Browsing by Autor "Vania Torrez"

Now showing 1 - 10 of 10

Bird assemblages in specialty coffee production landscapes in pre-montane humid subtropical forests
(2024) Nayra Antezana-Alvarado; Gabriel G. Torrico; Luis F. Pacheco; Camila Benavides-Frías; Vania Torrez; J. S. Jacobi
<title>Abstract</title> Coffee-related agricultural intensification affects bird species abundance, richness, and composition through habitat loss and degradation. Production of specialty coffee is expected to be more sustainable and environmentally friendly than conventional coffee. Nevertheless, not all specialty coffee is grown sustainably. To evaluate environmental sustainability, we evaluated the composition of bird assemblages in six specialty coffee-producing communities in Bolivia’s pre-montane subtropical humid forest region. To do this, we measured the diversity, richness, generalist and specialist species, and the effect of habitat on bird assemblages, comparing coffee plots and secondary forest plots as part of “Nature’s matrix”. We found significant differences in the abundance of generalist bird species. We did not find differences in the richness and diversity of specialist species. Plant strata, herbaceous leaf cover, and shrub leaf cover affected the assemblages of generalist species. Our results represent a first step toward understanding the intricate relationship between biodiversity and specialty coffee production, highlighting the importance of considering regional differences in landscape characteristics – conceived of as Nature’s matrix – when examining biodiversity in specialty coffee systems.
Caught in the Act: Incipient Speciation at the Southern Limit of <i>Viburnum</i> in the Central Andes
(Oxford University Press, 2024) Carlos A. Maya‐Lastra; Patrick W. Sweeney; Deren A. R. Eaton; Vania Torrez; Carla Maldonado; Malu I. Ore-Rengifo; Mónica Arakaki; Michael J. Donoghue; Erika J. Edwards
A fundamental objective of evolutionary biology is to understand the origin of independently evolving species. Phylogenetic studies of species radiations rarely are able to document ongoing speciation; instead, modes of speciation, entailing geographic separation and/or ecological differentiation, are posited retrospectively. The Oreinotinus clade of Viburnum has radiated recently from north to south through the cloud forests of Mexico and Central America to the Central Andes. Our analyses support a hypothesis of incipient speciation in Oreinotinus at the southern edge of its geographic range, from central Peru to northern Argentina. Although several species and infraspecific taxa have been recognized in this area, multiple lines of evidence and analytical approaches (including analyses of phylogenetic relationships, genetic structure, leaf morphology, and climatic envelopes) favor the recognition of just a single species, V. seemenii. We show that what has previously been recognized as V. seemenii f. minor has recently occupied the drier Tucuman-Bolivian forest region from Samaipata in Bolivia to Salta in northern Argentina. Plants in these populations form a well-supported clade with a distinctive genetic signature and they have evolved smaller, narrower leaves. We interpret this as the beginning of a within-species divergence process that has elsewhere in the neotropics resulted repeatedly in Viburnum species with a particular set of leaf ecomorphs. Specifically, the southern populations are in the process of evolving the small, glabrous, and entire leaf ecomorph that has evolved in four other montane areas of endemism. As predicted based on our studies of leaf ecomorphs in Chiapas, Mexico, these southern populations experience generally drier conditions, with large diurnal temperature fluctuations. In a central portion of the range of V. seemenii, characterized by wetter climatic conditions, we also document what may be the initial differentiation of the leaf ecomorph with larger, pubescent, and toothy leaves. The emergence of these ecomorphs thus appears to be driven by adaptation to subtly different climatic conditions in separate geographic regions, as opposed to parapatric differentiation along elevational gradients as suggested by Viburnum species distributions in other parts of the neotropics.
Caught in the Act: Incipient Speciation at the Southern limit of Viburnum in the Central Andes
(European Organization for Nuclear Research, 2023) Carlos A. Maya‐Lastra; Patrick W. Sweeney; Deren A. R. Eaton; Vania Torrez; Carla Maldonado; Malu I. Ore-Rengifo; Mónica Arakaki; Michael J. Donoghue; Erika J. Edwards
Repository for: Caught in the Act: Incipient Speciation at the Southern limit of Viburnum in the Central Andes In this repository, we are storing the following: HDF5 file of the assembly produced by ipyrad of our RADseq reads (bolivia_history.seqs.hdf5) HDF5 files with the SNPs found in item 1 (bolivia_history.snps.hdf5) Phylip file containing the final alignment used for the tree reconstruction (10-bolivia-initial_mcov0.25_rcov0.1_ALLscaff_SelectiveSampling.phy) For additional reproducibility material (scripts, notebooks) check: https://github.com/camayal/southern-oreinotinus
Disentangling environmental and spatial processes of community assembly in tropical forests from local to regional scales
(Wiley, 2015) Gabriel Arellano; J. Sebastián Tello; Peter M. Jørgensen; A C.; M. Isabel Loza; Vania Torrez; Manuel J. Macía
Understanding patterns and mechanisms of variation in the compositional structure of communities across spatial scales is one of the fundamental challenges in ecology and biogeography. In this study, we evaluated the effects of spatial extent (i.e. size of study region) on: 1) whether community composition can be better explained by environmental (i.e. niche‐based) or spatial (e.g. dispersal‐based) processes ; and 2) how climate and soils contribute to the influence of environment on plant community composition. We surveyed community composition across a network of 398 forest plots spanning a ∼4000 m elevational gradient in the Madidi region in northwestern Bolivia. Using redundancy analyses and hierarchical variation partitioning, we disentangled the effects of environmental and spatial predictors on species composition, further decomposing the environmental effect between its climatic and soil components. We repeated analyses for 200 sub‐regions ranging in spatial extent from ∼250 to ∼17 500 km 2 . Our analyses show a high degree of idiosyncrasy in results that come from different sub‐regions. Despite this variability, we were able to identify various important patterns in the structure of tropical plant communities in our study system. First, even though sub‐regions varied in size by nearly two orders of magnitude, the total amount of explained variation in community composition was scale independent; at all spatial scales, environment and space accounted for about 25% of the differences in community composition among plots. Second, the measured environmental effect was higher than the spatial effect on average and in the vast majority of sub‐regions. This was true regardless of the spatial extent of analysis. Finally, we found that both climatic and soil variables accounted for significant fractions of variation, but climate was always more important than soils.
