Dunes Sagebrush Lizard Research Articles

Lessons learned from a conservation translocation of a microendemic habitat specialist

Translocations are often characterized as “successes” or “failures”. However, this dichotomy masks the challenges of successful translocations and ignores important lessons learned in cases where a population was not established in perpetuity. We translocated 76 individuals of an imperiled endemic lizard, the Dunes Sagebrush Lizard (Sceloporus arenicolus), to a locality where it had gone extinct. Translocated lizards survived and reproduced in small numbers. Based on intensive monitoring, we were able to conclude the incipient population declined to zero individuals after 4 years. It is possible that predation, Allee effects, or stochastic factors prevented the population from sustaining itself at this historically occupied site. Valuable lessons for conservation translocations can be taken from this case. We offer novel perspectives on the IUCN Guidelines for Reintroductions and Other Conservation Translocations regarding release site selection, propagule bias, behavioral monitoring, population monitoring, and issues of land tenure. We recommend pairing knowledge of habitat requirements with quantitative analyses to select suitable release sites, translocating gravid females to jump‐start population growth, coupling delayed releases with intensive behavioral monitoring, using Poisson‐based models to determine necessary intensity of monitoring, and recognizing how issues of land tenure may present pitfalls for conservation translocations in the long term.

Supporting habitat conservation with automated change detection in Google Earth Engine.

A significant limitation in biodiversity conservation has been the effective implementation of laws and regulations that protect species' habitats from degradation. Flexible, efficient, and effective monitoring and enforcement methods are needed to help conservation policies realize their full benefit. As remote sensing data become more numerous and accessible, they can be used to identify and quantify land-cover changes and habitat loss. However, these data remain underused for systematic conservation monitoring in part because of a lack of simple tools. We adapted 2 algorithms that automatically identify differences between pairs of images. We used free, publicly available satellite data to evaluate their ability to rapidly detect land-cover changes in a variety of land-cover types. We compared algorithm predictions with ground-truthed results at 100 sites of known change in the United States. We also compared algorithm predictions to manually created polygons delineating anthropogenic change in 4 case studies involving imperiled species' habitat: oil and gas development in the range of the Greater Sage Grouse (Centrocercus urophasianus); sand mining operations in the range of the dunes sagebrush lizard (Sceloporus arenicolus); loss of Piping Plover (Charadrius melodus) coastal habitat after Hurricane Michael (2018); and residential development in St. Andrew beach mouse (Peromyscus polionotus peninsularis) habitat. Both algorithms effectively discriminated between pixels corresponding to land-cover change and unchanged pixels as indicated by area under a receiver operating characteristic curve >0.90. The algorithm that was most effective differed among the case-study habitat types, and both effectively delineated habitat loss as indicated by low omission (min. = 0.0) and commission (min. = 0.0) rates, and moderate polygon overlap (max. = 47%). Our results showed how these algorithms can be used to help close the implementation gap of monitoring and enforcement in biodiversity conservation. We provide a free online tool that can be used to run these analyses (https://conservationist.io/habitatpatrol).

Phylogeographic structure of the dunes sagebrush lizard, an endemic habitat specialist.

Phylogeographic divergence and population genetic diversity within species reflect the impacts of habitat connectivity, demographics, and landscape level processes in both the recent and distant past. Characterizing patterns of differentiation across the geographic range of a species provides insight on the roles of organismal and environmental traits in evolutionary divergence and future population persistence. This is particularly true of habitat specialists where habitat availability and resource dependence may result in pronounced genetic structure as well as increased population vulnerability. We use DNA sequence data as well as microsatellite genotypes to estimate range-wide phylogeographic divergence, historical population connectivity, and historical demographics in an endemic habitat specialist, the dunes sagebrush lizard (Sceloporus arenicolus). This species is found exclusively in dune blowouts and patches of open sand within the shinnery oak-sand dune ecosystem of southeastern New Mexico and adjacent Texas. We find evidence of phylogeographic structure consistent with breaks and constrictions in suitable habitat at the range-wide scale. In addition, we find support for a dynamic and variable evolutionary history across the range of S. arenicolus. Populations in the Monahans Sandhills have deeply divergent lineages consistent with long-term demographic stability. In contrast, populations in the Mescalero Sands are not highly differentiated, though we do find evidence of demographic expansion in some regions and relative demographic stability in others. Phylogeographic history and population genetic differentiation in this species has been shaped by the configuration of habitat patches within a geologically complex and historically dynamic landscape. Our findings identify regions as genetically distinctive conservation units as well as underscore the genetic and demographic history of different lineages of S. arenicolus.

