Increased Productivity and Reduced Seed Predation Favor a Large‐seeded Palm in Small Atlantic Forest Fragments

Abstract

Large-seeded plants are especially vulnerable to the loss of seed dispersers in small forest fragments. The palm Attalea humilis goes against this trend by reaching high abundances in small remnants. Productivity, seed dispersal and seed predation of A. humilis were investigated in two large (2400 and 3500 ha) and three small (19, 26 and 57 ha) Atlantic Forest fragments in southeastern Brazil. Palms in the small fragments produced more female inflorescences, resulting in a higher fruit production in these places. Seed dispersal rates were higher in the large fragments, where scatter hoarding was more frequent. Scolytine beetles were the main seed predators and damaged a larger number of seeds in small fragments, but predation by rodents and bruchine beetles was low irrespective of fragment size. As scolytines do not necessarily kill the seeds, low predation by bruchines and rodents, together with its own high productivity, allow A. humilis to be more abundant in small fragments despite the scarcity of its main dispersers. This increased abundance, by its turn, can increase competitive interactions between A. humilis and other plants in small fragments. Thus, abundance patterns of A. humilis are a good example of fragmentation affecting the balance of ecological interactions in a complex way, emphasizing the role of preserving ecological processes for conserving biodiversity in fragmented tropical landscapes.Abstract in Portuguese is available in the online version of this article.

Reproductive phenology, seed removal and early regeneration in relation to distance from parental plants of a native palm in small Atlantic forest fragments

“…Each palm produces a high number of fruits/seeds per year (2,600 seeds). There is evidence that forest palms, such as Attalea speciosa and A. humilis, invest more resources to reproduction whenever exposed to the high light conditions found in disturbed tracts of forests near edges (Barot et al 2005;Andreazzi et al 2012). High seed production may satiate seed predators enhancing the chances of per capita seed survival (Wright & Duber 2001;Andreazzi et al 2012;Meiga & Christianini 2015).…”

“…There is evidence that forest palms, such as Attalea speciosa and A. humilis, invest more resources to reproduction whenever exposed to the high light conditions found in disturbed tracts of forests near edges (Barot et al 2005;Andreazzi et al 2012). High seed production may satiate seed predators enhancing the chances of per capita seed survival (Wright & Duber 2001;Andreazzi et al 2012;Meiga & Christianini 2015). Predator satiation and high adult survival (no death in five years) may allow the longterm persistence of palm populations in disturbed Atlantic forest fragments, as suggested by detailed long-term studies working with other Atlantic forest palms (Souza & Martins 2004;Portela et al 2010).…”

“…Souza & Martins 2004;Galetti et al 2006;Portela et al 2010). Most studies investigating interactions between palms and seed predators or dispersers in fragments make inferences about the delayed consequences of these interactions for plant recruitment but do not include data on latter stages such as seedlings and juveniles (e.g., Fleury & Galetti 2006;Andreazzi et al 2012;Meiga & Christianini 2015;Mendes et al 2015). Studies that simultaneously include data on latter stages of recruitment, such as seedlings, juveniles and adults are rare but are demographically much more relevant (Wang & Smith 2002;Bruna et al 2009).…”

Effects of fragmentation on the seed predation and dispersal by rodents differ among species with different seed size

“…Some studies found that seeds were more likely to be removed and cached in large fragments than small fragments (Andreazzi et al 2012), possibly because there are more species of rodents in large fragments (Nupp & Swihart 2000;Johnson & Karels 2015), while other studies found the opposite result, and their explanation was that more rodents existed in small fragments because of increased seed production and decreased population of predators (Morán-López et al 2015;Mendes et al 2016). Some studies found that seeds were predated more frequently in fragment edges than in forest interiors, which they attributed to greater understory vegetation in fragment edges, providing harvesters increased shelter from predators (Matlack 1994;Kollmann & Buschor 2003), but other studies observed less seed removal at forest edges and proposed that this was due to lower cover at forest edges affording less protection from predators (Wolf Morán-López et al 2015).…”

“…Fragment size and edge effects are usually considered as the 2 most important fragmentation parameters for plant-rodent interactions (Kollmann & Buschor 2003;Fleury & Galetti 2006;Aliyu et al 2014;Mendes et al 2016), but previous work on these interactions in forest fragments has yielded contradictory results. For example, in 2 separate studies in eastern Brazil, Andreazzi et al (2012) showed that seeds of Attalea humilis were scatter-hoarded more frequently in the large fragments than small ones, but seed predation by rodents did not relate to fragment size, whereas Mendes et al (2016) observed greater seed predation in smaller fragments. Aliyu et al (2014) also found that seeds suffered more predation in small fragments and forest edges than in the continuous forest interior, which they attributed to greater fruit production at forest interior sites.…”