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Vegetation and habitat diversity at the southern desert edge of the Sonoran Desert.
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... Expanding studies to other populations and using information from the whole-genome throughout the species' natural range should be of interest (particularly those on islands) and reveal adaptive differentiation among populations [4,76]. Of particular interest is the association of Hd and π with precipitation and temperature showing that S. thurberi thrives in sites with a well-defined and more predictable monsoon in the fringes of the Sonoran Desert where thornscrub and tropical dry forests develop [77,78]. The wide environmental differentiation across the peninsula suggests local adaptation to different water regimes. ...
Genetic differentiations and phylogeographical patterns are controlled by the interplay between spatial isolation and gene flow. To assess the extent of gene flow across an oceanic barrier, we explored the effect of the separation of the peninsula of Baja California on the evolution of mainland and peninsular populations of the long-lived columnar cactus Stenocereus thurberi. We analyzed twelve populations throughout the OPC distribution range to assess genetic diversity and structure using chloroplast DNA sequences. Genetic diversity was higher (Hd = 0.81), and genetic structure was lower (GST = 0.143) in mainland populations vs peninsular populations (Hd = 0.71, GST = 0.358 respectively). Genetic diversity was negatively associated with elevation but positively with rainfall. Two mainland and one peninsular ancestral haplotypes were reconstructed. Peninsular populations were as isolated among them as with mainland populations. Peninsular haplotypes formed a group with one mainland coastal population, and populations across the gulf shared common haplotypes giving support to regular gene flow across the Gulf. Gene flow is likely mediated by bats, the main pollinators and seed dispersers. Niche modeling suggests that during the Last Glacial Maximum (c. 130 ka), OPC populations shrank to southern locations. Currently, Stenocereus thurberi populations are expanding, and the species is under population divergence despite ongoing gene flow. Ancestral populations are located on the mainland and although vicariant peninsular populations cannot be ruled out, they are likely the result of gene flow across the seemingly formidable barrier of the Gulf of California. Still, unique haplotypes occur in the peninsula and the mainland, and peninsular populations are more structured than those on the mainland.
... In this desert, water (or lack thereof) is a key driver for trait evolution and population dynamics. Here, annual plants must contend with low and variable rainfall and high and variable temperature (Cox et al., 1988;Búrquez et al., 1999;. Indeed, this community has become a model system for understanding bet hedging through delayed germination in a variable environment (Venable, 2007;Gremer and Venable, 2014;Gremer et al., 2016;. ...
Rapid environmental change can affect both the mean and variability in environmental conditions. Natural selection tends to favour those organisms that best respond to such changes. Here, we consider delayed germination as bet hedging strategies for 10 Sonoran Desert annuals. We use a germination model parameterized with long-term demographic and climate data to explore potential effects of changes in the mean and variance in precipitation on the evolution of germination strategies, as well as the risk of extinction. We then explored the potential for evolutionary rescue in response to these changes. As expected, results indicate that as rainfall declines, or uncertainty in rainfall increases, all species have higher extinction risk (the former being more detrimental). These shifts also increased the benefit of delayed germination. Results also indicate that evolutionary rescue can often occur for small shifts, especially for more variable rainfall regimes, but would not likely save populations experiencing larger environmental changes. Finally, we identified life history traits and functional responses to precipitation that were most strongly correlated to the ability to cope with changes in rainfall and with potential for evolutionary rescue: dormant seed survivorship and, to a smaller degree, chance of reproduction and seed yield sensitivity to precipitation.
... In 2006, we established monitoring plots in 13 sites throughout the distribution range of the saguaro in Sonora, Mexico (Fig. 1), starting with an initial sample of 1,487 individuals. The selected populations are representative of the four continental subdivisions of the Sonoran Desert: Lower Colorado River Basin, Arizona Upland, Plains of Sonora, and Central Gulf Coast (Dimmitt 2000); we also included the thornscrub transition between the Sonoran Desert and the northernmost portion of the Mexican tropical deciduous forest of the Pacific coast (the foothills of Sonora [Búrquez et al. 1999]). ...
