Genetic and demographic consequences of range contraction patterns during biological annihilation.

Species range contractions both contribute to, and result from, biological annihilation, yet do not receive the same attention as extinctions. Range contractions can lead to marked impacts on populations but are usually characterized only by reduction in extent of range. For effective conservation, it is critical to recognize that not all range contractions are the same. We propose three distinct patterns of range contraction: shrinkage, amputation, and fragmentation. We tested the impact of these patterns on populations of a generalist species using forward-time simulations. All three patterns caused 86-88% reduction in population abundance and significantly increased average relatedness, with differing patterns in declines of nucleotide diversity relative to the contraction pattern. The fragmentation pattern resulted in the strongest effects on post-contraction genetic diversity and structure. Defining and quantifying range contraction patterns and their consequences for Earth's biodiversity would provide useful and necessary information to combat biological annihilation.

Evaluating a herpetofaunal monitoring program in the Rolling Plains of Texas.

We evaluated the herpetofaunal monitoring program on a state-owned property in the Rolling Plains ecoregion of Texas to determine whether the current study design and survey effort are meeting the following monitoring objectives: (1) inventory herpetofaunal diversity on the property, (2) improve understanding of herpetofaunal habitat preferences, and (3) track herpetofaunal response to land management activities. We used the iChao1 species richness estimator to evaluate the sample completeness of the current dataset, which was collected intermittently from 2004 to 2016. Species richness was evaluated by site and year as well as pooled across sites and years. Observed species richness across all sites and years was 23 species, and estimated richness was 23.999 (23.090-34.052, 95% CI). Observed species richness for each year was less than the cumulative total, with 20 species observed in 2004, 6 species observed in 2013, 11 species observed in 2014, and 19 species observed in 2016. The estimated species richness for individual years of sampling ranged from 6.250 to 39.320 species. Our analysis suggests that inadequate sampling design and effort prevents all three objectives from being addressed using the existing dataset. Necessary improvements to the monitoring program to meet all objectives include increasing the spatial and temporal scale of the monitoring effort and utilizing a random sampling protocol. Monitoring methods that address variation in detection probability, such as occupancy and mark-recapture, will also need to play a role. Our findings show that monitoring programs require substantial investment in materials and personnel to obtain datasets sufficient for rigorous biodiversity monitoring.

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.

Modeling the distributions of tegu lizards in native and potential invasive ranges.

Invasive reptilian predators can have substantial impacts on native species and ecosystems. Tegu lizards are widely distributed in South America east of the Andes, and are popular in the international live animal trade. Two species are established in Florida (U.S.A.) - Salvator merianae (Argentine black and white tegu) and Tupinambis teguixin sensu lato (gold tegu) - and a third has been recorded there- S. rufescens (red tegu). We built species distribution models (SDMs) using 5 approaches (logistic regression, multivariate adaptive regression splines, boosted regression trees, random forest, and maximum entropy) based on data from the native ranges. We then projected these models to North America to develop hypotheses for potential tegu distributions. Our results suggest that much of the southern United States and northern México probably contains suitable habitat for one or more of these tegu species. Salvator rufescens had higher habitat suitability in semi-arid areas, whereas S. merianae and T. teguixin had higher habitat suitability in more mesic areas. We propose that Florida is not the only state where these taxa could become established, and that early detection and rapid response programs targeting tegu lizards in potentially suitable habitat elsewhere in North America could help prevent establishment and abate negative impacts on native ecosystems.

Dispersal and population state of an endangered island lizard following a conservation translocation.

