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A methodology was developed to assess the impacts of the historic 2013–2014 drought on ecosystems of California's Central Coast region, using a combination of satellite image analysis and in situ measurements of soil moisture in predominant vegetation types of the region. According to differences in Landsat drought indices for plant water stress and vegetation green cover (NDWI and NDVI, respectively), the geographic areas within the study region that were most severely impacted by the 2013 drought were the inland Carmel Valley in northern Monterey County and the coastal zones around San Simeon Point and Cambria in northern San Luis Obispo County. An expanded area of severe vegetation moisture stress, generally indicated by relative-differenced NDWI values of >400, was detected by May 2014 in both of these same geographic areas. For more detailed examination of drought impacts, the entire study region was separated into the 3 predominant vegetation types (grasslands, shrublands, and forests) to examine changes in Landsat NDWI and NDVI in the context of differing plant community responses to severe drought. Results confirmed that higher overall drought stress in 2013 and 2014 was detected in grasslands, compared to shrublands and forests, in both years at all elevations and slopes >200 m and >5%, respectively.
The cutthroat trout (Oncorhynchus clarkii) is a popular sport fish that is native to the waters of western North America. Cutthroat trout comprises many subspecies, each of which has experienced range reduction resulting from anthropogenic activities. Hence, there is a general interest from management agencies to assess the genetic structure of managed populations of cutthroat trout subspecies to ensure that proper conservation plans are implemented. Herein, we utilize microsatellite data to characterize the genetic composition of 2 populations of Bonneville cutthroat trout in Great Basin National Park: Mill Creek and South Fork Big Wash. Mill Creek was used as a source population for reintroduction into South Fork Big Wash in the year 2000, and there is concern that South Fork Big Wash may have experienced a population bottleneck after, or during, the stocking effort. We found that both populations exhibit low genetic diversity, and that the source population, Mill Creek, exhibited mixed signals of having undergone a recent population bottleneck. Structure analysis revealed 4 distinct groups, but those groups did not segregate geographically, although a significant pairwise FST (0.06727, P < 0.00001) between Mill Creek and South Fork Big Wash populations suggests that some genetic differentiation has occurred.
Mature tree mortality rates are poorly documented in desert riparian woodlands. I monitored deaths and calculated annual survivorship probability (Ps) in 2 groups of large (27–114 cm DBH), old (≥40 years old) Fremont cottonwood (Populus fremontii Wats.) in a stand along the free-flowing Yampa River in semiarid northwestern Colorado. Ps = 0.993 year-1 in a group (n = 126) monitored over 2003–2013, whereas Ps = 0.985 year-1 in a group (n = 179) monitored over the same period plus 3 earlier years (2000–2003) that included drought and a defoliating insect outbreak. Assuming Ps was the same for both groups during the 10-year postdrought period, the data indicate that Ps = 0.958 year-1 during the drought. I found no difference in canopy dieback level between male and female survivors. Mortality was equal among size classes, suggesting Ps is independent of age, but published longevity data imply that either Ps eventually declines with age or, as suggested in this study, periods with high Ps are interrupted by episodes of increased mortality. Stochastic population models featuring episodes of low Ps suggest a potential for an abrupt decline in mature tree numbers where recruitment is low. The modeling results have implications for woodland conservation, especially for relictual stands along regulated desert rivers.
Bumble bees are important pollinators of flowering plants, foraging and providing pollination services throughout the growing season. They are adapted to cool temperatures and are among the most important of all pollinators at high elevations and northern latitudes. Over the past several decades, multiple species of bumble bees have experienced declines in both geographic range and abundance in Europe and North America, while 4 species of the genus Bombus (Bombus) have suffered dramatic declines in the United States. Such declines are not as evident in Alaska, and the status of Bombus remains relatively unknown in the adjacent territories of Canada. To begin addressing this knowledge gap, we sampled the bumble bee fauna foraging on floral patches along 5 highways of Canada and southeastern Alaska in a short-term, one-time survey during late summer 2010. We observed 14 species and found Bombus assemblages to be structured by broad geographic features and ecoregions. The Bombus species B. (B.) occidentalis and B. (B.) terricola were relatively abundant in sample sites west and east of the Rocky Mountains, respectively, and B. (Pyrobombus) vagans, B. (Cullumanobombus) rufocinctus, and B. occidentalis were the most abundant species across all sites.
