Desert-like Conditions Research Articles

Conditions and thermophysical properties for transport of hydrocarbons and natural gas at high pressures: Dense phase and anomalous supercritical state

Hydrocarbons and natural gas, like other fluids exhibit anomalous behavior in the vicinity of their critical points (Pc, Tc), where flow oscillations, thermal instabilities, and decreased heat transfer can occur. This work, based on Peng-Robinson equations of state, demonstrates that in the case of mixtures, the cricondenbar, cricondentherm, and a part of the dense phase belong to this anomalous region. Consequently, the most desirable conditions for the transport of supercritical natural gas (SNG) are: above the critical pressure and critical temperature, above the cricondenbar and cricondentherm, and beyond the anomalous state. For methane, such conditions exist at pressure, P > 5 MPa and temperature, T > - 30 °C whereas for average composition of natural gases from US/Canada, West Asia, and North Sea, P ≥ 6 MPa and T > −30 °C may be appropriate/safe for SNG transport. Corresponding gray zones which will require special design considerations are also identified. Reduced pressure, (P/Pc) of 1.15 and reduced temperature, (T/Tc) of 1.25 and 1.4 may be appropriate to delimit the Unsafe Zone/Gray Zone and Gray Zone/Safe zone. In addition, the specific volume and kinematic viscosity show asymptotic behavior at high SC pressures that can have important implications in the transport of hydrocarbons and natural gas. Moreover, the critical temperature, cricondentherm, and anomalous region of natural gas can be moved to lower temperatures by adding one or more modifier gases with low Tc, e.g., methane, nitrogen, and argon; or, higher using gases with high Tc such as ethane, propane, and carbon dioxide. The pipelines carrying SNG, with Tc-modifications if needed, can therefore pass through polar, tropical, arid, and desert-like conditions.

Diversity of dung beetle-associated yeasts from pristine environments of Botswana.

Yeast-insect interactions are increasingly becoming an attractive source of discovery for previously unknown, unique, diverse, and industrially relevant yeast species. Despite a wealth of studies that have recently focused on yeasts in symbiotic association with Hymenopteran insects, yeasts associated with Coleopteran insects, such as lignocellulosic-rich dung-dependent beetles, remain poorly studied. Trends in yeast discovery suggest that species richness and diversity can be attributed to the ecological niche of the insect. Here, we considered the potential of dung beetles inhabiting the extreme environments of Botswana, characterized by desert-like conditions (semi-arid to arid and hot) as well as protected pristine environments, as possible attribute niches that can shape the extremophilic and diverse life history strategies of yeasts. We obtained a total of 97 phylogenetically diverse yeast isolates from six species of dung beetles from Botswana's unexplored environments, representing 19 species belonging to 11 genera. The findings suggest that the guts of dung beetles are a rich niche for non-Saccharomyces yeast species. Meyerozyma and Pichia were the most dominant genera associated with dung beetles, representing 55% (53 out of 97) of the yeast isolates in our study. Trichosporon and Cutaneotrichosporon genera represented 32% (31 out of 97) of the isolates. The remaining isolates belonged to Apiotrichum, Candida, Diutina, Naganishia, Rhodotorula, and Wickerhamiella genera (12 out of 97). We found out that about 62% (60 out of 97) of the isolates were potentially new species because of their low internal transcribed spacer (ITS) sequence similarity when compared to the most recent optimal species delineation threshold. A single isolate was unidentifiable using the ITS sequences. Using an in silico polymerase chain reaction-restriction fragment length polymorphism approach, we revealed that there was genetic diversity within isolates of the same species. Our results contribute to the knowledge and understanding of the diversity of dung beetle-associated yeasts.

