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Yellow rails (Coturnicops noveboracensis) winter along the U.S. coast, from North Carolina to Texas and southeastern Oklahoma. Although this rail is listed as a species of special concern in most of the provinces and states where it breeds, little is known about the winter ecology or population sizes of this secretive species. The goals of our study were to approximate numbers and determine age and sex ratios of yellow rails wintering in selected marshes at San Bernard National Wildlife Refuge (San Bernard NWR) in Brazoria and Matagorda counties, Texas. Yellow rails were banded in Spartina marshes from November 2009–April 2010. Feather samples were collected from each yellow rail for use in DNA sexing. We captured 170 yellow rails at the Cedar Lake Creek Unit of San Bernard NWR and recaptured 17 rails over the course of the study. We estimated that the population in marshes we sampled at San Bernard NWR (224.6 ha) from late November through mid-April consisted of 1,170 ± 300 individuals, or 5.2 ± 1.3 rails/ha. The highest ranked POPAN models suggest that the probability of recapture and the probability of entering the population were both time-dependent, while the probability of survival was time-independent. All yellow rails captured prior to January (n = 17) could be aged, with six (35.2%) aged as HY (Hatch Year), while 11 (64.7%) were aged as AHY (After Hatch Year). However, we were unable to conclusively assign ages to rails captured in January through April. Sufficient DNA was obtained from 59 yellow rails to determine that 33 (55.9%) were male. While the winter range of this species is widespread, it is likely that the coastal prairies of Texas are particularly important for this species given the large numbers and high density of rails encountered during this study.
Freshwater turtles are appropriate organisms for studying maternal investment in offspring because, unlike most long-lived vertebrates, turtles show high fecundities and most provide no parental care. We studied reproductive patterns of two emydine freshwater turtle species, the Texas river cooter (Pseudemys texana) and the red-eared slider (Trachemys scripta elegans) at Spring Lake, Hays County, Texas during the 2009 nesting season. Forty-six percent of all nesting Texas river cooters and 25% of all nesting red-eared sliders nested twice, with some Texas river cooters nesting more than twice. Mean egg mass, egg length, and egg width decreased in subsequent clutches in Texas river cooters. However, there was an insufficient sample size of subsequent clutches (n = 6) to draw conclusions for red-eared sliders. Red-eared sliders did not show a positive relationship between clutch size and body size. We found that in both species there was a positive relationship between egg width and egg mass in relation to maternal body size. However, only Texas river cooters showed a positive relationship between clutch size and maternal size, while only red-eared sliders showed a positive relationship between egg length and maternal size. By comparing reproductive parameters of these two coexisting populations, we concluded that the members of these two species allocate resources differently for reproduction.
We conducted a mark-recapture study on snapping turtles (Chelydra serpentina) at the headwaters of the San Marcos River, Hays County, Texas. The site is within a highly modified urban environment partially surrounded by a golf course, athletic fields, remnants of a theme park, and roadways supporting high traffic volume. We conducted the study from 1996–2011. We captured 179 turtles (89 adult females, 77 adult males, and 13 juveniles). We recaptured males significantly more frequently than females. We estimated population size to be 215 individuals with a density of 26/ha. The annual estimated probability of capture was 0.33, and estimated annual survivorship was 0.94 for males, 0.93 for females, and 0.81 for juveniles.
Historic surveys record screwbean mesquite (Prosopis pubescens) as widespread and dominant within upland riparian communities of the U.S. Southwest. I compared herbarium records and published surveys with surveys I conducted throughout the former range of P. pubescens. I found that this species has disappeared from 53% of its former range and has declined in density at eight of nine sites compared. Of 112 sites surveyed, only Ash Meadows National Wildlife Refuge has dense groves of P. pubescens over a large area. Prosopis pubescens remains in protected areas but not in urbanized areas. Declines of southwestern riparian species such as cottonwood and willow are well documented, but this is the first example of a declining species that is typically considered drought tolerant and is often found farther away from the stream course. Human alteration of rivers is therefore likely to be influencing plant communities as far away as a kilometer from the river itself.
