Seed survival and dispersal of an endemic Atlantic forest palm: the combined effects of defaunation and forest fragmentation

Abstract

About 45 palm species occur in the Atlantic forest of Brazil, and most of them are affected by loss of seed dispersers resulting from forest fragmentation and hunting. Here we report the effects of habitat loss and defaunation on the seed dispersal system of an endemic palm, Astrocaryum aculeatissimum . We evaluated seed removal, insect and rodent seed predation, and scatter-hoarding in nine sites, ranging from 19 ha to 79 000 ha. We report the seedling, juvenile and adult palm densities in this range of sites. Endocarps remaining beneath the parent palm had a higher probability of being preyed upon by insects in small, mostly fragmented and more defaunated sites. The frequency of successful seed removal, scatter-hoarding and consumption by rodents increased in the larger, less defaunated sites. Successful removal and dispersal collapsed in small ( < 1000 ha), highly defaunated sites and frequently resulted in low densities of both seedlings and juveniles. Our results indicate that a large fraction of Atlantic forest palms that rely on scatter-hoarding rodents may become regionally extinct due to forest fragmentation and defaunation. Current management practices including palm extraction and hunting pressure have a lasting effect on Atlantic forest palm regeneration by severely limiting successful recruitment of prereproductive individuals.

Estudo fenológico de Bactris gasipaes Kunth,Euterpe edulis Mart. e Syagrus romanzoffiana (Cham.) Glassman no Vale do Ribeira, SP, Brasil

“…As palmeiras são frequentemente consideradas "espécies chave" por possuírem pouca sincronia e longos períodos de frutificação, o que torna seus frutos disponíveis em épocas de escassez geral de frutos, sendo importante recurso alimentício para frugívoros tropicais (Galetti et al 1992, Galetti & Aleixo 1998, Henderson et al 2000, Galetti et al 2006.…”

Medium and large-sized mammals of the Reserva Ecológica de Guapiaçú, Cachoeiras de Macacu, RJ

“…Dirzo & Miranda 1990, Keuroghlian & Eaton 2009, Beck et al 2013, and also through their role as seed dispersers and predators (e.g. Asquith et al 1997, Asquith et al 1999, Galetti et al 2006, Donatti et al 2009, Kuprewicz 2013 contributing to plant local diversity. Acting as animal predators they also regulate herbivore populations (e.g.…”

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

“…However, invertebrate seed predators may not be able to compensate the mortality of higher numbers of seeds in fragments, allowing unexpected increases in recruitment near parental plants (Wright & Duber 2001;Wright 2003;Terborgh 2013). Although the effects of habitat loss and fragmentation on species composition and community structure of plants are reasonably well know (Tabarelli et al 2010;Laurance et al 2011), the effects upon interactions with seed predators and dispersers (e.g., Mendes et al 2015) and the way they could cascade and influence plant recruitment is much less understood (e.g., Galetti et al 2006;Uriarte et al 2010).…”

“…However, little is known about recruitment and long-term persistence of these palms in small Atlantic Forest fragments (e.g. 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).…”

“…Habitat loss, fragmentation and hunting interact synergistically contributing to decrease the abundance of many vertebrate frugivores and seed dispersers, with large animals being more susceptible to local extinctions (Peres & Palacios 2007). Plants with large seeds (>15 mm) are more susceptible to the loss of dispersers because their regeneration is strongly seed-limited (Moles & Reproductive phenology, seed removal and early regeneration in relation to distance from parental plants of a native palm in small Atlantic forest fragments Westoby 2002) and these plants rely heavily on large-bodied animals as seed dispersers (Silva & Tabarelli 2000;Wright & Duber 2001;Cordeiro & Howe 2003;Galetti et al 2006;2013;Terborgh et al 2008). For instance, defaunation of large-gaped frugivorous birds has been pointed out as the main source of rapid evolutionary change in seed size of the palm Euterpe edulis in remnants of the Brazilian Atlantic forest (Galetti et al 2013).…”