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Astrophytum asterias is an endangered cactus occurring in southern Texas and northeastern Mexico. The purpose of this study was to provide fundamental information about the reproductive biology of the species. Breeding-system experiments were conducted in Starr County, Texas. Pollination treatments were applied to explore whether the species is self-compatible or self-incompatible and whether plants are experiencing pollinator limitation. Treated (bagged) flowers were self-pollinated or outcrossed by hand, or allowed to naturally self-pollinate. Control flowers were unbagged and unmanipulated (open-pollinated). In each treatment and controls, we calculated mean fruit set and mean seed set per plant. Controls had 18.3% fruit set, with a mean seed set of 13.3 ± 14.7 seeds. The outcross treatment resulted in 88.6% fruit set, with a mean seed set of 95.8 ± 5.9 seeds. Median mean fruit and seed set in the outcross treatment were 1 and 92.7, respectively. Although some controls set fruit and seed, median mean fruit and seed set was 0. No fruit or seed was set in self-pollinated treatments. These results showed that the species is an obligate outcrosser. Reproductive success is, therefore, dependent on a vector to transfer pollen. The fact that fruit set and seed set were higher in hand-outcrossed flowers than in open-pollinated flowers suggests that A. asterias might be experiencing reproductive constraints in terms of availability or effectiveness of pollinators.
With global warming, flowering at many locations has shifted toward earlier dates of bloom. A steady increase in average annual temperature since the late 1890s makes it likely that flowering also has advanced in the northern Sonoran Desert of the southwestern United States and northwestern Mexico. In this study, phenological models were used to predict annual date of spring bloom in the northern Sonoran Desert from 1894 to 2004; then, herbarium specimens were assessed for objective evidence of the predicted shift in flowering time. The phenological models were derived from known flowering requirements (triggers and heat sums) of Sonoran Desert shrubs. According to the models, flowering might have advanced by 20–41 d from 1894 to 2004. Analysis of herbarium specimens collected during the 20th century supported the model predictions. Over time, there was a significant increase in the proportion of shrub specimens collected in flower in March and a significant decrease in the proportion collected in May. Thus, the flowering curve – the proportion of individuals in flower in each spring month – shifted toward the start of the calendar year between 1900 and 1999. This shift could not be explained by collection activity: collectors showed no tendency to be active earlier in the year as time went on, nor did activity toward the end of spring decline in recent decades. Earlier bloom eventually could have substantial impacts on plant and animal communities in the Sonoran Desert, especially on migratory hummingbirds and population dynamics of shrubs.
Reforestation of degraded lands in the tropics is one of the most important goals of ecological restoration. Restoration of montane wet forest is in progress at Hakalau Forest National Wildlife Refuge, Hawaii, using plantations of Acacia koa (koa), a canopy tree of montane wet forest. We used longhorned beetles (Plagithmysus claviger and P. varians) as indicator species to assess restoration. The beetles feed by boring into dead koa branches and are food for the endemic forest bird Hemignathus munroi. We quantified density of beetles in branches of koa from trees of 3 age categories: young plantations (3–8 y; 222 branches), older plantations (12–15 y; 212 branches), and canopy trees of intact forest (167 branches). We sampled by breaking dead branches into short pieces and counting the beetles within. Density of beetles was greater in canopy trees (4.89 beetles/branch) than in planted trees and was greater in older plantations (3.24 beetles/branch) than in younger plantations (0.90 beetles/branch). Beetles were clumped in distribution among branches (coefficient of dispersion = 5.17). Mean basal diameter of branches in canopy trees (32.6 mm) was greater than in planted trees and was greater in older plantations (29.3 mm) than in young plantations (19.0 mm). In young and older plantations, branches that harbored beetles were larger than branches that did not, but in canopy trees there was no difference. Branch diameter had a positive effect on number of beetles per branch in all age categories. Koa plantations promote recovery of plant and animal biological diversity in degraded habitats formerly occupied by montane wet forest.
Elevation has strong effects on climate and biota. In Hawaii, elevation on volcanic mountains affects temperature, rainfall, vegetation, and fauna. The effect of elevation on animal distribution and abundance can be direct through effects on climate or, in the case of phytophagous insects, indirectly mediated through climatic effects on host plants. In montane wet forests dominated by Metrosideros polymorpha (ohia lehua) and Acacia koa (koa), longhorned wood-boring beetles (Cerambycidae, Plagithmysus) play an important role as decomposers of wood and as food for higher trophic levels. The beetles I studied feed exclusively on dead wood of koa. I assessed the effect of elevation on the density of longhorned beetles in plantations of koa at Hakalau Forest National Wildlife Refuge, Hawaii. Density per branch of longhorned beetles was more than twice as great in the low-elevation sample (1,620–1,650 m; 3.49 beetles/branch, n = 200) as in the high-elevation sample (1,880–1,970 m; 1.61 beetles/branch, n = 200; t = 5.08, P < 0.001). Beetles were contagiously distributed among branches at both low and high elevations (CD = 5.71). Size of branch had a consistent positive effect on density of beetles, although this effect was more pronounced at low elevation. Elevation affects biological diversity directly through climate and seasonality, and indirectly through climatic effects on key habitat features. Effects of seasonality and habitat features on longhorned beetles need further study in Hawaiian montane forest.
