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The Conservation Reserve Program (CRP) in the USA plays a major role in carbon (C) sequestration to help mitigate rising CO2 levels and climate change. The Southern High Plains (SHP) region contains > 900.000 ha enrolled in CRP, but a regionally specific C sequestration rate has not been studied, and identification of the C pools and processes important in controlling C sequestration rates remain unresolved. We aimed to address these gaps by utilizing a CRP chronosequence with historical rangeland as a reference ecosystem. Soil samples (0–10 and 10–30 cm) were collected in 2012 and 2014 from a total of 26 fields across seven counties within the SHP and included seven croplands (0 y in CRP), 16 CRP fields that ranged from 6 to 26 y (as of 2012), plus three rangelands. Multiple regression analysis was conducted to gauge the rate of C sequestration under CRP within C pools: soil organic C (SOC), particulate organic matter C (POM-C), and microbial biomass C (MBC), with two additional predictors (soil clay + silt content and precipitation). Despite attempts to control for soil texture by targeting a dominant soil series (Amarillo fine sandy loam), the percent of clay + silt (15.2–48.7%) significantly influenced C accrual. The C sources (C3 from previous cropping systems or C4 from CRP grasses) in SOC and POM-C were assessed using stable C isotope signatures. Additionally, the role of soil microbes in C sequestration was evaluated by investigating the relationship between MBC and CO2 flux and C sequestration. SOC increased at a rate of 69.82 and 132.87 kg C ha− 1 y− 1 and would take approximately 74 and 77 y to reach the rangeland C stocks at 0–10 and 0–30 cm, respectively. The C4‐C primarily from the introduced grasses was the main source of C sequestration. SOC gains were essentially due to increases in POM-C and MBC, accounting for 50.04 and 15.64% of SOC sequestration at 0–30 cm, respectively. The highest semi-partial correlation coefficients between the increasing years under CRP restoration and MBC indicated CRP had the strongest effect on MBC compared to other C pools. In addition, increasing soil CO2 flux and MBC:SOC ratio with years of CRP restoration indicated MBC played a critical role in the C sequestration process. Conservation of CRP lands and efforts to sustain perennial systems in this highly erodible landscape should be a high priority of conservation programs. In doing so, significant offsets to increasing atmospheric CO2 levels may be achieved in addition to erosion control and improved wildlife habitat.

The ecological mechanisms that sustain high species richness in Neotropical bat communities have attracted research attention for several decades. Although many ecologists have studied the feeding behavior and diets of Neotropical bats on the assumption that food is a limiting resource, other resource axes that might be important for species coexistence are often ignored. Diurnal refugia, in particular, are a crucial resource for bats, many of which exhibit conspicuous morphological or behavioral adaptations to the roost environment. Here we report and analyze information about roost occupancy based on >500 field observations of Amazonian bats. Statistical analyses of these data suggest the existence of distinct groups of species roosting (1) in foliage, (2) exposed on the trunks of standing trees, (3) in cavities in standing trees, (4) in or under fallen trees, (5) beneath undercut earth banks, and (6) in arboreal insect nests; additionally, we recognize other groups that roost (7) in animal bur...

Within the neotropical bat family Phyllostomidae, species of the subfamilies Glossophaginae and Lonchophyllinae have many derived traits adapted to nectarivory, including elongated snouts and jaws and the ability to perform hovering flight. We compared patterns of cranial variation within and between these groups with respect to within-group allometric trajectories, based on 19 linear morphometric variables collected from 221 specimens representing all genera and 62% of the species in the two subfamilies. In a pooled principal component analysis, species belonging to Lonchophyllinae and Glossophaginae occupy similar regions in morphospace, though the latter species have a greater variance. Principal components and common principal components analyses for separate taxonomic lineages (subfamilies, tribes and subtribes) revealed distinct static allometric trajectories among these groups, with variables associated with elongation of the rostrum having distinct allometric coefficients. Our results indicate that distinct cranial morphotypes associated with the degree of elongation of the rostrum in phyllostomid nectarivores are allometrically characteristic of each lineage. The patterns suggest that cranial integration in phyllostomid nectarivores reflects primarily their phylogenetic history rather than adaptive pressures resulting from specialization to particular feeding resources.

Aim To determine whether there is evidence of changes in small mammals distributions and emergent metacommunity structure in the Atlantic Forest resulting from extensive habitat loss and fragmentation associated with anthropogenic activities. Location South American Atlantic Forest from northeastern Brazil to eastern Paraguay. Methods Using presence–absence data for non-volant small mammals, we analysed metacommunity structure for communities from 76 fragments distributed throughout Atlantic Forest. We evaluated coherence, range turnover and range boundary clumping for the entire non-volant small mammal assemblage, marsupials, rodents and sigmodontine rodents separately. b-diversity based on the multiplicative model was used to estimate the number of compartments (groups of sites with similar species composition) in Clementsian structures, and cluster analysis identified which sites formed compartments. Canonical correspondence analysis determined which environmental factors were associated with the gradients along which metacommunities were structured. Distancedecay analysis evaluated the spatial structure in small mammal and environmental data, and Mantel tests evaluated correlations between them. Results Rodent metacommunities had Clementsian structure, whereas marsupials had Gleasonian structure. Compartment locations for rodents were consistent with areas of endemism. Temperature seasonality was most associated with the gradients along which metacommunities were structured. Assemblage and environmental dissimilarity among sites had significant positive relationships with geographic distance. Main conclusions Compartment locations in Clementsian structures mirrored historical refugium locations and important vicariance events associated with large rivers. Despite extensive deforestation in Atlantic Forest, small mammal distributions are consistent with expectations based on historical biogeography, suggesting that anthropogenic activities have not yet greatly affected geographic distributions of emergent metacommunity structures. However, extinction debt associated with recent fragmentation and habitat loss may exist. Any effective conservation plan for large and fragmented biomes must consider areas of endemism to maintain regional biodiversity and maintain sufficiently large and connected fragments to facilitate rescue effects and minimize effects of extinction debt.

