Explore the vast range of titles available.

The Gray Vireo (Vireo vicinior) is a scarcely studied species of the arid mountains of the southwestern U.S. and northern Mexico, especially in the eastern part of its known range. Between May–August 2013, we located 10 nests of the Gray Vireo at the eastern canyons of the Sierra La Paila, Coahuila, Mexico; approximately 300 km SE from the closest known breeding population in Sierra Maderas del Carmen. Gray oaks (Quercus grisea) were the main nesting plant, followed by shrubby bullseyes (Nahuatlea hypoleuca). We recorded three new nesting plant species for the Gray Vireo. Six of the eight monitored nests were successful and two were abandoned due to Brown-headed Cowbird (Molothus ater) brood parasitism. This new population stands out as the southernmost, extends the breeding range of the Gray Vireo to the southeast of Coahuila, and raises questions about their potentially distinctive seasonal status, breeding ecology, and habitat use. The discovery of this breeding range extension implies the existence of more undiscovered reproductive populations throughout arid mountains of the northern Sierra Madre Oriental. El vireo gris (Vireo vicinior) es una especie poco estudiada de las montañas áridas del suroeste de Estados Unidos y el norte de México, especialmente en la parte oriental de su área de distribución conocida. Entre mayo–agosto de 2013 localizamos 10 nidos del vireo gris en los cañones orientales de la Sierra La Paila, Coahuila, México; aproximadamente 300 km al SE de la población reproductora conocida más cercana en Sierra Maderas del Carmen. Los encinos grises (Quercus grisea) fueron la principal planta usada para la anidación, seguidos por chomonques (Nahuatlea hypoleuca). Se registraron tres nuevas especies de plantas para anidación de vireo gris. Seis de los ocho nidos monitoreados tuvieron éxito y dos fueron abandonados debido al parasitismo de nido del tordo cabeza café (Molothus ater). Esta nueva población destaca como la más austral, amplía el área de reproducción del vireo gris hacia el sureste de Coahuila y plantea preguntas sobre su estatus migratorio o residente potencialmente distintivo, su ecología reproductiva y el uso de su hábitat. El descubrimiento de esta extensión del rango reproductivo implica la existencia de más poblaciones reproductivas no descubiertas en las sierras áridas del norte de la Sierra Madre Oriental. PALABRAS CLAVE chomonque; Coahuila; distribución reproductiva propuesta; encino gris; nueva población reproductiva; nuevas plantas para anidación; Sierra La Paila

The use of unmanned aerial vehicles (UAV) for forest monitoring has grown significantly in recent years, providing information with high spatial resolution and temporal versatility. UAV with multispectral sensors allow the use of indexes such as the normalized difference vegetation index (NDVI), which determines the vigor, physiological stress and photosynthetic activity of vegetation. This study aimed to analyze the spectral responses and variations of NDVI in tree crowns, as well as their correlation with climatic factors over the course of one year. The study area encompassed a 1.6-ha site in Durango, Mexico, where Pinus cembroides , Pinus engelmannii , and Quercus grisea coexist. Multispectral images were acquired with UAV and information on meteorological variables was obtained from NASA/POWER database. An ANOVA explored possible differences in NDVI among the three species. Pearson correlation was performed to identify the linear relationship between NDVI and meteorological variables. Significant differences in NDVI values were found at the genus level ( Pinus and Quercus ), possibly related to the physiological features of the species and their phenology. Quercus grisea had the lowest NDVI values throughout the year which may be attributed to its sensitivity to relative humidity and temperatures. Although the use of UAV with a multispectral sensor for NDVI monitoring allowed genera differentiation, in more complex forest analyses hyperspectral and LiDAR sensors should be integrated, as well other vegetation indexes be considered.

