Over the last decades several studies have identified that the directional changes in climate induced by anthropogenic emissions of greenhouse gases are affecting the ecology of desert ecosystems. In the Southwest United States, the impacts of climate change to plant abundance and distribution have already been reported, including in the Sonoran Desert ecosystem, home of the iconic Saguaro (Carnegiea gigantea). Hence, there is an urgent need to assess the potential impacts of climate change on the saguaro. The goals of this study are to provide a map of actual habitat suitability (1), describe the relationships between abiotic predictors and the saguaro distribution at regional extents (2), and describe the potential effect of climate change on the spatial distribution of the saguaro (3). Species Distribution Modeling (SDM) was used to investigate the relationships between abiotic variables and the Saguaro distribution. SDMs were calibrated using presence records, 2,000 randomly-generated pseudo absences, and ten abiotic variables. Of these, annual precipitation and max temperature of the warmest month was found to have the greatest relative influence on saguaro distribution. SDMs indicated that 6.9% and 8.1% of the current suitable habitat is predicted to be lost by 2050 and 2070, respectively. Therefore, predicted changes in climate may result in a substantial contraction of the suitable habitat for saguaro over the next century. By identifying the drivers of saguaro distribution and assessing potential changes in habitat suitability due to climate change, this study will help practitioners to design more comprehensive strategies to conserve the saguaro in the face of climate change.

Este estudio fue diseñado para analizar la variación florística a lo largo de la costa del Pacífico entre Cook Inlet, Alaska (61º30'N) hasta el extremo sur de la península de Baja California, México (23º02'N), utilizando para ello los datos correspondientes a 965 inventarios fitosociológicos (que incluyen 686 plantas vasculares) obtenidos en el muestreo de 279 localidades costeras. Mediante un método de clasificación por agrupamientos (Average Linkage Clustering), y usando el índice de similitud de Sørensen como medida de la diversidad florística entre aquéllos, los datos de campo fueron relacionados con las cuatro regiones biogeográficas descritas en el área de estudio: Boreal-Norteamericana, Rocosiana, Californiana y Xerofítico-Mexicana. De acuerdo con sus respectivos patrones de distribución, los táxones registrados (géneros y especies) fueron agrupados en elementos florísticos. Los elementos florísticos, junto con la comparación entre los principales tipos de vegetación costera, sirvieron como criterios para realizar una clasificación fitogeográfica más detallada del área de estudio, en la que se han diferenciado ocho provincias florísticas. Las diferencias fitogeográficas actuales están condicionadas por ciertos acontecimientos paleoclimáticos y paleogeográficos que se discuten en este artículo. Las provincias boreales y templadas presentan porcentajes muy elevados de elementos de amplia distribución, cuyo origen hay que situar en la geoflora Boreotropical o Artoterciaria que dominó el hemisferio norte durante el Terciario. Las provincias florísticamente más diversas son las que se sitúan en la región Californiana, debido a que albergan elementos de las geofloras Artoterciaria y Madroterciaria. La flora tropical de la península de Baja California se caracteriza por un elevado núme-ro de táxones relacionados con la flora neotropical, especialmente con la de Sudamérica. This study was designed to explore floristic variation along the Pacific coast from Cook Inlet, Alaska (61º30'N), to the southern tip of Baja California, Mexico, at 23º02'N. Data corresponding to 965 phytosociological relevés (including 686 vascular plants) obtained by sampling 279 coastal sites were examined. Using an objective classification system (Average Linkage Clustering) and Sørensen's index, floristic data acquired in fieldwork were related to the biogeographical regions of the study area. According to the worldwide distribution pattern of genera and species, the registered taxa were grouped into phytogeographical elements. These elements, along with the climatic classification of the sites and comparisons among the main coastal vegetation types, gave rise to a phytogeographical classification of the study area in which four regions (North American Boreal, Rocky Mountain, Californian and Xerophytic-Mexican) and eight floristic provinces were distinguished. Each province is characterized by its climate, changes in phytogeographic elements, the presence of endemic genera or species, and by its characteristic vegetation types. Floristic ...

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Background: seasonally dry tropical forests are considered critical and important ecosystems because they harbor exceptional biological diversity. Mexico lacks sound phytosociological studies of Seasonally Dry Tropical Forest and Michoacán is no exception. The present study may be regarded the first phytosociological in most of the Mexican pacific coast where seasonally dry tropical forests occurs. Questions/Objective: We aimed at describing the representative plant associations of the seasonally dry tropical forest, distributed on western Michoacán and to provide a sintaxonomic classification framework based on the floristic differentiation of the recognized communities and highlight its phytocenotic diversity. Study site and dates: Estado de Michoacán; 20 years. Methods: A total of 82 phytosociological inventories were conducted. Data were submitted to multivariate two-way indicator species analyses to depict plant communities and their ecological affinities. Results: From its analysis and interpretation, nine plant groups were differentiated, of which all but one was given the rank of association, which are Lysilomo acapulcensis–Heliocarpetum terebinthinacei, Ceibo aesculifoliae–Lysilometum divaricatae, Caesalpinio platylobae-Cordietum elaeagnoidis, Cochlospermo vitifolii-Lueheetum candidae, Lysilomo divaricatae-Cordietum elaeagnoidis; Stenocereo quevedonis-Cordietum selerianae, Guazumo ulmifoliae-Cordietum elaeagnoidis¸ Lonchocarpo huetamoensis-Cordietum elaeagnoidis and the community of Spondias purpurea-Cochlospermum vitifolium. Conclusions: Comparative floristic and structural profiles among plant communities permitted us to distinguish their bioclimatic relationships. Diagnostic species representative of all plant associations were selected and used for sintaxonomic nomenclature.  Plant associations were finally array along bioclimatic and altitudinal gradients and showed in arranged phytosociological tables. The plant association/community’descriptions permitted to compare structural physiognomy, floristic composition, ecological affinities, distribution patterns and bioclimatic liaison among them.

En este trabajo se abordan las relaciones entre el clima y la vegetación en el territorio de la vertiente del Pacífico Mexicano, considerada como una franja de 100 km de ancho que desde el litoral se extiende hacia tierra adentro y cuyos extremos norte y sur coinciden con la frontera de México con los Estados Unidos de América y con Guatemala respectivamente. Las relaciones fueron establecidas a partir del análisis bioclimático efectuado con los datos de precipitación y temperatura de 691 estaciones meteorológicas existentes en el área de estudio. La diagnosis bioclimática permitió identificar los macrobioclimas Mediterráneo y Tropical, los bioclimas Mediterráneo Pluviestacional Oceánico, Mediterráneo Xérico Oceánico, Mediterráneo Desértico Oceánico, Mediterráneo Hiperdesértico Oceánico, Tropical Pluvial, Tropical Pluviestacional, Tropical Xérico, Tropical Desértico y Tropical Hiperdesértico, y 30 isobioclimas. Los muestreos de campo se dirigieron hacia la caracterización fisionómica y florística de la vegetación natural potencial de las diferentes unidades bioclimáticas, estableciendo así los principales elementos diagnósticos (bioindicadores y fisionómico-estructurales) de la secuencia bioclimática a lo largo del gradiente latitudinal.