factors that influence the beta-diversity of spider communities in

Submitted 15 October 2015Accepted 28 March 2016Published 21 April 2016

Corresponding authorJose A Corroncajcorroncagmailcom

Academic editorPatricia Gandini

Additional Information andDeclarations can be found onpage 14

DOI 107717peerj1946

Copyright2016 Rodriguez-Artigas et al

Distributed underCreative Commons CC-BY 40

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Factors that influence the beta-diversityof spider communities in northwesternArgentinean GrasslandsSandra M Rodriguez-Artigas Rodrigo Ballester and Jose A CorroncaCONICET IEBI-Facultad de Ciencias Naturales Universidad Nacional de Salta Salta Argentina

ABSTRACTBeta-diversity defined as spatial replacement in species composition is crucial to theunderstanding of how local communities assemble These changes can be driven byenvironmental or geographic factors (such as geographic distance) or a combinationof the two Spiders have been shown to be good indicators of environmental qualityAccordingly spiders are used in this work as model taxa to establish whether thereis a decrease in community similarity that corresponds to geographic distance inthe grasslands of the Campos amp Malezales ecoregion (Corrientes) Furthermorethe influence of climactic factors and local vegetation heterogeneity (environmentalfactors) on assemblage compositionwas evaluated Finally this study evaluatedwhetherthe differential dispersal capacity of spider families is a factor that influences theircommunity structure at a regional scale Spiders were collected with a G-Vac fromvegetation in six grassland sites in the Campos amp Malezales ecoregion that wereseparated by a minimum of 13 km With this data the impact of alpha-diversityand different environmental variables on the beta-diversity of spider communitieswas analysed Likewise the importance of species replacement and nesting on beta-diversity and their contribution to the regional diversity of spider families with differentdispersion capacities was evaluated The regional and site-specific inventories obtainedwere complete The similarity between spider communities declined as the geographicdistance between sites increased Environmental variables also influenced communitycomposition stochastic events and abiotic forces were the principal interveningfactors in assembly structure The differential dispersal capacity of spider groups alsoinfluenced community structure at a regional scale The regional beta-diversity as wellas species replacement was greater in high and intermediate vagility spiders whilenesting was greater in spiders with low dispersion capacity Geographic distance amongother factors (climate and active and passive dispersion capacity) explains assemblystructure and the decrease spider community similarity between geographically distantsites Spiders with the highest dispersal capacity showed greater species replacementThis may be due to the discontinuity (both natural and anthropic) of the grasslandsin this ecoregion which limits the dispersal capacity of these spiders and their closedependence onmicrohabitats The dispersal capacity of the least vagile spiders is limitedby geographic distance and biotic factors such as competition which could explain thenesting observed between their communities

Subjects Biodiversity Ecology EntomologyKeywords Geographic distance Environmental heterogeneity Climate Corrientes-ArgentinaDispersion

How to cite this article Rodriguez-Artigas et al (2016) Factors that influence the beta-diversity of spider communities in northwesternArgentinean Grasslands PeerJ 4e1946 DOI 107717peerj1946

INTRODUCTIONThe relative importance of local and regional environmental factors as controllers oflocal community assembly is a central question in ecology and biogeography (Bell 2001Hubbell 2001 Ricklefs 2004) Beta-diversity (β) defined as the spatial change in speciescomposition (Whittaker 1960) can be the result of the replacement of some species fromone community to another or the result of nesting that reflects a process of species loss (orgain) (Baselga 2010 Baselga 2012) Thus beta-diversity can be considered a key conceptto understand how is the local community assembly (Condit et al 2002 Gering amp Crist2002) the behaviour of ecosystems their operation and for the conservation of biodiversity(Legendre Borcard amp Peres-Neto 2005)

There is a growing interest in identifying which factors determine beta-diversity patternsandhow these influence assembly structure ondifferent spatial scales (Carvalho et al 2011)Several authors have associated beta-diversity with environmental or geographic factorsas well as combinations of the two (Tuomisto Ruokolainen amp Yli-Halla 2003 LegendreBorcard amp Peres-Neto 2005 Soininen McDonald amp Hillebrand 2007 Qian Badgley ampFox 2009 Jimeacutenez-Valverde et al 2010 Carvalho et al 2011) demonstrating that theimportance of these factors depends on the group and taxonomic level studied on spatialscale and the geographic region analysed

Whittaker (1956) andWhittaker (1960) proposed the decline in similarity with increasinggeographic distance That is to say the similarity in species composition between two sitesdiminishes as the geographic distance between them increases (Whittaker 1956 Nekolaamp White 1999) Soininen McDonald amp Hillebrand (2007) proposed three mechanismswhich can act simultaneously and allow explain this phenomenon The first suggeststhat similarity decreases with geographic distance because there is a correspondingincrease in environmental dissimilarity that provokes greater species replacement Thismechanism supposes that species are distributed according to their distinct and specificrequirements and to their tolerance for diverse environmental conditions (Nekola ampWhite 1999) A second mechanism suggests that the decline in similarity could bedue to structural properties of the landscape that limit the range of dispersal Thisproposal envisions a non-homogeneous landscape and the presence of barriers todispersal (Garcillaacuten amp Ezcurra 2003) that affect displacement Finally the decrease insimilarity due to increasing distance between communities could be explained by aspecies own dispersal limit (neutral theory) within a homogeneous space (Hubbell 2001)

