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USGS2012

Genetic diversity of a newly established population of golden eagles on the Channel Islands, California

Gene flow can have profound effects on the genetic diversity of a founding population depending on the number and relationship among colonizers and the duration of the colonization event. Here we used data from nuclear microsatellite and mitochondrial DNA control region loci to assess genetic diversity in golden eagles of the recently colonized Channel Islands, California. Genetic diversity in the Channel Island population was low, similar to signatures observed for other recent colonizing island populations. Differences in levels of genetic diversity and structure observed between mainland California and the islands suggests that few individuals were involved in the initial founding event, and may have comprised a family group. The spatial genetic structure observed between Channel Island and mainland California golden eagle populations across marker types, and genetic signature of population decline observed for the Channel Island population, suggest a single or relatively quick colonization event. Polarity in gene flow estimates based on mtDNA confirm an initial colonization of the Channel Islands by mainland golden eagles, but estimates from microsatellite data suggest that golden eagles on the islands were dispersing more recently to the mainland, possibly after reaching the carrying capacity of the island system. These results illustrate the strength of founding events on the genetic diversity of a population, and confirm that changes to genetic diversity can occur within just a few generations.

California↗

USGS2015

Hydrographic surveys at seven chutes and three backwaters on the Missouri River in Nebraska, Iowa, and Missouri, 2011-13

The U.S. Geological Survey cooperated with the U.S. Army Corps of Engineers (USACE), Omaha District, to complete hydrographic surveys of seven chutes and three backwaters on the Missouri River yearly during 2011–13. These chutes and backwaters were constructed by the USACE to increase the amount of available shallow water habitat (SWH) to support threatened and endangered species, as required by the amended “2000 Biological Opinion” on the operation of the Missouri River main-stem reservoir system. Chutes surveyed included Council chute, Plattsmouth chute, Tobacco chute, Upper Hamburg chute, Lower Hamburg chute, Kansas chute, and Deroin chute. Backwaters surveyed included Ponca backwater, Plattsmouth backwater, and Langdon backwater. Hydrographic data from these chute and backwater surveys will aid the USACE to assess the current (2011–13) amount of available SWH, the effects river flow have had on evolving morphology of the chutes and backwaters, and the functionality of the chute and backwater designs. Chutes and backwaters were surveyed from August through November 2011, June through November 2012, and May through October 2013. During the 2011 surveys, high water was present at all sites because of the major flooding on the Missouri River. The hydrographic survey data are published along with this report in comma-separated-values (csv) format with associated metadata. Hydrographic surveys included bathymetric and Real-Time Kinematic Global Navigation Satellite System surveys. Hydrographic data were collected along transects extending across the channel from top of bank to top of bank. Transect segments with water depths greater than 1 meter were surveyed using a single-beam echosounder to measure depth and a differentially corrected global positioning system to measure location. These depth soundings were converted to elevation using water-surface-elevation information collected with a Real-Time Kinematic Global Navigation Satellite System. Transect segments with water depths less than 1 meter were surveyed using Real-Time Kinematic Global Navigation Satellite Systems. Surveyed features included top of bank, toe of bank, edge of water, sand bars, and near-shore areas. Discharge was measured at chute survey sites, in both the main channel of the Missouri River upstream from the chute and the chute. Many chute entrances and control structures were damaged by floodwater during the 2011 Missouri River flood, allowing a larger percentage of the total Missouri River discharge to flow through the chute than originally intended in the chute design. Measured discharge split between the main channel and the chute at most chutes was consistent with effects of the 2011 Missouri River flood damages and a larger percent of the total Missouri River discharge was flowing through the chute than originally intended. The U.S. Army Corps of Engineers repaired many of these chutes in 2012 and 2013, and the resulting hydraulic changes are reflected in the discharge splits.

Iowa, Missouri, Nebraska↗

USGS2024

How much trapping effort is needed for early detection of European green crab?