Remote Sensing and GIS tools for Forest Resource Management-A Review

Global importance and thus need to quantify the status of forest dynamics is increasing day by day. It is more so in the case of a country like India which is on the deficit side of forest cover in countering ecological balance. Information required for forest resource management includes extant, type of forest, felling/cutting, deforestation, afforestation, forest fire, forest flood, and extraction of bio-physical parameters like age of plantation, total biomass, canopy density etc. Widespread, vast span and difficult terrain, and inaccessibility makes it difficult to collect timely and periodic information about above mentioned parameter through conventional means. Forest mapping is one of the fields that witnessed the earliest application of remote sensing and GIS for nonmilitary purposes. using remote sensing data and GIS techniques, a forest manager can generate information regarding forest cover, types of forest present within an area of interest, human encroachment extent into forest land/protected areas, encroachment of desert-like conditions and so on [3].For the purpose of understanding the working of remote sensing and GIS, the basics are explained below.

Expanding the applicability of daytime radiative cooling: Technological developments and limitations

Daytime radiative cooling is regarded as the gold promise of future sustainable building energy systems and a breakthrough in the fight against local climate change. Despite the fervid research interest, most literature reports exceptional theoretical performances under ideal, desert-like conditions, but overlooks the cooling impairment that occurs under low atmospheric transparency (cloudy, humid, polluted conditions) and reduced sky access (packed urban contexts). Power recovery and stabilization call for decoupling of incoming and outgoing radiation at equal wavelengths. Enhanced directionality and high-contrast, broadband asymmetric transmission have been recently proposed to expand the applicability of radiative coolers over a wider spectrum of climates, weathers and terrains. This review offers itself as a first, timely synthesis of the current technological arena. Physical principles, materials and designs, collected from a variety of applicative fields, are detailed and discussed in terms of performance and feasibility, to inspire the transition into sustainable building cooling, worldwide. Major grey areas and serious concerns on potential violations of the 2nd law of thermodynamics reinforce the need for experimental demonstrations in future research.

Quantitative Assessment of Land Cover Sensitivity to Desertification in Maigatari Local Government Area, Jigawa State, Nigeria

Desertification alludes to land degradation in arid, semi-arid and sub-humid regions resulting from various variables, counting climatic variations and human activities. When land degradation transpire within the world’s drylands. It regularly makes desert-like conditions. Land degradation occurs all over, but is characterized as desertification when it occurs within the drylands. The study employed adjusted MEDALUS methodology using eleven indicators rainfall, evapotranspiration, aridity, soil texture, soil depth, slope gradient, drainage density, plant cover, erosion protection, sensitivity desertification index and Normalized Difference Vegetation Index (NDVI). Remote Sensing and GIS were the main techniques used in the indices computations and mapping. Thus, Shuttle Rader Topographic Map (SRTM) and Landsat 8 satellite imagery for the year 2019 with 30 meter resolution, captured in the month of August (rainy season), covering the study area were acquired from Global Land cover Facility (GLCF) University of Maryland. The study finds that the duration and intensity of rainfall is declining especially at the edge of the desert, extreme north and western part of the area. Rain quickly drained through infiltration and surface runoff which carried the little nutrients attached to the soil. Rainfall and climate is of arid type recording about 300-400mm of rainfall and the soil is low in organic matter content making it weak and less fertile and support only the cultivation of cereals and legumes. The study recommends that there is need to strengthen the laws and policies in controlling desertification and land degradation, establishment of shelterbelts to control desertification and act also as wind breakers and encourage the use of modern techniques such as drip irrigation to check the rate of infiltration and runoff. 
 Keyword: Desertification; Sensitivity; MEDALUS; GIS; Maigatari

