California Desert Research Articles

Reproductive Output and Clutch Phenology of Female Agassiz's Desert Tortoises (Gopherus agassizii) in the Sonoran Desert Region of Joshua Tree National Park

Agassiz's desert tortoise (Gopherus agassizii) reaches the southern edge of its range in the Sonoran Desert of California. The reproductive ecology of this wideranging species is understudied here compared to populations in the adjacent Mojave Desert. Understanding potential geographic variation in reproductive ecology is important for effective management of conservation-reliant species like G. agassizii. We studied the fecundity and clutch phenology of female G. agassizii at two study sites in the Sonoran Desert region of Joshua Tree National Park over five years (1997–1999, 2015–2016) spanning two of the strongest El Nino events on record and an epic drought. Across all years, mean clutch size was 4.3±1.5 eggs, mean clutch frequency was 1.78 clutches/female/year, and mean X-ray egg width was 36.51±1.56 mm, all of which are comparable to other published studies both in the Sonoran and Mojave deserts of California. Our results generally support earlier published findings that G. agassizii utilize a bet-hedging strategy of consistently producing small clutches almost every year, even during times of low annual primary productivity. A regionally warmer climate in the Sonoran Desert of California appears to have an effect on the timing of egg production, as the earliest dates of egg visibility in our study (April 6) were approximately two weeks earlier than the earliest dates reported for G. agassizii in the Mojave Desert. Shelled eggs were no longer visible in tortoises after mid-June in all years but the El Nino year 1998, when eggs were visible until mid-July.

The Groot Effect: Plant facilitation and desert shrub regrowth following extensive damage.

Deserts are increasing in extent globally, but existing deserts are decreasing in health. The basic biology and ecology of foundation plant species in deserts are limited. This is a direct study that provides an estimate of the capacity for a locally dominant foundation shrub species in California to recover from damage. Desert shrubs are cleared and damaged by humans for many purposes including agriculture, oil and gas production, and sustainable energy developments; we need to know whether foundation species consistently facilitate the abundance and diversity of other plants in high‐stress ecosystems and whether they can recover. A total of 20 Ephedra californica shrubs were clipped to the ground at a single site and systematically resampled for regrowth 2 years later. These shrubs were damaged once and regrew rapidly, and relatively, larger shrubs were not more resilient. This study provides evidence for what we termed the “Groot Effect” because smaller individuals of this shrub species can recover from significant aboveground damage and continue to have positive effects on other plant species (similar to the popular culture reference to a benefactor tree species). The density of other plant species was consistently facilitated while effects on diversity varied with season. These findings confirm that E. californica is a foundation species that can be an important restoration tool within the deserts of California in spite of extreme cycles of drought and physical damage to its canopy.

Spatial phylogenetics of the native California flora

BackgroundCalifornia is a world floristic biodiversity hotspot where the terms neo- and paleo-endemism were first applied. Using spatial phylogenetics, it is now possible to evaluate biodiversity from an evolutionary standpoint, including discovering significant areas of neo- and paleo-endemism, by combining spatial information from museum collections and DNA-based phylogenies. Here we used a distributional dataset of 1.39 million herbarium specimens, a phylogeny of 1083 operational taxonomic units (OTUs) and 9 genes, and a spatial randomization test to identify regions of significant phylogenetic diversity, relative phylogenetic diversity, and phylogenetic endemism (PE), as well as to conduct a categorical analysis of neo- and paleo-endemism (CANAPE).ResultsWe found (1) extensive phylogenetic clustering in the South Coast Ranges, southern Great Valley, and deserts of California; (2) significant concentrations of short branches in the Mojave and Great Basin Deserts and the South Coast Ranges and long branches in the northern Great Valley, Sierra Nevada foothills, and the northwestern and southwestern parts of the state; (3) significant concentrations of paleo-endemism in Northwestern California, the northern Great Valley, and western Sonoran Desert, and neo-endemism in the White-Inyo Range, northern Mojave Desert, and southern Channel Islands. Multiple analyses were run to observe the effects on significance patterns of using different phylogenetic tree topologies (uncalibrated trees versus time-calibrated ultrametric trees) and using different representations of OTU ranges (herbarium specimen locations versus species distribution models).ConclusionsThese analyses showed that examining the geographic distributions of branch lengths in a statistical framework adds a new dimension to California floristics that, in comparison with climatic data, helps to illuminate causes of endemism. In particular, the concentration of significant PE in more arid regions of California extends previous ideas about aridity as an evolutionary stimulus. The patterns seen are largely robust to phylogenetic uncertainty and time calibration but are sensitive to the use of occurrence data versus modeled ranges, indicating that special attention toward improving geographic distributional data should be top priority in the future for advancing understanding of spatial patterns of biodiversity.

