ABSTRACT Many pre-dispersal seed predators are specialized insects that rely on seeds for larval development. These insects may respond to the amount of seeds produced by a plant (i.e. crop size), increasing the proportion of seeds damaged with increases in seed numbers. Large seeds have more resources and spend more time in plants to complete their development and are probably more prone to be preyed on by those insects than small seeds. Here I tested how crop size and seed mass influence pre-dispersal seed predation in plants from the Cerrado savannas of Brazil. I related plant crop size to pre-dispersal seed predation for Xylopia aromatica and Erythroxylum pelleterianum. A literature review was performed to test if seed mass may explain among-species differences in pre-dispersal seed predation. Pre-dispersal losses increased proportionally to crop size in the two species investigated, but some species show positive or no density-dependent seed predation in literature, indicating that seed losses are not a simple function of crop sizes. Seed mass did not explain pre-dispersal seed loss differences among 14 species with data available. Pre-dispersal losses are often small and probably less important than seed dispersal and establishment limitation for plant recruitment in Cerrado savannas.

ABSTRACT The Brazilian Atlantic Forest is a global biodiversity hotspot, but most of what remains are small fragments. Small fragments are often harsh environments for forest plant recruitment due to edge effects and the loss of frugivorous animals that provide seed dispersal. We recorded the one-year reproductive phenology of the keystone palm Syagrus romanzoffiana in small (<2.5ha) Atlantic Forest fragments in southeastern Brazil. We tested the Janzen-Connell hypothesis with seed-removal experiments and followed the five-year survival of recruits in relation to the distance from parental plants. Palms produced many fruits throughout the year (mean 2,600/plant). More seedlings were found away from parental plants than near them, thereby supporting the Janzen-Connell hypothesis. Almost 45% of seedlings alive in 2010 were dead five years later, but recruitment of new seedlings compensated for this mortality. Distance-dependent factors influenced the density of early ontogenetic stages, but had limited effects on juveniles or on seed removal. High seed production, seed dispersal provided by disturbance-tolerant frugivores and the relatively long-term survival of adults, seedlings and juveniles seem to allow the persistence of S. romanzoffiana in the forest fragments, but possibly at the cost of an increased clumped distribution and reduced gene flow at the landscape scale.

Mistletoe establishment relies heavily on a seed reaching a proper host plant. Small frugivorous birds usually disperse large numbers of mistletoe seeds. However, in the field, mistletoes are absent from some potential available hosts. We investigated whether the mistletoe Phoradendron crassifolium has some preferences for specific host trees in a fragment of Atlantic Forest in southeast Brazil. We surveyed 397 tree individuals of 50 species within 25 families. Seven of those species (14%) bore P. crassifolium infections. Although prevalence at the individual level was low (11.6%), there were marked deviations in infection levels among species and families. Most (87%) of the infections (40 of 46) occurred in species belonging to the families Anacardiaceae (Lithraea molleoides and Tapirira guianensis) and Siparunaceae (Siparuna guianensis), which nevertheless accounted for only 26% of the potential individual hosts (103 of 397). We also performed an experiment simulating bird behavior. We inoculated 480 mistletoe seeds to the bark of four potential hosts in field, following the fate of the seeds for five months. No differences in host preference were observed. The low specificity detected at the local level was confirmed by a survey of exsiccata collected over the geographical distribution of the mistletoe, suggesting that P. crassifolium prevalence is more dependent on dispersal limitation than on mistletoe-host compatibility.

Conhecer a biologia de espécies invasoras pode auxiliar na escolha de estratégias de manejo visando seu controle. Este estudo enfoca a fenologia, produção e dispersão de sementes de Archontophoenix cunninghamiana, uma palmeira nativa da Austrália que está invadindo fragmentos de Mata Atlântica. O estudo foi desenvolvido num fragmento florestal de 10 ha (Mata da Cuaso 23º34' S, 46º43' W). Archontophoenix produziu frutos ao longo do ano, apresentando frutos maduros principalmente de outubro a fevereiro. As árvores atingem a maturidade com 18,5 cm DAP, cada uma produzindo 4.119 ± 1.922 sementes ano-1. Aves dispersam as sementes de Archontophoenix e 15% das sementes sobrevivem a predação pós-dispersão até o tempo requerido para germinação. O padrão espacial de predação pós-dispersão e a ausência de predadores de sementes pré-dispersão sugerem a ausência de predadores de sementes de Archontophoenix especializados, conforme predito pela hipótese de liberação de inimigos naturais. Dados deste e de outros estudos indicam um aumento expressivo na produção de sementes de A. cunninghamiana no fragmento em poucos anos. Archontophoenix pode estar se beneficiando da ausência de Euterpe edulis Mart., uma palmeira nativa que possui biologia similar e que foi extinta localmente devido à ação humana. Recomendações para controlar a invasão incluem a remoção contínua de todos Archontophoenix maiores que 15 cm DAP no fragmento e o estabelecimento de uma zona tampão ao redor do fragmento livre de Archontophoenix para dificultar a chegada de propágulos.

Understanding the basic biology of invasive species can help us to choose the best management strategies to deal with the invasion. I report the phenology, seed production and dispersal of Archontophoenix cunninghamiana, an Australian palm that is invading Atlantic forest fragments. Field work was done in a 10 ha forest fragment (Mata da Cuaso 23º34' S, 46º43' W). Archontophoenix produced bunches of fruits all year round, with a peak of mature fruits from October to February. Trees reach maturity around 18.5 cm DBH, each producing 4,119 ± 1,922 seeds year-1. Birds disperse the seeds, and nearly 15% of them escape post-dispersal seed predation during the time interval needed for germination. The spatial pattern of post-dispersal predation and the absence of pre-dispersal seed predation suggest a lack of specialized seed predators of Archontophoenix, as predicted by the enemy release hypothesis. Data obtained from this and other studies pointed out to a massive increase in seed production of A. cunninghamiana in a few years within the fragment. I suggest that this invasive palm can be taking advantage of the absence of Euterpe edulis Mart., a native palm which has similar biology, and was locally extinct due to human disturbances. Recommendations to control the invasion include the continuous removal of all Archontophoenix larger than 15 cm DBH, and the establishment of a buffer zone free of Archontophoenix around the fragment to decrease propagule pressure.