Population size is widely used as a unit of ecological analysis, yet to estimate population size requires accounting for observed and latent heterogeneity influencing dispersion of individuals across landscapes. In newly established populations, such as when animals are translocated for conservation, dispersal and availability of resources influence patterns of abundance. We developed a process to estimate population size using N-mixture models and spatial models for newly established and dispersing populations. We used our approach to estimate the population size of critically endangered St. Croix ground lizards (Ameiva polops) five years after translocation of 57 individuals to Buck Island, an offshore island of St. Croix, United States Virgin Islands. Estimates of population size incorporated abiotic variables, dispersal limits, and operative environmental temperature available to the lizards to account for low species detection. Operative environmental temperature and distance from the translocation site were always important in fitting the N-mixture model indicating effects of dispersal and species biology on estimates of population size. We found that the population is increasing its range across the island by 5-10% every six months. We spatially interpolated site-specific abundance from the N-mixture model to the entire island, and we estimated 1,473 (95% CI, 940-1,802) St. Croix ground lizards on Buck Island in 2013 corresponding to survey results. This represents a 26-fold increase since the translocation. We predicted the future dispersal of the lizards to all habitats on Buck Island, with the potential for the population to increase by another five times in the future. Incorporating biologically relevant covariates as explicit parameters in population models can improve predictions of population size and the future spread of species introduced to new localities.

Integrating Multiple Distribution Models to Guide Conservation Efforts of an Endangered Toad.

Species distribution models are used for numerous purposes such as predicting changes in species' ranges and identifying biodiversity hotspots. Although implications of distribution models for conservation are often implicit, few studies use these tools explicitly to inform conservation efforts. Herein, we illustrate how multiple distribution models developed using distinct sets of environmental variables can be integrated to aid in identification sites for use in conservation. We focus on the endangered arroyo toad (Anaxyrus californicus), which relies on open, sandy streams and surrounding floodplains in southern California, USA, and northern Baja California, Mexico. Declines of the species are largely attributed to habitat degradation associated with vegetation encroachment, invasive predators, and altered hydrologic regimes. We had three main goals: 1) develop a model of potential habitat for arroyo toads, based on long-term environmental variables and all available locality data; 2) develop a model of the species' current habitat by incorporating recent remotely-sensed variables and only using recent locality data; and 3) integrate results of both models to identify sites that may be employed in conservation efforts. We used a machine learning technique, Random Forests, to develop the models, focused on riparian zones in southern California. We identified 14.37% and 10.50% of our study area as potential and current habitat for the arroyo toad, respectively. Generally, inclusion of remotely-sensed variables reduced modeled suitability of sites, thus many areas modeled as potential habitat were not modeled as current habitat. We propose such sites could be made suitable for arroyo toads through active management, increasing current habitat by up to 67.02%. Our general approach can be employed to guide conservation efforts of virtually any species with sufficient data necessary to develop appropriate distribution models.

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.

The phylogenetic position of the Critically Endangered Saint Croix ground lizard Ameiva polops: revisiting molecular systematics of West Indian Ameiva.

The phylogenetic position of the critically endangered Saint Croix ground lizard Ameiva polops is presently unknown and several hypotheses have been proposed. We investigated the phylogenetic position of this species using molecular phylogenetic methods. We obtained sequences of DNA fragments of the mitochondrial ribosomal genes 12S rDNA and 16S rDNA for this species. We aligned these sequences with published sequences of other Ameiva species, which include most of the Ameiva species from the West Indies, three Ameiva species from Central America and South America, and one from the teiid lizard Tupinambis teguixin, which was used as outgroup. We conducted Maximum Likelihood and Bayesian phylogenetic analyses. The phylogenetic reconstructions among the different methods were very similar, supporting the monophyly of West Indian Ameiva and showing within this lineage, a basal polytomy of four clades that are separated geographically. Ameiva polops grouped in a cluster that included the other two Ameiva species found in the Puerto Rican Bank: A. wetmorei and A. exsul. A sister relationship between A. polops and A. wetmorei is suggested by our analyses. We compare our results with a previous study on molecular systematics of West Indian Ameiva. 

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.

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.