Conservation of species requires accurate population estimates. We used genetic markers from feces to determine bighorn sheep abundance for a herd that was hypothesized to be declining and in need of population status monitoring. We sampled from a small but accessible portion of the population's range where animals naturally congregate at a natural mineral lick to test whether we could accurately estimate population size by sampling from an area where animals concentrate. We used mark-recapture analysis to derive population estimates, and compared estimates from this smaller spatial sampling to estimates from sampling of the entire bighorn sheep range. We found that estimates were somewhat comparable; in 2009, the mineral lick sample and entire range sample differed by 20 individuals, and in 2010 they differed by only one individual. However, we captured 13 individuals in the entire range sample that were not captured at the mineral lick, and thus violated a model assumption that all individuals had an equal opportunity of being captured. This eliminated the possibility of inferring a total population estimate from just animals visiting the mineral lick, but because estimates were relatively similar, monitoring at the mineral lick can provide a useful index for management and conservation. We compared our results to a radio-collar study conducted in 2003–2004 and confirmed that the population remained stable since 2004. Our population estimates were 78 (CI 62–114) in 2009 and 95 (CI 77–131) in 2010. Between 7 and 11 sampling dates were needed to achieve a CV of 20% for population estimates, assuming a capture probability between 0.09 and 0.13. We relied on citizen science volunteers to maximize data collection and reduce costs; 71% of all fecal samples were collected by volunteers, compared to 29% collected by paid staff. We conclude that our technique provides a useful monitoring tool for managers. The technique could be tested and applied in similar populations where animals congregate with high fidelity at a mineral lick or other area.
Desert almond, Prunus fasciculata (Rosaceae), is a Mojave Desert shrub that primarily produces male and female flowers on different plants. I investigated the plant's pollination by examining pollen loads on insects aspirated from female flowers on 3 dioecious shrubs, growing near male-flowering shrubs, at one locality in southern Nevada during March 2014. Pollen loads were analyzed on 9 species of Diptera in Bombyliidae, Syrphidae, Calliphoridae, and Tachinidae and 4 species of Hymenoptera in Andrenidae (all female Andrena). All but 4 of the 65 flies and 38 bees aspirated carried P. fasciculata pollen grains, recognized by their tricolpate shape in polar view and oblate shape in equatorial view. Two species of syrphid flies in Copestylum were frequently aspirated and carried high P. fasciculata pollen loads and moderate proportions of conspecific pollen. High conspecific pollen loads on the tachinid Chaetogaedia also indicated potential for pollinating P. fasciculata. Three of the 4 species of Andrena bees carried large amounts of P. fasciculata pollen. Conspecific pollen also comprised most of the pollen load on Andrena bees, suggesting high flower constancies to the plant. Pollinators of P. fasciculata would vary over the plant's range, and likely between years, because of the localized populations or narrow larval diets of many of the insects collected from flowers. The female desert almond shrubs examined in southern Nevada during 2014 appeared to be pollinated by a variety of native flies and bees, especially syrphid flies in Copestylum and andrenid bees in Andrena.
The Cuatro Ciénegas killifish Lucania interioris is an endemic fundulid in the Chihuahuan Desert valley of Cuatro Ciénegas, Coahuila, México. It occurs in 3 major drainage regions of the basin and is limited primarily to naturally fragmented and physicochemically severe habitats of the valley floor. We assessed mitochondrial DNA variation and population genetic structure in L. interioris from 8 populations representative of the entire geographic range of this species, including its distribution within and among major drainage regions (western, central, and southeastern) of the valley. Five populations were invariant, including both populations in the western region (Haplotype A only), whereas 2 haplotypes were observed in each of the remaining populations. Haplotype diversity was low in the central basin (HD = 0.10 and HD = 0.19) and moderate in the southeastern basin (HD = 0.52). Low levels of divergence among haplotypes (0.3%–0.9%), together with high levels of genetic differentiation among regions (FCT = 0.847, P < 0.001), indicate complete isolation among major drainage regions. These results agree with previous documentation of morphological differentiation between populations from the western and central basins. Populations in the southeastern basin are divergent genetically and, therefore, also may exhibit morphological distinction.
Our knowledge of the biology of lizards in the genus Xenosaurus has increased over the past 20 years. Several generalities appear to hold for these lizards; however, some traits appear to vary among populations and species of Xenosaurus. Here we report on the thermal ecology, sexual dimorphism, and diet of a population of the recently described Xenosaurus tzacualtipantecus from Hidalgo, Mexico. The mean body temperature (Tb) of X. tzacualtipantecus in our population (18.1 °C) is the lowest mean Tb yet observed in Xenosaurus. The close relationships between Tb and air temperatures (Ta) suggest that X. tzacualtipantecus is closer to the thermoconformer end of the thermoconformer-thermoregulator continuum. Females of X. tzacualtipantecus had greater snout—vent lengths than males, males had longer femurs than females, and there was no difference in head size between the sexes. Xenosaurus tzacualtipantecus consumes a variety of invertebrates, primarily insects, suggesting that it is an opportunistic or generalist predator. The diets of lizards in the wet season were dominated by caterpillars, whereas in the dry season beetles were more important. Our observations on the ecology and natural history of X. tzacualtipantecus are generally consistent with previous observations on similar traits in other Xenosaurus.