We present a case study using trapping data and species accumulation theory to assess the sampling effort needed to detect species that are rare in habitats sampled as part of the management of invasive European green crab Carcinus maenas on the coast of Washington State and Salish Sea shorelines, such as is desired for early detection of invasive species. In response to detections of green crab on the west coast of North America monitoring efforts, including early detection monitoring, have increased. The goal of invasive species early detection monitoring programs is to detect new infestations soon after introduction so that eradication and quarantine measures can be used to control their spread. However, detection of newly introduced invasive species often occurs after populations are large and well established. The ability to detect newly introduced invasive species is affected by sampling procedures, including how much effort is expended. To assess the level of trapping effort needed to detect green crab and other taxa when they are rare, we calculate sample-based rarefaction curves, total species richness, and estimates of sample completeness. We then use these estimates to describe the relationship between sampling effort and detection at two different spatial scales. Our results suggest that high probability early detection of green crabs or other rare taxa in many coastal waterbodies will require significantly more trapping effort than was expended in 2020. Our analyses further suggest that the effort required to provide for early detection was less at the site-specific spatial scale than at the waterbody scale. However, sample completeness at the site-specific spatial scale was negatively correlated with species richness. Current efforts to look for new green crab populations and to manage existing populations provide an opportunity to look for other invasive organisms that may establish in similar habitats.

Washington↗

USGS1999

Terrestrial predator alarm vocalizations are a valid monitor of stress in captive brown capuchins (Cebus apella)

The vocal behavior of captive animals is increasingly exploited as an index of well-being. Here we show that the terrestrial predator alarm (TPA) vocalization, a robust and acoustically distinctive anti-predation vocal response present in many mammal and bird species, offers useful information on the relative well-being and stress levels of captive animals. In a 16-week experiment evaluating the effects of varying levels of physical environmental enrichment (control < toys < foraging box < foraging box and toys) in the cages of eight singly housed adult male brown capuchins, we quantified the 1) emission rate of TPAs, 2) proportions of normal and abnormal behavior sample intervals, and 3) fecal and plasma cortisol levels. Variation in TPA emission across the experimental conditions was significant. We found significant reductions in the mean TPA production rate by the group in the enriched (toys, foraging box, and foraging box and toys) compared to the control condition; pre- and post-experimental conditions, however, did not differ from the control condition. Mean TPA production by the group was also significantly positively correlated to mean group levels of fecal cortisol and proportion of abnormal behavior sample intervals, and significantly negatively correlated to the average proportion of normal behavior sample intervals in the group. Based on group means, plasma cortisol levels were positively, but not significantly, related to increasing TPA rate. At the level of the responses of an individual subject, however, the covariation between the vocal and non-vocal behavioral measures and the cortisol assays seldom attained significance. Nevertheless, the direction of the relationships among these parameters within individual subjects typically mirrored those correlations based on group means. At both the group mean and individual levels, our results are consistent with the interpretation that in conditions of low environmental enrichment the study subjects were more stressed, and therefore more reactive to the presence of a threatening terrestrial stimulus (human observer), than when in more enriched conditions. We suggest that protocols to evaluate the effectiveness of enrichment for captive species other than brown capuchins could also profitably exploit TPAs as a first-line monitor or as corroboratory evidence of current well-being.

Zoo Biology↗

USGS2013

Atmospheric propagation modeling indicates homing pigeons use loft-specific infrasonic ‘map’ cues

Results from an acoustic ray-tracing program using daily meteorological profiles are presented to explain ‘release-site biases’ for homing pigeons at three experimental sites in upstate New York where W. T. Keeton and his co-workers at Cornell University conducted extensive releases between 1968 and 1987 in their investigations of the avian navigational ‘map’. The sites are the Jersey Hill and Castor Hill fire towers, and another near Weedsport, where control pigeons from the Cornell loft vanished in random directions, in directions consistently >50 deg clockwise and in directions ∼15 deg clockwise from the homeward bearing, respectively. Because Cornell pigeons were disoriented at Jersey Hill whereas birds from other lofts were not, it is inferred that Jersey Hill lies within an acoustic ‘shadow’ zone relative to infrasonic signals originating from the Cornell loft’s vicinity. Such signals could arise from ground-to-air coupling of near-continuous microseisms, or from scattering of direct microbaroms off terrain features, both of which are initially generated by wave–wave interactions in the deep ocean. HARPA runs show that little or no infrasound from the loft area arrived at Jersey Hill on days when Cornell pigeons were disoriented there, and that homeward infrasonic signals could have arrived at all three sites from directions consistent with pigeon departure bearings, especially on days when these bearings were unusual. The general stability of release-site biases might be due to influences of terrain on transmission of the homeward signals under prevailing weather patterns, whereas short-term changes in biases might be caused by rapid shifts in atmospheric conditions.

