RESEARCH ARTICLE

Primate Extirpation From Rainforest Fragments Does Not Appear to InfluenceSeedling Recruitment

OSCARM M. CHAVES1*, VÍCTOR ARROYO-RODRÍGUEZ2, MIGUEL MARTÍNEZ-RAMOS2,AND KATHRYNE E. STONER3

1Departamento de Biodiversidade e Ecologia, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), PortoAlegre, Rio Grande do Sul, Brazil2Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Morelia, Michoacán, Mexico3Department of Fish, Wildlife and Conservation Ecology, New Mexico State University, Las Cruces, New Mexico

Primates are important seed dispersers, especially of large-seeded tree species, but the impact thatthese animals have on seedling recruitment is unclear. Evidence suggests that forest regenerationmight be disrupted in forest fragments in which primates were extirpated.We tested this hypothesis byassessing seedling recruitment in 3 forest fragments occupied (OF) by primates, 3 fragmentsunoccupied (UF) by primates, and 3 areas within a continuous forest (CF) in the Lacandona rainforest,Mexico. Species and stem densities of tree, palm and liana seedlings were recorded over 16 months.Individuals were classified according to dispersal mode: large-seeded animal-dispersed (LS), small- andmedium-seeded animal-dispersed (SS), and abiotically-dispersed species (AD). We assessed theinfluence of primate presence, adult tree assemblage, and fragment spatial metrics (size, age, distanceto nearest fragment, and distance to continuous forest) on seedling assemblages. We recorded 6879seedlings belonging to 90 species, and 59 genera in 405 1-m2 plots. Both seedlings and adults showedsimilar differences in species and stem densities of LS, SS and AD species among forest types,suggesting that seedling assemblages were strongly influenced by the adult assemblages. Therecruitment of each LS species varied among study sites, but evidence supporting higher recruitmentenhancement of these species in continuous forest and occupied fragments was weak. Distance tocontinuous forest was the unique fragment spatial metric related (negatively) to the recruitment of LSspecies. Thus, primate extirpation does not appear to disrupt seedling assemblages in the Lancandonarainforest. Nevertheless, we cannot reject the hypothesis that certain LS species such as Spondiasradlkoferi may be affected by the extirpation of primates. Am. J. Primatol. © 2014 Wiley Periodicals, Inc.

Key words: Ateles geoffroyi; Alouatta pigra; defaunation; forest regeneration; seed dispersal

INTRODUCTIONTropical deforestation has resulted in the popu-

lation decline and local extirpation of many frugivo-rous vertebrates [Canale et al., 2012; Terborgh et al.,2008; Wright et al., 2007], including several primatespecies [Arroyo-Rodríguez&Dias, 2009;Marsh et al.,2013; Ramos-Fernández & Wallace, 2008]. Thisdefaunation process [sensu Dirzo et al., 2014] cannegatively impact seed dispersal [Galetti & Dirzo,2013; Markl et al., 2012; Melo et al., 2006] and forestregeneration [Effiom et al., 2013,2014; Galetti et al.,2013; Stoner et al., 2007; Wotton & Kelly, 2011], asmost woody plant species in tropical forests aredispersed by vertebrates [Fleming et al., 1987].

Seed dispersal and its effect on seedlingassemblages are largely influenced by the morpho-logical characteristics of both vertebrates andfruits[Janson, 1983]. Overall, there is an inverse

relationship between the number of dispersers andseed sizes, due to the mechanical and physicalconstraints derived from fruit and seed handling[Jordano, 1995]. Whereas a wide assemblage ofdispersers can handle (and potentially swallow

Contract grant sponsor: Consejo Nacional de Ciencia yTecnología; contract grant numbers: CB2005-C01-51043,CB2006-56799.Conflicts of interest: None

�Correspondence to: Óscar M. Chaves, Departamento deBiodiversidade e Ecologia, Pontifícia Universidade Católica doRio Grande do Sul, Porto Alegre, 90619–900 Rio Grande do Sul,Brazil. E-mail: ochaba@gmail.com

Received 20 June 2014; revised 2 November 2014; revisionaccepted 3 November 2014

DOI: 10.1002/ajp.22364Published online XX Month Year in Wiley Online Library(wileyonlinelibrary.com).