Archocentrus myrnae is a small Central American cichlid that breeds in crevices. This study describes reproductive behavior and associated changes in color patterns in this species. Unlike most other cichlids from that area, female A. myrnae establish territories and actively court males before spawning. During courtship, females exhibit a distinct coloration. Whereas presence of courtship by females and the reversed sexual dimorphism usually is connected to reversal of sex roles in other fishes, females of A. myrnae intensively care for their brood after spawning through the free-swimming stage. Males are less active during brood care. In the context of the high reproductive investment of females, the evolution and maintenance of courtship and ornamentation of females is not yet understood.
The Devils River minnow (Dionda diaboli) coexists with at least 2 congeners and several other cyprinids throughout its range in southern Texas and northern Mexico. Larval and juvenile descriptions are needed to monitor D. diaboli larvae and juveniles as part of recovery efforts for this species of conservation concern. The purpose of this study was to describe and quantify characteristics of early life stages of D. diaboli from hatching to 128 d post hatch to facilitate larval and juvenile identification. Descriptive characters include mid-lateral band of melanophores by Day 8 (>5.1 mm SL; >5.4 mm TL), mid-lateral band of melanophores separate from a rounded caudal spot and lateral snout-to-eye melanophores by Day 16 (>5.8 mm SL; >6.3 mm TL), initial coiling of intestine by Day 32 (>6.2 mm SL; >7.2 mm TL), wedge-shaped caudal spot by Day 64 (>8.7 mm SL; >10.0 mm TL), and melanophores around scale margins and mid-lateral double dashes along lateral line by Day 128 (>13.5 mm SL; >16.0 mm TL). However, reliable separation among sympatric Dionda might not be possible until larvae and juveniles of congeners are described.
Sex ratios are difficult to determine for anurans with short, seasonal breeding cycles. However, it is important to obtain accurate sex-ratio estimates of the reproductively mature individuals within a population, because a naturally biased sex ratio decreases effective population size. A population of Houston toads (Bufo houstonensis) was used as a model to examine sex ratios for an anuran with short breeding cycles. During March 2001–August 2004, 157 B. houstonensis were captured by drift fence-pitfall traps and breeding-pond surveys. A significantly male-biased sex ratio was evident for both capture methods, indicating a naturally occurring bias within the population. A mathematical simulation model tested the hypothesis that the bias could be a consequence of different ages at first reproduction. Results from the simulations indicated populations of adult Houston toads are likely male-biased because of the difference in age at first reproduction.
As part of a recent project on the distribution and status of primates (Ateles geoffroyi and Alouatta palliata) in the tropical forests of northeastern Oaxaca, Mexico, we report the presence of spider monkeys (A. geoffroyi vellerosus) in a tropical dry forest south of the Isthmus of Tehuantepec, Oaxaca, Mexico. During March and May 2003, we documented the presence of spider monkeys at 5 sites (2 direct observations and 3 indirect records based on vocalizations, presence of feces, and a carcass). The presence of spider monkeys in a landscape dominated by tropical dry forest suggests that this species has an ability to inhabit a broad range of tropical forest types. Two factors threatening the continued presence of monkeys at these sites are increasing forest destruction as a result of highway construction, and hunting and capture for the pet trade.
The current (1996–1997 survey) mammalian fauna of the Cuatro Ciénegas Basin, Coahuila, Mexico, is compared with records of the past century as well as records from undated (pre-1953) owl-pellet records and undated (pre-1700) archaeological remains. The basin supports one of the largest freshwater areas in the deserts of northern Mexico and is located along the Sierra del Carmen–Sierra Madre Oriental Filter-Barrier, between the arid Chihuahuan and tropical Tamaulipan biotic provinces. The freshwater environment has remained remarkably stable through Pleistocene climatic oscillations, but more recently has been subjected to human-induced impact. Comparison of archaeological, historical, and current mammalian fauna depicts the well-known extirpation of larger carnivores and ungulates by humans; the shift to a drier, more Chihuahuan environment; and loss of species during the past century, including the apparent and unexplained disappearance of 4 species of rodents from the basin.
Examination of cytochrome-b DNA sequences from specimens of Notiosorex crawfordi, the desert shrew, indicate that within this taxon there are at least 3 major subdivisions reflecting levels of variation more typical of species rather than subspecies. One of these cytochrome-b haplotypes was recently described as a previously unrecognized species; however, that paper was limited to the description of a species level name. We provide additional insight into subdivisions in N. crawfordi. One DNA haplotype is distributed in Texas, New Mexico, and eastern Arizona, a second haplotype in Arizona and Sonora, Mexico, and the third haplotype in Baja California, Mexico. Nucleotide sequences obtained from intron 7 of the nuclear gene, beta fibrinogen, support the conclusions that 2 of the haplotypes occur sympatrically in southeastern Arizona and are not hybridizing with each other.
