Geographic distribution among members of the Sigmodon hispidus complex (Sigmodon hirsutus, S. hispidus, and S. toltecus) were examined using DNA sequences from the mitochondrial cytochrome-b gene. Geographic distribution of each taxon was defined based on DNA sequences obtained from 69 samples (19 newly obtained and 50 from previous studies) collected from North, Central, and South America. These data indicated that S. hispidus is restricted to the southern one-half of the United States and northeastern Mexico (Nuevo León and Tamaulipas), S. toltecus occupies the eastern one-third of Mexico (central Tamaulipas) to northern Honduras, and S. hirsutus is distributed from central Chiapas and southeastern Oaxaca to northern South America (Venezuela). The newly collected data extend distributions of S. hispidus from the southern United States southward into northeastern Mexico and that of S. toltecus from Chiapas, Mexico, southward to Honduras. Genetic divergence and patterns of phylogeography were examined within each taxon.
Much is known about movements of female white-tailed deer (Odocoileus virginianus). However, relatively few investigations have been directed toward free-ranging male deer and even fewer have involved mature (4 years old) males. Our objectives were to characterize utilization distributions and site fidelity, and to evaluate the subdominant-dominant-floater model using an extensive radiotelemetry dataset collected from male deer >or= 1.5 years old in southern Texas. We generated home ranges and core areas of 96 males from 16,696 location estimates collected during January 1993-June 1995. Annual home-range size did not differ among age categories. Males maintained smaller home ranges during spring than during other seasons and old males (>or= 7 years old) displayed smaller seasonal home ranges than young or mature males. Deer exhibited greater fidelity to home range during summer than during spring, prerut, and rut seasons. We detected limited evidence supporting the subdominant-dominant-floater model. The high fidelity to home range between years that we saw suggests little between-year shifting; however, annual home-range sizes exceeded the acreage of most private landholdings, which should be considered when formulating management plans.
Nearctic Plecoptera inhabit well-oxygenated, usually, permanent mountain streams, exhibit low vagility and possess distributions which can be excellent indicators of environmental changes which took place during the Pleistocene. Present distribution patterns of Nearctic stoneflies in the Sierra de San Pedro Martir of Baja California and the Sierra Madre Occidental and Sierra Madre Oriental of mainland Mexico can be attributed to the pluvial environments of the Pleistocene when suitable habitats were much more extensive. The Nearctic stonefly fauna of Baja California is an extension of that fauna found in the southwestern United States, especially California. In the past, stoneflies were able to cross the discontinuity between the southern Rocky Mountains and the Sierra Madre Occidental and disperse into northern, central and southern Mexico. Only one Nearctic species is known from the Sierra Madre Oriental. Previously, four Nearctic stoneflies had been reported from Mexico, all Amphinemura Ris species. After extensive collecting in the states of Baja California, Chihuahua, and Sonora, we have found 21 additional species in 11 genera from six families. The Amphinemura venusta complex contains six Mexican endemics (three undescribed).
The purpose of this study was to compare prey types and prey volume between the diets of two whiptail lizards (Teiidae), Aspidoscelis marmorata (a bisexual species) and A. tesselata (a unisexual species), that occur syntopically on the Indio Mountains Research Station (IMRS), Hudspeth County, Texas, which is located in a Chihuahuan Desert landscape. Because their home ranges overlap extensively, it was hypothesized that there would be resource partitioning in the diets between the two forms. Stomach contents of 69 individuals of A. marmorata and 21 individuals of A. tesselata were examined and determined to contain only arthropods. Taxa consumed by A. marmorata included species in 14 orders, while species in eight orders were consumed by A. tesselata . Both species eat primarily individual isopterans (92.7% in A. marmorata ; 94.5% in A. tesselata ). By volume, Homoptera (30.3%), Araneae (23.2%), Orthoptera (13.3%), and Isoptera (13.0%) compose 80.0% of the diet of A. marmorata ; whereas Orthoptera (29.7%), Homoptera (29.7%), Araneae (16.6%), and Isoptera (16.2%) make up 92.2% of the diet of A. tesselata . The results indicated that both species are opportunistic feeders that compete with each other for available food resources. This competition seems to be reflected in differences between densities of the species ( A. tesselata was present in lower densities). However, slight differences in their ecologies and available food resources may have accounted for the coexistence of both species in the study area.
