Gypsum Dunes Research Articles

Great Salt Lake desert landscape change over multiple temporal scales

This one-day (~260-mile) field trip guide provides an overview of the late Pleistocene to Holocene history of the Great Salt Lake Desert. Stops include Knolls Sand Dunes and areas on or surrounding the Bonneville Salt Flats, such as Juke Box trench, the Bonneville Salt Flats International Speedway, and the saline pan center and edge (Figure 1). We cover the post-Lake Bonneville geomorphic evolution of the Great Salt Lake Desert including changes in land cover over the past century. The Great Salt Lake Desert area provides unique access to saline landscape features including gypsum dunes and a perennial saline pan. We discuss the origin of these features and how they fit within the area’s broader geologic context. The accessibility of sites discussed here depends on surface conditions. In general, late summer to early fall is the most opportune time to visit this area. Vehicular travel to any of the off-road sites is discouraged when there is standing water or high near-surface moisture (wet mud with little traction). Surface conditions can change rapidly, and we recommend researching current conditions before initiating this trip. This desert is hot and dry during the summer and there is no shade and limited access to water; please plan accordingly. Past and current Great Salt Lake Desert depositional changes provide an analog for the modern Great Salt Lake with changing water availability, potential dust production, competing priorities, and rapidly changing land cover. The information presented here impacts understanding natural and geologic heritage, changing management strategies, and landscape dynamism over multiple spatial and temporal scales.

Onset of dune construction based on archaeological evidence, White Sands, New Mexico

AbstractThe White Sands dune field is the largest gypsum dune system in the world, derived from deflation of paleo-Lake Otero deposits. Understanding the timing of initial dune construction, and therefore lake deflation, is critical for understanding regional landscape evolution, including the history of lake desiccation. The onset of dune construction is currently estimated at ~8000 to 6500 cal yr BP, but numerical age control is limited. Archaeological evidence reported here indicates two older phases of gypsum dune construction. An archaeological site draped over a parabolic dune south of the main dune body contains artifacts dating to >12,200 cal yr BP, providing an upper age limit for the landform. Another site buried within a remnant of the main dune field yielded six statistically identical radiocarbon dates averaging ~8770 cal yr BP. The initial phase of terminal Pleistocene deflation and parabolic dune construction was perhaps localized but correlates with a period of regional aridity. Barchans and crescentic ridges comprising the main dune body developed in the Early Holocene in response to elevated salinity in local ground water and extensive exposures of gypsum available for deflation, likely due to aridity.

Repeated evolution of blanched coloration in a lizard across independent white-sand habitats.

The White Sands lizards of New Mexico are a rare and classic example of convergent evolution where three species have evolved blanched coloration on the white gypsum dunes. Until now, no geological replicate of the pattern had been described. However, one of the White Sands species, the lesser earless lizard (Holbrookia maculata), has been discovered to also inhabit the Salt Basin Dunes of Texas, where it has also evolved a blanched morph. We here present a first phenotypic and genetic description of the Salt Basin Dunes population of H.maculata. Phylogenetic inference based on a housekeeping gene (ND4) and a classic candidate gene in the melanin-synthesis pathway (Melanocortin 1 Receptor; Mc1r) shows the newly discovered population as an independent lineage, with no evidence of genetic parallelism in the coding region of Mc1r. Initial morphological data suggest that while this population displays convergent evolution in blanched coloration, there are divergent patterns in limb length and habitat use behavior between the gypsum environments. Our findings present the White Sands/Salt Basin Dunes as an exceptionally promising comparative model for studies of adaptation and convergent evolution.

A new species of tree cricket (Orthoptera, Gryllidae, Oecanthinae) from Chihuahuan Desert gypsum dunes in the United States and a key to the nigricornis species group

A new species of tree crickets, Oecanthus beamerisp. nov., is described from the gypsum dunes of White Sands National Park in New Mexico, United States. The new species is currently known only from the type locality, where it appears to be specific to the gypsophile plant hoary rosemary mint (Poliomintha incana). This new species has the narrowed tegmina and calling song that are found in the nigricornis species group. Although it has morphological similarities to O. quadripunctatus and O. celerinictus, there are differences in the subgenital plates, tegminal measurements, coloring, tibial markings, song frequency, and song pulse rate. This new species has been given the common name White Sands tree cricket. We provide a key to all species in the nigricornis group. Video and song recordings are available online as Suppl. materials 1–8.

