Plant and frugivore species characteristics drive frugivore contributions to seed dispersal effectiveness in a hyper-diverse community
Data files
Oct 24, 2024 version files 21.98 MB
Abstract
Seed dispersal by frugivores is a crucial step of the life cycle of most plants, influencing plant population and community dynamics. Although very important for most ecosystems, we are just beginning to understand which are the mechanisms driving frugivore-mediated seed dispersal. Most studies identifying the drivers of seed dispersal use interaction frequency as a proxy for estimating seed dispersal success, rather than looking at the functional outcomes of those interactions (e.g., contributions to successful seed germination). A valuable tool to link plant-frugivore interactions to seed dispersal success is the seed dispersal effectiveness (SDE) framework, which accounts for the quantity and quality components of seed dispersal. We evaluated which mechanisms, including morphological traits, trait matching, and phenological overlap of interacting species, as well as the degree of frugivory and feeding behavior of frugivores, influenced the quantity (interaction frequency and number of seeds dispersed per visit) and quality (seed germination after gut passage) components of SDE. To this end, we combined three methods (focal observations, mist-netting, and camera traps) to sample interactions between plants, birds, and mammals in a species-rich community of Cerrado in southeastern Brazil. We recorded 590 pairwise interactions between 34 plants and 49 frugivores. We found that phenological overlap among interacting species explained most of the variation in interaction frequencies. Trait matching affected the number of seeds dispersed per visit more for gulpers than mashers and peckers, and frugivore body mass and seed sizes positively affected seed germination. Finally, interaction frequencies had a stronger contribution to SDE, compared to the number of seeds dispersed per visit and seed germination, indicating an indirect effect of phenological overlap on SDE. We found that highly abundant plant-frugivore species with the most overlap in their phenologies also yield the highest values of SDE, suggesting that phenological overlap was the most important driver of SDE in our community. However, the number of seeds dispersed per visit also influenced SDE and seed germination was species-specific, suggesting that estimating SDE at the community level is necessary to understand how communities work, and the current and future challenges they face.
README: Plant and frugivore species characteristics drive frugivore contributions to seed dispersal effectiveness in a hyper-diverse community
Access this dataset on Dryad in DOI:10.5061/dryad.2rbnzs7x6
This dataset gathers plant-frugivore interactions, with their respective interaction frequencies and number of seeds dispersed per visit by frugivores for 171 unique interactions between 34 plant and 49 frugivore species. It also contains seed germination probabilities and seed dispersal effectiveness (SDE) values for 38 unique interactions between 16 plants and 16 frugivore species.
The data shown here was recorded in 6 sites within a species-rich neotropical savanna, the Cerrado, located in Southeast Brazil. Because we wanted to assess whether different plant and frugivore species characteristics influenced frugivore contributions to seed dispersal effectiveness in our community, the dataset also has a number of different plant-frugivore characteristics likely to affect each of the subcomponents of SDE and ultimately SDE. Specifically, we evaluated the effects of plant and frugivore morphological traits (body mass and seed sizes), phenological overlap and trait matching of interacting species, as well as animal degree of frugivory and feeding behavior, on interaction frequencies, the number of seeds dispersed per visit (SDE quantity component) and seed germination (SDE quality component), identifying which drivers explained most variation in frugivore contributions to SDE.
Description
1.Dataset and 2.Partial_dataset
The "1.Dataset" contains the complete set of data with all 171 plant-frugivore interactions, while "2.Partial_dataset" contains the 38 interactions for which we had values of seed germination and SDE. Also, both datasets have all plant-frugivore characteristics used in the models described in the data analysis section of the research paper. Please note that interaction frequencies and trait-matching values may differ between the complete and the partial dataset since the calculation of those variables depends on the set of interactions used. Each row represents an interaction, and columns show:
plantSp: the scientific names of plant species recorded in the study.
animalSp: the scientific names of frugivore species recorded in the study.
temp_overlap: the number of months both plant and frugivore species were simultaneously present in the sites.
