Arizona Population Research Articles

PERFORATED PLATES AND THE SALADO PHENOMENON

Perforated ceramic plates have intrigued southwestern archaeologists since the late 1800s, when they were first encountered at the Classic period platform-mound sites of the Phoenix Basin and the protohistoric villages of the Hopi Mesas. Residues, contextual clues, and usewear suggest that perforated plates were used as base-molds in pottery making, and/or as potters’ turntables. Updated information regarding the function, dating, and distribution of these objects is presented in this paper. These data, along with the results of recent research in the San Pedro River Valley (including compositional analyses), establish a strong connection between immigrant groups from northern Arizona and the origin and spread of the Salado phenomenon that linked populations in central and southern Arizona, western New Mexico, and northern Sonora and Chihuahua.

Leaf Nutrient Levels for Pecans

Measurement of nutrients in leaf tissue is a practical method of monitoring the nutritional status of perennial crops such as pecan (Carya illinoinensis, Wang. C. Koch). Accurate interpretations require known standard concentrations for the crop and region. To determine standard concentrations for pecans, focusing on those grown in the desert southwest, we conducted a survey of 135 `Western Schley' pecan trees in Arizona for 2 years. Leaf nutrient concentrations and yield were collected for each tree. Leaf nutrient concentrations from the highest yielding trees (50th yield percentile) were used to calculate a mean and CV for each nutrient. Results were compared with data from New Mexico, Georgia, and Sonora, Mexico. Relatively large differences were noted in mean K, Ca, B, Cu, Fe, Mn, and Zn levels. Nutrient interpretation ranges were calculated based on Arizona population statistics using the balance index method.

Winter profile of plasma sex steroid levels in free-living male western diamond-backed rattlesnakes, Crotalus atrox (Serpentes: Viperidae)

Recent field studies on the reproductive ecology of western diamond-backed rattlesnakes ( Crotalus atrox) from populations in southern Arizona showed significant differences in the concentration of plasma sex steroids (testosterone, T; 5α-dihydrotestosterone, DHT; and 17β-estradiol, E2) throughout the active season (March–October), and peak levels were coincident with the two mating periods (late summer and early spring). There is, however, no information on levels of sex steroids during winter. Similar to most snakes, hibernating individuals of C. atrox are typically inaccessible, but in southern Arizona, where environmental conditions are typically mild during winter, adult males frequently bask at or near the entrances of communal dens. Basking activity, therefore, offers a unique logistical opportunity to assess the complete annual profile of plasma sex steroid levels in males of a temperate reptile in nature. From November to February, we measured levels of plasma T, DHT, and E2 in adult male C. atrox that were located basking at communal dens. Additionally, cloacal, core body, and ambient air temperatures were obtained to investigate potential relationships between body temperatures and levels of sex steroids. Mean levels of T, DHT, and E2 were relatively high, and the concentration hierarchy was T > DHT > E2. Mean levels of T, DHT, and E2 showed no significant variation across the four months of sampling; however, E2 levels decreased progressively. In the annul cycle, sex steroid levels during winter were not basal when compared to values obtained during the active season. Mean cloacal temperatures of basking males were significantly higher than core body temperatures of non-basking males (inside dens) from November–December, and in February, which suggests that one function of winter basking is to elevate body temperatures. Steroid levels, nonetheless, were not significantly correlated with cloacal temperatures. We suggest that future field studies of male C. atrox should: (a) investigate sex steroid levels in non-basking individuals and (b) test whether elevated levels of sex steroids during winter facilitate the large increases that occur in early spring, which are coincident with the second mating season. Our findings on the reproductive biology of C. atrox and other viperids are discussed in the context of the associated–dissociated model of reproduction.

