the varia- tion in the plant-associated community is attributable to geography or to the ant–plant interaction. More impor- tantly, they do not tell us whether changes in invertebrate distributions from local to regional scales change ecosystem functions or whether convergence in community structure ensures that invertebrate food webs are functionally similar. The rosettes of many bromeliads (Bromeliaceae) form wells that collect water and organic detritus (phytotelmata), and provide a habitat for specialized aquatic organisms ranging from prokaryotes to invertebrates (Laessle 1961; Carrias, Cussac & Corbara 2001; Franck & Lounibos 2009). The invertebrate food web–inhabiting water-ﬁlled bromeliads is especially amenable to studies of aquatic–terrestrial interac- tions (Romero & Srivastava 2010), food web structure (Kit- ching 2000) and ecosystem function (Srivastava 2006), because it is small in size, can be exhaustively sampled and is naturally replicated throughout the neotropics. Some tank bromeliads such as Aechmea mertensii Schult.f. are involved in mutualistic associations with arboreal ants called ant gar- dens (AGs, reviewed in Orivel & Leroy 2011). In tropical
To link to this article : DOI:10.1371/journal.pone.0020538
URL : http://dx.doi.org/10.1371/journal.pone.0020538
To cite this version : Roux, Olivier and Céréghino, Régis and Solano, Pascal J. and Dejean, Alain. Caterpillars and fungal pathogens: two co-occurring parasites of an ant-plant mutualism. (2011)
To cite this version : Carrias, Jean-François and Brouard, Olivier and Leroy, Céline and Céréghino,
Régis and Pelozuelo, Laurent and Dejean, Alain and Corbara, Bruno. An ant-plant mutualism
induces shifts in the protist community structure of a tank-bromeliad. (2012) Basic and Applied
Ecology, vol. 13 (n° 8). pp. 698-705. ISSN 1439-1791
2015; animals: Smith et al., 2000; Telfer et al., 2003; Bowie et al., 2006; Anthony et al., 2007; Gonder et al., 2011; Nicolas et al., 2011). Notably, 10 of the 11 plant species investigated present a genetic discontinuity between populations north and south of latitude ~1-3°N. A similar genetic discontinuity is reported in the tree Barteria fistulosa Mast. (Passifloraceae) (Peccoud et al., 2013). This recurrent genetic discontinuity is even more intriguing because the region does not show any obvious physical barrier. It is therefore tempting to assume the existence of a reproductive barrier between north and south lineages of several Central African forest plants, indicating a broad pattern of incipient allopatric speciation. However, strong genetic discontinuities not matching any obvious physical barrier within continuous species ranges may simply constitute remnants of past
In conclusion, the results of the morphological, chemical, isotopic and reflectance analyses all point to N. bicalcarata being involved in a multifaceted nutritional mutualism with C. schmitzi. Because it seems to have lost some of the classical features involved in the carnivorous syndrome (absence of slippery wax and viscoelastic fluid, reduced acidity, putative absence of functional enzymes), Nepenthes bicalcarata may be viewed as a plant with an intermediate strategy between mutualism and antagonism. The ant symbiotic association is likely to have promoted a reduced harmful capacity in the antagonistic partner, i.e. the carnivorous plant, as expected by the theory of coevolution in some parasitic systems . Nevertheless, if the plant’s capacity to harm its specific ant symbiont has indeed been reduced by selection, we have also demonstrated that the association with the symbiotic ants represents an advantageous substitute for the carnivorous plant because it increases its efficiency as a predator of other insects (resulting in plants with more traps and more efficient trapping strategy). Therefore, this paradoxical but synergistic combination of carnivory and ant-plant mutualism results in a highly efficient nutrient sequestration strategy. This may explain why Nepenthes bicalcarata displays exceptional leaf life span and vegetative growth, reaching heights up to 20 m into the forest canopy , a record for the genus. Finally, this mixed strategy represents an outstanding adaptation for the exploitation of nutrient-poor soils and is, to our knowledge, unique in the plant kingdom.
described from any ant-plant system with fungiculture.