From the ground up: microhabitat use within a landscape context frames the spatiotemporal scale of settlement and vacancy dynamics in an endemic habitat specialist

Understanding how species are distributed throughout landscapes requires knowledge of the hierarchy of habitat selection made by individuals, the resulting spatiotemporal structure of demography, and the consequent dynamics of localized populations. We examined how patterns of habitat use, settlement, and vacancy in an endemic habitat specialist, Sceloporus arenicolus (dunes sagebrush lizard), varied within the Mescalero Monahans Sandhills ecosystem. We used a 4-year mark-recapture dataset to develop occupancy models that identified whether microhabitat or landscape scale best predicted S. arenicolus spatiotemporal habitat use, settlement, and vacancy, in both an undisturbed and disturbed landscape. Our results showed areas of high quality habitat were used constantly and lower quality areas were used intermittently, but repeatedly, over time in the undisturbed landscape. Habitat use in the disturbed landscape was spatiotemporally unpredictable. Microhabitat variables characterizing dune landscape topography predicted probability of use in S. arenicolus, while landscape-scale variables predicted probabilities of settlement and vacancy. In the undisturbed landscape, future settlement was predicted by presence of S. arenicolus, a pattern consistent with fine-scale source-sink dynamics already described for this species. Our results illustrate how spatially-discrete but temporally-linked areas should be conserved at fine spatiotemporal scales to secure persistence of S. arenicolus populations under variable environmental conditions. Disturbances to habitat continuity can disrupt individual movements and create inconsistently occupied habitat patches that appear to be unoccupied and thus are threatened by further disturbances.

LOGGERHEAD SHRIKE PREDATION ON DUNE-DWELLING LIZARDS AND NESTING SUCCESS IN SOUTHEASTERN NEW MEXICO

Predation of dunes sagebrush lizards (Sceloporus arenicolus) by loggerhead shrikes (Lanius ludovicianus) is not well-understood. The goal of this project was to determine if the frequency of dunes sagebrush lizards as prey by loggerhead shrikes was greater in areas that were fragmented by oil and gas development compared with unfragmented habitat. We deployed motion-activated game cameras at shrike nests to determine what prey was being fed at the nests, we quantified the amount of time shrikes spent hunting from power lines or other anthropogenic perches, and we collected shrike pellets to look for the presence of dunes sagebrush lizard scales. Camera data results indicate that lizards make up approximately 10% of the prey items that loggerhead shrikes take to the nest. The difference in overall lizard captures between fragmented and unfragmented habitat was not statistically significant. Power-line survey results indicate that loggerhead shrikes hunt from anthropogenic perches approximately 50% of the time. The analysis of camera-trap images allowed us to identify two individual dunes sagebrush lizards, each from a nest in fragmented habitat, and the pellet analysis documented one instance in unfragmented habitat. An opportunistic finding in a shrike food larder in unfragmented habitat documented six additional dunes sagebrush lizards that were impaled on barbed wire. These results indicate that loggerhead shrikes do sometimes predate dunes sagebrush lizards, although samples sizes were too small to determine predation rates between the habitat types.