Seedling establishment of many cactus species appears to be more frequent under canopies of nurse plants, which provide a less stressful microenvironment. Under these nurse plants, nutrient levels in the soil could be higher than in surrounding areas; these higher nutrient levels could promote higher seed germination. Seed burial under nurse plants may occur by seeds falling in the litter or in soil cracks; however, buried seeds are in the dark, which has been shown to inhibit seed germination for some cactus species. We measured germination percentage on nutrient-rich soil from under nurse mesquites and in soil from open spaces, and the effect of seed burial (buried and unburied seeds) on seed germination of three cactus species (Coryphantha durangensis, Peniocereus greggii, and Echinocereus longisetus) that grow under nurse plants in the Chihuahuan Desert. Echinocereus longisetus had very low germination across substrates. Coryphantha durangensis had higher germination on mesquite soil than on poor soil, and its buried seeds had lower germination than seeds on the soil surface. Germination of P. greggii seeds was higher on mesquite soil than on poor soil, and its buried seeds had lower germination than seeds on the soil surface.
We measured habitat associations in the rodent fauna at the Lyndon B. Johnson National Grassland in north-central Texas from May to August 2011. We recorded five species: hispid cotton rat (Sigmodon hispidus) was most abundant, followed by deer mouse (Peromyscus maniculatus), hispid pocket mouse (Chaetodipus hispidus), fulvous harvest mouse (Reithrodontomys fulvescens), and white-footed mouse (P. leucopus). Cotton rat density increased with grass cover; this effect was stronger for lower and middle quantiles of the abundance distribution. We found weak habitat correlates for P. maniculatus and R. fulvescens. This report is one of few describing the mammalian fauna of the vanishing Grand Prairie ecoregion.
We studied land-cover associations at nest sites and reproductive success of two Buteo species of conservation concern on the southern Great Plains, USA. The study area was in Cimarron County, Oklahoma, where land use is dominated by row-crop agriculture, livestock grazing, and grasslands enrolled in the Conservation Reserve Program (CRP). Ferruginous hawks (B. regalis) were uncommon and nested primarily in and around the Rita Blanca National Grassland. Swainson's hawks (B. swainsoni) were common and nested throughout the study area. Territories of ferruginous hawks contained more sandsage (Artemisia filifolia) habitat and less cropland and CRP lands than random sites, whereas territories of Swainson's hawks mirrored proportions of available landcover. Our results suggest that proportion of nearby sandsage habitat is an important factor in determining Swainson's hawk reproductive success. In addition, ferruginous hawk nest sites were located in areas that contained significantly more sandsage habitat than randomly selected sites in the study area. Nest-site availability may have constrained the distribution of buteos in our study area and is probably a major factor limiting nesting density of ferruginous hawks. Ferruginous hawks typically nest on man-made platforms (e.g., nest platforms and windmills) that in the study area were most common in and around the Rita Blanca National Grassland. Our results suggest that conversion of native grasslands to cropland may have negative consequences for ferruginous and Swainson's hawks. This relationship has been previously demonstrated in several studies of ferruginous hawks, but not for Swainson's hawks. In particular, loss of sandsage habitat on the southern Great Plains may have contributed to range declines in ferruginous hawks and decreased breeding success for Swainson's hawks.
The San Francisco Volcanic Field is one of the dominant volcanic fields on the Colorado Plateau, and its four million-year volcanic history has created a dramatic substrate age gradient. Sites within Pinyon-Juniper woodlands of the volcanic field share similar climate, elevation, and geology yet display dramatically different chemical and structural soil characteristics. The relative degree of soil development associated with ecosystem age strongly influences both the spatial distribution and composition of the local flora. A multiple response permutation procedure indicated that two distinct floristic assemblages occur; one in substrates younger than 150,000 years and one in older substrates. Indicator species analysis revealed that shrubs dominated younger, coarser, poorly developed volcanic soils while grasses and perennial herbs dominated older, finer, more nutrient-rich soils. Younger substrates harbored a higher degree of endemism, and species richness was positively correlated with ecosystem age.