Each year, an individual mature large saguaro cactus produces about one million seeds in attractive juicy fruits that lure seed predators and seed dispersers to a 3‐month feast. From the million seeds produced, however, only a few will persist into mature saguaros. A century of research on saguaro population dynamics has led to the conclusion that saguaro recruitment is an episodic event that depends on the convergence of suitable conditions for survival during the critical early stages. Because most data have been collected in Arizona, particularly in the surroundings of Tucson, most research has relied on a limited amount of environmental variation. In this study, we upscaled this knowledge on saguaro recruitment to a regional scale with a new method that used the inverse‐growth modeling of 1,487 saguaros belonging to 13 populations in a latitudinal gradient ranging from arid desert to tropical thornscrub forest in Sonora, Mexico. Using generalized linear and additive mixed models, we created two 110‐yr‐long saguaro recruitment curves: one driven only by previous size, and the second driven by size, drought, and soil structure. We found evidence that saguaro recruitment is indeed episodic, with periodicities of 20–30 yr, possibly related to strong El Niño Southern Oscillation events. Our results suggest that saguaros rely on multidecadal periodic pulses of good beneficial years to incorporate new individuals into their populations. Inverse‐growth modeling can be used in a wide variety of plant species to study their recruitment dynamics.
... Although we do not know what the genetic structure of Washingtonia was before the arrival of the European missionaries, San Ignacio has been a mission since 1728 and our sampling site is close to the town making introduction of plant material from the south highly likely as our TreeMix results suggest (Supporting Information S5). Furthermore, San Ignacio is found in the transition of Shreve's Vizcaíno and La Giganta regions (Shreve & Wiggins, 1964) or Aschmann's Central Desert, where rainfall is bi-seasonal (Turner et al., 1995;Búrquez et al., 1999). Our Northern Peninsular region is equivalent to Shreve's Lower Colorado Valley (Shreve & Wiggins, 1964). ...
Washingtonia is a genus of palms currently composed of two species, W. filifera and W. robusta, distributed in the States of Baja California, Baja California Sur, and Sonora in Mexico, and Southern California and Arizona in the United States. The group has been a taxonomic challenge due to a lack of type specimens, incomplete protologues, highly variable vegetative morphology, human dispersal of seeds, limited fieldwork in native populations and poor representation in herbaria. Here, we analyse the population structure and phylogenetic relationships and test whether morphological traits correlate with genetic variation throughout its distributional range. We used genotyping-by-sequencing (GBS) data to identify population structure and delimit species. We further used these data to determine whether morphological traits varied among genetic regions. We analysed 188 individuals from 21 populations of Washingtonia across its distribution range using multivariate and Bayesian methods. Our results showed great consistency in the discovery of four genetic groups: (1) Southern Peninsula, (2) Mid-Peninsula, (3) Northern Peninsula and (4) Sonoran mainland. The geographical limits to these clusters coincide very well with the large natural regions of the Sonoran Desert. Our analyses indicate that Washingtonia populations are highly structured within four major geographical regions. Even when no single morphological trait can be used to determine the genetic identity of Washingtonia palms, leaf greenness, a novel morphological trait, can be useful. Our results provide a robust phylogenetic analysis of Washingtonia settling a taxonomic debate that has lasted over a century.
... Although we do not know what the genetic structure of Washingtonia was before the arrival of the European missionaries, San Ignacio has been a mission since 1728 and our sampling site is close to the town making introduction of plant material from the south highly likely as our TreeMix results suggest (Supporting Information S5). Furthermore, San Ignacio is found in the transition of Shreve's Vizcaíno and La Giganta regions (Shreve & Wiggins, 1964) or Aschmann's Central Desert, where rainfall is bi-seasonal (Turner et al., 1995;Búrquez et al., 1999). Our Northern Peninsular region is equivalent to Shreve's Lower Colorado Valley (Shreve & Wiggins, 1964). ...