American Journal of Primatology

© 2014 Wiley Periodicals, Inc.

and disperse) small seeds, larger seeds of fleshy-fruit tree species might be more vulnerable todispersal failure because they depend primarily ona small group of specialized dispersers [Donattiet al., 2007; Galetti et al., 2013; Markl et al., 2012],such as large primates [reviewed by Russo &Chapman, 2011].

In the Neotropics, Atelinae primates are con-sidered effective seed dispersers. For plant specieswith large seeds and/or with hard indehiscenthusks, these animals are probably the only primarydispersal agent [Arroyo-Rodríguez et al., 2015;Chaves et al., 2011; González-Zamora et al., 2014;Levi & Peres, 2013; Stevenson et al., 2005]. This isbecause of the limited ability of smaller frugivorousanimals (e.g. bats and avian frugivores) to trans-port large seeds and/or to open fruits protected withhard indehiscent husks [Janson, 1983]. This is thecase of many species within the Sapotaceae,Fabaceae and Rubiaceae families (e.g. Pouteria,Inga, Genipa, Posoqueria), which are frequentlydispersed by large primates, such as howlermonkeys [reviewed by Arroyo-Rodríguez et al.,2015] and spider monkeys [Chaves et al., 2011;González-Zamora et al., 2014; Levi & Peres, 2013].Nevertheless, these primates are highly threatenedby habitat loss and hunting [Arroyo-Rodríguez &Dias, 2009; Canale et al., 2012; Peres & Palacios,2007; Ramos-Fernández & Wallace, 2008], poten-tially limiting seed dispersal and forest regenera-tion in human-dominated landscapes.

Several studies suggest that primate extirpationcan negatively affect seedling recruitment [Anzures-Dadda et al., 2011; Chapman & Onderdonk, 1998;González-Di Pierro et al., 2011; Marsh & Loiselle,2003]. For example, in Kibale National Park,Uganda, fragments where primates have beenextirpated have a lower density of seedlings andfewer species than areas with an intact frugivorecommunity [Chapman & Onderdonk, 1936]. Theyalso report that the seedling assemblage in frag-ments without primates is dominated by a greaterproportion of small-seeded species. Similarly, Meloet al. [2010] found that large-seeded species tendto be poorly represented in fragments unoccupiedby primates and other mid-sized and large-sized vertebrates. Analyses at the population levelalso demonstrate a lack of recruitment of severalspecies dispersed by howler monkeys in fragmentsunoccupied by these primates when comparedwith fragments occupied by howlers [Anzures-Dadda et al., 2011; Marsh & Loiselle, 2003].Nevertheless, seedling recruitment can also dependon other local factors, such as the diversity andcomposition of adult tree assemblages, and fragmentspatial metrics such as fragment size, age, andisolation level [Bennett & Saunders, 2010; Laurance,2005]. To test the impact of primates on seedlingrecruitment, the effects of all of these confoundingT

ABLEI.

Description

ofStudySites

intheLacan

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Site

Size(ha)

Location

(geographiccoordinates)

Distanceto

nearest

fragment(m

)Distanceto

continuous

forest(m

)YSF/YSEa,b

Continu

ousforest

300,000

CF1

16°09’32.0“N,90°54’06.6“W

500

0—

CF2

16°06’58.2“N,90°56’18.4“W

400

0—

CF3

16°09’40.0“N,90°54’04.5“W

810

0—

Occupiedfragments

OF1

1416°19’52.0“N,90°51’06.1“W

950

490

31OF2

3116°19’24.5“N,90°50’43.7“W

200

1270

31OF3

1125

16°15’12.2“N,90°49’59.5“W

100

1700

33Unoccupiedfragments

UF1

6.4

16°06’39.5“N,90°56’04.6“W

200

150

19/15

UF2

11.4

16°06’15.7“N,90°55’34.9“W

160

1400

25/22

UF3

2816°06’02.0“N,90°56’03.7“W

125

990

17/16

aYearssincefragmentation.

bYearssinceprimateextirpation.

Am. J. Primatol.

2 / Chaves et al.

factors need to be assessed simultaneously orcontrolled.