Donald Pinkava’s studies on the vascular flora of the Bolsón de Cuatro Ciénegas in the Chihuahuan Desert, updates, and taxonomic information on Acanthaceae in the region

In 1967 Donald Pinkava began botanical exploration of the then little-studied Bolsón de Cuatro Ciénegas in the east-central portion of the Chihuahuan Desert. This closed (i.e., internally drained) basin contains an unusual assemblage of biotic communities in a relatively small region. Following 10 years of field studies, between 1979 and 1984 Pinkava published catalogs of the vascular flora of his 2,000 km2 study area, and documented 860 species in 456 genera from 114 families. He also recognized and summarized eight “vegetation zones” in the study area: aquatic and semiaquatic habitats, gypsum dunes, basin sacaton grasslands, a transition zone, desertscrub, chaparral, oak-pine and oak woodlands, and montane conifer forests. Some updates and discussions are offered relative to both the flora and vegetation of the basin area. The botanical richness of this region is illustrated by Acanthaceae. A key to and synopsis of the 13 species in six genera of that family occurring there are provided. Lists comparing Acanthaceae in the Sonoran and Chihuahuan deserts are also appended. Pinkava’s pioneering botanical inventory in and around the Bolsón de Cuatro Ciénegas was both timely and has had a significant impact on subsequent efforts to preserve this precious natural resource of international significance.

“Extracellular Polysaccharide Synthesized by the Halophilic Bacterium Salibacterium halochares STm, Isolated from Gypsum Dunes: Production, Physicochemical Characterization and Emulsifying Properties”

“Extracellular Polysaccharide Synthesized by the Halophilic Bacterium Salibacterium halochares STm, Isolated from Gypsum Dunes: Production, Physicochemical Characterization and Emulsifying Properties”

Assessment of Sulfate Sources under Cold Conditions as a Geochemical Proxy for the Origin of Sulfates in the Circumpolar Dunes on Mars

Determining aqueous sulfate sources in terrestrial cold environments can provide an insight into the surface hydrological conditions and sulfur cycle on Mars. In this study, we analyzed sulfur and oxygen isotope compositions of secondary sulfate salts (e.g., gypsum, thenardite) in the surficial sediments and soils of the McMurdo Dry Valleys (MDV), Antarctica to determine contributions of sulfate from bedrock chemical weathering and atmospheric deposition under persistent dry polar conditions. The sulfate showed wider variation of δ34S (+15.8‰ to +32.5‰) compared to smaller ranges of δ18O (−8.9‰ to −4.1‰). In contrast, the δ34S of bedrock sulfide showed significantly lower and consistent values across the studied area (−0.6‰ to +3.3‰). Based on the δ34S trends, sulfide weathering may contribute up to 20–50% of secondary sulfate salts in the MDV. While the remaining 50–80% of sulfate inputs may originate from atmospheric deposition (e.g., sea aerosols, dimethulsulfide oxidation), the subglacial brines derived by relicts of seawater and/or lake/pond water influenced by microbial sulfate reduction could also be important sulfate endmembers particularly in the Antarctic lowland thaw zones. Additional field observations of frost, ponding water, and thin gypsum crusts on the terrestrial gypsum dunes at White Sands supports reactivity of gypsum on the surface of these dunes during cold winter conditions. Combined with our improved geochemical model of the sulfur cycle for cold Antarctic settings, we propose that transient liquid water or frost was available in near-surface environments at the time of gypsum formation in the north polar region on Mars. Ice and/or water interaction with basaltic sand of the basal unit (paleo-erg) would have enhanced leaching of sulfate from both sulfide oxidation and atmospheric deposition and resulted in formation of secondary gypsum salts.

Dust Production by Abrasion of Eolian Basalt Sands: Analogue for Martian Dust

AbstractDust is nearly ubiquitous on Mars, covering much of the planet's surface, having been redistributed by dust storms. Analysis of dust via landed instrumentation indicates a basaltic composition for its protolith; the same is interpreted for the dark dune sands encountered at rover field sites. In this paper, we used samples of eolian sands derived from basaltic volcanoes in an experiment to simulate dust production from basalt dune sands within an abrasion chamber. In addition, we used samples from gypsum dunes because gypsum is found within dune fields on the northern plains of Mars. The results, expressed as weight percent of sample reduced to dust, show a remarkably broad range over 4 orders of magnitude. Eolian abrasion of basalt sands can produce similar amounts of dust, as is the case for some desert sands on Earth. Some plausible Mars analogue materials can produce large amounts of dust, suggesting that eolian movement of basaltic sand and volcanic sediments on the surface of Mars is a potential source of fine‐grained sediment or dust.