Washingtonia is a genus of palms currently composed of two species, W. filifera and W. robusta, distributed in the States of Baja California, Baja California Sur, and Sonora in Mexico, and Southern California and Arizona in the United States. The group has been a taxonomic challenge due to a lack of type specimens, incomplete protologues, highly variable vegetative morphology, human dispersal of seeds, limited fieldwork in native populations and poor representation in herbaria. Here, we analyse the population structure and phylogenetic relationships and test whether morphological traits correlate with genetic variation throughout its distributional range. We used genotyping-by-sequencing (GBS) data to identify population structure and delimit species. We further used these data to determine whether morphological traits varied among genetic regions. We analysed 188 individuals from 21 populations of Washingtonia across its distribution range using multivariate and Bayesian methods. Our results showed great consistency in the discovery of four genetic groups: (1) Southern Peninsula, (2) Mid-Peninsula, (3) Northern Peninsula and (4) Sonoran mainland. The geographical limits to these clusters coincide very well with the large natural regions of the Sonoran Desert. Our analyses indicate that Washingtonia populations are highly structured within four major geographical regions. Even when no single morphological trait can be used to determine the genetic identity of Washingtonia palms, leaf greenness, a novel morphological trait, can be useful. Our results provide a robust phylogenetic analysis of Washingtonia settling a taxonomic debate that has lasted over a century.
... La precipitación cambia según la elevación y la influencia continental o costera, con una variación de entre 30 mm y 350 mm anuales. La temperatura en el verano alcanza máximos de 49°C al noroeste y en el invierno se presentan temperaturas bajo 0 °C en prácticamente todo el estado (Búrquez et al., 1999). ...
Desde finales del siglo XX se ha impulsado la megaminería en todo México, incluido el estado de Sonora que se caracteriza por la predominancia de ecosistemas áridos en su territorio. A partir de entonces se ha extendido la extracción de metales preciosos como el oro bajo la técnica de minería a cielo abierto. El presente trabajo analiza desde la óptica de la ecología política los conflictos socioambientales por megaminería en torno al agua en Sonora, en particular la contaminación por derrames y la falta de disponibilidad de agua. La información fue sistematizada y analizada a partir de fuentes periodísticas y académicas. Se identificaron 11 conflictos vinculados con el agua. Ocho se relacionan con la disminución en calidad a causa de un derrame y tres con la disminución en disponibilidad por acaparamiento de agua por parte de las empresas. El análisis refleja las debilidades del modelo de gobernanza ambiental predominante en México que antepone intereses privados a los públicos. Se argumenta a favor de la necesidad de devolverle al Estado la facultad de proteger los derechos humanos de la ciudadanía, entre ellos el derecho humano al agua.
... The temperature range on the islands is approximately 10°C narrower than on the peninsula, and the mean temperature of the warmest quarter is 4°C cooler. The biseasonal precipitation patterns of the Sonoran Desert Region (Shreve & Wiggins, 1964;Burquez et al. 1999) are represented by the influence on the model performance of the precipitation of both the warmest and coldest quarters. However, there is less precipitation on the islands than inland, during both seasons, with the most significant differences occurring during the warmest quarter. ...
Aim
Threats faced by narrowly distributed endemic plant species in the face of the Earth's sixth mass extinction and climate change exposure are especially severe for taxa on islands. We investigated the current and projected distribution and range changes of Cochemiea halei, an endemic island cactus. This taxon is of conservation concern, currently listed as vulnerable on the International Union for the Conservation of Nature Red List and as a species of special concern under Mexican federal law. The goals of this study are to (a) identify the correlations between climate variables and current suitable habitat for C. halei; (b) determine whether the species is a serpentine endemic or has a facultative relationship with ultramafic soils; and (c) predict range changes of the species based on climate change scenarios.