Wildlife managers in the 21st century are challenged to maintain balance for wildlife and human use of the landscape. Because mountain lion (Puma concolor) habitat is often adjacent to urbanization in Arizona, mountain lions are ideal models to examine how human alteration of habitats influences life-history characteristics. We quantified mountain lion home-range characteristics and selection of vegetative associations in central and southern Arizona. We calculated 95% and 50% fixed kernel home ranges for eight female and 21 male mountain lions radiocollared in Payson, Prescott, and Tucson, Arizona, from August 2005 through August 2008. We assessed use of vegetative associations and urban areas within the study area (second order) and within the home range (third order). At both levels of selection at all study sites, mountain lions avoided human-dominated landscapes. At second-order selection, mountain lions preferred woodland habitat in Tucson and Prescott and chaparral in Payson. At the third order, lions in Tucson and Payson selected riparian and chaparral in Prescott. Season, mountain lion mass, and ungulate density had no effect on the size of home ranges. Home-range sizes for resident males ranged from 5,286 to 83,859 ha; transient males covered up to 409,195 ha. Home ranges for females ranged from 2,860 to 21,772 ha. Intensive development and conversion of large open spaces to small properties and subdivisions has caused increased loss, fragmentation, and encroachment into mountain lion habitat. Preserving natural landscapes for access to habitat patches is important in maintaining connectivity to ensure viable populations.
Where their ranges overlap, western yellow bats (Lasiurus xanthinus) often select roost sites in the fronds of native desert fan palms (Washingtonia filifera) as well as in other palm species. Roost occupancy patterns and characteristics of palm trees or palm oases important for roost selection across the Colorado Desert are unknown. We surveyed 41 palm oasis sites throughout the Colorado Desert and found 33 of those locations to have western yellow bat activity, and we confirmed day roosts at 19 sites. Compared to unoccupied palm sites, bats were found roosting in palm oases that were at higher elevations, had evidence of new palm growth, and where palms had a full range of skirt lengths. Our findings have implications for managing palm oases for western yellow bats.
Didymo (Didymosphenia geminata) is a freshwater colonial diatom native to northern latitude lakes and streams and, until recently, was considered indicative of high-altitude, low-temperature, nutrient-poor habitats experiencing little anthropogenic impact. In recent years, however, this diatom has expanded its geographic distribution into lower latitudes and altitudes. In early 2012, we discovered a bloom of didymo in the Lower American River below Nimbus Dam in Sacramento County, California. Due to production of large masses of extracellular stalks that can smother stream substrates, and its proximity to a salmonid habitat restoration project, discovery of didymo prompted us to conduct a study of its effects on benthic macroinvertebrates, an important food source for juvenile salmonids. In May and June 2012, we sampled benthic macroinvertebrates in a reach of the main channel where didymo was abundant and in a nearby reach on a side channel where environmental conditions were similar but didymo was seemingly rare or absent. We found significant differences in taxonomic composition and abundance of macroinvertebrates inhabiting the two reaches. Higher numbers of Chironomidae (midges), Gammaridae (scuds), Hirudinidae (leeches), Hydroptilidae (microcaddisflies), and total macroinvertebrates were recorded in the main channel. In contrast, higher numbers of Baetidae (baetid mayflies), Glossosomatidae (saddlecase caddisflies), and Tipulidae (crane flies), along with a higher percentage of combined Ephemeroptera, Plecoptera, and Trichoptera (%EPT), were recorded in the side channel. We also recorded higher values for three common measures of taxonomic diversity (Margalef richness, Pielou's evenness, Shannon-Wiener diversity) in the side channel. From these initial observations, we tentatively concluded that the didymo bloom has influenced benthic macroinvertebrate composition in the Lower American River.
