Riqueza, distribuição e sazonalidade de interações planta-formiga mediadas por néctar extrafloral em cerrado mineiro

• Ano de defesa: 2014
• Autor(a) principal: Belchior, Ceres
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Uberlândia; BR; Programa de Pós-graduação em Ecologia e Conservação de Recursos Naturais; Ciências Biológicas; UFU
• Palavras-chave em Português: Nectários extraflorais; Mutualismo; Comunidade de formigas; Abundância de plantas; Distribuição espacial; Brasil; Formiga - Ecologia; Relação inseto-planta; Nectários; Extrafloral nectaries; Mutualism; Ant community; Plant abundance; Spatial distribution; Brazil; CNPQ::CIENCIAS BIOLOGICAS::ECOLOGIA
• Link de acesso: https://repositorio.ufu.br/handle/123456789/13278; https://doi.org/10.14393/ufu.te.2014.67

Understanding the role and adaptive significance of extrafloral nectaries (EFNs)-mediated ant-plant associations has been the focus of many studies on plant-insect interactions. In the Brazilian cerrado savanna, plant species with EFNs are common, relatively abundant and its mutualistic relations with ants have received great attention by researchers. Species abundance is considered one of the best predictors for mutualistc networks structure, and evidences indicate that, dependending on EFNs characteristics, certain plant species might be more attractive to the ants. Considering that the location of food sources in the enrivonment can affect not only where workers forage, but also where ants construct their nests, it is expected that the presence of EFNs on vegetation, allied to seasonal variation, may determine the distribution and organization of associated ant community. Thus, ant presence on vegetation would be variable, influenced by seasonality and existence of EFN-bearing plants in space. In this PhD thesis, the following hypothesys were tested: I-i) EFN-bearing plants are more visited than EFN-lacking plants, I-ii) the presence of these glands promotes more visitation during the wet season compared to dry season, I-iii) the composition of ant visiting fauna differs between plants with and without EFNs; II-i) plant species abundance and location of EFNs afect ant visiting community, II-ii) plants with EFNs presenting the elevated morphotype are more visited compared to plants presentig other morphotypes of EFNs; III-i) vegetation spots with EFNs contain more ant nests than spots lacking EFNs, III-ii) vegetation spots with EFNs have also higher richness/abundance of ants. Data collection of all chapters have occurred in a cerrado reserve nearby Uberlândia, MG State, Brazil. Along ten transects (total area with 3.000 m2), in the rainy (October-January) and dry season (April-July) of 2010-2011, plants (72 species; 762 individuals) were checked three times per season (day, afternoon and night) for ant presence. Results showed that 21 species (29%) and 266 individuals (35%) possessed EFNs. Ant fauna censuses revealed 38 species (36 in rainy, 26 in dry season) associated to studied plants. Significant effects of interaction between seasonality, presence of EFN and plant fenological factors were detected in ant fauna, but there was no difference in the ant species composition between plants with and without EFNs. However, in the rainy season (when EFNs are more active), EFN-bearing plants presented significantly higher ant richness/abundance than EFN-lacking plants. Also, significant effects of interaction between presence of EFN and plant abundance were observed in the ant fauna registered during the rainy season. Among plants with EFNs, those very abundant were more visited than those of low abundance. The opposite was observed in the species without EFNs, which, in general, were less visited than EFN-bearing species. The location of EFNs affected ant richness, but not abundance, while the morfotype of EFNs affected both. The composition of visiting ant fauna varied only between plant species very abundant and in accordance with EFN location. Along eight transects (total area with 1.600 m2), 76 plant species, including 1.235 individuals (25% and 44% with EFNs, respectively), received baits (sardine and honey) and were observed for 15 minutes, during the day, with the purpose of registering the visiting/resident ant fauna. The censuses carried out in the rainy season (October/2011-March/2012) revealed, in total, 39 ant species and 6.502 individuals, in addition to 231 nests. EFN-bearing plants presented higher association with nests, as well as higher ant richness/abundance, than plants without EFNs. Vegetation spots lacking EFNs (N = 566) contained less nests and lower richness/abundance of visiting ants per m2 than spots containing only EFN-bearing plants (N = 362 spots) or these plants pooled with EFNs-lacking plants (N = 345 spots) each spot possesses 1 m2. The present studies are inedit, because (i) indicated that the effect of EFN presence on ant-plant interactions is conditional to seasonal variation; (ii) showed how ant community varies according to plant abundance and revealed that plants with EFNs simultaneously on vegetative and reproductive structures, or with EFNs presenting the elevated morfotype, are more attractive to ants; and (iii) showed that, in cerrado savanna, a richer ant community is promoted when EFN-bearing plants are together with EFNs-lacking plants, and also suggested that nutrition hypothesis and protection against herbivores hypothesis about the benefits of EFNs to plants may not be mutually exclusive.