New York↗

USGS2017

A decade of boreal rich fen greenhouse gas fluxes in response to natural and experimental water table variability

Rich fens are common boreal ecosystems with distinct hydrology, biogeochemistry and ecology that influence their carbon (C) balance. We present growing season soil chamber methane emission (F CH 4 ), ecosystem respiration (ER), net ecosystem exchange (NEE) and gross primary production (GPP) fluxes from a 9-years water table manipulation experiment in an Alaskan rich fen. The study included major flood and drought years, where wetting and drying treatments further modified the severity of droughts. Results support previous findings from peatlands that drought causes reduced magnitude of growing season F CH 4 , GPP and NEE, thus reducing or reversing their C sink function. Experimentally exacerbated droughts further reduced the capacity for the fen to act as a C sink by causing shifts in vegetation and thus reducing magnitude of maximum growing season GPP in subsequent flood years by ~15% compared to control plots. Conversely, water table position had only a weak influence on ER, but dominant contribution to ER switched from autotrophic respiration in wet years to heterotrophic in dry years. Droughts did not cause inter-annual lag effects on ER in this rich fen, as has been observed in several nutrient-poor peatlands. While ER was dependent on soil temperatures at 2 cm depth, F CH 4 was linked to soil temperatures at 25 cm. Inter-annual variability of deep soil temperatures was in turn dependent on wetness rather than air temperature, and higher F CH 4 in flooded years was thus equally due to increased methane production at depth and decreased methane oxidation near the surface. Short-term fluctuations in wetness caused significant lag effects on F CH 4 , but droughts caused no inter-annual lag effects on F CH 4 . Our results show that frequency and severity of droughts and floods can have characteristic effects on the exchange of greenhouse gases, and emphasize the need to project future hydrological regimes in rich fens.

Global Change Biology↗

USGS2014

The behavioural response of adult Petromyzon marinus to damage-released alarm and predator cues

Using semi‐natural enclosures, this study investigated (1) whether adult sea lamprey Petromyzon marinus show avoidance of damage‐released conspecific cues, damage‐released heterospecific cues and predator cues and (2) whether this is a general response to injured heterospecific fishes or a specific response to injured P. marinus . Ten replicate groups of 10 adult P. marinus , separated by sex, were exposed to one of the following nine stimuli: deionized water (control), extracts prepared from adult P. marinus , decayed adult P. marinus (conspecific stimuli), sympatric white sucker Catostomus commersonii , Amazon sailfin catfish Pterygoplichthys pardalis (heterospecific stimuli), 2‐phenylethylamine (PEA HCl) solution, northern water snake Nerodia sipedon washing, human saliva (predator cues) and an adult P. marinus extract and human saliva combination (a damage‐released conspecific cue and a predator cue). Adult P. marinus showed a significant avoidance response to the adult P. marinus extract as well as to C. commersonii , human saliva, PEA and the adult P. marinus extract and human saliva combination. For mobile P. marinus , the N. sipedon washing induced behaviour consistent with predator inspection. Exposure to the P. pardalis extract did not induce a significant avoidance response during the stimulus release period. Mobile adult female P. marinus showed a stronger avoidance behaviour than mobile adult male P. marinus in response to the adult P. marinus extract and the adult P. marinus extract and human saliva combination. The findings support the continued investigation of natural damage‐released alarm cue and predator‐based repellents for the behavioural manipulation of P. marinus populations in the Laurentian Great Lakes.