Population Trends and Implications for Monitoring Cactus Ferruginous Pygmy Owls in Northern Mexico

Although once described as common in lowland central and southern Arizona (Bendire 1888, Fisher 1893, Breninger 1898, Gilman 1909, Bent 1938), cactus ferruginous pygmy owls (Glaucidium brasilianum cactorum; hereafter, pygmy owls) have been extirpated throughout much of their former range in Arizona. As a result, this northernmost subspecies of ferruginous pygmy owls (Van Rossem 1937, Johnsgard 1988) are now listed as endangered by the U.S. Fish and Wildlife Service (USFWS 1997, Hardy et al. 1999). Immediately south of Arizona in northern Sonora, Mexico, pygmy owls occur primarily in desert-scrub and grassland vegetation communities where woodlands are near stands of large saguaro cacti (Carnegia gigantea) (Flesch 2003a). Because pygmy owls are thought to be abundant in northern Sonora, these populations may prove critical for recovery in Arizona as well as for long-term persistence of pygmy owls in the Sonoran Desert. Natural or facilitated dispersal of pygmy owls from Sonora may augment populations in Arizona, especially when combined with habitat management (USFWS 2003). Numerous threats to pygmy-owl habitat exist in northern Sonora, however, including woodcutting, vegetation clearing for agriculture or buffelgrass (Pennisetum ciliare), and overgrazing, and there are few regulatory mechanisms in place to protect habitat. Despite the importance of pygmy-owl populations in northern Sonora, there are currently no data on population trends or on design parameters for population monitoring. Therefore, between 2000 and 2004 we monitored relative abundance of pygmy owls in northern Sonora, estimated temporal variation in relative abundance, and assessed the efficacy of different sampling designs for monitoring population trends. Our goals were to assess population trends, determine environmental factors that explained variation in trends, and evaluate the statistical power of our monitoring program for future monitoring efforts.

Inheritance of courtship song variation among geographically isolated populations of Drosophila mojavensis

Courtship song variation in many Drosophila species evolves rapidly and is thought to contribute to species-specific mate recognition. Studies using song playback experiments have shown that courtship songs are part of this recognition system in the sibling species D. mojavensis and D. arizonae. We examined variation in components of courtship songs in D. mojavensis to evaluate further the influence of courtship song divergence on sexual isolation. We found significant geographical variation in mean interpulse interval and mean burst duration, and significant variation in mean burst duration among geographically isolated populations from Baja California and mainland Mexico and Arizona. Significant regional differences in these song components were detected, as well as variation among populations nested within regions. Residual maximum likelihood (REML) analysis of F1 and F2 generations from a cross between a Baja California and an Arizona population revealed additive autosomal influences on mean interpulse interval with a significant effect of dominance and significant effects of the Y chromosome on mean burst duration. Regional differences in song variation and the type of genetic architecture observed are consistent with patterns of geographical variation associated with the colonization of the mainland from Baja California and documented differences in sexual isolation between populations.

Persistence of Gunnison’s prairie dog colonies in Arizona, USA

Although the five species of prairie dogs ( Cynomys spp.) are recognized as important components of grassland ecosystems in western North America, they have experienced major population declines due to poisoning, outbreaks of sylvatic plague, recreational shooting, and habitat conversion. From May 2000 to October 2001, we investigated 270 colonies of Gunnison’s prairie dog ( Cynomys gunnisoni) in Arizona. Because these colonies were classified as active in previous surveys (1987, 1990–1994, 1998), we were able to examine their persistence. Most (70%) of the colonies became inactive between the initial and recent surveys, with colony extinctions spanning our study area. Colony persistence was positively associated with the persistence of the nearest neighboring colony but was not associated with major vegetation type, distance to nearest neighboring colony, or initial size of the colony. The amount of area occupied by individual colonies varied between surveys, sometimes dramatically. We found little evidence that the reduction in active colonies was due to poisoning, recreational shooting, or habitat conversion. Rather, direct and indirect evidence suggest plague is the primary factor negatively impacting Gunnison’s prairie dog populations in Arizona. Currently, there is no way to control or prevent plague outbreaks in Gunnison’s prairie dog populations. To mitigate the effects of localized plague outbreaks on the overall population of this species, we suggest that Gunnison’s prairie dog be reintroduced to public lands throughout its historical range.

