Spatial Pattern of Pindó Palm (Syagrus romanzoffiana) Recruitment in Argentinian Atlantic Forest: The Importance of Tapir and Effects of Defaunation

Abstract

Hunting pressure, fragmentation and deforestation have caused global declines in animal abundance, and the consequences for plant communities are poorly understood. Many large-seeded plants, for instance, depend on large and endangered vertebrates for seed dispersal. In some Semi-deciduous Atlantic Forests, endangered tapirs (Tapirus terrestris) are major dispersers of pind o palms (Syagrus romanzoffiana). Here, we compare recruitment patterns of pind o palms between protected and disturbed (defaunated) Atlantic Forest areas in Argentina and evaluate the potential consequences of the lack of the main disperser for pind o palm regeneration. We analyzed the number and spatial pattern of pind o adults, offspring, and tapir dung piles within ten plots established in an area spanning tapir latrines inside Iguaz u National Park and in a fragmented forest area outside the park where tapir is locally extinct. In both areas, we evaluated recruitment levels beneath 24 adult palms in circular plots centered on adult stems. We found lower pind o palm recruitment outside the park where offspring tended to be aggregated around adult palms. In contrast, in Iguaz u National Park offspring were spatially associated with tapir dung-piles, in which most offspring were registered. Recruitment under adults was higher outside the park suggesting a lower rate of seed removal in disturbed areas. Our results show that tapir dispersal promotes higher recruitment levels of pind o offspring and shapes their spatial pattern, breaking the spatial association with adult (presumably maternal) palms. These results are useful for predicting the impact of local tapir extinction on this palm.Abstract in Spanish 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

“…The loss of genetic diversity is compatible with restricted seed dispersal and increased recruitment near parental plants (Martins et al 2016). Restricted dispersal is also expected to produce increasing levels of clumped spatial distribution (Souza & Martins 2004;Sica et al 2014) potentially enhancing distance-and densitydependent effects that decrease seedling density and survival, as demonstrated here.…”

“…res.). Large-bodied frugivores such as tapirs behave as main seed dispersers of S. romanzoffiana in more pristine habitats (Sica et al 2014) but are extinct in our site. However, other animals that still persist in the region like squirrels, Crabeating fox Cerdocyon thous, Guans Penelope superciliaris, and Tegu lizards Salvator teguixin may provide some seed dispersal (Mendes et al 2015;A.V.…”

“…The seeds have on average 20.3 mm long, 11.6 mm wide and 1.1 g in weight based on N=50 seeds measured. Fruits of S. romanzoffiana are consumed by many frugivores including at least 60 species of insects and vertebrates including small rodents, squirrels, agoutis, pacas, marsupials, coatis, peccaries, tapirs, monkeys, as well as Tegu lizards and birds such as guans (Galetti et al 1992;Genini et al 2009;Silva et al 2011;Sica et al 2014;Mendes et al 2015). In contrast to frugivores few species are able to prey on the seed, which is protected by a thick endocarp.…”

The key role of the largest extant Neotropical frugivore (Tapirus terrestris) in promoting admixture of plant genotypes across the landscape

“…, Sica et al . ). Except for adults, all individuals sampled in this study (hereafter referred as ‘seedlings’ indistinctively) corresponded either to seedlings presumably younger than 1 yr old and still depending on seed resources or to saplings (early juveniles) of more than 1 yr old, with wider (but still not pinnate) leaves.…”

“…Tapirs defecate recurrently at the same sites ( i.e ., latrines), where seed and seedling clumps are usually produced (Fragoso & Huffman , Sica et al . ). In the Atlantic Forest of South America, the Amazonian tapir heavily consumes fruits of the palm Syagrus romanzoffiana (Chamisso) Glassman (Olmos et al .…”