Among arthropods spiders have gained wide acceptance as indicators of environmentalquality (Pinkus-Rendoacuten Leoacuten-Corteacutes amp Ibarra-Nuacutentildeez 2006) as such their abundancespecies richness and community structure are useful indicators of the biodiversity ofthe biocoenosis as a whole (Willett 2001) Spider species richness has been correlatedwith latitude and mean annual temperature (Finch Blick amp Schuldt 2008 Whitehouseet al 2009) with habitat complexity and maximum regional temperature (Jimeacutenez-Valverde amp Lobo 2007) as well as with altitudinal gradients (Chatzaki et al 2005 Bowdenamp Buddle 2010) Spiders respond quickly to brusque changes in habitat heterogeneity(Rubio Corronca amp Damborsky 2008) and as a consequence of the narrow spatial

Rodriguez-Artigas et al (2016) PeerJ DOI 107717peerj1946 219

scale in which spiders divide these biotic and abiotic changes they become anappropriate species to evaluate patterns in diversity at a regional scale As follows adecrease in similarity between spider assemblages was recorded as climatic and geographicdistance increased (Carvalho et al 2011) although the response to the latter was weak insome cases (Jimeacutenez-Valverde et al 2010)

Spiders use different strategies to capture prey this variety not only indicates theirdiversity but can also reflect diversity at other trophic levels (Żmudzki amp Laskowski2012) They are distributed across the majority of terrestrial ecosystems as well as somefreshwater ecosystems (Turnbull 1973) Their wide distribution can be explained by thecapacity to disperse passively through the air via silk threads (ballooning) (Braeligndegaard1937Humphreys 1987 Foelix 2011) and occupy a variety of available niches The distancethat a spider can travel by this method depends primarily on body weight and wind thoughunder favourable conditions a spider could travel several hundred kilometres (Okuma ampKisimoto 1981) The wide variety of body sizes and ecological strategies between spiderfamilies renders differences in their capacity to disperse passively (Bishop amp Riechert1990 Suter 1999) Consequently supposing that ballooning is the primary method oflong-distance dispersal (Bishop amp Riechert 1990 Thomas Brain amp Jepson 2003) differentfamilies should have different beta-diversity patterns Some vagile species can reach anyavailable habitat under favourable environmental conditions while other species with poordispersal capabilities are unable to colonize all of the habitats in which they could survive(Araujo amp Pearson 2005 Steinitz et al 2006)

In addition to the dispersal capacity other factors can explain the diversity of spidersincluding their correspondence with the habitat heterogeneity (Uetz 1991Whitmore et al2002 Jimeacutenez-Valverde amp Lobo 2007) understood the latter as the complexity of verticaland horizontal vegetation (Tews et al 2004) Thus heterogeneous habitats provide moreavailable niches and many alternative ways of exploit environmental resources (Bazzaz1975) Habitat heterogeneity influences microclimate and determines the communityof herbivorous species which are spidersrsquo primary food source and consequently itinfluences species composition and abundance in different habitats (Pearce et al 2004)Moreover climate factors such as temperature humidity and precipitation (Bonte Baertamp Maelfait 2002 Jimeacutenez-Valverde amp Lobo 2007 Paredes Mungiacutea 2012) select the speciesthat can live in each locality (Jimeacutenez-Valverde et al 2010)

Five ecoregions converge in Corrientes province including the Campos amp Malezalesecoregion (Burkart et al 1999) This ecoregion is considered a prolongation of theParanaense jungle and extends outward from the southeastern edge of Misiones provinceencompassing an area of 30000 km2 The landscape matrix principally grassland bestowsthe region with great potential for agriculture and cattle farming the latter being thepredominant anthropic activity in the region (Matteucci 2012) Over the last ten yearsmultiple authors (Avalos et al 2007 Rubio Corronca amp Damborsky 2008 Avalos et al2009 Rubio amp Moreno 2010) have analysed spider fauna in the province however onlythe recent study by Rodriguez Artigas (2014) has attempted to identify which factorsinfluence spider communities at different spatial scales in the four ecoregions in CorrientesNotwithstanding that study did not consider geographic distance as a possible determinant


Figure 1 Studied areaMap of the area of study highlighting sampling sites

in diversity patterns For this reason the present study seeks to examine the influence ofgeographical distance and the effect of environmental variables (climate and habitatheterogeneity) on spider diversity patterns of Campos amp Malezales ecoregion Likewisethis study evaluates whether the differences in the dispersal capacity of spider speciesinfluences their community structure at a regional scale We expect that spider assemblageswould differ between sites and more so at more distant sites demonstrating that themost vagile spider families are more dependent on environmental characteristics and thatgeographic distance would not be among the primary forces driving assembly structureMoreover it is expected that spiders with high vagility can reach to more available nichesshowing a low beta diversity

MATERIALS AND METHODSArea of study Six sites that were geo-referenced of grasslands in eastern Corrientes province(Argentina) within the Campos amp Malezales ecoregion were considered in this study Siteswere arranged fromnorth to south between 2733primendash2930primeS and 5614primendash5849primeW separatedby a distance no smaller than 13 km and reaching 250 km between the most distant pair(Fig 1) This ecoregion is distinguished by its vegetation the matrix consisting of vastgrasslands of plain periodically interrupted by relict patches of Paranaense jungle-likeforest The region has a humid subtropical climate with isohyets at 1800 mm to the


northeast and 1300 mm to the southeast and uniform rain throughout the year The meantemperature oscillates between 20 and 22 C There are periodic floods and fires the latterused as a management tool that to regulate the dynamic vegetation of the ecoregion Thegrasslands are low and dominated byAndropogon Aristida Briza Erianthus PiptochaetiumPoa Stipa Paspalum Axonpus and Panicum species The small patches of open forest thatarise from the savannah are characterized by SyagrusAcaciaAllagoptera andDiplothemiumspecies (Matteucci 2012)

