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Phoradendron coryae (Viscaceae) is a dioecious, parasitic plant on oak trees and shrubs in Quercus (Fagaceae), and it occurs from Arizona to Texas and into northern Mexico. The species produces minute spherical flowers during summer. Dioecious flowering requires pollinating insects to carry pollen from male to female plants. I investigated the pollination of P. coryae parasitizing Quercus turbinella shrubs at 3 sites at different elevations in the Cerbat Mountains of northwestern Arizona during August–September 2015. I examined pollen from male flowers, aspirated insects landing on female flowers, and counted conspecific pollen grains carried by insects. The tricolpate pollen of P. coryae was semiangular to subangular in polar view and circular to depressed oval in equatorial view. Female flowers were visited by 2 species of Coleoptera in 2 families, 6 species of Diptera in 6 genera and 3 families, and 1 species of Hymenoptera. Insects on flowers were extremely small (most <3 mm in length), and nearly all (99%) of the pollen carried by insects was from P. coryae. Conspecific pollen was found on 67% of the insects identified. Pollen loads were low, with only 25% of the insects carrying ≥5 grains. The beetle Attalus futilis (Melyridae) was the most frequently aspirated species, comprising 71% of the insects collected and occurring at all 3 sites. Most A. futilis (64%) carried P. coryae pollen. The second most frequently collected insects were 2 species of Hippelates and Liohippelates flies (Chloropidae). The Liohippelates carried the most P. coryae pollen. Other insects with pollen included 2 additional species of Chloropidae, 2 species of flies in Tachinidae and Tephritidae, a species of beetle in Chrysomelidae, and a species of parasitic wasp in Figitidae. Phoradendron coryae appeared to be pollinated mostly by A. futilis beetles due to their apparent abundance and by Liohippelates flies due to their relatively high pollen loads.
Northern Bobwhite (Colinus virginianus) populations in Texas have been declining during the past several decades. Declines have been attributed to habitat loss, but other causes and potential contributing factors (e.g., parasites, disease) have been posited. Little is known about helminth parasites in bobwhites from Texas. Previous studies often used bobwhites collected during the hunting season, which only samples individuals that survive after the summer breeding season. Our objectives were to (1) assess the prevalence, intensity, and abundance of helminths in bobwhites from Fisher County, Texas, during an annual cycle; (2) identify which species are known to be pathogenic; and (3) determine whether infections are related to host age, sex, and season of collection. We collected 142 bobwhites during February–March 2010 (n = 37), August 2010 (n = 51), and December 2010–January 2011 (n = 54). We found 7 helminth species, of which 3 (Oxyspirura petrowi, Tetrameres pattersoni, and Dispharynx nasuta) are known to cause tissue damage to bobwhites. Aulonocephalus pennula was the most common (82% prevalence) and numerically abundant species (96% of all specimens). Prevalence and mean abundance of A. pennula, O. petrowi, and T. pattersoni were higher in adults than juveniles. Prevalence of A. pennula, O. petrowi, and T. pattersoni did not vary with host sex. Mean abundance of T. pattersoni was higher in females than males. Prevalence of A. pennula, O. petrowi, and T. pattersoni was lower in summer than early and late winter and was related to low infections in young juveniles. Our findings provide insight into helminth infection dynamics of Northern Bobwhites across an annual cycle.
Nitrogen (N) and phosphorus (P) cycling in lakes can be impacted by numerous abiotic and biotic factors. Large animals, such as birds and mammals, may recycle nutrients within a system or bring them in from surrounding habitats or different landscapes. Eared Grebes (Podiceps nigricollis) congregate in large numbers in the fall on the Great Salt Lake (GSL), Utah, and may have an important role in recycling nutrients from macroinvertebrates back into the water column. We evaluated the role of Eared Grebes in N and P cycling within the GSL by estimating the magnitude of their nutrient recycling capacity. We estimated Eared Grebe population size on the GSL over 5 years at 300,000 to over 4,300,000 birds. We used a previously published food intake model to estimate monthly recycling of N (5 to 300 tonnes) and P (0.4 to 25 tonnes). The maximum estimates of N and P loading by Eared Grebes are about 25% of nutrient recycling in the GSL caused by turnover in the water column. Eared Grebes may speed up nutrient recycling, making nutrients available to primary producers sooner. The contribution of waterbirds to nutrient cycling is important for the entire N and P cycles within the GSL.