Bias and Precision of Lizard Occupancy Estimates Vary among Observers and between Methods

Heterogeneity in detection probabilities arises from many parts of a survey design and can introduce bias into estimates of site occupancy probability. We examined the effect of two important sources of heterogeneity, observer and survey method, on occupancy estimates in a lizard community in west Texas, with a special emphasis on Dunes Sagebrush Lizard (Sceloporus arenicolus). Using line transects and visual encounter surveys, nine observers surveyed 72 sites. We detected 10 species of lizards in total; all 10 were detected using visual encounter surveys and only 4 were detected using transects. We determined observers to be an important variable in occupancy models for two of three species of lizards. Insufficient detections were made of the remaining seven species to reliably model occupancy. We conducted simulations to further investigate the impacts of observer variability on occupancy estimate bias and precision by using a range of known occupancy and detectability combinations. Precision in the occupancy estimate increased as the mean observer detection probability increased. Overall, bias was minimized by conducting surveys with either 1) observers with high detection probabilities or 2) using teams of observers with mixed (high and low) detection probabilities.Modeling observer detection probabilities explicitly provided marginal improvement to the occupancy estimate in the simulations. The consistent variability in detection probability among observers has implications for the precision and bias in occupancy estimates and decisions should be made at the experimental design phase about how to approach this problem.

Fragmentation alters home range and movements of the Dunes Sagebrush Lizard (Sceloporusarenicolus)

Habitat fragmentation is a major driver of biodiversity loss and among reptiles has been attributed as a cause of species decline. The negative effect of habitat fragmentation has also been shown to be worse for species that are habitat specialists. The Dunes Sagebrush Lizard (Sceloporus arenicolus Degenhardt and Jones, 1972) is a species that specializes on the shinnery oak (Quercus havardii Rydb.) sand-dune landform of the Mescalero–Monahans Sandhills ecosystem in western Texas and eastern New Mexico, USA. This landform has been fragmented by roads and well pads used for the extraction of oil and gas resources. The effects of fragmentation on the home range and movements of this species can lead to the effective isolation of populations and increased risk of localized extirpations. We showed that home-range size was larger in an unfragmented area and that the mean distance of movements was greater. We also observed that roads in the fragmented areas restricted movements of S. arenicolus. We concluded that roads can be barriers to movements even though only narrow strips of habitat are altered.

The Texas Conservation Plan has not slowed oil and gas well development in dunes sagebrush lizard habitat

Background: The dunes sagebrush lizard (Sceloporus arenicolus) is an imperiled species that is restricted to shinnery oak (Quercus havardii) sand dune habitats in southeastern New Mexico and West Texas, USA. This region is also a hotspot of oil and gas development that is a major threat to the species. Methods: Here we use well data and a natural experiment to test the effectiveness of voluntary conservation agreements for slowing or stopping oil and gas well approval in the lizard’s habitat in New Mexico and Texas. Results: We show that the Candidate Conservation Agreement (CCA) and CCA with Assurances in New Mexico, both of which contain strong avoidance mechanisms, are associated with a steep decline in oil and gas well approval in the New Mexico portion of the lizard’s range, but not outside the lizard’s range. By contrast, the Texas Conservation Plan (TCP), which does not include mandatory avoidance, is not associated with any decline of oil and gas well approval in the lizard's Texas range relative to the broader landscape. Conclusions: These results indicate that the TCP is insufficient to conserve the lizard in Texas, thereby jeopardizing genetic and geographic representation across the range of the species.

Effects of habitat fragmentation on population structure of dune‐dwelling lizards

AbstractLandscape fragmentation alters biotic and abiotic characteristics of landscapes, variously affecting the size and demographic structure of species' populations. Fragmentation is predicted to negatively impact habitat specialists because of perturbations to their habitat, whereas generalists should be less sensitive to fragmentation. Differences in life history among the lizards in this community should partly explain some of the variation in generalist species' responses to fragmentation. During five seasons (2009–2013), we captured eight species of lizards on 27 independent trapping grids located in unfragmented (N = 18) and fragmented (N = 9) grids in the Mescalero‐Monahans Sandhills ecosystem in southeastern New Mexico. Using a two‐way ANOVA, we tested for effects of fragmentation and year on capture rates for each species. To test for effects of fragmentation on demographic structure, we used contingency tables with expected frequencies computed from the demographic structure on unfragmented grids. Capture rates of the endemic habitat specialist Sceloporus arenicolus (dunes sagebrush lizard) decreased to zero in fragmented sites. The demographic structure of S. arenicolus and Holbrookia maculata (common lesser earless lizard) was severely disrupted at fragmented sites, with proportions of juveniles, adult males, or adult females being over‐ or underrepresented during sample months. Variable responses of five generalist species could be attributed to life history patterns, habitat affinity, and breeding phenology. This is the first empirical study we are aware of that describes and quantifies the demographic effects of fragmentation on populations of multiple lizard species in a replicated study. Our findings lend important insights into how habitat specialization and differences in life history influence the susceptibility of species to the impacts of fragmentation.

