Caterpillars and fungal pathogens: two co-occurring parasites of an ant-plant mutualism

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

Divergent Chemical Cues Elicit Seed Collecting by Ants in an Obligate Multi-Species Mutualism in Lowland Amazonia

In lowland Amazonian rainforests, specific ants collect seeds of several plant species and cultivate them in arboreal carton nests, forming species-specific symbioses called ant-gardens (AGs). In this obligate mutualism, ants depend on the plants for nest stability and the plants depend on ant nests for substrate and nutrients. AG ants and plants are abundant, dominant members of lowland Amazonian ecosystems, but the cues ants use to recognize the seeds are poorly understood. To address the chemical basis of the ant-seed interaction, we surveyed seed chemistry in nine AG species and eight non-AG congeners. We detected seven phenolic and terpenoid volatiles common to seeds of all or most of the AG species, but a blend of the shared compounds was not attractive to the AG ant Camponotus femoratus. We also analyzed seeds of three AG species (Anthurium gracile, Codonanthe uleana, and Peperomia macrostachya) using behavior-guided fractionation. At least one chromatographic fraction of each seed extract elicited retrieval behavior in C. femoratus, but the active fractions of the three plant species differed in polarity and chemical composition, indicating that shared compounds alone did not explain seed-carrying behavior. We suggest that the various AG seed species must elicit seed-carrying with different chemical cues

Anatomical aspects of the embryo and initial development of Oenocarpus minor Mart: a palm tree from the Amazon

The anatomy of the embryo and the initial germination phase of O. minor seeds are examined here. Ripe fruits were collected from five individuals, the pulp removed, and the seeds sown in beds with sandy substrate in a greenhouse with 50% shade. Germination follow-up was made by collecting different stages of development. The anatomical study done according to usual techniques of light microscopy. The embryo is capitate and occupies a central position in the basal region of the seed. The embryogenic axis is located in the proximal region in a position that is oblique to the cotyledon axis. The cotyledon is formed by parenchymatous, procambial and protodermic tissue. The vascular bundles lie along the peripheral zone of the distal region to the embryogenicaxis. After 14 days, the primary rootemerges; after 21 days, the first cotyledon sheath and after 35 days, the second cotyledon sheath, and the seedling emerges above the substrate. Germination is of the ligule adjacent type.Neste trabalho foi feita a anatomia do embrião e a fase inicial da germinação da semente de O. minor. Frutos maduros de cinco indivíduos foram despolpados e as sementes obtidas foram semeadas em canteiros contendo substrato areia em casa de vegetação com sombreamento a 50%. O acompanhamento da germinação foi feito através de coletas das diferentes fases do desenvolvimento. O estudo anatômico foi realizado conforme técnicas usuais de microscopia de luz. O embrião é capitado. O eixo embrionário localiza-se na região proximal em posição oblíqua ao eixo cotiledonar. O cotilédone é formado por tecido parenquimático, procambial e protodérmico. Os feixes vasculares ocorrem ao longo da zona periférica da região distal até ao eixo embrionário. Aos 14 dias é emitida a raiz primária. Aos 21 dias forma-se a primeira bainha cotiledonar e aos 35 dias a segunda bainha cotiledonar ocorrendo à emergência da plântula acima do substrato. A germinação é do tipo adjacente ligular

Ecology and evolution of ant gardens in French Guiana

Les jardins de fourmis résultent de l'association entre un nombre limité d'épiphytes et une, deux ou trois espèces de fourmis qui vivent autour des racines et forment leur nid à ce niveau sans altérer la structure racinaire ni l'arbre support. Ce type d'association présente à la fois des avantages pour la plante et pour les fourmis. Les fourmis se nourrissent des fruits des épiphytes et contribuent à disséminer leurs graines et de plus, créent, par la constitution de leur nid, un sol suspendu plus riche en nutriments que le sol réel, permettant une bonne croissance et une protection contre la sécheress

Aspectos morfo-anatômicos do embrião de Euterpe precatoria Mart. durante o processo germinativo Morphological and anatomical studies on germinating seeds of Euterpe precatoria Mart.

Euterpe precatoria Mart. é uma palmeira amplamente distribuída na bacia Amazônica, em terra firme e em solos de várzea. Dos frutos obtém-se o "vinho do açaí" e do ápice caulinar o palmito, que fazem desta palmeira um importante recurso alimentar. Foi feita a descrição morfo-anatômica do embrião de Euterpe precatoria, durante o processo germinativo, possibilitando o entendimento do mesmo. As observações foram realizadas em microscopio óptico, a partir de cortes histológicos de secções longitudinais e transversais da semente em diversos estádios da germinação. O eixo embrionário é curvo. No início da germinação, forma-se externamente o botão cotiledonar contendo a futura planta. A radícula emerge primeiro, apresentando coifa bem desenvolvida, desenvolvendo-se mais rapidamente que a plúmula. O processo de formação das primeiras folhas é contínuo. À medida que o embrião se desenvolve, a região distal aumenta de tamanho, formando o haustório e ocupando o lugar do endosperma.<br>Euterpe precatoria is a palm tree widespread in Amazon basin, in terra firme and várzea sites. The fruit is used for the production of Açaí wine, and the sten apex for the production of palm hearts (palmito), which are an important food source. Different stages of germinated açaí seed were studied in longitudinal and transversal sections, under a optical microscope. The embryonic axis is curved. In the early stages of germination, the integument is displaced, forming the cotyledonal bud and the future plant. The radicle emerges first, with a well developed root cap and develops faster than the plumula. The process of formation of the first leaves is continuous. As the embryo is developing, the distal region increases in size, forming the haustorium and occupying the place of the endosperm