The live-bearing fish genus Brachyrhaphis from Central America has become an important model system in evolutionary and ecological research. This paper presents some of the first work on the Cardinal Olomina Brachyrhaphis roseni since this species was first described. Specifically, I present data on populations that suggest that the elevational distribution of B. roseni is dramatically different than what was previously thought. This work will provide valuable background information for future studies of the ecology and evolution of this species.
The western scrub-jay (Aphelocoma californica) is a common nest predator and has been documented depredating nests of the federally endangered golden-cheeked warbler (Setophaga chrysoparia), a woodland songbird, in central Texas. We conducted opportunistic and transect surveys for western scrub-jays across two vegetation classes (woodland and shrub-scrub) to investigate the proximity of scrub-jays to golden-cheeked warblers breeding in a fragmented landscape. We used a chi-square test to compare the number of observed and expected scrub-jay detections for each vegetation class. To investigate if scrub-jays are an edge-occupying species, we compared the distance to nearest vegetation edge of actual scrub-jay detections to a null distribution of mean random distances. We found that scrub-jays occur in areas closer to vegetation class boundaries but do not appear to prefer one vegetation type over the other. Our findings suggest that golden-cheeked warblers may have higher nest predation risk in fragmented areas of their breeding range.
At Southern Methodist University campus about 6 miles south of Taos, New Mexico,, we recovered tetrathyridia of Mesocestoides in five Peromyscus maniculatus in the summers of 2008 (3 of 129, 0.023%), 2009 (0 of 98, 0%), 2010 (1 of 112, 0.008%), 2011 (0 of 88, 0%), and 2012 (1 of 86, 0.011%). Tetrathyridia from the body cavity of one of the five infected mice were injected into the peritoneal cavity of laboratory white mice, Mus musculus. Our later examination of the laboratory mice revealed heavy infections of tetrathyridia continuing to reproduce asexually. Here we provide important new information on the prevalence of asexuality among tetrathyridia and underscore the need for further study of this variation among metacestodes of this cosmopolitan genus.
I describe an occurrence of interference competition between a group of five male scissor-tailed flycatchers (Tyrannus forficatus) and 11 blue jays (Cyanocitta cristata). The interaction was initiated by a subset of two blue jays and concluded after nine additional blue jays arrived at a perch on a sweet gum (Liquidambar styraciflua), causing the scissor-tailed flycatchers to leave the perch and area. Both species exhibited intraspecific cooperation during the encounter.
Most reports of anuran visual displays (especially those involving extension of the back legs) are of tropical species living within noisy habitats. Here, we provide a descriptive report of visual displays involving back leg extension in a temperate anuran, Blanchard's cricket frog (Acris blanchardi). We observed male cricket frogs engaging in bouts of display, lasting an average of 2.9 min and incorporating both visual and acoustic signals. In a typical display bout, frogs near each other began circling (during a chorus at the pond) within a small area while extending their back legs and occasionally vocalizing. Rarely, the frogs would attack one another by hopping onto, then off, an opponent. Bouts ended when individuals stopped displaying while remaining near each other. The most common behaviors observed during a display bout, in order of decreasing frequency, were leg extensions, direction changes, forward movements, and vocalizations. These observations increase prospects for the study of evolution of visual displays in anurans occupying relatively open, quiet habitats.
The variable platyfish (Xiphophorus variatus), native to Gulf Coast drainages of northern Mexico, is a popular aquarium fish with a long history of introduction globally. We document the first Texas occurrence of this species, and its persistence in highly urban Waller Creek in the city of Austin since at least 2004. The population appears to be limited to Waller Creek, having not yet been found in neighboring creeks where similar habitat exists. We observed individuals in situ and in the lab surviving in 7°C water, well below published thermal minima, and report its persistence through one of the coldest winters in Austin's recorded history. Its persistence may be due to a combination of its cold tolerance and the presence of thermal refuges. In the lab we found that individuals purchased in a local pet store and individuals from Waller Creek had the same cold tolerance.