To address these questions, we investigated fungiculture by Azteca queens founding new colonies in young Cecropia trees (Urticaceae). In the genus Cecropia, a group of neotropical pioneer trees, 46 of the 61 species are associated with ants [ 27 ]. A recent multigene phylogeny inferred a single origin of the symbiotic relationship between Azteca ants and Cecropia plants, starting around 8 Mya ago [ 28 ]. The Cecropia hosts provide hollow stem internodes for hous- ing (domatia) and phyto-glycogen containing food bodies (Mu ¨llerian bodies) [ 29 ] for nutri- tion. The ants in return deter herbivores, prune their host trees from encroaching vegetation, and deposit extra nutrients within the hollow stem where they may be absorbed into the host tree’s tissue [ 30 – 32 ]. In hollow stem internodes of Cecropia inhabited by Azteca colonies, we regularly found chaetothyrialean fungi in small, clearly delimited patches. Some of the fungus strains found were shared among different Azteca species, while others were ant-species spe- cific [ 23 ]. This pattern indicates two possible scenarios of fungus recruitment: (1) random infection through spores or hyphal fragments from the environment, or (2) transmission from mother to daughter colony by the foundress queen. If foundress queens carry along fungi from their mother colonies, the distribution and frequency of fungal strains in foundress queen col- onized domatia should show the same pattern as observed in established colonies. If no such pattern is observable, the inoculation is suggested to originate from random infection.
AGs ( Madison, 1979 ; Benzing, 2000 ).
Divergence in flower size and shape among a plant popu- lation is largely explained on the basis of pollinator- or florivore-mediated selection. In the present study, we provide evidence for the first time of the importance of the identity of the mutualistic ants on inflorescence, floral and fruit traits. The strength and direction of this selection on floral and fruit traits change depending on the ant species, which may play a contrasting role in shaping plant evolution and specia- tion. However, as the reproductive biology of A. mertensii is still very poorly known, further experiments and studies are needed to better understand its breeding system and the mech- anisms of microevolution such as gene flow, as well as genetic drift and selection in the context of ant – plant interactions.
The recent discovery of bacteria and fungi associated with plant-ants (i.e., ants associated with myrmecophytes or plants providing them with a nesting place in the form of hollow structures called “domatia”) shed light on an overlooked role of microbiomes in ant-plant interactions [ 23 – 26 ]. It has also contributed to improving our understanding of how ants regulate their immediate environment and, thus, how they affect the diversity and functioning of the ecosystem. Moreover, myrmecophytes constitute a robust system that can be studied in order to answer such questions, since they are most often inhabited by one or a few specialized plant-ant species, with usually one colony per plant [ 27 – 29 ]. In addition, the environmental conditions provided by myrmecophytes can be considered as different from the surroundings, so that the microorganisms found inside the domatia are expected to differ according to the identity of both the associated ant species and the plant. As a consequence, both the local environment provided by the plant and the traits of the ant species might affect the diversity and composition of the associated microbial communities, which can be considered as a selection force or niche-filtering [ 30 , 31 ].
than a concentrated solution) across a 3-fold range of dilutions has been reported previously to only occur in ants after several hours or days [ 19–21 ].
Ants, like most animals, must ingest a full suite of essential amino acids to sustain their nutritional needs. Thus, the next question that arose was whether ants would be able to discrimi- nate essential amino acids from non-essential ones and whether this ability depends on the amino acid to carbohydrate ratio (AA:C). When ants that were deficient in both C and EAA were offered a solution containing sucrose combined with essential amino acids (EAA:C) versus a solution with non-essential amino acids (NEAA:C), ants focused their foraging effort on EEA:C, regardless of the AA:C ratio tested ( Figures 1 K and S1 D; Table S1 ; EAA:C was selected in 65 assays out of 72, p < 0.001 for all ratios tested; Data S2 D, ratio effect, p = 0.391). Interestingly, ants appeared to regulate the amount of both EAA and NEAA collected to an intake target ( Figure 1 M). Some NEAA are impor- tant regulators of key metabolic pathways that are necessary for maintenance, growth, reproduction, and immunity in organisms. NEAA can be synthetized de novo by the organism, but the pro- cess is costly, so regulating their consumption might be adaptive. Having demonstrated that ant colonies were able to distin- guish EAA from NEAA, we next examined the responses of
Ottawa, Canada, K1A 0R6 email@example.com ABSTRACT
An attempt is made to solve the Quadratic Assignment Problem through the development of a simplified ant colony system in C. Experiments with the implementation are per- formed and reported.
