The relationship between soil variables and leafcutter ant (Atta sexdens) nest distribution in the Colombian Amazon

Abstract

We determined the relationships between several soil variables and the distribution of leafcutter ant (Atta sexdens) nests on the Colombian shore of the Amazon River. Seven habitats were identified in which nests were consistently present or absent. Soil samples for physiochemical analysis were taken near nest sites in three habitats where nests were present and from randomly selected sites in four other habitats where nests were absent. Percent canopy cover and soil resistance were also measured for each site. Almost all of the 20 identified soil variables were significantly different between habitats with and without A. sexdens nests, and the values of all variables were heterogeneous between the seven habitats. The most important variables correlated with leafcutter ant nest presence were percent canopy cover (positively), percent silt, soil resistance at 0-20 cm, and pH (all negatively). We deduced a binomial and a multinomial logistic regression which showed how each of these variables was related to nest presence and habitat, respectively. We describe how each variable may affect leafcutter ant nest development, especially in its earliest stages, and therefore influences nest distribution. We propose a suitable-soil hypothesis which, complementary to the palatable forage hypothesis, aims to explain patterns in leafcutter ant nest demography based on soil conditions.

Does inundation risk affect leaf-cutting ant distribution? A study along a topographic gradient of a Costa Rican tropical wet forest

“…Van Gils et al . (2010) found negative correlations between soil properties (e.g. per cent silt, soil resistance and pH) and Atta sexdens nest distribution.…”

“…In fact, the elevated nest density of LCAs at secondary forests has been particularly associated to proliferation of pioneer plants (Silva et al 2009). However, demographic patterns of LCAs may be complementarily attributed to soil physicochemical variables (suitable-soil hypothesis; van Gils et al 2010).…”

“…However, demographic patterns of LCAs may be complementarily attributed to soil physicochemical variables (suitable-soil hypothesis; van Gils et al . 2010). Van Gils et al .…”

“…Although van Gils et al . (2010) have proposed a suitable-soil hypothesis acting complementary with the palatable forage hypothesis, no relation between nest density and size with soil consociations was observed. Besides, nest density did not vary between alluvial and volcanic soils, even though there is a notable and known difference among them (IUSS Working Group WRB 2006).…”

Nesting architecture and population structure of the fungus-growing antCyphomyrmex transversus(Formicidae: Myrmicinae: Attini) in the Brazilian coastal zone of Ilhéus, Bahia

“…Moreover, considering that Cyphomyrmex contains approximately 37 cataloged species (Price et al 2003), studies on this group are concentrated on relatively few species, such as C. costatus (Weber 1957), C. longiscapus (Mueller & Wcislo 1998;Schultz et al 2002), C. muelleri (Schultz et al 2002) and C. morschi (Klingenberg et al 2007). Although nesting biology in fungus-growing ants is extremely species-specifi c, diverse abiotic and biotic conditions are recognized as key factors that aff ect founding queen nesting behavior, nest architecture and, consequently, nest distribution (Jonkman 1980;Hölldobler & Wilson 1990;Mayhé-Nunes 1995;Leal 1998;Moreira et al 2004a;Soares et al 2006;Vasconcelos et al 2006;Verza et al 2007;Silva et al 2009;van Gils et al 2010). For example, according to Vasconcelos et al (2006), founding queens of the leaf-cutter ant Atta laevigata prefer to nest on bare soil rather than on soil covered by leaf litter.…”