Sampling Samples were collected from vegetation with a G-Vac (garden vacuum) bythe IEBI team (Institute for the Study of Invertebrate Biodiversity- FCN-UNSa) betweenthe spring of 2006 and autumn of 2007 In each collecting site we selected two areas of2 ha each located one on the left and the other on the right side of the route separatingfrom the route border by no less than 150 m In each area 10 randomly samples weretaken per season (Spring and Autumn) Each suction sample was spaced from anotherby not less than 50 m Thus a total of 40 suction samples was taken per collecting site Asingle suction sample consisted of vacuuming an area of one square meter for one minuteThe material collected was placed in polyethylene bags with 70 ethyl alcohol labelledappropriately and transported to the laboratory for analysis Spiders were recorded inspreadsheets and all were classified by family following the keys available (Dippenaar-Schoeman amp Jocqueacute 1997 Ramiacuterez 1999 Ubick et al 2005) Morphospecies were assignedaccording to the methodology proposed by Oliver amp Beattie (1996) to those spiders thatcould not be identified to species taxonomic level This information was incorporated intothe database at IEBI (IEBIData) which includes digital pictures of somatic and externalgenital distinctive characters of each speciesmorphospecies that easily permit to identifyindividuals and assign them to a correct species morphospecies Collected specimens weredeposited in the IEBI-MCN Collection (Instituto para el Estudio de la Biodiversidad deInvertebrados-Museo de Ciencias Naturales Universidad Nacional de Salta)

Environmental variables To characterize each of the selected samples sites informationon eight bioclimatic variables were obtained from the WorldClim-Bioclim (wwwworldclimorg) database including temperature and precipitation two variables associatedwith productivity (Normalized vegetation Index NDVI) for the months in whichsamples were taken which were obtained from Modis satellite images from NASA(httpmodisgsfcnasagov) and four variables measured in situ of local vegetationheterogeneity The latter variables were quantified as a percentage vegetation per strataat 50 cm intervals from ground level to 2 m as described by Huang et al (2011) Thismeasurement was only taken in the autumn and therefore variables associated withenvironmental heterogeneity were only incorporated into analysis that included autumn

Selection of spider families with different dispersal capacities To test whether thedifferential dispersal capacities of spider families influence the structure of spidercommunities on a regional scale six spider families were selected Araneidae TheridiidaeThomisidae Salticidae Anyphaenidae and Miturgidae The first two families build webs tocapture prey while the other four ones hunt on the ground and in the vegetation (Cardosoet al 2011) Different spider families have distinct dispersal capacities both active andpassive Araneidae and Theridiidae dispersal passively through the air (ballooning) which


allows them to travel several hundred kilometres under favourable conditions (Okumaamp Kisimoto 1981) Thomisidae can also dispersal via ballooning (Foelix 2011) howeverlike Salticidae (both foliage runners) they tend to dispersal on the ground (Liljesthroumlm etal 2002) These families can rapidly run short distances and use this dispersal methodwidely (Dondale et al 1970) Finally Anyphaenidae and Miturgidae exclusively dispersalon the ground (Gertsch 1979) and this dispersal is limited Following this criteria andthat outlined by Jimeacutenez-Valverde et al (2010) the families are grouped as high vagility(Araneidae and Theridiidae) intermediate vagility (Thomisidae and Salticidae) and lowvagility (Anyphaenidae and Miturgidae)

Data analysisInventory and alpha diversity Inventory completeness was evaluated using the non-parametric estimators of species richness Chao1 and ACE which represent the lower andupper limits respectively of the species richness in communities with highly heterogeneoussamples (Chao amp Shen 2012) These estimators were calculated with the program SPADE(Chao amp Shen 2009) and were used to calculate inventory completeness at differentscales The program PAST v217 (Hammer Harper amp Ryan 2001) was used to run ananalysis of similarities (ANOSIM) to test for statistically significant differences betweenspider assemblages at the sampling sites To evaluate and compare the diversity betweensites the true observed diversity and the estimated diversity for each community werecalculated using the Reacutenyi one-parametric diversity index family (Toacutethmeacutereacutesz 1995) andthe estimators Chao Chao amp Shen and MVUE to estimate zero first and second-orderdiversity respectively Both calculations weremade using the PAST v217 (Hammer Harperamp Ryan 2001) and SPADE (Chao amp Shen 2009) programs

Evaluation of geographic distance and environmental variables with respect to spidercommunities A simple Mantel test verified the relative importance of geographic distanceon the patterns of beta-diversity obtained The test considered a faunistic matrix (generatedusing Jaccard distance data as a measure of the similarity between spider communitiesbetween sites) and a geographic distance matrix (generated using site coordinates inWGS84 format and the geographic distance as a measure of distance between site pairs)The Mantel tests were performed with the PAST v217 (Hammer Harper amp Ryan 2001)program using Pearsonrsquos correlation coefficient and 10000 permutations to evaluatethe statistical significance between matrices The influence of geographical distance andenvironmental variables (climate and vegetation) on the distribution pattern of spiderswas assessed by a variation partitioning procedure (Borcard Legendre amp Drapeau 1992)using the package lsquolsquoVeganrsquorsquo in the software R Thus the total variation of the abundancematrix was partitioned in its purely spatial purely climate and purely vegetation complexityeffects in the fraction explained by the correlation between them and also by the residualfraction Previously principal coordinates of neighbour matrices (PCNM) was performedto obtain spatial variables These variables as environmental ones were subjected to a runforward selection using an analysis of canonical redundancy (RDA) (Legendre amp Legendre1998) to select the variables that were included in the variation partitioning procedure(Blanchet Legendre amp Borcard 2008) βRC was calculated based on the Raup-Crick


similarity following the formula outlined by Chase et al (2011) This measurementpermitted the inference of events associated the dissimilarity between site pairs inaccordance with the following interpretation βRC asymp 0 Similarityobservedasymp Similarityexpected(stochastic events structure communities high dispersion between sites) βRC asymp 1Similarityobserved lt Similarityexpected (differences in deterministic environmental filtersbetween sites favours dissimilarity in species composition biotic forces drive differentiationin adjacent communities) and βRC asympminus1 Similarityobserved gt Similarityexpected (shareddeterministic environmental filters generate high similarity between sites as a result ofabiotic factors)

