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At least 307 records · Page 17Linked to original sources
USGS2013

Genetic structure, diversity and subspecies status of Gull-billed Terns (Gelochelidon nilotica) from the United States

Gull-billed Terns (Gelochelidon nilotica) are among the most widespread, yet scarce, Charadriiformes in the world. Two subspecies are recognized in the United States: G. n. aranea breeds along the U.S. Atlantic and Gulf coasts and G. n. vanrossemi breeds in the Salton Sea and San Diego Bay of California. Conservation concerns exist for the species due to its low abundance in the United States and apparent declines in some parts of its North American range. We used nuclear microsatellite markers and mitochondrial DNA sequences to assess genetic diversity and differentiation patterns among Gull-billed Tern populations from Virginia, Texas, and California. We also tested for evidence of population bottlenecks, and evaluated the support our data provide for the North American subspecies. Genetic diversity was highest in Texas and underscored the importance of habitat in that large population. Significant population differentiation existed, but could not be consistently identified using various analytical approaches and suggested that the magnitude of differentiation was low. No evidence for bottlenecks was identified. Our data could not distinguish individuals from different subspecies and therefore do not support the current intraspecific taxonomy. Tenable explanations for many findings are related to the low site tenacity demonstrated by the species.

Waterbirds↗
USGS2016

Jaguar taxonomy and genetic diversity for southern Arizona, United States, and Sonora, Mexico

Executive Summary The jaguar is the largest Neotropical felid and the only extant representative of the genus Panthera in the Americas. In recorded history, the jaguars range has extended from the Southern United States, throughout Mexico, to Central and South America, and they occupy a wide variety of habitats. A previous jaguar genetic study found high historical levels of gene flow among jaguar populations over broad areas but did not include any samples of jaguar from the States of Arizona, United States, or Sonora, Mexico. Arizona and Sonora have been part of the historical distribution of jaguars; however, poaching and habitat fragmentation have limited their distribution until they were declared extinct in the United States and endangered in Sonora. Therefore, a need was apparent to have this northernmost (Arizona/Sonora) jaguar population included in an overall jaguar molecular taxonomy and genetic diversity analyses. In this study, we used molecular genetic markers to examine diversity and taxonomy for jaguars in the Northwestern Jaguar Recovery Unit (NJRU; Sonora, Sinaloa, and Jalisco, Mexico; and southern Arizona and New Mexico, United States) relative to jaguars in other parts of the jaguar range (Central and South America). The objectives of this study were to: Collect opportunistic jaguar samples (hide, blood, hair, saliva, and scat), from historical and current individuals, that originated in NJRU areas of Arizona, New Mexico, and Sonora; Use these samples to assess molecular taxonomy of NJRU jaguars compared to data from a previous study of jaguars rangewide; and Develop suggestions for conservation of NJRU jaguars based on the results.

Arizona, Jalisco, New Mexico, Sonora, Sinaloa↗
USGS2012

The challenge of retarding erosion of island biodiversity through phytosanitary measures: An update on the case of Puccinia psidii in Hawai'i

Most rust fungi are highly host specific, but Puccina psidii has an extremely broad host range within Myrtaceae and gained notoriety with a host jump in its native Brazil from common guava ( Psidium guajava ) to commercial Eucalyptus plantations. When detected in Hawaiʻi in April 2005, the first invasion outside the neotropics/subtropics, there was immediate concern for ʻōhiʻa (Metrosideros polymorpha). ʻŌhiʻa composes 80% of native forest statewide, providing stable watersheds and habitat for most Hawaiian forest birds and plants. Within months, rust spores spread statewide on wind currents, but ʻōhiʻa was found to be only a minor host, showing very light damage. The primary host was nonnative rose apple ( Syzygium jambos ), severely affected at a landscape scale, but the epiphytotic subsided as rose apple was largely defoliated or killed within several years. The limited and stable host range in Hawaiʻi (versus elsewhere) led the local conservation community to explore possibilities for excluding new genetic strains of P. psidii . Although national/international phytosanitary standards require strong scientific justification for regulations involving an infraspecific taxonomic level, hopes were buoyed when genetic studies showed no apparent genetic variation/evolution in Hawaiʻi's rust strain. A sophisticated genetic study of P. psidii in its home range is near completion; genetic variation is substantial, and host species strongly influences rust population structure. To prevent introduction of new strains, the Hawaiʻi Department of Agriculture is moving ahead with establishing stringent measures that restrict entry of Myrtaceae into Hawaiʻi. Meanwhile, P. psidii poses a major threat to Myrtaceae biodiversity worldwide.

