Éditeur(s) : Institut de Ciències del Mar de Barcelona, CSIC
Résumé : The main characteristics of the biology of bigeye scad were studied from commercial fishery catches around Reunion Island. Biometric relationships were calculated. The monitoring of size distribution, aggregated by month, allowed us to estimate the theoretical growth equation using the ELEFAN software. The von Bertalanffy growth parameters were adjusted with a seasonal modulation: L8 = 265 mm; K = 1.64 year-1; c = 0.068; ? = 0.38. The growth of the cohort was quite high during the austral summer (November-April) and decreased during the austral winter (May-October). The arrival of a new cohort with homogeneous small sizes (65 to 90 mm) in the fishery in November coincided with the disappearance of large individuals. A feature of the reproductive biology was that the sex ratio remained constant month by month and that there was no predominance of male or female even in the larger size classes. Fish were mature by April and the proportion of mature fish progressively increased until November, when the gonad-indices were the highest. The size at first maturity (L50) was reached at 215 mm (fork length). The largest specimens observed were 255 mm long (fork length). After reproduction, massive mortality occurred and few individuals survived.
Scientia Marina (0214-8358) (Institut de Ciències del Mar de Barcelona, CSIC), 2007-03 , Vol. 71 , N. 1 , P. 137-144

Droits : 2007 CSIC
http://archimer.ifremer.fr/doc/2007/publication-2335.pdf
http://archimer.ifremer.fr/doc/00000/2335/

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
We assessed the occurrence of algae in five species of tank-bromeliads found in contrasting environmental sites in a Neotropical, primary rainforest around the Nouragues Research Station, French Guiana. The distributions of both algal abundance and biomass were examined based on physical parameters, the morphological characteristics of bromeliad species and with regard to the structure of other aquatic microbial communities held in the tanks. Algae were retrieved in all of the bromeliad species with mean densities ranging from ∼10(2) to 10(4) cells/mL. Their biomass was positively correlated to light exposure and bacterial biomass. Algae represented a tiny component of the detrital food web in shaded bromeliads but accounted for up to 30 percent of the living microbial carbon in the tanks of Catopsis berteroniana, located in a highly exposed area. Thus, while nutrient supplies are believed to originate from wind-borne particles and trapped insects (i.e., allochtonous organic matter), our results indicate that primary producers (i.e., autochtonous organic matter) are present in this insectivorous bromeliad. Using a 24-h incubation of size-fractionated and manipulated samples from this plant, we evaluated the impact of mosquito foraging on algae, other microorganisms and rotifers. The prey assemblages were greatly altered by the predation of mosquito larvae. Grazing losses indicated that the dominant algal taxon, Bumilleriopsis sp., like protozoa and rotifers, is a significant part of the diet of mosquito larvae. We conclude that algae are a relevant functional community of the aquatic food web in C. berteroniana and might form the basis of a complementary non-detrital food web.
ISSN: 1932-6203

hal-00819161
https://hal.archives-ouvertes.fr/hal-00819161
https://hal.archives-ouvertes.fr/hal-00819161/document
https://hal.archives-ouvertes.fr/hal-00819161/file/Brouard2011_AreAlgae.pdf
DOI : 10.1371/journal.pone.0020129

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
ISSN: 1932-6203

hal-01090647
https://hal-agroparistech.archives-ouvertes.fr/hal-01090647
DOI : 10.1371/journal.pone.0008957

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Plant-ants live in a mutualistic association with host plants known as "myrmecophytes" that provide them with a nesting place and sometimes with extra-floral nectar (EFN) and/or food bodies (FBs); the ants can also attend sap-sucking Hemiptera for their honeydew. In return, plant-ants, like most other arboreal ants, protect their host plants from defoliators. To satisfy their nitrogen requirements, however, some have optimized their ability to capture prey in the restricted environment represented by the crowns of trees by using elaborate hunting techniques. In this study, we investigated the predatory behavior of the ant Azteca andreae which is associated with the myrmecophyte Cecropia obtusa. We noted that up to 8350 ant workers per tree hide side-by-side beneath the leaf margins of their host plant with their mandibles open, waiting for insects to alight. The latter are immediately seized by their extremities, and then spread-eagled; nestmates are recruited to help stretch, carve up and transport prey. This group ambush hunting technique is particularly effective when the underside of the leaves is downy, as is the case for C. obtusa. In this case, the hook-shaped claws of the A. andreae workers and the velvet-like structure of the underside of the leaves combine to act like natural Velcro that is reinforced by the group ambush strategy of the workers, allowing them to capture prey of up to 13,350 times the mean weight of a single worker.
ISSN: 1932-6203

hal-00818187
https://hal.archives-ouvertes.fr/hal-00818187
https://hal.archives-ouvertes.fr/hal-00818187/document
https://hal.archives-ouvertes.fr/hal-00818187/file/Dejean2010_Arboreal.pdf
DOI : 10.1371/journal.pone.0011331

