Bromeliads As Biodiversity Amplifiers and Habitat Segregation of Spider Communities in a Neotropical Rainforest

2010. The Journal of Arachnology 38:270–279 Bromeliads as biodiversity amplifiers and habitat segregation of spider communities in a Neotropical rainforest Thiago Gonçalves-Souza1, Antonio D. Brescovit2, Denise de C. Rossa-Feres1,andGustavo Q. Romero1,3: 1Departamento de Zoologia e Botaˆnica, IBILCE, Universidade Estadual Paulista, UNESP, Rua Cristo´vaõ Colombo 2265, CEP 15054- 000, Saõ Jose´ do Rio Preto, SP, Brazil; 2Instituto Butanta˜, Laborato´rio de Artro´podes Peçonhentos, Avenida Vital Brazil 1500, CEP 05503-900, Saõ Paulo, SP, Brazil Abstract. Although bromeliads can be important in the organization of invertebrate communities in Neotropical forests, few studies support this assumption. Bromeliads possess a three-dimensional architecture and rosette grouped leaves that provide associated animals with a good place for foraging, reproduction and egg laying, as well as shelter against desiccation and natural enemies. We collected spiders from an area of the Atlantic Rainforest, southeastern Brazil, through manual inspection in bromeliads, beating trays in herbaceous+shrubby vegetation and pitfall traps in the soil, to test if: 1) species subsets that make up the Neotropical forest spider community are compartmentalized into different habitat types (i.e., bromeliads, vegetation and ground), and 2) bromeliads are important elements that structure spider communities because they generate different patterns of abundance distributions and species composition, and thus amplify spider beta diversity. Subsets of spider species were compartmentalized into three habitat types. The presence of bromeliads represented 41% of the increase in total spider richness, and contributed most to explaining the high beta diversity values among habitats. Patterns of abundance distribution of the spider community differed among habitats. These results indicate that bromeliads are key elements in structuring the spider community and highlight the importance of Bromeliaceae as biodiversity amplifiers in Neotropical ecosystems. Keywords: Alpha and beta diversity, Atlantic rainforest, bromeliad-dwelling spiders, community structure, habitat type Habitat structural complexity (i.e., physiognomic diversity) they have leaves organized in a rosette, which usually form a plays an important role in population dynamics and in the tank that accumulates rainwater and nutrient-rich debris distribution and organization of animal communities in (Benzing 2000). Such characteristics result in a great variety of natural systems (Lawton 1983; Langellotto & Denno 2004; microhabitats for terrestrial (Romero & Vasconcellos-Neto Srivastava 2006). Structurally more complex habitats can 2005a, b; Romero 2006; Omena & Romero 2008) and aquatic increase food availability, provide more shelter against animals (Greeney 2001; Srivastava 2006; Balke et al. 2008), predators and climatic harshness and supply alternative which generally use bromeliads for foraging, reproduction, egg resources (Langellotto & Denno 2004). laying, nursery, and shelter against desiccation and natural Several studies have shown that habitat complexity (archi- enemies (Romero & Vasconcellos-Neto 2005a). For these tecture) is a key factor determining spider species richness and reasons, bromeliads were considered to be biodiversity composition (Robinson 1981; Greenstone 1984; Wise 1993; amplifiers (sensu Rocha et al. 2000). However, although Halaj et al. 2000; Langellotto & Denno 2004; Beals 2006). For various studies have suggested several advantages of brome- example, using an artificial structure made of wood and wire, liads for the fauna of Neotropical forests (Benzing 2000; Robinson (1981) showed that spiders with different foraging Greeney 2001; Romero 2006), to our knowledge there is no strategies use habitats according to their architectural study showing that these plants are important in structuring characteristics, which end up segregating the spiders into spider communities and as amplifiers of total richness and species subsets. If this experiment foretells the real spider beta diversity (i.e., species turnover among habitats: Tuomisto distribution in natural communities, structurally different & Ruokolainen 2006; Novotny et al. 2007). habitats will be represented by non-random species subsets Our hypothesis is that bromeliads are key elements of spider with lower percentages of shared species as habitat dissim- community structure and that they contribute to amplifying ilarity increases. Indeed, habitat structure is an important the diversity of these arthropods in Neotropical ecosystems. predictor of the spider communities in several natural To evaluate this hypothesis, we compared species abundance ecosystems (e.g., Halaj et al. 