Journal of Fish Biology↗

USGS2019

Individual behaviour and resource use of thermally stressed brook trout Salvelinus fontinalis portend the conservation potential of thermal refugia

Individual aggression and thermal refuge use were monitored in brook trout Salvelinus fontinalis in a controlled laboratory to determine how fish size and personality influence time spent in forage and thermal habitat patches during periods of thermal stress. On average, larger and more exploratory fish initiated more aggressive interactions and across all fish there was decreased aggression at warmer temperatures. Individual personality did not explain changes in aggression or habitat use with increased temperature; however, larger individuals initiated comparatively fewer aggressive interactions at warmer temperatures. Occupancy of forage patches generally declined as ambient stream temperatures approached critical maximum and fish increased thermal refuge use, with a steeper decline in forage patch occupancy observed in larger fish. These findings suggest that larger individuals may be more vulnerable to stream temperature rise. Importantly, even at thermally stressful temperatures, all fish periodically left the thermal refuge to forage. This indicates that the success of refugia at increasing population survival during periods of stream temperature rise may depend on the location of thermal refugia relative to forage locations within the larger habitat mosaic. These results provide insights into the potential for thermal refugia to improve population survival and can be used to inform predictions of population vulnerability to climate change.

Journal of Fish Biology↗

USGS2019

The dilemma of pest suppression in the conservation of endangered species

In the conservation of endangered species, active suppression of a population of one native species to benefit another native species poses particular challenges. Obvious examples include predator control and nest parasite reduction. Less obvious is the control of blood-feeding arthropods. We present a case study on the effect of blood-feeding black flies (Simulium spp.) on reintroduced Whooping Cranes (Grus americana). Our intent is to provide a transferrable, science-driven approach for determining the effects of blood-feeding arthropods on endangered vertebrates, and demonstrate an approach for guiding selection of management actions for managers faced with competing objectives. A multi-year experiment demonstrated that black flies reduce nest success in reintroduced cranes by driving the birds off their nests during incubation. Deciding how to respond, however, is complicated because the target black flies are native species that serve important ecological functions. We suggest that a decision-analytic approach can inspire the development of creative management alternatives and facilitate a transparent process that evaluates trade-offs among competing objectives. Recognizing that these decisions involve trade-offs, which must be weighed in the context of each case, is crucial to identifying alternatives that best balance multiple management objectives. Given the uncertainty about the population dynamics of blood-feeding arthropods, an adaptive management approach will offer substantial benefits.

Wisconsin↗

USGS2019

Effects of exercise and bioprocessed soybean meal diets during rainbow trout rearing

Background: Alternative protein sources to fishmeal in fish feeds are needed. Objectives: Evaluate rearing performance of adult rainbow trout (Oncorhynchus mykiss) (initial weight 139.0 ±1.5 g, length 232.9 ± 0.8 mm, mean ± SE) fed one of the two isonitrogenous and isocaloric diets (46% protein, 16% lipid) and reared at one of the two levels of exercise (water velocities of either 3.6 cm/s or 33.2 cm/s). Methods: Protein in the control diet was based on fishmeal. In the experimental diet, bioprocessed soybean meal replaced approximately 60% of the fishmeal. Fish were fed by hand once-per-day to near satiation, and the food was increased daily. The experiment lasted 90-days. Results: There were no significant differences in gain, percent gain, or specific growth rate between the dietary treatments. However, the amount of food fed and feed conversion ratio was significantly lower in the 60% bioprocessed soybean meal diet. Intestinal morphology, relative fin length, splenosomatic index, hepatosomatic index, and viscerosomatic index were not significantly different in the trout fed either diet. Fish reared at 3.6 cm/s had a significantly lower feed conversion ratio (1.02 ± 0.02) than fish reared at 33.2 cm/s (1.13 ± 0.02). However, there were no significant differences in gain, percent gain, specific growth rate, or percentage mortality in fish reared with or without exercise. No significant interactions were observed between diet and exercise (higher water velocity). Conclusion:Based on these results, at least 60% of the fishmeal in adult rainbow trout diets can be replaced by bioprocessed soybean meal, even if higher water velocities are used to exercise the fish.

