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Evaluation of fine-scale environmental heterogeneity and its effect on terrestrial mammal diversity in a grassland in the Chihuahuan Desert

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Abstract

Environmental heterogeneity is expected to increase the richness and diversity of species. The aim of this study is to identify environmental elements that influence the richness and diversity of small, medium and large species of mammals. For the sampling of mammals, camera and Sherman traps were used at 18 sampling stations. For vegetation sampling, eight large-scale explanatory variables were selected in a 1000 m² plot at each station. The diversity (H’) of habitats (heterogeneity) and species were measured using the Shannon–Wiener diversity index. To relate the heterogeneity and environmental variables with species richness for small, medium and large mammals, a generalised linear model (GLM) was used while considering the Poisson probability distribution. A multiple linear regression model was used for data with normal distributions. The results suggested that environmental elements could favour rodent richness but may have a negative effect on community evenness and some environmental variables that are related to the diversity of rodent species and the species richness of medium and large mammals. It was concluded that the relationship between environmental heterogeneity and mammal richness is complex and that the response to the biotic elements of the landscape is diverse and different for each species.

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Dipodomys phillipsii Gray, 1841 Southern Banner-tailed Kangaroo Rat Dipodomys phillipii [sic] Gray, 1841:522. Type locality "near Real del Monte," Hidalgo. Dipodomys ornutus Merriam, 1894:110. Type locality Berriozi-bal, Zacatecas. Dipodomys perotensis Merriam, 1894:111. Type locality Perote, Veracruz.
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Investigations concerning the ecology of small mammals have traditionally been conducted at the scale of individual patches with little consideration given to the structure of the surrounding landscape (Lidicker 1995). Research focused only at the scale of individual patches has resulted in an incomplete knowledge regarding the patterns of movement in small mammals. Although a large body of literature exists concerning movements of small mammals, previous studies have focused primarily on dispersal as a mechanism of population regulation and home range movements within a live-trapping grid (Hansson 1987, Szacki et al. 1993, Kozakiewicz and Szacki 1995). As a result, movements of small mammals have typically been considered to be limited in terms of distance, frequency, and habitat utilized (Szacki et al. 1993, Kozakiewicz and Szacki 1995).
Article
Grasslands are inherently dynamic in space and time, evolving with frequent disturbance from fire and herbivores. As a consequence of human actions, many remaining grasslands have become homogenous, which has led to reduced ecosystem function, biodiversity loss, and decreased ecological services. Previous research has shown that restoring inherent heterogeneity to grasslands can increase avian diversity, but the amount of heterogeneity (i.e., number of patches or fire return interval) and the impact on avian community stability have yet to be investigated. We used a unique landscape-level design to examine avian response to interacting fire and grazing across multiple experimental landscapes that represented a gradient of fire- and grazing-dependent heterogeneity. We used seven landscapes (430-980 ha; x = 627 ha) with varying levels of patchiness ranging from annually burned (one single patch) with spring-only fires to a four-year fire return interval with spring and summer fires (eight patches). This design created a range of heterogeneity as a result of pyric herbivory, an ecological process in which fire and grazing are allowed to interact in space and time. We found that greater heterogeneity across experimental landscapes resulted in increased avian diversity and stability over time. An index of bird community change, quantified as the sum of the range of detrended correspondence analysis axis site scores, was nearly four times greater in the most homogenous experimental landscape when compared to the most heterogeneous experimental landscape. Species responses were consistently positively associated with increased heterogeneity at the landscape scale, and within-experimental-landscape responses were most often related to litter cover, litter accumulation, and vegetation height. We conclude that increased fire- and grazig-dependent heterogeneity can result in high variability in the bird community at finer, transect scales, but increased diversity and stability at broad landscape scales. We recommend that future management efforts in rangelands focus on restored disturbance processes to increase heterogeneity and improve grassland bird conservation.
Article
Context: The expansive grassland biome is one of the most extensively transformed in South Africa, yet no strategy for monitoring its integrity is in place. A grassland health program, incorporating different ecosystem levels, was recently initiated. The suitability of three taxonomic groups as indicators has been tested so far: vegetation (by calculating an ecological index value, El), insects (using the South African grassland scoring system, SAGraSS) and small mammals (this study). All of these methods aim to be rapid and easy to perform. Whereas SAGraSS still needs further refinement, several factors already indicate the importance of including small mammal community parameters in integrity assessments.
Article
From 1996 to 2001, we conducted a study of two adjacent rodent communities in the Mapimi Basin of the Chihuahuan desert in Mexico. The objective was to test the resource level hypothesis in explaining differences in two contrasting but spatially close habitats: a tobosa grassland area (Hilaria mutica) and a mesquite (Prosopis glandulosa)–creosote (Larrea tridentata)–prickly pear (Opuntia rastrera) shrubland. Based on the inherent differences in the two habitats, we made the following predictions relative to the resource level hypothesis: (1) shrublands should have higher inherent density, diversity, and richness of small mammals than grasslands; (2) annual and seasonal changes in density, diversity, richness, and community composition should be more pronounced in grassland than in shrubland. Concerning the first set of predictions, rodent density was higher in the shrubland (17.7±1.1ind/ha) than the grassland (5.8±0.7ind/ha; F1,48=292.2, p⩽0.001). Overall species richness was equal in both habitats but the richness at any given time was significantly higher in shrubland (7.5±0.2 species vs. 5.6±0.3 species, F1,48=35.0, p⩽0.001). Species diversity, however, was equal in both habitats. Concerning the second set of predictions, rodent densities differed significantly in both areas annually (grassland: F5,24=10.9, p