Changes in surface water distribution in America's boomburbs

Boomburbs, or booming suburbs, represent rapid economic growth and urban sprawl, but this process typically requires a substantial redistribution of blue space (surface waters). In this study, the addition, modification, and removal of stream channels and inland surface waters were analyzed for 17 boomburbs, most located within the Sunbelt region of the U.S. Pre-development and present-day stream flowlines and inland lake/pond boundaries were digitized and edited off the earliest available, historical USGS 1: 24,000 scale topographic maps and from the National Hydrography Dataset Plus, High Resolution (NHDPlus, HR), respectively. Additionally, the count and distribution of residential pools provided data on the reallocation of surface water for four boomburbs. A total of 1145 km of stream channels were buried from all boomburbs, including more than 50% loss in several boomburbs, primarily due to centralizing surface runoff through a few major channels and canals. In contrast, lakes and ponds generally increased in areal extent over time (nearly 14 km2 of surface water added to the boomburbs during urbanization), as well as a substantial amount of surface water added for residential pools, including the equivalent of 1 km2 of additional surface water area in just one boomburb. This study illustrates a common practice of simplifying the urban stream network in desert-like conditions, while adding new waterbodies into the urban landscape to support housing development and recreational purposes. These boomburbs are only a fraction of sprawling metropolitan areas in the United States, but the overall demand for water in arid cities is high and requires unsustainable water management practices. Booming suburbs should reduce water reliance, rather than rely on water recycling, to prepare for a changing climate and relentless urbanization.

Scenario of poultry farming in high altitude region of India

During the last three decades, India has reached a level of self-sufficiency in chicken production, and the poultry industry has become more sophisticated, but the situation in the cold arid Himalayan part in India remains challenging. The main reasons for this condition are the non-existence of any commercial breeds or hatcheries, problems transporting day old chicks, poor availability of poultry feed ingredients and the fact that the majority of the population are Buddhist, and consequently largely vegetarian and generally avoid killing animals. There are varied climatic and topographic features are shows in the north western part of the Himalayan region of India. This area exhibits an extremely cold and dry climate for most of the year which hinders the growth and productivity of biomass. Vegetation cover is therefore very rare in these areas with the temperature falling to-30°C during winter and the altitude varies from 2000 to 3658 m from mean sea level (MSL). This type of cold, arid, desert-like conditions are not suited for natural habitat of poultry birds. At sea level, the oxygen concentration, barometric pressure, humidity and temperature should be 21%, 740 mm Hg, 65% and 99.8°F, respectively, however, in this cold desert area O2 concentration is 30% lower than at mean sea level, barometric pressure is only 510 mm Hg, humidity is less than 30% and temperature ranges from-30°C to +30°C. The objective of this review article is briefly described the problems, their solutions and opportunities for successful poultry farming in the high altitude cold arid region of India.

The disappearing desert and the emergence of agropastoralism: An adaptive cycle of rapid change in the mid-Holocene Lake Titicaca Basin (Peru–Bolivia)

The mid-Holocene was an extremely dry period in the Lake Titicaca Basin of South America, when lake levels were at their lowest point in the Holocene. South of the lake, a lack of outflow and very low and irregular precipitation would have created desert-like conditions. This area's ‘archaeological silence’ seems to reflect an effective lack of population. This situation changed drastically as lake levels rose suddenly in the centuries following 3540 cal BP. As the desert disappeared, a flux of migrants filled the landscape, probably from the population concentration in the basin's western highlands. They imported and developed new technologies and economic practices and reorganized them into an agropastoral lifeway. The emergence of agropastoralism was both rapid and widespread, as people throughout the Lake Titicaca Basin adopted this practice. This major, regional shift can be productively framed as an adaptive cycle or Holling loop. This approach builds on the robust foundation of complexity theory, emphasizes the integrated nature of humans and their environment in a single system, highlights how systems fluctuate between slow and accelerated change, and is useful for developing hypotheses. Cascading feedback loops in climate, ecology, and cultural practices generated the emergence of agropastoralism. This resilient system is still in use today and is currently facing major climate changes, which makes understanding its origins especially relevant.