I studied the age, growth, feeding, and behavior of Sacramento squawfish, Ptychocheilus grandis, in a small stream to provide basic life history information on this species in a habitat where it is often abundant. Young-of-year squawfish in Bear Creek grew throughout the summer and early fall. Mean back-calculated lengths of squawfish ranged from 65 mm SL (standard length) at age I to 257 mm SL at age IV. Mean back-calculated lengths varied among year-classes only at age I, with lengths varying from 55 mm SL for the 1979 year-class to 84 mm SL for the 1977 year-class. Bear Creek contained a large number of small mature fish (ages III and IV), but fish older than age IV were rare. Young squawfish (≤100 mm SL) consumed primarily insects and occasionally small fish. Fish became the dominant prey (>50% by weight) at a size of 100 to 150 mm SL. When squawfish were assigned to 50-mm size-classes, diet diversity calculated by size-class (proportions based on the summed contents of all individuals in the size group) was greatest for fish 51 to 100 mm SL. Individual diet diversities (proportions based on individual gut contents) did not vary among size-classes. Stomach fullness of squawfish ≤100 mm SL declined from May through December 1980. Individual diet diversity of fish ≤100 mm SL did not vary over the same time period. Large squawfish (100 to 500 mm SL) were sedentary and exhibited little movement within or between pools, during observations of summer, daytime behavior. Large squawfish did not interact aggressively with each other or with similar-sized Sacramento sucker, Catostomus occidentalis. A flexible pattern of growth of young-of-year, partitioning of food among life stages, and the sedentary, nonaggressive behavior of large squawfish all contribute to the success of the species in small streams.
Wild boars (Sus scrofa) are increasing in abundance and geographic distribution throughout North America. Our objectives were to determine daily and hourly activity patterns. We placed global-positioning-system collars on 25 wild boars from two sites in southern Texas. Wild boars at both sites displayed highly nocturnal activity patterns, and during the dormant and early growing season, activity increased with rising temperatures.
Fewer mammalian species occurred on summits of sheer-walled buttes than occurred in similar "mainland" control sites, but density of small mammals on buttes equaled or exceeded mainland density. Peromyscus crinitus, the only terrestrial mammal on Jug Butte, occupied a larger habitat niche there than in control areas. No such niche expansion was noted for P. crinitus on Junction Butte, where four other species of small mammals (Eutamias quadrivittatus, Neotoma lepida, Neotoma cinerea, Peromyscus truei) and at least one large mammal (Canis latrans) also occurred. At least 18 species of terrestrial mammals inhabit the control sites. It is hypothesized that the species number remains static on each butte and is a function of the unique dispersal abilities of each species and does not represent an equilibrium between recurrent colonization and extinction.
Carrion community composition was examined in 40 rabbit carcasses at three northern Chihuahuan Desert study areas in Texas and New Mexico from May to August, 1976. Four seral stages of decomposition are described for the carcasses: Fresh, Active, Advanced Decay, and Dried. Of 80 arthropod species collected, 63 are identified as participants in the carrion community. Six vertebrate forms were participants. Probable feeding roles of arthropod and vertebrate taxa are presented. Diversity and concentration of dominance were calculated for seral stages, and relationships to resource diversity and food chain complexity are discussed. Removal efficiency of vertebrates and colonization efficiency of arthropods are correlated to describe a probable abbreviation of arthropod carrion communities in small carcasses; possible implication for arthropod adaptations are presented. No direct correlation appeared between carrion community composition and area meteorological conditions.
La plaga bubónica es una enfermedad bacterial introducida para quien las pulgas (Siphonaptera) son los vectores principales. Los perros de la pradera de Utah (Cynomys parvidens) son muy susceptibles a la plaga, y colonias enteras generalmente desaparecen poco después de la llegada de la plaga. La inyección en las madrigueras con Pyraperm (un polvo insecticida) mata a las pulgas y detiene inmediatamente la propagación de la plaga en las colonias. Entonces, es posible que los polvos de insecticidas puedan jugar un papel importante en la conservación de los perros de la pradera.