Three taxa are recognized at the rank of species based on molecular phylogenetic studies in Phacelia sect. Glandulosae (Hydrophyllaceae, Boraginales). Results of those studies did not support a monophyletic Phacelia crenulata Torr. ex S. Watson, because 3 varieties of that species were supported as distinct lineages based on molecular (nuclear and chloroplast) and morphological characters. Typification and status is clarified for P. corrugata A. Nelson and P. orbicularis Rydb. A new nomenclatural combination for P. crenulata var. angustifolia N.D. Atwood is established to elevate that variety to species rank, as Phacelia angustifolia (N.D. Atwood) Walden, comb. et stat. nov.
Data on reproductive ecology of turtles in New Mexico are limited, and some species living there are among the least studied in the United States. We trapped 4 native species of turtles (Apalone spinifera, Chrysemys picta, Pseudemys gorzugi, and Trachemys gaigeae gaigeae) in the Rio Grande and Black River (Pecos River drainage) of New Mexico in June 2012 and 2013 to collect data on female reproductive ecology, including clutch size, egg size, timing of egg production, and percentage of gravid females. During our sampling, we found shelled eggs via X-radiography in only 3 native species: C. picta, P. gorzugi, and T. g. gaigeae. Clutch and egg sizes were within the range of previously reported values, although clutch size for P. gorzugi (10 eggs) is only the second published record for that data-deficient species. Clutch size increased with body size in T. g. gaigeae. We observed few differences between reproductive parameters for turtles in New Mexico and their conspecifics and congeners elsewhere in the United States, other than the observation that female C. picta may mature at smaller body sizes in New Mexico relative to other western populations elsewhere in its vast, primarily eastern North American range.
Big sagebrush (Artemisia tridentata Nutt.) ecosystems provide habitat for sagebrush-obligate wildlife species such as the Greater Sage-Grouse (Centrocercus urophasianus). The understory of big sagebrush plant communities is composed of grasses and forbs that are important sources of cover and food for wildlife. The grass component is well described in the literature, but the composition, abundance, and habitat role of forbs in these communities is largely unknown. Our objective was to synthesize information about forbs and their importance to Greater Sage-Grouse diets and habitats, how rangeland management practices affect forbs, and how forbs respond to changes in temperature and precipitation. We also sought to identify research gaps and needs concerning forbs in big sagebrush plant communities. We searched for relevant literature including journal articles and state and federal agency reports. Our results indicated that in the spring and summer, Greater Sage-Grouse diets consist of forbs (particularly species in the Asteraceae family), arthropods, and lesser amounts of sagebrush. The diets transition to sagebrush in fall and winter. Forbs provide cover for Greater Sage-Grouse individuals at their lekking, nesting, and brood-rearing sites, and the species has a positive relationship with arthropod presence. The effect of grazing on native forbs may be compounded by invasion of nonnative species and differs depending on grazing intensity. The effect of fire on forbs varies greatly and may depend on time elapsed since burning. In addition, chemical and mechanical treatments affect annual and perennial forbs differently. Temperature and precipitation influence forb phenology, biomass, and abundance differently among species. Our review identified several uncertainties and research needs about forbs in big sagebrush ecosystems. First, in many cases the literature about forbs is reported only at the genus or functional type level. Second, information about forb composition and abundance near lekking sites is limited, despite the fact that lekking sites are an important center of Greater Sage-Grouse activity. Third, there is little published literature on the relationship between forbs and precipitation and between forbs and temperature, thereby limiting our ability to understand potential responses of forbs to climate change. While there is wide agreement among Greater Sage-Grouse biologists that forbs are an important habitat component, our knowledge about the distribution and environmental responses of forb species in big sagebrush plant communities is limited. Our work for the first time synthesizes the current knowledge regarding forbs in sagebrush ecosystems and their importance for Greater Sage-Grouse and identifies additional research needs for effective conservation and management.