The Record Los Angeles Heat Event of September 2010: 1. Synoptic‐Scale‐Meso‐β‐Scale Analyses of Interactive Planetary Wave Breaking, Terrain‐ and Coastal‐Induced Circulations

AbstractOn 27 September 2010 the Los Angeles Civic Center reached its all‐time record maximum temperature of 45°C before 1330 local daylight time with several other regional stations observing all‐time record breaking heat early in that afternoon. This record event is associated with a general circulation pattern predisposed to hemispheric wave breaking. Three days before the event, wave breaking organizes complex terrain‐ and coastal‐induced processes that lead to isentropic surface folding into the Los Angeles Basin. The first wave break occurs over the western two thirds of North America leading to trough elongation across the southwestern U.S. Collocated with this trough is an isentropic potential vorticity filament that is the locus of a thermally indirect circulation central to warming and associated thickness increases and ridging westward across the Great Basin. In response to this circulation, two subsynoptic wave breaks are triggered along the Pacific coast. The isentropic potential vorticity filament is coupled to the breaking waves and the interaction produces a subsynoptic low‐pressure center and a deep vortex aloft over the southeastern California desert. This coupling leads to advection of an elevated mixed layer over Point Conception the night before the record‐breaking heat that creates a coastally trapped low‐pressure area southwest of Los Angeles. The two low‐pressure centers create a low‐level pressure gradient and east‐southeasterly jet directed offshore over the Los Angeles Basin by sunrise on 27 September. This allows the advection of low‐level warm air from the inland terrain toward the coastally trapped disturbance and descending circulation resulting in record heating.

Stem photosynthesis and hydraulics are coordinated in desert plant species.

Coordination between stem photosynthesis and hydraulics in green-stemmed desert plants is important for understanding the physiology of stem photosynthesis and possible drought responses. Plants with photosynthetic stems have extra carbon gain that can help cope with the detrimental effects of drought. We studied photosynthetic, hydraulic and functional traits of 11 plant species with photosynthetic stems from three California desert locations. We compared relationships among traits between wet and dry seasons to test the effect of seasonality on these relationships. Finally, we compared stem trait relationships with analogous relationships in the leaf economics spectrum. We found that photosynthetic and hydraulic traits are coordinated in photosynthetic stems. The slope or intercept of all trait relationships was mediated by seasonality. The relationship between mass-based stem photosynthetic CO2 assimilation rate (Amass ) and specific stem area (SSA; stem surface area to dry mass ratio) was statistically indistinguishable from the leaf economics spectrum. Our results indicate that photosynthetic stems behave like leaves in the coordination of multiple traits related to carbon gain, water movement and water loss. Because of the similarity of the stem Amass -SSA relationship to the leaf Amass -specific leaf area relationship, we suggest the existence of a photosynthetic stem economic spectrum.