Why didn't the lizard cross the road? Dunes sagebrush lizards exhibit road-avoidance behaviour

Context Research has shown many negative effects of roads and traffic on wildlife and other biodiversity. The direct and indirect mechanisms through which roads and traffic harm animal populations vary across taxa, making mitigation of road effects a great challenge for conservation. As such, a large toolkit of species-specific management techniques may be needed to mitigate the negative effects of roads for wildlife and other biodiversity. The dunes sagebrush lizard, Sceloporus arenicolus, is a psammophilic (sand-loving) habitat specialist endemic to the Mescalero–Monahans Sandhills ecosystem of New Mexico and Texas. Within this ecosystem, roads fragment shinnery oak sand-dune landforms occupied by the species. Aims In the present study, we conducted behaviour trials in experimental enclosures to test whether the smallest roads restrict movements of the dunes sagebrush lizard. In addition, we also conducted trials to evaluate whether a sand-filled wildlife-crossing feature could facilitate road crossing. Methods We conducted behavioural trials on 24 dunes sagebrush lizards in our control enclosure and 22 lizards in our road and sand-filled wildlife-crossing enclosure. Movements were recorded for 15min. The final locations at the end of each trial were analysed using circular statistics to determine whether movements in the road or the sand-filled wildlife-crossing enclosures were different from the control. Key results Our results supported the hypotheses that dunes sagebrush lizards avoid roads and do so according to a surface-avoidance mechanism. We also found that the wildlife crossing-feature design tested here had no effect on the movements or road-crossing frequency of dunes sagebrush lizard. Conclusions Surface-avoidance behaviour indicated that roads will persistently affect the movements of dunes sagebrush lizard, even when traffic is not present. Also, more research into an effective wildlife crossing is needed to increase connectivity of fragmented populations. Implications These findings help evaluate the impact of roads in creating isolated populations that experience increased demographic stochasticity and, in some instances, localised extirpation in this species. Our study can guide conservation plans for the dunes sagebrush lizard, and contribute to our understanding of road effects on biodiversity in general.

Conservation Credits—Evolution of a Market-Oriented Approach to Recovery of Species of Concern on Private Land

When species are listed as threatened or endangered under the Endangered Species Act, there are often real or perceived negative consequences for landowners that may produce perverse incentives and lead to the elimination rather than protection of habitat for the species on private land. In Texas, where approximately 95% of the land is privately owned, the listing of one species and the potential listing of another led to the creation of two innovative programs aimed at incentivizing landowners to protect and improve habitat for the two species: Recovery Credit System for the Golden-Cheeked Warbler and Conservation Recovery Award System for the Dunes Sagebrush Lizard. Both programs were based on multistakeholder collaborations that included federal and state agencies, nongovernmental organizations, and private landowners, and which resulted in quasimarket mechanisms for the voluntary protection of habitat by landowners for the species of concern. Key components of both programs included confidentiality of landowner conservation agreements with the state’s wildlife management agency and the creation of not-for profit organizations to implement contracts with landowners and disseminate payments for habitat conservation actions to landowners. These two programs have also informed efforts to protect the Lesser Prairie-Chicken and Greater Sage-Grouse, which are under threat on private land in multiple states. Seven lessons learned from protection programs for the four species presented in this article provide useful guidelines for the conservation of other at-risk species on private land elsewhere.

Direct and indirect effects of petroleum production activities on the western fence lizard (Sceloporus occidentalis) as a surrogate for the dunes sagebrush lizard (Sceloporus arenicolus).

