16 research outputs found

    Developmental Failure and Loss of Reproductive Capacity as a Factor in Extinction: A Nine-Year Study of Dedeckera Eurekensis (Polygonaceae)

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    Many long-lived perennial species exhibit lowered reproductive capacity. Early studies of reproductive success in Dedeckera eurekensis (Polygonaceae) demonstrated that the species exhibited extremely low reproductive success, low seed/ovule (S/O) ratios (i.e., the percentage of ovules that produce filled seeds; 2.5 %), low germinability of filled seeds (3.5%), low seedling survivorship (11 .1%), and lack of recruitment in natural populations. These results were attributed to genetic load, but this elicited controversy, prompting long-term studies of the relationship between the S/O ratio and environment. After nine years of monitoring, however, the S/O ratio had not changed significantly (2 .7%), and there was no significant correlation between precipitation and the S/O ratio. Controlled field experiments demonstrated that neither resource availability nor other ecological factors significantly influenced embryo abortion rates. Controlled self-pollinations (N = 115) matured only one questionably filled seed, whereas intrapopulation cross-pollinations (N = 192) produced significantly more seed (S/O = 12.0 %). Previous pollination studies demonstrated that the species has no primary pollinators and is only rarely visited by a few generalist insects. However, the flowers typically self-pollinate in 2—3 days following anthesis. Strong inference suggests that the loss of reproductive capacity in D. eurekensis may be the result of inbreeding depression due to the superimposition of self-pollination on a normally outcrossed species carrying a high genetic/segregational load

    Nonnative Ungulate Impacts on Greater Sage-grouse Late Brood-rearing Habitat in the Great Basin, USA

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    Domestic livestock grazing is the dominant land use on much of the current range inhabited by greater sage-grouse (Centrocercus urophasianus; sage-grouse) in the western United States. Nonnative feral horses (Equus ferus caballus) also inhabit important sage-grouse seasonal habitats. Overabundant feral horse populations and improper grazing by domestic cattle (Bos taurus) can impact the health of sagebrush (Artemisia spp.) and desert shrub rangeland communities and native wildlife. These impacts to sage-grouse can be exacerbated when they affect late brood-rearing habitat, which provide the forbs and arthropods required to fledge broods. Managers require better information regarding the extent of these impacts. In 2020, we assessed the potential impact of feral horses and domestic cattle on sage-grouse late brood-rearing habitats in western Utah and eastern Nevada, USA. We acquired late brood-rearing location data from sage-grouse marked with global positioning system and very-high frequency radio-transmitters from 2016 to 2020 for North Utah data, 2017 to 2018 for South Utah data, and 1961 to 2017 for both east and west Nevada data to delineate late brood-rearing habitats. Using these location data, we compared 8 sites (4 pairs) within horse and non-horse use areas to assess sage-grouse habitat quality characteristics between areas that have been predominantly horse and cattle grazed versus sites that have been predominantly cattle grazed. For each pairing, 1 site was located within and the other outside of a Bureau of Land Management herd management area boundary, and both sites shared similar habitat characteristics (i.e., topography, dominant vegetation, soils, and climate) and selection probability for broods. We collected vegetation and dung count data at each site to assess characteristics related to habitat quality for sage-grouse brood-rearing, based on ungulate presence. We used a mixed model analysis of variance to detect differences between each paired site comparison (α \u3c 0.01). Horses or evidence of horse presence (i.e., dung) were not detected at our non-horse sites allowing for an unbiased comparison between paired sites. Cattle presence was noted at all our paired sites. Average annual grass frequency was 0.74 in horse and 0.17 in non-horse use areas (P = 0.20), and average annual grass cover was 4.0% compared to 0.2% in horse use areas (P = 0.32). Average annual grass biomass was 0.45 kg/ha in horse and 0.04% in non-horse use areas (P = 0.34). Vegetation height was 44.2 cm in non-horse compared to 34.5 cm in horse use areas (P = 0.23). These results suggest that increased ungulate grazing and year-long use of late brood-rearing habitat by feral horses coupled with livestock grazing may impair habitat suitability, particularly considering ecological impacts from invasive plant species. Our results suggest that managing late brood-rearing habitats to reduce the frequency and intensity of year-long grazing by feral horses can be best accomplished by reducing horse numbers and the seasonal distribution of grazing by domestic livestock

    HABITAT REQUIREMENTS FOR ERIGERON KACHINENSIS, A RARE ENDEMIC OF THE COLORADO PLATEAU

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    Volume: 54Start Page: 193End Page: 20

    The Discovery of Great Basin Bristlecone Pine, Pinus Longaeva

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    An analysis of human–black bear conflict in Utah

