DOI: 10.5061/dryad.3r2280gr4
title: Field measurements performed on Staghorn fern colonies (Platycerium bifurcatum)

description: This study explores the relationship observed between ‘guests’ – foreign
 inhabitants of social colonies – and the density and fecundity of
 eusocial-like staghorn ferns (Platycerium bifurcatum, Polypodiaceae). Our
 observations suggest that guests in staghorn colonies have a range of
 commensal and negative relationships, paralleling those seen in eusocial
 animal species.
description: The genus <em>Platycerium</em> comprises 18 epiphytic
 species with a pantropical distribution (Kreier & Schneider,
 2006). The ‘common staghorn fern’ (<em>P. bifurcatum</em>)
 occurs on the Sunda Islands, Eastern Australia, Lord Howe Island and New
 Guinea (Hoshizaki, 1972; Kreier & Schneider, 2006). Our research
 focused on staghorn ferns occurring in Lord Howe Island (LHI), a volcanic
 island of &lt;15 km<sup>2</sup> in area (31°33'S,
 159°05'E), located app. 500 km east of Australia in the Tasman Sea.
 Although the island supports a diverse range of habitats (Harris et al.,
 2005), lowland areas are dominated by stunted tropical dry forest, where
 <em>P. bifurcatum</em> colonies are located within arm’s reach
 (Dawes et al., 2020). To investigate the frequency and
 diversity of ‘guests’ in staghorn colonies, we inspected all colonies
 located within a 5-meter distance on either side of three narrow tracks
 winding through the island’s tropical dry forest (total track length
 approximately 5 km; Figure S1). Morphological differences between guests
 and staghorn colonies, as well as among guests themselves, facilitated
 their identification. We recorded the relationship between guest presence
 and density and fecundity of staghorn colonies by measuring three
 variables for each colony: 1) colony density, 2) per capita fecundity and
 3) colony-level fecundity. These traits reflect information about colony
 health and spatial dynamics. Colony density was determined by dividing the
 total number of individuals by the colony’s volume
 (cm<sup>3</sup>) calculated via the product of width, height
 and depth measurements. To evaluate the fecundity-related
 parameters,<em> </em>we subdivided colonies into lower, middle
 and upper sections, reflecting differential reproductive patterns (Burns
 et al., 2021). From each section, three mature individuals were randomly
 selected, and the number of reproductive fronds were counted per
 individual following Burns et al. (2021). Per capita fecundity was then
 calculated by dividing the total number reproductive fronds by the number
 of assessed individuals (mostly nine, unless insufficient mature
 individuals were present). Lastly, colony-level fecundity was calculated
 by multiplying per capita fecundity by colony density. To expand our
 sample size of guest-inhabited colonies for analysing the relationship
 with their host, we also searched for colonies with guests off-track, in
 all accessible areas of dry forest. This approach allowed us to compile a
 dataset that likely encompasses most inhabited colonies on the
 island. To assess differences in colony density, per
 capita fecundity, and colony-level fecundity among colonies inhabited by
 different guest species or not inhabited at all, we conducted three
 one-way ANOVAs using R v.4.0.4 with the ‘car’ package. Subsequently, we
 performed post hoc Tukey HSD tests to identify significant mean
 differences between inhabited and uninhabited colonies. To investigate
 colony density variations between on- and off-track locations, we employed
 a Mann-Whitney U test from the R base package. Similar tests were applied
 to fecundity metrics. As the outcomes of these tests were not significant
 for most colonies (Figure S2), both on-track and off-track colonies were
 analysed together to answer the second research question. All data were
 tested for normality and transformed where necessary.
description: # Guests in Nests, dataset #### Dataset Overview This dataset encompasses
 observations from a field study conducted on Lord Howe Island, focusing on
 the interactions between various guest species and staghorn ferns
 (Platycerium bifurcatum), an epiphytic plant. The study explores the
 influence of guest species on the density and fecundity of staghorn
 colonies, which may exhibit features similar to eusociality in animals.
 #### Data Structure and Contents The dataset comprises 172 observations of
 staghorn fern colonies, collected along predefined tracks through the
 island's dry forest. Each entry includes the following parameters for
 each colony: 1. **Track Status (on/off)**: Indicates whether the colony
 was observed directly on the predefined track or off the track. 2. **Guest
 Type**: Specifies the type of guest species found within the colony,
 including native ferns and orchids. 3. **Number of Individuals (#ind)**:
 The total count of individual ferns within the colony. 4. **Volume
 (dm³)**: The calculated volume of the colony, derived from measurements of
 width, height, and depth (in cm). 5. **Colony Density**: Computed by
 dividing the number of individuals by the colony's volume, providing
 a density measure in individuals per cubic decimeter. 6. **Per Capita
 Fecundity**: The average number of reproductive fronds per individual
 within the colony. 7. **Colony Fecundity**: A product of per capita
 fecundity and colony density, indicating the total reproductive output of
 the colony. #### Usage Notes * **Potential Applications**: This dataset
 can serve as a basis for further research into plant social behavior,
 conservation efforts, or ecological studies of the relationship between
 different plant species. #### Additional Information * **Missing Data
 Codes**: The dataset uses 'non' to indicate no guests present. *
 **Abbreviations**: 'non' refers to no guest present; specific
 guest species are abbreviated: 'Zea.pus.' for *Zealandia
 pustulata*, Oph.pen. for *Ophioglossum pendulum*, Den.gra. for *Dendrobium
 gracilicaule*, Psi.nud. for *Psilotum nudum* and Fic.mac. for *Ficus
 macrophylla*.