Insect. Soc. DOI 10.1007/s00040-015-0440-4 Insectes Sociaux RESEARCH ARTICLE Size and condition of bamboo as structural factors behind the vertical stratification of the bamboo-nesting ant community 1 2 1 3 4,5 F. V. Arruda • M. A. Pesquero • D. G. Marcelino • G. A. Leite • J. H. C. Delabie • R. Fagundes6 Received: 11 April 2015 / Revised: 29 September 2015 / Accepted: 1 October 2015 Ó International Union for the Study of Social Insects (IUSSI) 2015 Abstract Nest-site limitation is an important factor reg- bamboo. Finally, we observed the species distribution along ulating ant diversity, particularly at low elevations. In a vertical gradient of bamboo height, and proposed that savannas, trees and shrubs do not support large nests in their differential colonization of ground and canopy-dwelling crowns and cavities for nest sites are limited. However, species and habitat specialization may be key mechanisms bamboos are very common and can provide vertically for the observed pattern of distribution. This study con- stacked hollow chambers for ants to establish their colonies. tributes to a better understanding of species coexistence in We evaluated the bamboo species Guadua paniculata as a low elevation forests in the Brazilian Cerrado by consider- source of nest cavities for ants in the Cerrado (Brazilian ing bamboo nest sites as a key factor affecting ant diversity. savanna). We hypothesized that the morphology of this bamboo species and its vertical arrangement regulate the Keywords Ant–plant interaction Á Species coexistence Á distribution of ants nesting in it. Thirty bamboo patches Cavity-nesting ants Á Limiting factors Á Canopy Á distributed among four sites in the state of Tocantins (Bra- Camponotus Á Azteca Á Guadua paniculata Á Brazil zil) were evaluated, in which 36 species of ants occupied more than half of the bamboo available. Wider and longer culms enabled a greater number of colonies of several ant Introduction species. Living or dead condition of bamboo had a signifi- cant effect on the diversity and composition of the ant fauna. Ants are the most abundant non-herbivorous insects in Dead culms were occupied opportunistically by several interactions with plants (Davidson et al. 2003). Ants forage generalist species, while Azteca fasciata dominated living on plants for food (prey and sugary secretions), and also build nests in plants as carton structures in association with epiphytes (i.e., gardening-ants), or using spaces provided by & R. Fagundes trunks, branches and leaves as physical resources (Ho¨ll- [email protected] dobler and Wilson 1990; Delabie et al. 1991). Cavities 1 Programa de Po´s-Graduac¸a˜o em Ecologia de Eco´tonos, harboring ant nests can be specialized structures like the Universidade Federal do Tocantins, Palmas, Brazil domatia of Acacia trees, natural cavities formed by tree bark 2 Universidade Estadual de Goia´s, Morrinhos, Brazil or resulting from wood death, cavities bored by some ant species, or even abandoned cavities created by wood-boring 3 Instituto Nacional de Pesquisa da Amazoˆnia (INPA), Manaus, Brazil beetles, galling insects or vertebrates (Ho¨lldobler and Wil- son 1990; Jolivet 1996; Blu¨thgen and Feldhaar 2010). In 4 Laborato´rio de Mirmecologia, CEPLAC/CEPEC, Itabuna, Brazil most cases, arboreal ants depend on natural cavities in vegetation for nesting because few are able to dig holes in 5 Departamento de Cieˆncias Agra´rias e Ambientais, Universidade Estadual de Santa Cruz, Ilhe´us, Brazil the wood (Jolivet 1996; Davidson et al. 2006). Nesting cavities are an important limiting resource for the dispersion 6 Departamento de Biodiversidade Evoluc¸a˜o e Meio Ambiente, Universidade Federal de Ouro Preto, Ouro Preto, MG of ants because they need these sites to establish their col- 35400-000, Brazil ony, tend brood and subsequently expand their population 123 F. V. Arruda et al. (Powell 2008, 2009; Fonseca 1993). However, cavities have culms by ants might be a combination of habitat special- limited availability and low durability opposed to the high ization of ant species, related to the bamboo size and importance as nest resource (Powell 2008, 2009), and are, condition. Based on that we have four predictions: (1) thus, a key resource for ants. Therefore, studies of nest-site bamboo with greater size will accumulate more nests of limitation are imperative to understand ant diversity and different ant species due to the greater quantity of sites for distribution (Powell et al. 2011). nesting; (2) live bamboo will have more nests than dead In Neotropical ecosystems, bamboo culms are an bamboo due to the higher habitat stability and protection important source of nesting cavities for generalist and spe- against predators; (3) the fauna nested in dead bamboo cialist ant species (Kohout 1988; Buschinger et al. 1994; would be different from that nested in living bamboo due to Cobb et al. 2006; Davidson et al. 2006; Dorow and the difference in resource quality; and (4) ant species would Maschwitz 1990; Fagundes et al. 2011). Cavity-nesting ants be distributed along the bamboo height in a vertically take advantage of pre-existing openings in the internodes, stratified pattern in response to bamboo size, predicting a typically made by wood-boring beetles (Fagundes et al. differential colonization of ground and arboreal nesting 2011) and woodpecker birds (Leite et al. 2013). Bamboo is a species. resistant shelter, protecting the colony against predators and providing stable conditions for its growth (Powell 2008, 2009; Leite et al. 2013). In fact, both soil and vegetation ants Methods nest opportunistically in bamboo (Cobb et al. 2006; Fagundes et al. 2011), especially those of the genus Cam- We collected the data in four areas of Cerrado in the county of ponotus (Davidson et al. 2006; Leite et al. 2013), although Pium (State of Tocantins, Brazil; 49°4605400W10°2903000S), in some ant species have specialized adaptations for living in the basin of Araguaia River. We conducted the field study bamboo (Davidson et al. 2006). Once installed, the colonies between August 2008 and January 2010. The altitude ranges seek prey throughout the soil or vegetation (Davidson et al. from 200 to 300 m and the climate is warm and humid 2006) or keep honeydew-producing hemipterans within the (24–35 °C) with rainy season extending between November nest (Delabie 2001). Therefore, bamboo patches are and April (Leite et al. 2013). The areas were distributed in four important for ants because they provide nesting cavities, fragments 5–10 km apart: Javae´sFarm(JF;1400haoffor- structure habitats, and serve as foraging area. est); Ouro Verde Farm (OV; 1600 ha); Brazil Palmeira Farm The distribution of ants in bamboo may be regulated by (BPF; 440 ha; Leite et al. 2013)andCanguc¸u Reserve (MST; three major factors. First, the bamboo shape and the struc- 10 ha). These areas have a typical vegetation known as Cer- ture. For example, bamboo with long and erect culms rada˜o. Cerrada˜o is a type of Cerrado (Brazilian savanna) presents high incidence of ant nests (Davidson et al. 2006; composed of densely spaced tall tree species (10–20 m) (Silva Fagundes et al. 2011), which could be enhanced by the and Bates 2002). Within the Cerrada˜o, the dominant bamboo presence of holes of various sizes (Fagundes et al. 2011). Guadua paniculata Munro (Poaceae) grows in dense clumps Second, live culms are resistant shelters against predators (Leite et al. 2013). G. paniculata is a perennial bamboo with and provide stable conditions for colony growth, whereas erect stems which grow to an average height of 10 m and dead bamboo culms are easily broken and may not protect diameter of 20 cm; and form dendroid lateral branches and a against rain, heat and occasional fire (Powell 2008, 2009; few roots emerging from nodes (Clayton et al. 2006). Bamboo Leite et al. 2013). Third, the dispersion range of ant species stems are called culms, and consist of stacks of chambers and its distribution along the ground-canopy gradient called internodes that are isolated from each other by solid (Davidson et al. 2006; Yanoviak and Kaspari 2000). regions called nodes. Ground-nesting ants commonly occupy cavities in the trunk We established sampling plots at least 500 m apart on or lower branches of trees, while typically arboreal species each of the four areas. We marked 30 sampling plots in can be found nesting throughout the plant stratum (Vas- total: thirteen in BPF area, eight in JF, seven in OV, and two concelos e Vilhena 2006; Camacho and Vasconcelos 2015; in MST. At each sample plots, we randomly selected 15 live Yanoviak and Kaspari 2000). This stratified pattern of ant and 15 dead culms of G. paniculata (N = 900). Since distribution may be true for ants in bamboo, although it has bamboo reproduces by cloning, we considered the 30 not yet been investigated. sampled culms of each bamboo plot as a single individual In this study, we evaluated the bamboo Guadua panic- bamboo (samples) and each sampled area as a population ulata as a source of nest sites for ants in bamboo forests in (spatial replicates). We measured the circumference and the Brazilian Cerrado. We described the ant fauna associ- length of each culm. We searched for ant nests within each ated to the bamboo G. paniculata and the effect of its size internode opening the entire culm. We quantified the and condition (dead or alive) on the structure of ant com- number of nests and the nest position (distance from the munity. We hypothesized that the colonization of bamboo stem base) in each culm. The collected ant samples were 123 Size and condition of bamboo as structural factors behind the vertical stratification of the… identified at the Myrmecology Laboratory (CEPLAC/ nests), Pseudomyrmex (6; 8 %) and Crematogaster (6; 4 %) CEPEC, BA, Brazil) where vouchers were deposited under were the most diverse and common genera.
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