Abstract
Plants bearing extrafloral nectaries (EFNs) are common in the Brazilian cerrado savanna, where climatic conditions having marked seasonality influence arboreal ant fauna organization. These ant-plant interactions have rarely been studied at community level. Here, we tested whether: 1) EFN-bearing plants are more visited by ants than EFN-lacking plants; 2) ant visitation is higher in the rainy season than in dry season; 3) plants producing young leaves are more visited than those lacking young leaves in the rainy season; 4) during the dry season, plants with old leaves and flowers are more visited than plants with young leaves and bare of leaves or flowers; 5) the composition of visiting ant fauna differs between plants with and without EFNs. Field work was done in a cerrado reserve near Uberlândia, MG State, Brazil, along ten transects (total area 3,000 m2), in the rainy (October-January) and dry seasons (April-July) of 2010–2011. Plants (72 species; 762 individuals) were checked three times per season for ant presence. Results showed that 21 species (29%) and 266 individuals (35%) possessed EFNs. These plants attracted 38 ant species (36 in rainy, 26 in dry season). In the rainy season, plants with EFNs had higher ant abundance/richness than plants without EFNs, but in the dry season, EFN presence did not influence ant visitation. Plant phenology affected ant richness and abundance in different ways: plants with young leaves possessed higher ant richness in the rainy season, but in the dry season ant abundance was higher on plants possessing old leaves or flowers. The species composition of plant-associated ant communities, however, did not differ between plants with and without EFNs in either season. These findings suggest that the effect of EFN presence on a community of plant-visiting ants is context dependent, being conditioned to seasonal variation.
Highlights
Interspecific interactions are considered important processes that can influence species variation and adaptation [1] as well as community organization and stability [2,3,4]
Young leaves were observed in 51.2% (= 390), old leaves in 77.2% (= 588) and flowers in 11% (= 84) of all plants
Young leaves were observed in 9.1% (= 69), old leaves in 94.3% (= 719) and flowers in 3.9% (= 30) of all plants
Summary
Interspecific interactions are considered important processes that can influence species variation and adaptation [1] as well as community organization and stability [2,3,4]. Ants can use extrafloral nectaries (EFNs), which are glands that secrete nectar rich in sugar, water and amino acids. These glands are very diverse in morphology, possessing structures that can differ considerably from floral nectaries in size and shape [14,15]. In Brazil, records of EFNs on the flora of many biomes are frequent [5, 8, 16], especially in the cerrado savanna, where the frequency and abundance of plants with EFNs are relatively high [5, 6, 17]. Ants are the main visitors of EFNs, among other arthropods, like wasps, flies, spiders, bees, beetles and mites [18,19,20]
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