Hawai'i↗
USGS2020

Conservative plumage masks extraordinary phylogenetic diversity in the Grallaria rufula (Rufous Antpitta) complex of the humid Andes

The Grallaria rufula complex is currently considered to consist of 2 species, G. rufula (Rufous Antpitta) and G. blakei (Chestnut Antpitta). However, it has been suggested that the complex, populations of which occur in humid montane forests from Venezuela to Bolivia, comprises a suite of vocally distinct yet morphologically cryptic species. We sequenced nuclear and mitochondrial DNA for 80 individuals from across the distribution of the complex to determine the extent of genetic variation between and within described taxa. Our results revealed 18 geographically coherent clades separated by substantial genetic divergence: 14 within rufula, 3 within blakei, and 1 corresponding to G. rufocinerea (Bicolored Antpitta), a species with distinctive plumage found to be nested within the complex. Neither G. rufula nor G. blakei as presently defined was monophyletic. Although 6 of the 7 recognized subspecies of G. rufula were monophyletic, several subspecies contained substantial genetic differentiation. Genetic variation was largely partitioned across recognized geographic barriers, especially across deep river valleys in Peru and Colombia. Coalescent modeling identified 17 of the 18 clades as significantly differentiated lineages, whereas analyses of vocalizations delineated 16 biological species within the complex. The G. rufula complex seems unusually diverse even among birds of the humid Andes, a prime location for cryptic speciation; however, the extent to which other dispersal-limited Andean species groups exhibit similar degrees of cryptic differentiation awaits further study.

Auk↗
USGS2015

Targeting climate diversity in conservation planning to build resilience to climate change

Climate change is raising challenging concerns for systematic conservation planning. Are methods based on the current spatial patterns of biodiversity effective given long-term climate change? Some conservation scientists argue that planning should focus on protecting the abiotic diversity in the landscape, which drives patterns of biological diversity, rather than focusing on the distribution of focal species, which shift in response to climate change. Climate is one important abiotic driver of biodiversity patterns, as different climates host different biological communities and genetic pools. We propose conservation networks that capture the full range of climatic diversity in a region will improve the resilience of biotic communities to climate change compared to networks that do not. In this study we used historical and future hydro-climate projections from the high resolution Basin Characterization Model to explore the utility of directly targeting climatic diversity in planning. Using the spatial planning tool, Marxan, we designed conservation networks to capture the diversity of climate types, at the regional and sub-regional scale, and compared them to networks we designed to capture the diversity of vegetation types. By focusing on the Conservation Lands Network (CLN) of the San Francisco Bay Area as a real-world case study, we compared the potential resilience of networks by examining two factors: the range of climate space captured, and climatic stability to 18 future climates, reflecting different emission scenarios and global climate models. We found that the climate-based network planned at the sub-regional scale captured a greater range of climate space and showed higher climatic stability than the vegetation and regional based-networks. At the same time, differences among network scenarios are small relative to the variance in climate stability across global climate models. Across different projected futures, topographically heterogeneous areas consistently show greater climate stability than homogenous areas. The analysis suggests that utilizing high-resolution climate and hydrological data in conservation planning improves the likely resilience of biodiversity to climate change. We used these analyses to suggest new conservation priorities for the San Francisco Bay Area.