Oligotrophic bacteria have been isolated from many habitats, yet environmental regulation of their distributions in soil has not been elucidated. To address the issue of environmental influence upon oligotrophic distributions, Chihuahuan Desert soils were sampled from five sites along an elevational and vegetational gradient within Big Bend National Park during January and August of 2002 and 2003. Soils were diluted and plated on oligotrophic media, and plates were incubated at 15, 25, 35, 45 and 60 °C. Additionally, measurements of soil organic matter, pH, moisture, extractable nitrate, extractable ammonium and microbial biomass carbon were collected for each sample to relate oligotrophic bacterial distributions to soil nutrient and edaphic characteristics. Analysis of variance indicated significant site, season, incubation-temperature and interaction effects on total oligotroph numbers. Canonical correspondence analysis and multiple regressions indicated that all soil-chemistry variables significantly influenced discrete morphologies of oligotrophs. Oligotroph distributions were most congruent with soil-chemistry variation in three sites, whereas oligotrophic diversity in two sites did not adhere closely to measured environmental variables. While vegetation type may structure oligotroph communities at the two mid-elevational sites, abiotic constraints are drivers in low-desert sites.

Understanding threats to endangered species is one of the most critical components of implementing a successful recovery plan. For the endangered star cactus Astrophytum asterias , both mammalian and insect herbivory have been documented as a major threat to populations in Mexico. Herein, we focus on populations of A. asterias in Texas, examining how mortality threats differ from populations found in Mexico as well as among sites within Texas. Our study supports insect and mammalian herbivory as a major threat to A. asterias in Texas, with reductions in population sizes ranging between 16 and 54%. However, our study highlights that both regional and local differences can influence rates of mortality even in a range-restricted species such as A. asterias and highlights the need to assess threats at both of these levels for effective development and implementation of endangered species recovery plans.

We employed a sliding-window approach at multiple scales (window sizes and dispersal distances) to calculate seven standard graph-theoretical metrics within a subset of a large, freshwater wetland network. In contrast to most graph analyses, which quantify connectivity at a single (global) scale or at a patch-level scale, a multi-scaled, sliding-window approach provides an assessment that bridges these two approaches to examine patch clusters. As a case study we focused on a subset of a habitat patch network in a ~20,000 km2 area encompassing 2,782 playa wetlands in the panhandle of Texas. Playas are seasonal wetlands of the southern Great Plains of North America that form a network of regional habitat resources for wildlife. The large size of this network meant that global metrics failed to capture localized properties, so we used contour mapping to visualize continuous surfaces as functions of playa density, linkage density, and other topological traits at different window sizes and dispersal distances. This technique revealed spatial patterns in the components (i.e., the network properties of regions of the landscape at a given dispersal scale), with the spatial scale of habitat clustering varying with the size of the sliding window and dispersal distance. Using a tool familiar to landscape ecology (sliding-window methodology) in a novel way (to examine ecological networks at multiple scales), our approach provides a way to represent ecologically determined local-scale graph properties and illustrates how a multi-scaled approach is useful in examining habitat connectivity to investigate graph properties.

Understanding the spatial distribution of phenotypes and their association with local environmental conditions can provide important insights into the evolutionary history and ecological dynamics of species. Geographical variation in the skull size of the Artibeus lituratus complex was explored to evaluate the association between morphological traits and habitat-specific environmental conditions in the mainland populations of Middle and South America. We performed a principal component analysis based on 390 museum specimens using 17 cranial and mandibular measurements to explore the overall morphometric variation in our sample. Additionally, we used the information from 19 bioclimatic variables from 127 collecting localities to assess the extent of variation in environmental space across our study area. A canonical correlation analysis performed to evaluate the association between morphological and environmental variables indicated a high correlation between morphology and environment. Seasonality was correlated with skull size (canonical r = 0.7). Specifically, skull size in the A. lituratus complex increases as the amount of precipitation during the driest season increases and as inter-annual precipitation variability decreases. This result supports the hypothesis that environmental pressures are at least partially responsible for the skull size differences observed. Moreover, the nonrandom distribution of individuals with different skull sizes suggests that environmental filtering plays a role in determining the geographical distribution of morphological variants. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 623–634.

Catch-and-release (CAR) fishing of deep-water physoclistous species can lead to increased stress and impairment often resulting in immediate release mortality. We made use of a condition index (BtR score) to evaluate the relationship between CAR-related impairment and immediate release mortality in the recreational red snapper (Lutjanus campechanus) fishery. Symptoms of barotrauma and impairment showed positive relationships with capture depth and occurred more frequently during the summer sampling than the fall. Impairment, as measured by BtR score, showed significant logistic relationships with immediate release mortality proxies such as floating and erratic swimming at release. Logistic curves had inflection points at BtR scores of 0.3–0.4 (on a scale of 0–1), above which fish experienced high immediate release mortality regardless of season (60–100%). Mean BtR scores were lower than the inflection point of the logistic curve, resulting in immediate release mortality estimates ranging from 20% to 28%. Recaptured fish showed significantly lower impairment than non-recaptured fish. The BtR score is a proficient method to estimate both impairment and immediate release mortality of red snapper in field settings.

Three species of Mexican deer mice of the Peromyscus mexicanus species group (P. grandis, P. guatemalensis, and P. zarhynchus) were characterized morphologically and genetically to test hypothesized concepts of species limits. We investigated if previously proposed phenetic relationships among these 3 taxa were supported by morphometric and genetic data. Analyses of nongeographic and geographic variation for individuals from 36 localities in Guatemala and southeastern Mexico were conducted to assay morphologic and geographic boundaries. In addition, 35 mitochondrial cytochrome-b gene sequences were analyzed using maximumparsimony and Bayesian inference methods to determine relationships among the 3 taxa. This study based on comparisons to type specimens provided support for the presence of 3 morphologically and genetically distinct units. Our analyses suggest that P. grandis and P. guatemalensis are more closely related to each other than either is to P. zarhynchus, rejecting existing hypotheses that suggest that P. zarhynchus and P. grandis are phenetically more similar. The results of this study depict relationships among other members of the P. mexicanus group and patterns of speciation and biogeography and allow identification of regionally important phylogeographic units in Mesoamerica. DOI: 10.1644/09-MAMM-A-167.1.