Location
The island archipelago in Bahía Magdalena on the Pacific coast, Baja California Sur, Mexico.
Methods
We used temperature and precipitation variables at 30‐arc second resolution and soil type, employing multiple species distribution modeling methods, to identify important climate and soil conditions driving current habitat suitability. The best model of current suitability is used to predict possible effects of four climate change scenarios based on best‐case to worst‐case representative concentration pathways, with projected climate data from two general circulation models, over two time periods.
Main conclusions
The occurrence of the species is found to be strongly correlated with ultramafic soils. The most important climate predictor for habitat suitability is annual temperature range. The species is predicted to undergo range contractions from 21% to 53%, depending on the severity and duration of exposure to climate change. The broader implications for a wide range of narrowly adapted, threatened, and endemic plant species indicate an urgent need for threat assessment based on habitat suitability and climate change modeling.
Genetic differentiations and phylogeographical patterns are controlled by the interplay between spatial isolation and gene flow. To test the extent of gene flow across an oceanic barrier, we explored the effect of the separation of the peninsula of Baja California on the evolution of mainland and peninsular populations of the long-lived columnar cactus Stenocereus thurberi . We analyzed twelve populations throughout the OPC distribution range to assess genetic diversity and structure using chloroplast DNA sequences. Genetic diversity was higher ( H d =0.81), and genetic structure was lower ( G ST =0.143) in mainland populations vs peninsular populations ( H d =0.71, G ST =0.358 respectively). Genetic diversity was negatively associated with elevation but positively with rainfall. Two mainland and one peninsular ancestral haplotypes were reconstructed. Peninsular populations were as isolated among them as with mainland populations. Peninsular haplotypes formed a group with one mainland coastal population, and populations across the gulf shared common haplotypes giving support to regular gene flow across the Gulf. Gene flow is likely mediated by bats, the main pollinators and seed dispersers. Niche modeling suggests that during the Last Glacial Maximum (c. 130 ka), OPC populations shrank to southern locations. Currently, Stenocereus thurberi populations are expanding, and the species is under population divergence despite ongoing gene flow. Ancestral populations are located on the mainland and although vicariant peninsular populations cannot be ruled out, they are likely the result of gene flow across the seemingly formidable barrier of the Gulf of California. Still, unique haplotypes occur in the peninsula and the mainland, and peninsular populations are more structured than these on the mainland.
Background
Arid and semi-arid regions account for about 40% of the world’s land surface area, and are the most sensitive areas to climate change, leading to a dramatic expansion of arid regions in recent decades. Ephemeral plants are crucial herbs in this area and are very sensitive to climate change, but it is still unclear which factors can determine the distribution of ephemeral plants and how the distribution of ephemeral plants responds to future climate change across the globe.
Aims
Understanding the impact of climate change on ephemeral plant distribution is crucial for sustainable biodiversity conservation.
Methods
This study explored the potential distribution of three types of ephemeral plants in arid and semi-arid regions (cold desert, hot desert, and deciduous forest) on a global scale using the MaxEnt software. We used species global occurrence data and 30 environmental factors in scientific collections.
Results
Our results showed that (1) the average value of the area under the receiver operating curve (AUC) of each species was higher than 0.95, indicating that the MaxEnt model’s simulation accuracy for each species was good; (2) distributions of cold desert and deciduous forest species were mainly determined by soil pH and annual mean temperature; the key factor that determines the distribution of hot desert species was precipitation of the driest month; and (3) the potential distribution of ephemeral plants in the cold desert was increased under one-third of climate scenarios; in the hot desert, the potential suitable distribution for Anastatica hierochuntica was decreased in more than half of the climate scenarios, but Trigonella arabica was increased in more than half of the climate scenarios. In deciduous forests, the ephemeral plant Crocus alatavicus decreased in nearly nine-tenths of climate scenarios, and Gagea filiformis was increased in 75% of climate scenarios.