Stable isotopes of lead and strontium as tracers of sources of airborne particulate matter in Kyrgyzstan

Central Asia is dominated by an arid climate and desert-like conditions, leading to the potential for long-range transport of desert dust within and out of the region. Of particular interest is the Aral Sea, which has receded in size largely due to water diversion. As a result, newly exposed sediments are resuspended by wind and thus, may be a potential new source of particulate matter within the region. Here, strontium and lead stable isotope ratios are employed along with detailed elemental composition, to explore the contribution of long-range transport of Aral Sea sediments, as well as other potential sources of dust, within Central Asia. Ambient PM10 samples were collected during dust and non-dust events from mid-2008 to mid-2009 at two sites in Kyrgyzstan located ∼1200 and 1500 km ESE of the Aral Sea. Aral Sea sediments and local Kyrgyzstan soils were resuspended and sized to PM10. The Aral Sea sediments have an average 87Sr/86Sr ratio of 0.70992. In contrast, the Sr isotope ratio in local soils exhibits an average ratio of 0.71579. Ambient PM10 collected in Kyrgyzstan has an average 87Sr/86Sr ratio of 0.71177, falling between the values of these two potential sources and indicating a complex mixture of contributing sources. At both sites, airborne Sr isotope ratios measured during dust events were similar, suggesting that Aral Sea sediments only minimally affect air quality in Kyrgyzstan. Elemental analysis and Pb isotope ratios supported this finding. While the Pb isotopes and elemental data both indicate an anthropogenic source, long-range dust transport from other deserts inside and outside the region cannot be ruled out as sources of PM10 in Central Asia.

Heteroskedasticity as a leading indicator of desertification in spatially explicit data

Regime shifts are abrupt transitions between alternate ecosystem states including desertification in arid regions due to drought or overgrazing. Regime shifts may be preceded by statistical anomalies such as increased autocorrelation, indicating declining resilience and warning of an impending shift. Tests for conditional heteroskedasticity, a type of clustered variance, have proven powerful leading indicators for regime shifts in time series data, but an analogous indicator for spatial data has not been evaluated. A spatial analog for conditional heteroskedasticity might be especially useful in arid environments where spatial interactions are critical in structuring ecosystem pattern and process. We tested the efficacy of a test for spatial heteroskedasticity as a leading indicator of regime shifts with simulated data from spatially extended vegetation models with regular and scale-free patterning. These models simulate shifts from extensive vegetative cover to bare, desert-like conditions. The magnitude of spatial heteroskedasticity increased consistently as the modeled systems approached a regime shift from vegetated to desert state. Relative spatial autocorrelation, spatial heteroskedasticity increased earlier and more consistently. We conclude that tests for spatial heteroskedasticity can contribute to the growing toolbox of early warning indicators for regime shifts analyzed with spatially explicit data.

Cooling Mediterranean Sea surface temperatures during the Late Miocene provide a climate context for evolutionary transitions in Africa and Eurasia

In the Late Miocene, grasslands proliferated, succulent plants diversified in the mid-latitudes, and the desert-like conditions appeared in the Sahara. Despite this major environmental change on land, the coeval deep-sea oxygen isotope record does not provide evidence for significant high latitude cooling or continental ice growth, making it difficult to relate widespread terrestrial environmental change to global climatic changes. A U37K′ –derived sea surface temperature (SST) reconstruction spanning 13 to 6 Ma from uplifted hemipelagic sediments in Northern Italy provides the first continuous mid-latitude temperature record with which to compare the evolution of aridity and biotic events at similar latitudes in Northern Africa and Pakistan. Between 13 and 8.8 Ma, Mediterranean SST lay near the upper limit of the alkenone temperature proxy (∼28 °C), exceeding modern SST at the site by as much as 10 °C. Throughout the record, sapropel layers correspond to local SST maxima, suggesting that Late Miocene hydrological conditions in the Mediterranean responded to insolation forcing via mechanisms similar to those documented for the Plio-Pleistocene. Mediterranean SST cooled rapidly beginning at ∼8 Ma, with an episode of intense cooling to ∼19 °C between 7.2 Ma and 6.6 Ma, followed by a rebound to ∼25 °C preceding the Messinian Salinity Crisis at 5.9 Ma. These observations establish, for the first time, a direct relationship between increasing aridity in the Northern hemisphere mid-latitudes and significant cooling. Evidently, this cooling was not accompanied by significant growth in continental ice volume. The extreme warmth and subsequent cooling of the Mediterranean Sea are not well-represented in current Late Miocene climate models, which our results suggest underestimate regional warmth prior to the Late Miocene cooling. Evidence of secular cooling during the Late Miocene gives new support to the much-debated link between a possible decline in atmospheric CO2 levels and Late Miocene changes in vegetation on land.