Here we tested the hypothesis that forest regen-eration is disrupted in fragments unoccupied byprimates (i.e. black howler monkeys, Alouatta pigra;and spider monkeys, Ateles geoffroyi) in the Lacan-dona region in southern Mexico, as the local extirpa-tion of these seed dispersers is expected to limit therecruitment of animal-dispersed species, particularlythose with large seeds. The Lacandona region is anappropriate area to assess this hypothesis becauseboth fragment isolation and disappearance of pri-mates occurred recently (see Methods) and hence,large-seeded species mainly dispersed by theseanimals should still be present. We sampled adulttree and seedling species in 3 fragments occupied byprimates (OF), 3 fragments unoccupied by primates(UF), and 3 reference areaswithin a continuous forest(CF) in the Lacandona rainforest in Mexico to test ifspecies and stem densities of both seedlings and adulttrees differed among forest types. This analysis wasdone for the whole assemblage, as well as for eachdispersal mode separately: large-seeded (LS), small-

and medium-seeded (SS), and abiotically-dispersedspecies (AD).We then tested if the recruitment of eachLS species was lower (i.e. limited), higher (i.e.enhanced) or similar (i.e. neutral) to that expectedby the abundance of adult trees. Finally,we evaluatedthe influence of fragment size, age, distance to nearestfragment, anddistance to continuous forest on speciesdensity (i.e. number of species/sampled area) andstem density of seedlings within each dispersal mode.

If primate extirpation in the Lacandona rain-forest negatively affects seedling recruitment, wepredict that: (i) species and stem densities in theseedling bank will be higher in CF and OF than inUF, particularly when considering LS species, butthis pattern will not occur for adult trees; (ii) therecruitment of LS species will be higher thanexpected by the abundance of adult trees in CF andOF, while in UF recruitment of these species will belimited or neutral. Finally, since fragment spatialmetrics often influence forest regeneration (seeabove), we also expect that (iii) at least some ofthese metrics will be related to seedling assemblagesin each dispersal mode.

TABLE II. Top Ten Seedling Species Found in Three Continuous Forest Areas, Three Fragments Occupied byPrimates and Three Fragments Unoccupied by Primates in the Lacandona Rainforest, Mexico

Forest condition Plant species Family Life form Dispersal mode Abundance (%)

Continuous forest Ampelocera hottlei Ulmaceae Tree LS 32.8Castilla elastica Moraceae Tree SS 15.1Brosimum alicastrum Moraceae Tree LS 12.3Virola guatemalensis Myristicaceae Tree LS 6.7Guarea glabra Meliaceae Tree SS 5.6Lysiloma acapulcense Fabaceae Tree AD 3Dialium guianense Fabaceae Tree SS 2.3Celtis iguanaea Cannabaceae Vine SS 2.2Abuta panamensis Menispermaceae Vine LS 1.8Inga pavoniana Fabaceae Tree SS 1.4

Occupied fragments Inga punctata Fabaceae Tree SS 22.1Brosimum alicastrum Moraceae Tree LS 17.7Castilla elastica Moraceae Tree SS 11.1Guarea glabra Meliaceae Tree SS 10.4Dialium guianense Fabaceae Tree SS 6.3Brosimum lactescens Moraceae Tree SS 3.4Nectandra reticulata Lauraceae Tree SS 2.4Paullinia costata Sapindaceae Vine SS 2.2Spondias radlkoferi Anacardiaceae Tree LS 1.9Posoqueria latifolia Rubiaceae Tree LS 1.8

Unoccupied fragments Licania hypoleuca Chrysobalanaceae Tree AD 20.8Brosimum alicastrum Moraceae Tree LS 17.1Vochysia guatemalensis Vochisiaceae Tree AD 16.2Brosimum lactescens Moraceae Tree SS 12.6Xylopia frutescens Annonaceae Shrub SS 4.6Inga vera Fabaceae Tree LS 3.7Ampelocera hottlei Ulmaceae Tree LS 2.1Hirtella americana Chrysobalanaceae Tree SS 1.9Pseudolmedia glabrata Moraceae Tree SS 1.9Vatairea lundellii Fabaceae Tree AD 1.8

LS, Large-seeded animal-dispersed species; SS, small- and medium-seeded animal-dispersed species; AD, abiotically-dispersed species. The life form anddispersal mode of each species are indicated. Species are ordered according to the relative abundance of individuals.

Am. J. Primatol.