Conclusions
The potential suitable distributions of ephemeral plants in the different ecosystems were closely related to their specific adaptation strategies. These results contribute to a comprehensive understanding of the potential distribution pattern of some ephemeral plants in arid and semi-arid ecosystems.
Fouquieria splendens is a stem-succulent native to the Chihuahuan, Mojave, and Sonoran Deserts that spans Mexico and the American Southwest. It is well-known for its variable morphology, the underlying reason for which remains incompletely understood. Here, we attempt to quantify the effect of topographic and interspecific factors on F. splendens morphology and distribution. To this end, we measured 27 ocotillos located in the Organ Pipe Cactus National Monument within the Sonoran Desert during June of 2019. We also quantified the spatial distribution of interspecific neighbors relative to F. splendens within two topographically different sites - a bajada gradient and a plain. Using ocotillo morphology, the distances to an ocotillo’s nearest neighbors, and hydrographic data extracted from the National Hydrography Dataset, we demonstrate 1.) the effect of major, desert, interspecific neighbors, like shrubs and cacti, on ocotillo morphology; 2.) the effect of elevation on intraspecific spacing as individuals compete for limited space; and 3.) a trade-off between height and number of branches. This places F. splendens morphology in its larger environmental and ecological context, highlighting the importance of individual traits and associated trade-offs among traits affected by topography and interspecific neighbors. By examining the ocotillo in a multi-species community and diverse landscape, this study provides empirical insight into a wider range of factors contributing to the variation in F. splendens morphology and spacing.
This updated and expanded A New Island Biogeography of the Sea of Cortés, first published nearly 20 years ago, integrates new and broader studies encompassing more taxa and more complete island coverage. The present synthesis provides a basis for further research and exploration in upcoming years of the biologically fascinating Sea of Cortés region. The Gulf region is increasingly being exploited, for its natural resources by way of marine fisheries, and for its stunning natural beauty by way of a burgeoning tourism industry. Further, the region's human population is increasing apace. It is appropriate, therefore, that this volume discusses these evolving circumstances, and the efforts of the Mexican government to regulate and manage them. The new Biogeography includes a section on the conservation issues in the Sea of Cortés, past accomplishments and conservation needs as yet outstanding. This book should be of strong interest to conservation biologists, ecologists, and evolutionary biologists more generally.
The reproductive biology of Merremia palmeri and the pollination efficiency of its insect visitors were examined for a Sonoran Desert population in northwestern Mexico. Pollen transfer experiments proved that the plant is self-incompatible. Reproduction is, therefore, dependent upon reliable visitation by the primary pollinators, hawk moths. Many aspects of the floral structure are typical of sphingophilous flowers, and the time of flower opening and nectar secretion corresponded to the period of greatest hawk moth activity. A single hawk moth visit to a flower could be sufficient for successful fertilization. Additional visits up to five increased percentage fruit set, but flowers that received six or more visits had lower fruit and seed set. Neither the number of moth visits nor fruit and seed set were correlated with temperature or relative humidity. Over the course of the study >55% of flowers set fruit. We conclude that hawk moths are reliable and efficient pollinators for M. palmeri in a warm desert habitat.
The vascular plant flora includes 271 species in 198 genera and 63 families. The Quitobaquito region supports c45% of the total flora of Organ Pipe Cactus National Monument, although the area constitutes only about 3.5% of the total area of the monument. Thirty-five are wetland plants; 33 species are not native to the region. Major vegetational and floristic changes have been due to human influences, which continue today. -from Authors
In order to establish relatively firm boundaries for the Sonoran Desert, climatic data from more than 250 weather stations were utilized to delineate this arid zone based upon the de Martonne Aridity Index. In additon, 17 conceptualizations (12 presented here) of the Sonoran Desert were mapped at the same scale to determine their relevance and consistency. -from Author