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Liorhyssus hyalinus (F.) is a nearly cosmopolitan, polyphagous rhopalid, or scentless plant bug, that feeds mainly on flowers, fruits, and seeds of its hosts. Adults are known from numerous plants in diverse families, whereas nymphs develop on fewer species. Thirteen species of host plants were recorded for L. hyalinus during the sampling of grasses, forbs, subshrubs, and shrubs in the western United States (west of 100th meridian) from 2000 to 2015. The 11 new host records are Lygodesmia juncea, Machaeranthera tanacetifolia, Sonchus asper, Stephanomeria exigua, S. pauciflora, and S. thurberi (Asteraceae); Chamaesyce albomarginata (Euphorbiaceae); Erodium botrys and E. texanum (Geraniaceae); and Malva parviflora and Sphaeralcea ambigua (Malvaceae). The most common host (9 collections) was the adventive Erodium cicutarium, previously reported as a host in the Old World. Another previously known host was Sonchus oleraceus. Hosts of L. hyalinus in western states comprise four principal groups: late...

Local adaptation influences plant species’ responses to climate change and their performance in ecological restoration. Fine-scale physiological or phenological adaptations that direct demographic processes may drive intraspecific variability when baseline environmental conditions change. Landscape genomics characterize adaptive differentiation by identifying environmental drivers of adaptive genetic variability and mapping the associated landscape patterns. We applied such an approach to Sphaeralcea ambigua, an important restoration plant in the arid southwestern United States, by analyzing variation at 153 amplified fragment length polymorphism loci in the context of environmental gradients separating 47 Mojave Desert populations. We identified 37 potentially adaptive loci through a combination of genome scan approaches. We then used a generalized dissimilarity model (GDM) to relate variability in potentially adaptive loci with spatial gradients in temperature, precipitation, and topography. We identified non-linear thresholds in loci frequencies driven by summer maximum temperature and water stress, along with continuous variation corresponding to temperature seasonality. Two GDM-based approaches for mapping predicted patterns of local adaptation are compared. Additionally, we assess uncertainty in spatial interpolations through a novel spatial bootstrapping approach. Our study presents robust, accessible methods for deriving spatially-explicit models of adaptive genetic variability in non-model species that will inform climate change modelling and ecological restoration.

Wildfires burned 24,254 ha of critical habitat designated for the recovery of the threatened Mojave desert tortoise (Gopherus agassizii) in southern Nevada during 2005. The proliferation of non-native annual grasses has increased wildfire frequency and extent in recent decades and continues to accelerate the conversion of tortoise habitat across the Mojave Desert. Immediate changes to vegetation are expected to reduce quality of critical habitat, yet whether tortoises will use burned and recovering habitat differently from intact unburned habitat is unknown. We compared movement patterns, home-range size, behavior, microhabitat use, reproduction, and survival for adult desert tortoises located in, and adjacent to, burned habitat to understand how tortoises respond to recovering burned habitat. Approximately 45% of home ranges in the post-fire environment contained burned habitat, and numerous observations (n = 12,223) corroborated tortoise use of both habitat types (52% unburned, 48% burned). Tortoises moved progressively deeper into burned habitat during the first 5 years following the fire, frequently foraging in burned habitats that had abundant annual plants, and returning to adjacent unburned habitat for cover provided by intact perennial vegetation. However, by years 6 and 7, the live cover of the short-lived herbaceous perennial desert globemallow (Sphaeralcea ambigua) that typically re-colonizes burned areas declined, resulting in a contraction of tortoise movements from the burned areas. Health and egg production were similar between burned and unburned areas indicating that tortoises were able to acquire necessary resources using both areas. This study documents that adult Mojave desert tortoises continue to use habitat burned once by wildfire. Thus, continued management of this burned habitat may contribute toward the recovery of the species in the face of many sources of habitat loss. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

In desert ecosystems, selective foraging by seed consumers affects distribution and composition of soil seed banks, influencing plant population dynamics. However, the roles of consumers in burned habitats where direct seeding is used during ecological restoration to replenish depleted seed banks have not been well established. We evaluated seed removal for nine seed species over 12 months in burned and unburned shrublands in the Mojave Desert, USA. Percentage of total seed removed was highest during spring (16% of offered seed) and summer (21%). Rodents removed much of the large-seeded Coleogyne ramosissima in both burned and unburned habitats, while seed removal of this species by ants was low in burned and moderate in unburned habitats. Ants removed the greatest amount of small-seeded species (Penstemon bicolor, Encelia farinosa, and Sphaeralcea ambigua) in unburned habitat, indicating that ants can exploit different seed masses. Seed removal imposes limitations on seed availability, particularly for large-seeded species, as both rodents and ants selected seeds of C. ramosissima. Successful restoration seeding projects in arid lands may require protecting seed from granivore pressure, and seed species selection and season of seeding warrant consideration to reduce seed loss.