Applied biodiversity science: Bridging ecology, culture, and governance for effective conservation / Ciencia aplicada en biodiversidad: Integrando ecología, cultura y gobernancia para la conservación efectiva / Ciência aplicada em biodiversidade: Integrando ecologia, cultura e governancia para a conservação efetiva

Solutions to the biodiversity crisis will ultimately come from biological scientists and social scientists working in tandem, yet disconnects among scientific disciplines, conservation institutions, and practical implementation hinder effective conservation. The vision of Applied Biodiversity Science (ABS) is to achieve integration between biodiversity research and on-the-ground conservation practices. Three pillars support ABS: 1) integrated social and biological research; 2) cross-disciplinary collaboration with local conservation institutions and actors; and 3) application of conservation theory to practice. Our ABS program, including a doctoral training program, is focused on two cross-cutting themes: Ecological Functions and Biodiversity; and Communities and Governance. The research integration matrix matches causes of biodiversity loss against research approaches, and is thus a useful tool for defining integrative questions and building interdisciplinary research teams. Case studies from Western Amazon and Gran Chaco illustrate how the ABS model has been implemented in the Americas. The intention is that ABS approaches will produce conservation scientists who communicate effectively across disciplines, and make their research relevant to ongoing programs. The ABS approach helps elucidate how and why ecosystem functions, biodiversity, human communities and governance systems are interconnected.

Las soluciones para la crisis de biodiversidad serán generadas finalmente a partir del trabajo conjunto de científicos naturales y sociales. Pero la desconexión entre disciplinas, instituciones conservacionistas y la implementación de conocimientos impiden la conservación efectiva. La visión de la Ciencia de Biodiversidad Aplicada (CBA) es lograr la integración entre investigación sobre biodiversidad y la práctica de la conservación. Tres pilares sustentan esta propuesta: 1) investigación biológica y social integrada; 2) colaboración entre disciplinas con instituciones y actores locales que trabajan en conservación; y 3) implementación práctica de teorías sobre conservación. Nuestro programa CBA incluye un programa para estudiantes de doctorado y está enfocado en dos temas de investigación: funciones ecológicas y biodiversidad, y comunidades y gobernabilidad. La matriz integrada de investigación relaciona las causas de la pérdida de biodiversidad con los enfoques de la investigación, siendo una herramienta útil para definir hipótesis integradas y formar equipos interdisciplinarios de investigación. Estudios de casos de Amazonia y el Gran Chaco demuestran cómo implementamos el modelo de CBA en Suramérica. La intención es que el enfoque CBA produzca científicos de la conservación que se comuniquen efectivamente entre disciplinas y sus estudios sean relevantes para los programas en ejecución. El enfoque planteado ayudaría a iluminar cómo y porqué las funciones de los ecosistemas, la biodiversidad, las comunidades humanas y los sistemas de gobernabilidad están interconectadas.

As soluções para a crise de biodiversidade serão geradas finalmente apartir do trabalho conjunto de cientistas naturais e sociais. Mas a desconexão entre disciplinas, instituições conservacionistas e a implementação de conhecimentos impedem a conservação efetiva. A visão da Ciência de Biodiversidade Aplicada (CBA) é conseguir a integração entre investigação sobre biodiversidade e a prática da conservação. Três pilares sustentam esta proposta: 1) investigação biológica e social integrada; 2) colaboração entre disciplinas com instituições e atores locais que trabalham em conservação; e 3) implementação prática de teorias sobre conservação. Nosso programa CBA inclui um programa para estudantes de doutorado e está focado em dois temas de investigação: funções ecológicas e biodiversidade, e comunidades e governabilidade. A matriz integrada de investigação relaciona as causas da perda de biodiversidade com as abordagens da investigação, sendo uma ferramenta útil para definir hipóteses integradas e formar equipes interdisciplinárias de investigação. Estudos de casos da Amazônia e o Gran Chaco demonstram como implementamos o modelo de CBA na América do sul. A intenção é de que a abordagem CBA gere cientistas da conservação que se comuniquem efetivamente entre disciplinas e seus estudos sejam relevantes para os programas em execução. A abordagem sugerida ajudaria a iluminar como e porquê as funções dos ecossistemas, a biodiversidade, as comunidades humanas e os sistemas de governabilidade estão interconectadas.