Ecosphere↗
USGS2020

An updated genetic marker for detection of Lake Sinai Virus and metagenetic applications

Background Lake Sinai Viruses (LSV) are common RNA viruses of honey bees ( Apis mellifera ) that frequently reach high abundance but are not linked to overt disease. LSVs are genetically heterogeneous and collectively widespread, but despite frequent detection in surveys, the ecological and geographic factors structuring their distribution in A. mellifera are not understood. Even less is known about their distribution in other species. Better understanding of LSV prevalence and ecology have been hampered by high sequence diversity within the LSV clade. Methods Here we report a new polymerase chain reaction (PCR) assay that is compatible with currently known lineages with minimal primer degeneracy, producing an expected 365 bp amplicon suitable for end-point PCR and metagenetic sequencing. Using the Illumina MiSeq platform, we performed pilot metagenetic assessments of three sample sets, each representing a distinct variable that might structure LSV diversity (geography, tissue, and species). Results The first sample set in our pilot assessment compared cDNA pools from managed A. mellifera hives in California ( n = 8) and Maryland ( n = 6) that had previously been evaluated for LSV2, confirming that the primers co-amplify divergent lineages in real-world samples. The second sample set included cDNA pools derived from different tissues (thorax vs. abdomen, n = 24 paired samples), collected from managed A. mellifera hives in North Dakota. End-point detection of LSV frequently differed between the two tissue types; LSV metagenetic composition was similar in one pair of sequenced samples but divergent in a second pair. Overall, LSV1 and intermediate lineages were common in these samples whereas variants clustering with LSV2 were rare. The third sample set included cDNA from individual pollinator specimens collected from diverse landscapes in the vicinity of Lincoln, Nebraska. We detected LSV in the bee Halictus ligatus (four of 63 specimens tested, 6.3%) at a similar rate as A. mellifera (nine of 115 specimens, 7.8%), but only one H. ligatus sequencing library yielded sufficient data for compositional analysis. Sequenced samples often contained multiple divergent LSV lineages, including individual specimens. While these studies were exploratory rather than statistically powerful tests of hypotheses, they illustrate the utility of high-throughput sequencing for understanding LSV transmission within and among species.

California, Maryland, Nebraska↗
USGS2013

Biodiversity in a changing climate: a synthesis of current and projected trends in the US

This paper provides a synthesis of the recent literature describing how global biodiversity is being affected by climate change and is projected to respond in the future. Current studies reinforce earlier findings of major climate-change-related impacts on biological systems and document new, more subtle after-effects. For example, many species are shifting their distributions and phenologies at faster rates than were recorded just a few years ago; however, responses are not uniform across species. Shifts have been idiosyncratic and in some cases counterintuitive, promoting new community compositions and altering biotic interactions. Although genetic diversity enhances species' potential to respond to variable conditions, climate change may outpace intrinsic adaptive capacities and increase the relative vulnerabilities of many organisms. Developing effective adaptation strategies for biodiversity conservation will not only require flexible decision-making and management approaches that account for uncertainties in climate projections and ecological responses but will also necessitate coordinated monitoring efforts.