The vegetation from abandoned mine sites in the Picher lead zinc mining field in Ottawa County, Oklahoma, structurally and compositionally resembles that of other disturbed habitats in the eastern part of Oklahoma. The overstory dominants are cottonwood (Populus deltoides) and black willow (Salix nigra). Winged sumac (Rhus copallina), American elm (Ulmus americana), and black cherry (Prunus serotina) were the most important understory species. The seeds of the characteristic overstory and understory vegetation are primarily dipersed by wind and birds. Inefficient seed dispersal is suggested as a reason for the almost complete absence from these sites of the upland forest dominants, oaks (Quercus spp.) and hickories (Carya spp.) Soil analyses revealed the sites have high concentrations of heavy metals, however, their potential toxic effects may have been alleviated to some extent by the high pH and soil calcium concentrations. Macronutrients are not limiting in the soils from these sites. Similarity indicies and unidimensional site ordination were used to investigate the intrasite variation and reveal a correspondence between the individual site vegetative composition and soils.
This study examines winter abundance patterns of three groups of song birds across the south-central United States--the phoebes (Sayornis), thrashers (Toxostoma and Oreoscoptes), and bluebirds (Sialia). The analysis was done on 15 years of National Audubon Society Christmas Bird Count data that were collected in an area encompassing most of Texas, Oklahoma, and part of New Mexico. There was no statistically significant east-west variation in group abundances, but a transition from eastern to western forms within each group occurred between the 98th and 102nd meridians, and the transition was abrupt. A significant biogeographic boundary appears to exist within two degrees on either side of the 100th meridian.
The effects of a cold front, which decreased water temperatures to freezing, on estuarine fish near Redfish Bay and Port Aransas, Texas are noted. Most Texas estuarine fish appear able to tolerate 6-7 C; torpidity and death occur below this level. A few species, notably the pinfish, Lagodon rhomboides, and the spotted sea trout, Cynoscion nebulosus, can tolerate lower temperatures.
The external morphology and internal anatomy of leaflets from four disjunct Sophora taxa were examined in order to establish relationships among extant populations and to determine their relationship with fossil remains presumed to be Sophora. Several leaflets of the fossil material were found with other paleovegetative samples dated at 15,695 ± 230 radiocarbon years ago. These leaflets were compared to samples from four widely disjunct extant taxa of Sophora from the Chihuahuan and Sonoran desert region of the southwestern United States and Mexico. Scanning electron micrographs of surface modifications were used to demonstrate similarities among the taxa in question. Leaflets were cleared and stained in order to examine venation patterns. These data, along with comparative studies of internal structures, clearly identified the fossil material as a Sophora and provided additional evidence indicating a monophyletic origin for all five taxa. Based on this and previous work by the senior author, a proposed phylogenetic sequence originating in the Pliocene is suggested. A putative ancestral type for the complex is also proposed.
Recovery of degraded semiarid rangeland is influenced by the degree of soil erosion and changes in soil physical and chemical properties that follow the loss of herbaceous cover. The objectives of this study were to compare changes in physical and chemical properties of a chaparral soil protected from grazing for 18 years, and to evaluate these changes relative to succession and threshold paradigms. Litter and soil samples were collected beneath shrub live oak (Quercus turbinella), birchleaf mountain mahogany (Cercocarpus betuloides) and open spaces between shrubs in a livestock exclosure and the surrounding grazed area. Additional soil was collected beneath shrub live oak and from open spaces between shrubs for a bioassay of soil fertility within the exclosure and the grazed area using oats (Arena sativa) as the indicator species. Percentage silt and clay were greater and percentage sand was lower within the exclosure. Organic carbon and total nitrogen concentrations were greater in soil beneath mountain mahogany and from shrubless openings within the exclosure compared to the grazed area, but not beneath shrub live oak. Soil from shrubless openings in the exclosure produced greater oat shoot weights compared to soil from open spaces in the grazed area, but there was no difference in oat shoot weights between grazed and protected areas beneath shrub live oak. Shoot weights increased in response to nitrogen and nitrogen + phosphorus, but not phosphorus alone, indicating the site was primarily nitrogen limited. Improvements in soil physical and chemical properties within the exclosure did not result in recovery of herbaceous vegetation in open areas between shrubs. A very heterogeneous distribution pattern in soil properties, characterized by large differences between soils under shrubs compared to open areas between shrubs, was evident within the exclosure and in the grazed area, indicating the presence of a degraded ecosystem. Improvements in soil physical and chemical properties within the exclosure represent an upward trend within a stable threshold of lower productivity, rather than a slow return to climax condition.