A Contribution to the Phylogeography and Anatomy of Helminthoglyptid Land Snails (Pulmonata: Helminthoglyptidae) from the Deserts of Southern California

Abstract Land snails in the family Helminthoglyptidae are found sparingly and locally throughout southern California's deserts. They are mostly restricted to rock outcrops and talus in partially shaded canyons where they can gain access to cooler temperatures under the rocks. Several species are known only from their type localities, and were described by shell characters only. We have endeavored to locate known species, document their reproductive anatomy and embryonic shell structure, refine knowledge of their distribution, and incorporate genetic sequencing of two mitochondrial genes (COI and 16S) to investigate evolutionary relationships in these taxa. As a “first pass” molecular study, we have established basic sequence and divergence data for 27 populations of snails in five genera: Helminthoglypta (subgenus Coyote), Eremarionta, Cahuillus, Chamaearionta and Sonorelix. Fifteen of the populations were previously unknown. We confirmed that the Salton Rift/Coachella Valley is a major biogeographic barr...

High intraspecific genetic divergence in the versatile fairy shrimp Branchinecta lindahli with a comment on cryptic species in the genus Branchinecta (Crustacea: Anostraca)

Branchinecta lindahli is a generalist fairy shrimp that has a widespread distribution in North America. We initiated a study to better understand the geographic structure of genetic variation within this species and to test if cryptic species are present in B. lindahli. Additionally, we examined four other species of Branchinecta to test if there were any generalities in the levels of genetic divergence within and among species. Genetic data from the mitochondrial cytochrome c oxidase I gene revealed two distinct clades within B. lindahli: one found in the Central Valley and Mojave Desert of California, USA and one found in Baja California, Mexico. The remaining haplotypes were widespread throughout the remainder of North America. Further examination of the distribution within clades revealed no additional phylogeographic structure. The amount of intraspecific divergence observed for B. lindahli and B. hiberna was high compared to B. mackini and B. sandiegonensis. However, maximal intraspecific divergences were less than what was observed among Branchinecta species. We argue that the amount of intraspecific divergence observed in B. lindahli is not consistent with the presence of cryptic species and that caution should be taken when attempting to delimit cryptic species within this group.

Genetic Structure Across a Contact Zone betweenXerospermophilusGround Squirrels in Southern California

The Mohave ground squirrel (Xerospermophilus mohavensis) is endemic to the western Mojave Desert of California and is state-listed as Threatened. This species is of conservation concern because of the potential for large-scale renewable energy development within its range. Recent evidence suggests that this threatened species may at least occasionally hybridize with the closely related round-tailed ground squirrel (Xerospermophilus tereticaudus) where the species come into contact. As a result, there is great interest in the distribution of the Mohave ground squirrel, especially where it may come in contact with the round-tailed ground squirrel. One of the least understood portions of the Mohave ground squirrel distribution is around the Hinkley Valley, west of the city of Barstow, where its eastern range limits come into proximity with the round-tailed ground squirrel. To document what is known of the fine-scale distribution of these congeners in this region, we assemble and review all available trapping survey data from this area and combine the field survey data with genetic analyses of recently collected samples. Our evaluation of trapping records confirms that there are no reliable recent reports of Mohave ground squirrels in the Hinkley Valley itself, which has been developed for agriculture. The species appears to be largely restricted to the relatively undisturbed desert habitat west of Hinkley. In contrast, a number of round-tailed ground squirrel records exist for the Hinkley Valley, some dating back to 1977. Using 13 nuclear microsatellite loci from 55 ground squirrel samples collected across this region, we confirm the presence of genetically pure Mohave and round-tailed ground squirrels. However, 3 individuals collected in the Hinkley Valley that were identified as round-tailed ground squirrels on the basis of external characteristics show evidence of Mohave ground squirrel ancestry. In similar fashion, 3 animals from the desert region west of Hinkley were found to have some round-tailed ground squirrel genetic ancestry in spite of external features typical of Mohave ground squirrels. While round-tailed ground squirrels seem to be the dominant species in Hinkley Valley and Mohave ground squirrels seem dominant in the desert environment to the west, hybridization does appear to occur occasionally. Further, when these species hybridize, at least some hybrids are fertile, and backcrossing appears to occur in both parental directions. It is important to investigate this phenomenon more closely to evaluate possible threats to the genetic integrity of the Mohave ground squirrel.