2 ACO-based structural optimization
Ant colony optimization (ACO) encompasses a large variety of optimization metaheuristics derived from the seminal work of Dorigo et al. in the early 90s [ 5 , 6 ]. Since then, ACO based heurstics have been proved to give remarkable results in a wide range of optimization problems, including DNA sequencing [ 7 ], scheduling [ 8 ], protein-ligand docking [ 9 ], assembly line balancing [ 10 ] and packet-switched routing [ 11 ]. ACO has been recognized as one of the most successful research lines in the area of swarm intelligence [ 12 , 13 ], and always seats beside evolutionary algorithms, iterated local search, simulated annealing, and tabu search among the top metaheuristic techniques [ 14 ].
Figure 2: Ant vs. simulation performances. (a) Heat map of trajectories of 200 simulation iterations over an example maze (brighter colors signify more visits, cubes are drawn in white). Actual ant trajectory for this maze is overlaid in blue. Initial location for all trajectories is marked by a green cogwheel. (b) Probabilities to solve the maze as a function of mean coverage, for ants (blue), pinball model (red), and extended pinball model (magenta) simulations. The percent of solvable mazes is depicted in black (up to 0.55 coverage - experimental mazes, 0.55 coverage and above - computer generated mazes). Sample sizes (from small coverage to large): Ants - 15,57,19,19,28,30, Pinball Model - 200 iterations each over 10,14,10,8,15,11 distinct mazes, Extended Pinball Model - 500 iterations each over 10,14,10,8,15,11 distinct mazes. Existence of Solution - (experimental - up to 0.55 coverage): 10, 14, 10, 8, 15, 11 (generated- 0.55 coverage and beyond): 100 for each coverage. (c) Comparison of average total arc length of ants’ and different types of simulations’ trajectories (color scheme as in (b)). The geodesic shortest path traversing the maze is shown in black. We take into account the different success rates of the simulation and ants as shown in panel (b) by adding a penalty to each iteration/experiment which was not successful. The added penalty equals average speed multiplied by the time stuck before termination of experiment/iteration. Error margins in (b,c) are standard errors of the mean. Wherever no error is visible, the error is small enough to fit within the filled circle marker. Sample sizes (from small coverage to large): Ants - 31,10,14,10,8,15,11, Simulations - as in (b) except the first point is 200/500 iterations in the no cubes case, Shortest Path - 10,14,10,8,15,11, first point is simply the width of the board. (d) The performance of different simulated models normalized by empirical ant performance. We use a single inverse measure for the performance of the simulations: L sim
enable us to estimate that A. mertensii may derive nitrogen from both ant species, but was affected differently depending on the ant partner (Fig. 1B). We demonstrate that A. mertensii—C. femoratus/Cr. levior associations can radically increase the amount of nutrients available to the host. Differences in stable N isotopic composi- tion could reflect the diversity and rich- ness of the macro- and microorganisms 11
INRIA - BIOCORE F-06902 - Sophia Antipolis firstname.lastname@example.org
Abstract—Modelling plant-pest interactions is not an obvious task since the involved processes are numerous and complex. We propose a minimal model based on trophic relations and the concept of plant compensation capacity. We only consider three main components in our system: the plant foliar biomass, the compensation capacity, and the pest population. We prove that there exist two threshold parameters, N1 and N2, and show that the system admits different equilibria, which are locally asymptotically stable or unstable, depending on the value of the previous threshold parameters. Finally, we summarize our theoretical results in a bifurcation diagram that allows to discuss possible control strategies to lower the impacts of the pest or even to obtain a better biomass yield.