American Indian Diets and Nutritional Research: Implications of the Strong Heart Dietary Study, Phase II, for Cardiovascular Disease and Diabetes

This editorial review focuses on nutrition as a factor for the rise of American Indian cardiovascular disease (CVD) and diabetes. Based on the Strong Heart Dietary Study, Phase II (SHDS-II), Stang and colleagues (1) found that nutrient intakes varied little between the three American Indian populations in Arizona, Oklahoma, and the Dakotas and the national averages of the third National Health and Nutrition Survey (NHANES III). Although they recommend increases in dietary intake of B vitamins, antioxidants, and nutrients to reduce CVD, the dietary data did not account for the dramatic increase in heart disease or diabetes.

POPULATION GENETIC ANALYSIS OF SONORAN PRONGHORN(ANTILOCAPRA AMERICANA SONORIENSIS)

The endangered Sonoran pronghorn (Antilocapra americana sonoriensis) consists of only 2 small populations, 1 in Arizona and 1 in Mexico. Mitochondrial DNA sequence data and 5 microsatellite loci were used to compare levels of genetic diversity and differentiation between the 2 Sonoran pronghorn populations and between this subspecies and other selected pronghorn populations, both proximate and distant to the Sonoran pronghorn's current range. The data support a history of recent isolation of Sonoran pronghorn populations from those in Arizona, New Mexico, and Texas. Loss of genetic diversity due to bottlenecks and drift has been severe in both populations of the Sonoran pronghorn, but is most pronounced in the Arizona population. These results are discussed in terms of conservation management strategies.

Epidermal conductance as a component of dehydration avoidance in Digitaria californica and Eragrostis lehmanniana, two perennial desert grasses

Epidermal conductance ( g min) is water lost through the cuticle and stomata of plants when stomatal conductance is minimal. Low g min may affect survival of perennial grasses by maintaining tissue hydration during drought. If true, populations from environments where drought is severe may exhibit reduced g min compared to those from less arid environments. Success of invasive grasses may also be associated with reduced g min compared to non-invasive competitors. Using plants grown in a single environment, we measured g min of leaves from populations of Digitaria californica from environments with similar annual precipitation but differing in average drought severity (southern Arizona and western Texas, USA), and a population of the exotic species Eragrostis lehmanniana that has invaded sites occupied by D. californica in Arizona. Epidermal conductance was lower in the D. californica population from the more arid environment (Texas). Likewise, g min was lower in E. lehmanniana than in the Arizona D. californica population. Shoot biomass production as a fraction of g min was higher in E. lehmanniana than in the D. californica populations and was higher in the Texas D. californica population than in the Arizona population. This suggests that low g min may be a component of drought avoidance in these grasses.

Vegetation Cover and Forb Responses to Cattle Exclusion: Implications for Pronghorn

Cattle grazing is often implicated as a factor that reduces vegetative cover and the abundance of important forage plants for wildlife. Recent declines in northern Arizona populations of pronghorn (Antilocapra americana Ord) have focused public and scientific attention on the factors contributing to low fawn recruitment and the potential benefits of cattle removal. To further understandtheeffectsofcattlegrazing,westudiedthepotentialhidingcoverprovidedbystandingliveanddeadherbaceousmatter as well as forb richness and canopy cover following 5 years of cattle removal. Cattle removal increased horizontal hiding cover by 8% at a distance of 5 m (P ¼ 0.025), but had no statistically significant effect on the potential hiding cover at distances of 10 m (P ¼ 0.105) or 25 m (P ¼ 0.746). Forb species richness was 16% lower in exclosures than in an adjacent grazed pasture in 2001 (P ¼ 0.036), but no differences were observed in 2002 (P ¼ 0.636). The canopy cover of forbs was generally unaffected by cattle removal. These results suggest that curtailing or removing cattle is unlikely, by itself, to lead to rapid improvements in the hiding cover or forb availability for pronghorn on similar rangelands in northern Arizona. In this region, where immediate improvements in fawn survival and recruitment are important to population persistence, additional management actions should be considered.

