The role of parabiotic ants and environment on epiphyte composition and protection in ant gardens

Abstract

IntroductionMutualism is a ubiquitous interspecific interaction that occurs among a great diversity of living organisms (Janzen, 1985). Plants and insects, in particular, are frequently involved in three types of mutualisms: pollination, seed dispersal and protection against herbivores (Bronstein, 1994;Bronstein et al., 2006). In these interactions, plants attract and reward insects for their actions by offering shelter and/or food through specialized structures, while insects guarantee flower pollination, seed dispersal or protection against consumers (Bronstein et al., 2006).Although the majority of plant-insect mutualisms are generalized and facultative (Stanton, 2003;Bronstein et al., 2006), some interactions can be very specialized (see RicoAbstract Ant gardens (AGs) are a multi-partner specialized ant-plant interaction involving several ant and epiphyte species. Although studies on AGs have reported possible roles for some species in this system, there are unanswered questions regarding the process of epiphyte incorporation in the AGs and the role of less aggressive ant species in AG protection. In this study, we used AGs in the Brazilian Amazon forest formed by two parabiotic ant species to test a set of hypothesis regarding two main questions: 1) How is AG plant community composition affected by the surrounding environment? 2) Does Crematogaster levior play a role in the chemical detection of herbivory in the AGs? After identifying epiphytes occurring at AGs at the forest edge and in the interior, we found that ant gardens in each environment exhibited different compositions, and that plant species bearing oil or extrafloral nectar glands were more frequent in AGs located in the forest interior than in those at the forest edge. By performing experiments with volatile compounds emitted from injured epiphytes, we detected that only Camponotus femoratus was responsive, responding almost eight times faster in response to plant extracts than water treatments. Our results support the idea that environmental conditions affect ant preference for feeding resources provided by epiphytes and consequently shape the structure of the epiphyte community in AGs. On the other hand, the role of C. levior in AGs remains unknown, since it seems to play no direct or indirect role in AG protection.

Diversity and interactions of the epiphyte community associated with ant‐gardens are not influenced by elevational and environmental gradients

“…We also observed that abandoned ant-gardens may be occupied by the opportunistic ant species Dolichoderus bispinosus (MacKay, 1993). We recorded 15 species of epiphytes associated with the ant-gardens, but less than half are true AG epiphytes (Orivel & Leroy, 2011;Morales-Linares et al, 2016) et al, 2016) or between the interior and the edge of the forest (Leal et al, 2017), even when associated with one or two (parabiosis) true AG ant species (Dejean et al, 2000). However, the richness and composition of the AG epiphytes did not differ in relation to vegetation type (RF and SESF), which can be explained by the presence of a single true AG ant species.…”

Structure and robustness of the Neotropical ant‐gardens network under climate change

“…The limitations of our predictions are the use of co‐occurrences instead of real interactions (Blanchet et al ., 2020) and not considering the individual capacity of the AG ant and epiphyte species to disperse or adapt to different habitats (Morales‐Linares et al ., 2016; Chomicki et al ., 2017; Leal et al ., 2017; Leroy et al ., 2017), as well as the importance of the AG host trees (Davidson, 1988; Kaufmann & Maschwitz, 2006; Morales‐Linares et al ., 2016). Furthermore, we did not evaluate the ability of the species to switch partners (rewiring of interactions) in the simulated extinctions (Schleuning et al ., 2016).…”

“…Selection of the six AG ant and 16 epiphyte species was based on the review of Orivel & Leroy (2011), and recent studies of the diversity of Neotropical AGs (e.g., Morales‐Linares et al ., 2016; Leal et al ., 2017; Supporting Information Figure S1). The nomenclature of the AG ant and epiphyte species was homogenised ( sensu Orivel & Leroy, 2011), and the parabiotic ants (e.g., Crematogaster levior Longino, 2003) excluded, i.e., those species that co‐inhabit with the AG ants but do not construct AGs, as well as epiphyte species that are rarely seen in the AGs or those with no confirmation of their seed dispersal by AG ants (e.g., Columnea linearis Oerst.).…”

Basic ecology of ant gardens in a dry-premontane transitional forest

“…AGs have been reported in humid tropical ecosystems and near water bodies (Yu, 1994). The composition of epiphytes in AGs is influenced by ant species and AG size, among other factors (Leal et al, 2017). AGs have high ecological value because the mutualistic relationship allows them to hold water and nutrients, harbor an associated fauna, and facilitate vascular epiphytes (Céréghino et al, 2010).…”

“…AGs have high ecological value because the mutualistic relationship allows them to hold water and nutrients, harbor an associated fauna, and facilitate vascular epiphytes (Céréghino et al, 2010). However, there are still questions regarding the natural history of AGs (Leal et al, 2017). In addition, studies on ecosystems other than humid tropical forests and Colombian ecosystems, in general, are scarce (Bader, 1999).…”