Primate Extirpation from Seedling Recruitment / 3

METHODSStudy Area and Sites

A detailed description of the study area and siteshas been reported elsewhere [Chaves et al., 20112012] so only a brief overview is given here.Fieldwork was conducted during a 16-month periodin 2007 (January–June, August–November) and2008(February-May, July-September) in the Lacan-dona rainforest, southern Chiapas, Mexico (16°05’58“N, 90°52’36“ W; elevation 10–50m.a.s.l.). Weworked in two adjacent areas separated by theLacantún river: the Marqués de Comillas region(MCR, eastern side of the river), and the MontesAzules Biosphere Reserve (MABR, western side).Human colonization ofMCRbegan in 1960 [Mendoza& Dirzo, 1999], and resulted in the rapid disappear-ance and fragmentation of the forest. Approximately50% of the land surface of MCR is nowadays used foragricultural purposes, but small and large forestfragments (0.5 to >1,000ha) still remain in the area.The protected area ofMABRwas created in 1978 andconsists of approximately 3000 km2 of relativelyundisturbed forest.

We selected 9 sites, 3 areas within thecontinuous forest (CF) of MABR separated by atleast 4 km from each other, 3 forest fragmentsoccupied by primates (OF), and 3 fragmentsunoccupied by primates (UF) (Table I). Bothblack-handed spider monkeys (Ateles geoffroyivellerosus) and black howler monkeys (Alouattapigra) are present in CF and OF, whereas UFs havebeen unoccupied by primates for at least 15 yr(Table I). Fragments were isolated �17 yr ago andduring this study and our previous studies in thesame area [Chaves et al., 2011 2012] we did notobserve movements of primates among OF and UFfragments or between these fragments and thecontinuous forest. Additionally, even when UF1was 150m from the continuous forest, we neverobserved primates or traces of them (e.g. feces,hairs, bones) in this fragment or in UF2 and UF3.Overall, the anthropogenic matrix around OF andUF fragments was composed of small forestremnants (i.e. secondary successional forests rang-ing from 0.5 to 25 ha in size), cattle pastures,agricultural lands devoted to chili peppers and/orcorn crops, and isolated human settlements. Cattle

Fig. 1. Density of individuals and species (mean�SD) of adult trees (left panels) and seedlings (right panels) according to the dispersalmode in each habitat type. Different letters indicate significant differences among habitat types (contrast tests, P<0.05 in all cases).Large-seeded animal-dispersed species (LS), small- and medium-seeded animal-dispersed species (SS), and abiotically-dispersedspecies (AD).

Am. J. Primatol.

4 / Chaves et al.

cannot enter in most of the study fragments becauseof the presence of fences, but occasionally somecows entered the unoccupied fragments UF2 andUF3 to drink water during the dry season. Howev-er, our observations showed that cattle used well-marked trails that led straight to the water andthey basically walked to the water, drank, and thenreturned to the pasture. We never found experi-mental plots destroyed by cattle, nor any cowfootprints near them. To limit the interference ofcattle in these two fragments we placed the

experimental plots 40–200m from the trails.Finally, to minimize the potential effect of fragmentsize in our results we standardized the samplingeffort in each study site as described below.

Primates in the Study AreaTwo primate species occur in the area: Ateles

geoffroyi vellerosus andAlouatta pigra.A. geoffroyi isdistributed from the state of Veracruz, Mexico,throughout most of Central America and the ChocóRegion of the Pacific coast of South America tonorthern Ecuador. It is a fruit specialist with ripefruits accounting for more than 70% of its feedingtime [González-Zamora et al., 2009; van Roosmalen& Klein, 1988]. A. pigra is endemic to southernMexico, Belize, andGuatemala [Rylands et al., 2006],and devotes as much as 50% of their feeding timeconsuming fruits [Pavelka&Knopff, 2004]. InMABRthe population density of A. geoffroyi is estimated as2.9 ind./km2, while that for A. pigra is 14.4 ind./km2

[Estrada et al., 2004]. Both primate species arecurrently classified as endangered throughout theirgeographic range due to human disturbances such asdeforestation, habitat loss, and hunting [IUCN,2013]. This study satisfied the legal requirementsof the Mexican Secretary of Environmental andNatural Resources (SEMARNAT) and meets all theMexican animal care policies and the Principles ofthe American Society of Primatologists for theEthical Treatment of Nonhuman Primates.