While many studies have addressed the effect of individual stresses on plant—plant associations, few have addressed the effects of co-occurring stresses. We therefore investigated how associations between Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) and 2 native grasses (Poa secunda and Elymus elymoides) responded to different combinations of grazing and moisture stresses in the Great Basin, USA. Positive (i.e., facilitative) interactions between nurse plants and their beneficiaries are predicted to increase with increasing moisture limitation and grazing stress, but these interactions may break down at extreme levels of stress. We hypothesized that (1) competitive interactions and negative shrub-grass spatial associations would occur under the least stressful conditions (low grazing intensity / high precipitation); (2) positive shrub-grass spatial associations would dominate at intermediate levels of stress (high grazing intensity / high precipitation and low grazing intensity / low precipitation); and (3) negative grass-shrub relationships would dominate at extreme levels of stress (high grazing / low precipitation). We sampled 5 site pairs (high vs. low grazing intensity) that occurred over a precipitation gradient. We assessed how abundance of the 2 grasses P. secunda and E. elymoides responded to sagebrush microsite (canopy vs. interspace), grazing intensity, and precipitation. We found that both grass species were positively associated with A. tridentata canopy microsites at low annual precipitation levels. However, grazing stress appeared to weaken this effect for P. secunda, indicating, as we predicted, a potential breakdown of facilitative interactions in highly stressful conditions. Although we predicted that facilitation would dominate in moderately stressful conditions, we only found this to be true (for both grasses) in one of the 2 moderately stressful scenarios (low grazing / low precipitation). Our results provide insights into how Great Basin plant communities may respond to the separate and combined effects of grazing and drought stresses, both of which may intensify in the future.
Managing fire for the conservation of biodiversity is a widespread challenge. An important disturbance mechanism in big sagebrush (Artemisia tridentata) communities, fire has well-known effects on vegetation structure but poorly described consequences for sagebrush wildlife communities. We estimated the abundance of small mammals in relation to fire history in mountain big sagebrush (A. t. ssp. vaseyana) communities by way of a chronosequence approach that included 3 wildfires and adjacent unburned areas. We compared patterns of mammal community succession with expectations of the habitat accommodation model by associating responses of mammals to change over time in vegetation structure. Burned study sites were at various stages of vegetation succession from 7 to 19 years following fire. Shrub canopy cover ranged from 9% to 36% and was not fully recovered on the plots at 19 years after fire. Only Belding's ground squirrel (Urocitellus beldingi) demonstrated a measurable response to fire that was consistent across all 3 burned study areas. Its density was approximately 10 times greater in burned areas relative to adjacent unburned habitat irrespective of the number of years since a burn occurred. Deer mouse (Peromyscus maniculatus) was more abundant on sites more recently burned than at sites closer to full vegetation recovery. Overall, effects of fire on small mammal abundance in this landscape were relatively small, did not closely match the expectations of the habitat accommodation model, and suggest that conservation of small mammal communities in fire-affected sagebrush landscapes can be influenced by habitat management at large spatial scales.
Within the last century, the floristic composition of riparian communities in the Southwest has drastically changed following introduction of the exotic tree Tamarix ramosissima. In an attempt to control Tamarix populations, the tamarisk leaf beetle (Diorhabda carinulata) has been utilized as a biological control agent. Three years of data collection at our study sites along Fountain Creek (Fountain, CO) allowed us to characterize the response of Tamarix to invasion by the biological control agent. In analyzing data collected before, during, and after the beetle invasion, we observed a significant effect of foliar herbivory on Tamarix physiology and life history strategy. Associations between flower number and functional traits changed before, during, and after the beetle invasion. Before the invasion, reproductively fit individuals exhibited high stomatal conductance and used relatively more water. During and after the invasion, fit plants had higher foliar chlorophyll content, but conductance was not significantly correlated with fecundity. Tamarix responded to defoliation by increasing water use, which may have been an attempt to sustain photosynthate allocation to reproductive structures. Therefore, the leaf beetle may increase the water use of Tamarix during the growing season.
The Sutter Buttes (Buttes) are a small, isolated mountain range in the Great Central Valley of California. Systematic study of the fauna and flora of this unique habitat has been limited by the private ownership of the entire mountain range. As a result, much of our knowledge about the herpetofauna of the Buttes is based on isolated observations and scattered museum records, most over 4 decades old. In this study, we present an updated inventory of the herpetofauna of the Buttes, based on a 2-year field survey within the boundaries of the first publicly protected property within the Buttes (Sutter Buttes State Park) and a comprehensive survey of museum specimens. The objective of this study was to develop a current herpetofaunal species list for the Buttes as a whole and the park specifically. We verify the occurrence of 16 previously identified herpetofaunal species within the park and provide evidence for 3 additional species. We also provide the first record of the widely invasive Pond Slider (Trachemys scripta); clarify the status of a previous misidentification of a federally threatened species, Giant Gartersnake (Thamnophis gigas); and provide evidence for the probable extirpation of 2 California Species of Special Concern, the Foothill Yellow-Legged Frog (Rana boylii) and Blainville's Horned Lizard (Phrynosoma blainvillii). Therefore, our species list for the Buttes includes 20 herpetofaunal species. Museum specimens from the Buttes are located at 8 museums, with the majority at the California State University, Chico Vertebrate Museum. Sixteen of the 22 herpetofauna species extant or recently extirpated from the Buttes are represented by museum vouchers, with only 11 having tissue samples. This study sets an updated baseline for the further study and monitoring that will be required to facilitate effective management and conservation of the unique Sutter Buttes.