Résumé : This document presents a survey of the marine-related activities in France, i.e. those of the commercial sector (exploitation of minerai and living resources, manufacturing industries, services) and those of the public sector (Navy, State services, education, safety, marine research). A chapter is devoted to the protection of the coastal and marine environment, and the chapter on tourism gives quantitative data on the impacts of the pollution caused by the Erika oil-tanker. Each activity of the commercial sector is described by key-figures (turnover, value added, employmentl. The description of the non-commercial public sector includes data on costs, including personnel costs. In addition to these figures, qualitative information is given on the recent development, present situation and outlook for each activity
Ce document présente un panorama des activités liées à la mer en France, c'est-à-dire du secteur industriel (exploitation des ressources minérales et vivantes, industrie manufacturière, services) et celles du secteur public non marchand (Marine nationale, services de l'État, enseignement, sécurité, recherche marine). Un chapitre est consacré à la protection de l'environnement littoral et marin, et le chapitre sur le tourisme donne des indications quantitatives sur les impacts de la pollution causée par le navire pétrolier Erika. Chaque activité du secteur industriel est décrite par des chiffres-clés (chiffre d'affaires, valeur ajoutée, emploi). Pour le secteur public non marchand, sont fournies des données sur les coûts, notamment les coûts de personnel. Ces indicateurs sont accompagnés d'informations qualitatives sur l'évolution récente , la situation actuelle et les perspectives de chaque activité.

Droits : 2002 Ifremer
http://archimer.ifremer.fr/doc/00117/22850/20660.pdf
http://archimer.ifremer.fr/doc/00117/22850/53085.pdf
http://archimer.ifremer.fr/doc/00117/22850/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Zelus annulosus is an assassin bug species mostly noted on Hirtella physophora, a myrmecophyte specifically associated with the ant Allomerus decemarticulatus known to build traps on host tree twigs to ambush insect preys. The Z. annulosus females lay egg clutches protected by a sticky substance. To avoid being trapped, the first three instars of nymphs remain grouped in a clutch beneath the leaves on which they hatched, yet from time to time, they climb onto the upper side to group ambush preys. Long-distance prey detection permits these bugs to capture flying or jumping insects that alight on their leaves. Like some other Zelus species, the sticky substance of the sundew setae on their forelegs aids in prey capture. Group ambushing permits early instars to capture insects that they then share or not depending on prey size and the hunger of the successful nymphs. Fourth and fifth instars, with greater needs, rather ambush solitarily on different host tree leaves, but attract siblings to share large preys. Communal feeding permits faster prey consumption, enabling small nymphs to return sooner to the shelter of their leaves. By improving the regularity of feeding for each nymph, it likely regulates nymphal development, synchronizing molting and subsequently limiting cannibalism.
ISSN: 0028-1042

hal-01091981
https://hal.archives-ouvertes.fr/hal-01091981
https://hal.archives-ouvertes.fr/hal-01091981/document
https://hal.archives-ouvertes.fr/hal-01091981/file/Dejean_11543.pdf
DOI : 10.1007/s00114-013-1091-9