Ecological quality as a coffee quality enhancer. A review
(Springer Science+Business Media, 2023) Vania Torrez; Camila Benavides-Frías; Johanna Jacobi; Chinwe Ifejika Speranza
Elevational Gradients in β-Diversity Reflect Variation in the Strength of Local Community Assembly Mechanisms across Spatial Scales
(Public Library of Science, 2015) J. Sebastián Tello; Jonathan A. Myers; Manuel J. Macía; A C.; Leslie Cayola; Gabriel Arellano; M. Isabel Loza; Vania Torrez; Maritza Cornejo; Tatiana B. Miranda
Despite long-standing interest in elevational-diversity gradients, little is known about the processes that cause changes in the compositional variation of communities (β-diversity) across elevations. Recent studies have suggested that β-diversity gradients are driven by variation in species pools, rather than by variation in the strength of local community assembly mechanisms such as dispersal limitation, environmental filtering, or local biotic interactions. However, tests of this hypothesis have been limited to very small spatial scales that limit inferences about how the relative importance of assembly mechanisms may change across spatial scales. Here, we test the hypothesis that scale-dependent community assembly mechanisms shape biogeographic β-diversity gradients using one of the most well-characterized elevational gradients of tropical plant diversity. Using an extensive dataset on woody plant distributions along a 4,000-m elevational gradient in the Bolivian Andes, we compared observed patterns of β-diversity to null-model expectations. β-deviations (standardized differences from null values) were used to measure the relative effects of local community assembly mechanisms after removing sampling effects caused by variation in species pools. To test for scale-dependency, we compared elevational gradients at two contrasting spatial scales that differed in the size of local assemblages and regions by at least an order of magnitude. Elevational gradients in β-diversity persisted after accounting for regional variation in species pools. Moreover, the elevational gradient in β-deviations changed with spatial scale. At small scales, local assembly mechanisms were detectable, but variation in species pools accounted for most of the elevational gradient in β-diversity. At large spatial scales, in contrast, local assembly mechanisms were a dominant force driving changes in β-diversity. In contrast to the hypothesis that variation in species pools alone drives β-diversity gradients, we show that local community assembly mechanisms contribute strongly to systematic changes in β-diversity across elevations. We conclude that scale-dependent variation in community assembly mechanisms underlies these iconic gradients in global biodiversity.
Mechanisms of community assembly explaining beta‐diversity patterns across biogeographic regions
(Wiley, 2021) Miguel Muñoz Mazón; J. Sebastián Tello; Manuel J. Macía; Jonathan A. Myers; Peter M. Jørgensen; Victoria Cala Rivero; Alfredo F. Fuentes; Vania Torrez; Gabriel Arellano
Abstract Aim We examined tree beta diversity in four biogeographical regions with contrasting environmental conditions, latitude, and diversity. We tested: (a) the influence of the species pool on beta diversity; (b) the relative contribution of niche‐based and dispersal‐based assembly to beta diversity; and (c) differences in the importance of these two assembly mechanisms in regions with differing productivity and species richness. Location Lowland and montane tropical forests in the Madidi region (Bolivia), lowland temperate forests in the Ozarks (USA), and montane temperate forests in the Cantabrian Mountains (Spain). Methods We surveyed woody plants with a diameter ≥2.5 cm following a standardized protocol in 236 0.1‐ha forest plots in four different biogeographical regions. We estimated the species pool at each region and used it to recreate null communities determined entirely by the species pool. Observed patterns of beta diversity smaller or greater than the null‐expected patterns of beta diversity implies the presence of local assembly mechanisms beyond the influence of the species pool. We used variation‐partitioning analyses to compare the contribution of niche‐based and dispersal‐based assembly to patterns of observed beta diversity and their deviations from null models among the four regions. Results (a) Differences in species pools alone did not explain observed differences in beta diversity among biogeographic regions. (b) In 3/4 regions, the environment explained more of the variation in beta diversity than spatial variables. (c) Spatial variables explained more of the beta diversity in more diverse and more productive regions with more rare species (tropical and lower‐elevation regions) compared to less diverse and less productive regions (temperate and higher‐elevation regions). (d) Greater alpha or gamma diversity did not result in higher beta diversity or stronger correlations with the environment. Conclusion Overall, the observed differences in beta diversity are better explained by differences in community assembly mechanism than by biogeographical processes that shaped the species pool.
