DOI: 10.5061/dryad.v82b7
title: Data from: Loss of animal seed dispersal increases extinction risk in a tropical tree species due to pervasive negative density dependence across life stages

description: Overhunting in tropical forests reduces populations of vertebrate seed
 dispersers. If reduced seed dispersal has a negative impact on tree
 population viability, overhunting could lead to altered forest structure
 and dynamics, including decreased biodiversity. However, empirical data
 showing decreased animal-dispersed tree abundance in overhunted forests
 contradict demographic models which predict minimal sensitivity of tree
 population growth rate to early life stages. One resolution to this
 discrepancy is that seed dispersal determines spatial aggregation, which
 could have demographic consequences for all life stages. We tested the
 impact of dispersal loss on population viability of a tropical tree
 species, Miliusa horsfieldii, currently dispersed by an intact community
 of large mammals in a Thai forest. We evaluated the effect of spatial
 aggregation for all tree life stages, from seeds to adult trees, and
 constructed simulation models to compare population viability with and
 without animal-mediated seed dispersal. In simulated populations,
 disperser loss increased spatial aggregation by fourfold, leading to
 increased negative density dependence across the life cycle and a 10-fold
 increase in the probability of extinction. Given that the majority of tree
 species in tropical forests are animal-dispersed, overhunting will
 potentially result in forests that are fundamentally different from those
 existing now.
description: Seedling growth and
 survivalThis file describes the
 growth and survival of individual Miliusa horsfieldii (Annonaceae)
 seedlings censused annually in 3 m x 3 m plots from 2009-2011. Column 1
 (PLOT_ID) is the unique identifier of each 3 m x 3 m plot, Column 2 (TAG)
 is the unique identifier of each seedling, Column 3 (HEIGHT_1) is the
 height (in cm) of each seedling during the first census, Column 4
 (HEIGHT_2) is the height (in cm) of each seedling during the second
 census, Column 5 (SURVIVAL) is the survival of seedlings from the first to
 the second census (1=alive, 0=dead), and CONSPECIFIC_seedlings is the
 count of conspecific seedlings in 1 m x 1 m quadrats containing the focal
 seedling. The 11 columns titled "DBH_1" to "DBH_11"
 are the DBH (in cm) of neighboring conspecific trees in a 20 m radius. The
 11 columns titled "DIS_1" to "DIS_11" are the distance
 (in m) of neighboring conspecific trees in a 20 m radius. "NA"
 values in the neighborhood matrices indicate 0 trees were
 present.SEEDLINGS.csvSeed germination from seed addition experimentData on seed germination of Miliusa horsfieldii collected using a seed addition experiment in 95 plots. In these plots, a total of 6,500 marked seeds were added in 3 piles of 5, 15 or 45 seeds during June-July 2009 and monitored for survival for three months, at which time all seeds had either germinated or died. Column 1 (PLOT) is the unique identifier of each seed addition plot, Column 2 (GERMINANTS) is the total number of seeds that successfully germinated, column 3 (TOTAL_ADDED) is the total number of seeds added to each pile, and CONSPECIFIC_SEEDLINGS is the count of conspecific seedlings in 1 m x 1 m quadrats containing the focal seed pile. The four columns titled "DBH_1" to "DBH_4" are the DBH (in cm) of neighboring conspecific trees in a 10 m radius. The four columns titled "DIS_1" to "DIS_4" are the distance (in m) of neighboring conspecific trees in a 10 m radius. "NA" values in the neighborhood matrices indicate 0 trees were present.SEEDS.csvFruit production as a function of tree sizeData on fruit production of Miliusa horsfieldii trees measured in June-July 2011. Fruits were counted in three 3 m x 3 m quadrats beneath 14 reproductive trees. Column 1 (FRUIT_COUNT) indicates the total number of fruits counted, Column 2 is the DBH of the focal tree (in cm) and Column 3 (TREE_ID) is a unique identifier for each individual tree.TREES.csvCounts of naturally-dispersed newly-established seedlingsData on counts of newly established Miliusa horsfieldii (Annonaceae) seedlings censused in 3 m x 3 m plots. Column 1 (PLOT_ID) is the unique identifier of each 3 m x 3 m plot, Column 2 (RECRUIT_COUNTS) is the count of newly recruited seedlings in each plot, Column 3 (CONSPECIFIC_seedlings) is the count of previously established conspecific seedlings in 1 m x 1 m quadrats containing the recruits. The 11 columns titled "DBH_1" to "DBH_11" are the DBH (in cm) of neighboring conspecific trees in a 20 m radius. The 11 columns titled "DIS_1" to "DIS_11" are the distance (in m) of neighboring conspecific trees in a 20 m radius. "NA" values in the neighborhood matrices indicate 0 trees were present.RECS.csv