Developing reliable techniques for revegetating disturbed arid lands is challenging. Few studies have directly compared effectiveness of the 2 main revegetation techniques— seeding and outplanting—and the relationship to various treatments intended to enhance plant establishment. We compared seeding and planting and evaluated granivory protection, irrigation, and shelter treatments with a range of native perennial species monitored for 3 y on a wildfire site in the Mojave Desert of southern Nevada. Contrasted with previous studies in the Mojave Desert, seeding failed to establish new plants, despite protecting seeds from small mammal granivory, irrigating, and using seeds known to be viable during a study period that included a mix of moist and dry years. Outplanting, however, resulted in third-year survival = 22% for 4 of 10 species. The best-performing species and their survival included desert globemallow ( Sphaeralcea ambigua A. Gray [Malvaceae]; 55%), Eastern Mojave buckwheat ( Eriogonum fasciculatum Benth. [Polygonaceae]; 28%), white bursage ( Ambrosia dumosa (A. Gray) Payne [Asteraceae]; 23%), and creosote bush ( Larrea tridentata (DC.) Coville [Zygophyllaceae]; 23%). Adding either water or shelter approximately doubled survival. Surviving the first year appeared critical to success, as out-plants healthy at year 1 remained alive at year 3. Although outplanting is often considered inferior for introducing propagules to larger areas in comparison with seeding, a finding that 86% of Sphaeralcea and 73% of Eriogonum survivors were flowering suggests that potential seed production by the outplants should not be dismissed. Results suggest that outplanting native perennials can revegetate desert disturbances, especially if early survival can be increased.

Mechanical scarification plus stratification was most effective in improving germination of Sphaeralcea ambigua A. Gray and Sphaeralcea coccinea (Nutt.) Rydb. (Malvaceae) in my experiment that compared 4 seed treatments. The pattern of species response to treatments was similar. The control treatment (seeds left at room temperature in original packing envelopes) and the 30-d stratification at 4 °C (39 °F) treatment both yielded low germination (average 12%). Mechanical scarification alone improved germination (average 44%); while the combination of mechanical scarification plus 30-d stratification resulted in an average 65% germination (45% and 85% germination for S. ambigua and S. coccinea , respectively). Although impermeability of the seedcoat is the main factor preventing germination, embryos also appear to be partially or conditionally dormant. These treatments may have potential for other Sphaeralcea species.

Increasing wildfire activity is one of the most pressing management concerns in arid lands of the American West. To examine post-fire recovery of perennial vegetation in the Mojave and Sonoran Deserts, I analyzed data systematically synthesized from the literature. Post-fire sprouting by desert perennials is generally limited but varies among species. For example, only 3–37% of Larrea tridentata sprouted compared to 64–86% of Yucca schidigera . Four of five studies measuring recovery of perennial cover reported close relationships ( r 2 = 0.67–0.99) between time since fire (TSF) and cover. In fact, three studies measuring the longest TSF (≥37 years) found that cover had returned to within 10% cover of unburned areas within approximately 40 years. Conversely, post-fire species composition exhibited little convergence with unburned composition in five of six studies even 47 years after fire. Sphaeralcea ambigua , Gutierrezia spp., Achnatherum speciosum , Encelia spp., Hymenoclea salsola , and Baileya multiradiata had the highest burned:unburned abundance ratios, although overall post-fire community composition differed between the Mojave and Sonoran Deserts. Analyzing the literature as a whole suggested some generalities (e.g., that perennial cover reestablishes faster than composition), but more work is required for improving specific knowledge about plant recovery among fires, sites, species, and climates.

Spatial pattern and patterns of mortality were analyzed from a five year re-census of over 7000 mapped perennial shrubs within a one hectare study plot in Joshua Tree National Park. A five year interval revealed evidence for negative intraspecific interactions which was not evident after a one year evaluation of the same plants within the study area. Juvenile mortality was a positive function of conspecific density for Ambrosia dumosa, Eriogonum fasciculatum and Sphaeralcea ambigua. In addition, juvenile E. fasciculatum that died occurred closer to conspecific adults than would be expected by chance. The two censuses are similar in that uniform patterns of distribution among conspecifics are rare, particularly for non-succulent species.