The same methodology above described was applied to the question of correlationbetween the faunistic geographic distance and environmental matrices for each ofthe family groups selected taking into account dispersal capacity and the importanceof ballooning (wind dispersal) as a dispersal technique in the structuring of spidercommunities at a regional scale

Dispersal and beta-diversity The contribution of beta-diversity in the regional diversity(gamma) of the groups with different dispersal capacities was calculated from amultiplicative partition of diversity using the program PARTITION 30 (Veech amp Crist2009) where γ = α1 (within the samples) times β1 (between samples) times β2 (betweenregional sites) The latter observed β value was collated with the value expected withrandom distribution (Crist et al 2003) and compared between groups Finally the totalbeta-diversity of each group of families with distinct dispersal capacities was partitionedinto its components nesting and species replacement as described in the Soslashrensen indexThe R lsquolsquobetapartrsquorsquo pack provided by Baselga et al (2013) was used for this analysis

RESULTSInventory and alpha diversityA total of 3873 adult and immature spiders belonging to 251 speciesmorphospecies and27 families were collected Araneidae Theridiidae and Oxyopidae were the dominantfamilies representing 2943 1942 and 1910 respectively of total abundance whileAraneidae and Salticidae had greater species richness (S= 52 and S= 40 respectively) Theperformance of the non-parametric estimators of species richness found that the inventoryreached 74 of the value estimated by Chao1 (Table 1)

Spider communities differed between pair of sites (Anosim Rgt 063plt 001) Allsites had a specific richness equal to or greater than 80 species except for site 1 (Table 1)The inventory of each site was unable to capture the total spider diversity present in eachsite though completeness values were good and were near to or greater than 60 of theChao1 estimate (Table 1) The true observed and estimated diversity parameters indicatedifferent community behaviour in rare and dominant species consequently under thesecircumstances sites were not able to compare in this respect (Table 1)

Beta-diversity similarity decreases with geographic distanceThe Mantel test (R= 053plt 005) demonstrated that geographic distance had a directeffect of the similarity of spider assemblages confirming that these communities become less


Table 1 Diversity parameters The abundance and species richness of spider species non-parametric estimator values (Chao1 y ACE) of the in-ventory completeness and the true observed and estimated diversity

Site 1 Site 2 Site 3 Site 4 Site 5 Site 6 TOTAL

Richness 40 80 110 82 84 103 251Abundance 102 803 703 480 843 942 3873Chao1 6756 12188 17503 12283 11415 16618 33911ACE 726 1387 1820 1293 1217 2249 3426Inventory completeness (Chao1) 5920 6564 6284 6676 7358 6198 7402

0D(Sobs) 40 80 110 82 84 103 ndash1D(Shannonentropy) 2713 1320 2822 2950 3159 2059 ndashObserved diversity2D(GiniminusSimpsonIndex) 1912 461 1112 1278 1995 862 ndash0D(Chao) 676 1219 1750 1228 1142 1662 ndash1D(ChaoampShen) 3770 1531 3449 3512 3473 2417 ndashEstimated diversity2D(MVUE) 2331 463 1128 1310 2041 869 ndash

Table 2 RaupndashCrick values RaupndashCrick values are indicated below the diagonal and modified Chase etal (2011) values above the diagonal (light grey=βRC asymp 0 black=βRC asymp 1 dark grey=βRC asympminus1)

Site 1 Site 2 Site 3 Site 4 Site 5 Site 6

Site 1 ndash 0773 minus0664 minus0915 minus0247 minus0424Site 2 0887 ndash 0531 0331 minus0971 minus0721Site 3 0168 0766 ndash 0846 minus0939 minus0956Site 4 0043 0666 0077 ndash 0005 minus0353Site 5 0377 0015 0031 0503 ndash minus0674Site 6 0288 0140 0022 0324 0163 ndash

NotesβRC asymp 0 Similarityobserved asymp Similarityexpected (stochastic events structure communities high dispersion betweensite) βRC asymp 1 Similarityobserved lt Similarityexpected (differences in deterministic environmental filters between sitesfavors dissimilarity in species composition biotic forces drive differentiation in adjacent communities) βRC asymp minus1Similarityobserved gt Similarityexpected (shared deterministic environmental filters generate high similarity between sites as aresult of abiotic factors)

similar as the distance between them increases This variable together with environmentalones explained 39 of the changes in the composition of spider assemblages (Fig 2)The variation mainly corresponded to the pure effects of vegetation complexity (17)the latter with climate explained 28 of the composition changes The analysis of Raup-Crick similarity based on standardized values also supported these findings showingthat deterministic abiotic forces followed by stochastic events are important factors thatcontribute to the structure of the spider communities considered in this study (Table 2)

Beta-diversity the relationship between dispersion and beta-diversityWith respect to the dispersal capacity of spider families the geographic distanceexplained 16 of the variation in the composition of the spider assemblages with highdispersal capacity (Fig 3A) however it was not significant according to the Mantel test(R= 044pgt 005) Meanwhile 21 of the changes in the composition of communitiescan be attributed to the purely climate and purely vegetation complexity effects This


Figure 2 Variation partitioningVariation partitioning showing the relative influence of the geograph-ical distance climate and vegetation complexity variables on the spider assemblages in grassland of Cam-pos amp Malezales ecoregion (Corrientes-Argentina)

percentage rises to 25 if it also considers its spatial structure Thus even though stochasticevent are important the deterministic abiotic forces were the key factor driving spidercommunity structure (Table 3)