In the humid tropics, bananas (Musa AAA genome) are mostly grown on bare soil and as a single crop. These semi- perennial agro- ecosystems contain regularly spaced banana plants and are extremely
simple and homogeneous and, therefore, are well suited for studying ant community structure. In the current study, we performed a pattern analysis at a fine spatial scale and provided information on temporal and spatial dynamics of ants foraging in a single- crop banana agroeco- system: (i) We assessed the diurnal and nocturnal foraging activity of these species; (ii) determined which species are dominant, subdomi- nant, and subordinate; (iii) assessed how numerical dominance at an impermanent resource (i.e., a bait) evolved through time; and (iv) as- sessed how abundance of species, at baits and in the neighborhood of the baits, were correlated.
Peptides are the predominant class of toxins in most arthropod venoms, and multiple AMPs have been reported in the venoms of scorpions [ 15 ], spiders [ 16 ], centipedes [ 17 ], wasps [ 18 ] and ants [ 19 , 20 ]. Our research group has previously isolated the antimicrobial polycationic and c-terminally amidated peptide bicarinalin in the venom of the myrmicine ant Tetramorium bicarinatum. Recent antimicrobial bioassay-based studies on several pathogens confirmed that bicarinalin is an effective and fast-acting molecule with a broad spectrum of antimicrobial activity and a moderate cytotoxicity against human lymphocytes [ 13 , 21 ]. Several studies argued that AMPs, including bicarinalin, are suitable for the development of novel preservatives in the food industry [ 22 ]. Given this, were the peptide used as a preservative it might also prevent some gastric diseases by acting against H. pylori once ingested.
With 89 species recorded, the ant fauna of Senegal can be considered as relatively diverse compared to the other neighbouring Sahelian countries such as Mali, or Niger, where 33 and 10 species respectively are now known (Taylor website), especially in view of the size of the country and that several important zones were not investigated. In particular, samples collected in the fruit-based agroecosystems from the “Niayes” and “Plateau de Thiès” regions show a high relative ant diversity. The climatic preferences of the species listed in this paper show Senegal to be an intermediate ecozone between North Africa and the sub-Sahara area. Our results show additions to the published ranges about Sahelian ant faunas and probably semi-arid ant species across sub-Saharan Africa.
The Fourth Refinement. One of the main purposes of the presented formal development is to formally establish the reachability of the main system goal: ”All the distributed food will be eventually transferred to the nest”. In the second refinement, we already proved that all the events affecting the food distribution are convergent and the amount of food outside the nest is constantly decreasing. However, this result does not concern the events modelling the ants moving in search of the food or drawn by the left pheromone, ants returning to the nest, etc. We have to ensure that the ants do not stay forever in such modes of operation. We can achieve this by deriving the necessary conditions (constraints) on the ant perception functions that essentially control ant movements.
such insects in this restricted foraging area. In the territorially- dominant arboreal ant species studied so far, workers ambush in a group permitting them to capture a wide range of insects that are spread-eagled, and only certain species need to use their venom (or pygidial gland secretion for Dolichoderinae) [7–11]. Note that spread-eagling the prey is possible based on the ability of workers discovering a prey to recruit nestmates situated within a radius of 20–30 cm thanks to the emission of a pheromone. This ‘short- range recruitment’ can be distinguished from ‘long-range recruitment’ that occurs when a foraging worker, not necessarily the individual discovering a large food source (or a large prey) returns to its nest laying a scent trail to recruit nestmates . In a non-dominant arboreal species, the workers, which hunt solitarily, capture a wide range of prey using their venom; however, when confronted with termites or competing arboreal ants defending a sugary food source, they use volatile secretions produced by their mandibular gland. The action at a distance of these secretions keeps them from having to come into contact with dangerous enemies .
Examination of the sequence of out- and nestbound ants at different levels of the bridge shows that clusters arise at the bridge bottleneck. Ants arriving in the bottleneck give way to
ants coming from the narrow part of the bridge and therefore accumulate at the level of the constrictions. When the path is free, the waiting ants cross the narrow part of the bridge, where they are given way by ants in the bottleneck at the other side. The mere presence of a bottleneck did not induce an additional delay in the ant progression, as shown by the fact that the ants that did not encounter another ant at the level of the bridge constriction spent the same amount of time crossing the bottleneck and the entrance. Examination of the sequence of inbound and outbound ants at different levels of the bridge shows that the clusters did not exist before the bottlenecks and thus that they were not formed at the departure from the nest or the food source.