The North American tortoise Xerobates agassizii (synonym: Gopherus agassizii) consumes herbage and grasses produced from low and variable desert rains. Utilization of Sphaeralcea ambigua foliage and the grass Schismus barbatus were studied in 8 adult tortoises (2.3 kg body mass). The herbage contained more N but less fiber than the grass. Tortoises ingested and digested more dry matter and energy from herbage than grass. Intakes and retention of N were greater from the herbage than the grass, but amino acid proportions and true N digestibilities were similar between diets. Herbage contained more Ca than grass, especially in relation to P (Ca:P 14.5 vs. 1.9), but this was ameliorated by lower absorption of Ca from the hergage. K intakes were greater from the herbage than the grass and associated with the digestive loss of Mg from herbage. Low Na content of both forages resulted in net losses of Na. Maintenance requirements for dietary N (14.4 mg · kg−0.75 · d−1) and for digestible energy (19.9 kJ · kg−0.75 · d−1) were lower than estimates for other herbivorous reptiles and consistent with the utilization of desert pastures where quality and abundance may be low and erratic. Modest requirements for these and other nutrients may enable desert tortoises to tolerate temporal deficiencies, but these must ultimately be corrected by a wider dietary selection. Consequently, both diversity and abundance of pasture growth may be critical to long-term nutrient balances of this threatened species.

Fossil packrat middens are used to reconstruct late Quaternary environments in the arid Western U.S.A. Airborne pollen is contributed to middens both directly from the air, and through adherence to plant macrofossils. I examined the filtration of atmospheric pollen by Larrea tridentata leaves (resinous, with sparse recumbent hairs), Cercidium microphyllum twigs (glabrous with recumbent hairs) and Sphaeralcea ambigua leaves (covered with stellate hairs) and evaluated the potential biases of scavenged pollen on the interpretation of pollen records from middens. Pollen grains collected from the surfaces of the plants were most numerous during the spring when (airborne) pollen concentrations were high. Of the species investigated, the Sphaeralcea leaves filtered the greatest number of spring pollen grains from the air (3419 grains cm−2); captured pollen was very low during other seasons. Sticky Larrea leaves continuously captured airborne pollen ( = 246 grains cm−2). Pollen captured by smooth Cercidi...

We tested for intraspecific interference among Colorado Desert shrubs using an integrated analysis of spatial pattern and juvenile mortality. The data set included 7,000 woody perennials of 24 species in a mapped hectare of Joshua Tree National Monument, California. The site is dominated by Ambrosia dumosa (62.0% of the stems), with Larre tridentata a conspicuous secondary species (2.3% of the stems). Analyses of static pattern for common species showed: (1) aggregated adults and juveniles for Ambrosia dumosa, Erigonum fasciculatum, Mirabilis bigelovii, and Sphaeralcea ambigua, with more aggregation among juveniles than adults; (2) randomly distributed adults and juveniles for Krameria grayi, Opuntia rasmosissima, Simondsia chinensis, and Yucca schidigera. The summed volumes and distances between nearest conspecific neighbors were positively correlated for Ambrosia dumosa and Larrea tridentata, but not significantly correlated for eight remaining species with ≥100 individuals. Static pattern suggests only weak evidence for negative interactions in Ambrosia and Larrea, and little evidence for other species. Alternative mechanisms other than negative interaction that could give rise to these static patterns are discussed. Juvenile mortality was documented for four common species (Ambrosia dumosa, Eriogonum fasciculatum, Mirabilis bigelovii, and Sphaeralcea ambigua) that experienced substantial mortality. Analyses show: (1) the proportion of individuals that died was independent of the initial density of conspecifics; (2) distance to conspecific adults did not differ for juveniles that died versus those that survived; and (3) death was no more likely for juveniles that contacted other plants than for those that were isolated. The exception was a vine, Mirabilis bigelovii, whose juveniles survived better in contact with other plants. In sum, neither spatial pattern nor patterns of mortality showed clear evidence of negative intraspecific interference.

The feces of the Shasta ground sloth (Nothrotheriops shastense), preserved by the arid climate of the lower Grand Canyon, were collected at various levels and examined by microhistological analyses to identify and quantify plant taxa in the diet. Over 500 pieces of different Shasta sloth coprolites were examined. Sloth dung from the nearby Muav Caves was examined and compared with that from Rampart Cave.Seventy-two genera of plants were identified in the sloth dung deposited discontinuously from over 40,000 to about 11,000 yr BP. The major plant taxa in the Rampart Cave sloth diets were desert globemallow (Sphaeralcea ambigua = 52%), Nevada mormontea (Ephedra nevadensis = 18%), saltbushes (Atriplex spp. = 7%), catclaw acacia (Acacia greggii = 6%), Cactaceae spp. (= 3%), common reed (Phragmites communis = 5%), and yucca (Yucca spp. = 2%).Six of the most abundant plants in sloth diets were collected in the environs of Rampart Cave and were analyzed for their energy, fiber and nutrient values. The simulated diets of Rampart Cave sloths averaged 1679 cal/g in digestible gross energy and 7.9% for digestible protein. Apart from a substantial increase in digestible energy and in mormontea there was no unusual change in the sloth diet immediately prior to the time of their extinction.The ecological role of Nothrotheriops shastense is less dramatically different from that of extant desert herbivores than was previously believed.