Frontiers in Ecology and the Environment↗
USGS2016

Hydrothermal vents and methane seeps: Rethinking the sphere of influence

Although initially viewed as oases within a barren deep ocean, hydrothermal vent and methane seep communities are now recognized to interact with surrounding ecosystems on the sea floor and in the water column, and to affect global geochemical cycles. The importance of understanding these interactions is growing as the potential rises for disturbance from oil and gas extraction, seabed mining and bottom trawling. Here we synthesize current knowledge of the nature, extent and time and space scales of vent and seep interactions with background systems. We document an expanded footprint beyond the site of local venting or seepage with respect to elemental cycling and energy flux, habitat use, trophic interactions, and connectivity. Heat and energy are released, global biogeochemical and elemental cycles are modified, and particulates are transported widely in plumes. Hard and biotic substrates produced at vents and seeps are used by “benthic background” fauna for attachment substrata, shelter, and access to food via grazing or through position in the current, while particulates and fluid fluxes modify planktonic microbial communities. Chemosynthetic production provides nutrition to a host of benthic and planktonic heterotrophic background species through multiple horizontal and vertical transfer pathways assisted by flow, gamete release, animal movements, and succession, but these pathways remain poorly known. Shared species, genera and families indicate that ecological and evolutionary connectivity exists among vents, seeps, organic falls and background communities in the deep sea; the genetic linkages with inactive vents and seeps and background assemblages however, are practically unstudied. The waning of venting or seepage activity generates major transitions in space and time that create links to surrounding ecosystems, often with identifiable ecotones or successional stages. The nature of all these interactions is dependent on water depth, as well as regional oceanography and biodiversity. Many ecosystem services are associated with the interactions and transitions between chemosynthetic and background ecosystems, for example carbon cycling and sequestration, fisheries production, and a host of non-market and cultural services. The quantification of the sphere of influence of vents and seeps could be beneficial to better management of deep-sea environments in the face of growing industrialization.

Frontiers in Marine Science↗
USGS2026

Longitudinal variability of demographics and life history in an anadromous spawning population within a large, unimpeded East Coast, USA, watershed

Objective The goal of this study was to characterize the variability in age, growth, and life history of sea-run fish throughout a large, East Coast, USA, watershed to improve the parameterization of longitudinal variation in demographics and spawning histories in an undammed river. Methods Both live and dead American Shad Alosa sapidissima were collected during spring 2020 and 2021. Sex, length, age, and repeat spawning information were recorded for all individuals ( n = 512). Growth curves were created to test hypotheses about the variables that were related to the growth rates of American Shad for this relatively unsampled portion of the spawning population in the Delaware River. Results We observed variation in size, age, repeat spawning probability and propensity, and sex ratios from downstream to upstream as well as during the spawning season. Individual traits also varied among the fish that died during migration and those that were collected alive. Conclusions This study expands the current knowledge about variability in the life history traits that are commonly used in assessing and managing an anadromous fish that spawns upstream in a large, undammed watershed. Our results have broad implications for the assessment and management of anadromous fish populations globally and contribute to understanding parity along a continuum. Some potential priorities for future work include using telemetry to understand the final disposition of live fish, investigating fine-scale genetic control for correlated life-history traits, and investigating the correlations between natal origin (i.e., genetic stock mixing) and longitudinal variation within spawning populations.

New York, Pennsylvania↗
USGS2014

Spatial genetic structure of bristle-thighed curlews (Numenius tahitiensis): Breeding area differentiation not reflected on the non-breeding grounds

Migratory birds occupy geographically and ecologically disparate areas during their annual cycle with conditions on breeding and non-breeding grounds playing separate and important roles in population dynamics. We used data from nuclear microsatellite and mitochondrial DNA control region loci to assess the breeding and non-breeding spatial genetic structure of a transoceanic migrant shorebird, the bristle-thighed curlew. We found spatial variance in the distribution of allelic and haplotypic frequencies between the curlew's two breeding areas in Alaska but did not observe this spatial structure throughout its non-breeding range on low-lying tropical and subtropical islands in the Central Pacific (Oceania). This suggests that the two breeding populations do not spatially segregate during the non-breeding season. Lack of migratory connectivity is likely attributable to the species' behavior, as bristle-thighed curlews exhibit differential timing of migration and some individuals move among islands during non-breeding months. Given the detrimental impact of many past and current human activities on island ecosystems, admixture of breeding populations in Oceania may render the bristle-thighed curlew less vulnerable to perturbations there, as neither breeding population will be disproportionally affected by local habitat losses or by stochastic events. Furthermore, lack of migratory connectivity may enable bristle-thighed curlews to respond to changing island ecosystems by altering their non-breeding distribution. However, availability of suitable non-breeding habitat for curlews in Oceania is increasingly limited on both low-lying and high islands by habitat loss, sea level rise, and invasive mammalian predators that pose a threat to flightless and flight-compromised curlews during the molting period.