Integrated remote sensing investigations of ancient quarries and road systems in the Greater Dayr al-Barshā Region, Middle Egypt: a study of logistics

Although the study of stone quarries is gaining increasing importance in Egyptian archaeology, quarry logistics, particularly as concerns transport facilities, has hitherto hardly been investigated. In the case of the quarry roads in the greater Dayr al-Barshā region (Middle Egypt), distinguishing between roads related to quarry exploitation from those resulting from other periods of use (in this case mainly related to funerary cult and Late Antique–Early Islamic Period monastic communities) poses another methodological problem. In this paper the use of very high spatial resolution satellite (VHSRS) technology is combined with archaeological methods to investigate the interplay between limestone quarries and roads in the study region. Remote sensing affords significant advantages over traditional survey techniques by visualizing the spatial context, whereas the spectral information content of the imagery adds information on road characteristics.Results indicate that spectral content is of less importance for road detection in desert-like conditions than the spatial resolution of the imagery. Filtering techniques have an additional value, but in general enhancement techniques such as histogram equalization are most important for mapping road networks in the greater Dayr al-Barshā region. Based on spectral and morphological characteristics, six road types could be identified, a seventh being located using traditional techniques. Ground verification in conjunction with archaeological evidence clarified the spatial context and functions of the routes in the pharaonic and later periods, serving cemetery, quarry and settlement logistics.Apart from one Middle Kingdom processional road, most roads have their origin in New Kingdom quarry activities. The road pattern we discovered provides important indications on how the stone transport was organized in a practical way. Many quarries in Dayr Abū Ḥinnis were not connected to harbours along the Nile, but to a long desert road that facilitated talatat transport to an area in northern Amarna. When the abandoned quarry complexes were turned into settlements in the Late Antique–Early Islamic Period, the resident communities selected parts of the existing road system for inter-site transport and transport from and to the Nile Valley. New paths were only rarely developed.These observations demonstrate that remote sensing techniques hold great potential for surveying road patterns over large distance in desert-like conditions.

Case Study

While most motor vehicle operators must obtain a driver’s license, which requires training and a test, child operators of motorized dirt bikes can use these vehicles without any training or experience. In this case, a 10-year-old boy was riding a dirt bike in the desert for the first time. The area where he was riding had desert-like sand and dune conditions on both sides of a 2-lane highway. The boy received some oral instructions from a family friend, and then spent a few hours riding in the dirt. Towards the end of the day, an off-duty ambulance was driving down the highway. The child stopped at the side of the road, looked towards the ambulance, which was the only vehicle on the road in either direction, and then proceeded to cross, clearing the roadway. The ambulance driver panicked, left the road and struck the dirt bike 30 feet off the side of the road in the dirt. The boy suffered a traumatic brain injury with permanent brain damage. Human factors issues from both motor vehicle operators’ perspectives will be discussed.