From Vietnam, VA, to Iraq, CA: The Spectrality of Violence in An-My Lê’s Small Wars and 29 Palms

This paper focuses on two of the three photographic projects included in An-My Le’s Small Wars (2005). The first one, Small Wars (1999–2002) represents Vietnam War reenactors staging combat in the Virginian forest. In the second project, 29 Palms (2003–2004), Le turns her camera on United States Marines preparing for deployment in Iraq in the California desert. In the series, warfare is either reenacted or rehearsed without the violent outcome of combat being tangibly represented. However, the spectrality of past and impending violence permeates the photographs and confirms the haunting legacy of war iconography. We will examine how Le uses the American landscape and creates images haunted by the invisible visibility of violence.

The Map and the Territory: Documenting David Dunn’s Sky Drift

In 1977, a large group of musicians performed David Dunn’s Sky Drift while moving slowly across a Southern California desert, documenting the concert with four stationary microphones. A year later, Dunn presented the work in New York as a ‘performance/documentation’, playing back the audio recording for a seated audience. This article explores issues of ‘liveness’ in recorded sound, ‘transparency’, ‘aura’ and ‘the work itself’ in order to examine the consequences of this act: what does it mean for a recording of an outdoor performance to be shared at an indoor concert event? Can such a complex and interactive experience – with widely dispersed musicians and mobile audience members – be successfully converted into a fixed document? What does a recording capture and what must it exclude? Because Sky Drift constantly shifts the physical relationships between musicians and audience across a vast outdoor landscape, each listener’s experience represents an equally valid sonic perspective on the piece. As a result, it is unclear how a satisfying recording might be made or what it might even mean to ‘hear the music’ at all. When relocated – away from its original outdoor context – Sky Drift is deprived of much of its potential to communicate meaning.

Making the desert BLOOM

With virtually a non‐stop growing season with mild winters and fertile soils, southeast California's desert region provides 80% of the fresh fruits and vegetables for the U.S. in the winter. But, without the combined efforts of science, technology, industry, university research, Cooperative Extension, and government support, the miracle known as “America's Winter Garden” would otherwise be an inhospitable desert wasteland.

Diet of the Mohave Ground Squirrel (Xerospermophilus mohavensis) in Relation to Season and Rainfall

The Mohave ground squirrel (Xerospermophilus mohavensis) is endemic to the western Mojave Desert of California. It is listed as threatened under the California Endangered Species Act, yet there is little published information on its habitat requirements. We studied the diet of Mohave ground squirrels at 4 sites in desert scrub habitat in Inyo County, California, primarily by microhistological analysis of 754 samples of fecal pellets collected from live-trapped animals. Over all sites and seasons, shrub foliage was the largest component of the diet (39.8% relative density) and mainly derived from several taxa of Chenopodiaceae: winterfat (Krascheninnikovia lanata), spiny hopsage (Grayia spinosa), and saltbushes (Atriplex spp.). Forb leaves were next in importance (34.1% relative density), especially from Fabaceae (Astragalus and Lupinus), Polemoniaceae (Gilia and Linanthus), and Asteraceae. Flowers, pollen, and seeds were also major components (20.3% relative density). Leaves composed nearly all of the diet in spring, whereas pollen, flowers, and seeds made up about a third of the diet in summer. Following dry winters when annual forbs were limited, Mohave ground squirrels depended primarily on foliage from perennial shrubs and forbs. Following wet winters when spring annuals were abundant and most plant species flowered and set seed prolifically, squirrels consumed a high proportion of leaves plus flowers, pollen, and seeds of annual forbs. Mohave ground squirrels reproduced only after winter rainfall >80 mm that resulted in a standing crop of herbaceous annuals ≥100 kg · ha-1. Mohave ground squirrels consumed very little of the nonnative annual plant biomass present on our study sites (Erodium, Salsola, Bromus, and Schismus contributed <3% overall to the diet). Conservation implications include the following: (1) priority should be given to protecting habitats supporting preferred perennial forage plants, including winterfat and spiny hopsage; (2) habitats with an understory dominated by native annual forbs have higher value than those dominated by nonnative plants, especially annual grasses; and (3) if climate change results in lower and less regular winter precipitation, suitable habitat for Mohave ground squirrels may be reduced and fragmented in the drier portions of the geographic range.