Seedling AssemblagesWe sampled seedling assemblages (i.e. young

trees, palms, and lianas 5–100 cm tall and <1 cm indiameter) in ground-level grids composed of 3 trans-ects with 5 1-m2 plots placed alternately at both sidesof each transect (Fig. S1). In each study site weestablished 3 grids separated by at least 30m fromeach other and a total of 45 1-m2 plots (Fig. S1). Gridswere located within forest interiors (i.e. >100m fromforest edge) to minimize confounding edge effects[Laurance et al., 2002, 2006] andbecause ourprevious15-month study on the diet of spider monkeysindicates that in these areas monkeys concentrate>80%of their feeding time [Chaves et al., 2011, 2012].Howlermonkeys were also observed foraging in theseareas during the study period. Due to the absence oftaxonomic guides on liana seedlings of Lacandona, weonly sampled some commonand conspicuous lianas inthe study area that could be unequivocally identified,such as Celtis iguanaea, Abuta panamensis, andPaullinia costata. To quantify recruitment, all re-corded seedlings were marked with individuallynumbered aluminum tags, and plots were surveyedevery 3 months during a 16-month period. We usednumeric tags todifferentiatenewrecruits and identifyeach seedling.

Fig. 2. Electivity values (Chesson’s e) for seedlings of four largeseeded animal dispersed species in the Lacandona rainforest,southern Mexico. When the index value is 0, recruitment do notdiffer than expected by the abundance of adult trees, negativevalues indicate recruitment limitation, and positive valuesindicate higher recruitment than expected. CF ¼ continuousforest sites, OF ¼ forest fragments occupied by primates, andUF ¼ forest fragments unoccupied by primates.

Am. J. Primatol.

Primate Extirpation from Seedling Recruitment / 5

We classified seedling species according to theirfruit traits, seed size, and seed dispersal mode into3 categories: large-seeded animal-dispersed (LS),small- and medium-seeded animal-dispersed (SS),and abiotically-dispersed (AD) species. LS speciesincluded four fleshy fruit species with seeds�10mm in length, which are intensely consumedand defecated by primates in the study area[Table S1; Chaves et al., 2011; González-Di Pierro,2011; González-Zamora et al., 2014]. Primates areprobably the main seed dispersers of these speciesbecause: (i) these species are absent in the seed raingenerated by birds and bats in southern Mexico[Galindo-Gonzalez et al., 2000; Peña-Domene et al.,2014]; (ii) during 1010hr of behavioral observationsof primates in the region [Chaves et al., 2011, 2012]we never observed birds or other vertebrates (withthe exception of primates) feeding on these fruits;and (iii) although other large terrestrial mammalssuch as Dicotyles pecari, Odocoileus virginianus,and Agouti paca can swallow (and eventuallydisperse) these seeds, they can also be importantseed predators [Beck et al., 2013; Kuprewicz, 2013].SS species included fleshy fruit species with small(<1–3mm in length), and medium seeds (>3–9mm)dispersed by a wide assemblage of frugivores suchas primates [Chaves et al., 2011], birds, and bats[Galindo-Gonzalez et al., 2000; Peña-Domene et al.,2014]. Finally, AD species included dry fruit treespecies reported as dispersed by wind, water orgravity in southern Mexico [Ibarra-Manríquezet al., 1997].

We determined the adult tree composition (i.e.trees >10 cm in diameter at breast height) in thesame areas in which we sampled seedlings. To dothis, we randomly fixed ten 50� 2m linear transectsin each study site (excluding forest edges), for a totalof 90 linear transects [further details inChaves et al.,2012].

Species were identified in situ with the collabo-ration of an experienced local para-taxonomist.Plant nomenclature was used according to theRoyal Botanical Garden and Missouri BotanicalGarden update database (http://www.theplantlist.org/,accessed 10.09.14). Individuals not identified inthe field were assigned to morphospecies, andcollected for later identification using the Lacan-dona reference collection located at the Centro deInvestigaciones en Ecosistemas (UNAM, Morelia,Michoacán, Mexico).

Fragment Spatial MetricsIn each fragment, we measured four spatial

metrics that have been recognized as importantfactors affecting seedling recruitment: fragment size,fragment age, distance to nearest fragment, anddistance to the continuous forest [Benítez-Malvido,T

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0.58

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Am. J. Primatol.

6 / Chaves et al.