How Census 2000 Data Suggest Hostility Toward Mexican-Origin Arizonians

Using the Arizona 5% Public Use Microdata Sample (PUMS) from the 2000 U.S. Census, we compare language-related figures for the Mexican-origin population with those for the total population. Additionally, we compare place of birth and educational attainment data for Mexican-origin persons who speak Spanish at home with those who speak English-only to provide a fuller characterization of these groupings. The 5% PUMS files contain individual records of responses to census questionnaires representing a 5% sample of the occupied and vacant housing units in Arizona and the persons in the occupied units. Our purpose is to more fully characterize the Arizona population to assist in improving education, language, and legal policy in the state, and we conclude that current legal, language, and education initiatives, such as efforts to impose an official English language and to restrict native languages in schools, are at odds with population figures and may signal hostility toward Mexican-origin Arizonians.

Vegetation Cover and Forb Responses to Cattle Exclusion: Implications for Pronghorn

Cattle grazing is often implicated as a factor that reduces vegetative cover and the abundance of important forage plants for wildlife. Recent declines in northern Arizona populations of pronghorn (Antilocapra americana Ord) have focused public and scientific attention on the factors contributing to low fawn recruitment and the potential benefits of cattle removal. To further understand the effects of cattle grazing, we studied the potential hiding cover provided by standing live and dead herbaceous matter as well as forb richness and canopy cover following 5 years of cattle removal. Cattle removal increased horizontal hiding cover by 8% at a distance of 5 m (P = 0.025), but had no statistically significant effect on the potential hiding cover at distances of 10 m (P = 0.105) or 25 m (P = 0.746). Forb species richness was 16% lower in exclosures than in an adjacent grazed pasture in 2001 (P = 0.036), but no differences were observed in 2002 (P = 0.636). The canopy cover of forbs was generally unaffected by cattle removal. These results suggest that curtailing or removing cattle is unlikely, by itself, to lead to rapid improvements in the hiding cover or forb availability for pronghorn on similar rangelands in northern Arizona. In this region, where immediate improvements in fawn survival and recruitment are important to population persistence, additional management actions should be considered.

Phylogeography in a galling insect, grape phylloxera, Daktulosphaira vitifoliae (Phylloxeridae) in the fragmented habitat of the Southwest USA

AbstractAim The Southwest USA is characterized by fragmented habitat for a range of species in a manner analogous to island systems. This can restrict gene flow among populations and may promote genetic differentiation and the evolution of endemic populations or species among the forested terrestrial islands. The region has experienced cycles of cooling and warming throughout the Pleistocene and the current isolation among populations may date back only c. 11,000 years. Thus, some studies have found genetic structure that predates the current distribution of organisms. The effect of habitat fragmentation on genetic structure was tested using DNA sequences in a highly specialized herbivorous insect, grape phylloxera, Daktulosphaira vitifoliae, that exhibits poor dispersal capacity and natal‐host associated mating that would seem to predispose it to genetic differentiation.Location Southwestern USA.Methods Phylogenetic trees and statistical parsimony networks were estimated from 458 bp of the mitochondrial cytochrome oxidase I gene sampled from 12 populations in Arizona and New Mexico.Results There was no evidence that populations were differentiated at the level of canyon or mountain range but significant structure was found at the larger level of geographic region. The pattern was confounded by the polyphyly of Southwest (SW) grape phylloxera relative to eastern populations and the coexistence of two highly divergent lineages within populations.Main conclusions An early split of grape phylloxera into the SW has resulted in some differentiation between populations in the Transition and Sonoran + Chihuahuan geographic regions. It is hypothesized that this differentiation has been overlaid by a more recent introduction of haplotypes from midwestern USA populations that occur primarily in the Transition region. The importance of sampling broadly is stressed.

Initial Therapy for Acute Myocardial Infarction: Socioeconomic Implications and Limitations

