DOI: 10.5061/dryad.p2ngf1vqk
title: Data collected for paper: Ecological drivers of intraspecific variation in seed dispersal services of a common neotropical palm

description: Through frugivory and seed dispersal, vertebrates influence plant
 demography and forest regeneration. Variation in local habitat surrounding
 fruiting plants can influence frugivore foraging decisions, thereby
 creating intraspecific variation in seed dispersal services. However, we
 have little knowledge of drivers of local variation in frugivory. Here, we
 investigate factors that may influence frugivore diversity and fruit
 removal at the level of individual plants. We focus on a common understory
 palm within a continuous Chocó forest with mixed land-use histories in
 Ecuador. The density of pioneer tree species in the genus Cecropia around
 focal palms was negatively related to fruit removal and the diversity of
 frugivores visiting palms. This may relate to the fact that the presence
 and abundance of Cecropia species often indicate the existence and
 severity of past disturbances. Local Cecropia density was also related to
 an overall shift in the frugivore community that corresponded with an
 increase in fruit removal by lower-quality seed dispersers (rodents). We
 also found that the local density of fruiting conspecifics was positively
 related to frugivore diversity, but not fruit removal. Our results provide
 information on drivers of intraspecific inequalities in plant populations
 across tropical forest landscapes. The reduction in fruit removal and
 frugivore diversity associated with local Cecropia abundance suggests that
 seed dispersal services can be sensitive to fine-scale variation in
 habitat structure. Furthermore, because Cecropia are often indicative of
 past disturbances, this indicates that even small-scale habitat
 degradation by humans can have lasting effects by creating localized
 pockets of forest unfavored by frugivores.
description: <b>Study
 system</b> Our study was conducted at Bilsa
 Biological Station in northwest Ecuador (79”45’W, 0”22’N; 350-750 m
 elevation; 2-3 m precipitation annually), a 3500-ha private reserve of
 humid evergreen rainforest located within the Chocó biogeographic region
 (Durães <i>et al.</i> 2013). The Chocó forest has
 exceptionally high levels of endemism in both plant and animal species and
 is recognized as one of the most biologically diverse regions on the
 planet (Myers <i>et al.</i> 2000). The study area consists of
 continuous forest that is composed of a complex matrix of undisturbed
 forest with patches of varying size that have been regenerating naturally
 for the past 24-34 years after selective logging and small-scale farming
 (Durães <i>et al.</i> 2013). Our focal plant species,
 <i>Prestoea decurrens </i>(Arecaceae) is a monoecious,
 insect-pollinated understory palm that is common in our study area (Browne
 & Karubian 2016) and throughout lowland tropical forests ranging
 from Bolivia to Nicaragua (Ervick & Bernal 1996, Steege
 <i>et al.</i> 2013). The palm is clonal, and individuals form
 distinct clusters of stems with a mean height of approximately 4 m (± 1.4
 standard deviation (SD), N = 252).  <i>Prestoea decurrens
 </i>produces fleshy animal-dispersed fruit 2-3 cm in diameter, with
 a purple epicarp, that contain a single seed measuring 6-7 mm in diameter.
 Fruits are arrayed on infructescences, each holding approximately 100-600
 fruits, and individual trees may hold up to six separate infructescences
 concurrently (unpublished data). We selected this focal palm species
 because it is a widespread and abundant fruiting resource in the
 understory environment and important for many frugivores across a large
 proportion of neotropical forests. The size and characteristics of
 <i>P. decurrens</i> fruits are common among many tropical
 plants, which makes it possible to extrapolate relevant information from
 our results into a broader context across tropical forests.
 <b>Frugivore observations</b>
 We deployed camera traps on
 31 fruiting <i>P. decurrens</i> palms located across
 approximately 40 ha of continuous, but heterogeneous, forest in Bilsa from
 August-November 2018, a period that coincided with high fruit production
 in this species (J. Karubian, <i>unpublished data).</i> We
 selected focal palms with mature fruits in locations that represented the
 spectrum of past-habitat use found in the 130-ha study area. Focal palms
 were geolocated by GPS (Garmin model 64s, Atchison, KS, USA) with 3-7
 meters accuracy. We deployed Browning Strike Force® HD motion-sensor trail
 cameras (2014 and 2018 models) with nighttime capability in front of the
 mature infructescences of each palm. In most cases (all but 2), all mature
 infructescences on an individual palm were included in the camera frame,
 generally 1-3 infructescences. Palms were located in most cases before
 fruits were ripe, and cameras were installed once fruits ripened. A small
 proportion of focal palms were already ripe when found, and camera traps
 were immediately set in front of them. Palm crop size was estimated for
 each infructescence by counting the number of fruits on 3 rachilla,
 averaging them, and multiplying the average by the number of rachilla on
 an infructescence, then summing the estimate for all infructescences on a
 given palm. Cameras were deployed for
 approximately 25 days or until all fruits were removed. Cameras were
 programed to capture 30-second videos with a 5-second delay between videos
 and as such recorded most or all visitation events during the sampling
 period. Because the maximum continuous recording time allowed by our
 cameras was only a few minutes, we did not have the ability to record and
 compare the full length of foraging events by frugivores. However, we can
 draw conclusions about relative rates and visitation frequencies through
 our 30-second capture method. Visitors were identified to the
 species level, using Ridgely and Greenfield (2001) <i>The Birds of
 Ecuador </i>and Tirira, (2017) <i>A field guide to the mammals
 of Ecuador</i>. The majority of the toucans we recorded were Chocó
 toucans (<i>Ramphastos brevis);</i> however,
 Chestnut-mandibled toucans (<i>R. swainsonii</i>) are also
 common in the area and due to the
 similarity in appearance we categorize these birds broadly as ‘toucans’
 here. We recorded the number of fruits handled, removed, or
 dropped by each visitor in each video. We summed the total fruit removed
 from each focal palm and calculated the mean percentage of overall fruit
 removal that each frugivore species contributed. We also calculated for
 each frugivore species the mean percentage of fruit it swallowed/carried
 away versus dropped (which can provide information on disperser
 quality). <b>Local habitat
 characterization </b> To understand
 how local habitat might influence visitation and fruit removal, we
 selected habitat metrics known to influence frugivore habitat use at this
 site: (Durães <i>et al.</i> 2013, Mahoney <i>et
 al.</i> 2018): canopy density, canopy height, the number of large
 trees ( &gt; 50 cm diameter at breast height (DBH)) within 20 m of
 each focal palm, the number of trees belonging to the genus
 <i>Cecropia </i>within 10 m of each focal palm, and the
 presence of conspecifics fruiting in the understory within 20 m of focal
 palms. Variation in neighborhood fruit availability was estimated by
 counting conspecifics because <i>P. decurrens </i>was the only
 observed fruiting plant in the understory near focal plants during the
 study period. We recorded <i>Cecropia</i> species abundance
 because these prevalent neotropical pioneer trees indicate past
 disturbance (Mesquita <i>et al.</i> 2001, Zalamea <i>et
 al.</i> 2008, 2012). We estimated canopy density as percentage
 canopy cover using a spherical densiometer (Forestry Supplies no. 43888),
 and canopy cover measurements were taken 0.5 m from the base of the focal
 palm in each cardinal direction and averaged. Canopy density, as well as
 canopy height and the presence of large trees, are typically attributed to
 lower disturbance levels. We quantified canopy height as the tallest tree
 within 10 m around the focal palm; this height was estimated individually
 by the same two observers for each palm and averaged.