1998; Laurance et al., 2006]. To determine fragmentsize and distance to nearest fragment and continuousforest we used LANDSAT satellite images from 2007(Instituto Nacional de Estadística y Geografía,México, http://www.inegi.org.mx/geo/contenidos/im-gpercepcion/imgsatelite/landsat.aspx) from thestudy area complemented with direct field-measuresusing a GPS (Garmin 76 CSX). Information onfragment age was provided by land-owners.

Data AnalysisWe summed up the data of the three blocks

(seedling assemblages) and of the ten transects (adulttrees) from each site and considered the sites asindependent samples for the following analyses. Toassess the inventory completeness within each site,we estimated the expected number of seedling speciesusing four nonparametric estimators (ICE, ACE,Chao2, and bootstrap) with EstimateS 9.1.0 [Colwell,2005]. Because the mean (�SD) sample coverage persite was 81� 15% (Table S2), we assumed that oursampling effort was sufficient [Chao & Jost, 2012].However, to control for differences in sample coverageamong sites (40–100%; Table S2), we based ouranalyses on the density of species (i.e. numbers ofspecies per 45m2).

To test for differences in seedling and adult treeassemblages among forest types (OF,UF, andCF)weused generalized linear models [Lehman et al., 2005]using one analysis for each depedent variable (i.e.stem and species densities). We constructed thefollowing models: dependent variable¼age categoryþdispersal modeþ forest type (nested in age catego-ry and dispersal mode). As suggested for countdependent variables, we fixed a Poisson error and alog link function to the response variables [Lehmanet al., 2005].Whenwe found differences among foresttypes, we used post hoc analyses with contrasts toidentify which forest condition differed among eachother [Lehman et al., 2005].

To assess whether the recruitment of LS speciesin each forest type depended on the availability ofadult trees, we used a modified version of theelectivity index (e) presented by Chesson [1983].This index is based on Manly’s alpha selection index(a), which considers the proportion of each resourceused (or proportion of each seedling species in ourcase) relative to the proportion of adult trees in eachstudy site [Krebs, 1999]. However, in cases in whichthe number of available trees varies, results may notbe accurate, and hence, Manly’s alpha should beconverted to an electivity index as indicated byChesson [1983]: e¼mai -1/(m-2)aiþ1, wherem is thetotal number of tree species. Chesson’s e rangesbetween -1 and 1. Negative values indicate theabundance of seedlings is lower than the expectedabundance of adults (i.e. recruitment limitation);positive values indicate the opposite (i.e. recruitment

enhancement); and values close to zero indicate thatrecruitment is directly proportional to the availabili-ty of adult trees (i.e. neutral recruitment).

To assess the influence that the four spatialmetrics have on seedling species and stem densitieswithin different dispersal modes, we used Spearmanmultiple correlations. These statistical analyseswere performed using JMP software (version 8.0,SAS Institute, Cary, N.C.).

RESULTSOverview

After 16 months, we recorded 6,879 seedlings(2,087 in CF, 1,472 in OF, and 3,320 inUF) belongingto 90 species (plus 43morphospecies), 59 genera, and37 families in 405 1-m2 plots. Of these species, 78.9%were trees, 15.6% shrubs, 4.4% lianas, and 1.1%palms. According to the dispersal mode, most wereSS species (58 species, 64.4%), followed byAD species(20, 22.2%), and LS species (12, 13.3%). Of the top tenspecies in CF, four were LS species, while in OF andUF this number was three (Table II). The three mostabundant seedling species varied according to foresttype. In CF these specieswereAmpelocera hottlei (LSspecies, 33% of individuals), Castilla elastica (SSspecies, 15%), and Brosimum aliscastrum (SS spe-cies, 12%). The threemost abundant seedling speciesin OF were two SS species (Inga punctata, 22%, andC. elastica, 11%) and one LS species (B. alicastrum,18%), while in UF two AD species (Licania hypo-leuca, 21%, and Vochysia guatemalensis, 16%), andone LS species (B. alicastrum, 17%; Table II) weremost abundant.