The optimal therapeutic approach for acute myocardial infarction (AMI) is still evolving; however, many would consider one of two basic options: "medical"-only thrombolysis or reperfusion, or an early (invasive), percutaneous coronary intervention (PCI). The decision about which is most appropriate depends (perhaps unfortunately) on more than just medical factors. That is, the choice for some patients is also limited by payor source and the technical capabilities at the site of the initial treatment. Practically speaking, a significant portion of the US population simply does not have the option of (at least, initial) PCI. Kino Community Hospital in Tucson, AZ, serves primarily an indigent population in southern Arizona, near the border with Mexico. This facility does not have in-house capability for PCI. Therefore, shortly after the publication of the original Thrombolysis in Myocardial Infarction (TIMI) 14 study (June 1999), we implemented their combination reperfusion protocol for the initial therapy of eligible patients admitted to the hospital with AMI. This report documents our experience with this medical reperfusion regimen in 42 patients over a span of almost 3 years. A retrospective chart review was conducted to evaluate outcome in 42 patients with ST-segment elevation myocardial infarction given the TIMI-14 reperfusion regimen. Resolution of ST-segment changes occurred in 30 patients (71.4%) [complete resolution in 25 patients (59.5%) and incomplete resolution in 5 patients (1.9%)], with major bleeding complicating the therapy of only 1 patient (2.38%) [corrected]. After stabilization in our facility, 28 patients (66.6%) needed PCI. This report summarizes the experience of a small county hospital where medical thrombolysis is the only immediate therapy available.

EFFECTS OF DESTRUCTIVE COLLECTING PRACTICES ON REPTILES: A FIELD EXPERIMENT

Abstract A basic tenet of wildlife management is that acceptable harvest methods should have little impact on populations other than eliminating or reducing the number of surplus individuals. We evaluated whether collectors who use destructive methods to harvest individual animals threaten reptile populations in Arizona, USA. Destructive methods usually involve permanent damage to cracks and crevices in rock outcrops that provide moist, cool shelter sites for reptiles. We surveyed 80 rock outcrops in an area slated for development. We treated half of the rock outcrops by imitating the activities of collectors using pry bars to overturn rocks and break open cracks, and we then resurveyed the rock outcrops. Multivariate repeated-measures analysis revealed that damaged rock outcrops support fewer reptiles than undamaged outcrops. We also observed species, sex, age-class, and seasonal effects due to treatment. To combat the growing problem of habitat destruction from reptile harvest, we recommend protection o...

Saguaro Distribution under Nurse Plants in Arizona's Sonoran Desert: Directional and Microclimate Influences*

The saguaro cactus, an icon of the American southwestern desert, defines the extent of the Sonoran Desert through portions of its range. Saguaros rely upon nurse plants for establishment and survival in the harsh temperature and moisture regime of the desert. Freezing temperatures limit the range of the saguaro to the north in Arizona. However, nurse plants extend the range of saguaros by providing more moderate conditions beneath their canopies. This study focuses on precisely these small, highly localized temperature variations, which, we suggest, are linked to regional-scale patterns of distribution of the species, particularly in marginal, cold-limited locales. We sampled 291 saguaros over thirty populations in Arizona, in the northern portion of their range. Saguaros establish under the south side of their nurse's canopy in the coldest parts of their range more often than expected, while a significant distributional bias is not observed in those in warmer, more moderate plots. To further investigate air temperature as a possible factor in the directional bias of saguaro establishment, we collected microclimate data under the north and south sides of the canopies of two common nurse plants, Cercidium microphyllum (a tree) and Ambrosia deltoidea (a shrub) in Phoenix, Arizona. South sides of nurses have significantly higher minimum temperatures than do the north sides. Survivorship in the coldest areas appears to be greatest under the south side of a nurse's canopy, where warmer wintertime microclimatic conditions occur. We suggest that within-canopy microclimatic variability under a single nurse plant may be reflected in regional distributional and in the survivorship patterns of saguaros throughout Arizona.

Exposure and risk estimates for Arizona Drinking Water

As part of the National Human Exposure Assessment Survey, a multistage sampling was used to estimate and compare exposures and risks associated with drinking water for two groups ‐ the population of Arizona and that of border communities. There had been some concern that the border communities' exposures would be higher than those of other parts of the state because of their proximity to Mexico, where environmental quality may not be as high a priority as it is in the United States. The two study populations were further categorized by gender, age, ethnicity, education, income, and building structure type and year of construction. For these subgroups, the study estimated and compared risks for arsenic, 1,3‐butadiene, chloroform, chromium, 1,2‐dichloroethane, dichloromethane, lead, nickel, and toluene. For almost all of the sample subjects, residue concentrations were below the drinking water guideline values of both Arizona and the US Environmental Protection Agency. Of the metals studied, arsenic was the only one with a population carcinogenic risk above the acceptable level of 1.0E‐6. Contrary to expressed concerns, average daily exposures and associated risks were estimated to be smaller in the border communities than in the Arizona population. For utilities, one finding deserving further study was that risks from tap water were estimated to be greater than risks from nontap water. Further research may be warranted to uncover the causes for these elevated risks.