The vertebrate fauna of the Upper Permian of Niger—VII. Cranial anatomy and relationships of Bunostegos akokanensis (Pareiasauria)

ABSTRACT We describe newly recovered cranial material of Bunostegos akokanensis, a pareiasaurian reptile known from the Upper Permian Moradi Formation of northern Niger. Bunostegos is highly autapomorphic, with diagnostic cranial features including two or three hemispherical bosses located above and between the external nares; laterally projecting supraorbital ‘horn’ formed by an enlarged postfrontal; large foramen present on ventral surface of postfrontal; and hemispherical supratemporal boss located at posterolateral corner of skull roof. We addressed the phylogenetic position of Bunostegos by incorporating it into a cladistic analysis of 29 parareptilian taxa (including all 21 currently valid pareiasaurs) and 127 cranial and postcranial characters. The results of this analysis place Bunostegos as more derived than middle Permian forms such as Bradysaurus and as the sister taxon to the clade including Deltavjatia plus Velosauria. Certain characters, such as the pattern of cranial ornamentation and the size and placement of the tabulars, appear to be more similar to more derived pareiasaurs such as Elginia from Scotland and Arganaceras from Morocco, but the most parsimonious tree topology indicates that these features were evolved independently in the Nigerien form. The lack of both dicynodont herbivores and Glossopteris, combined with the presence of a giant herbivorous captorhinid, indicates a markedly different community structure in the Permian of Niger compared with those for contemporaneous southern Pangean basins (i.e., Karoo, Luangwa, Ruhuhu). The endemic tetrapod fauna of Niger supports the theory that central Pangea was biogeographically isolated from the rest of the supercontinent by desert-like conditions during Late Permian times. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Global desertification: Drivers and feedbacks

Desertification is a change in soil properties, vegetation or climate, which results in a persistent loss of ecosystem services that are fundamental to sustaining life. Desertification affects large dryland areas around the world and is a major cause of stress in human societies. Here we review recent research on the drivers, feedbacks, and impacts of desertification. A multidisciplinary approach to understanding the drivers and feedbacks of global desertification is motivated by our increasing need to improve global food production and to sustainably manage ecosystems in the context of climate change. Classic desertification theories look at this process as a transition between stable states in bistable ecosystem dynamics. Climate change (i.e., aridification) and land use dynamics are the major drivers of an ecosystem shift to a “desertified” (or “degraded”) state. This shift is typically sustained by positive feedbacks, which stabilize the system in the new state. Desertification feedbacks may involve land degradation processes (e.g., nutrient loss or salinization), changes in rainfall regime resulting from land-atmosphere interactions (e.g., precipitation recycling, dust emissions), or changes in plant community composition (e.g., shrub encroachment, decrease in vegetation cover). We analyze each of these feedback mechanisms and discuss their possible enhancement by interactions with socio-economic drivers. Large scale effects of desertification include the emigration of “environmental refugees” displaced from degraded areas, climatic changes, and the alteration of global biogeochemical cycles resulting from the emission and long-range transport of fine mineral dust. Recent research has identified some possible early warning signs of desertification, which can be used as indicators of resilience loss and imminent shift to desert-like conditions. We conclude with a brief discussion on some desertification control strategies implemented in different regions around the world.

Foraging behavior of heritage versus recently introduced herbivores on desert landscapes of the American Southwest

Since the 1800s managed grasslands and shrublands of the arid American Southwest have been grazed predominantly by cattle originally bred for temperate climates in northern Europe. A heritage breed, the criollo cattle, has survived in northern Mexico for more than 400 years under desert-like conditions of low and variable rainfall, hot temperatures in the growing season, and both spatially and temporally scarce levels of primary production. We tested the hypothesis that the heritage breed has a broader spatial foraging distribution under harsh environmental conditions, and that its distribution is driven by environmental variables which differ from those that control the distribution of the introduced European breed. Movements of individual criollo and Angus breed animals were monitored autonomously in the northern Chihuahuan desert of southern New Mexico, USA. Georeferenced foraging locations acquired at 5-minute intervals for each animal were fit to a logistic regression using environmental factors as p...