In the intermediate vagile spider families the geographical distance had little influencein the dissimilarity of spider assemblages (Mantel test R= 031pgt 005) (Fig 3B) beingenvironmental variables the most important in structuring community However themodel only explained 10 of the changes in spider assemblages indicating that otherfactors mainly biotic according to βRC values could influence the distribution pattern ofthe species (Table 3)

Geographic distance did an important role in structuring the assemblages of familieswith a low dispersal capacity (Mantel test R= 049plt 005) explaining 18 of thevariation of the assemblages (Fig 3C) Environmental variables also influenced on thecommunity dissimilarity although the biotic forces and stochastic factors would be themost important for structuring the communities of the least vagile spider (Table 3)

Regional beta-diversity (β2) was greater in families with a high dispersal capacity andlesser in less vagile families exceeding the values expected by chance by 34 29 and14 respectively (Fig 4) β2 (between sites) diversity significantly exceeded expecteddiversity values indicating that these species were not randomly distributed Likewisethe differences between the expected and observed β1 (between samples) diversity valueswere statistically significant for the families with the greatest and lowest dispersal capacityrevealing their capacity to occupy different available niches


Figure 3 Variation partitioning by families with different dispersal capacityVariation partitioningshowing the relative influence of the geographical distance climate and vegetation complexity variables inspider families with high (A) intermediate (B) and low (C) dispersal capacity

Dissimilarity (βSOR) and species replacement between sites (βSIM ) were greater forspiders with high and intermediate dispersal capacity (Table 4) representing 91 and87 respectively of the total beta-diversity The least vagile families had the least speciesreplacement but the highest nesting value (25 of the observed dissimilarity) (Table 4)

DISCUSSIONSpider species richness in the grassland of the Campos amp Malezales ecoregion is high 251speciesmorphospecies from27Araneomorphae families were recorded which correspondsto 90 of the total number of families recorded in Corrientes province (Rodriguez Artigas2014) Our results are comparable to those obtained by other authors in the same provincewho have used intensive sampling methods Rubio Corronca amp Damborsky (2008) reported28 spider families in forests and grasslands in the Mburucuyaacute National Park while Avaloset al (2009) found 33 families in samples obtained from the Iberaacute Provincial Reserve Inthis work four of the families corresponded to orbicular spiders three of which were alsodescribed in the forests and grasslands of the same ecoregion by Rubio amp Moreno (2010)

Although it is difficult to sample the totality of a spider assemblage due to the largenumber of rare species collected (Haddad et al 2010) a large proportion (74) of thespecies present in the Campos amp Malezales grasslands were captured in this study thispercentage was near to or greater than 60 for each site included in this study These resultsindicate good (Cardoso 2009) and complete inventories since the percentage exceeds 50of the estimated total number of species (Chao et al 2009)


Table 3 RaupndashCrick values by families with different dispersal capacity RaupndashCrick values are indi-cated below the diagonal and modified Chase et al (2011) values above the diagonal (light grey= βRC asymp0 black=βRC asymp 1 dark grey=βRC asympminus1) in families with high intermediate and low vagility


HighSite 1 ndash 0539 minus0326 minus0923 minus0120 minus0526Site 2 0770 ndash 0512 minus0744 minus0609 0165Site 3 0337 0756 ndash minus0903 minus0629 0522Site 4 0039 0128 0049 ndash 0359 minus0623Site 5 0440 0196 0186 0680 ndash minus0085Site 6 0237 0583 0761 0189 0458 ndash

MediumSite 1 ndash minus0465 minus0519 minus0537 minus0879 minus0739Site 2 0268 ndash 0163 0856 minus0835 minus0379Site 3 0241 0582 ndash minus0225 0581 minus0786Site 4 0232 0929 0388 ndash 0685 minus0848Site 5 0061 0083 0210 0843 ndash 0580Site 6 0131 0311 0107 0076 0210 ndash

LowSite 1 ndash 0895 0560 0753 0643 0542Site 2 0948 ndash 0065 0954 minus0276 0008Site 3 0780 0533 ndash 0095 0575 minus0877Site 4 0877 0977 0548 ndash minus0577 minus0467Site 5 0822 0362 0788 0212 ndash 0012Site 6 0771 0504 0062 0267 0506 ndash


Table 4 Partition of the total beta diversity into its components Partition of the total beta-diversityinto its components species replacement (βSIM) and nesting (βSNE) for families with varying vagility (dif-ferent letters indicate statistically significant differences between groups plt 005)

VAGILITY βSIM βSNE βSOR

High 0676a 0069a 0745a

Medium 0665a 0100b 0765a

Low 0531b 0177c 0709b

Whittaker (1956) and Whittaker (1960) proposed that geographic distance influencesthe structure of the spider assemblages studied showing a decrease in the similarity ofspider communities as geographic separation increases Similar results were reported byCarvalho et al (2011) in the Portuguese region of the Iberian Peninsula The effect ofgeographical distance could be explained by the first mechanism proposed by Soininen


Figure 4 Partition of gamma diversity of spider diversityMultiplicative partition of the diversity offamilies with high intermediate and low dispersal capacity ( indicates statistically significant differencesbetween observed and expected values)

McDonald amp Hillebrand (2007) because environmental variables also explained the speciesturnover being the habitat heterogeneity (complexity of vegetation) the most relevantThus stochastic and deterministic events like dispersal and abiotic factors respectivelywould be the principle intervening forces on community structure as was verified by thevariation partitioning and βRC values

The results obtained here counter previous findings from a spider study in MadridProvince (Spain) in which Jimeacutenez-Valverde et al (2010) observed that geographic distancewas not an important factor explaining the differences in community compositionHowever other empiric studies revealed that the relationship between similarity andgeographic distance is strongly dependent on the extent of the area of study (Martiny etal 2011 Soininen et al 2011 Steinbauer et al 2012) This could explain the discrepancybetween the results obtained here and in the Spanish study since the distance between themost distant sites in our study was double that of the Jimeacutenez-Valverde et al (2010) study