Host plant resistance in melon to sweetpotato whitefly in California and Arizona

Sweetpotato whitefly biotype B (MEAM1 cryptic species of Bemisia tabaci; SPWF) feeding severely impacts fall season melon (Cucumis melo L.) yield and quality in the lower deserts of California and Arizona. Melon accessions PI 313970 and TGR 1551 (PI 482420) have been reported to exhibit host plant resistance (HPR) to SPWF. Potentially higher and lower levels of HPR to SPWF were observed in ad hoc comparisons of numbers of adults per leaf on six melon accessions, PI 313970, TGR 1551, 'Impac', and 'Top Mark' in a naturally infested field test at Holtville, CA in fall 2012. Replicated field tests at Holtville in fall 2013 and spring 2014 (when SPWF populations are lower than in the fall) compared SPWF infestation of five (PI 116482, PI 123689, PI 124107, PI 124431, PI 145594) of the six accessions with PI 313970, TGR 1551, TGR 1937 (PI 482431), 'Top Mark' and 'Impac'. Statistically significant differences were found in both seasons among the entries for numbers of adults per sampled leaf, eggs, crawlers, red eyes, or nymphs cm-2 leaf area at many but not all sampling dates. Though there were significant (P<0.05) differences among the entries for number of adults per sampled leaf at seven weekly sampling dates in fall 2013, none of the accessions had consistently fewer adults than 'Impac' or 'Top Mark'. There were few differences among the entries in spring 2014 for numbers of adults per sampled leaf. PI 116482 had the most, and PI 145594, PI 313970 and TGR 1937 had the fewest adults, on average.

Common Raven (Corvus corax) kleptoparasitism at a Golden Eagle (Aquila chyrsaetos) nest in southern Nevada

ABSTRACT.— The Common Raven (Corvus corax) is a ubiquitous species in the Mojave Desert of southern Nevada and California. From 5 to 24 May 2014, using remote trail cameras, we observed ravens repeatedly kleptoparasitizing food resources from the nest of a pair of Golden Eagles (Aquila chyrsaetos) in the Spring Mountains of southern Nevada. The ravens fed on nine (30%) of the 30 prey items delivered to the nest during the chick rearing period. Kleptoparasitic behavior by the ravens decreased as the eagle nestling matured to seven weeks of age, suggesting a narrow temporal window in which ravens can successfully engage in kleptoparasitic behavior at eagle nests. The observation of kleptoparasitism by Common Ravens at the nest suggests potential risks to young Golden Eagles from Common Ravens.

Community Structure and Demography in a Saline Pan-Dune Mosaic in the Western Mojave Desert

A unique saline ecological system formed by an extensive mosaic of small clay pans and low stable dunes exists within Edwards Air Force Base in the western Mojave Desert of California. This ecosystem lies between the large Rosamond and Rogers dry lakes on the old Pleistocene lakebed of Lake Thompson. Plant communities on the low and relatively stable dunes were broadly classed as saltbush scrub, with a total canopy cover of 30–36%. Atriplex confertifolia was the typical dominant, with Ericameria nauseosa as an important associate. Taller dunes of younger age and less saline soils had similar plant cover, but a distinct plant community with Atriplex canescens and Krascheninnikovia lanata as dominants and Yucca brevifolia as a common associate. Flat areas adjacent to the dunes were dominated by a virtual monoculture of Atriplex confertifolia. Aboveground shrub and bunchgrass biomass including dead material varied from 503 to 1204 kg ha−1, low in comparison to similar plant communities in the Great Basin. The absence of small saplings and seedlings of many shrub species suggests successful establishment is highly episodic. Seedlings were abundant only in Isocoma acradenia.