The Open Biology Journal↗

USGS2000

Cassin's Sparrow (Aimophila cassinii) status assessment and conservation plan

Executive Summary Cassin’s Sparrow ( Aimophila cassinii ) is a grassland species endemic to the southwestern U.S. and northern Mexico. Its behavior and ecology have been shaped by these arid ecosystems and the health of its populations is dependent on the availability of grasslands that contain a shrub component. Populations of many grassland birds have experienced dramatic declines due to the loss and deterioration of grassland habitats, and there has been concern about the trends in Cassin’s Sparrow populations. Without better information about population trends, ecology, and effects of management activities, and without a stronger emphasis on grassland management, Cassin’s Sparrows and other grassland species may continue to experience declines. Little information exists about historic Cassin’s Sparrow population levels, and current population estimates for states in the breeding range are unknown. Significant survey-wide declines are documented by the Breeding Bird Survey (BBS) between 1966 and 1996. However, closer examination of these data suggest that the survey-wide trends are driven by population declines in the Edwards Plateau and South Texas Brushlands in Texas. No other areas within the core of its range or on the periphery show consistent, significant trends. In fact, there is consensus that in the core of its range in New Mexico Cassin’s Sparrow remains the most abundant breeding bird in grasslands with a shrub component. Understanding of population patterns in this species is complicated by large yearly fluctuations in distribution and numbers at any particular location, apparently in response to precipitation. This is particularly obvious in the periphery of its range. These dramatic fluctuations have hampered a clear assessment of population status, and our understanding has been confounded by the fact that the timing of BBS data collection does not always coincide with the peak breeding season of this species. The lack of information about the Cassin’s Sparrow’s status, ecology, and response to management activities, and the apparent declines indicated by BBS data, have been cause for concern. Habitat disturbance and degradation, mainly due to grazing and rangeland management practices such as shrub control, fire management, and planting of exotics, pose threats to Cassin’s Sparrow populations, as does habitat conversion through suburban development and agriculture. There is evidence that heavy grazing negatively affects populations, but the information is primarily available from the southwestern portion of its range (Arizona) and may not be applicable throughout the Cassin’s Sparrow’s entire range. Any management practice that results in complete removal of the shrub component, or loss of grass cover and an increase in shrub density beyond a threshold preferred by the species, also poses a threat. Lack of standardized or coordinated studies of Cassin’s Sparrow ecology and response to management practices in different geographic portions of its range has made it difficult to assess its status and make specific management recommendations. Limited data are available from the wintering grounds, and from its range (both breeding and wintering) in Mexico. The greatest needs are for determining of the causes of significant declines where they occur, determining of the effects of various management activities on Cassin’s Sparrow throughout its range, improved assessments of population and trends, and a better understanding of the annual population and distribution dynamics of this species, which shows such dramatic annual distributional fluctuations.

Wyoming, Nebraska, Kansas, Oklahoma,Texas, New Mex↗

USGS2007

Habitat alteration increases invasive fire ant abundance to the detriment of amphibians and reptiles

Altered habitats have been suggested to facilitate red imported fire ant (Solenopsis invicta) colonization and dispersal, possibly compounding effects of habitat alteration on native wildlife. In this study, we compared colonization intensity of wood cover boards by S. invicta among four forest management treatments in South Carolina, USA: an unharvested control (>30 years old); a partially thinned stand; a clearcut with coarse woody debris retained; and a clearcut with coarse woody debris removed. Additionally, we compared dehydration rates and survival of recently metamorphosed salamanders (marbled salamanders, Ambystoma opacum, and mole salamanders, A. talpoideum) among treatments. We found that the number of wood cover boards colonized by S. invicta differed significantly among treatments, being lowest in the unharvested forest treatments and increasing with the degree of habitat alteration. Salamanders that were maintained in experimental field enclosures to study water loss were unexpectedly subjected to high levels of S. invicta predation that differed among forest treatments. All known predation by S. invicta was restricted to salamanders in clearcuts. The amount of vegetative ground cover was inversely related to the likelihood of S. invicta predation of salamanders. Our results show that S. invicta abundance increases with habitat disturbance and that this increased abundance has negative consequences for amphibians that remain in altered habitats. Our findings also suggest that the presence of invasive S. invicta may compromise the utility of cover boards and other techniques commonly used in herpetological studies in the Southeast. ?? 2007 Springer Science+Business Media B.V.