Although the environmental variables considered have an effect on the similarity ofspider assemblagesThus as suggested by Jimeacutenez-Valverde et al (2010) climate conditionsselect which spider species can live in a given locality but not how many and thathabitat complexity is the principal factor determining the number of species that a localitycan support

Furthermore the differential dispersal capacities of the spiders can influence communitystructure at a regional scale Araneidae and Theridiidae contributed the most to regionalbeta-diversity and together with Salticidae and Thomisidae were the most dissimilar andwith a higher species replacement between communities These results are not consistent


with the findings of Jimeacutenez-Valverde et al (2010) who considered a different set families intheir analysis (Araneidae= high vagility Thomisidae and Salticidae= intermediate vagilityand Gnaphosidae= low vagility) The dispersal capacity a species can be affected by habitatfragmentation (Garcillaacuten amp Ezcurra 2003) increasing beta-diversity between communitiesThis could explain our results since thematrix of the grasslands in the Campos ampMalezalesecoregion contains remnant patches of Paranaense jungle (Matteucci 2012) interspersedin a landscape where humans undertake a variety of activities (ranching agriculture androad-building among others) This could interrupt aerial dispersal increasing beta-diversityof the most vagile spider communities

The geographic distance was not a relevant factor structuring the assemblagesintermediate vagility spiders In this group the dissimilarity between communitiesmight be determined by other abiotic factors not included in this analysis For theirpart the vegetation complexity and climatic distance explained the composition of thehigh-vagility spider assemblages suggesting as mentioned by Jimeacutenez-Valverde amp Lobo(2007) that spider diversity is principally determined by vegetation complexity and theclimatic conditions of a given site As in the general model geographic distance generatesan environmental dissimilarity (Soininen McDonald amp Hillebrand 2007) that explainsthe changes in species composition of the families of more vagile spiders The spidersof these families dispersal aggregately on a local scale showing a close dependence onmicro-habitats which are necessary to fasten webs (Simoacute et al 2011) and serve as sites ofrefuge (Jimeacutenez-Valverde amp Lobo 2007) These spiders select micro-habitats that favourprey availability (Sunderland amp Samu 2000) or minimize competitive exclusion andcannibalism (Viera 2011)

Stochastic factors like dispersal are important in structuring the assemblages of lowvagility spider families However this last factor (dispersal) would be limited by theseparation between sites as was demonstrated in these results Thus the dispersal of thisgroup of spiders is affected by the distance between sites responding to second and thirdmechanism proposed by Soininen McDonald amp Hillebrand (2007) For their part bioticfactors such as competition could lead to species exclusion (Wise 2006) and would berelevant to this group of spiders this would explain the greater degree of nesting betweenthese communities with respect to families with high and intermediate dispersal capacity

CONCLUSIONSOur results reflect that the grasslands in the Campos ampMalezales ecoregion support a greatdiversity of spider species that vary between sites This indicates that despite a homogeneousappearance grasslands are a heterogeneous habitat from a spider perspective (Ferro ampRomanowski 2012) Geographic distance does influence the decrease in spider communitysimilarity but it is not the only force explain beta-diversity between distant sites There areother factors that contribute to the structuring of the local and regional spider assemblagessuch as climatic factors vegetation complexity and dispersal acting differently accordingto the studied group Dispersal has a differential effect on distinct spider assemblages thiseffect is heavily influenced by the active and passive dispersal capacity of each assemblages


constituents Future studies that evaluate additional variables may be necessary to identifyadditional forces that determine the structure of the spider communities in these grasslandsparticularly of intermediate vagility spiders which are important for maintaining diversityin their communities

ADDITIONAL INFORMATION AND DECLARATIONS

FundingThe material collection was financially supported by CONICET (Consejo Nacional deInvestigaciones Cientiacuteficas y Teacutecnicas PIP-CONICET 2005-2007) JAC received financialsupport from the CIUNSa (Consejo de Investigaciones de la Universidad Nacional deSalta) The funders had no role in study design data collection and analysis decision topublish or preparation of the manuscript

Grant DisclosuresThe following grant information was disclosed by the authorsCONICET (Consejo Nacional de Investigaciones Cientiacuteficas y Teacutecnicas PIP-CONICET2005ndash2007)CIUNSa (Consejo de Investigaciones de la Universidad Nacional de Salta)

Competing InterestsThe authors declare there are no competing interests

Author Contributionsbull SandraM Rodriguez-Artigas performed the experiments analyzed the data contributedreagentsmaterialsanalysis tools wrote the paper prepared figures andor tablesbull Rodrigo Ballester performed the experiments analyzed the data prepared figures andortablesbull Jose A Corronca conceived and designed the experiments performed the experimentsanalyzed the data contributed reagentsmaterialsanalysis tools wrote the paperreviewed drafts of the paper

Data AvailabilityThe following information was supplied regarding data availability

The raw data has been supplied as a Supplemental Dataset

Supplemental InformationSupplemental information for this article can be found online at httpdxdoiorg107717peerj1946supplemental-information

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Condit R Pitman N Leigh EG Chave J Terborgh J Foster RB Nunez VP Aguilar SValencia R Villa G Muller-Landau HC Losos E Hubbell SP 2002 Beta-diversityin tropical forest trees Science 295666ndash669 DOI 101126science1066854

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Foelix RF 2011 Biology of spiders 3rd edition Oxford Oxford University PressGarcillaacuten PP Ezcurra E 2003 Biogeographic regions and β-diversity of woody dryland

legumes in the Baja California peninsula Jounal of Vegetation Science 14859ndash868DOI 101111j1654-11032003tb02219x