Constructed wetland technology and mosquito populations in Arizona

Constructed wetlands and other aquatic habitat creation or restoration efforts offer both potential benefits and problems for arid areas. An unintentional consequence of these efforts has been the potential for an increase in local adult mosquito populations. Shallow water-emergent plant zones may provide ideal conditions for mosquito larval growth, and areas of high humidity, dense vegetation, and abundant birds and other wildlife may provide ideal conditions for adult mosquitoes. Three constructed wetlands in southern Arizona were studied over a period of years before and after they were constructed and operational. Mosquito populations were sampled using a variety of methods, primarily trapping of adults with CO 2-baited traps. Populations apparently increased, sometimes by several orders of magnitude, after wetlands became operational. Several methods of mosquito abatement were initiated and their results are discussed. However, no definitive conclusions can be drawn because no untreated areas were available for comparison and many factors that may have affected mosquito populations also changed. Based on the experience gained at these three sites, mosquito control is an especially important design and management component for constructed wetlands in arid environments with low background populations of mosquitoes.

Tassel-Eared Squirrel Population, Habitat Condition, and Dietary Relationships in North-Central Arizona

We examined the seasonal population dynamic of tassel-eared squirrels (Sciurus aberti) in north-central Arizona, USA, during 1996-1997 to assess relationships with forest structural habitat condition and dietary fungi use. Our 8 study sites averaged 66 ha and exhibited considerable variation in ponderosa pine (Pinus ponderosa) habitat structure. We conducted capture-recapture trapping during 3 seasons each year, for a total of 56,016 trap days and 2,542 captures of 450 squirrels. We attained population estimates with mean standard error ±10%. Density across periods ranged from 0.05 to 1.03 squirrels/ha, and fluctuated widely, at half our study sites, particularly between April and August trapping periods. Indices of recruitment averaged 0.14 juveniles/female. Survival rates averaged 0.78, with winter survival (0.63) significantly lower than other periods. We analyzed 382 fetal samples for seasonal hypogeous and epigeous fungi, of which 21 taxa were detected. Mean fecal fungal content was significantly higher in August (70.8% relative frequency) than in January (28.2%) and April (9.4%). Recruitment was strongly and positively related to both the number of interlocking canopy trees and August fungal content in fecal samples. August fecal fungal content was positively related to basal area for all tree species. Across all periods, squirrel density was positively related to fecal fungal diversity. Winter squirrel survival was inversely related to snow cover duration and positively related to dietary fungal diversity. Squirrel density fluctuations between April and August were positively tied to pine quadratic mean diameter. Forest management and restoration practices emphasizing intensive, widespread thinning may adversely impact tassel-eared squirrels and the fungi that provide food. Integrating squirrel habitat needs of interlocking canopies and other structural attributes in forest management will benefit squirrel populations.

Saguaro recruitment over their American range: a separation and comparison of summer temperature and rainfall

Saguaro establishment is limited by moisture in the Sonoran Desert summer, presumably by summer rainfall. This study provides a first look at saguaro regeneration in 30 Arizona populations, and decouples summer rainfall from temperature, despite the strong relationship between these two variables, to determine the effects of each. Partial correlations quantify the success of temperature and precipitation in predicting high juvenile survival. This study finds that, once saguaros receive enough summer moisture (i.e. a population exists), highest maximum July temperature is the variable that best predicts recruitment. Although ultimately limited by water, saguaro regeneration appears to be influenced by maximum summer temperatures more than precipitation. The population structure for all populations shows a large spike among the youngest individuals, suggesting that recruitment continues in populations of this protected species.