Local extinctions have cascading effects on ecosystem functions, yet little is known about the potential for the rapid evolutionary change of species in human-modified scenarios. We show that the functional extinction of large-gape seed dispersers in the Brazilian Atlantic forest is associated with the consistent reduction of the seed size of a keystone palm species. Among 22 palm populations, areas deprived of large avian frugivores for several decades present smaller seeds than nondefaunated forests, with negative consequences for palm regeneration. Coalescence and phenotypic selection models indicate that seed size reduction most likely occurred within the past 100 years, associated with human-driven fragmentation. The fast-paced defaunation of large vertebrates is most likely causing unprecedented changes in the evolutionary trajectories and community composition of tropical forests.

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Ecology of neotropical mistletoes: an important canopy-dwelling component of Brazilian ecosystems RESUMO (Ecologia de ervas-de-passarinho Neotropicais: um importante componente do dossel de ecossistemas brasileiros). Ervas-de-passarinho têm sim sido regularmente estudadas em países temperados por afetar negativamente espécies cultivadas e fl orestas manejadas. Em comparação com ambientes temperados pouco se conhece sobre a ecologia das ervas-de-passarinho neotropicais. Desta forma, é necessário maior conhecimento sobre o grupo porque são importantes elementos de comunidades vegetais, atuando como recurso-chave para polinizadores, dispersores de sementes e herbívoros. Através de uma combinação de trabalhos clássicos já publicados com evidências empíricas recentes, nós apresentamos padrões emergentes da interação entre ervas-de-passarinho com os organismos associados e questionamentos para estudos adicionais. Existe um crescente interesse neste grupo no Brasil. E embora existam informações sobre dispersão de sementes, estudos sobre biologia reprodutiva são raros e representam um campo a ser explorado. O conhecimento da biologia básica das ervas-de-passarinho será relevante para modelar sua distribuição espacial usando uma abordagem metapopulacional ou epidemiológica. Nesta revisão nós sumarizamos os principais estudos conduzidos na região Neotropical para fornecer um panorama atual das pesquisas desenvolvidas, bem como novas ideias para futuras investigações, especialmente no Brasil. Palavras ABSTRACT(Ecology of neotropical mistletoes: an important canopy-dwelling component of Brazilian ecosystems). Mistletoes have been studied in temperate countries regularly because they can be pests of cultivated plants and forest plantations. In comparison with temperate habitats, little is known about the ecology of mistletoes in the Neotropics. More emphasis should be given to neotropical mistletoes because they could be important elements of plant communities, acting as key resources for pollinators, seed dispersers and herbivores. Using a combination of fi ndings from early mistletoe studies and empirical evidence from several recent case studies, we report emerging patterns of mistletoe interactions with associated organisms and propose aims for further studies. Th ere has been increasing interest in working with mistletoes in Brazil. Although there are some data on the ecology of mistletoe seed dispersal, reproductive biology studies are scarce and represent a wide range of fi eldwork to be explored. Knowledge of the basic biology of mistletoes will be very important for modeling their spatial distribution using metapopulation or epidemiological approaches. In this review, we summarize the studies conducted in the neotropical region in order to provide a framework for current research and new ideas for future investigations of mistletoes, especially in Brazil. Revisão / ReviewActa bot. bras. 26(2): 264-274. 2012.Ecology of neotropical mistletoes: an important canopy-dwelling component of Brazilian ecosystems

Non-overlap of hosts used by three congeneric and sympatric loranthaceous mistletoe species in an Amazonian savanna: host generalization to extreme specialization RESUMO (Não-sobreposição de hospedeiros utilizados por três espécies de ervas-de-passarinho lorantáceas congêneres e simpátricas em uma savana Amazônica: generalização pelo hospedeiro à extrema especialização). Duas hipóteses principais predominam na literatura sobre a especifi cidade entre ervas-de-passarinho e hospedeiros: (1) ervas-de-passarinho só poderão se especializar em espécies de plantas em que elas são frequentemente depositadas; e (2) compatibilidade entre as ervas-depassarinho e as espécies de plantas é um prerequisito para o parasitismo. Explorei estas hipóteses com o estudo dos padrões de deposição de sementes e a compatibilidade entre ervas-de-passarinho e hospedeiros em populações de três espécies de ervas-de-passarinho congenéricas e simpátricas do gênero Psittacanthus (P. biternatus, P. eucalyptifolius and P. plagiophyllus -Loranthaceae) e registrei a presença ou ausência destas três espécies em 15 espécies de árvores em uma mancha de savana na Amazônia. Entre as cinco espécies de árvores que eu encontrei infectadas, também registrei se elas possuíam pelo menos uma semente de erva-de-passarinho de qualquer das espécies aderida aos seus galhos. Finalmente, plantei sementes de todas as espécies de ervas-de-passarinho nas mesmas árvores em várias espécies de hospedeiros e não-hospedeiros e registrei a sobrevivência das sementes e o estabelecimento ao fi nal de 7 (P. plagiophyllus) e 12 meses (P. biternatus e P. eucalyptifolius). Não houve sobreposição entre as árvores utilizadas como hospedeiros pelas três espécies de Psittacanthus. ABSTRACT(Non-overlap of hosts used by three congeneric and sympatric loranthaceous mistletoe species in an Amazonian savanna: host generalization to extreme specialization). Two main hypotheses predominate in the literature on mistletoe-host specifi city: (1) mistletoes are only likely to specialize on plant species on which they are frequently deposited; and (2) compatibility between mistletoes and plant species is a prerequisite for mistletoe-host parasitism. I explored these hypotheses by studying the seed deposition patterns and mistletoe-host compatibility in populations of three congeneric and sympatric mistletoe species of the genus Psittacanthus (P. biternatus, P. eucalyptifolius and P. plagiophyllus -Loranthaceae). I recorded the presence or absence of these mistletoe species in 15 tree species in a savanna patch in Amazonia. Among the fi ve tree species that I found to be potential hosts (at least one tree individual infected), I also recorded if they had at least one mistletoe seed of any species attached to their branches. Finally, I planted seeds of all mistletoe species on the same individual trees in various hosts and non-host species and recorded seed survivorship and seedling establishment within 7 (P. plagiophyllus) to 12 months (P. biternatus and P. eucalyptifolius) aft er planting. Th er...