Book
Principles and methods of landscape ecology are intensively used to model and to manage disturbed landscapes and menaced pristine areas as well. Students and professionals can find a new version of "Principles and Methods in Landscape Ecology" firstly published in 1998 by Chapman & Hall (London). Landscape ecology is an integrative and multi-disciplinary science and "Principles and Methods in Landscape Ecology" reconciles the geological, botanical, zoological and human perspectives. In particular new paradigms and theories like percolation, metapopulation, hierarchies, source-sink models, have been integrated, in this last edition, with the recent theories on bio-complexity, information and cognitive sciences. Methods for studying landscape ecology are covered including spatial geometry models and remote sensing in order to create confidence toward techniques and approaches that require a high experience and long-time dedication. Principles and Methods in Landscape Ecology is a textbook useful to present the landscape in a multi-vision perspective for undergraduate and graduate students of biology, ecology, geography, forestry, agronomy, landscape architecture and planning. Sociology, economics, history, archaeology, anthropology, ecological psychology are some sciences that can benefit of the holistic vision offered by this texbook. A relevant goal of this second edition is to increase confidence in the new generations of students and practitioners for considering the ecological systems as the result of the integration between ecosystemic (non spatial) and landscape (spatial) patterns and processes.
Article
The habitat heterogeneity hypothesis states that an increase in habitat heterogeneity leads to an increase in species diversity. We tested this hypothesis for a community of small mammals in the semiarid, sand-shinnery-oak ecosystem of the southwestern United States. We used indices of differentiation diversity to quantify differences between two habitat types (blowouts in a sand-shinnery-oak matrix) in terms of species diversity. The Wilson-Shmida index (βT) considers species composition only, whereas the Morisita-Horn index (CmH) also takes species abundances into account. We constructed null models to test the hypothesis that differentiation diversity between habitat types is greater than that produced by stochastic processes. Two models were constructed, one based on the random placement of species and one based on the random placement of individuals. No evidence supported the hypothesis that habitat heterogeneity enhances diversity of a landscape by increasing the number of species in an area. Indeed, paired habitats were more similar than chance alone would dictate in terms of species identities. In contrast, habitat heterogeneity affects diversity by significantly altering the relative proportions of species in contrasting habitat types. Because seeds differentially accumulate at the interface between blowouts and matrix, the high productivity of the edge may actually homogenize habitat types in terms of species richness. Nonetheless, blowouts might best be considered to be microhabitats which enhance or complement the value of the matrix even though the species which use either habitat type are identical.
Article
La escala y su importancia en el análisis espacial. El concepto de escala subyace a cualquier cometido de análisis espacial en ecología debido a que la heterogeneidad ecológica depende de la escala. Para evaluar su importancia, necesitamos descomponer el concepto de escala en tres dimensiones: ecológica, de muestreo y analítica. Nuestra capacidad de inferencia depende en gran medida de cómo las escalas de muestreo y análisis se ajustan a la dimensión espacial real del fenómeno ecológico. Los objetivos analíticos de los ecólogos en relación a la escala son, en primer lugar, determinar el reparto de variación de los fenómenos a lo largo de las escalas espaciales y, en segundo lugar, establecer cómo la covariación entre parámetros ecológicos cambia en función de la escala espacial. Para ambos fines, podemos considerar el espacio de forma explícita, con unidades de análisis definidas exclusivamente por características espaciales como posición, extensión y distancia, o bien de forma implícita, con niveles de heterogeneidad estructural biológica que suponen una variación en las características espaciales (p. ej. microhábitats, hábitats). Un problema analítico asociado a la escala es que el número de unidades de muestreo suele reducirse conforme se amplía la escala, disminuyendo la capacidad para detectar variación y covariación significativas. Frente a este problema, el novedoso Análisis de Coordenadas Principales de Matrices de Vecinos permite desglosar la varianza de un parámetro ecológico y generar valores predichos utilizables como variables respuesta en análisis de covariación, con la misma potencia analítica para distintas escalas espaciales.
Article
The history of the development of statistical hypothesis testing in time series analysis is reviewed briefly and it is pointed out that the hypothesis testing procedure is not adequately defined as the procedure for statistical model identification. The classical maximum likelihood estimation procedure is reviewed and a new estimate minimum information theoretical criterion (AIC) estimate (MAICE) which is designed for the purpose of statistical identification is introduced. When there are several competing models the MAICE is defined by the model and the maximum likelihood estimates of the parameters which give the minimum of AIC defined by AIC = (-2)log-(maximum likelihood) + 2(number of independently adjusted parameters within the model). MAICE provides a versatile procedure for statistical model identification which is free from the ambiguities inherent in the application of conventional hypothesis testing procedure. The practical utility of MAICE in time series analysis is demonstrated with some numerical examples.
Carnívoros: inventarios y monitoreos
  • López-González
Tree plantations replacing natural grasslands in high biodiversity areas: How do they affect the mammal assemblage?
  • Lezzi
The Chihuahuan Desert: a binational conservation response to protect a global treasure
  • Biggs
Interactions between the cotton rats
  • Petersen
Petersen, M., 1973. Interactions between the cotton rats. Sigmodon fulviventer and S. hispidus. Amer. Midl. Nat. 90, 319-333. https://doi.org/10.2307/2424456.
Guía para la identificación de los mamíferos de México en campo y laboratorio
  • S T Á Lvarez-Castañeda
  • T Lvarez
  • N González-Ruíz
Á lvarez-Castañeda, S.T., Á lvarez, T., González-Ruíz, N., 2015. Guía para la identificación de los mamíferos de México en campo y laboratorio. Centro de Investigaciones Biológicas del Noroeste, S. C. y Asociación Mexicana de Mastozoología, A. C., p. 522