Biological Invasions↗

USGS1988

Food availability controls seasonal cycle of growth in Macoma balthica (L.) in San Francisco Bay, California

A 2-yr field study of growth in the bivalve Macoma balthica (L.) at four locations in San Francisco Bay, California, U.S., showed that the timing and rate of growth (increase in shell length) were related to food supply. This clam feeds on both planktonic and benthic microalgae, depending on availability. Growth was apparently food-limited during some months, during one year more than the other, and at some locations more than others. Tissue-weight changes were also related to food availability. The heaviest animals were found in that year and at those locations with the highest chl a concentrations. Tissue-weight gains usually coincided with increased shell-growth rate or with reproductive development, although some large animals showed weight gain independent of both of these factors during periods with mid-range chl a levels. Weight losses coincided with spawning or periods of low growth rate, except at one station where, during a period when most animals were reproductively ripe, food concentrations were high, and shell growth was rapid, animals lost weight. This study failed to show a relation between salinity and the timing or rate of change of either shell length or tissue weight. The mild temperatures (10-23 ??C water temperature) of the area studied resulted in no growth inhibition due to low temperature, but there was some indication that the high air temperatures found in these intertidal areas limited growth rates. ?? 1988.

Journal of Experimental Marine Biology and Ecology↗

USGS2014

Genetic analysis of invasive Asian Black Carp ( Mylopharyngodon piceus ) in the Mississippi River Basin: evidence for multiple introductions

Invasive Asian Black Carp ( Mylopharyngodon piceus ) have been present in USA aquaculture facilities since the 1980s and wild Black Carp have been found in the Mississippi River Basin since the early 1990s. This study characterizes the genetic diversity and relatedness of the Basin’s Black Carp and clarifies the introduction history. Analyses focused on three mitochondrial markers (control region, cytochrome- b , and 16S) and seven nuclear microsatellite markers ( nDNA ), using aquaculture and wild-caught samples collected in the upper and lower Mississippi Basin. Of the three mitochondrial haplotypes, two were shared between the aquaculture and wild populations, while a third was only present in upper Mississippi wild-caught specimens. Due to the presence of diploid and triploid fish, microsatellite markers were scored as pseudodominant and revealed low polymorphism (N A = 4.6, N A Ave = 1.5). Nuclear Bayesian clustering analyses identified two genetically distinct groups and four subclusters, each primarily composed of a unique haplotype. Samples from three aquaculture farms were assigned to group 1, while a fourth farm included samples from both groups 1 and 2. Wild-caught fish from the upper Basin were predominantly group 1, whereas wild samples from the lower Mississippi were assigned to both genetic groups. The presence of divergent haplotypes and distinct nDNA groups, along with geographic distribution patterns, indicate that wild populations in the basin likely resulted from multiple introductions. Genetic similarities between wild and captive populations support claims that aquaculture is the introduction source, but a shortage of samples and a history of repeated transfers among facilities obscure the precise pathway.

Mississippi River Basin↗

USGS2017

Divergence and gene flow in the globally distributed blue-winged ducks

The ability to disperse over long distances can result in a high propensity for colonizing new geographic regions, including uninhabited continents, and lead to lineage diversification via allopatric speciation. However, high vagility can also result in gene flow between otherwise allopatric populations, and in some cases, parapatric or divergence-with-gene-flow models might be more applicable to widely distributed lineages. Here, we use five nuclear introns and the mitochondrial control region along with Bayesian models of isolation with migration to examine divergence, gene flow, and phylogenetic relationships within a cosmopolitan lineage comprising six species, the blue-winged ducks (genus Anas), which inhabit all continents except Antarctica. We found two primary sub-lineages, the globally-distributed shoveler group and the New World blue-winged/cinnamon teal group. The blue-winged/cinnamon sub-lineage is composed of sister taxa from North America and South America, and taxa with parapatric distributions are characterized by low to moderate levels of gene flow. In contrast, our data support strict allopatry for most comparisons within the shovelers. However, we found evidence of gene flow from the migratory, Holarctic northern shoveler (A. clypeata) and the more sedentary, African Cape shoveler (A. smithii) into the Australasian shoveler (A. rhynchotis), although we could not reject strict allopatry. Given the diverse mechanisms of speciation within this complex, the shovelers and blue-winged/cinnamon teals can serve as an effective model system for examining how the genome diverges under different evolutionary processes and how genetic variation is partitioned among highly dispersive taxa.

Journal of Avian Biology↗

USGS2008

Are hotspots of evolutionary potential adequately protected in southern California?