Résumé : This document presents a survey of the marine-related activities in France, i.e. those of the commercial sector (exploitation of mineral and living resources, manufacturing industries, services) and those of the public sector (Navy, State services, education, safety, marine research). A chapter is devoted to the protection of the coastal and marine environment, and the chapter on tourism gives quantitative data on the impacts of the pollution caused by the Erika oil-tanker. Each activity of the commercial sector is described by key-figures (turnover, value added, employment). The description of the non-commercial public sector includes data on costs, including personnel costs. In addition to these figures, qualitative information is given on the recent development, present situation and outlook for each activity.
Ce document présente un panorama des activités liées à Ia mer en France, c'est-a-dire du secteur industriel (exploitation des ressources minérales et vivantes, industrie manufacturière, services) et celles du secteur public non marchand (Marine nationale, services de I'Etat, enseignement, sécurité, recherche marine). Un chapitre est consacre a Ia protection de l'environnement littoral et marin, et le chapitre sur le tourisme donne des indications quantitatives sur les impacts de Ia pollution causée par le navire pétrolier Erika. Chaque activité du secteur industriel est décrite par des chiffres-clés (chiffre d'affaires, valeur ajoutée, emploi). Pour le secteur public non marchand, sont fournies des donnees sur les coûts, notamment les coûts de personnel. Ces indicateurs sont accompagnes d'informations qualitatives sur l'évolution récente, Ia situation actuelle et les perspectives de chaque activité.

Droits : 2002 Ifremer
http://archimer.ifremer.fr/doc/00117/22852/20661.pdf
http://archimer.ifremer.fr/doc/00117/22852/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Here we show that trying to rob prey (cleptobiosis) from a highly specialized predatory ant species is risky. To capture prey, Allomerus decemarticulatus workers build gallery-shaped traps on the stems of their associated myrmecophyte, Hirtella physophora. We wondered whether the frequent presence of immobilized prey on the trap attracted flying cleptoparasites. Nine social wasp species nest in the H. physophora foliage; of the six species studied, only Angiopolybia pallens rob prey from Allomerus colonies. For those H. physophora not sheltering wasps, we noted cleptobiosis by stingless bees (Trigona), social wasps (A. pallens and five Agelaia species), assassin bugs (Reduviidae), and flies. A relationship between the size of the robbers and their rate of capture by ambushing Allomerus workers was established for social wasps; small wasps were easily captured, while the largest never were. Reduviids, which are slow to extract their rostrum from prey, were always captured, while Trigona and flies often escaped. The balance sheet for the ants was positive vis-à-vis the reduviids and four out of the six social wasp species. For the latter, wasps began by cutting up parts of the prey's abdomen and were captured (or abandoned the prey) before the entire abdomen was retrieved so that the total weight of the captured wasps exceeded that of the prey abdomens. For A. pallens, we show that the number of individuals captured during attempts at cleptobiosis increases with the size of the Allomerus' prey.
ISSN: 0028-1042

hal-00825725
https://hal.archives-ouvertes.fr/hal-00825725
DOI : 10.1007/s00114-012-0895-3
PUBMED : 22361902

Éditeur(s) : HAL CCSD SAGE Publications
Résumé : International audience
ISSN: 1010-5395

hal-01679045
https://hal.univ-antilles.fr/hal-01679045
DOI : 10.1177/1010539517735414

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Climatic changes result in an increased in mean temperature and in a higher incidence of extreme weather events such as heat and cold waves. For ectotherms, such as insect parasitoids, the ability to remain active under extreme climatic conditions is a significant key to fitness. The body size of individuals, and in particular their surface to volume ratio, may play a role in their resistance to thermal conditions. The thermal tolerances are investigated of two closely-related sympatric parasitoid species [Aphidius avenae Haliday and Aphidius rhopalosiphi De Stefani-Perez (Hymenoptera: Aphidiinae)] that have a similar ecology but differ in body size and phenologies. The critical thermal limits of individuals are assessed in both sexes of each parasitoid species and the influence of surface-volume ratios on their thermal tolerances. Aphidius avenae is less resistant to low temperatures and more resistant to high temperatures than A. rhopalosiphi. The lower surface to volume ratio of A. avenae individuals may help them to remain active in summer when experiencing heat waves. However, body size is not the sole factor that plays a role in differences of thermal tolerance between species and body size may not be an adaptation to extreme temperatures but rather a by-product of developmental regulation. Closely related sympatric species from the same ecological guild can have different thermal tolerances that may allow them to occur within the same habitat. The present study also highlights the importance of clearly defining how to measure critical thermal limits to determine the thermal tolerance of a species.
ISSN: 0307-6962

hal-00589094
https://hal.archives-ouvertes.fr/hal-00589094
DOI : 10.1111/j.1365-3032.2010.00758.x