We compared 4 programs designed to identify species of bats from their echolocation calls (Bat Call ID, EchoClass, Kaleidoscope Pro, and SonoBat) using field data collected in Nebraska, USA (29,782 files). Although we did not know the true identity of these bats, we could still compare the pairwise agreement between software packages when identifying the same call sequences. If accuracy is high in these software packages, there should be high agreement in identification. Agreement in identification by species averaged approximately 40% and varied by software package, species, and data set. Our results are not consistent with the high accuracy often claimed by some software packages and may be a warning about the importance of understanding accuracy of acoustical identification in designing ecological experiments and interpreting results.
The helminth fauna of the bolson pupfish Cyprinodon atrorus (Osteichthyes: Cyprinodontidae) consisted of 7 helminth taxa collected from 7 localities of Cuatro Ciénegas, a natural area protected by the Mexican government in Coahuila, northern Mexico. The helminth community is described at the infracommunity and component community levels. The acanthoeephalan Atactorhynchus duranguensis was the most prevalent and abundant species. The remaining species were rare and found at low mean abundance values. The observed species richness, individual parasite abundance, and diversity were low at both component community and infracommunity levels. These findings are similar to those found in other freshwater fish species in the Nearctic part of Mexico; however, our study shows that the number of larval forms, in terms of species richness and abundance, is very low in comparison with previous studies in the area. Isolation of the Cuatro Ciénegas basin from the Bravo River (= Grande River) basins is suggested as the main factor determining the depauperate helminth assemblage. The low number of individual larval stages in this fish species is probably due to the lack of piscivorous birds in the area.
In 2001 and 2002, a study of many-lined skinks (Plestiodon multivirgatus) was conducted by Los Alamos National Laboratory biologists in north-central New Mexico to determine means and ranges for several morphological characters and to test for sexual dimorphism. Over both years, there were 539 new captures of many-lined skinks, which included 131 Hatchlings. The earliest hatchling capture was on 19 June and the latest capture was on 31 August. Hatchling captures peaked on 1 August in 2001 and 6 August in 2002. The age class, sex, snout—vent length (SVL), tail length (TL), mass, head length (HL), and head width (HW) were recorded and individuals were released at the point of capture. Our results indicate that the SVL, mass, HL, and HW did not exhibit sexual dimorphism. The sex ratio was skewed toward females in this study. It is not known whether the many-lined skink has sexual determination based on environmental factors, but the data here suggest that more research is needed. From these observations, we supplement the limited existing knowledge on the morphology of this species.
In July 2013, a unique type of movement was noted of cattle (Bos taurus) bones across the surface of Smith Creek Valley Playa, in central Nevada. Portions of 3 skeletal elements and 2 sections of articulated elements were found at the ends of shallow, linear, furrow-like trails inscribed in the playa surface. These trails, with their skeletal material, are similar to those produced by the phenomenon described as “racing” or “sailing rocks” that is best documented from Racetrack Playa in Death Valley, California. As has been recently observed for the rocks of Racetrack Playa, the material here was probably moved by a combination of wind acting on ice floating on liquid water. This is the first report of such movement of objects from Smith Creek Playa and represents a previously unreported mechanism for taphonomic transport of skeletal material.
We report the first photographic record of the white-nosed coati (Nasua narica) in the southeastern portion of the state of Guanajuato. Although this species is considered abundant and widely distributed in México, Guanajuato is not considered part of its current distribution. Because of the lack of records in surrounding areas, it is not possible to determine if there is an existing linkage to other populations. Thus, it is imperative to continue monitoring this species in the region to identify and assess the connectivity of other established populations and to ensure the species' long-term conservation.
We used remote video monitoring systems to document nest predators at San Clemente Bell's Sparrow (Artemisiospiza belli clementeae) nests and recorded an unexpected depredation by an island night lizard (Xantusia riversiana) on 22 May 2013. This record is the first documented case of a San Clemente Bell’s Sparrow being depredated by any reptile and is also the first documentation of any night lizard species (genus Xantusia) depredating a bird's nest. Additionally, we found that night lizards are among the smallest lizard species ever observed depredating a bird's nest.
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