IMARS Phase 2A Draft Mission Architecture and Science Management Plan for the Return of Samples from Mars Phase 2 Report of the International Mars Architecture for the Return of Samples (iMARS) Working Group.

iMARS Phase 2A Draft Mission Architecture and Science Management Plan for the Return of Samples from Mars Phase 2 Report of the International Mars Architecture for the Return of Samples (iMARS) Working Group.

Convergent Phenotypic Evolution despite Contrasting Demographic Histories in the Fauna of White Sands.

When are evolutionary outcomes predictable? Cases of convergent evolution can shed light on when, why, and how different species exhibit shared evolutionary trajectories. In particular, studying diverse species in a common environment can illuminate how different factors facilitate or constrain adaptive evolution. Here we integrate studies of pattern and process in the fauna at White Sands (New Mexico) to understand the determinants of convergent evolution. Numerous animal species at White Sands exhibit phenotypic convergence in response to a novel-and shared-selective environment: geologically young gypsum dunes. We synthesize 15 years of research on White Sands lizards to assess the contribution of natural selection, genetic architecture, and population demography to patterns of phenotypic evolution. We also present new data for two species of White Sands arthropods, Ammobaenetes arenicolus and Habronattus ustulatus. Overall, we find dramatic phenotypic convergence across diverse species at White Sands. Although the direction of phenotypic response is parallel, the magnitude of phenotypic response varies among species. We also find that species exhibit strikingly different demographic patterns across the ecotone. The species with the most genetic structure between White Sands and dark-soil populations generally exhibit the least phenotypic divergence, suggesting population demography as a key modulator of adaptation. Comparative studies are particularly important for understanding the determinants of convergence in natural systems.

Ephemeral liquid water at the surface of the martian North Polar Residual Cap: Results of numerical modelling

Gypsum, a mineral that requires water to form, is common on the surface of Mars. Most of it originated before 3.5Gyr when the Red Planet was more humid than now. However, occurrences of gypsum dune deposits around the North Polar Residual Cap (NPRC) seem to be surprisingly young: late Amazonian in age. This shows that liquid water was present on Mars even at times when surface conditions were as cold and dry as the present-day. A recently proposed mechanism for gypsum formation involves weathering of dust within ice (e.g., Niles, P.B., Michalski, J. [2009]. Nat. Geosci. 2, 215–220.). However, none of the previous studies have determined if this process is possible under current martian conditions. Here, we use numerical modelling of heat transfer to show that during the warmest days of the summer, solar irradiation may be sufficient to melt pure water ice located below a layer of dark dust particles (albedo⩽0.13) lying on the steepest sections of the equator-facing slopes of the spiral troughs within martian NPRC. During the times of high irradiance at the north pole (every 51ka; caused by variation of orbital and rotational parameters of Mars e.g., Laskar, J. et al. [2002]. Nature 419, 375–377.) this process could have taken place over larger parts of the spiral troughs. The existence of small amounts of liquid water close to the surface, even under current martian conditions, fulfils one of the main requirements necessary to explain the formation of the extensive gypsum deposits around the NPRC. It also changes our understanding of the degree of current geological activity on Mars and has important implications for estimating the astrobiological potential of Mars.

When field experiments yield unexpected results: lessons learned from measuring selection in White Sands lizards.

Determining the adaptive significance of phenotypic traits is key for understanding evolution and diversification in natural populations. However, evolutionary biologists have an incomplete understanding of how specific traits affect fitness in most populations. The White Sands system provides an opportunity to study the adaptive significance of traits in an experimental context. Blanched color evolved recently in three species of lizards inhabiting the gypsum dunes of White Sands and is likely an adaptation to avoid predation. To determine whether there is a relationship between color and susceptibility to predation in White Sands lizards, we conducted enclosure experiments, quantifying survivorship of Holbrookia maculate exhibiting substrate-matched and substrate-mismatched phenotypes. Lizards in our study experienced strong predation. Color did not have a significant effect on survival, but we found several unexpected relationships including variation in predation over small spatial and temporal scales. In addition, we detected a marginally significant interaction between sex and color, suggesting selection for substrate matching may be stronger for males than females. We use our results as a case study to examine six major challenges frequently encountered in field-based studies of natural selection, and suggest that insight into the complexities of selection often results when experiments turn out differently than expected.