Oligarchic patterns in tropical forests: role of the spatial extent, environmental heterogeneity and diversity
(Wiley, 2015) Gabriel Arellano; Peter M. Jørgensen; A C.; M. Isabel Loza; Vania Torrez; Manuel J. Macía
Abstract Aim Oligarchic patterns can vary from weak (i.e. little difference between rare and common species) to strong (i.e. a set of dominant species is immediately evident). Our aim was to understand the relationships between the strength of the oligarchic patterns, diversities (alpha, beta and gamma), and five potential causes (elevational variability, soil heterogeneity, elevation, soil conditions and geographical extent). Location The Amazon–Andes transition in the Madidi region (Bolivia). Methods We established 398 plots of 0.1 ha each, containing 121,183 individual woody plants belonging to 2390 species. Then we defined 500 sub‐regions (= unique overlapping subsets of 50 plots from the pool of 398 plots) so they varied in extent from 220 to 17,700 km 2 within the study area. We employed two independent path analyses to relate environmental characteristics and geographical extent of sub‐regions to (1) oligarchic strength and (2) alpha, beta and gamma diversities. We used generalized linear models to relate diversities to different measures of oligarchic strength. Results Oligarchies at larger extents were weaker, a trend strongly driven by the pure effect of area and, secondarily, by environmental heterogeneity. Oligarchies at higher elevations were weaker than expected, and oligarchies in acidic and nutrients‐poor soils were not stronger than those in less stressful soils. Trends in oligarchic strength were inversely correlated with those of gamma and beta diversity: weaker oligarchies were found in species‐rich and heterogeneous communities. Main conclusions Environmental heterogeneity and low landscape connectivity limit the strength of the oligarchic pattern. Although diversities (particularly beta diversity) and oligarchic strength are closely related, they are somewhat differently driven by external factors. In particular, oligarchic strength is more sensitive to spatial extent and less sensitive to environmental heterogeneity than beta diversity. Finally, the study of oligarchic patterns should consider a priori expectations based on species richness and turnover.
Phylogenetic patterns of rarity in a regional species pool of tropical woody plants
(Wiley, 2017) M. Isabel Loza; Iván Jiménez; Peter M. Jørgensen; Gabriel Arellano; Manuel J. Macía; Vania Torrez; Robert E. Ricklefs
Abstract Aim Rarity, which is believed to influence extinction risk, can be defined in terms of local abundance, geographical range size and habitat breadth. Phylogenetic patterns in these attributes provide insight into the extent to which rarity and extinction risk are conserved during evolution and the potential for species‐level heritability. We evaluated phylogenetic signal (i.e., related species resembling each other more than species drawn at random) and evolutionary conservatism (similarity among related species exceeding that expected from a Brownian model of evolution) in three axes of rarity (local abundance, geographical range size and habitat breadth) among species in a regional pool of tropical woody plants. Location The Madidi region in Bolivia. Time period 2001–2010. Major taxa studied Lignophyta clade. Methods We used a network of 48 1‐ha forest plots and 442 0.1‐ha forest plots to measure local abundance and habitat breadth of 1,700+ woody plant species (from 100+ plant families). We estimated geographical range size from occurrence records of individual species across the Neotropics. We characterized overall phylogenetic patterns of rarity using Blomberg's K and applied variance partitioning among taxonomic levels, as well as disparity analysis, to describe patterns of trait distribution at different depths in the phylogeny. Results We found phylogenetic signal, but not evolutionary conservatism, in the three axes of rarity. The variance in rarity among supra‐specific taxa, particularly families and genera, exceeded that calculated from random draws of species from the Madidi region. Phylogenetic signal, estimated by the proportion of variance among supra‐specific taxonomic levels, varied between 23 and 36% for local abundance and geographical range size, and between 9 and 10% for habitat breadth. Main conclusions The regional pool of woody plant species in Madidi exhibits phylogenetic signal in rarity that is consistent with biologically significant species‐level heritability.
Styloceras connatum (Buxaceae), una Nueva Especie de Bolivia
(Missouri Botanical Garden Press, 2010) Vania Torrez; Peter M. Jørgensen
Una nueva especie del género Styloceras Kunth ex A. Juss. (Buxaceae), fue encontrada en los bosques nublados del Parque Nacional Madidi y la Reserva Biosfera y Tierra Comunitaria de Origen Pilón Lajas en los Andes Bolivianos. Se describe e ilustra a S. connatum Torrez & P. Jørg., taxón que presenta similitudes morfológicas con S. penninervium A. H. Gentry & Aymard, pero se distingue de está por la consistencia de las hojas, número de anteras, color de flores y las características del fruto. Se proporciona una clave para la identificación de especies de Styloceras conocidas al presente.