Mining has been cited as detrimental to bighorn sheep (Ovis canadensis), but little research exists that has demonstrated those effects. We compared behavior of bighorn sheep while individuals were inside and outside of an active copper mine to determine if individual animals were altering their behavior relative to the active mine. We conducted this study in the Silver Bell Mountains, Arizona, from December 2003 to January 2005. We observed 3 radiocollared subadult males, 4 adult males, and 5 females, and recorded behavior throughout the daylight period. After accounting for differences by sex-age class (i.e., subadult male, adult male, female) and season (i.e., breeding, non-breeding), bighorn sheep fed less (6%) while inside the mine perimeter. Other behaviors (e.g., bedding, standing, alert, and interacting) were observed for similar amounts of time while within and outside the mine perimeter. Within sex-age classes, there were few differences in behavior. Subadult males fed less (mean difference = −18.6%, 95% C.I. = −43.1–6.0) and bedded more (mean difference = 14.3%, 95% C.I. = −40.9–69.4) while inside the mine. During the breeding season, adult males were alert less and interacted less (alert, mean difference = 4.1%, 95% C.I. = −1.63–9.9; interacting, mean difference = 3.1%, 95% C.I. = −5.7–11.9) while inside the mine. Females interacted more (mean difference = 0.37%; 95% C.I. = −0.01–0.8) while inside the mine area. Elements of modern mining activity (e.g., vehicular traffic, humans afoot near vehicles, sounds) might be predictable to bighorn sheep allowing them to habituate to those human activities.
We documented range expansion of the Asiatic clam, Corbicula fluminea, in Colorado since its first occurrence in 1993 in the South Platte River drainage. Using recent surveys and literature records, we compiled known occurrences of the Asiatic clam over the past 12 y and determined that it has expanded beyond the initial confines of the Platte River and Arkansas River drainages into the Colorado River and San Juan River drainages. All previously reported occurrences are still extant and the species continues to spread to new localities, especially in the Arkansas River drainage. We speculate on potential negative impacts to native freshwater mussels in Colorado, but have not conducted any definitive studies.
Samples of 8 natural populations of Drosophila pseudoobscura inhabiting northern Mexico were cytogenetically analyzed. Twelve distinct chromosomal arrangements of the third chromosome were identified. Number of inversions at each locality varied from 6 to 8. A total of 468 third chromosomes were examined in the area of study, and relative frequencies of inversions in each population were calculated. The most common inversions in decreasing order of relative frequency were: TL, SC, OL, and CU; the other 8 inversions had frequencies <10%. Each locality had 3–4 inversions that accounted for ≤80% of the total. All populations were heterogeneous. Relative frequency of each inversion did not form a gradient along the transect studied. Unexpected was the presence of the ST inversion, as well as the incidence, in some populations, at a moderate frequency, of the inversion OL. Another exception was the increase in frequency of the EP inversion compared with previous collections in the area. More information from the region is needed.
Only one species, Sceloporus variabilis, previously has been recorded in the diet of Cerrophidion tzotzilorum. Here I report 2 new prey items for this little known species of montane pitviper. I examined stomach contents from a juvenile C. tzotzilorum and found a skink (Sphenomorphus incertus) and an orthopteran in the family Acrididae. These prey species are similar to those eaten by other species of Cerrophidion.
In the Lower Rio Grande Valley of South Texas, Audubon's orioles (Icterus graduacauda) have declined substantially in the past 50 y, probably due to habitat loss, fragmentation, and brood parasitism by bronzed cowbirds (Molothrus aeneus). Tape playback of the song of Audubon's oriole, originally intended to better survey the oriole, also attracted bronzed cowbirds. Bronzed cowbirds flew silently into the nearest tree in 14.1% of 234 playbacks, whereas Audubon's orioles responded vocally or flew toward the recorder in 15.8% of playbacks. Bronzed cowbirds might use vocalizations of Audubon's oriole as a cue to find breeding pairs or nests of this secretive species, which usually forages and sings within dense foliage.
We collected owl pellets from 4 counties to examine the distribution of prairie voles (Microtus ochrogaster) and other small mammals in the Texas Panhandle. We identified 797 individuals of 15 genera and species of small mammals from 207 owl pellets. Overall, the 5 most abundant small mammals, Peromyscus (331 individuals), Reithrodontomys (182 individuals), Cryptotis parva (74 individuals), Sigmodon hispidus, and M. ochrogaster (60 individuals), comprised 89% of all individuals identified. This study extends the known range of M. ochrogaster 24 km south and 13 km east of the previous record in Carson County, Texas, and provides new county records of M. ochrogaster in Armstrong and Ochiltree counties. Additionally, we identified C. parva in samples from Ochiltree and Carson counties and Notiosorex crawfordi in samples from Armstrong County, both of which represent new county records. Our results, along with other recent work on M. ochrogaster, suggest that this species is more widespread in the northern and central Texas Panhandle than previously reported. More work is necessary to determine the southern limit of this species in the Texas Panhandle.