Gering JC Crist TO 2002 The alpha-beta-regional relationship providing new insightsinto local-regional patterns of species richness and scale dependence of diversitycomponents Ecology Letters 5433ndash444 DOI 101046j1461-0248200200335x

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Spider as potential indicators of elephant-induced habitat change in endemic sandforest Maputaland South Africa African Journal of Ecology 48446ndash460


Hammer O Harper DAT Ryan PD 2001 PAST palaeontological statistics Version 217Available at http folkuionoohammerpast (accessed September 2015)

Huang PS Tso IM Lin HC Lin LK Lin CP 2011 Effects of thinning on spider diversityof an east asian subtropical plantation forest Zoological Studies 50705ndash717

Hubbell SP 2001 The unified neutral theory of biodiversity and biogeography (MPB-32)Princeton and Oxford Princeton University Press

HumphreysWF 1987 The thermal biology of the wolf spider Lycosa tarentula(Araneae Lycosidae) in Northern Greece Bulletin of the British Arachnological Socity7117ndash122

Jimeacutenez-Valverde A Baselga A Melic A Txasko N 2010 Climate and regional beta-diversity gradients in spiders dispersal capacity has nothing to say Insect Conserva-tion and Diversity 351ndash60 DOI 101111j1752-4598200900067x

Jimeacutenez-Valverde A Lobo JM 2007 Determinants of local spider (Araneidae andThomisidae) species richness on a regional scale climate and altitude vs habitatstructure Ecological Entomology 32113ndash122 DOI 101111j1365-2311200600848x

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Legendre P Legendre L 1998Numerical ecology Amsterdam ElsevierLiljesthroumlmGMinervino E Castro D Gonzalez A 2002 La comunidad de arantildeas del

Cultivo de Soja en la provincia de Buenos Aires Argentina Neotropical Entomology31197ndash210 DOI 101590S1519-566X2002000200005

Martiny JB Eisen JA Penn K Allison SD Horner-Devine MC 2011 Drivers ofbacterial β-diversity depend on spatial scale Proceedings of the National Academy ofSciences of the United States of America 1087850ndash7854DOI 101073pnas1016308108

Matteucci SD 2012 Ecorregioacuten Campos y Malezales In Morello J Matteucci SDRodriacuteguez AF Silva M eds Ecorregiones y complejos ecosisteacutemicos argentinos BuenosAires Orientacioacuten Graacutefica Editora 247ndash263

Nekola JCWhite PS 1999 The distance decay of similarity in biogeography andecology Journal of Biogeography 26867ndash878 DOI 101046j1365-2699199900305x

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Oliver I Beattie AJ 1996 Invertebrate morphospecies as surrogates for species a casestudy Conservation Biology 199ndash109 DOI 101046j1523-1739199610010099x

Paredes MungiacuteaW 2012 Spider from pantanos de Villa Reserved Zone (Lima Peruacute)diversity and spatio-temporal variation of spider communities Saarbruumlcken LambertEditorial

Pearce JL Venier LA Eccles G Pedlar J McKenney D 2004 Influence of habitat andmicrohabitat on epigeal spider (Araneae) assemblages in four stand types Biodiver-sity and Conservation 131305ndash1334 DOI 101023BBIOC00000194032694855


Pinkus-RendoacutenMA Leoacuten-Corteacutes JL Ibarra-Nuacutentildeez G 2006 Spider diversity in atropical habitat gradient in Chiapas Mexico Diversity and Distributions 1261ndash69DOI 101111j1366-9516200600217x

Qian H Badgley C Fox DL 2009 The latitudinal gradient of beta diversity in relationto climate and topography for mammals in North America Global Ecology andBiogeography 18111ndash122 DOI 101111j1466-8238200800415x

Ramiacuterez MJ 1999 Orden Araneae In Crespo FA Iglesias MS Valverde AC eds El ABCen la determinacioacuten de artroacutepodos Clave para especiacutemenes presentes en la ArgentinaBuenos Aires Editorial CCC Educando

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Rodriguez Artigas SM 2014 Paisaje y comunidad de arantildeas (Araneae) Anaacutelisis adiferentes escalas espaciales en ecorregiones asociadas al Sistema Esteros del IberaacuteCorrientes-Argentina Tesis Doctoral Universidad Nacional de Salta

Rubio GD Corronca JA DamborskyMP 2008 Do spider diversity and assemblageschange in different contiguous habitats A case study in the protected habitats ofthe Humid Chaco ecoregion north-east Argentina Environmental Entomology37419ndash430 DOI 101093ee372419

Rubio G Moreno CE 2010 Orb-weaving spider diversity in the Iberaacute MarshlandsArgentina Neotropical Entomology 39(4)496ndash505DOI 101590S1519-566X2010000400006

SimoacuteM Laboarda A Jorge C CastroM 2011 Araneomorphae el grupo maacutes diversode las arantildeas In Viera C ed Araacutecnidos de Uruguay Diversidad comportamiento yecologiacutea Montevideo Ediciones de la Banda Oriental

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Soininen J McDonald R Hillebrand H 2007 The distance of similarity in ecologicalcommunities Ecography 303ndash12 DOI 101111j0906-7590200704817x

Steinbauer MJ Dolos K Reineking B Beierkuhnlein C 2012 Current measuresfor distance decay in similarity of species composition are influenced bystudy extent and grain size Global Ecology and Biogeography 211203ndash1212DOI 101111j1466-8238201200772x

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Suter RB 1999 An aerial lottery the physics of ballooning in a chaotic atmosphereJournal of Arachnology 27281ndash293


Tews J Brose U GrimmV Tielboumlrger KWichmannM Schwager M JeltschF 2004 Animal species diversity driven by habitat heterogeneitydiversitythe importance of keystone structures Journal of Biogeography 3179ndash92DOI 101046j0305-0270200300994x