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
In mutualisms, each interacting species obtains resources from its partner that it would obtain less efficiently if alone, and so derives a net fitness benefit. In exchange for shelter (domatia) and food, mutualistic plant-ants protect their host myrmecophytes from herbivores, encroaching vines and fungal pathogens. Although selective filters enable myrmecophytes to host those ant species most favorable to their fitness, some insects can by-pass these filters, exploiting the rewards supplied whilst providing nothing in return. This is the case in French Guiana for Cecropia obtusa (Cecropiaceae) as Pseudocabima guianalis caterpillars (Lepidoptera, Pyralidae) can colonize saplings before the installation of their mutualistic Azteca ants. The caterpillars shelter in the domatia and feed on food bodies (FBs) whose production increases as a result. They delay colonization by ants by weaving a silk shield above the youngest trichilium, where the FBs are produced, blocking access to them. This probable temporal priority effect also allows female moths to lay new eggs on trees that already shelter caterpillars, and so to occupy the niche longer and exploit Cecropia resources before colonization by ants. However, once incipient ant colonies are able to develop, they prevent further colonization by the caterpillars. Although no higher herbivory rates were noted, these caterpillars are ineffective in protecting their host trees from a pathogenic fungus, Fusarium moniliforme (Deuteromycetes), that develops on the trichilium in the absence of mutualistic ants. Therefore, the Cecropia treelets can be parasitized by two often overlooked species: the caterpillars that shelter in the domatia and feed on FBs, delaying colonization by mutualistic ants, and the fungal pathogen that develops on old trichilia. The cost of greater FB production plus the presence of the pathogenic fungus likely affect tree growth.
PLoS ONE

hal-00912399
https://hal.archives-ouvertes.fr/hal-00912399
https://hal.archives-ouvertes.fr/hal-00912399/document
DOI : 10.1371/journal.pone.0020538
OATAO : 10156

Éditeur(s) : HAL CCSD Elsevier
Résumé : Differentiation of the Earth's mantle and formation of continental and oceanic crust occur principally through partial melting and extraction of basaltic melt. Among the mantle rocks occurring at the Earth's surface, as tectonically-emplaced massifs, abyssal peridotites or xenoliths, the harzburgites (< 5% clinopyroxene) are widely considered as refractory mantle residues left after extraction of a basaltic component. In contrast, the most fertile lherzolites (15% clinopyroxene) are generally regarded as pristine mantle, only weakly affected by partial melting. In this paper we present new convergent structural and geochemical data from the Lherz massif, the type-locality of lherzolite, indicating that the lherzolites from Lherz do not represent pristine mantle. Detailed structural mapping clearly shows that the lherzolites are secondary rocks formed at the expense of the harzburgites. Variations of major, minor and trace elements through the harzburgite–lherzolite contacts indicate that the lherzolites were formed through a refertilization process involving interaction of refractory, lithospheric mantle with upwelling asthenospheric partial melts. Combined with previously published indications of refertilization in orogenic peridotites, our new observations in Lherz suggest that most lherzolite massifs represent secondary (refertilized) rather than pristine mantle. Together with geochemical data on mantle xenoliths, this indicates that melt transport and melt-rock reaction play a key role on the rejuvenation and erosion of the lithospheric mantle.
ISSN: 0012-821X

hal-00406433
https://hal.archives-ouvertes.fr/hal-00406433
DOI : 10.1016/j.epsl.2007.05.026

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Most peridotite massifs and mantle xenoliths show a wide range of isotopic variations, often involving significant decoupling between Hf, Nd and Sr isotopes. These variations are generally ascribed either to mingling of individual components of contrasted isotopic compositions or to time integration of parent-element enrichment by percolating melts/fluids, superimposed onto previous depletion event(s). However, strong isotopic decoupling may also arise during porous flow as a result of daughter-elements fractionation during solid-liquid interaction. Although porous flow is recognized as an important process in mantle rocks, its effects on mantle isotopic variability have been barely investigated so far. The peridotites of the Lherz massif (French Pyrenees) display a frozen melt percolation front separating highly refractory harzburgites from refertilized lherzolites. Isotopic signatures observed at the melt percolation front show a strong decoupling of Hf from Nd and Sr isotopes that cannot be accounted for by simple mixing involving the harzburgite protolith and the percolating melt. Using one dimensional percolation-diffusion and percolation-reaction modeling, we show that these signatures represent transient isotopic compositions generated by porous flow. These signatures are governed by a few critical parameters such as daughter element concentrations in melt and peridotite, element diffusivity, and efficiency of isotopic homogenization rather than by the chromatographic effect of melt transport and the refertilization reaction. Subtle variations in these parameters may generate significant inter-isotopic decoupling and wide isotopic variations in mantle rocks. (C) 2009 Elsevier B.V. All rights reserved.
ISSN: 0012-821X

hal-00413135
https://hal.archives-ouvertes.fr/hal-00413135
DOI : 10.1016/j.epsl.2008.12.033