phe_overlap: degree of temporal overlap between plant and frugivore species based on the abundance of interacting species co-occurring in the same month. For each pair of plant-frugivore species, we selected the minimum relative abundance of the interacting pair each month. Then, we added all minimum relative abundances across all months for each pair of species (Pleasants, 1990).
trait_matching: a measure of how much plant and frugivore traits match. We used morphological plant and frugivore traits known to affect animal frugivory (gape/gullet size × fruit diameter, and fruit length × beak length; Dehling et al., 2014), and quantified trait matching of interacting partners using a multivariate trait congruence approach (Peralta, et al., 2020). To this end, we built a similarity matrix of morphological traits for plants and a similarity matrix of morphological traits for frugivore species using the Gower similarity coefficient (Gower, 1971) and the “vegdist” function from the vegan R package (Oksanen et al., 2022). Then, using the plant and frugivore trait similarity matrices and a binary species interaction matrix, we ran a Parafit test (Legendre et al., 2002) with the “parafit” function from the ape R package (Paradis et al., 2004). The Parafit test allowed us to assess whether frugivore species interact more frequently with plant species with similar traits, compared to a scenario where species interact randomly.
body_mass (kg): the body mass of frugivores in kilograms (kg). The data on body masses were obtained from bird captures with mist nets, and for the frugivore species that failed to be captured, we used databases (Wilman et al., 2014; Bello et al., 2017; Souza et al., 2019; Tobias et al., 2022). When bird and mammal body masses were available from more than one source, we calculated average values considering all sources.
gape_width (mm): the width of birds' beaks, and the width of mammals' mouths (i.e., gullet sizes; Fuzessy et al., 2022) in millimeters (mm). Gape widths and gullet sizes were obtained from bird captures with mist nets, databases (Wilman et al., 2014; Bello et al., 2017; Souza et al., 2019; Tobias et al., 2022), and measurements taken from museum specimens (3-10 individuals per species) at the USP Zoological Museum (MZUSP). When bird and mammal traits were available from more than one source, we calculated average values considering all sources.
beak_length (mm): the length of birds' beaks in millimeters (mm). Beak lengths were obtained from bird captures with mist nets, databases (Wilman et al., 2014; Bello et al., 2017; Souza et al., 2019; Tobias et al., 2022), and measurements taken from museum specimens (3-10 individuals per species) at the USP Zoological Museum (MZUSP). When beak lengths were available from more than one source, we calculated average values considering all sources. Beak length is unavailable for mammals and marked with NA, as we could not find a good substitute for this specific trait that applied to mammals.
behavior: frugivore feeding behavior, determined based on the most common behavior observed during interaction sampling. Specifically, for each plant-frugivore interaction, the frugivore was classified as a gulper when most of its feeding behavior toward the plant species consisted of swallowing entire fruits, as a masher when most fruits were crushed and mandibulated before ingestion, and as a pecker when the frugivore only pecked the fruit pulp without removing the seed (Levey, 1987; Moermond & Denslow, 1985).
degree_frugivory: percentages of fruits in frugivore diets. We extracted the percentages of fruits in frugivore diets from Wilman et al. (2014) for birds and, when available, from diet reports for mammals (Bueno & Motta-Junior, 2004; Gayot et al., 2004; Pedrosa et al., 2019; Rodrigues da Silva et al., 2014). As we could not find values of frugivory degree for all frugivore species, a few rows have NAs.
nseeds: the number of seeds contained inside fruits of each plant species. The number of seeds inside fruits was obtained from fruits collected in the study sites and are the rounded average values of 1-20 ripe fruits of 1-5 plant individuals of each species, according to their availability.
fruit_length (mm): the length of fruits in millimeters (mm). Fruit length was measured as the maximum distance between the base of the fruit (where it was attached to the plant) to the apex, using a caliper (Pérez-Harguindeguy et al., 2013).
fruit_diameter (mm): the diameter of fruits in millimeters (mm). Fruit diameter was measured as the maximum distance perpendicular to fruit length (considering how fruits were attached to the plant; Pérez-Harguindeguy et al., 2013).
