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Sequences of the mitochondrial (mt) NADH dehydrogenase subunit 5 gene (ND5) were acquired to assess genetic diversity and female effective population size (Nef) of two forms of Cyprinella (C. lepida and C. sp. cf lepida) and two species of Dionda (D. serena and D. texensis) in headwaters of three rivers in the upper Nueces River basin in central Texas. As documented in prior studies, two divergent clades of haplotypes of mtDNA were found in both genera: one in the Frio and Sabinal rivers, representing C. lepida and D. serena; one in the Nueces River, representing C. sp. cf lepida and D. texensis. Levels of variation in mtDNA from C. lepida in the Sabinal River and D. serena in the Frio and Sabinal rivers were comparable to or considerably lower than values documented for populations of several threatened or endangered cyprinids. Estimates of Nef for C. lepida in the Frio River and C. sp. cf lepida in the Nueces River were low, suggesting that adaptive genetic variation through time may be compromised. Of all populations sampled, only D. texensis in the Nueces River appears at present to be genetically stable demographically. An unexpected finding was two individuals resembling C. lepida in the Frio River with a haplotype referable to C. sp. cf lepida; the origin of these individuals is unknown. Two other individuals resembling C. lepida but with haplotypes of mtDNA referable to C. venusta were found in the Frio River and presumably represent relatively recent hybrids. Results of our study indicate that C. lepida, C. sp. cf lepida, and D. serena in the upper Nueces River basin, especially in the Sabinal River drainage, are at appreciable genetic risk.
We examine variation in ovarian traits over a 24-month period in Cyprinodon rubrofluviatilis, an inhabitant of highly variable stream environments in the southern Great Plains of western Texas and Oklahoma. The smallest females bearing clutches are ca. 20 mm in standard length. Ovarian traits indicate that maximum reproduction occurred from March into July, but some degree of reproduction was potentially possible throughout the year. Most ovaries had atretic oocytes as early as September when the gonadosomatic index and the percentage of females with clutches were declining, but a small proportion had mature eggs in all fall and winter months (0–2%, average 0.8%, October–January, across all years) except, possibly due to sampling error, in October. Detailed analysis of females from April and July indicate greater reproduction in 2002 than in 2003 and greater in spring than in mid-summer. There was marginal evidence from estimates of dry weight of oocytes that females invest more energy in individual offspring in spring than in mid-summer.
Ordination, correlation, and regression analyses were used to identify trophic and taxonomic distributional patterns of fishes in the Tilostoc River (located west of Valle de Bravo Lake in the Middle Balsas Basin, central Mexico) and associations of these patterns with environmental variables. Nonmetric multidimensional scaling analysis indicated that trophic and taxonomic assemblages corresponded similarly to measured environmental gradients, especially elevation and velocity of currents. We also compared the trophic structure of assemblages of fishes of the Tilostoc River to that of Terreros Creek, a temperate system of similar size and species richness but with a taxonomically different group of species. The two basins were significantly different, indicating strong historical constraint on trophic structure. Our trophic matrix for Tilostoc River was strongly correlated with the taxonomic matrix.
To elucidate feeding kinematics of the endangered Rio Grande silvery minnow (Hybognathus amarus), high-speed (500 frames/s) recordings of dorsal, lateral, and ventral feeding of larval silvery minnow were analyzed through National Institute of Health ImageJ software. Suction-feeding with buccal expansion was observed when feeding was apparent, and approach and feeding angle of H. amarus approaching the feeding substrate were calculated. Angles of approach averaged ca. 24–90°, while feeding angles were ca. 90°. Duration and touches, duration and bites, and touches and bites were correlated at 0.74, 0.62, and 0.54, respectively. Video analysis of feeding kinematics showed that H. amarus uses a combination of biting into the substrate followed by rapid lateral movement of the head. Hybognathus amarus has evolved a rapid-feeding mechanism in a turbid environment that allows for tasting and feeding sequences averaging 50–80 milliseconds.