Size-standardized craniometric variation was investigated among species of the genus Artibeus. Eleven extant and one extinct species were examined using geometric and linear morphometric analyses to evaluate morphological differences among species. Based on 19 landmarks located in the ventral side of the cranium, 29 size-standardized linear measurements were calculated and used for statistical multivariate analyses. Discriminant Function Analysis showed major interspecific differences in shape between A. anthonyi and A. concolor with respect to the remaining extant species of Artibeus. These two species are described as morphologically unique morphotypes with a broader rostrum, enlarged squamosal region, and wider basicranium. Specifically, a broader premaxilla is the character that better discriminates A. anthonyi from all other species, whereas a broader squamosal region (particularly the deep mandibular fossa, and elongated squamosal) and wider braincase are the main characters differentiating A. concolor. All other species of the genus overlap to varying extents in their morphology showing high shape similarities. The least variant shape features include the pterygoid fossa, the glenoid (mandibular) fossa, the maxillae, and the occipital region; these regions in all cases contribute to mechanical aspects of jaw function and bite. The fact that the least variant aspects of skull shape all involve feeding is consistent with the hypothesis that selection has favored a specific diet-associated morphology rather than divergence or character displacement in Artibeus.

Behavioural lateralization has been observed in many species of fishes during stimulus-specific tasks. However, one area that has been overlooked is the study of naive side bias in motor behaviour of fishes in the absence of direct visual stimulus. To this end, we examined naive side biases in motor behaviour in five species of minnows (Osteichthyes: Cyprinidae). Fifteen individuals of each species were subjected to a T-shaped test arena, with 40 randomized replicates per individual. We took advantage of rheotaxis by running a slow current of water through each arm of the test apparatus. Of the 75 individuals tested, 55 showed a rightward turning preference. The overall right-biased behaviour observed in these fishes in the absence of systematic stimulus strongly suggests that a stimulus-free control condition be included in the experimental design whenever plausible for studies of laterality in fishes and presumably in other organisms.

The purpose of this study was to assess morphological differences between stunted and non-stunted white perch Morone americana and green sunfish Lepomis cyanellus. Few female M. americana were captured; thus, morphological differences between adult males and juveniles were assessed for M. americana. Similarly, few immature (juvenile) L. cyanellus were captured for the stunted morphotype; thus, male and female morphological differences were assessed for L. cyanellus. Features of the head tended to be relatively larger in stunted fish of both species, whereas the mid-body tended to be relatively larger in non-stunted M. americana, but not in non-stunted L. cyanellus. Adult and juvenile morphology overlapped considerably in non-stunted M. americana, but there was a clear distinction between adult and juvenile morphology of stunted M. americana. There was little sexual dimorphism in shape in stunted L. cyanellus, whereas sexual dimorphism was evident in non-stunted L. cyanellus. It appears that selective forces imposed by predation and food limitation may contribute to morphological diversification between stunted and non-stunted fishes.

Campbell, M. D., Patino, R., Tolan, J., Strauss, R., and Diamond, S. L. 2010. Sublethal effects of catch-and-release fishing: measuring capture stress, fish impairment, and predation risk using a condition index. – ICES Journal of Marine Science, 67: 513–521. The sublethal effects of simulated capture of red snapper (Lutjanus campechanus) were analysed using physiological responses, condition indexing, and performance variables. Simulated catch-and-release fishing included combinations of depth of capture and thermocline exposure reflective of environmental conditions experienced in the Gulf of Mexico. Frequency of occurrence of barotrauma and lack of reflex response exhibited considerable individual variation. When combined into a single condition or impairment index, individual variation was reduced, and impairment showed significant increases as depth increased and with the addition of thermocline exposure. Performance variables, such as burst swimming speed (BSS) and simulated predator approach distance (AD), were also significantly different by depth. BSSs and predator ADs decreased with increasing depth, were lowest immediately after release, and were affected for up to 15 min, with longer recovery times required as depth increased. The impairment score developed was positively correlated with cortisol concentration and negatively correlated with both BSS and simulated predator AD. The impairment index proved to be an efficient method to estimate the overall impairment of red snapper in the laboratory simulations of capture and shows promise for use in field conditions, to estimate release mortality and vulnerability to predation.

Increasing the scope and accuracy of information about pinniped diets obtainable from non-invasive techniques is increasingly important, particularly in cases where pinniped species are threatened or endangered. This study is the first to explore the potential for using elemental analysis of the otoliths found in scat to enhance the information available for diet analyses. We investigated the effects of pinniped digestion on otolith microchemistry using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). We compared the elements contained in the edges (adult stage) and cores (larval/juvenile stage) of otoliths from Pacific herring (Clupea pallasii), Atka mackerel (Pleurogrammus monopterygius), and Walleye pollock (Theragra chalcogramma) recovered from the scat of captive Steller sea lions (Eumetopias jubatus) to elements in a sample of pristine (undigested) otoliths. We found that digestion had a significant effect on four of the six sampled combinations of species and otolith region (herring edges and cores, mackerel edges, and pollock cores), and that Rb most frequently showed significant differences in concentration after digestion. We could significantly discriminate among species of both pristine and digested otoliths using either otolith edges or cores with the elements Ba, Rb, Sr, Y, and Mg. When compared to previously identified digested otoliths, unknown samples of the three species of digested otoliths could be discriminated with 55–100% accuracy depending on species and otolith region. When compared to a library of previously identified pristine and digested otoliths, unknown samples of digested otoliths could be discriminated to species with 65–88% accuracy. When the group of unknown digested otoliths was compared to known pristine otoliths, discrimination ranged from 45 to 65%. These results indicate that elemental analysis could be used to supplement visual identification of otoliths from scat. However, further research is required to determine whether elemental analysis of digested otoliths could be useful for prey fish population studies.

