DOI: 10.5061/dryad.sn02v6x6w
title: Functional diversity and trait filtering of insectivorous bats on forest islands created by an Amazonian mega dam

description: 1. Mega dams in lowland tropical forests often create large archipelagos,
 leading to biodiversity decay and disruption of ecosystem functioning in
 remnant habitat islands. 2. We investigated the functional diversity and
 functional trait filtering of aerial insectivorous bats in both insular
 forest patches created by a vast ~30-yr-old hydropower reservoir and the
 adjacent mainland continuous forest in Central Amazonia. 3. Bats were
 surveyed using passive bat recorders across 34 forest sites. Based on a
 set of morphological traits derived for each species recorded, we
 estimated both the bat functional richness, functional evenness and
 functional dispersion at each surveyed site. We further assessed the
 effects of local vegetation, patch and landscape features on patterns of
 functional diversity. The interaction between functional traits,
 environmental characteristics, and species distribution was investigated
 using a combination of RLQ and fourth-corner analyses. 4. We found that
 mainland sites retained higher functional richness and lower functional
 evenness compared to forest islands, indicating a more complete functional
 assemblage in the mainland. Additionally, species composition was affected
 by local vegetation structure and forest area, with small isolated islands
 exhibiting pervasive loss of functional traits. RLQ and fourth-corner
 analyses showed that larger understorey foraging species with greater
 dispersal capacity, constant frequency-frequency modulated calls, and
 higher frequency of maximum energy were associated with more isolated
 small islands. Conversely, forest subcanopy species, exhibiting
 quasi-constant frequency calls and presenting low dispersal capacity were
 associated with continuous forests and islands with greater forest area,
 and were therefore more sensitive to habitat insularization. 5. Our study
 calls attention to the pervasive impacts induced by large dams on the
 functional diversity of tropical insectivorous bats. We recommend that
 future assessments of the effects of habitat fragmentation on mammals
 should include traits linked to ecosystem services. In designing and
 licensing new dams, we suggest the creation of extensive protected areas
 surrounding mainland forests to minimize the detrimental impacts of small
 isolated islands and safeguard the full complement of key ecological
 functions provided by insectivorous bats.
description: Bat
 surveys Between July and November 2016, we sampled
 aerial insectivorous bats using a Song Meter 2 BAT+ ultrasound recorder,
 connected to an SMX-US ultrasonic omnidirectional microphone (Wildlife
 Acoustics, Maynard, Massachusetts) positioned 1.5 m above ground at the
 centre of each plot. Each recorder was programmed to operate from dusk to
 dawn (17:30h to 06:30h) for four consecutive nights, covering the activity
 period of all bat species. Thus, each plot was sampled for 52h for a total
 of 1,768 recorder-hours over 136 sampling nights. Each recorder was
 configured to passively record bat activity in real time. To improve the
 range and quality of the ultrasound pulse recordings, we set the sample
 rate to 384 kHz with 32-bit resolution and only sounds with 18 dB
 exceeding ambient noise were considered. Ultrasounds were saved in WAC
 format with 30-min, producing 26 files every 13 hours of recordings. Using
 the Kaleidoscope 4.0.3 program (Wildlife Acoustics, Maynard,
 Massachusetts), these files were converted into WAV format and subdivided
 into 5-sec files. Spectrograms with at least two echolocation pulses of a
 single species or phonic complexes (species with similar calls that cannot
 be confidently distinguished) in each 5-sec file were defined as a ‘bat
 pass’, and this is considered as the unit of measure for bat activity.
 This study was undertaken under licenses for scientific purposes from
 Instituto Chico Mendes de Conservação da Biodiversidade - ICMBio
 (#53340-1). As this study did not involve the bat capture, it did not
 require approval from an ethics committee.