Genetic relationships of American alligator populations distributed across different ecological and geographic scales.

Although much work has been conducted on coastal populations of the American alligator (Alligator mississippiensis), less is known about the population dynamics and genetic structure of populations of alligators confined to inland habitats. DNA microsatellite loci, derived from the American alligator, were used to investigate patterns of genetic variation within and between populations of alligators distributed at coastal and inland localities in Texas. These data were used to evaluate the genetic discreteness of different alligator stocks relative to their basic ecology at these sites. Observed mean heterozygosities across seven loci for both coastal and inland populations ranged from 0.50-0.61, with both inland and coastal populations revealing similar patterns of variation. Measures of F(st) revealed significant population differentiation among all populations; however, analyses of molecular variance (AMOVAs) failed to demonstrate any apparent geographic pattern relative to the population differentiation indicated by F(st) values. Each population contained unique alleles for at least one locus. Additionally, assignment tests based on the distribution of genotypes placed 76% of individuals to their source population. These genetic data suggest considerable subdivision among alligator populations, possibly influenced by demographic and life history differences as well as barriers to dispersal. These results have clear implications for management. Rather than managing alligators in Texas as a single panmictic population, translocation programs and harvest quotas should consider the ecological and genetic distinctiveness of local alligator populations.

Competition, predation, and the distributions of four desert anurans.

Several studies have shown that larval competition and susceptibility to predation affect distributions of amphibian assemblages across ephemeral and perennial habitats. However, few studies have examined mechanisms affecting distribution patterns and site use of anurans adapted to highly ephemeral habitats. This study examines hypotheses about competition and predation as mechanisms creating non-overlapping patterns of site use in four anurans that breed in highly ephemeral habitats: Scaphiopus couchii (Couch's spade-foot toad), Gastrophryne olivacea (narrow-mouthed toad), Bufo speciosus (Texas toad), and Bufo punctatus (red-spotted toad). These four anurans showed a significantly nonrandom pattern of co-occurrence. Only 12% of 95 ephemeral breeding sites surveyed were occupied by more than one species. We tested the hypotheses that non-overlapping use of breeding sites was due to activity rates of their tadpoles that in turn reflect their competitive ability and susceptibility to predation. Tadpoles of S. couchii were significantly more active and more susceptible to predation than were tadpoles of G. olivacea, B. speciosus, and B. punctatus. The masses of G. olivacea, B. speciosus, and B. punctatus were less when they were reared with S. couchii, demonstrating the possible competitive dominance of S. couchii. These results suggest that the competitive ability of S. couchii may play a role in excluding G. olivacea, B. speciosus, and B. punctatus from very ephemeral breeding sites, and that susceptibility to predation could play a role in excluding S. couchii from breeding sites of longer duration that are more likely to be colonized by aquatic predators.

Morphological correlates of locomotor performance in hatchling Amblyrhynchus cristatus.

Previous studies of locomotor performance from a variety of perspectives often assumed that speed and limb length were strongly correlated. Despite support of this assumption from biomechanical models, few empirical studies have demonstrated a significant relationship between measures of locomotor capacity, such as maximum velocity, and length of the hindlimb at either the inter- or intra-specific level. We examined whether one measure of locomotor performance, maximum velocity, correlates with body size and elements of the hindlimb in hatchling marine iguanas (Amblyrhynchus cristatus). Larger hatchlings ran faster. Removing the effects of body size revealed that relative lengths of the tibia and hindfoot correlated with size-adjusted maximum velocity. Individuals with relatively long tibia and short pes were relatively faster than individuals with short tibia and long pes. Functional morphological analyses predict that femur length should correlate with maximum velocity. However, our analyses failed to support this prediction. Because hatchling marine iguanas exploit relatively open habitats, the relationship between maximum velocity and limb morphology may be interpreted as an adaptation enhancing escape from predators.