The Lepidoptera of White Sands National Monument 7: A New Species of the Genus Areniscythris (Scythrididae), a Recently Discovered Iconic Species from the Monument

A new species of Scythrididae, Areniscythris whitesands sp. nov. Metzler and Lightfoot, is described from a series of specimens that were found active during the daytime on open bare sand of the white gypsum dunes at White Sands National Monument, Otero Co., New Mexico. Adults and genitalia of the male and female are illustrated, and the bionomy of the species is shortly discussed.

The remarkable endemism of moths at White Sands National Monument in New Mexico, USA, with special emphasis on Gelechioidea (Lepidoptera)

The white sands formation, a snow-white gypsum dunes system, is the world's largest gypsum dune field. White Sands National Monument protects about 40% of the dunes; the dunes formation as it is known today was formed ca. 8,000 years BP. Prior to 8,000 years BP, the area covered by the dunes was a wet cool forest of the last glacial maximum in North America. The dunes were formed as a result of the hypsithermal, a warming and drying period which followed the most recent glacial maximum. The white sands formation is located in south central New Mexico in the Tularosa Basin of southwestern United States. A 10-year study of moths at the dunes was commissioned by the U. S. National Park Service in 2006. Almost immediately species new to science were detected. In the period of 6 years, 30 new species were discovered in the dunes. Several of the new species are white or very pale in color, and are endemic to the dunes. The focus of the 10 year project was modified to emphasize naming the undescribed species which helps the National Park Service catalog and manage the habitats. The data should encourage other researchers to explore the interactions of the animals with the plants and the harsh desert environment, to study DNA and evolution, and to study the rapid adaptation which seems to be occurring.

Asymmetrical mate preference in recently adapted White Sands and black lava populations of Sceloporus undulatus

Abstract Speciation can proceed rapidly when natural and sexual selection act in concert. For example speciation can be accelerated when traits that confer a selective advantage in a particular habitat also influence mate preference. Studying parallel but evolutionarily independent instances of ecological divergence can illuminate the interaction between natural and sexual selection during speciation. Locally adapted populations of the eastern fence lizard Sceloporus undulatus have recently evolved in three different habitats in the Chihuahuan desert: blanched color morphs occur on the gypsum dunes of White Sands, melanic color morphs occur on the Carrizozo lava flow, and brown color morphs occur in the surrounding desert scrubland. In addition to differences in cryptic dorsal coloration, populations also differ in the size and color of ventral patches used for social signaling. This system therefore provides an opportunity to investigate the interplay of natural and sexual selection during rapid ecological speci-ation. We used mate preference experiments to determine whether locally adapted populations may exhibit the early stages of behavioral reproductive isolation. We observed an asymmetrical mate preference in this system; White Sands males preferentially courted local females, while males from dark soils and black lava populations did not exhibit a preference for local mates. We also found that female behavior and ventral patch phenotype were associated with male courtship. Our results suggest that the observed preference for local mates evolved at White Sands, and we discuss the possible link between local adaptation and traits involved in mate preference in this system.

Microbial Nitrogen and Sulfur Cycles at the Gypsum Dunes of White Sands National Monument, New Mexico

The White Sands National Monument from New Mexico (U.S.A) contains one of the largest known gypsum dune fields with unique, rapidly migrating, arid, evaporitic habitats. Deposits from dune sides and interdune areas were collected in order to determine the characteristics of microbial habitat and communities through mineral assemblages, microbial pigments along with investigations of nitrogen and sulfur cycles. The most abundant pigments, scytonemin and carotenoids, were common UV protective pigments. Predominance of nitrite and nitrate over ammonium nitrogen (2.16: 1) implies that nitrification processes might be important in this ecosystem. Ammonium oxidizers from groups of β-, γ-proteobacteria and archaea were detected in all deposits, thereby indicating microbial involvement in nitrification. Additionally, denitrifying organisms with nirS and nirK genes were also present in most of the analyzed samples. The presence of trace carbonate mineral phases in association with biofilm implies possible microbial sulfate reduction. Microbes with metabolic abilities for sulfur cycling (i.e., dissimilatory sulfite reducers, purple sulfur bacteria, green sulfur and non-sulfur bacteria, and organisms with the APS enzyme) were identified in all samples. These particular organisms have the ability to reduce sulfate and to re-oxidize reduced sulfur compounds back to sulfate.