Differences in Species and Stem DensitiesAmong Forest Types

Density of seedlings and adult trees in eachdispersal mode differed between forest types(x2¼222.8, df¼ 20, P < 0.0001). Considering alldispersal modes, density of adult trees and seedlingswere higher in unoccupied fragments than in theother two forest types (contrast tests, P<0.05 in allcases; Fig. 1). Conversely, density of individuals fromseedling LS species was higher in continuous forestthan in the other forest types, but this coincided withthe pattern observed for the adult trees (Fig. 1).Similarly, we found a greater density of seedlings ofSS and AD species in UF, which concurred with thepattern observed in adult trees (Fig. 1).

The species density of adult trees and seedlingsin each dispersal mode also differed between foresttypes (Fig. 1; x2¼972.3, df¼20, P<0.0001), and,with only some slight differences, density of seedlingspecies presented the same pattern as adult trees(Fig. 1). Density of seedling LS species was higher inCF than in OF and UF, and a similar pattern was

Am. J. Primatol.

Primate Extirpation from Seedling Recruitment / 7

observed for adult trees (contrast test, P< 0.05 in allcases; Fig. 1). We found a higher proportion ofseedling LS species in CF than in OF and UFfragments, but this pattern was also found in adulttrees (Fig. S2). Overall, the proportion of individualsand species in each dispersal mode corresponded tothe pattern observed in the adult trees (Fig. S2),suggesting a strong effect of adult tree community onthe observed recruitment patterns. Prediction 1 wastherefore not supported.

Recruitment of LS Species and Availability ofAdult Trees

The electivity index varied greatly among spe-cies, sites, and forest types (Fig. 2), suggesting thatprimates do not have an important role in therecruitment of LS species. For example, the recruit-ment of Spondias radlkoferi seems to be stronglylimited in all UFs and in two of the three CFs. Therecruitment of Pouteria campechiana was limited inall CFs, in two of the threeOFs and in one of the threeOFs. Similar variations were found in the other twoLS species (Fig. 2). Our second prediction wastherefore supported partially for S. radlkoferi butnot for the other three species.

LS Species and Correlation With SpatialMetrics

Correlation analyses showed that both thespecies and stem densities of LS seedling specieswere significantly related (negatively) to distance tocontinuous forest. However, no other significantcorrelations were detected (P>0.1 in all cases,Table III). Therefore, our third prediction waspartially supported.

DISCUSSIONOverall, our findings do not support the hypothe-

sis that primate extirpation in the Lacandona rain-forest fragments disrupts the recruitment of large-seeded animal-dispersed species at the communitylevel, suggesting that dispersal services provided byprimates may be ecologically redundant. However, atthe individual species level, it is noteworthy that thelargest seeded species, S. radlkoferi, had limitedrecruitment in the unoccupied fragments. Thisobservation suggests that the results obtained inour studymay change in a community that consists ofmore LS species than in Lacandona. However, thishypothesis remains to be tested.

Our data suggest that seedling recruitment inthis area is driven by the adult tree assemblagestructure and hence, by the seed rain of the differentgroups of species. Thus, our data only providedminimal support for our predictions about therelevant role of primates in recruitment patterns.

We found that: (i) stem and species densities ofseedlings in each dispersal mode were not affected byprimate presence but reflected the same patternsobserved in adult trees, particularly in the case of LSspecies (Fig. 1, Fig. S2), (ii) recruitment limitation ofLS species occurred not only in unoccupied frag-ments, but in OFs and CFs, and (iii) stem and speciesdensities of LS species were negatively correlatedwith distance to continuous forest. Our findingscontrast with other studies suggesting that thedisappearance or low density of atelids can affectnegatively the recruitment of large-seeded species inforest fragments [Marsh & Loiselle, 2003; Stevenson& Aldana, 2008] and disturbed continuous forests[Nuñez-Iturri et al., 2008; Peres & van, 2002;Stevenson, 2011]. Similar findings have also beenreported for paleotropical forests differing in primateabundance [Chapman & Onderdonk, 1998; Effiomet al., 2013, 2014].