Does Supply-Induced Scarcity Drive Violent Conflicts in the African Sahel? The Case of the Tuareg Rebellion in Northern Mali

According to the influential `environmental security' literature, supply-induced scarcity in the form of environmental degradation is a key driver of civil violence around the world. African drylands, especially the Sahel region, are allegedly among the areas most seriously affected by this development. Views of desertification and severe environmental degradation in the Sahel are held by environmental security scholars, despite the comprehensive literature questioning such ideas that has been published since the late 1980s. Instead of being steadily transformed towards more desert-like conditions through increasing population pressure, Sahelian environments are dominated by climatic fluctuations. This article first reviews the literature criticizing the idea of `desertification' as it is applied on African drylands. Then, the article critically discusses the use of the Tuareg rebellion in northern Mali as an example of a supply-induced scarcity related conflict. The case study shows that the droughts of the 1970s and 1980s played a role in the rebellion, but the rebellion was not driven by supply-induced scarcity. Instead, the droughts led to the migration of young men to Algeria and Libya, where they were exposed to revolutionary discourses. There was already a strong feeling among nomads and Tuareg in Mali of being marginalized by state policies of modernization and sedentarization. Embezzlement of drought relief funds by government officials in Bamako added further to the anger felt by the young men who took up arms against the Malian state. The drought of the 1970s and 1980s was probably not a necessary condition for the rebellion to take place. Detailed case studies of armed conflicts, engaging with environmental research, may be necessary to further deepen our understanding of links, or lack of such links, between violence and environmental stress.

A Mössbauer spectroscopic study of simulated weathering of Didwana ordinary chondrites

A sample of an ordinary chondrite fall, Didwana-Rajod, Rajasthan, India which was shown to be largely unweathered, was exposed to weathering in laboratory conditions. Wet and dry cycle of different strengths (0.01 and 0.1 M) of sodium sulfate solution was applied for different periods of time (maximum of 140 days). An attempt was made to simulate meteorite weathering more or less analogous to environmental exposure in desert-like conditions. It is found that lower concentration of the attacking ions is more effective in weathering the meteorite. Kamacite is affected in early cycles of weathering more than any other mineral. The olivine to pyroxene ratio is much less affected.

Editorial and Retrospective 2008

Editorial and Retrospective 2008

Molecular Adaptation during Adaptive Radiation in the Hawaiian Endemic Genus Schiedea

Background“Explosive” adaptive radiations on islands remain one of the most puzzling evolutionary phenomena. The rate of phenotypic and ecological adaptations is extremely fast during such events, suggesting that many genes may be under fairly strong selection. However, no evidence for adaptation at the level of protein coding genes was found, so it has been suggested that selection may work mainly on regulatory elements. Here we report the first evidence that positive selection does operate at the level of protein coding genes during rapid adaptive radiations. We studied molecular adaptation in Hawaiian endemic plant genus Schiedea (Caryophyllaceae), which includes closely related species with a striking range of morphological and ecological forms, varying from rainforest vines to woody shrubs growing in desert-like conditions on cliffs. Given the remarkable difference in photosynthetic performance between Schiedea species from different habitats, we focused on the “photosynthetic” Rubisco enzyme, the efficiency of which is known to be a limiting step in plant photosynthesis.ResultsWe demonstrate that the chloroplast rbcL gene, encoding the large subunit of Rubisco enzyme, evolved under strong positive selection in Schiedea. Adaptive amino acid changes occurred in functionally important regions of Rubisco that interact with Rubisco activase, a chaperone which promotes and maintains the catalytic activity of Rubisco. Interestingly, positive selection acting on the rbcL might have caused favorable cytotypes to spread across several Schiedea species.SignificanceWe report the first evidence for adaptive changes at the DNA and protein sequence level that may have been associated with the evolution of photosynthetic performance and colonization of new habitats during a recent adaptive radiation in an island plant genus. This illustrates how small changes at the molecular level may change ecological species performance and helps us to understand the molecular bases of extremely fast rate of adaptation during island adaptive radiations.