Colonization of novel White Sands habitat is associated with changes in lizard anti-predator behaviour

Colonization of novel habitats is often associated with differences in ecological community composition. For small diurnal animals, differences in predator diversity and abundance can lead to behavioural shifts in the novel habitat. The eastern fence lizard Sceloporus undulatus (Bosc and Daudin, 1801) recently colonized the gypsum dunes of White Sands, a predator-poor community relative to the predator-rich community of the surrounding Chihuahuan dark-soil habitat. We used field experiments to assess S. undulatus anti-predator behaviour in white-sand versus dark-soil habitats, and used laboratory assays to determine whether behavioural differences could be mediated by hormonal regulation. Overall, we found that white-sand lizards were less vigilant but more wary than their dark-soil counterparts; it took them longer to detect a simulated predator, but once detected they were more likely to retreat from their perches than dark-soil lizards. At the proximate level, differences in anti-predator behaviour could not be explained by differences in plasma hormone levels (corticosterone and testosterone); we detected elevated corticosterone for lizards in our stress treatment relative to control treatment, but found no differences between habitats in baseline or acute corticosterone levels. At the evolutionary level, we suggest that differences in anti-predator behaviour may be explained by differences across habitats in predation environment, habituation, and/or the cost of retreating. Our study implicates changes in predator community composition in mediating ecological divergence in behaviour.

Diversity of culturable thermo-resistant aquatic bacteria along an environmental gradient in Cuatro Ciénegas, Coahuila, México

At the desert oasis of Cuatro Ciénegas in Coahuila, México, more than 300 oligotrophic pools can be found and a large number of endemic species of plants and animals. The most divergent taxa of diatoms, snail and fishes are located in the Churince hydrological system, where we analyzed the local diversification of cultivable Firmicutes and Actinobacteria. The Churince hydrological system is surrounded by gypsum dunes and has a strong gradient for salinity, temperature, pH and dissolved oxygen. In August 2003, surface water samples were taken in 10 sites along the Churince system together with the respective environmental measurements. 417 thermo-resistant bacteria were isolated and DNA was extracted to obtain their BOX-PCR fingerprints, revealing 55 different patterns. In order to identify similarities and differences in the diversity of the various sampling sites, an Ordination Analysis was applied using Principal Component Analysis. This analysis showed that conductivity is the environmental factor that explains the distribution of most of the microbial diversity. Phylogenetic reconstruction from their 16S rRNA sequences was performed for a sample of 150 isolates. Only 17 sequences had a 100% match in the Gene Bank (NCBI), representing 10 well known cosmopolitan taxa. The rest of the sequences cluster in 22 clades for Firmicutes and another 22 clades for Actinobacteria, supporting the idea of high diversity and differentiation for this site.

Molecular and functional basis of phenotypic convergence in white lizards at White Sands

There are many striking examples of phenotypic convergence in nature, in some cases associated with changes in the same genes. But even mutations in the same gene may have different biochemical properties and thus different evolutionary consequences. Here we dissect the molecular mechanism of convergent evolution in three lizard species with blanched coloration on the gypsum dunes of White Sands, New Mexico. These White Sands forms have rapidly evolved cryptic coloration in the last few thousand years, presumably to avoid predation. We use cell-based assays to demonstrate that independent mutations in the same gene underlie the convergent blanched phenotypes in two of the three species. Although the same gene contributes to light phenotypes in these White Sands populations, the specific molecular mechanisms leading to reduced melanin production are different. In one case, mutations affect receptor signaling and in the other, the ability of the receptor to integrate into the melanocyte membrane. These functional differences have important ramifications at the organismal level. Derived alleles in the two species show opposite dominance patterns, which in turn affect their visibility to selection and the spatial distribution of alleles across habitats. Our results demonstrate that even when the same gene is responsible for phenotypic convergence, differences in molecular mechanism can have dramatic consequences on trait expression and ultimately the adaptive trajectory.

Rapid divergence of social signal coloration across the White Sands ecotone for three lizard species under strong natural selection

Animal social signals are important for population recognition, communication, and mate choice. Although natural selection often favours cryptic coloration, sexual selection can underlie patterns of coloration that function in interor intrasexual communication. We compared social signal coloration of three lizard species across a substrate colour ecotone in New Mexico. These species exhibit cryptic blanched dorsal coloration on the gypsum dunes of White Sands and dark coloration on the surrounding desert soils. We detected corresponding population divergence in colour used for intra- (Aspidoscelis inornata, Sceloporus undulatus) or inter- (Holbrookia maculata) sexual signalling. Although the magnitude and direction of change in coloration varied among taxa, differences in hue and chroma accounted for more variation in social coloration than for dorsal coloration. The relative conspicuousness of social signals also varied across the ecotone. We discuss the possibilities that divergent signalling colours in this system are the result of: (1) stochastic processes, (2) direct selection, and/or (3) a correlated response to natural selection on dorsal coloration. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 243–255.