Western Burrowing Owls (Athene cunicularia hypugaea) often live in close proximity to humans, yet their behavioral responses to anthropogenic land use are largely unknown. We compared the diurnal foraging and activity budgets of adult male Burrowing Owls during the breeding seasons of 2004 and 2005 at three urban and three rural sites in northwestern Texas. The owls (N = 17 urban, 10 rural) spent most of their time being vigilant, resting, preening, perching, and in the burrow; less time was spent hunting, eating, provisioning the mate or young, flying, or engaging in other behaviors. Activity budgets did not differ significantly with land use. There were significant differences in activity budgets among study sites and with respect to times of day, weather variables, and numbers of owlets. Although hunting success and provisioning rates did not vary between urban and rural sites, aerial insects were taken as prey more often at urban than at rural sites. More foraging attempts occurred in habit...

Understanding patterns in terms of the mechanistic processes that produce them is the essence of ecology. However, many studies merely document nonrandom patterns of species coexistence without providing insight into the structuring mechanisms and their scale dependence. Moreover, few studies address the mechanisms driving functional diversity. The objectives of this study were to document empirical patterns of species coexistence within stream fish assemblages across a broad geographic region, addressing both the functional and taxonomic organization of those assemblages, and to determine whether the structuring mechanisms are scale dependent. We gathered data from a report published by the Texas Parks and Wildlife Department that provided empirical species abundance distributions for 62 assemblages from 7 ecoregions and 18 river basins. For each assemblage, we simulated expected species abundances using five previously published models of niche apportionment. These models generate relative abundances in proportion to niche breadth and are constrained to maintain observed species richness, but they do not include information on species identity. These models included four stochastic variants of a geometric series (dominance preemption, random fraction, broken stick, and dominance decay) in which species abundances relate directly to niche breadth and one model (random assortment) in which abundances are independent of niche partitioning altogether. To assess scale dependence, we repeated the analyses after pooling assemblages by ecoregion, river basin, and the entire state. The patterns of niche apportionment for assemblages pooled according to river basin are more consistent with local assemblages than with assemblages pooled according to ecoregions or the entire state. These results suggest that niche apportionment plays a crucial role in structuring stream fish assemblages and that functional groups divide niche space more evenly than do species.

A new morphometric approach was developed to study morphological variation within P1 elements commonly referred to as Idiognathodus simulator, which was selected to be the biostratigraphic marker for the base of the global Gzhelian Stage (Carboniferous). This new approach combines landmark-based geometric morphometrics with eigen analyses to analyze shape variation within P1 elements of the I. simulator group, and could be used to analyze shape variation in other morphologically similar conodont groups. Specimens analyzed were obtained from three sections of the early Gzhelian Heebner Shale of the Oread cyclothem in the North American Midcontinent region, the cyclothem from which I. simulator was originally named. This analysis shows that the I. simulator group comprises a set of at least five species with asymmetrical P1 element pairs, relatively short adcarinal ridges, and a variably developed eccentric groove. Species discrimination is based on the presence of caudal and rostral lobes, character of the adcarinal ridges, and platform shape. The species I. simulator is restricted to P1 elements with a caudal adcarinal ridge that is isolated from the caudal platform margin. Idiognathodus lateralis sp. nov. is erected to include P1 elements with a caudal adcarinal ridge that is not isolated from the caudal platform margin.

Late Paleoindian typology on the southern High Plains has suffered from overlapping definitions and subjectivity in assigning individual projectile points to types. To address perceived projectile point variability in the region, assemblages from several localities on the southern High Plains are examined for statistical differences in shape. Digital photographs of projectile points are used to digitize point outlines. Landmark coordinate data then are used to delineate 10 interlandmark characters. Multivariate analysis of projectile points from eight assemblages reveals that the primary difference in point shape lies between long points with narrow bases and short points with wide bases. Analysis of characters by raw material type or source discerned no significant differences. Variation in point form represented by most of the assemblages, including the Plainview and Milnesand type assemblages, overlaps to a significant degree. The Lubbock Lake FA5-17 assemblage, consisting of long points with n...

Although the swimming behavior of Oryzomys palustris has been described, little is known about how long this species will remain in an area that is inundated by several centimeters of water. This study documents the response of an O. palustris population to habitat inundation in a coastal prairie locality of southeastern Texas. During a mark-recapture study conducted during 2002 and 2003, we live- trapped O. palustris on a grid in an area that experienced prolonged ($5 mo) inundation during 2 of our 6 quarterly trapping periods. We describe a trapping technique, using foam rafts to support rodent live-traps, that is suitable for use in inundated areas. Despite long-term inundation, little available refuge, and an apparent complete turnover of the population, we estimated population densities of ca. 29 individuals per hectare during inundation, only a moderate decrease from the higher levels encountered before and after inundation. RESUMEN—A pesar de que se ha descrito el comportamiento natatorio de Oryzomys palustris, se sabe poco sobre cuanto tiempo permanece esta especie en un a inundada por varios cento ´metros de agua. Esta investigacion documenta la respuesta de una poblacion de O. palustris a la inundacion de habitat en un llano costero del sureste de Texas. Durante un estudio de marca-recaptura realizado durante el 2002 y el 2003, capturamos vivos los O. palustris, en una parcela de un area que sufrioinundacion prolongada ($5 meses), durante 2 de nuestras 6 sesiones trimestrales de trampeo. Describimos una tecnica de trampeo usando balsas de unicel para sostener trampas para roedores, que son utiles para usar en a inundadas. A pesar de la prolongada inundacion, la falta de refugio disponible y un aparente cambio completo de la poblacion, estimamos una densidad poblacional de aproximadamente 29 individuos por hectarea durante la inundacion , solo una moderada disminucion del nivel mas alto encontrado antes y despues de la inundacion .