The dunes sagebrush lizard (Sceloporus arenicolus) is a habitat specialist of conservation concern limited to shin oak sand dune systems of New Mexico and Texas (USA). Because much of the dunes sagebrush lizard's habitat occurs in areas of high oil and gas production, there may be direct and indirect effects of these activities. The congeneric Western fence lizard (Sceloporus occidentalis) was used as a surrogate species to determine direct effects of 2 contaminants associated with oil and gas drilling activities in the Permian Basin (NM and TX, USA): herbicide formulations (Krovar and Quest) and hydrogen sulfide gas (H2S). Lizards were exposed to 2 concentrations of H2 S (30 ppm or 90 ppm) and herbicide formulations (1× or 2× label application rate) representing high-end exposure scenarios. Sublethal behavioral endpoints were evaluated, including sprint speed and time to prey detection and capture. Neither H2S nor herbicide formulations caused significant behavioral effects compared to controls. To understand potential indirect effects of oil and gas drilling on the prey base, terrestrial invertebrate biomass and order diversity were quantified at impacted sites to compare with nonimpacted sites. A significant decrease in biomass was found at impacted sites, but no significant effects on diversity. The results suggest little risk from direct toxic effects, but the potential for indirect effects should be further explored.

Linking irreplaceable landforms in a self-organizing landscape to sensitivity of population vital rates for an ecological specialist.

Irreplaceable, self-organizing landforms and the endemic and ecologically specialized biodiversity they support are threatened globally by anthropogenic disturbances. Although the outcome of disrupting landforms is somewhat understood, little information exists that documents population consequences of landform disturbance on endemic biodiversity. Conservation strategies for species dependent upon landforms have been difficult to devise because they require understanding complex feedbacks that create and maintain landforms and the consequences of landform configuration on demography of species. We characterized and quantified links between landform configuration and demography of an ecological specialist, the dunes sagebrush lizard (Sceloporus arenicolus), which occurs only in blowouts (i.e., wind-blown sandy depressions) of Shinnery oak (Quercus havardii) sand-dune landforms. We used matrix models to estimate vital rates from a multisite mark-recapture study of 6 populations occupying landforms with different spatial configurations. Sensitivity and elasticity analyses demonstrated demographic rates among populations varied in sensitivity to different landform configurations. Specifically, significant relationships between blowout shape complexity and vital rate elasticities suggested direct links between S. arenicolus demography and amount of edge in Shinnery oak sand-dune landforms. These landforms are irreplaceable, based on permanent transition of disturbed areas to alternative grassland ecosystem states. Additionally, complex feedbacks between wind, sand, and Shinnery oak maintain this landform, indicating restoration through land management practices is unlikely. Our findings that S. arenicolus population dynamics depended on landform configuration suggest that failure to consider processes of landform organization and their effects on species' population dynamics may lead to incorrect inferences about threats to endemic species and ineffective habitat management for threatened or endangered species. As such, successful conservation of these systems and the biodiversity they support must be informed by research linking process-oriented studies of self-organized landforms with studies of movement, behavior, and demography of species that dwell in them.

Sand grain size composition influences subsurface oxygen diffusion and distribution of an endemic, psammophilic lizard

AbstractReptile species endemic to dune ecosystems worldwide possess morphological and behavioral adaptations for burying in sand. Specializations for burying and subsurface breathing among these animals are advantageous only where sand conditions permit. The patchy distributions of many psammophilic species are presumably due to the occurrence of suitable areas where attributes of the sand facilitate locomotion, burying, subsurface breathing and nesting. The endemic, dune‐dwelling Sceloporus arenicolus does not occur in areas where sand grain size composition is relatively fine, and the distribution of the species appears limited to areas with coarse‐grained sand. However, the exact mechanism by which this occurs is unknown. We hypothesized that subsurface breathing is inhibited in fine sand, and tested the prediction that fine sand restricts diffusion of oxygen. We compared oxygen diffusion rates in sand with grain size compositions matching sites where S. arenicolus was present (coarse sand) to diffusion rates in samples from sites where it was absent (fine sand). We found that samples with relatively coarse sand from sites where S. arenicolus was present had higher oxygen diffusion rates than samples with finer sand where S. arenicolus was absent. These results corroborated our prediction and support the hypothesis that subsurface breathing by S. arenicolus is constrained by fine sand. This is the first step in a line of research on the role of sand grain size composition in the life history of dune‐dwelling reptiles and more experiments can build on this study. Our results have broad implications for the conservation of all strictly psammophilic species by improving our understanding of the habitat elements necessary for their survival and persistence.