Parthenogenetic reproduction in several all-female species of whiptail lizards (genus Aspidoscelis) does not preclude the occasional production of extreme variants. An adult lizard with a unique combination of dorsal color pattern, scutellation, and meristic characters captured 20 August 2013 approximately 200 m east of the Rio Grande in Bosque Farms, Valencia County, New Mexico, was inferred to be an extreme variant of triploid, hybrid-derived Aspidoscelis exsanguis which was also observed near the point of capture. There was no basis for identifying the specimen as a tetraploid hybrid because morphology did not reflect that origin and no gonochoristic species (e.g., Aspidoscelis marmorata or Aspidoscelis inornata) was known to occur at the site. Morphological analyses also ruled out the possibility that it could be an extreme variant of diploid parthenogenetic Aspidoscelis neomexicana, which is syntopic with A. exsanguis in Bosque Farms.
Arizona gray squirrels (Sciurus arizonensis) are endemic to the southwestern United States and northwestern Mexico. Despite classification as a species of concern in portions of its range, little is known about Arizona gray squirrels. We investigated survival and causes of mortality for a population of squirrels in the Huachuca Mountains in 2007 and 2008. Adult survival was high and did not differ between sexes, with probability of survival >0.70 one year postcapture. Predation was the most common known cause of mortality; consequently, management plans should account for habitat characteristics that provide protection from predators when managing for Arizona gray squirrels.
The Balsas Basin is one of the largest and most varied formations in Mexico with a high degree of endemism and variety of flora and fauna. To date, there has been no in-depth study of spider diversity in this region. This paper details a survey of spiders found in the Balsas Basin, collected at 20 localities in the states of Guerrero, Puebla, and Morelos between 1997 and 2011. During our survey, we identified 437 mature spiders and grouped them into 24 families, 53 genera, and 56 species and sorted as follows: we found 15 species in Guerrero, 29 in Morelos, and 20 in Puebla. We found five new country records for Mexico and 28 new state records (nine for Guerrero, 10 for Morelos, and nine for Puebla), with a total of 13 possible new species. We estimated beta diversity (change in species composition), and indicated that most localities shared only a few species (fewer than 40%), which suggests that each locality has a unique suite of species with specific habitat characteristics. This first report on spiders from this extensive region shows the necessity for further study in the areas of biodiversity, ecology, and conservation biology.
The African clawed frog (Xenopus laevis) is an invasive amphibian in at least 15 countries. In Mexico, only occasional records have documented it in the state of Baja California. In May 2013, we discovered a population at Puente el Morro in Rosarito. In a 1-h session of trapping, we captured 106 individuals (adults and juveniles) at a small pond. We did not see eggs, tadpoles, or reproductive activity, but lengths of frogs indicate that some have reached sexual maturity. This discovery indicates the need for conservation plans and action against X. laevis dispersion, especially in Mediterranean zone climates.
The genus Ictalurus is represented in northwest Mexico by a taxonomically problematic group of populations informally treated as the Ictalurus pricei complex. Several morphological characters separate the undescribed catfish populations (Sinaloa catfish) in the Culiacan River and San Lorenzo River basins from the Yaqui catfish (Ictalurus pricei), the only catfish species described from the region. In this paper, a phylogenetic analysis of cytochrome oxidase subunit 1 supports the monophyly of the I. pricei complex (Yaqui and Sinaloa catfishes). The complex appears closely related to Ictalurus lupus, another species from the American Southwest.
The Pecos gambusia (Gambusia nobilis) is an endangered poeciliid native to western Texas and eastern New Mexico. The decline of G. nobilis in Texas is likely the result of habitat alteration and introduction of potentially invasive congeners (e.g., the introduced largespring gambusia, Gambusia geiseri). In the East Sandia Cienega, observers have noted mating between G. geiseri and G. nobilis. Because potential hybridization between native and introduced species could have detrimental effects on reproductive fitness, we compare mean brood size, gonadosomatic indices, and standard length of both G. geiseri and G. nobilis as a first step in assessing the impacts of G. geiseri introduction in this area.