Potential Effects of Ateline Extinction and Forest Fragmentation on Plant Diversity and Composition in the Western Orinoco Basin, Colombia

Abstract

Cattle and agricultural farming in the western Orinoco Basin began in 1555, and since then fragmentation of continuous forest has occurred. We evaluated the effects of the disturbances and the absence of large primates on plant community composition, diversity, and regeneration patterns. Atelines (Lagothrix and Ateles) inhabited the lowlands close to the Andean mountains, but no longer live in fragmented habitats. Their absence may have negative effects on plant populations because atelines play important roles as seed dispersers in neotropical forests, especially for large-seeded plants, which are rarely swallowed by other seed dispersers. We compared 2 1-ha vegetation plots in forest fragments north of the La Macarena Mountains with 7 plots in continuous forest in Tinigua National Park. Both sites share the same climatic conditions and have similar geological origins. There is floristic affinity between forests with similar ecological characteristics; the fragmented forests are also less diverse than the continuous forests. As predicted, the forest fragments have fewer individuals with large seeds. The results suggest that forest fragmentation and local ateline extinctions affect plant communities, reducing diversity and affecting large-seeded plants.

Hunting alters seedling functional trait composition in a Neotropical forest

“…We believe this reflects the compensatory effects of missing granivores. The loss of large frugivores is generally thought to disfavor large-seeded plant species (Nunez-Iturri et al 2008, Stevenson and Aldana 2008, Terborgh et al 2008. The impact of the loss of large frugivores for plant community composition might be even larger than is generally appreciated because comparisons of hunted and protected forests can only document the net effect of missing frugivores and granivores.…”

“…The loss of these species has been linked to substantial declines in plant species diversity (e.g., Miranda 1991, Stevenson andAldana 2008), though this is not always observed (Rolda´n andSimonetti 2001, Wright et al 2007b). Changes in plant diversity and species composition in defaunated forests might be driven by lost seed dispersers (Dirzo and Miranda 1991, Wright et al 2007b, Nunez-Iturri et al 2008, Stevenson and Aldana 2008, Terborgh et al 2008, Harrison et al 2013, seed predators (Wright et al 2007b), or herbivores Miranda 1991, Poulsen et al 2013).…”

“…The loss of these species has been linked to substantial declines in plant species diversity (e.g., Miranda 1991, Stevenson andAldana 2008), though this is not always observed (Rolda´n andSimonetti 2001, Wright et al 2007b). Changes in plant diversity and species composition in defaunated forests might be driven by lost seed dispersers (Dirzo and Miranda 1991, Wright et al 2007b, Nunez-Iturri et al 2008, Stevenson and Aldana 2008, Terborgh et al 2008, Harrison et al 2013, seed predators (Wright et al 2007b), or herbivores Miranda 1991, Poulsen et al 2013). However, because hunting impacts species from all of these guilds simultaneously, including primates, birds, ungulates, and large rodents (Corlett 2007, Peres and Palacios 2007, Fa and Brown 2009, these comparative studies of hunted vs. protected forests cannot identify the specific interactions or mechanisms underlying changes in plant diversity and species composition.…”

“…The net effect of the loss of both dispersers and seed predators varies among studies that compare hunted and protected forests. For example, species with large seeds are more abundant in hunted forests in Panama (Wright et al 2007b), but less abundant in hunted forests in Peru and Colombia (Nunez-Iturri et al 2008, Stevenson and Aldana 2008, Terborgh et al 2008. Our approach, which contrasts results from experimental exclosures with results from a comparison of hunted and protected forests, will allow us to evaluate the effects of the loss of terrestrial seed predators in the presence and absence of arboreal and volant seed dispersers.…”

Diversidad y abundancia de primates y sus amenazas en el interfluvio de los ríos Napo y Putumayo, Amazonía peruana

“…Por otro lado, la alteración y pérdida de bosques ya sea por extracción de recursos forestales o de hidrocarburos traen como consecuencia la disminución de poblaciones de primates, pér-dida o fragmentación de hábitats, extinción local de especies, reducción en la frecuencia de dispersión de semillas y escasa población de árboles alimenticios (Peres 1997, Nuñez-Iturri & Howe 2007, Stevenson & Aldana 2008, Aquino et al 2015a). Más allá de estas consecuencias, está la inminente desaparición o pérdida de primates y ungulados como dispersores en el largo plazo.…”