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : International audience
The maintenance in the long run of a positive carbon balance under very low irradiance is a prerequisite for survival of tree seedlings below the canopy or in small gaps in a tropical rainforest. To provide a quantitative basis for this assumption, experiments were carried out to determine whether construction cost (CC) and payback time for leaves and support structures, as well as leaf life span (i) differ among species and (ii) display an irradiance-elicited plasticity. Experiments were also conducted to determine whether leaf life span correlates to CC and payback time and is close to the optimal longevity derived from an optimization model. Saplings from 13 tropical tree species were grown under three levels of irradiance. Specific-CC was computed, as well as CC scaled to leaf area at the metamer level. Photosynthesis was recorded over the leaf life span. Payback time was derived from CC and a simple photosynthesis model. Specific-CC displayed only little interspecific variability and irradiance-elicited plasticity, in contrast to CC scaled to leaf area. Leaf life span ranged from 4 months to >26 months among species, and was longest in seedlings grown under lowest irradiance. It was always much longer than payback time, even under the lowest irradiance. Leaves were shed when their photosynthesis had reached very low values, in contrast to what was predicted by an optimality model. The species ranking for the different traits was stable across irradiance treatments. The two pioneer species always displayed the smallest CC, leaf life span, and payback time. All species displayed a similar large irradiance-elicited plasticity.
ISSN: 1631-0691

hal-01095975
https://hal-agroparistech.archives-ouvertes.fr/hal-01095975
DOI : 10.1016/j.crvi.2011.01.007

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
ISSN: 0098-0331

hal-01083748
https://hal-agroparistech.archives-ouvertes.fr/hal-01083748
DOI : 10.1007/s10886-009-9673-x

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Myrmecophytes offer plant-ants a nesting place in exchange for protection from their enemies, particularly defoliators. These obligate ant-plant mutualisms are common model systems for studying factors that allow horizontally transmitted mutualisms to persist since parasites of ant-myrmecophyte mutualisms exploit the rewards provided by host plants whilst providing no protection in return. In pioneer formations in French Guiana, Azteca alfari and Azteca ovaticeps are known to be mutualists of myrmecophytic Cecropia (Cecropia ants). Here, we show that Azteca andreae, whose colonies build carton nests on myrmecophytic Cecropia, is not a parasite of Azteca-Cecropia mutualisms nor is it a temporary social parasite of A. alfari; it is, however, a temporary social parasite of A. ovaticeps. Contrarily to the two mutualistic Azteca species that are only occasional predators feeding mostly on hemipteran honeydew and food bodies provided by the host trees, A. andreae workers, which also attend hemipterans, do not exploit the food bodies. Rather, they employ an effective hunting technique where the leaf margins are fringed with ambushing workers, waiting for insects to alight. As a result, the host trees' fitness is not affected as A. andreae colonies protect their foliage better than do mutualistic Azteca species resulting in greater fruit production. Yet, contrarily to mutualistic Azteca, when host tree development does not keep pace with colony growth, A. andreae workers forage on surrounding plants; the colonies can even move to a non-Cecropia tree.
ISSN: 0028-1042

hal-00818203
https://hal.archives-ouvertes.fr/hal-00818203
DOI : 10.1007/s00114-010-0710-y
PUBMED : 20730522

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
ISSN: 0006-3606

hal-01093932
https://hal-agroparistech.archives-ouvertes.fr/hal-01093932
DOI : 10.1111/j.1744-7429.2009.00614.x