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Most mistletoe species that live in savanna patches are subjected to frequent fires. Although having similar habits, even congener species may parasitize very different host species and show different degrees of specialization that may differentially affect their resistance to fire. We studied three congener mistletoe species with a diverse degree of specificity to their hosts: Psittacanthus biternatus, Psittacanthus eucalyptifolius and Psittacanthus plagiophyllus, the first being the most generalist species, and the last the most specialist. We investigated their prevalence (proportion of hosts infected) in 35 plots of an Amazonian savanna, with different fire histories. Our aim was to understand if they respond similarly to fire frequency and the abundance of their hosts. Additionally, we experimentally applied fire to individuals of the three species using a portable propane flamethrower to test for the influence of mistletoe species, plant size and quantity of heat pulses (single or double burn) on mistletoe survivorship. Prevalence varied greatly among species: 1.5 percent for P. biternatus, 4.8 percent for P. eucalyptifolius and 20 percent for P. plagiophyllus. Prevalence of P. plagiophyllus was negatively related to fire frequency, while for the other two species it was not. Psittacanthus biternatus had a higher probability of survival compared with the other two species, and larger plants were more likely to survive under single burn treatment and to regenerate through sprouting. Our results suggest that, due to complex interactions between fire, hosts and mistletoes, even sympatric species may respond differently to fire frequency and host abundance.Abstract in Portuguese is available in the online version of this article.

Our knowledge of how tropical forest biodiversity and functioning respond to anthropogenic and climate‐associated stressors is limited. Research exploring El Niño impacts are scarce or based on single post‐disturbance assessments, and few studies assess forests previously affected by anthropogenic disturbance. Focusing on dung beetles and associated ecological functions, we assessed (a) the ecological effects of a strong El Niño, (b) if post‐El Niño beetle responses were influenced by previous forest disturbance, and (c) how these responses compare between forests impacted only by drought and those affected by both drought and fires. We sampled 30 Amazonian forest plots distributed across a gradient of human disturbance in 2010, 2016, and 2017—approximately 5 years before, and 3–6 and 15–18 months after the 2015–16 El Niño. We found 14,451 beetles from 98 species and quantified the beetle‐mediated dispersal of >8,600 seed mimics and the removal of c. 30 kg of dung. All dung beetle responses (species richness, abundance, biomass, compositional similarity to pre‐El Niño condition, and rates of dung removal and seed dispersal) declined after the 2015–16 El Niño, but the greatest immediate losses (i.e., in 2016) were observed within fire‐affected forests. Previous forest disturbance also influenced post‐El Niño dung beetle species richness, abundance, and species composition. We demonstrate that dung beetles and their ecological functions are negatively affected by climate‐associated disturbances in human‐modified Amazonian forests and suggest that the interaction between local anthropogenic and climate‐related stressors merits further investigation. Abstract in Portuguese is available with online material.

The present paper describes the spatial distribution of the mistletoe Psittacanthus plagiophyllus Eichl. (Loranthaceae) on its host, the cashew tree Anacardium occidentale L., in a Brazilian Amazonian savanna. Our aim was to understand the roles of bird-seed dispersers and host quality in determining the mistletoe distribution among its host trees. In 2006, we marked 118 cashews in a 4.5-ha plot and counted the number of mistletoes and the presence of seeds attached to host branches in 2006, 2007 and 2008. On average, 36% of the hosts were infected each year. The infection load and the probability of being infected increased significantly with host crown diameter. On average, 25% of the hosts received at least one mistletoe seed in each year, being taller and previously infected hosts more prone to receive seeds in all 3 years. Elaenia cristata was the main seed disperser, visiting P. plagiophyllus 48 times in 35 h of focal records. Additionally, in a field experiment, we used the presence of an infection and the host size as surrogates for host quality and tested their effect on mistletoe survivorship. After 9 months, 16.5% of seeds survived and 14% had established, but neither host conditions nor host size influenced seed survivorship. Therefore, we suggest that mistletoe distribution is a consequence of a consistent dispersal of seeds onto larger and previously parasitised hosts across years.