Biology subjects

Velasquez-Valencia, A.

Publications and source records attributed to Velasquez-Valencia, A..

4 recordsLinked to original sources

bioRxiv2025

Tree-Cover Gradients Modulate the Taxonomic and Functional Diversity of Birds in Amazonian Cattle-Ranching Landscapes

Cattle-ranching expansion is the major anthropogenic driver transforming forests in the Colombian Amazon. Landscapes typified by low ecological connectivity and simplified arboreal structure limit resource availability and alter avian species composition and functional-trait distributions. This study analyzed the relationship between the taxonomic and functional diversity of bird assemblages across four tree-cover categories (open (OP), semi-open (SO), semi-closed (SC), and closed (CL)) using 491 point counts from 104 cattle-ranching landscape mosaics in the northwestern Colombian Amazon. A trait matrix was compiled for 342 recorded species distributed among four trophic guilds. Margalef, Shannon, and Simpson indices, together with five functional diversity indices, were calculated, and correlation coefficients between indices were estimated by guild and cover type. The tree-cover gradient differentially influenced guild-level richness, evenness, and functionality. In open and semi-closed covers, insectivores showed greater functional richness, with traits adapted to foraging in open habitats, whereas intermediate vegetation supported higher evenness and functional complementarity in frugivores and granivores. Closed covers imposed stronger filtering on trait diversity. The results are consistent with metacommunity dynamics in which local assemblages and functional spillover sustain ecological processes at the mosaic scale. For cattle-ranching landscape management, reducing habitat contrast within the productive matrix and strengthening forest connectivity are recommended to conserve species richness and ecosystem functions.

ecology↗

bioRxiv2025

Livestock Landscapes as Ecological Filters: Effects of the Tree Cover Gradient on the Taxonomic and Functional Diversity of Granivorous Birds in the Colombian Amazon

Livestock landscapes in the Colombian Amazon are undergoing rapid land-use changes, leading to the structural simplification of vegetation and the loss of avifauna and its ecological functions. This study evaluated the effect of tree cover as an ecological filter on the taxonomic and functional diversity of granivorous birds within livestock mosaics. Eight livestock landscape mosaics were analyzed and classified based on tree cover into open, semi-open, and semi-closed categories. Bird surveys were conducted using point counts and mist netting, and eight morphological traits were measured across the 22 recorded species. Five functional diversity indices were calculated to assess the response to the tree cover gradient through their morphological traits. A reduction in tree cover excludes functionally specialized species and favors generalist communities with redundant traits. Semi-closed and semi-open covers harbored higher functional and taxonomic diversity, showing high levels of richness and functional evenness, with niche complementarity. Open pastures exhibited lower trait variability and clustering with reduced ecological functionality. Larger granivorous species were associated with denser vegetation, whereas smaller species were linked to more open, highly disturbed areas. Greater tree cover promotes the coexistence of granivorous bird species by increasing the availability of microhabitats and resource diversity, which are exploited by species with different functional traits. This highlights the importance of conserving structurally complex vegetation within livestock matrices, using silvopastoral systems to enhance the resilience and functionality of productive Amazonian landscapes.

ecology↗

bioRxiv2025

Morphometry and diversity of birds in cocoa agroforestry and silvopastoral systems in the Colombian Amazon

The primary cause of deforestation in the Amazon region is extensive traditional cattle ranching, which is considered an important economic activity in several departments of the region, particularly in Caqueta. This research aimed to determine the influence of vegetation cover on the morphometry and diversity of birds in agroforestry systems with cocoa and silvopastoral practices in the Colombian Amazon. Sampling was conducted in eight locations in the Caqueta department using mist nets between January and November 2023. In each location, five effective sampling days were carried out, and for each captured individual, weight and morphometric measurements of the bill, wings, legs, and tail were recorded. Based on the wing measurements, the Kipps index was calculated, relating the morphology to the dispersal capacity of the birds. A total of 350 individual birds were recorded, distributed across 77 species and 20 families in the sampled agroforestry systems with cocoa and silvopastoral practices. The Early Brush cover type exhibited the highest richness and abundance, and it was determined that the variation in the morphometric traits of the birds is associated with the type of habitat. The species accumulation curve from the collected mosaics allowed for the documentation and analysis of community richness in these two systems. It was determined that agroforestry systems with cocoa and silvopastoral practices, due to their tree structures simulating a heterogeneous habitat, have the capacity to host many species and are therefore important for the conservation of avifauna. Anthropization and fragmentation of natural habitats exert pressures on birds, leading to modifications in their morphometric traits to adapt to their environmental conditions.

ecology↗

bioRxiv2024

Evaluation of Three Diets Based on Dry, Live, and Wet Feeds for Optimal Growth of Discus Fish (Symphysodon p.) Under Controlled Conditions in Florencia, Caqueta, Colombia

This study evaluated the effect of three diets, wet (PAP), live (DAP) and commercial feed (COC), on the growth of juvenile discus fish (Symphysodon sp), under controlled environmental conditions in the Colombian Amazon. The PAP diet was made with animal protein and Amazonian fruits. The DAP diet consisted of the provision of live food (Moina macrocopa); Both diets were mixed in equal parts with the concentrate to be supplied to the fish. In the COC diet, only the commercial feed was supplied. The daily supply of each diet corresponded to 6% of the average body weight of the juveniles, adjusting the quantity in each measurement. Each treatment had four repetitions (aquarium), with a density of 0.32 individuals per liter for a total of 192 discus fish. The growth of the juveniles was monitored by taking morphometry every nine days for 63 days. The morphometric variables presented differences between the diets, the highest values were recorded in PAP and DAP. The morphometric variables such as total length and weight were positively associated with nutritional contents such as proteins, lipids and carbohydrates present in DAP and PAP. These components influenced the growth of the fish and were related to the feed conversion factor. It is suggested that fish fed with DAP and PAP continued to grow thanks to the biological and enzymatic stimuli provided by these foods, unlike the COC feeding with the lower growth reported. These results demonstrate that the combination of live foods prepared according to the habits and nutritional requirements of the species with concentrates promote the growth of the fish, promoting optimal development and general well-being of the discus fish during growth under controlled conditions.

physiology↗