2000). distribution patterns (dominance curves) and species composi- Considering that most of the animals associated with the tion (beta diversity) of spiders in bromeliads, herbaceous+ plant family Bromeliaceae are habitat specialists (Greeney shrubby vegetation and ground habitats to test whether 1) 2001; Romero 2006; Balke et al. 2008; Omena & Romero species subsets that make up the spider Neotropical forest 2008), different habitat architectures could generate differ- community are compartmentalized in different habitat types entiated subsets of spider communities. Bromeliads occur (i.e., bromeliads, vegetation and ground) and 2) whether almost exclusively in Neotropical regions (with the exception bromeliads are important elements that structure spider of an African species: Benzing 2000) and represent an excellent communities because they generate different patterns of study system to investigate compartmentalization phenomena. abundance distributions and species composition, and thus Bromeliads are a good example of complex structures because amplify spider beta diversity. In this study, we consider total richness as the total number of spider species from the three 3 Corresponding author. E-mail: [email protected] habitat types (bromeliads, herbaceous and shrubby vegetation 270 GONÇ ALVES-SOUZA ET AL.—HABITAT SEGREGATION OF SPIDERS 271 and ground), and beta diversity as the difference in the spider higher than 3 m, and the distance between them varied from 1 species composition between habitats. to 3 m. Beating trays were made up of a 1 3 1 m square wooden beam frame holding a 1m2 cotton cloth; these trays METHODS were placed under the shrub to be sampled and, with the help Study site.—This work was done at the Santa Lućia of a stick, we beat the shrub 20 times so that the spiders would Biological Station (SLBS) (19u579S, 40u319W, 600–900 m fall onto the cloth. After this procedure, we preserved the asl), an area of 440 ha in Santa Teresa County, Espı´rito Santo spiders in 75% ethanol. State, southeast Brazil. The vegetation of SLBS is character- We collected ground spiders in 195 pitfall traps distributed ized as primary Atlantic Rainforest. The region has an average in 24 plots; the pitfall traps were set up inside each bromeliad rainfall of 1868 mm with November being the wettest month, plot. Each trap was 2 m (large plots) to 1.5 m (small plots) with an average rainfall of 268.8 mm and June the driest of the apart. The number of traps in each bromeliad patch varied year with 58.9 mm (for more details see Mendes & Padovan according to the size of the patch; ten and five ground traps 2000). were set up in large and small patches, respectively. Those At SLBS, the Bromeliaceae family is of great importance in plots in rocky outcrops (n 5 3) did not receive pitfalls. The the physiognomy of the vegetation, dominating various traps were made of plastic (500 ml) and contained approxi- stretches of forest understory, generally making up large mately 400 ml water, 10 ml detergent and 10 g thick salt. Each agglomerates of multispecific patches that occur naturally trap had a slab of polystyrene as a roof to avoid capturing between forests and rocky outcrops on shallow and structurally leaves and rainwater. Traps remained active in the field for poor ground (hereafter named ‘‘bromeliad patches’’: Wendt et seven days only during the sampling period, after which the al. 2008). Small patches vary from 0.005 to 0.14 ha and large material was collected, sorted in a laboratory and the spiders ones from 0.43 to 0.93 ha (see Wendt et al. 2008). The forest stored in 75% ethanol. Voucher specimens were deposited in vegetation, with a not-well-defined canopy stratification, is the Instituto Butantan (IBSP, Brazil). predominated by members of the family Myrtaceae (e.g., genus We used different sampling methods for each habitat type to Eugenia), followed by species of Ocotea (Lauraceae), Pouteria maximize spider collection. Each method used here is the most (Sapotaceae) and some Rubiaceae, Melastomataceae, Fabaceae appropriate for the purpose of this study (Santos 1999; and Arecaceae (see Thomaz & Monteiro 1997). Romero & Vasconcellos-Neto 2005a, b). Data surveying.—We sampled spiders from bromeliads, Statistical analyses.—We ran an individual-based rarefac- herbaceous and shrubby vegetation (hereafter called vegetation to control for variation in sampling effort among habitats tion) and ground in nine bromeliad patches 125 to 1031 m using the software EstimateS 8.0 (Cowell 2006); we used apart. Surveying was done in 24 permanent plots during ten confidence intervals of 95% for the three habitats. This sampling periods between February 2006 and September 2007, method allowed comparisons among unbalanced samples or in one-month intervals. Numbers of plots

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