seed_size (mm): the largest dimension of seeds, considering seed length, diameter, and height (Pérez-Harguindeguy et al., 2013), in millimeters (mm). The dimensions of seeds were obtained from fruits collected in the study sites and are the average values from 1-20 ripe fruits of 1-5 plant individuals of each species, according to their availability.
int_frequency: interaction frequency estimates for each pair of interacting species. Because we recorded plant-frugivore interactions using three different sampling methods (focal observations, captures with mist nets, and camera traps), we had to merge interaction frequencies using the grand total standardization method (Quintero et al., 2022). The grand total standardization approach transforms the interaction frequencies of each sampling method into the probability that a certain pairwise interaction will occur among all interactions sampled. To calculate it, we first weighted the number of interactions (i.e., visits) by dividing them by the corresponding effort in hours used to sample interactions for each method. Second, the values of each interaction frequency matrix were weighted by the total sum of interactions per hour recorded under each specific sampling method. Third, each interaction matrix was weighted by the sampling completeness corresponding to the specific sampling method. Once all matrices were weighted, we combined them to obtain a matrix representing species-interaction frequencies by calculating the average value for each pairwise interaction.
n_seeds_dispersed: the number of seeds dispersed per visit by frugivores for each pair of interacting species. When we recorded more than one interaction between the same pair of species, we calculated the average values of seeds being dispersed per visit. When we recorded only one interaction between a pair of species, we used the unique value of seeds dispersed in that specific visit.
seed_germination (only available in the partial dataset): the probability of seeds germinating after interactions. Those values were obtained from droppings collected from captured birds, droppings collected after fruit offering to captive birds of Turdus leucomelas, or droppings collected from easily identifiable frugivore species’ droppings in the field, i.e., when we saw the frugivore defecating or when feces were very characteristic of a certain animal species. Unfortunately, we were not able to estimate seed germination values for all of the recorded interactions, so this variable was only available in the partial dataset for unique 38 interactions.
SDE (only available in the partial dataset): seed dispersal effectiveness values, i.e., the product of interaction frequencies, number of seeds dispersed per visit, and seed germination values. Because seed germination was only available for a subset of interactions, SDE is also only available in the partial dataset for 38 unique interactions.
3.Data_seed_germ
This dataset contains the raw seed germination data for seeds immersed in pulp (i.e., whole fruits), manually de-pulped (i.e., de-pulped), and passing through the guts of frugivores (i.e., gut passed). “AnimalSp” column is specific for gut-passed seeds and specifies the animal species interacting with the seed. Seeds and fruits were sowed in Petri dishes (9 cm diameter each) according to treatment (gut-passed, manually-depulped, and whole fruits). The number of seeds and fruits in each Petri dish depended on their sizes. For small seeds (< 2 mm long), we included up to 300 seeds in each Petri dish, whereas for large seeds (> 2 mm long), we included 10 to 30 seeds per Petri dish. For fruits, we followed the same logic, including from 5 to 20 fruits per Petri dish, depending on fruit size. Petri dishes were stored in germination chambers set at 27 ° C and 12-12 dark-light hours and watered every 2–3 days. We considered a germination event when a seed showed the protrusion of the radicle. Seeds and fruits remained in germination chambers until seeds germinated or for a maximum of 6 months. Each row of this table represents an event when seeds were sowed into a petri dish, or in the case of gut-passed seeds, seeds contained in a single fecal sample from a single individual.
PlantSp: the scientific names of the plant species from which seeds were sowed.
Treatment: the treatment received by seeds. They could be seeds immersed in pulp (i.e., whole_fruit), seeds manually de-pulped (i.e., de-pulped), and seeds passing through the guts of frugivores (i.e., gut_passed).
AnimalSp: for seeds passing through the guts of frugivores, this column specifies frugivore species by their scientific names. NA rows here refer to treatments different from "gut_passed".
Seeded: the number of seeds sowed for each specific treatment into Petri dishes.
Germinated: the number of seeds that germinated after being sowed into Petri dishes.
Proportion: the proportion of seeds that germinated from the total of seeds sowed.
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