 All recordings were inspected
 manually using the Kaleidoscope 4.0.3 program, and all species/phonic
 complexes were identified using the Amazonian bat ultrasound key sourced
 from López-Baucells et al. (2016). We separated <em>Pteronotus
 parnellii</em> into two sonotypes according to Pavan et al. (2018):
 <em>Pteronotus</em> 55 kHz = <em>P.
 rubiginosus</em> and <em>Pteronotus</em> 60 kHz =
 <em>P. alitonus</em>. <em>Eptesicus
 brasiliensis</em> and <em>E. chirichinus</em> were
 classified as a single phonic complex (<em>Eptesicus
 brasiliensis</em>/<em>chirichinus</em>) because of
 overlapping ultrasound characteristics (López-Baucells et al., 2016). We
 excluded all Phyllostomidae and Molossidae species from the analysis
 because these families cannot be reliably
 identified. Species traits
 We carefully selected seven
 functional traits that are widely used to assess the functional
 composition of bat assemblages across tropical forest landscapes,
 including two ultrasound characteristics (frequency of maximum energy and
 call structure), three body measurements (body mass, relative wing loading
 and aspect ratio), and vertical stratification of flight activity as a
 measure of forest habitat use. Environmental variables
 We used five local predictor
 variables to represent the floristic structure and vegetation clutter of
 each sampling site based on vegetation surveys within each of our forest
 plots. In particular, we assessed the (i) number of adult tree species
 (i.e., diameter at breast height ≥10 cm), (ii) number of adult tree stems
 (tree abundance), (iii) forest basal area, (iv) fire severity and (v)
 vegetation clutter. Variables (i) to (iv) were obtained from a previous
 study within the same forest plots (see Benchimol & Peres, 2015
 for further details). Fire severity was a categorical variable derived
 from the extent to which each island had been affected by fires during the
 El Niño drought of late 1997 to early 1998 (Benchimol & Peres,
 2015) and the number of charred trees and height of char marks on each
 tree; burnt islands have been regenerating and therefore we assume that
 fire severity can be a robust proxy for secondary vegetation. We further
 quantified vegetation clutter by placing 3 m × 3 m white panel sheets on
 each of the four sides of the recorder, which were photographed from 8 m
 (see Marciente et al., 2015). Using the ImageJ 1.8.0 software, we then
 thresholded these photos into black & white images, with black
 pixels representing the vegetation, and then estimated the mean proportion
 of vegetation from the four panels per plot.
 We also obtained four patch
 and landscape variables: (i) forest area (in hectares), (ii) the shortest
 distance from each survey island to the nearest continuous forest (in
 meters), (iii) shortest distance from the recorder to the edge of the
 islands and the mainland (in meters), and (iv) the amount of
 landscape-scale forest cover. We used RapidEye© high-resolution (5-m
 pixel) imagery of the Balbina archipelago to quantify the patch and
 landscape variables. Forest area was measured for islands and continuous
 forest. To assess forest area in continuous forests, we assigned a value
 ten-fold larger than our largest island of 1,690.04 ha, a widely used
 procedure in fragmented landscape studies to include continuous forests in
 the analyses (Benchimol & Peres, 2015). Forest cover around each
 island (i.e., old-growth and/or secondary vegetation in different stages
 of regeneration) was measured considering four different spatial scales
 (within a buffer radius of 500 m, 1000 m, 1500 m and 2000 m from each
 recorder), in order to cover the home range sizes of different aerial
 insectivorous bat species. We then obtained the proportion of forest cover
 within each landscape using the QGIS 2.18.14
 software. References
 Benchimol, M., & Peres, C. A. (2015). Predicting local extinctions of Amazonian
 vertebrates in forest islands created by a mega dam. Biological
 Conservation, 187, 61–72.
 http://dx.doi.org/10.1016/j.biocon.2015.04.005
 López-Baucells A., Rocha R., Bobrowiec P.E.D., Bernard E.,
 Palmeirim J. & Meyer C. (2016). Field guide to Amazonian bats (1st
 ed). Editora INPA. Marciente, R., Bobrowiec, P. E. D., &
 Magnusson, W. E. (2015). Ground-vegetation clutter affects phyllostomid
 bat assemblage structure in lowland Amazonian forest. PLoS ONE, 10(6),
 e0129560.
 https://doi.org/10.1371/journal.pone.0129560
 Pavan, A. C., Bobrowiec, P. E. D., & Percequillo, A. R.
 (2018). Geographic variation in a South American clade of mormoopid bats,
 Pteronotus (Phyllodia), with description of a new species. Journal of
 Mammalogy, 99(3), 624–645. https://DOI:10.1093/jmammal/gyy048