Bat- and Bird-Generated Seed Rains at Isolated Trees in Pastures in a Tropical Rainforest

Abstract

Bats are abundant and effective seed dispersers inside the forest, but what happens when a forest is fragmented and transformed into pasture? The landscape at Los Tuxtlas, Mexico, originally rainforest, is greatly fragmented and covered with pastures. We analyzed the seed rains produced by frugivorous bats and birds under isolated trees in pastures in the fragmented landscape and the contribution of this process to vegetational recovery. We surveyed bats and obtained fecal samples under isolated trees in pastures. We also collected seed rain below the canopy of 10 isolated Ficus trees, separating nocturnally dispersed seeds from diurnally dispersed seeds. We caught 652 bats of 20 species; 83% of captures were frugivores. The most abundant species were Sturnira lilium (48%), Artibeus jamaicensis (18%), Carollia perspicillata (12%), and Dermanura tolteca (11%). Fecal samples contained seeds of 19 species in several families: Piperaceae (50%), Moraceae (25%), Solanaceae (12%), Cecropiaceae (10%), and others (3%). Sturnira lilium was the most important disperser bat in pastures. Seed rain was dominated by zoochorous species (89%). We found seed diversity between day and night seed captures to be comparable, but we found a significant interaction of disperser type ( bird or bat) with season. Seven plant species accounted for 79% of the seed rain: Piper auritum (23%), Ficus ( hemiepiphytic-strangler tree) spp. (17%), Cecropia obtusifolia (10%), P. amalago (10%), Ficus ( free-standing tree) spp. (8%), P. yzabalanum (6%), and Solanum rudepanum (5%). Bats and birds are important seed dispersers in pastures because they disperse seeds of pioneer and primary species (trees, shrubs, herbs, and epiphytes), connect forest fragments, and maintain plant diversity. Consequently, they might contribute to the recovery of woody vegetation in disturbed areas in tropical humid forests. tantes dispersores en pastizales ya que dispersan semillas de especies pioneras y primarias (árboles, arbustos, hierbas y epífitas); conectan remanentes de selva y mantienen la diversidad vegetal. Consecuentemente pueden promover la recuperación de la vegetación leñosa en áreas perturbadas de regiones tropicales húmedas.

Phenology of two Ficus species in seasonal semi-deciduous forest in Southern Brazil

“…Ficus adhatodifolia can be considered a relevant species in the food resources production for wildlife of the MGSP. In addition, this species can be used in reforestation, conservation and management of impacted ecosystems by being important food resource (Carauta and Diaz, 2002) and have the potential to attract frugivores (Cavalheiro et al, 2002), which could increase rain of propagules and introduce new species in such areas (Galindo-González et al, 2000;Guevara et al, 2004). According to Eshiamwata et al (2006), planting Ficus spp.…”

Early seed fall and seedling emergence: precursors to tropical restoration

“…regeneration of forests felled by hurricanes, in which seed banks and living seedlings and saplings promote rapid return of forests, as compared with large agricultural areas abandoned to re-growth, where regeneration is slow and species-poor (Boucher et al 2001). Seed dispersal into open areas is severely limited for most forest species (Martínez-Garza and González-Montagut 1999;Ingle 2003;Martínez-Garza et al 2009), unless relict fruiting pasture trees serve as ''magnet trees'' that attract animals that bring seeds which otherwise would not arrive (Guevara and Laborde 1993;Galindo-Gonzalez et al 2000). Preexisting seed banks are potentially important if the magnet effect of pasture trees results in seed deposition and emergence of species far from their sources.…”

Seed rain generated by bats under Cerrado’s pasture remnant trees in a Neotropical savanna

“…Importantly, scattered trees are used by a wide range of animals because the micro-ecosystem surrounding an individual tree greatly enhances structural complexity relative to its surrounds. Particularly, frugivorous bats make extensive use of scattered trees in many tropical landscapes (Galindo-González et al, 2000). The intense seed rain recorded under the studied trees indicates their importance, at least, as feeding roosts.…”

“…Much of these diaspores have comparatively low establishment success in pastures, while large seeds can have relatively high germination and establishment rates (Nepstad et al, 1996;Hooper et al, 2002; but see Lopez and Vaughan, 2004). In this respect, isolated trees may act as nuclei for forest recovery and can be a valuable and inexpensive tool for the reforestation of Neotropical habitats (Galindo-González et al, 2000). The concept of "nucleation" is used to describe the spreading of recovery from many different foci following a disturbance, wherein scattered trees play an important role (Franklin and MacMahon, 2000).…”

“…Many of these trees produce fleshy fruits, which attract frugivorous vertebrates to feed and rest within their fruiting canopies (Eshiamwata et al, 2006). As a result, frugivores often deposit large number of seeds from several species under remnant trees (Guevara and Laborde, 1993;Galindo-González et al, 2000;Slocum and Horvitz, 2000;Pausas et al, 2006). Then, the presence of trees may contribute to the recovery of environmental conditions favorable to tree regeneration processes (Parrotta et al, 1997;Lamb et al, 2005).…”