Isla Rasa in the Gulf of California has been recognized as an important seabird breeding island for more than 150 y. Yet during most of this period, the island suffered human disturbances that severely reduced seabird nesting success. Today, nearly two decades after disturbances ended, Isla Rasa supports about 90% of the global populations of Heermann's gulls (Larus heermanni) and elegant terns (Thalasseus elegans), plus smaller populations of other species. However, the recently available 1856 journals of Italian naturalist Federico Craveri, and the oral traditions of the Comcaac (Seri people), suggest that the array of nesting species has changed. Apparently, California brown pelicans (Pelecanus occidentalis californicus) abandoned Isla Rasa as a breeding site at the onset of disturbances, and terns first colonized it around 1920.
Cordylophora lacustris (Coelenterata) was collected from five inland fresh-water habitats across Texas, the first records for the species in the state. Morphological variations were observed in specimens from different habitats, a phenomenon that seems correlated to seasonal growth patterns and to physicochemical differences between the aqueous environments. The species is adaptable to a variety of ecological conditions and is probably more widespread than the literature indicates.
Sceloporus torquatus minor is a name Cope proposed for lizards of the torquatus group from "Zacatecas" in 1885. Subsequently, the epithet minor was transferred to S. jarrovi and the type locality of S. j. minor was restricted to the "Valparaiso Mountains" in western Zacatecas. Our comparison of the two original syntypes of S. j. minor with lizards from the Valparaíso Mountains indicates that they do not represent the same taxon. The type locality of S. t. minor Cope is herein restricted to eastern Zacatecas where the resident lizards closely resemble the two syntypes; one of these syntypes (USNM 26167) is designated as the lectotype, the other (USNM 26166) as a paralectotype, of S. t. minor Cope. /// Sceloporus torquatus minor es un nombre que Cope propuso para el grupo de lagartijas torquatus del estado mexicano de Zacatecas en el año de 1885. Después, el epíteto minor fue transferido al S. jarrovi y la localidad tipo de S. j. minor fue restringido a las Montañas Valparaíso del oeste de Zacatecas. Nuestra comparación de los dos sintipos originales del S. j. minor con las lagartijas de las Montañas Valparaíso nos indica que no representan el mismo grupo taxonómico. La localidad tipo del S. t. minor Cope está restringida al oriente de Zacatecas, donde las lagartijas son muy similares a los dos sintipos; uno de estos sintipos (USNM 26167) ha sido designado como lectotipo, el otro (USNM 26166) como un paralectotipo del S. t. minor Cope.
Variation was evaluated in 206 adult Dipodomys elator from three populations in northern Texas. Males were significantly larger then females for 10 of 20 characters, and significant geographic variation occurred in 11 of 19 characters for males and 9 of 19 characters for females. Males from Hardeman Co. were significantly larger than females for total length, body length, hind foot length, greatest depth of cranium, and zygomatic width, whereas those from Wichita Co. were significantly larger for basal length of cranium and nasal length. Females from Wilbarger Co. averaged larger than those from Hardeman and Wichita counties in most characters but those from Hardeman Co. were significantly largest for total length and tail length and smallest for basal length of cranium. Sexual differences were greater in specimens from Hardeman and Wichita counties than in specimens from Wilbarger Co.
In September 1901, Professor L. M. Underwood and Mr. A. D. Selby engaged in a botanical collecting trip in west-central Colorado to obtain vascular plants as a contribution to the flora of the Rocky Mountains. An itinerary of the trip has been reconstructed from information on the labels of a set of 718 specimens retained by Mr. Selby now in The Ohio State University Herbarium and from data in the field notebooks of Professor Underwood at the New York Botanical Garden. Twenty taxa named by Per Axel Rydberg based on the collection are enumerated with the citation of the original publication, the locality, date, and number on the specimen, and the designated kind of type in The Ohio State University Herbarium.
