Browsing by Autor "Mariana Villegas"

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BIRD COMMUNITIES RESPOND TO THE SEASONAL FRUIT AND FLOWER AVAILABILITY IN A FRAGMENTED TROPICAL ANDEAN LANDSCAPE
(2024) Mariana Villegas; César Mayta; Cecilia L. López; Isabell Hansen; Silvia C. Gallegos
Fire is one of the main causes of fragmentation in tropical Andean forests. Fragmentation can influence plant reproductive phenology, which in turn affects bird communities. In the Bolivian Yungas, we investigated how the seasonal availability of fruits and flowers affects bird richness, abundance and bird community composition in forest edges and adjacent bracken (Pteridium ferns) dominated areas. We captured birds with mist nets at eight sites during the dry, transition and wet seasons, and recorded fruit and flower availability through phenological observations and plant collections. We examined variation in species richness and abundance using generalized linear mixed-effects models, and bird species composition in each season using multivariate analyses. Fruit availability was higher in the transition and wet seasons, and lowest in the dry season, while flower availability did not differ among seasons. Bird species richness and abundance were significantly higher in bracken areas, although there was significantly lower fruit availability than at the forest edge, and these were mainly generalist bird species that may be tolerant to disturbance. Total bird abundance increased with higher fruit availability in both habitats, and with flower availability at the forest edge. Bird species composition differed between forest edges and bracken areas in the transition and the wet seasons, being influenced by fruiting and flowering phenology in the dry and transition seasons, and elevation in all seasons. Our results show the varying seasonal influence of plant reproductive phenology on avian communities of disturbed habitats, although other large scale factors associated with fragmentation may also shape bird communities.
Bird community responses to different urban conditions in La Paz, Bolivia
(Springer Science+Business Media, 2010) Mariana Villegas; Álvaro Garitano‐Zavala
Bird perches and artificial bat roosts increase seed rain and seedling establishment in tropical bracken‐dominated deforested areas
(Wiley, 2024) César Mayta; Cecilia L. López; Mariana Villegas; Luís F. Aguirre; Isabell Hensen; Silvia C. Gallegos
Tropical forests are being reduced by human activities. The use of fire for agricultural expansion generates areas dominated by the bracken fern Pteridium , where forest regeneration is slow. This may be caused by seed limitation, especially of animal‐dispersed seeds, due to the absence of seed dispersers from the forest in deforested areas, calling for restoration strategies to assist forest regeneration. We installed bird perches and artificial bat roosts to evaluate their effect on the density, species richness, and composition of animal‐dispersed seeds and seedlings of tree and non‐tree species in bracken‐dominated areas in the tropical montane forest of Bolivia. We found that perches and bat roosts increased the density and species richness of animal‐dispersed seeds and established seedlings. The seeds and seedlings dispersed by birds were clumped under the perches, while the seeds and seedlings dispersed by bats were distributed around the roosts. Perches had a higher density and species richness of seeds and seedlings compared to bat roosts, suggesting that the use of perches could be a better option as a restoration tool in bracken‐dominated areas. The increase in seed rain and seedling establishment of animal‐dispersed species in perches and bat roosts supports seed limitation, hindering forest succession in bracken‐dominated areas. The use of bird perches accompanying other restoration techniques is a promising restoration strategy to accelerate forest regeneration in tropical areas dominated by Pteridium , which are widely distributed.
Differences in bird and bat traits, seed-dispersal interactions and functions between tropical montane forest and bracken-dominated areas
(Frontiers Media, 2025) César Mayta; Matthias Schleuning; Cecilia L. López; Mariana Villegas; Isabell Hensen; Silvia C. Gallegos
Most tropical plant species depend on animals to disperse their seeds. Seed dispersal by animals allows plants to colonize new sites in deforested habitats helping to accelerate forest recovery. However, deforestation can affect the interactions between animals and plants that are crucial for forest regeneration. In this study, we analyze the differences on the composition of functional traits and on seed-dispersal interactions and functions by birds and bats between forest and deforested areas dominated by bracken fern. At eight study sites, we captured birds and bats in bracken-dominated areas and at forest in the tropical montane forest of Bolivia and analyzed their droppings. We found a similar composition of functional traits related to animal size, gape width and degree of frugivory of bats in both habitat types. Hand-wing index of birds was significantly higher in bracken compared to forest. Birds had more interaction richness and abundance in bracken than in forest, and bats had more interaction abundance in forest than in bracken. The majority of seeds dispersed by birds and bats in bracken were from pioneer species. We conclude that, although seed dispersal by birds and bats is maintained in the bracken-dominated areas, most of the dispersed seeds belong to pioneer species. Pioneer species are unlikely to establish in bracken-dominated areas, making the natural regeneration process of these deforested areas very slow.