Plant Phenology and Water Relations in a Saline Pan-Dune Mosaic in the Western Mojave Desert

An extensive mosaic of small clay pans and low stable dunes exists within Edwards Air Force Base in the western Mojave Desert of California. This pan-dune ecosystem, positioned between the large Rosamond and Rogers dry lakes on the old Pleistocene lakebed of Lake Thompson, provides an opportunity to study the seasonal patterns in growth and flowering phenology and water relations in a saltbush scrub community dominated by a mix of C3 and C4 species. C3 shrubs initiated vegetative growth in February, with current shoot and leaf production largely ceasing in most species by mid-April. The deeply rooted Tetradymia stenolepis and Ericameria nauseosa continued vegetative growth through May. C4 species including Atriplex and the grass Distichilis spicata typically began vegetative growth in mid- to late March, 2–6 weeks later than the first group and continued this growth in most cases through June and July. Reproductive growth commonly did not begin until June and continued into July and/or August. Shrub species showed a general pattern of slowly declining water potentials (increased stress) through the late spring and summer months, reflecting more limited soil water availability. Smaller changes in predawn water potential over this period were seen in the deeply rooted species. Soil moisture availability in the widespread Atriplex confertifolia showed a pattern of variation between pan, dune and open flat microhabtats.

Patterns of Spatial Distribution of Golden Eagles Across North America: How Do They Fit into Existing Landscape-scale Mapping Systems?

Abstract Conserving wide-ranging animals requires knowledge about their year-round movements and resource use. Golden Eagles (Aquila chrysaetos) exhibit a wide range of movement patterns across North America. We combined tracking data from 571 Golden Eagles from multiple independent satellite-telemetry projects from North America to provide a comprehensive look at the magnitude and extent of these movements on a continental scale. We compared patterns of use relative to four alternative administrative and ecological mapping systems, namely Bird Conservation Regions (BCRs), U.S. administrative migratory bird flyways, Migratory Bird Joint Ventures, and Landscape Conservation Cooperatives. Our analyses suggested that eagles initially captured in eastern North America used space differently than those captured in western North America. Other groups of eagles that exhibited distinct patterns in space use included long-distance migrants from northern latitudes, and southwestern and Californian desert residents....

A Vascular Flora of the Kiavah Wilderness, Scodie Mountains, Kern County, California

Congress designated the Kiavah Wilderness in 1994 under the California Desert Protection Act. It is located in the Scodie Mountains in Kern County, ca. 24 km (15 mi) east of Lake Isabella and 24 km (15 mi) west of Ridgecrest, and encompasses a total of 137 mi2 (354 km2) with elevations ranging from 1000 to 2200 m (3500–7294 ft). The Wilderness is ecologically important because it occurs in a transition zone between two floristic provinces, the Sierra Nevada of the California Floristic Province and the Mojave Desert of the Desert Province. It is of cultural significance because it has a rich history of Native Americans harvesting pinyon pine nuts and inhabiting the land. Prior to the study ca. 290 vascular plant taxa had been documented, primarily along roads and the Pacific Crest Trail. Jim Shevock and Barbara Ertter made significant collections and contributions to the floristic inventory during the 1980s and early 1990s, and LeRoy Gross added valuable collections in 2005 and 2006. The purpose of the project was to inventory the vascular plant taxa throughout the Kiavah Wilderness, document special status plants, and assess invasive non-native plants. The project took place in 2013–2015, and 68 days were spent in the field. It coincided with three severe to exceptional drought years, the driest span for the site in recorded history. During the study large stands of Pinus monophylla, found in the Wilderness and much of the Southwest, experienced large die-offs. About 1300 plant specimens were collected for the study, which are deposited at RSA, CAS, and UCR. In total, 70 families, 240 genera, 457 species, and 477 minimum-rank taxa were documented, including those collected previously. A total of 28 non-native taxa (5.9% of the flora) and 26 special status plants (5.4%) were documented. Three special status taxa previously documented in the Wilderness were not relocated: Lewisia disepala (Montiaceae), Cordylanthus rigidus subsp. brevibracteatus (Orobanchaceae), and Delphinium purpusii (Ranunculaceae). A range extension for Eriophyllum mohavense (Asteraceae) was documented.