Thomas CFG Brain P Jepson PC 2003 Aerial activity of linyphiid spiders modellingdispersal distances from meteorology and behaviour Journal of Applied Ecology40912ndash927 DOI 101046j1365-2664200300844x

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Turnbull AL 1973 Ecology of the true spiders (Araneomorpha) Annual Reviews ofEntomology 18305ndash348 DOI 101146annureven18010173001513

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Ubick D Paquin P Cushing PE Roth V 2005 Spider of North America an identificationmanual Keene New Hampshire American Arachnological Society

Uetz GW 1991 Habitat structure and spider foraging In Bell SS McCoy ED Mushin-sky HR eds Habitat Structure the physical arrangement of objects in space LondonChapman and Hall

Veech JA Crist TO 2009 PARTITION software for hierarchical partitioning of speciesdiversity Version 30 Available at httpwwwusersmuogioedu cristtopartitionhtm(accessed September 2015)

Viera C 2011 Comportamiento constructor y depredador de arantildeas de tela In VieraC ed Araacutecnidos de Uruguay Diversidad comportamiento y ecologiacutea MontevideoEdiciones de la Banda Oriental

Whitehouse MEA Hardwick S Scholz BCG Annells AJ Ward A Grundy PR HardenS 2009 Evidence of a latitudinal gradient in spider diversity in Australian cottonAustral Ecology 3410ndash23 DOI 101111j1442-9993200801874x

Whitmore C Slotow R Crouch T Dippenaar-Schoeman A 2002 Diversity of spider(Araneae) in a Savanna Reserve Northern Province South Africa Journal of Arach-nology 30344ndash356 DOI 1016360161-8202(2002)030[0344DOSAIA]20CO2

Whittaker RH 1956 Vegetation of the great smoky mountains Ecological Monographs261ndash80 DOI 1023071943577

Whittaker RH 1960 Vegetation of the Siskiyou Mountains Oregon and CaliforniaEcological Monographs 30279ndash338 DOI 1023071943563

Willett TR 2001 Spiders y other arthropods as indicators in old-growth versus loggedredwood stands Restoration Ecology 9410ndash420DOI 101046j1526-100X200194010x

Wise DH 2006 Cannibalism food limitation intraspecific competition and theregulation of spider populations Annual Review of Entomology 51441ndash465DOI 101146annurevento51110104150947

Żmudzki S Laskowski R 2012 Biodiversity and structure of spider communities along ametal pollution gradient Ecotoxicology 211523ndash1532DOI 101007s10646-012-0906-3


INTRODUCTIONThe relative importance of local and regional environmental factors as controllers oflocal community assembly is a central question in ecology and biogeography (Bell 2001Hubbell 2001 Ricklefs 2004) Beta-diversity (β) defined as the spatial change in speciescomposition (Whittaker 1960) can be the result of the replacement of some species fromone community to another or the result of nesting that reflects a process of species loss (orgain) (Baselga 2010 Baselga 2012) Thus beta-diversity can be considered a key conceptto understand how is the local community assembly (Condit et al 2002 Gering amp Crist2002) the behaviour of ecosystems their operation and for the conservation of biodiversity(Legendre Borcard amp Peres-Neto 2005)

There is a growing interest in identifying which factors determine beta-diversity patternsandhow these influence assembly structure ondifferent spatial scales (Carvalho et al 2011)Several authors have associated beta-diversity with environmental or geographic factorsas well as combinations of the two (Tuomisto Ruokolainen amp Yli-Halla 2003 LegendreBorcard amp Peres-Neto 2005 Soininen McDonald amp Hillebrand 2007 Qian Badgley ampFox 2009 Jimeacutenez-Valverde et al 2010 Carvalho et al 2011) demonstrating that theimportance of these factors depends on the group and taxonomic level studied on spatialscale and the geographic region analysed

Whittaker (1956) andWhittaker (1960) proposed the decline in similarity with increasinggeographic distance That is to say the similarity in species composition between two sitesdiminishes as the geographic distance between them increases (Whittaker 1956 Nekolaamp White 1999) Soininen McDonald amp Hillebrand (2007) proposed three mechanismswhich can act simultaneously and allow explain this phenomenon The first suggeststhat similarity decreases with geographic distance because there is a correspondingincrease in environmental dissimilarity that provokes greater species replacement Thismechanism supposes that species are distributed according to their distinct and specificrequirements and to their tolerance for diverse environmental conditions (Nekola ampWhite 1999) A second mechanism suggests that the decline in similarity could bedue to structural properties of the landscape that limit the range of dispersal Thisproposal envisions a non-homogeneous landscape and the presence of barriers todispersal (Garcillaacuten amp Ezcurra 2003) that affect displacement Finally the decrease insimilarity due to increasing distance between communities could be explained by aspecies own dispersal limit (neutral theory) within a homogeneous space (Hubbell 2001)

Among arthropods spiders have gained wide acceptance as indicators of environmentalquality (Pinkus-Rendoacuten Leoacuten-Corteacutes amp Ibarra-Nuacutentildeez 2006) as such their abundancespecies richness and community structure are useful indicators of the biodiversity ofthe biocoenosis as a whole (Willett 2001) Spider species richness has been correlatedwith latitude and mean annual temperature (Finch Blick amp Schuldt 2008 Whitehouseet al 2009) with habitat complexity and maximum regional temperature (Jimeacutenez-Valverde amp Lobo 2007) as well as with altitudinal gradients (Chatzaki et al 2005 Bowdenamp Buddle 2010) Spiders respond quickly to brusque changes in habitat heterogeneity(Rubio Corronca amp Damborsky 2008) and as a consequence of the narrow spatial

























































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factors that influence the beta-diversity of spider communities in

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