Conservation Genetics↗
USGS2023

A Fisherman's Tale: An unusual observation of the Ozark Cavefish, Troglichthys (= Amblyopsis) Rosae (Eigenmann)

Troglichthys (= Amblyopsis ) rosae (Ozark Cavefish) is currently known from 83 locations within the Ozark Highlands ecoregion. We found a cavefish at a new location in the Grand Lake O' the Cherokees on the western side of the Neosho River (Delaware County, OK), which is on the northwest periphery of the Ozark Cavefish range. Examination of the mitochondrial ND2 gene supports that the specimen is an Ozark Cavefish, but distinct (4.6–9.2% pairwise distance) from other specimens that have been genetically sampled, and could represent a unique population. Future research should focus on expanding sampling efforts and conducting a range-wide genetic analysis of the Ozark Cavefish.

Southeastern Naturalist↗
USGS2015

Ecology and conservation of North American sea ducks

The past decade has seen a huge increase in the interest and attention directed toward sea ducks, the Mergini tribe. This has been inspired, in large part, by the conservation concerns associated with numerical declines in several sea duck species and populations, as well as a growing appreciation for their interesting ecological attributes. Reflecting the considerable research recently conducted on this tribe, Ecology and Conservation of North American Sea Ducks examines the 15 extant species of sea ducks from North America. Chapters are organized conceptually to focus on, compare, and contrast the ecological attributes of the tribe. Experts provide in-depth treatments of a range of topics, including: Population dynamics and genetics Infectious diseases and parasites Breeding costs and cross-seasonal affects Contaminant burdens Foraging behavior and energetics Migration strategies, molt ecology, and habitat affinities and dynamics Breeding systems and reproductive behavior Harvest history The book presents a comprehensive synthesis of sea duck ecology, documents factors that have caused population declines of some species, and provides managers with measures to enhance recovery of depressed populations of sea ducks in North America. Capturing the current state of knowledge of this unique tribe, it provides a benchmark for where we are in conservation efforts and suggests future directions for researchers, managers, students, conservationists, and avian enthusiasts.

Book↗
USGS2005

Overview of recent DNA vaccine development for fish

Since the first description of DNA vaccines for fish in 1996, numerous studies of genetic immunisation against the rhabdovirus pathogens infectious haematopoietic necrosis virus (IHNV) and viral haemorrhagic septicaemia virus (VHSV) have established their potential as both highly efficacious biologicals and useful basic research tools. Single small doses of rhabdovirus DNA constructs provide extremely strong protection against severe viral challenge under a variety of conditions. DNA vaccines for several other important fish viruses, bacteria, and parasites are under investigation, but they have not yet shown high efficacy. Therefore, current research is focussed on mechanistic studies to understand the basis of protection, and on improvement of the nucleic acid vaccine applications against a wider range of fish pathogens.