Assessment of artichoke hybrids under USA and Italian conditions and the hereditability of some important traits

Globe artichoke (Cynara cardunculus L. subsp. scolymus) hybrids are not Mendelian F1 with the consequent uniformity postulated by Mendel. This is due to the fact that hybrids are not originated from crosses between two pure lines; in fact, globe artichoke suffers strong inbreeding depression. Hence, the hybrid uniformity is one of the most important characteristics together with their improved characteristics for quality and morphological traits. To select hybrids lines, to be introduced for fresh consumption and industry processes, some uniform lines with promising characteristics have been selected in California in spring 2014 and evaluated in two contrasting environments such as the California desert of Brawley (33°02'48”N; 115°31'43”W) in spring 2014 and the Italian Mediterranean environmental conditions of Ladispoli (Rome) (41°57'29N; 12°07'10E) in spring 2015. The same procedures have been also adopted in the following year. The characteristics distribution among the evaluated hybrids has been studied utilizing multivariate and regression analyses. Hybrids have been also characterized by molecular markers to assess their genetic distance and parents' effects. Hybrids, on the base of their morphological traits, could be divided into 3 or 4 clusters the most important traits to discriminate the hybrids in all the years are earliness, spiny, distance between main head and first shoot, head shape, receptacle shape, bracts density, bract shape, and bract color. Hereditability values, of some important traits such as: earliness, plant height, presence of spines, presence of mucron, colour, head shape, and head compactness, have been estimated in globe artichoke. The differences between maternal and paternal hereditability are also reported and discussed.

Identification, Distribution, and Pathogenicity of Diatrypaceae and Botryosphaeriaceae Associated with Citrus Branch Canker in the Southern California Desert.

Several members of the families Botryosphaeriaceae and Diatrypaceae are known as canker and dieback pathogens of a number of woody hosts. Because desert citrus production in California can occur in proximity to table grape production, it was suspected that fungi associated with grapevine cankers might also be associated with citrus branch canker and dieback decline. To determine the fungi associated with branch canker and dieback disease of citrus in the southern California desert regions, surveys were conducted from 2011 to 2013 in the major citrus-growing regions of Riverside, Imperial, and San Diego Counties. Cankered tissues were collected from branches showing symptoms typical of branch canker and dieback. Various fungal species were recovered from necrotic tissues and species were identified morphologically and by phylogenetic comparison of partial sequences of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2), β-tubulin gene, and elongation factor 1-α genes with those of other species in GenBank. Four fungi, including Neoscytalidium hyalinum, Eutypella citricola, E. microtheca, and an unnamed Eutypella sp., were associated with branch canker. N. hyalinum was the most frequently recovered fungus from symptomatic tissues (31%) followed by E. citricola (10%), E. microtheca (4%), and the Eutypella sp. (2%). In pathogenicity tests, all fungi caused lesions when inoculated on 'Lisbon' lemon (citrus) branches. Lesions caused by the Eutypella sp. were significantly longer than those of the other Eutypella spp.; however, they did not differ significantly from those produced by N. hyalinum. The most-parsimonious unrooted trees based on the combined data of ITS and partial β-tubulin gene region sequences showed three distinct clades of Eutypella spp. (E. citricola, E. microtheca, and an unidentified Eutypella sp.). Similarly, ITS and partial translation elongation factor 1-α gene region sequences differentiated two species of Neoscytalidium, N. hyalinum and N. novaehollandiae. Identifying the diversity, distribution, and occurrence of these fungal pathogens is useful for the management of citrus branch canker and dieback disease in the desert citrus-growing regions of California.