Ants visit nectaries of Epidendrum denticulatum (Orchidaceae) in a Brazilian rainforest: effects on herbivory and pollination

Abstract

Epidendrum denticulatum (Orchidaceae) produces nectar on the petioles of buds, flowers, and fruits (extrafloral nectaries) but no nectar is found on its flowers, and it is probably a deceptive species. In the Brazilian Atlantic rainforest, some aspects of both the ecology and behavior of Camponotus sericeiventris (Formicinae) and Ectatomma tuberculatum (Ponerinae), two ant species foraging on E. denticulatum extrafloral nectaries, were investigated. Both experiments, using termites as baits and field observations, suggest that these ant species are able to prevent reproductive organ herbivory, without affecting pollinator behaviour. Since a low fruit set is often cited as a characteristic of the family, especially for deceptive species, ants attracted to orchid inflorescences protect reproductive structures and increase the probability of pollination success. Epidendrum denticulatum flowers were visited and probably pollinated by Heliconius erato (Nymphalidae) and Euphyes leptosema (Hesperiidae).Key words: ant-plant interaction, foraging behaviour, extrafloral nectaries, pollination ecology. RESUMO Formigas visitam nectáreos de Epidendrum denticulatum (Orchidaceae) em uma área deMata Atlântica: efeitos sobre herbivoria e polinização Epidendrum denticulatum (Orchidaceae) produz néctar nos pecíolos de botões florais, flores e frutos (nectáreos extraflorais), mas não em suas flores, e provavelmente "engana" seus polinizadores. Numa área de Mata Atlântica, investigamos alguns aspectos da ecologia e comportamento das formigas Camponotus sericeiventris (Formicinae) e Ectatomma tuberculatum (Ponerinae), ambas encontradas forrageando em nectáreos extraflorais de E. denticulatum. Tanto experimentos usando cupins como iscas quanto observações de campo sugerem que ambas as espécies de formiga têm a dupla capacidade de limitar a herbivoria dos órgãos reprodutivos da espécie estudada, sem interferir no comportamento dos polinizadores. Uma vez que baixa taxa de frutificação é característica das orquídeas, principalmente de espécies sem néctar floral, as formigas atraídas para suas inflorescências estão protegendo as estruturas reprodutivas e aumentando a probabilidade de sucesso de polinização. As flores de E. denticulatum são visitadas e provavelmente polinizadas por Heliconius erato (Nymphalidae) e Euphyes leptosema (Hesperiidae).Palavras-chave: interação planta-formiga, comportamento de forrageamento, nectáreos extraflorais, ecologia de polinização.

Unidirectional transitions in nectar gain and loss suggest food deception is a stable evolutionary strategy in Epidendrum (Orchidaceae): insights from anatomical and molecular evidence

“…In Epidendrum , nectar has been detected only in species showing swollen cuniculi, in which the presence of copious nectar is evident [9]. Thus, rewarding and rewardless Epidendrum species are distinguishable only through observing free nectar availability in floral nectaries [11, 12]. …”

“…Indirect evidence gathered from different data sources has been interpreted as collective evidence indicating the presence of a food deceptive strategy. The short visit times of pollinators that abandon the inflorescence after visiting a single flower [11], low fruit set [12], and the absence of nuclear genetic structure among populations [9] may indicate the existence of food deception in the analyzed species. According to [2], food deception in orchids tends to reduce the time spent by pollinators in the same inflorescence, decreasing the levels of geitonogamy and fruit set.…”

Crane flies and microlepidoptera also function as pollinators in Epidendrum (Orchidaceae: Laeliinae): the reproductive biology of E. avicula

“…The majority of the species of Epidendrum , however, is adapted to pollination by Lepidoptera (i.e. phalaenophily and psychophily; van der Pijl & Dodson ; Almeida & Figueiredo ; Pansarin ; Pansarin & Amaral ; Fuhro et al . ).…”

Pollination of Guarianthe skinneri, an ornamental food deception orchid in southern Florida, by the naturalized orchid bee Euglossa viridissima

“…Extrafloral nectaries commonly occur in orchid inflorescences but are little studied. Almeida and Figueiredo (2003) concluded that a Camponotus ant species protects the reproductive structures of Epidendron denticulatum (Jacq.) in Brazil.…”