Conference Paper↗
USGS2016

Rare earth element deposits in China

China is the world’s leading rare earth element (REE) producer and hosts a variety of deposit types. Carbonatite- related REE deposits, the most significant deposit type, include two giant deposits presently being mined in China, Bayan Obo and Maoniuping, the first and third largest deposits of this type in the world, respectively. The carbonatite-related deposits host the majority of China’s REE resource and are the primary supplier of the world’s light REE. The REE-bearing clay deposits, or ion adsorption-type deposits, are second in importance and are the main source in China for heavy REE resources. Other REE resources include those within monazite or xenotime placers, beach placers, alkaline granites, pegmatites, and hydrothermal veins, as well as some additional deposit types in which REE are recovered as by-products. Carbonatite-related REE deposits in China occur along craton margins, both in rifts (e.g., Bayan Obo) and in reactivated transpressional margins (e.g., Maoniuping). They comprise those along the northern, eastern, and southern margins of the North China block, and along the western margin of the Yangtze block. Major structural features along the craton margins provide first-order controls for REE-related Proterozoic to Cenozoic carbonatite alkaline complexes; these are emplaced in continental margin rifts or strike-slip faults. The ion adsorption-type REE deposits, mainly situated in the South China block, are genetically linked to the weathering of granite and, less commonly, volcanic rocks and lamprophyres. Indosinian (early Mesozoic) and Yanshanian (late Mesozoic) granites are the most important parent rocks for these REE deposits, although Caledonian (early Paleozoic) granites are also of local importance. The primary REE enrichment is hosted in various mineral phases in the igneous rocks and, during the weathering process, the REE are released and adsorbed by clay minerals in the weathering profile. Currently, these REE-rich clays are primarily mined from open-pit operations in southern China. The complex geologic evolution of China’s Precambrian blocks, particularly the long-term subduction of ocean crust below the North and South China blocks, enabled recycling of REE-rich pelagic sediments into mantle lithosphere. This resulted in the REE-enriched nature of the mantle below the Precambrian cratons, which were reactivated and thus essentially decratonized during various tectonic episodes throughout the Proterozoic and Phanerozoic. Deep fault zones within and along the edges of the blocks, including continental rifts and strike-slip faults, provided pathways for upwelling of mantle material.

Book chapter↗
USGS1997

Status and management of the PaliIa, an endangered Hawaiian honeycreeper, 1987-1996

A single, relictual population of Palila Loxioides bailleui, a Hawaiian honeycreeper, survives on the slopes of Mauna Kea volcano on the island of Hawai'i, where it feeds principally on flowers and green seeds of the mamane tree Sophora chrysophylla. The Palila was listed as an endangered species by state and federal governments because of continuing damage to its habitat by browsing Feral and Mouflon Sheep Ovis aries and O. musimon and Goats Capra hircus and because of the bird's restricted range and low numbers. Ecology of the Palila was studied from 1987 to 1996. Annual population estimates fluctuated between 1 600 and 5 700 and averaged 3 400 birds. Estimates varied with availability of mamane seeds, which are less abundant in drought years. In drought years, most birds did not attempt to breed, and survival rates were lower because of a shortage of food. Availability of mamane seeds also showed large seasonal variability. While some nests were preyed upon by Owls Asio flammeus, Cats Felis catus and Rats Rattus rattus, losses were high at the end of the season from unexplained death of eggs and chicks. Genetic studies did not implicate inbreeding depression. Neither avian malaria nor avian pox appeared at this site, where the mosquito vector was absent. However, weather and food shortage worsened towards the end of the nesting season. Availability of food and habitat remain the principal factors limiting increase in the Palila population. Recovery efforts now focus on reducing numbers of feral ungulates, fire management, removing mammalian predators, and developing techniques for captive propagation and introduction to currently unoccupied sites within the bird's former range. Reforestation adjacent to the Mauna Kea Forest Reserve would allow the Palila population to expand and grow.

Pacific Conservation Biology↗
USGS2013

Population genetics and evaluation of genetic evidence for subspecies in the Semipalmated Sandpiper (Calidris pusilla)

