Metapopulation processes affecting diversity and distribution of myrmecophiles associated with red wood ants (original) (raw)
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Mechanisms driving the specificity of a myrmecophyte-ant association
Biological Journal of the Linnean Society, 2009
In the understory of pristine Guianese forests, the myrmecophyte Hirtella physophora almost exclusively shelters colonies of the plant-ant Allomerus decemarticulatus in its leaf pouches. We experimentally tested three nonmutually exclusive hypotheses concerning phenomena that can determine the species specificity of this association throughout the foundation stage of the colonies: (1) interspecific competition results in the overwhelming presence of A. decemarticulatus queens or incipient colonies; (2) exclusion filters prevent other ant species from entering the leaf pouches; and (3) host-recognition influences the choice of founding queens, especially A. decemarticulatus. Neither interspecific competition, nor the purported exclusion filters that we examined play a major role in maintaining the specificity of this association. Unexpectedly, the plant trichomes lining the domatia appear to serve as construction material during claustral foundation rather than as a filter. Finally, A. decemarticulatus queens are able to identify their host plant from a distance through chemical and/or visual cues, which is rarely demonstrated in studies on obligatory ant-plant associations. We discuss the possibility that this specific host-recognition ability could participate in shaping a compartmentalized plant-ant community where direct competition between ant symbionts is limited.
Some ecological theories predict a positive relationship between species richness and resource size, resource abundance, or resource concentration. In this study, we tested these three hypotheses with myrmecophilous beetles, which use ant nests as their hosts. The resource concentration hypothesis predicts that patches with a high density of a resource support high richness of species dependent on that specific resource. The resource abundance hypothesis predicts that the hosts offering more resources support more species. The resource size hypothesis predicts that larger hosts support more species than smaller hosts. We collected beetles from nests of the nest building wood ant Formica aquilonia. In 49 F. aquilonia nests, we observed 965 individual beetles and 16 species of myrmecophilous beetle. Both the nearest neighbour distance and the volume of ant nests influenced species richness and beetle number. The beetle species utilising several hosts were more widespread and more abundant than the specialist beetle species. Thus, our findings support the resource concentration, resource size and resource abundance hypotheses.
BMC Evolutionary Biology, 2016
Background: A host infected with multiple parasitic species provides a unique system to test evolutionary and ecological hypotheses. Different parasitic species associated with a single host are expected to occupy different niches. This niche specialization can evolve from intraguild competition among parasites. However, niche specialization can also be structured directly by the host when its defence strategy depends on the parasite's potential impact. Then it can be expected that species with low or no tendency to prey on host brood will elicit less aggression than severe brood parasitic species and will be able to integrate better in the host system. We examined this hypothesis in a large community of symbionts associated with European red wood ants (Formica rufa group) by testing the association between 1) level of symbiont integration (i.e. presence in dense brood chambers vs. less populated chambers without brood) 2) level of ant aggression towards the symbiont 3) brood predation tendency of the symbiont. Results: Symbionts differed vastly in integration level and we demonstrated for the first time that relatively unspecialized ant symbionts or myrmecophiles occur preferentially in brood chambers. Based on their integration level, we categorize the tested myrmecophiles into three categories: 1) species attracted to the dense brood chambers 2) species rarely or never present in the brood chambers 3) species randomly distributed throughout the nest. The associates varied greatly in brood predation tendency and in aggression elicited. However, we did not find a correlation for the whole myrmecophile community between a) brood predation tendency and host's aggression b) integration level and host's aggression c) integration level and brood predation tendency. Conclusions: Our results indicate that red wood ants did not act more hostile towards species that have a high tendency to prey on brood compared to species that are less likely or do not prey on brood. We show that potentially harmful parasites can penetrate into the deepest parts of a social insect fortress. We discuss these seemingly paradoxical findings in relation to models on coevolution and evolutionary arms races and list factors which can make the presence of potentially harmful parasites within the brood chambers evolutionary stable.
Do non-myrmocophilic epiphytes influence community structure of arboreal ants?