The discrepancy between our findings and thecited studies can be explained, at least in part, by thefact that most studies on the topic do not control forthe effect of the adult tree assemblage on seedlingrecruitment [e.g. Chapman & Onderdonk, 1998;Nuñez-Iturri et al., 2008; Nuñez-Iturri and Howe,2007; Stevenson & Aldana, 2008; but see Effiomet al., 2013]. This might overestimate the true role ofprimates on plant regeneration. Moreover, severalstudies show that forest regeneration in fragmentedlandscapes is often driven by the assemblage of adulttrees and/or by other forest traits, such as fragmentsize and age, and isolation level [e.g. Bennett &Saunders, 2010; Laurance, 2005; Laurance et al.,2006]. The interaction among these factors results inhabitats with contrasting environmental conditions,such as forest edges, gaps, and closed forests, thatcan favor or limit the recruitment, survival, andreproduction of both small and large-seeded animal-dispersed species [Bennett & Saunders, 2010;Laurance, 2005; Santo-Silva et al., 2013]. Overall,density and richness of pioneer and/or small seededseedling species increase in smaller and openhabitats, while recruitment of large-seeded speciesdecrease [Laurance, 2005; Santo-Silva et al., 2013].This concurs, at least in part, with our main results.In sum, the effects of primate’ extirpation on seedlingassemblages are most likely site dependent.

There are at least three other non-exclusiveexplanations for our results that we cannot reject.First, different ecological scales and/or methodolo-gies could lead to contrasting results on themutualistic relationship between frugivores andthe consumed fruit species [Burns, 2004, 2005]. Forinstance, herewe used 1-m2 sampling plots and adulttree inventories to study the impact of primates onthe seedling recruitment at the community level,while other studies on the topic have studied only asmall number of large-seeded species that recruitunderneath sleeping trees [Nuñez-Iturri & Howe,

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8 / Chaves et al.

2007; Sethi &Howe, 2009]. Even in studies located inthe same study area, the conclusions on the disperserplant mutualisms might be scale dependent [re-viewed by Burns, 2004].

Second, because most vertebrate species are stillpresent in Lacandona [Garmendia et al., 2013] someother seed dispersers (e.g. large frugivorous birds,large rodents, bats, kinkajous, and coatis) mightcompensate for the dispersal services provided byprimates in this region. In this sense, Herrera [1985]mentions that relationships between angiospermsand their animal dispersers are generally bestdescribed as diffuse networks rather than close co-evolutionary relationships. In agreement with thisidea, Donatti et al. [2007] show that local extinctionsof large bodied frugivores rarely influence thesurvival of the seed species, including large seededspecies, they disperse [but see Levi & Peres, 2013].

Finally, it is probable that abiotic seed dispersaland/or asexual reproductive ability of LS species andmany other plant species [Lasso et al., 2009],guarantee some level of recruitment even in theabsence of animal dispersers [Donatti et al. 2007].For instance, in our study area a non-quantifiedpercentage of seeds from some LS species such asSpondias radlkoferi andAmpelocera hottlei are oftendispersed by gravity, water, or both at distances of upto 50m from the parental tree [OMC, pers. obs.].

Although our findings are novel and hopeful fortropical rainforests, our conclusions should be takenwith caution because the work is based on a smallnumber of replicas by forest type and only four LSspecies. Further long-termstudies are needed to have abetter understanding of the impact that primatedisappearance will have on the future of this uniquebut vanishing ecosystem. Studies focused on particularplant populations (particularly those with criticalstructural and/or functional importance) are alsoneeded, as we cannot reject the hypothesis that someparticularLSspeciesmaybeaffectedby theextirpationof primates [e.g.Ampelocerahottlei:González-DiPierroet al., 2011;Manilkara zapota: Gutiérrez-Granados &Dirzo, 2010]. Finally, it is imperative that futurestudies take into account the adult tree populationpresent when evaluating regeneration patterns ofseedlings and saplings. This information will be usefulin determining if the results found here can begeneralized to other tropical forests, or if this is amore local phenomena characteristic of the Lacandonaregion.

ACKNOWLEDGEMENTSThe Instituto para laConservación y elDesarrollo

Sostenible, Costa Rica (INCODESO) provided logisti-cal support. This study would not have been possiblewithout the collaboration of the local people in LomaBonita, Chajul, Reforma Agraria and Zamora Pico deOro. A. Estrada and M. Quesada provided useful

comments and suggestions in early drafts of thispaper. J. Rodríguez collaborated with the identifica-tion of seedlings. J.C. Bicca-Marques and D. Camar-atta provided valuable logistical support during theredaction of this manuscript in Rio Grande do Sul,Brazil. We are grateful for technical support providedby J. M. Lobato Garcia, and G. Sánchez Montoya.

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Supporting InformationAdditional Supporting Information may be found inthe online version of this article.

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