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Because territoriality is energetically costly, territorial animals frequently respond less aggressively toneighbours than to strangers, a reaction known as the "dear enemy phenomenon" (DEP). The contrary,the "nasty neighbour effect" (NNE), occurs mainly for group-living species defending resource-basedterritories. We studied the relationships between supercolonies of the pest fire ant Solenopsis saevissimaand eight ant species able to live in the vicinity of its nests plus Eciton burchellii, an army ant predatorof other ants. The workers from all of the eight ant species behaved submissively when confrontedwith S. saevissima (dominant) individuals, whereas the contrary was never true. Yet, S. saevissima weresubmissive towards E. burchellii workers. Both DEP and NNE were observed for the eight ant species, withsubmissive behaviours less frequent in the case of DEP. To distinguish what is due to chemical cues fromwhat can be attributed to behaviour, we extracted cuticular compounds from all of the nine ant speciescompared and transferred them onto a number of S. saevissima workers that were then confronted withuntreated conspecifics. The cuticular compounds from three species, particularly E. burchellii, triggeredgreater aggressiveness by S. saevissima workers, while those from the other species did not.
ISSN: 0376-6357

hal-00913344
https://hal.archives-ouvertes.fr/hal-00913344
https://hal.archives-ouvertes.fr/hal-00913344/document
https://hal.archives-ouvertes.fr/hal-00913344/file/roux_10206.pdf
DOI : 10.1016/j.beproc.2013.04.014

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Mutualisms, or interactions between species that lead to net fitness benefits for each species involved, are stable and ubiquitous in nature mostly due to "byproduct benefits" stemming from the intrinsic traits of one partner that generate an indirect and positive outcome for the other. Here we verify if myrmecotrophy (where plants obtain nutrients from the refuse of their associated ants) can explain the stability of the tripartite association between the myrmecophyte Hirtella physophora, the ant Allomerus decemarticulatus and an Ascomycota fungus. The plant shelters and provides the ants with extrafloral nectar. The ants protect the plant from herbivores and integrate the fungus into the construction of a trap that they use to capture prey; they also provide the fungus and their host plant with nutrients. During a 9-month field study, we over-provisioned experimental ant colonies with insects, enhancing colony fitness (i.e., more winged females were produced). The rate of partial castration of the host plant, previously demonstrated, was not influenced by the experiment. Experimental plants showed higher δ¹⁵N values (confirming myrmecotrophy), plus enhanced vegetative growth (e.g., more leaves produced increased the possibility of lodging ants in leaf pouches) and fitness (i.e., more fruits produced and more flowers that matured into fruit). This study highlights the importance of myrmecotrophy on host plant fitness and the stability of ant-myrmecophyte mutualisms.
PLoS ONE

hal-00913754
https://hal.archives-ouvertes.fr/hal-00913754
https://hal.archives-ouvertes.fr/hal-00913754/document
DOI : 10.1371/journal.pone.0059405
OATAO : 10202

Éditeur(s) : HAL CCSD Royal Society, The
Résumé : Species engaged in multiple, simultaneous mutualisms are subject to trade-offs in their mutualistic investment if the traits involved in each interaction are overlapping, which can lead to conflicts and affect the longevity of these associations. We investigate this issue via a tripartite mutualism involving an ant plant, two competing ant species and a fungus the ants cultivate to build galleries under the stems of their host plant to capture insect prey. The use of the galleries represents an innovative prey capture strategy compared with the more typical strategy of foraging on leaves. However, because of a limited worker force in their colonies, the prey capture behaviour of the ants results in a trade-off between plant protection (i.e. the ants patrol the foliage and attack intruders including herbivores) and ambushing prey in the galleries, which has a cascading effect on the fitness of all of the partners. The quantification of partners' traits and effects showed that the two ant species differed in their mutualistic investment. Less investment in the galleries (i.e. in fungal cultivation) translated into more benefits for the plant in terms of less herbivory and higher growth rates and vice versa. However, the greater vegetative growth of the plants did not produce a positive fitness effect for the better mutualistic ant species in terms of colony size and production of sexuals nor was the mutualist compensated by the wider dispersal of its queens. As a consequence, although the better ant mutualist is the one that provides more benefits to its host plant, its lower host–plant exploitation does not give this ant species a competitive advantage. The local coexistence of the ant species is thus fleeting and should eventually lead to the exclusion of the less competitive species.
ISSN: 0962-8452

hal-01608641
https://hal.archives-ouvertes.fr/hal-01608641
DOI : 10.1098/rspb.2016.1679
PRODINRA : 405078