Daily and Seasonal Patterns of Natural Ultraviolet Light Exposure of the Western Sagebrush Lizard (Sceloporus graciosus gracilis) and the Dunes Sagebrush Lizard (Sceloporus arenicolus)

Abstract: We monitored ultraviolet-B (UVB) irradiance exposure (measured using the ultraviolet index [UVI]) of the Western Sagebrush Lizard (Sceloporus graciosus gracilis) in Lassen Volcanic National Park, California, and the related Dunes Sagebrush Lizard (S. arenicolus) in eastern New Mexico. For S. graciosus gracilis, on sunny days between 0900 and 1100 h, average lizard UVI tracked available solar UVI. Periodic shade-seeking between 1100 and 1600 h resulted in lizard UVI being less than the available solar UVI. This daily pattern of exposure was evident for the activity period from June until August. This general pattern was also evident for S. arenicolus except when air temperatures exceeded 37°C; at these times, all S. arenicolus subjects retreated underground for much of the afternoon. Individuals of S. graciosus gracilis exhibited large within-day variations in the durations of time that they basked in full sun, sought shade, and retreated underground. Two lizards followed for most of a day showe...

Endangered Species in the Oil Patch

Tension among competing interests is nothing new in environmental law. Even among the most tenacious adversaries, the ability to find common ground can serve as an impetus to further the aims of both industry and environmental proponents. Broadly speaking, advocates of the oil and gas industry prefer few restraints, if any, on exploration, development, and production. Comparatively, champions of biological and ecological preservation favor regulatory protections to conserve these interests. Cutting across these often disparate objectives, the Endangered Species Act (ESA) presents a not-so-obvious opportunity for both sides to receive a share of the pie through cooperation and forward planning. This Paper proffers the notion that where concerns over the survival of a species may impede oil and gas activities, proactive cooperation, planning, and compromise within the ESA process can present both industry and environmentalists with a winning outcome. The Paper first provides background information on the ESA and describes its chief statutory mechanics. Next, the Paper discusses recent ESA developments that are particularly relevant to the oil and gas industry and focuses on the cooperative effort related to the Dunes Sagebrush Lizard and pursued by the oil and gas industry, private landowners, state officials in Texas and New Mexico, and environmental organizations. Finally, the Paper reviews pending ESA issues and offers recommendations for private and public stakeholders facing ESA challenges.

Disassembly of a dune‐dwelling lizard community due to landscape fragmentation

Landscape fragmentation alters patterns of landscape structure that affect quality and configuration of habitats, and disrupts population dynamics and persistence of species. Community disassembly, a process of community change due to nonrandom species losses and declines, is occurring worldwide as a result of landscape fragmentation, habitat loss, and habitat degradation. We carried out a comparative study at 27 trapping sites designed to characterize how fragmentation affects community structure in a dune‐dwelling lizard community. Lizard communities in non‐fragmented sites demonstrated nested community structure. Conversely, lizard communities at sites fragmented by roads and well pads from oil and gas development had consistently lower abundance of two species, and demonstrated random community structure. Species loss and lower abundance of species at fragmented sites suggested a pattern of community disassembly. The dunes sagebrush lizard (Sceloporus arenicolus), an ecological specialist, and the lesser earless lizard (Holbrookia maculata) were present on most non‐fragmented sites. However, neither species was present on more than half of the fragmented sites, and their abundances were much lower than on non‐fragmented sites. We attributed reduced species diversity on fragmented sites to quantitative differences in landscape configuration compared to non‐fragmented sites. Specifically, both size and shape of sand dune blowouts differed between non‐fragmented and fragmented sites. Fragmented sites possess more large patches of open sand and barren ground and fewer, smaller, and more dispersed shinnery dune blowouts. Patterns of occurrence and relative abundance suggest S. arenicolus and H. maculata were sensitive to these patch‐scale attributes. In this ecosystem, landscape‐scale fragmentation appears to influence landscape configuration and community disassembly at the patch‐scale. Our findings allow us to disentangle drivers of species loss and enhance our understanding of the processes of community disassembly in fragmented landscapes.