A new species of flea is described from the Sierra Madre del Sur in the state of Guerrero, México, with specimens from the collection of the late Dr. Alfredo Barrera deposited in the Museo de Zoología "Alfonso L. Herrera," Facultad de Ciencias, Universidad Nacional Autónoma de México. The mammalian hosts are Peromyscus sp., Peromyscus megalops auritus, and Reithrodontomys sp. A brief discussion on the distribution of this genus is presented. /// Se describe una nueva especie de pulga de localidades en la Sierra Madre del Sur en el estado de Guerrero, México, con especímenes de la colección "Alfredo Barrera," del Museo de Zoología "Alfonso L. Herrera," Facultad de Ciencias, Universidad Nacional Autónoma de México. Los hospederos mamíferos son, Peromyscus sp., Peromyscus megalops auritus, y Reithrodontomys sp. Se discute brevemente la distribución de este género.
Using U.S. Forest Service fire occurrence records, we found that during the 29-year period 1955 to 1983, 1611 fires burned a total of 41,447 ha in the 391,000-ha desert portion of Tonto National Forest, Arizona (TNF). Lightning-caused fires, though fewer in number, burned approximately twice the area of fires set by people. Fires were numerous from May through August, but area burned was greater during June than all other months combined. Using average annual hectares burned and subtracting areas of overlap between fires, we estimated that 294 years were required for all parts of the TNF desert to burn. Ignoring overlap, estimated time required for an area of equal size to the TNF desert to burn is 274 years. Increasing fire occurrence during the 29-year period studied might be due to wetter-than-normal winters toward the end of the period, fuel provided by exotic annual plants, improved fire detection and reporting, and ignition by people.
Two series of owl pellets, collected near Mathis, Texas, were analyzed. Changes in percentages of prey items from 1956 to 1959 indicate an increase in the numbers of Sigmodon hispidus. This increase caused a reduction in the use of other prey species by the owls. The foraging habits of the owls changed with an increase in food supply in the nesting area.
We report a fifth locality and natural history notes for the Mexican water mouse Rheomys mexicanus. This is the third record for Oaxaca, and it corresponds to the northernmost known locality for the genus Rheomys and for the species R. mexicanus. In addition, it represents the highest elevation known for the species.
A study of zooplankton composition and density was conducted in Flaming Gorge Reservoir, Wyoming-Utah, in 1983 and 1984, and the data were compared to a study in 1965 and 1966 (3 and 4 years after impoundment). Zooplankton density tended to be less in the 1983-1984 samples than in the 1965-1966 samples for most species, while mean size was substantially less in the 1983-1984 samples than in the 1965-1966 samples for Daphnia pulex, Diaptomus sp., and Cyclops bicuspidatus thomasi. Three rotifers found in 1983 and 1984 (Kellicottia longispina, Synchaeta sp., and Squatinella sp.) were not reported in 1965 and 1966.
Eggshell thickness, levels of pollutant residues, and population status of the white-faced ibis (Plegadis chihi) were monitored in Texas from 1969 through 1976. Texas ibis nesting populations declined by 42%. Reproductive success apparently was limited by DDE-induced shell thinning and by dieldrin-caused mortality. Eggshells averaged 4% to 10% thinner than the pre-1943 mean thickness. Shells of numerous crushed eggs exceeded 20% thinning. Mean DDE residues in randomly collected eggs decreased from 0.94 ppm in 1970 to 0.25 ppm in 1976. DDE was higher, averaging 2.5 ppm, in thin-shelled eggs. DDE was negatively correlated with shell thickness. Dieldrin and PCB residues increased slightly from 1970 to 1976, but neither was correlated significantly with shell thickness. Residues in brains of many dead and dying ibises collected during years of extreme reproductive failure, 1970 and 1973, contained between 5 and 25 ppm dieldrin. Ibises were exposed to aldrin and dieldrin by feeding in rice fields where aldrin-treated rice seed was planted. Improved nesting success in 1976 may have been related to declining residues of DDE and to the discontinued use of aldrin in rice fields.