Basic and Applied Ecology, 2003
In a one-year-survey in Panama we examined the influence of a tree crown's epiphyte assemblage on its ant fauna. Ants were collected with various types of insect traps in 25 crowns of Annona glabra trees. The study trees were assigned to three different categories according to their epiphyte load, and to an epiphyte-free control group. We collected 22,335 specimens of 91 morphospecies, 32 genera and six subfamilies. By far the most abundant species was Solenopsis zeteki, a minute Myrmicinae, which was found in each of the 25 study trees. Many other species were also rather common and widely distributed throughout the study area. Only six species were singletons. Measures of αand β-diversity, species abundance and species composition were not affected by the epiphyte load of a tree. We also made direct in situ observations of ants on 34 additional Annona glabra trees with and without epiphytes. Workers were attracted with tuna and sugar baits, and interspecific interactions and nesting sites were recorded. In total, 40 species of ants were found, all of which had also been collected in the traps. Almost half of the colonies (48%) used dead wood as nesting substrate, while 29% nested in epiphytes. Consistent with the results of the trap survey, the epiphyte load of the study trees had no influence on ant species richness and composition, but a significant correlation between ant abundance and epiphyte load was detectable. In both data sets, the lack of associations between ant species indicated that the ant assemblages were not structured in a mosaic-like fashion. We conclude that epiphytes do hardly influence the composition of ant assemblages in the studied tree crowns, probably because arboreal ants are highly opportunistic with respect to their host plants.
Biological Journal of the Linnean …, 2010
Interactions between potentially mutualistic partners can vary over geographic areas. Myrmecophytes, which are plants harbouring ants, often do not exhibit sufficient intraspecific variability to permit comparative studies of myrmecophytic traits over space or time. Humboldtia brunonis (Fabaceae), a dominant, endemic myrmecophyte of the Indian Western Ghats, is unique in exhibiting considerable variability in myrmecophytic traits, e.g. domatia presence, as well as domatia occupancy and associated ant diversity throughout its geographic range. Although its caulinary domatia are occupied by at least 16 ant species throughout its distribution, young leaves and floral buds producing extrafloral nectar (EFN) are protected by ants from herbivory only in the southernmost region, where Technomyrmex albipes (Dolichoderinae) is the most abundant ant species. The extent of protection by ants was positively related to local species richness of ants and their occupancy of domatia. On the other hand, the highest abundance of interlopers in the domatia, including non-protective ants, the arboreal earthworm Perionyx pullus, and other invertebrates, occurred in sites with the least protection from herbivory by ants. Whereas domatia morphometry did not vary between sites, domatia occupied by protective ants and invertebrate interlopers were longer and broader than empty ones at all sites. The lowest percentage of empty domatia was found at the southernmost site. There was a progressive decline in ant species richness from that found at the sites, to that feeding on H. brunonis EFN, to that occupying domatia, possibly indicating constraints in the interactions with the plants at various levels. Our study of this dominant myrmecophyte emphasizes the impact of local factors such as the availability of suitable ant partners, domatia occupancy, and the presence of interlopers on the emergence of a protection mutualism between ants and plants.
Oecologia, 2003
Social organisation of colonies of obligate plant-ants can affect their interaction with myrmecophyte hosts and with other ants competing for the resources they offer. An important parameter of social organisation is whether nest sites of a colony include one or several host individuals. We determined colony boundaries in a plant-ant associated with the rainforest understorey tree Leonardoxa africana subsp. africana, found in coastal forests of Cameroon (Central Africa). This myrmecophyte is strictly associated with two ants, Petalomyrmex phylax and Cataulacus mckeyi. Plants provide food and nesting sites for P. phylax, which protects young leaves against insect herbivores. This mutualism is often parasitised by C. mckeyi, which uses but does not protect the host. The presence of C. mckeyi on a tree excludes the mutualistic ant. Because Petalomyrmex -occupied trees are better protected, their growth and survival are superior to those of Cataulacus -occupied trees, giving P. phylax an advantage in occupation of nest sites. C. mckeyi often colonises trees that have lost their initial associate P. phylax, as a result of injury to the tree caused by disturbance. Polydomy may allow C. mckeyi to occupy small clumps of trees, without the necessity of claustral colony foundation in each tree. Investigating both the proximate (behavioural repertoire, colony odour) and the ultimate factors (genetic structure) that may influence colony closure, we precisely defined colony boundaries. We show that colonies of C. mckeyi are monogynous and facultatively polydomous, i.e. a colony occupies one to several Leonardoxa trees. Workers do not produce males. Thus, the hypothesis that polydomy allows workers in queenless nests to evade queen control for their reproduction is not supported in this instance. This particular colony structure may confer on C. mckeyi an advantage in short-distance dispersal, and this could help explain its persistence within the dynamic Leonardoxa system.