Reserves are often designed to protect rare habitats, or "typical" exemplars of ecoregions and geomorphic provinces. This approach focuses on current patterns of organismal and ecosystem-level biodiversity, but typically ignores the evolutionary processes that control the gain and loss of biodiversity at these and other levels (e.g., genetic, ecological). In order to include evolutionary processes in conservation planning efforts, their spatial components must first be identified and mapped. We describe a GIS-based approach for explicitly mapping patterns of genetic divergence and diversity for multiple species (a "multi-species genetic landscape"). Using this approach, we analyzed mitochondrial DNA datasets from 21 vertebrate and invertebrate species in southern California to identify areas with common phylogeographic breaks and high intrapopulation diversity. The result is an evolutionary framework for southern California within which patterns of genetic diversity can be analyzed in the context of historical processes, future evolutionary potential and current reserve design. Our multi-species genetic landscapes pinpoint six hotspots where interpopulation genetic divergence is consistently high, five evolutionary hotspots within which genetic connectivity is high, and three hotspots where intrapopulation genetic diversity is high. These 14 hotspots can be grouped into eight geographic areas, of which five largely are unprotected at this time. The multi-species genetic landscape approach may provide an avenue to readily incorporate measures of evolutionary process into GIS-based systematic conservation assessment and land-use planning.

Biological Conservation↗

USGS2003

A comparison of visual prey detection among species of piscivorous salmonids: Effects of light and low turbidities

Differences in reaction distance to prey fish by piscivorous salmonids can alter predator–prey interactions under different visual conditions. We compared reaction distances of three piscivorous salmonids commonly found in western lakes: cutthroat trout, Oncorhynchus clarki utah , rainbow trout, O. mykiss , and the nonnative lake char, Salvelinus namaycush . Reaction distances to salmonid prey were measured as functions of light and turbidity in a controlled laboratory setting. In addition, predation rates and swimming speeds of lake char preying on juvenile cutthroat trout were measured experimentally under a range of light levels. Reaction distances for cutthroat trout and rainbow trout increased rapidly as light levels increased, reaching relatively constant reaction distances at higher light levels. Reaction distances for lake char were similar to cutthroat trout and rainbow trout at the lower light levels; however, lake char reaction distances continued to increase with increasing light intensity to asymptote at distances 65% higher than those for both cutthroat and rainbow trout. Predation rates by lake char were low for the darkest light levels, increased rapidly under low light levels (0.50–0.75 lx), and then declined to an intermediate rate at all higher light levels. Swimming speeds by lake char also increased rapidly from extremely low light conditions to a peak and declined to an intermediate level at light levels above 1.00 lx. These results suggest that, above the saturation intensity threshold, piscivorous lake char react to fish prey at greater distances than do cutthroat trout and rainbow trout. These differences may help explain the decline of native trout following the introductions of nonnative lake char in lakes and reservoirs of western North America.

Environmental Biology of Fishes↗

USGS2021

Warming induces divergent stomatal dynamics in co-occurring boreal trees

Climate warming will alter photosynthesis and respiration not only via direct temperature effects on leaf biochemistry but also by increasing atmospheric dryness, thereby reducing stomatal conductance and suppressing photosynthesis. Our knowledge on how climate warming affects these processes is mainly derived from seedlings grown under highly controlled conditions. However, little is known regarding temperature responses of trees growing under field settings. We exposed mature tamarack and black spruce trees growing in a peatland ecosystem to whole-ecosystem warming of up to +9°C above ambient air temperatures in an ongoing long-term experiment (SPRUCE: Spruce and Peatland Responses Under Changing Environments). Here, we report the responses of leaf gas exchange after the first two years of warming. We show that the two species exhibit divergent stomatal responses to warming and vapor pressure deficit. Warming of up to 9°C increased leaf N in both spruce and tamarack. However, higher leaf N in the warmer plots translate into higher photosynthesis in tamarack but not in spruce, with photosynthesis being more constrained by stomatal limitations in spruce than in tamarack under warm conditions. Surprisingly, dark respiration did not acclimate to warming in spruce, and thermal acclimation of respiration was only seen in tamarack once changes in leaf N were considered. Our results highlight how warming can lead to differing stomatal responses to warming in co-occurring species, with consequent effects on both vegetation carbon and water dynamics.

Global Change Biology↗