Prior data indicated that enhanced avail- ability of sucrose, a major product of photosynthesis in source leaves and the carbon source for secondary wall cellulose synthesis in fiber sinks, might improve fiber quality under abiotic stress conditions. To test this hypothesis, a family of transgenic cotton plants (Gos- sypium hirsutum cv. Coker 312 elite) was produced that over-expressed spinach sucrose-phosphate syn- thase (SPS) because of its role in regulation of sucrose synthesis in photosynthetic and heterotrophic tissues. A family of 12 independent transgenic lines was char- acterized in terms of foreign gene insertion, expression of spinach SPS, production of spinach SPS protein, and development of enhanced extractable Vmax SPS activ- ity in leaf and fiber. Lines with the highest Vmax SPS activity were further characterized in terms of carbon partitioning and fiber quality compared to wild-type and transgenic null controls. Leaves of transgenic SPS over-expressing lines showed higher sucrose:starch ra- tio and partitioning of 14 C to sucrose in preference to starch. In two growth chamber experiments with cool nights, ambient CO2 concentration, and limited light below the canopy, the transgenic line with the highest SPS activity in leaf and fiber had higher fiber micro- naire and maturity ratio associated with greater thick- ness of the cellulosic secondary wall.

The ectoparasites of a small mammal community within an intertidal zone in the upper Gulf coast region of Texas were studied to assess the seasonal variation in abundances of the mite Gigantolaelaps mattogrossensis (Fonseca) (Acari: Laelapidae) on the marsh rice rat, Oryzomys palustris (Harlan). Further study into the ecology and dynamics of this parasite-host relationship was deemed to be necessary to expand the understanding of these potential participants in the ecology of Bayou Hantavirus, an important causative agent of Hantavirus pulmonary syndrome. The objective of this study was to determine the effects of five predictor variables on mite abundance: prevalences of hosts, relative humidity, precipitation, temperature, and length of daylight. Mite abundance was modeled as a function of the five variables with analyses of variance and multiple regressions; however, because the predictor variables pertain to the sampling period rather than to the individual rodent host, the effective sample size was small and thus the sums of squares and cross products matrix was singular. We therefore developed and used a new method for estimating regression coefficients based on the "noise-addition method" (random residual variation) combined with a bootstrap step converting the reduced rank data to full rank, providing realistic estimates of confidence intervals for the regression statistics. The population abundances of mites fluctuated significantly across collecting periods. Humidity and precipitation were the most influential variables in explaining the variation in abundances of mites. Model interpretation suggests that G. mattogrossensis is a nidicolous parasite. These results provide a baseline understanding of the seasonal interactions between parasite and host.

Missing data are frequent in morphometric studies of both fossil and recent material. A common method of addressing the problem of missing data is to omit combinations of characters and specimens from subsequent analyses; however, omitting different subsets of characters and specimens can affect both the statistical robustness of the analyses and the resulting biological interpretations. We describe a method of examining all possible subsets of complete data and of scoring each subset by the ‘condition’ (ratio of first eigenvalue to second, or of second to first, depending on context) of the corresponding covariance or correlation matrix, and subsequently choosing the submatrix that either optimizes one of these criteria or matches the estimated condition of the original data matrix. We then describe an extension of this method that can be used to choose the ‘best’ characters and specimens for which some specified proportion of missing data can be estimated using standard imputation techniques such as the expectation-maximization algorithm or multiple imputation. The methods are illustrated with published and unpublished data sets on fossil and extant vertebrates. Although these problems and methods are discussed in the context of conventional morphometric data, they are applicable to many other kinds of data matrices. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88, 309–328.

Although the examination of latitudinal gradients of species richness is common, little attention has been devoted to other components of biodiversity such as phenetic diversity. Because the phenotype reflects aspects of an organism's environment, ecological relationships and evolutionary history, measures of phenetic diversity likely provide complimentary information to that of species richness, and may provide unique insights for understanding the mechanistic basis to patterns of biodiversity. Herein, we evaluate latitudinal gradients in the phenetic diversity of 32 New World bat communities. Seven morphological characters were used to estimate phenotypic variation among bat species within local communities. Principal components analysis decomposed this variation into axes of size and shape. Three measures of phenetic diversity were calculated separately for size and for shape axes. The range of species scores on a particular axis described the amount of phenetic variation encompassed by species in a community. The standard deviation of minimum spanning-tree segment lengths described uniformity of species. Average nearest-neighbor distances described local packing. We separately regressed these six measures on local species richness and latitude separately. Variation in species richness accounted for a significant amount of variation in each measure of phenetic diversity. Latitude also accounted for significant variation in phenetic diversity except for the standard deviation of minimum-spanning tree segment lengths and the average nearest-neighbor distance on the shape axis. More importantly, gradients in phenetic diversity were significantly different than would be expected as a consequence of latitudinal gradients in species richness. Nonetheless, when variation among communities regarding the richness and composition of their regional faunas was taken into consideration, differences between empirical and simulated gradients were nonsignificant. Thus, factors that determine the composition of regional faunas have a great impact on the phenetic diversity of communities and ultimately the latitudinal gradient in biodiversity.