Disentangling the roles of bracken fronds and litter on natural seedling recruitment in fire-disturbed tropical montane habitats
(Elsevier BV, 2024) Cecilia L. López; César Mayta; A C.; Mariana Villegas; Emili Antonia Jiménez; Víctor Vásquez; Isabell Hensen; Silvia C. Gallegos
Tropical montane forests are diverse ecosystems often affected by uncontrolled human-induced fires causing tree mortality and creating large deforested areas. After fires, Pteridium spp. ferns (bracken) often dominate, and forest regeneration in these areas is slow. In this study, we evaluated the effects of bracken fronds and litter, as well as the micro-environmental conditions created by the fern, on the density and species diversity of naturally recruiting seedlings. At eight sites, 120 experimental plots were established among forest and bracken-dominated areas with the following treatments: (a) fronds and litter intact (F+L+); (b) fronds intact and litter removed (F+L-); (c) fronds removed and litter intact (F-L+); and (d) fronds and litter removed (F-L-). After one year, all seedlings were registered, identified and classified according to their life-form (tree, shrub, herb, vine), dispersal vector (wind- or animal-dispersed) and successional status (early-, mid-, and late-successional). For all treatments we assessed 12 micro-environmental variables. We identified 3649 naturally-recruiting seedlings corresponding to 278 species from 70 families. We found positive effects of bracken fronds particularly on tree seedling recruitment: treatments with fronds had greater densities of both animal- and wind-dispersed tree seedlings, 1.8 and 1.4 fold higher, respectively, compared to treatments without fronds. Similarly, the density of early-, mid- and late-successional tree species was 1.3, 1.7 and 1.9 times higher in treatments with than without fronds. Furthermore, species diversity of early-, mid- and late-successional tree species was higher in the treatments with fronds. The environmental conditions generated by bracken presence, such as photosynthetically active radiation, soil temperature, live bracken biomass and litter depth, had positive effects on seedling density of all, animal-dispersed and early-successional tree species, and negative effects on seedling recruitment of other life-forms, notably from early successional stages. To promote forest regeneration in bracken-dominated areas, active restoration measures such as direct seed addition and transplants of nursery-raised seedlings of mid- and late-successional species should be considered. Since bracken can hinder the establishment of some life forms and species but favor others, it is recommended to include a trait-based approach to understand species responses to environmental factors and select species that are optimally adapted to bracken-dominated habitat conditions to promote forest regeneration. • Bracken facilitates seedling recruitment of mid- and late-successional tree species. • Bracken fronds’ shade increases species diversity of tree seedlings. • Bracken litter decreases natural recruitment of herbs. • Animal-dispersed species have higher recruitment under bracken fronds and litter.
Habitat differences in seed‐dispersing vertebrates indicate dispersal limitation in tropical bracken‐dominated deforested areas
(Wiley, 2024) Silvia C. Gallegos; César Mayta; Mariana Villegas; Guido Ayala; Kazuya Naoki; Josef Rechberger; V. D. Zambrana Rojas; María Viscarra; Nuria Bernal‐Hoverud; Mauricio Espejo
Abstract Shifting agriculture and anthropogenic fires are among the main causes of deforestation in the tropics. After fire and land abandonment, vast deforested areas are commonly dominated by the bracken fern Pteridium for long periods. Although forest regeneration in bracken‐dominated areas is mainly hindered by dispersal limitation, little is known about the role of seed‐disperser communities in slow forest succession. Our objective was to unravel the differences in the properties of the seed‐disperser communities between forests and bracken‐dominated areas to assess their role in dispersal limitation to foster ecological restoration. We compared species richness, diversity, abundance, and composition of seed‐dispersing birds, bats, and medium and large terrestrial mammals between both habitats in a montane forest of Bolivia. The species richness and diversity were similar for bats and higher for birds in bracken‐dominated areas than in the forest, but species composition was different between both habitats and groups. Although species composition was similar between both habitats for terrestrial mammals, the abundance was higher in the forest than in bracken‐dominated areas. Differences in species composition of seed‐dispersing birds and bats could be one of the main causes of dispersal limitation in forest regeneration in tropical bracken‐dominated areas. The few shared species between both habitats could explain the low seed rain of animal‐dispersed forest tree species in bracken‐dominated areas and the consequent hindered forest regeneration. Future studies relevant to natural forest regeneration should focus on analyzing the effects of animal‐attractants such as perches, artificial bat‐roosts, and seedling transplants on disperser communities, seed dispersal effectiveness, and forest regeneration. Abstract in Spanish is available with online material.
The use of bird perches and artificial bat roosts to overcome dispersal and establishment limitation in bracken-dominated deforested areas
(Elsevier BV, 2026) César Mayta; Cecilia L. López; Mariana Villegas; Isabell Hensen; Silvia C. Gallegos
The failure of seeds to arrive at suitable sites (dispersal limitation) and/or unsuitable conditions for germination, seedling survival and growth (establishment limitation) can impede the regeneration of tropical forests. We installed bird perches and artificial bat roosts in deforested areas dominated by the bracken fern Pteridium in the tropical montane forest of Bolivia to evaluate their effect on dispersal and establishment limitations. We also analyzed the relationship between seed size and life-history strategies of plants subject to both limitations. We found that perches reduced dispersal and establishment limitation of all seed sizes (small and large) and life-history strategies (pioneer and non-pioneer). In contrast, bat roosts did not reduce dispersal and establishment limitation in any of the categories. Our results reinforce the observation that dispersal limitation is one of the main filters that plant species must overcome in bracken-dominated deforested areas. The installation of bird perches as well as direct sowing of animal-dispersed seeds and planting of seedlings are strategies that could effectively support the regeneration of these widely distributed deforested areas.
Variación de la folivoría en Begonia parviflora (Begoniaceae) con relación a la edad foliar y fenología de la planta
(2004) Carlos M. Zambrana Torrelio; Mariana Villegas; Cinthya Ureña Aranda; Mónica Pacoricona