Semipalmated Sandpipers ( Calidris pusilla ) are among the most common North American shorebirds. Breeding in Arctic North America, this species displays regional differences in migratory pathways and possesses longitudinal bill length variation. Previous investigations suggested that genetic structure may occur within Semipalmated Sandpipers and that three subspecies corresponding to western, central, and eastern breeding groups exist. In this study, mitochondrial control region sequences and nuclear microsatellite loci were used to analyze DNA of birds (microsatellites: n = 120; mtDNA: n = 114) sampled from seven North American locations. Analyses designed to quantify genetic structure and diversity patterns, evaluate genetic evidence for population size changes, and determine if genetic data support the existence of Semipalmated Sandpiper subspecies were performed. Genetic structure based only on the mtDNA data was observed, whereas the microsatellite loci provided no evidence of genetic differentiation. Differentiation among locations and regions reflected allele frequency differences rather than separate phylogenetic groups, and similar levels of genetic diversity were noted. Combined, the two data sets provided no evidence to support the existence of subspecies and were not useful for determining migratory connectivity between breeding sites and wintering grounds. Birds from western and central groups displayed signatures of population expansions, whereas the eastern group was more consistent with a stable overall population. Results of this analysis suggest that the eastern group was the source of individuals that colonized the central and western regions currently utilized by Semipalmated Sandpipers.

Waterbirds↗
USGS2019

Decision-making in agent-based modeling: A current review and future prospectus

All basic processes of ecological populations involve decisions; when and where to move, when and what to eat, and whether to fight or flee. Yet decisions and the underlying principles of decision-making have been difficult to integrate into the classical population-level models of ecology. Certainly, there is a long history of modeling individuals' searching behavior, diet selection, or conflict dynamics within social interactions. When all the individuals are given certain simple rules to govern their decision-making processes, the resultant population–level models have yielded important generalizations and theory. But it is also recognized that such models do not represent the way real individuals decide on actions. Factors that influence a decision include the organism's environment with its dynamic rewards and risks, the complex internal state of the organism, and its imperfect knowledge of the environment. In the case of animals, it may also involve complex social factors, and experience and learning, which vary among individuals. The way that all factors are weighed and processed to lead to decisions is a major area of behavioral theory. While classic population-level modeling is limited in its ability to integrate decision-making in its actual complexity, the development of individual- or agent-based models (IBM/ABMs) (we use ABM throughout to designate both “agent-based modeling” and an “agent-based model”) has opened the possibility of describing the way that decisions are made, and their effects, in minute detail. Over the years, these models have increased in size and complexity. Current ABMs can simulate thousands of individuals in realistic environments, and with highly detailed internal physiology, perception and ability to process the perceptions and make decisions based on those and their internal states. The implementation of decision-making in ABMs ranges from fairly simple to highly complex; the process of an individual deciding on an action can occur through the use of logical and simple (if-then) rules to more sophisticated neural networks and genetic algorithms. The purpose of this paper is to give an overview of the ways in which decisions are integrated into a variety of ABMs and to give a prospectus on the future of modeling of decisions in ABMs.

Frontiers in Ecology and Evolution↗
USGS2000

Genetic variation in the endangered Southwestern Willow Flycatcher

The Southwestern Willow Flycatcher ( Empidonax traillii extimus ) is an endangered Neotropical migrant that breeds in isolated remnants of dense riparian habitat in the southwestern United States. We estimated genetic variation at 20 breeding sites of the Southwestern Willow Flycatcher (290 individuals) using 38 amplified fragment length polymorphisms (AFLPs). Our results suggest that considerable genetic diversity exists within the subspecies and within local breeding sites. Statistical analyses of genetic variation revealed only slight, although significant, differentiation among breeding sites (Mantel's r = 0.0705, P < 0.0005; θ = 0.0816, 95% CI = 0.0608 to 0.1034; Φ ST = 0.0458, P < 0.001). UPGMA cluster analysis of the AFLP markers indicates that extensive gene flow has occurred among breeding sites. No one site stood out as being genetically unique or isolated. Therefore, the small level of genetic structure that we detected may not be biologically significant. Ongoing field studies are consistent with this conclusion. Of the banded birds that were resighted or recaptured in Arizona during the 1996 to 1998 breeding seasons, one-third moved between breeding sites and two-thirds were philopatric. Low differentiation may be the result of historically high rangewide diversity followed by recent geographic isolation of breeding sites, although observational data indicate that gene flow is a current phenomenon. Our data suggest that breeding groups of E. t. extimus act as a metapopulation.

The Auk↗