Review of the systematic status of Sceloporus arenicolus Degenhardt and Jones, 1972 with an estimate of divergence time.

The sagebrush lizards (Sceloporus graciosus group) consist of four taxa (S. graciosus graciosus, S. graciosus gracilis, S. graciosus vandenburgianus, and S. arenicolus) distributed in western North America. Of these, S. arenicolus is morphologically, behaviorally, and ecologically distinct as well as geographically disjunct from the other taxa, occurring only in the Mescalero-Monahans Sandhills of southeastern New Mexico and adjacent Texas. Sceloporus arenicolus is a taxon of concern because of its small range and habitat alteration due to land use practices. Understanding evolutionary relationships among members of the S. graciosus group, and especially S. arenicolus, has important implications for conservation. We examine the phylogenetic relationship of S. arenicolus relative to the three recognized subspecies of S. graciosus at mitochondrial and nuclear loci for populations sampled throughout the ranges of these taxa. Additionally, we estimate the divergence time and clade age of S. arenicolus. We find that the S. graciosus group is in need of major taxonomic revision, and also confirm that S. arenicolus is a genetically distinct and divergent lineage. These results bear important consequences for conservation and management.

Landscape Pattern Determines Neighborhood Size and Structure within a Lizard Population

Although defining population structure according to discrete habitat patches is convenient for metapopulation theories, taking this approach may overlook structure within populations continuously distributed across landscapes. For example, landscape features within habitat patches direct the movement of organisms and define the density distribution of individuals, which can generate spatial structure and localized dynamics within populations as well as among them. Here, we use the neighborhood concept, which describes population structure relative to the scale of individual movements, to illustrate how localized dynamics within a population of lizards (Sceloporus arenicolus) arise in response to variation in landscape pattern within a continuous habitat patch. Our results emphasize links between individual movements at small scales and the emergence of spatial structure within populations which resembles metapopulation dynamics at larger scales. We conclude that population dynamics viewed in a landscape context must consider the explicit distribution and movement of individuals within continuous habitat as well as among habitat patches.

Regional credit market for species conservation: Developing the Fort Hood Recovery Credit System

AbstractIn 2005, Fort Hood Military Reservation (Fort Hood, TX, USA) staff sought assistance from the Texas Department of Agriculture and several partner organizations to develop a mitigation approach that included the ability to mitigate temporary impacts to habitat through temporary mitigation agreements with private landowners. Fort Hood, which is home to the largest known population of the federally endangered golden‐cheeked warbler (Setophaga chrysoparia; warbler), was at that time facing increased demands for military training activities that had the potential to disturb, but not likely destroy warbler habitat. Texas Department of Agriculture assembled an advisory committee and 3 stakeholder committees (science, economics, and policy), and tasked them with developing a cost‐efficient system that provided the desired mitigation, while also contributing to the recovery of the warbler. The resulting Recovery Credit System (RCS) enabled Fort Hood to purchase both permanent and temporary credits that represent habitat conservation actions from private landowners for use to mitigate impacts on the installation. We describe our experiences developing and implementing the RCS and briefly discuss new regional credit markets now underway or in development in Utah, USA, for the Utah prairie dog (Cynomys parvidens); in Texas for the dunes sagebrush lizard (Sceloporus arenicolus), golden‐cheeked warbler, black‐capped vireo (Vireo atricapilla), and lesser prairie chicken (Tympanuchus pallidicinctus); and in Colorado, USA, for the greater sage grouse (Centrocercus urophasianus). © 2012 The Wildlife Society.