We introduced 250 alligator snapping turtles (Macrochelys temminckii) originating from a turtle farm in Arkansas into six pools adjacent to the Washita River in Johnston, Bryan, and Marshall counties, Oklahoma. Additionally, we released 16 captive-bred and reared juvenile turtles. We used radiotelemetry and mark-recapture to monitor dispersal of turtles, selection of microhabitat, and patterns of movement. We placed transmitters on 16 adult turtles from Arkansas and 16 captive-bred juveniles 2–4 years old. We recorded 198 locations of 32 individuals by radiotelemetry between May 2007 and August 2008. We recaptured 45 turtles one-five times using hoop nets employed for 501 trap-nights. We compared movement and selection of habitat between sexes and age classes for the parameters water depth, bottom temperature, turbidity, and canopy cover. Adults and juveniles chose shallower depths with more canopy than available randomly. Additionally, adults chose greater depths than did juveniles, and juveniles chose areas with more canopy than did adults. There was no difference in selection of habitat between sexes. Adults utilized a larger linear home range than did juveniles.
To assess the genetic diversity and phylogeography of the blunt-nosed leopard lizard (Gambelia sila), we sequenced 1,285 base pairs (bp) of the mitochondrial cytochrome oxidase-b (cyt-b, 682 bp) and cytochrome oxidase III (CO3, 603 bp) genes from 33 individuals representing eight natural populations in central California. Phylogenetic analysis indicated that 17 observed haplotypes are partitioned into two major clades, which correspond geographically to where the lizards were collected. We also conducted a focused analysis of individuals collected from the canyons leading into the Cuyama Valley in Ventura and Santa Barbara counties, a geographic area with lizards possibly representing a remnant hybrid (with G. wislizenii) population. All lizards from the Cuyama Valley and adjacent canyons exhibited the mitochondrial haplotype of G. sila and were embedded within one clade. Our morphological analysis placed some leopard lizards collected from Cuyama Valley with true G. sila, whereas some individuals aggregated with G. wislizenii. This finding suggests that the quantitative morphological characteristics often used to distinguish between the two species are fairly labile and may be influenced by prevailing environmental conditions.
We identify Matthiola parviflora, native to the Mediterranean, as a newly discovered exotic plant in the Sonoran Desert in southwestern United States. We used morphological and molecular characteristics to distinguish M. parviflora from its naturalized congener Matthiola longipetala. Comparison with Internal Transcribed Spacer sequences from GenBank confirmed identification as M. parviflora. To predict the potential for broad-scale invasion, we used repeated censuses and maximum-entropy modeling with MaxEnt software. Censuses from 2008–2010 documented localized spread through an undisturbed biological reserve, and the modeling predicted a large area of suitable habitat in southwestern United States and northern Mexico. This record represents the first reported occurrence of M. parviflora in the Western Hemisphere and characterizes the species as well established near Tucson, Arizona, with a significant potential for spread.
We investigated the effects of soil temperature and depth to ground water on first-year growth of a facultative floodplain phreatophyte, Glycyrrhiza lepidota, in a 2-×-2 factorial greenhouse experiment. We grew plants in mesocosms subirrigated with water low in dissolved oxygen, mimicking natural systems, and set depth of ground water at 63 or 100 cm and soil temperature at cold (ambient) or warm (≤2.7°C above ambient). We hypothesized the moister (63 cm) and warmer soil would be most favorable and predicted faster growth of shoots and roots and greater nitrogen-fixation (thus, less uptake of mineral nitrogen) under those conditions. Growth in height was significantly faster in the moister treatment but was not affected by soil temperature. Final biomass of shoots and of roots, total biomass of plants, and root:shoot ratio indicated a significant effect only from depth of ground water. Final levels of soil mineral-nitrogen were as predicted, with level of nitrate in the moister treatment more than twice that in the drier treatment. No effect from soil temperature on level of soil-mineral nitrogen was detected. Our results suggest that establishment of G. lepidota requires strict conditions of soil moisture, which may explain the patchy distribution of the species along southwestern dryland rivers.
To determine if ecological restoration is a feasible practice that can accelerate the recovery of biodiversity and ecological processes, we evaluated the reestablishment of the lepidopteran larval community and rates of herbivory in a site in secondary succession and a restored site in the Chamela-Cuixmala Region, Mexico. Species richness and abundance of lepidopterans were similar at both sites; however, there was a strong difference in composition of species. Only 27% of species were shared between sites; however, Simpson's diversity indices were not different between sites. Rates of herbivory and percentage of consumption of leaves by herbivores in two species of trees, Apoplanesia paniculata (Leguminosae) and Heliocarpus pallidus (Tiliaceae), were equivalent between sites. Restoration of tropical dry forests appears to be feasible, and this practice is helping to reestablish the lepidopteran larval community associated with the vegetation and, more importantly, also is reestablishing the ecological process of herbivory.