The assessment of biotic responses to habitat disturbance and fragmentation generally has been limited to analyses at a single spatial scale. Furthermore, methods to compare responses between scales have lacked the ability to discriminate among patterns related to the identity, strength, or direction of associations of biotic variables with landscape attributes. We present an examination of the relationship of population- and community- level characteristics of phyllostomid bats with habitat features that were measured at mul- tiple spatial scales in Atlantic rain forest of eastern Paraguay. We used a matrix of partial correlations between each biotic response variable (i.e., species abundance, species richness, and evenness) and a suite of landscape characteristics to represent the multifaceted asso- ciations of bats with spatial structure. Correlation matrices can correspond based on either the strength (i.e., magnitude) or direction (i.e., sign) of association. Therefore, a simulation model independently evaluated correspondence in the magnitude and sign of correlations among scales, and results were combined via a meta-analysis to provide an overall test of significance. Our approach detected both species-specific differences in response to land- scape structure and scale dependence in those responses. This matrix-simulation approach has broad applicability to ecological situations in which multiple intercorrelated factors contribute to patterns in space or time.

We describe the morphological changes associated with starvation in larval largemouth bass Micropterus salmoides and develop bivariate and multivariate morphological indices of nutritional status. We obtained hatchery-reared largemouth bass, raised them until completion of fin development, and divided them into two randomized experimental groups of fed and unfed fishes. Fed fishes were provided with newly hatched brine shrimp twice daily. We quantified morphological changes in body shape using 23 morphometric characters. After only 3 d of food deprivation, we were able to detect statistically significant differences in morphology between the fed and unfed fish using multivariate analysis. The magnitude of the mean difference increased over time. An unexpected result suggested that a simple, bivariate ratio of standard length to body depth at the anus was almost as efficient and robust at classifying fed and unfed largemouth bass from an independent data set as a multivariate index based on all 23...

Search tactics are cognitive processes, or decision mechanisms, that organisms use to locate available resources such as food, mates, refugia, and high-quality habitats. However, our knowledge of the actual tactics that animals use while searching for resources is limited, and very little empirical evidence has been accumulated. Therefore, we developed a suite of search-tactic models (1) to simulate possible searching behaviors of mobile organisms so that inferences can be made about their decision mechanisms, and (2) to determine the extent to which different models produce paths that approximate a globally optimal solution. The search-tactic models included deterministic and probabilistic searches in attempt to characterize biologically plausible searching behaviors. Classical linear multivariate methods (discriminant function analysis, Mahalanobis distances) and nonlinear artificial neural networks were used to discriminate the paths produced by the different models and to classify ‘‘unknown’’ foraging paths into one of the search-tactic models, based on the geometry of the resulting paths. Both linear and nonlinear analyses suggested that it is possible for animals to use a nearest-neighbor search tactic to search with near-optimum efficiency without having complete knowledge of the specific locations of all available resources. Furthermore, both methods of analyses demonstrated that it might be possible to use characteristics of foraging paths in an experimental setting to make inferences about the actual decision mechanisms animals use while searching for resources. Key words: computer simulation, discrimination, foraging paths, multivariate analysis, neural networks, searching behavior, search tactics. [Behav Ecol 15:248–254 (2004)]

The mortality of fish captured in fishing tournaments has commonly been estimated incorrectly and, thus far, only one account has presented an estimate of the standard error or confidence interval for tournament-associated mortality. In this article we describe methods for estimating the initial, delayed, and total mortality of tournament-caught fish and provide formulae for estimating the sampling variances of these estimates. The absence of such estimates from previous studies may explain an observed lack of change in tournament-associated mortality between the 1980s and the 1990s. Our methods provide insight into the design of studies of tournament-associated mortality and suggest, for example, that many previous studies have held too few fish for observation and have greatly undersampled control fish. Improved study design and reporting should increase our understanding of the factors influencing tournament-associated mortality.

Vertebrate skeletons, particularly fossils, commonly have damaged, distorted, or missing structures. Because multivariate morphometric methods require complete data matrices, there are two possible solutions: to omit the specimens or characters having missing values, or to estimate missing values from the remainder of the data. Omission of specimens or characters reduces the data available for analysis, and thus the power to detect patterns or differences. Univariate and bivariate-regression methods are known to reduce the total variance of the data, and thus are not considered here. We compared the two most common multivariate methods: expectation-maximization (EM), which uses the covariance matrix directly, and principal-component (PC) estimation, based on regression of characters on principal components. Performance was evaluated by computer simulation of randomly introduced missing data in constructed data sets of known structure, and in several complete fossil (Pterodactylus skeleton) and re...

The lack of information surrounding natural history and ecology of the endangered Morelet's crocodile (Crocodylus moreletii) has prompted a baseline study of the population genetics for this species. Nine microsatellite loci have been used to estimate genetic structure within and gene flow patterns among crocodiles (using a recently described maximum likelihood approach) from seven localities in north-central Belize. Individuals from the seven localities grouped into four apparent populations. Within localities, a high degree of genetic heterogeneity was observed. Among all localities, some subdivision was present (FST = 0.062; RST = 0.100). Furthermore, among the apparent populations, we found a significant correlation between geographic distance and genetic subdivision. Our findings suggest a relatively high level of migration among populations (Nm = 5.15) and are consistent with an isolation-by-distance model of gene flow. Two contiguous subpopulations in particular, New River and New River La...

Phylogenetic relationships among 7 species of Reithrodontomys were examined using the complete mitochondrial cytochrome-b gene. DNA-sequence data were analyzed using parsimony (weighted and unweighted) and genetic distance methods. In all analyses, R. sumichrasti, R. megalotis, and R. zacatecae formed a monophyletic clade. Likewise, R. montanus and R. raviventris were depicted as sister taxa in all analyses. Our study supports recognition of R. zacatecae as a species distinct from R. megalotis and recognition of R. raviventris as distinct from R. montanus. Patterns of chromosomal evolution were examined using differential staining as resolved by 3 DNA probes and fluorescent in situ hybridization. Using the phylogeny based on DNA sequences, we concluded that there has been extensive chromosomal repatterning (in most cases karyotypic megaevolution) in the evolution of R. zacatecae, R. megalotis, R. sumichrasti, R. montanus, R. raviventris, and R. humulis.