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    Conflict between black bears (Ursus americanus) and humans has occurred in Utah, but the records are largely incomplete. To document these events, the Utah Division of Wildlife Resources initiated a black bear sightings and encounters database in 2003, and we updated it. From 2003–2013, there were 224 recorded events, with 10 attacks, 208 property damages, and 6 vehicle collisions. Most events took place at campsites (40%). The most common season for events was summer (78%). Most conflict occurred at night. The number of events has not increased over the last 10 years, with no significant relationship between the number of events per year and drought. Most events involved single bears, and over half of events occurred when food or garbage was available for the bear

    A Practical Assessment of Using sUASs (Drones) to Detect and Quantify Wright Fishhook Cactus (Sclerocactus wrightiae L.D. Benson) Populations in Desert Grazinglands

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    Obtaining accurate plant population estimates has been integral in listing, recovery, and delisting species under the U.S. Endangered Species Act of 1973 and for monitoring vegetation in response to livestock grazing. Obtaining accurate population estimates remains a daunting and labor-intensive task. Small unmanned aircraft systems (sUASs or drones) may provide an effective alternative to ground surveys for rare and endangered plants. The objective of our study was to evaluate the efficacy of sUASs (DJI Phantom 4 Pro) for surveying the Wright fishhook cactus (Sclerocactus wrightiae), a small (1–8 cm diameter) endangered species endemic to grazinglands in the southwest desert of Utah, USA. We assessed sUAS-based remotely sensed imagery to detect and count individual cacti compared to ground surveys and estimated optimal altitudes (10 m, 15 m, or 20 m) for collecting imagery. Our results demonstrated that low altitude flights provided the best detection rates (p < 0.001) and counts (p < 0.001) compared to 15 m and 20 m. We suggest that sUASs can effectively locate cactus within grazingland areas, but should be coupled with ground surveys for higher accuracy and reliability. We also acknowledge that these technologies may have limitations in effectively detecting small, low-growing individual plants such as the small and obscure fishhook cactus species

    Data from: Weaving a tangled web: divergent and reticulate speciation in Boechera fendleri sensu lato (Brassicaceae: Boechereae)

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    Hybrid speciation is relatively common in plants compared to other well-studied groups. Polyploidy and apomixis are strongly associated with hybrid speciation, presumably due to the opportunities they provide for both reestablishing reproductive function in hybrids with incomplete chromosomal homology and creating rapid reproductive isolation in sympatry. Boechera, a species-rich genus closely related to Arabidopsis, is a particularly fertile ground for the study of hybrid speciation. Thirty-eight apomictic triploid hybrid species are currently recognized in Boechera. Recent research has shown that apomictic diploid hybrids, although very rare in angiosperms, are common in Boechera. Given this complexity, focused studies of individual species complexes are critical to understanding speciation and diagnosing biodiversity in Boechera. Here we analyze DNA sequences from seven nuclear loci and multilocus genotypes from 15 microsatellite markers in a group of closely related taxa formerly included in B. fendleri. Our results support the recognition of four species previously segregated from B. fendleri s. l., including three genetically distinct, sexual diploids (B. fendleri, B. spatifolia, and B. texana) and one apomictic triploid hybrid (B. porphyrea). We also identify four novel apomictic diploid hybrid species (B. carrizozoensis, B. centrifendleri, B. sanluisensis, and B. zephyra) and additional apomictic triploid hybrids. Our results reveal a complex network of relationships. Sexual diploid species can hybridize to form apomictic diploids, and members of these two groups can hybridize to form trigenomic, apomictic triploids

    Data from: Does hybridization drive the transition to asexuality in diploid Boechera?

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    Gametophytic apomixis is a common form of asexual reproduction in plants. Virtually all gametophytic apomicts are polyploids, and some view polyploidy as a prerequisite for the transition to apomixis. However, any causal link between apomixis and polyploidy is complicated by the fact that most apomictic polyploids are allopolyploids, leading some to speculate that hybridization, rather than polyploidy, enables apomixis. Diploid apomixis presents a rare opportunity to isolate the role of hybridization, and a number of diploid apomicts have been documented in the genus Boechera (Brassicaceae). Here we present the results of a microsatellite study of 1393 morphologically and geographically diverse diploid individuals, evaluating the hypothesis that diploid Boechera apomicts are hybrids. This genus-wide dataset was made possible by the applicability of a core set of microsatellite loci in 69 of the 70 diploid Boechera species and by our ability to successfully genotype herbarium specimens of widely varying ages. With few exceptions, diploid apomicts exhibited markedly high levels of heterozygosity resulting from the combination of disparate genomes. This strongly suggests that most apomictic diploid Boechera lineages are of hybrid origin, and that the genomic consequences of hybridization allow for the transition to gametophytic apomixis in this genus

    Alexander-etal_Boechera-fendleri-sensu-lato_data

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    Specimen citations, GenBank accessions for novel sequence data (locus: pistillata; cloned from hybrid members of Boechera fendleri sensu lato), and complete microsatellite data (15 nuclear microsatellite loci from 374 individuals) for molecular systmatic investigation of Boechera fendleri sensu lato
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