The role of Senescent Stem-Galls over Arboreal Ant Communities Structure in Eremanthus erythropappus (DC.) MacLeish (Asteraceae) Trees

Abstract

The extensive occupation of canopy trees by ants can be attributed to many factors, such as the presence of structures that provide food and shelter. Structures induced by other insects in host plants, like senescent galls, can provide shelter and a nesting place for many species of ants. The main objectives of this work were: (1) to describe the ant communities found in canopies of candeia trees (Eremanthus erythropappus), including the species which use galls as nesting sites; (2) verify the role of galls in determining the structure and composition of the ant communities and (3) to evaluate whether the size and shape of galls are important to the choice of nesting sites by ants. Specifically, the following questions were investigated: 1 – Are larger galls more frequently occupied by ants than smaller galls? 2 – Does gall shape (globular and fusiform) influence occupation? 3 – Which species of ants are present in the canopies of candeias and which are occupying galls? Senescent galls were collected in locations in the southern portion of the Espinhaço Mountain Range, state of Minas Gerais, southeastern Brazil. In total, 3,195 galls were collected and 19 ant species were recorded. Only 176 galls (5.5%) had been occupied by ants, and these were represented by 11 species. The most frequent species found occupying galls were Myrmelachista nodigera, with 48 colonies; Nesomyrmex spininodis, with 37 colonies; and Crematogaster complex crinosa sp. 1, with 29 colonies. The ants occupied galls with greater volume and diameter. Even considering the low occupation frequency, senescent galls in E. erythropappus are used by ants, either as outstations or satellite nests of polydomic colonies, and may be important in determining ant species composition in canopy trees.

Arthropod facilitation mediated by abandoned dead domatia

“…We found that almost 88% of dead domatia that were occupied by ants did not contain an ant queen. Similar results have also been reported by other abandoned structures made by insects, such senescent galls and wood‐boring beetle abandoned cavities, which are mainly colonized by ant species that develop polydomic colonies (Almeida et al 2014, Santos et al 2017, Novais et al 2017). The construction of polydomic nests is a strategy to increase the distribution of the colony in order to avoid predation and reduce local intraspecific competition for the same resources by bringing workers closer to new food sources (Debout et al 2007, Lanan et al 2011, Robinson 2014).…”

“…These new habitats might persist on plants and can be later used as shelter by other arthropods in a facilitative interaction process (Vieira and Romero 2013, Cornelissen et al 2016, Zuo et al 2016, Novais et al 2018). Particularly, ants can take advantage of the abandoned shelters made by other insects for nesting, such as wood‐boring beetle abandoned cavities (Tschinkel 2002, Satoh et al 2016, Novais et al 2017), senescent galls (Fernandes et al 1988, Mehltreter et al 2003, Almeida et al 2014, Santos et al 2017, 2019), and empty cocoons (Raath et al 2017).…”

Gall-Colonizing Ants and Their Role as Plant Defenders: From ’Bad Job’ to ’Useful Service’

“…Another is that larger galls could prove useful in a subsequent “ergonomic phase” of colony growth when the housed population presumably is subject to a large increase [46]. Although referring to a tropical plant, studies on candeia trees ( Eremanthus erythropappus ) showed similar patterns in gall size preferences: larger galls have higher rates of occupation by ants [23,52].…”

“…scutellaris too, implying a division of a colony’s section into several nesting sites [59,61,62,63]. An alternative use of galls by ants is that of “outstations” as reported on candeia trees [23]. An outstation is a pre-existing structure in the environment used as a rest area or a shelter during territory patrolling, eventually enabling the ants to respond to nest invasions/disturbances quickly [64,65].…”

“…The gall secondary fauna also includes a number of ant species belonging to different subfamilies and widespread in several habitats [18,20,21,22,23]. Tόrossian, [20,21] found that ant species in temperate environments differed in their choice of galls to colonize according to the position of galls on plants, whereas in tropical areas, gall size seemed to play a major role [23]. In both cases, the results showed that galls could host colonies at different life stages or with different compositions (e.g., only queen, only adults, adults and brood, or adults, brood and queen).…”