Patterns of reproductive isolation between two sympatric species of oaks, Quercus gambelii and Q. grisea , that exhibit strong ecological differentiation were examined. A full diallel cross using four trees of each species (i.e. all possible pollinations among eight trees) was performed. This design was repeated at two sites that represent different outcomes of sympatry: (1) a xeric mountain ridge where many hybrids are established (HZ); and (2) a mesic valley bottom where virtually no hybrids are established (MOCYN). By measuring fruit survival at several developmental stages, both the timing and strength of reproductive barriers within and between sites, species, cross types, and pollen dosage levels were examined. In three of four cases, heterospecific fruit set was significantly reduced compared to conspecific fruit set. This reduction occurred after the time of fertilization, but before the onset of embryo growth. Increasing the dose of pollen from an average of 9–194 grains/stigma did not affect this result. Thus, early postfertilization processes play a strong role in species fidelity in these oaks. Quercus gambelii experienced a five-fold decrease in conspecific fruit set at HZ relative to MOCYN. In contrast, heterospecific fruit set of Q. gambelii was the same at both sites. Poor Q. gambelii pollen performance is implicated as playing the major role in this result. One Q. gambelii individual at HZ was highly fecund, and had higher heterospecific than conspecific fruit set; slight introgression in this tree was detected uisng RAPD markers. The Environmental Emasculation Hypothesis that posits that environmental stress can increase the probability of hybrid formation by reducing the competitive ability of male gametes of one species is proposed.

Symptoms of wood boring activity and Cerambycidae larvae in living oak trees (Quercus L. spp.) were discovered in October 2006 in the Sierra Fria, Aguascalientes, Mexico. Prompted by this finding, we conducted a field study to determine the wood borer species and its host preference and geographical distribution, and to record biological and ecological data. Adult specimens were obtained by caging infested bole samples in laboratory conditions as well as by installing screen emergence cages on infested trees in several locations in the Sierra Fria. Twenty-nine line transects were sampled in search of wood boring symptoms in living oak trees. Forty adult specimens were obtained during the 32-month study. Based on morphology and behavior, the insect was identified as Crioprosopus magnificus LeConte (Coleoptera: Cerambycidae), a new geographical record for this species. The main host for this insect is Quercus potosina Trel., but it also occasionally attacks Quercus grisea Liemb. and Quercus eduardii Trel. Wood boring symptoms attributed to C. magnificus were found along the Sierra Fria. Beetle emergence was confirmed in four locations. Observations on insect mating, longevity and oviposition are provided.

The white oaks Quercus gambelii and Q. grisea overlap in distribution in New Mexico and Arizona. Within the region of overlap, there are numerous instances of contact between the two taxa. In some areas of contact morphologically, intermediate trees are common, whereas in others, morphologically intermediate trees are rare or absent. We describe a set of RAPD markers that distinguish between the two species and use these markers to examine patterns of gene exchange in an area of contact in the San Mateo Mountains of New Mexico. The markers are highly coincident with morphology and confirm that hybridization between the two species takes place. Despite the occurrence of hybrids, both species remain distinct, even in areas of sympatry, and marker exchange appears to be limited.

The hybridization of plants can have significant consequences for the structure of consumer communities, and hybridization effects on plant defenses have been suggested to affect the distribution of consumers within hybrid zones. It is currently unknown how hybridization may affect ontogenetic patterns of phenolic biosynthesis. We describe the seasonal variation of absolute and relative concentrations of 18 individual phenolics, total proanthocyanidins, and nitrogen in theQuercus \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $grisea\\times Quercus$ \\end{document} gambeliihybrid complex in central New Mexico. Expression patterns of individual compounds were most often equal between hybrid and parental taxonomic categories; nonequal patterns of expression were most often dominant (equal to one parent) towardQ. gambelii. These patterns of phenolic expression contrast with the more common additive patterns reported in hybrid zones of other tree species.Quercus griseabackcrosses displayed significant developmental instability in phenolic biosynthesis relative to other hybrid oaks. Importantly, the composition and structure of phenolic phenotypes were found to vary seasonally. Throughout the growing season, the majority (>93%) of variation between oak phenolic phenotypes was attributed to the relative concentrations of phenolics and nitrogen. The results of this study emphasize the importance of compound‐specific evaluations of hybrid plant defense metabolites and metabolic variation in hybrid zones. These considerations are critical for the further empirical study of potential hybridization effects on the complex, dynamic mixtures that make up plant defense chemistry.

