, distance to forest edge, and neighboring flower and fruit density.

The data includes:

An R-script to perform analyses included in the article

       Arnell_2023_script.R

Spatial locations, reproductive status (vegetative / reproductive) and plant height of all individuals of D. mezereum in the local population in 2016-2017

        daphne_16.csv

        daphne_17.csv       

        daphne_18.csv

Data on number of flowers, number of fruits, fruit removal, plant height, flowers and fruits on neighboring reproductive individual within a 10 m radius of each reproductive individual and the distance to forest edges for each reproductive individual in 2016-2018

        reproductive_16.csv

        reproductive_17.csv       

        reproductive_18.csv

Data on flower gender (hermaphroditic/female) and fruit set for a subset of the local population in 2016-2018

        pollination_16.csv

        pollination_17.csv       

        pollination_18.csv

Results from the hand pollination experiment for a subset of the local population in 2019

        pollination_19.csv

Size of the study area and the length and location of forest edges (shapefiles) used in the analyses of spatial associations in R (each shapefile consists of six files with the extensions: .cpg, .dbf, .prj, .sbn, .sbx, .shp, .shx, and can be opened in R or any GIS prgram such as the open source software QGIS) 

         win.shp 

         lines.shp

Please refer to the README-files for further information about each data set / item.

STUDY SPECIES

Daphne mezereum is a deciduous shrub that can grow up to a height of 200 cm. In Sweden, D. mezereum is a relatively rare species found mainly on damp, humus-rich soils at forest edges or in deciduous forests previously managed as meadows or grazed by livestock. D. mezereum is one of the earliest species to flower in this region. Flowers are usually open from April to May, although during mild winters the onset of flowering can be as early as February.

LOCATION

This study was carried out on the peninsula of Väddö in the Stockholm archipelago in south eastern Sweden. The study area covers approximately 4.8 hectares, largely located in a forest. In the area, the forest is dominated by Picea abies, with deciduous species (e.g. Betula spp. and Populus tremula) occurring mostly in forest edges and in forest gaps. The soil consists of glacial till influenced by nearby occurring calcareous bedrock. The mean temperature of January is -3.5 C° and the mean temperature for June is -15.9 C°, with a mean annual precipitation of 595 mm.

FIELD SURVEY

During the years 2016-2018, we mapped all established individuals of D. mezereum of approximately 10 cm and higher within the study area. Individuals that were not detected during the first year were added continuously the following years of survey. In late April to early May we recorded the number of buds and flowers on each individual, as well as plant height. We recorded the number of fruits in June to August.

In 2019, to investigate if individuals were pollen limited, we surveyed 70 reproductive individuals. For each individual we recorded if flowers were hermaphroditic or female (anthers without pollen or lacking anthers). On individuals with more than one branch, we performed a cross-pollination experiment. One branch was pollinated and the rest was left un-treated as control. Pollen was taken from three or more randomly selected plants not included in the survey and applied with a small brush into each flower tube, on both hermaphroditic and female flowers. In April to May, we recorded number of flowers and in June the number of developing fruits.

POLLINATION AND FRUIT SET

To estimate the degree of pollen limitation, we compared fruit set between individuals having hermaphroditic flowers (producing pollen) and individuals having female flowers (producing no pollen), and assessed the effect of the pollen-addition treatment on fruit set.

SPATIAL ASSOCIATIONS

To describe the spatial structure of the population, we estimated spatial associations among individuals of D. mezereum based on the spatial locations of all individuals in the three survey years. Spatial associations were estimated using the inhomogeneous pair correlation function ginhom(r). Spatial associations among individuals with the same reproductive status (reproductive/vegetative) were also estimated separately. 

To describe the spatial structure of the population in relation to landscape structures, we fitted an inhomogeneous Thomas cluster process, with distance to forest edge (distance to edge) as a covariate. 

INVESTMENT IN REPRODUCTION, REPRODUCTIVE SUCCESS AND DISPERSAL IN RELATION TO DISPERSAL TRAITS AND DISTRIBUTION PATTERNS

We considered six predictor variables when investigating the effects of plant traits and distribution patterns on number of flowers (investment in reproduction), fruit set (relative reproductive success) and fruit removal. The predictors included three traits, height, number of flowers and number of fruits, and three measures of spatial locations, distance to forest edge, total number of flowers within a 10 m radius (neighboring flower density) and total number of fruits within a 10 m radius (neighboring fruit density). We chose a radius of 10 m as the analyses of spatial associations showed positive spatial associations up to 10 m.

The effect of three variables (height, distance to edge, neighboring flower density) were included in the model explaining the number of flowers produced by individuals of D. mezereum.

The effect of four variables (height, flowers, distance to edge, neighboring flower density) were included in the model explaining the fruit set of individuals of D. mezereum.

The effect of four variables (height, fruits, distance to edge, neighboring fruit density) were included in the model explaining the fruit removal in individuals of D. mezereum.

Please consult the original article as well as the R-script "Arnell_2023_script.R" for details on how the data was analyzed. 

Please contact Matilda Arnell (matilda.arnell@su.se) for information or collaboration. 

Please cite the original article when using these data (DOI: XXXXX).