Correspondence: R. E. Strauss, Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409-3131, U.S.A. (email: rich.strauss@ttu.edu). The necessity of objectively determining the numbers of groups of organisms, along with their shapes, positions and other characteristics, arises often in ecological and behavioural studies (Hamilton 1971; Radakov 1973; Morse 1980; Ginsberg & Young 1992; Whitehead 1997). Choice by isolated animals of a particular conspecific group (herd, flock, or school) as a function of group size, shape and composition can have important consequences for their predation risk and foraging success (Caraco et al. 1980; Magurran & Pitcher 1983; Clark & Mangel 1986; Hager & Helfman 1991). Studies of grouping behaviour, in the laboratory and in the wild, must be based on operationally objective characterization of the numbers and sizes of such groups. This problem has recently emerged in our study of schooling behaviour in Corydoras paleatus, a benthic South American catfish that schools in two dimensions rather than three and displays a fission/fusion social behaviour that depends on group size. We initially observed that seven or fewer individuals (more or less) almost invariably cluster into a single aggregation, whereas 12 or more individuals (more or less) tend to spend most of their time separated into two aggregations. Groups of 7–12 individuals typically display an intermediate behaviour, alternately separating from one ‘school’ into two and remerging. Larger groups commonly associate and disassociate into two, three or more schools, usually differing in shape, orientation and number of individuals. Our objective has been to dissect this dynamic behaviour by filming aggregations from above under various experimental conditions, digitizing the positions and orientations of individuals, and quantifying the spatial structure over time using statistical tools appropriate for such studies (Morgan et al. 1976; Diggle 1983; Cressie 1991; Whitehead 1997). However, an unexpectedly difficult analytical task has been to determine objectively, at a particular time, the number of schools present and the most reasonable assignment of individuals to schools. This is complicated by the following factors, which are not uncommon in studies of group structure and dynamics (Hamilton 1971; Radakov 1973): (1) schools can differ in extent (area) and

The bacterium Erwinia chrysanthemi is a model plant pathogen, responsible for causing cell death in plant tissue. Cell-wall depolymerizing enzymes and avirulence proteins essential for parasitism by this bacterium utilize dedicated type II and type III secretion systems, respectively. Although E. chrysanthemi is not recognized as a mammalian pathogen, we have observed that the bacterium can adhere to, cause an oxidative stress response in and kill cultured human adenocarcinoma cells. These bacteria express a surface protein that bears immunological identity to intimin, a protein required for full virulence of enterohemorrhagic and enteropathogenic Escherichia coli. A type III secretion mutant of E. chrysanthemi was observed to have a significantly lower capability of causing death than the wild-type strain in parallel cultures of human colon adenocarcinoma cells. These observations suggest that E. chrysanthemi has the potential to parasitize mammalian hosts as well as plants.

Wear-induced changes in the crown topography of molariform teeth have been widely used to index relative age in rodents. To assess the consistency of molar-wear estimates in natural populations of a sigmodont rodent ( Bolomys lasiurus ), we investigated the association between molar wear and two other age-dependent craniodental characters: degree of exposure of molar roots from the alveoli and ossification of the basisphenoid-basioccipital suture. We compared magnitudes of Spearman correlation coefficients among states of these characters in samples cross-classified by vegetation, season, and locality, under the null hypothesis of high correlation in the absence of differential environmental effects on molar wear. A bootstrap procedure was used to derive empirical sampling distributions of the age-index correlations and, thus, to establish realistic confidence intervals. We then employed a multivariate procedure to reduce subjectivity of classifying combinations of indices of age into age classes. Using a principal component analysis of the correlation matrix of craniodental indices, variation expressed among indices was summarized as a multivariate age factor. An objective ordering of sets of indices of age (the various combinations of tooth-wear, molar-root exposure, and suture-ossification conditions observed among all samples) was provided by projecting individuals onto the first principal component. The method revealed age-frequency differences between wet- and dry-season samples from northeastern Brazil, ostensibly due to the occurrence of a reproductive peak at the beginning of the rainy season, and predicted a maximum life span for B. lasiurus of ca. 1—1.5 years in the wild.

Metamorphosis is of particular interest in ecological and evolutionary studies because the decoupling of larval and adult growth patterns potentially allows the adaptive diversification of the separate stages. To better understand how differential growth patterns might contribute to evolutionary differences in body form, growth allometries in relation to interspecific morphometric differences were studied in two species of loricariid catfishes that can be completely discriminated in the smallest larvae examined. Many characters undergo metamorphic shifts in allometric growth rates, although the timing of the shifts seems to vary among characters. Interspecific allometric differences are highly correlated with the discriminatory values of the characters in larvae, but a comparable correlation is absent in adults. This suggests that metamorphosis serves to “release”; adult growth patterns from phylogenetic constraints on growth.

Nucleotide sequences from the mitochondrial control region and genotypes from 5 nuclear microsatellite loci were used to examine genetic structure and infer recent (within approximately the last 3,000 years) evolutionary history of a population (549 individuals) of the southern plains woodrat (Neotoma micropus). Observed heterozygosity values ranged from 0.61 to 0.89 across microsatellite loci and systematically were lower than expected heterozygosity values (0.66-0.95). Probability of unique identity using microsatellite data was high (1 individual in 66,005,424). Fifty-three mitochondrial haplotypes were obtained from 150 individuals. F(ST) values estimated from sequence and microsatellite data were 0.061 and 0.011, respectively, and the R(ST) for microsatellite data was 0.007. Within-group genetic variation ranged from 93.90% to 99.99% depending on whether sequence or microsatellite data were examined. Analyses of microsatellite data suggested that all sampled individuals belonged to a single population, albeit genetically diverse. However, combined data analyses suggested the presence of low levels of substructure attributable to maternal lineages within the population. Low nucleotide-diversity values (0.007-0.010) in addition to high haplotype-diversity values (0.915-0.933) indicate a high number of closely related haplotypes, and suggest that this population may have undergone a recent expansion. However, Fu's F(S) statistic did not fully support this finding, because it did not reveal a significant excess of recent mutations. A phylogenetic approach using the haplotype sequence data and a combined set including both haplotype and genotype data was used to test for evolutionary patterns and history.