Objectives were to determine number and height of sprouts and seedlings following clearcutting of a mesa dominated by pinyon pines (Pinus edulis) and alligator junipers (Juniperus deppeana) in southwestern New Mexico and to determine effects of prescribed burning for control of sprouts and seedlings. No stump of pinyon pine sprouted. Nearly 50% of stumps of alligator junipers sprouted with most occurring in plots with slash removed; the fewest and tallest sprouts occurred in plots with slash uniformly scattered following clearcutting. Nearly 25% of stumps of gray oaks (Quercus grisea) sprouted. Burning in the same year as clearcutting did not affect sprouting of gray oaks as much as other treatments. Not burning clearcuts and leaving slash scattered resulted in the fewest sprouts, and shortest sprouts of gray oaks occurred in plots with slash removed. Seedlings of pinyon pines, alligator junipers, and gray oaks were most prevalent in uncut control plots. Some seedlings of alligator junipers were in plots with slash scattered and removed, and few seedlings were in plots that were burned. Most seedlings of gray oaks were in uncut control plots and plots where slash was removed. Seedlings of pinyon pines grew tallest in plots with slash removed, seedlings of alligator junipers grew tallest in plots where slash was scattered, and seedlings of gray oaks grew tallest in all plots except the uncut control.

The historical and environmental forces involved in determining the geographic location of plant hybrid zones have long been of interest. Often hybrid zones appear to be intimately tied to the environment, yet because many abiotic factors covary it is often difficult to understand which are truly the most important in maintaining the position and structure of a hybrid zone. This study uses empirical data and modeling analyses to examine whether abiotic factors are responsible for the location and structure of an oak (Quercus) hybrid zone and, if so, which factors are the most important. Specifically, leaf trait measurements and ecological niche models were used to test the hypothesis that water availability plays a primary role in promoting and maintaining the location of hybridization between 2 species. Leaf trait analyses and ecological niche models both supported the hypothesis that water availability determines the location and structure of the hybrid zone. These findings lend support for the general importance of environmental factors in determining hybrid zone location and structure. Furthermore, they demonstrate how functional trait analyses and predictive ecological niche models can be used in future hybrid zone research.

We examined interactions between host plants, endophytic fungi, and leaf-mining moths (Phyllonorycter sp.) in an oak (Quercus grisea × Q. gambelii) hybrid zone. The community of endophytic fungi and two common endophyte species examined responded to host plant hybridization. Total fungal frequency (TFF) and frequency of Gnomonia cerastis were lowest on hosts resembling Q. grisea, and increased linearly towards those resembling Q. gambelii. In contrast, Coccochorella quercicola was most frequently isolated from Q. grisea-like hosts and decreased in frequency across hybrids towards Q. gambelii. Frequency of G. cerastis and TFF covaried with Phyllonorycter density across the hybrid zone, but direct effects of endophytes on Phyllonorycter density were not detected. Associations between endophytes and unexplained mortality of Phyllonorycter varied according to endophyte species and stage of Phyllonorycter development. In the sap-feeding stage, unexplained mortality was negatively associated with TFF and frequencies of Hormonema sp. and Preussia funiculata; whereas, in the tissue-feeding stage, unexplained Phyllonorycter mortality was positively associated with G. cerastis frequency. Three-way interactions between plant hybridization, endophytic fungi, and the insect herbivore were not significant.

The plant-hybrid-zones-as-centers-of-biodiversity (hereafter, PHZCB) hypothesis posits that plant hybrid zones represent areas of elevated biodiversity, and supports the inclusion of plant hybrid zones in conservation efforts. Support for the PHZCB hypothesis is limited to a handful of cases involving insect and fungal species and to two studies involving higher trophic levels. The PHZCB hypothesis requires further testing before plant hybrid zones can be established with any certainty as centers of biodiversity. We test whether the PHZCB hypothesis holds for higher trophic levels by examining the community structure of birds and reptiles associated with the Quercus grisea x Quercus gambelii species complex. Specifically, we compare patterns of species richness and abundance of these taxa in 10 hybrid zones and 11 contact zones (i.e., zones where both parental species occur but hybrids do not). In contrast to predictions of the PHZCB hypothesis, contact zones supported significantly more species of birds and reptiles than did hybrid zones. Species abundances exhibited idiosyncratic responses to zone type, but were higher generally in the contact zones.