DOI: 10.5061/dryad.9cnp5hqkt
title: The joint effects of forest habitat area and fragmentation on Dung beetles

description: Habitat loss and habitat fragmentation usually occur together, at the same
 time and place.  However, while there is consensus that habitat
 loss is the preeminent threat to biodiversity, the effects of
 fragmentation are contentious.  Some argue that habitat
 fragmentation is not bad for biodiversity, and even that it is
 good.  Generally, the studies that find no harm or positive
 outcomes of fragmentation invariably assume that it is independent of
 habitat loss.  However, dissociating the effects of habitat
 fragmentation from habitat loss is questionable because the two are
 essentially coupled.  Accordingly, we evaluated how forest area
 and fragmentation (via edge effects) influenced dung beetles per se, and
 through their effects on the abundance of mammals, using structural
 equation modeling (SEM).  Dung beetles are very sensitive to
 forest habitat loss and fragmentation, and to changes in the abundance of
 mammals on which they depend for dung.  Our study area was in the
 Tana River, Kenya, where forest fragments are depauperated of mammals
 except for two endemic species of monkeys.  We mapped 12 forests,
 counted the resident monkeys, and sampled 113,955 beetles from 288
 plots.  Most of the 87 species of beetles found were small
 tunnellers.  After implementing a fully latent Structural
 Regression SEM, the optimal model explained a significant 26% of the
 variance in abundance, and 89% of diversity.  The main drivers of
 beetle abundance were positive, direct, effects of forest area and number
 of monkeys, and negative edge effects.  The main drivers of
 diversity were the direct effects of the beetle abundance, indirect
 effects of forest area and abundance of mammals, and indirect negative
 edge effects.  Thus forest area, fragmentation (via edge
 effects), and the number of monkeys jointly influenced the abundance and
 diversity of the beetles directly and indirectly.
description: # The joint effects of forest habitat area and fragmentation on Dung
 beetles ## Columns A to AA
 contain the covariates associated with each plot (plotID) Each row
 represents a plot, 5 pitfalls combined constituting one visit to one
 sampling station on one of the six sampling periods All data are original
 measurements, i.e. not transformed for normality. * abdist2matrix.m,
 Distance of the plot to the matrix in meters * allIndividuals, sum of all
 individuals of all species in the five pitfalls from the same plot *
 asy.Hill.q0, asymptotic species richness for this plot * asy.Hill.q1,
 asymptotic Shannon diversity for this plot * basA, basal area of trees in
 the plot in square centimeters * cent2matrix, centrod distance to matrix
 in meters * colo.mang.grp, colobus and mangabey groups in the forest where
 this plot was located * colo.mang.inds, number of colobus and mangabeys in
 the forest where this plot was located" * comb.area, area of forest
 fragment (m2) * comb.area.perim, area-perimeter ratio * comb.perim,
 perimeter of forest fragment (m) * cutbasA, basal area of cut stems in the
 plot in square centimeters * east.west, location of plot on the east or
 west bank of the Tana River * forest, an identifier-name-for each forest
 fragment * Hill.q0, species richness (reference sample) * Hill.q1,
 exponential of Shannon diversity index (reference sample)) * larg.mg, mass
 of large sized beetles in this plot in milligrams * mang.grp, number of
 mangabey groups in the forest where this plot was located * mang.inds,
 number mangabeys in the forest where this plot was located * med.mg, mass
 of medium beetles (milligrams) * NA, stands for ""Not
 Available"" representing a missing value * plotID, beetle
 sampling plot accounting for year and month sampled * samp.month, an
 identifier for the month samples were taken * transectID, an identifier
 for each transect in each forest fragment * tunn.mg, mass of tunnelling
 beetles (milligrams) * utm.x, eastings UTM coordinates of forest fragment
 * utm.y, northings UTM coordinates for forest fragment * year, an
 identifier for the year the samples were taken