We characterized nest-sites of the southern flying squirrel (Glaucomys volans) in a pine-oak forest located in Hidalgo, Mexico, and compared habitat variables between plots with nests and random plots without observed nests. We also compared areas of mature forest with forested areas under management. We detected 31 leaf nests or dreys along two streams in mature forest and none in forest under management; 93.6% of dreys were constructed on branches of live oaks (Quercus laurina). Plots with nests had significantly more snags, more rocks, and steeper slopes than plots without observed nests. No difference was found in the number of trees. In plots with nests, oaks were the dominant trees, mainly Q. laurina, while pines (Pinus) were more abundant in plots without observed nests. Given the propensity for these squirrels to build leaf-nests, availability of snags and cavities in this region may not be a limiting factor for G. volans as has been suggested previously.
Phylogenetic relationships of the Mexican endemic and endangered Nelson's woodrat, Neotoma nelsoni (Rodentia: Cricetidae), were examined using three mitochondrial genes (cytochrome-b, 12S ribosomal RNA, and 16S ribosomal RNA) for a total of 2,140 base pairs. Gene-sequences were analyzed using maximum likelihood and Bayesian models of phylogenetic inference. Independent analyses of the three gene-sequences converged on essentially identical gene trees, all showing N. nelsoni to be a sister lineage to N. leucodon from Durango, Mexico. Given the relatively low level of divergence of sequence of cytochrome-b between N. nelsoni and N. leucodon (3.3% using the Kimura two-parameter model, which is less than variation within N. leucodon) and the current absence of reliable diagnostic morphological characters to distinguish N. nelsoni from N. leucodon, N. nelsoni is recognized as a subspecies of N. leucodon. Based on molecular estimates of times of divergence, phyletic diversification in the species-group N. micropus (which includes N. leucodon nelsoni) began near the Middle Pleistocene and N. leucodon nelsoni diverged from other Mexican populations of N. leucodon during the Late Pleistocene. The repeated Pleistocenic cycles together with the final periods of volcanic activity in the eastern part of the Trans-Mexico Volcanic Belt may have played a major role in early differentiation in this lineage.
Changes over one grazing season and data from a 5-year study were used to evaluate the impact of cattle-grazing on the structure and composition of plants in steppe riparian areas. For one growing season, comparison of areas exposed to grazing and areas released from grazing indicated that the areas exposed to grazing had a significantly different structure, less aboveground biomass, and greater heterogeneity in soil nutrients than did nongrazed areas. The 5-year study showed that compositions of species between grazed and nongrazed areas were different at the onset. Over time, additional variations in diversity and composition of species between the grazed and nongrazed areas occurred but did not change significantly. This suggested that environmental factors were affecting these areas more than grazing. Impacts on steppe riparian vegetation were minimal at the intensities of grazing investigated.
Data on density, percentage of cover, and species richness were collected for grasses occurring in xeroriparian (desert riparian) areas across the Barry M. Goldwater Range, Arizona, to understand how native grasses occurring in isolated xeroriparian areas are related to use by wildlife, exotic invasive plants, and the surrounding floral community. These data were analyzed for significant associations with two aspects of landscape: adjoining matrix community of plants; distance from water-developments for wildlife (as a proxy for long-term use by wildlife). The adjoining matrix community, either Creosote-Bursage Desert Scrub or Palo Verde-Mixed Cacti-Mixed Scrub on Bajadas, had a significant influence on communities of native and exotic grasses in xeroriparian habitats, suggesting that observed characteristics of these communities can be predicted in the Sonoran Desert when large-scale distribution of floral communities are known. Increasing cover of exotic plants was associated with decreasing native richness. Distance to water-developments for wildlife had no significant relationship, suggesting that use associated with this water was not a significant driver of communities of grass.
We describe surplus-killing of endangered giant kangaroo rats (Dipodomys ingens) by endangered San Joaquin kit foxes (Vulpes macrotis mutica) and consider the conditions that may have promoted such killing. We also use results of extensive mark-recapture surveys of rodents to document a decline in local density of the giant kangaroo rat that was likely caused by surplus-killing.
We examined the reproductive status of Baird's pocket gophers (Geomys breviceps) in Union Parish, Louisiana, for 18 months in 2010 and 2011. We found that pocket gophers were potentially reproductively active throughout the year, although the number of reproductively active gophers peaked during late spring through autumn. Our results are similar to those of studies of Baird's pocket gopher in other states and of other pocket gophers in the genus Geomys.