In light of local population declines and poor calf survival, we investigated visual obstruction as potential elk (Cervus elaphus) calf hiding cover at birth sites. We hypothesized that female elk would use hiding cover (i.e., visual obstruction) in order to conceal their calves at the birth site and reduce vulnerability to predation. Selection of hiding cover has been well documented at calf bedding sites subsequent to parturition; however, because of variably reported results from prior studies, it is unclear whether hiding cover is selected at the immediate birth site. We estimated visual obstruction of hiding cover, measured understory vegetation height, and categorized the dominant form of hiding cover at 65 birth sites and 116 random sites within the Black Hills, South Dakota. We found no significant differences in visual obstruction, vegetation height, or selection of dominant hiding cover categories between birth and random sites within forest and grassland systems. We surmise that selection of birth sites with greater visibility was used as a strategy to increase detectability of potential human and puma (Puma concolor) disturbances, which may be hindered by understory vegetation or woody debris that obstructs visibility. This may explain why we did not detect any selection for hiding cover; thus, understory cover for calves may not be a driving factor for selection of birth sites.
Joshua tree (Yucca brevifolia Engelm.) is a large, arborescent member of the yucca genus. It is an endemic and visually dominant plant in portions of the Mojave Desert, USA. We document the unique and heretofore unreported directional orientation of its flower panicles. The flower panicles grow primarily at the tips of branches that are oriented to the south. When branches with flower panicles are not oriented in a southerly direction, the flower panicles themselves tend to bend or tilt toward the south. This strategy maximizes exposure of the panicles to direct solar radiation, which, within the latitudes where the Joshua tree grows, is always from the south. Such a strategy may minimize the energetic cost of translocating photosynthates from the plant's leaf rosettes to the flowers. The flower panicles create large, light-colored landing pads for the obligate nocturnal moth pollinator. Residual warmth in the flower panicles may provide a thermal reward for the moth pollinator that emerges shortly after sunset.
Parasite communities of stream fish assemblages in the western United States are poorly known. We investigated the intestinal parasites of an assemblage of stream fishes in Spanish Fork River in central Utah, USA. Two species, mottled sculpin (Cottus bairdii) and redside shiner (Richardsonius balteatus), had no observable parasites. In the other 3 species, southern leatherside chub (Lepidomeda aliciae), mountain sucker (Catostomus platyrhynchus), and longnose dace (Rhinichthys cataractae), we identified metacercia of an unidentified trematode. We found adult cestodes in southern leatherside chub only. Prevalence and intensity of parasites was highest in southern leatherside chub. Reasons for differential prevalence and intensity of parasites among host fish species are unknown, but there seems to be no relationship to trophic position or habitat use in this fish community.
Packera franciscana (Greene) W.A. Weber and Á. Löve (Asteraceae) (San Francisco Peaks ragwort) is an alpine-zone endemic of the San Francisco Peaks in northern Arizona. Previous studies have shown that P. franciscana is patchily distributed in alpine-zone talus habitats. The purpose of this study was to describe the relationship between snow duration and P. franciscana abundance. We established trailside transects through P. franciscana habitat along the Weatherford Trail to estimate the abundance of P. franciscana ramets. Snow-free and snowbed sample segments were chosen based on a 17 May 2013 snow photograph taken from within the Inner Basin of the San Francisco Peaks caldera. The section of the Weatherford Trail under snow on 17 May 2013 had a 5-year arithmetic mean of 1.53 ramets ⋅ m-2 (SE 0.37)—much less dense than the snow-free section which had a 5-year arithmetic mean of 7.17 ramets ⋅ m-2 (SE 1.09). The steep upper portion of talus slopes is known to move downslope faster than mid- and lower slope portions due to gravitational processes working on surface particle size, slope angle, and frost heave/needle ice during moist periods. Needle ice is known to uproot seedlings in other species. Active talus shift may inhibit P. franciscana colonization and growth on upper talus slopes via high seedling mortality in the snowbed zone during spring snowmelt.