Interactions among animals and plants are key to understanding seed dispersal, plant regeneration and plant community patterns. These interactions can be dynamic, with changes of species and functional roles across space and time. Despite fluctuations in species abundances and resources over time being the rule in natural communities, most studies approach plant-frugivore interactions as temporally static. We documented changes in bird and ant species in interactions with plants producing carbohydrate-(Miconia rubiginosa) or lipid-rich diaspores (Xylopia aromatica) comparing two fruiting seasons 15 years apart in a savanna in southeastern Brazil. We tested if abundance and body size of dispersal vectors (birds and ants) affected the frequency of interactions and the quantitative effectiveness of seed dispersal (QTC). Rich bird (26 species) and ant (18 genera) assemblages interacted with the diaspores. A core of bird and ant taxa was temporally consistent, and responsible for most seed removal across the two years for both plants. Temporal transience was more common for sporadic partners of interactions, and for species with similar functional roles. Abundance and body size of birds affected the interspecific contributions to QTC. Large-bodied birds dispersed large quantities of seeds of our relatively small-seeded plants, even if their visits were sporadic. For ants, variations in temperature and rainfall across time seems more important in driving variations in the contributions to QTC. The combined effect of birds and ants in the same system helps to stabilize the temporal fluctuations in the amount of seeds dispersed. However, ants alone are unlikely to replace the functional roles of vertebrate dispersers. Even though species in the assemblage change either their quantitative contribution to seed dispersal or their presence or absence in the interaction network, species persisting in interaction over time are the most important quantitative partners for plants.

RESUMO − A invasão biológica pela espécie Pittosporum undulatum Vent. pode ocasionar degradação de ecossistemas nativos, perda de espécies e de serviços ecossistêmicos. Além das características biológicas que favorecem seu estabelecimento, seus frutos são fontes alimentares para algumas espécies de aves, que acabam por dispersar suas sementes. O presente estudo foi realizado no Parque Estadual Alberto Löfgren, e visou verificar as espécies de aves potencialmente dispersoras do pau-incenso, comparar os registros de alimentação obtidos para esta árvore e para outras seis espécies arbóreas locais e avaliar a influência da ingestão das sementes pelas aves na sua taxa de germinação. A coleta de dados consistiu em observações focais das aves em atividade de forrageio no pau-incenso e a captura de indivíduos com redes de neblina para coleta de sementes nas fezes. Testes de germinação foram realizados com as sementes coletadas das fezes e diretamente dos frutos maduros. No total, foram encontradas 107 sementes nas fezes de oito sabiás, pertencentes a três espécies: Turdus rufiventris, Turdus amaurochalinus e Turdus albicollis. Não encontramos diferenças significativas nas taxas de germinação entre os tratamentos. Apesar da passagem das sementes pelo trato digestório das aves não ter alterado significativamente as taxas de germinação, os sabiás podem ser importantes dispersores do pau-incenso, permitindo a colonização de novas áreas por esta espécie exótica e intensificando seu processo de invasão biológica na Mata Atlântica.Palavras-chave: invasão biológica; dispersão; conservação; Turdus.ABSTRACT − Biological invasion by the species Pittosporum undulatum Vent. could bring degradation to native ecosystems and loss of biodiversity and ecological services. Besides the biological features favoring the establishment of the species in natural environments, some bird species use its fruits as food sources, being responsible for its seed dispersion. The present study was held at Alberto Löfgren State Park, São Paulo, Southeastern Brazil, and aimed to verify which bird species are P. undulatum potential dispersers; to compare feeding bouts to P. undulatum with another six arboreal species and to evaluate the influence of seed ingestion in germination rates. We sampled data using focal observation of foraging birds in P. undulatum and captured individuals with mist nets to collect seed from their faeces. In addition, we have made seed germination tests that included seeds collected from bird faeces and directly from mature fruits in trees. We found 107 seeds inside the faeces of eight thrushes, belonging to three species: Turdus rufiventris, Turdus amaurochalinus and Turdus albicollis. We did not find significant differences in germination rates between treatments. Although the passage through the birds' digestive system did not change significantly germination rates, thrushes can be important dispersers of P. undulatum, allowing colonization of new areas and intensifying the biological invasion process in Atlantic Forest.

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This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0), which permits reproduction, adaptation, and distribution provided the original author and source are credited. ResumoA invasão biológica é um processo frequente em ambientes naturais do mundo inteiro. Em locais invadidos, é necessária a avaliação da interferência da espécie invasora no ecossistema, antes que medidas de manejo sejam adotadas. Trechos do Parque Estadual Alberto Löfgren (PEAL), São Paulo, sudeste do Brasil, se encontram em diferentes graus de colonização por três espécies de palmeiras exóticas invasoras (PEIs). O presente estudo visou verificar como a densidade dessas PEIs influencia no uso dos habitats pelas aves de sub-bosque. Foram estabelecidas duas áreas amostrais com diferentes densidades de PEIs. Os métodos de trajetos e capturas com rede de neblina foram utilizados em conjunto para o levantamento dos dados sobre a avifauna, e o método de ponto quadrante, aliado à contagem dos indivíduos de PEIs, caracterizou a estrutura da vegetação nessas áreas amostrais. A densidade de PEIs diferiu significativamente entre as áreas. Em relação às aves, ocorreu diminuição significativa no total de contatos obtidos na área com maior densidade de PEIs. Os resultados sugerem que o aumento da densidade de PEIs interfere no uso dos habitats pelas aves, sendo necessário realizar controle das populações dessas palmeiras, para evitar perdas de espécies de aves nas assembleias locais. Palavras-chave:Arecaceae, conservação, invasões biológicas. AbstractBiological invasion is a common process in natural environments around the world. In an invaded habitat, the interference of the invasive species in the ecosystem must be evaluated. The Alberto Löfgren State Park (PEAL) in São Paulo, southeastern Brazil, is suffering colonization from three species of invasive exotic palms (IEPs). The present study intended to verify how IEP density influences understory bird assemblages in this park. We have established two sampling areas with different palm density. Both line transects and mist nets were jointly used to survey the avifauna. Point-centered quarter sampling, allied with the counting of individual IEP, characterized the vegetation structure. IEP density differed significantly among sampling areas. We encountered a negative relation between IEP density and bird contacts. The results suggest that the increase in IEPs density interfere with the habitat use by birds. The control of palm populations is required, in order to avoid losses of birds in the future.

Ghost-crab abundance is often used as an indicator of sandy beach environmental quality. Most studies use an indirect approach, assuming a direct relationship between the number of burrows and individuals. We here hypothesized that burrows could remain open for different periods of time according to the beach strata. We performed a field manipulation to simulate burrows, with persistence of each one individually assessed over a month. Results succeeded in demonstrating a significant differential persistence of burrows among beach compartments (backshore, frontal dune, and coastal vegetation, i.e., in a landward oriented sequence), which can affect abundance estimates and are thus prone to overestimating larger size classes, which inhabit the landward limit of the species’ range of occurrence. We recommend that this information is taken into consideration in population studies, and encourage the development of similar studies over broader spatial and temporal scales.