To evaluate use of habitat by northern leatherside (Lepidomeda copei), intermittent reaches of streams adjacent to streams containing northern leatherside were electrofished. Northern leatherside were collected from two of five intermittent streams sampled in southwestern Wyoming. The opportunistic use of seasonally available habitats by northern leatherside might be reflective of spawning movements and is consistent with its evolutionary history.
A test of a general growth-model to estimate the age of Carnegiea gigantea, a keystone species of the Sonoran Desert, was conducted. Results suggest that standard errors are low (<2 years) and the model is robust for estimating age of establishment of the long-lived saguaro cactus.
We planted 308 star cacti (Astrophytum asterias) in southern Texas on private ranches where existing populations were reduced or destroyed. Overall mortality was 48% with herbivory accounting for 34% of the mortality (50 of 148). Mortality varied among planting sites but was not influenced by initial size, even when cacti killed by herbivory were excluded. Mortality was highest during times with low precipitation or high temperatures. Surviving cacti on two sites increased in average size. Reintroduction through planting is a viable strategy for restoring populations of star cacti.
Copepods of the genus Salmincola (gill lice) parasitize salmonids. We collected kokanee salmon (Oncorhynchus nerka) from a reservoir in Colorado to identify the species of gill lice present and investigate intensity and prevalence of infestations. We observed increasing intensity and prevalence with age of fish. Our study adds to limited knowledge of infestations of Salmincola in Colorado and the western United States.
Four nematodes Physaloptera rara (11/31, 35.5%), Physaloptera (5/31, 16.0%), Toxascaris leonina (1/31, 3.2%), and Toxocara canis (17/31, 54.8%) and two cestodes Dipylidium caninum (11/31, 35.5%) and Mesocestoides variabilis (9/31, 29.0%) were recovered from 23 of 31 (74%) swift foxes, Vulpes velox, for the first time from New Mexico.
We evaluated the influence of sex and environmental temperature on thermoregulation by Aspidoscelis calidipes from Apatzingán, Mexico. Range of body temperature was 32.6–44.6°C with a mean (±1 SD) of 40.44 ± 2.55°C, which is one of the highest recorded for the genus Aspidoscelis. Body temperature did not vary as a function of sex and was strongly associated with environmental temperature (temperature of air and substrate) which may be due to territoriality.
We found two nests of the long-eared owl (Asio otus) in Reserva Ecológica el Uno, located in Janos municipality, Chihuahua, Mexico. Contents of nests were recorded, photographed, and monitored between 28 March and 10 June 2007. Nests were constructed on honey mesquites (Prosopis glandulosa) and contained three eggs and three nestlings, respectively. These nests represent the first confirmed breeding record for the state of Chihuahua and the second for Mexico (outside Baja California).
We report the persistence of Craugastor palenque and expansion of its distribution in Chiapas, Mexico. Previous records of this species were only from the type series. We report records from another locality south of the type locality. These new records confirm the presence of the species, which had not been collected since the 1970s.
We used automatic game-cameras to document the consumption of desert gourds (Cucurbita foetidissima) by collared peccary (Pecari tajacu) during 2009–2011 at a wildlife feeding station near Alpine, Texas. Our observations constitute the first report of the fruit of C. foetidissima in the diet of collared peccary. Seeds probably escape damage during mastication and chemical digestion owing to their small size, and we, therefore, consider collared peccary to be potential dispersal agents of C. foetidissima. Although extinct megafauna (e.g., probiscideans, equids, and Geochelone) also may have dispersed seeds of C. foetidissima, the contention that its fruit is an ecological anachronism warrants reconsideration.
We review the known records of desert shrews from Nevada and report the results of genetic analyses of a specimen from Ash Meadows National Wildlife Refuge, Nye County, Nevada, which help clarify the evolutionary relationships of the genus Notiosorex from southwestern United States.
We describe an encounter of eight territorial California towhees (Melozone crissalis), alternately engaged in mobbing a western scrub-jay (Aphelocoma californica) and vigorous conspecific attack and display. We additionally characterize a previously unreported crouching posture adopted by the towhees while surrounding the scrub-jay and hypothesize that this posture communicates submissiveness to conspecific owners of a territory. We suggest that this behavioral sequence resulted from a conflict between cooperation among pairs and defense of resources among pairs, wherein behaviors consistent with both were exhibited nearly simultaneously.