“…not enough to kill the streptococci but enough to educate them to resist penicillin” (Alexander Fleming, Nobel Prize lecture, Dec. 11, 1945). These prophetic words underscore the arms race in which we find ourselves today. Large populations and mutable genomes give microbes a profound capacity to respond to changing environmental conditions. The misuse of antibiotics in human health and agriculture has contributed to continuing microbial drug resistance. Thus, 65 years later, in 2010, we continue to battle microorganisms and strive to design novel and useful antimicrobial agents (1).

Hybognathus placitus collected from several west Texas streams exhibit sexual dimorphism in body form, which is unusual in cyprinids. Seventeen morphological measurements, including standard length, were made on 62 specimens and analyzed for sexual dimorphism. Partial warp scores were used to describe sexual dimorphism in body shape. There was no difference in standard length between males and females (ANOVA, P = 0.9038, F1,60 = 0.0147), but there was a highly significant (MANOVA, F1,60 = 4.78, P < 0.001) sexual dimorphism in body shape. Overall, males have relatively longer first dorsal fin rays, larger heads, and caudal peduncles, whereas females are deeper bodied and have relatively longer trunks, from the pelvic fin insertion to the anal vent. Differences between male and female H. placitus in length of the first dorsal fin ray are readily apparent and can potentially be used for field identification.

In the United States, Bayou virus (BAYV) ranks second only to Sin Nombre virus (SNV) in terms of hantavirus pulmonary syndrome (HPS) incidents, having been confirmed in cases from Texas and Louisiana since its discovery in 1994. This study on BAYV infection among sympatric, non-oryzomyine rodents ("spillover") in Freeport, TX, is the first to link patterns of hantavirus interspecific spillover with the spatiotemporal ecology of the primary host (marsh rice rat, Oryzomys palustris). Mark-recapture and/or harvest methods were employed from March 2002 through May 2004 in two macrohabitat types. Rodent blood samples were screened for the presence of IgG antibody to BAYV antigen by IFA after which Ab-positive blood, saliva, and urine were analyzed for the presence of viral RNA by nested RT-PCR. From 727 non-oryzomyine captures, five seropositive (but not viral RNA positive) individuals were detected: one each of Baiomys taylori, Peromyscus leucopus, and Reithrodontomys fulvescens; and two Sigmodon hispidus. Spillover hosts were not associated with macrohabitat where O. palustris abundance, density, or seroprevalence was highest. Rather, spillover occurred in the macrohabitat indicative of greater overall disturbance (as indicated by grazing and exotic plant diversity) and overall biodiversity. Spillover occurred during periods of high seroprevalence detected elsewhere within the study region. Spillover locations differed significantly from all other capture locations in terms of percent water, shrub, and grass cover. Although greater habitat and mammal diversity of old-fields may serve to reduce seroprevalence levels by tempering intraspecific contacts between rice rats, greater diversity also may create an ecologically opportunistic setting for BAYV spillover. Impacts of varying levels of disturbance and biodiversity on transmission dynamics represent a vastly uncharacterized component of the evolutionary ecology of hantaviruses.

A common problem in morphometric studies is to determine whether, and in what ways, two or more previously established groups of organisms differ. Discrimination of predefined groups is a very different problem than trying to characterize the patterns of morphological variation among individuals, and so the kinds of morphometric tools used for these two kinds of questions differ. In this paper I review the basic procedures used for discriminating groups of organisms based on morphological characteristics – measures of size and shape. A critical reading of morphometric discrimination studies of various kinds of organisms in recent years suggests that a review of procedures is warranted, particularly with regard to the kinds of assumptions being made. I will discuss the main concepts and methods used in problems of discrimination, first using conventional morphometric characters (measured distances between putatively homologous landmarks), and then using landmarks directly with geometric morphometric approaches.

Morphological variation among populations of Leporinus friderici (Bloch), an anostomid fish of widespread neotropical distribution, has been hypothesized but never conclusively demonstrated. We used multivariate procedures to examine patterns of morphometric variation among populations of L. friderici from three South American biogeographic regions: the Parana-Paraguay River and Amazon River basins of Brazil, and the Marowijne River basin of Suriname. Samples from the southern Parana-Paraguay basin are completely distinct from the northern Amazonian and Suriname regions in principal components analysis, primarily on the basis of body elongation and orbit differcnces. Samples from the two northern regions were separated in a size-free canonical variates analysis by differences in relative body depth. These results emphasize a need for further studies of neotropical fish species with similar distribution patterns.

Reznick and Endler investigated natural variation in life-history traits of populations of Trinidad guppies exposed to one of three intensities of predation: (i) high predation directed primarily at adults, (ii) moderate predation directed primarily at juveniles, and (iii) low predation. They were able to document significant interpopulational differences in life-history traits associated with this differential predation on a trait-by-trait basis. However, the present extended multivariate analysis indicates that (1) life-history traits do not differ significantly between populations exposed to moderate versus low predation, although both differ greatly from high-predation populations; (2) life-history variation is strongly unifactorial; and (3) despite the importance of predation effects, approximately 17% of the variation in life-history variables cannot be accounted for by predation intensity. Residual variation has no obvious geographical patterns, but instead seems to reflect local environmental variability. Life-history differences between predation regimes are consistent with residual patterns of variation within regimes, suggesting that local variation provides the raw material for extrapolation in response to predation, but also that it influences the direction of correlated change in life-history traits.

Archaeopteryx is almost universally considered a primitive bird. Debate persists, however, about the taxonomic assignment of the six skeletal fossils. Allometric scaling of osteological data shows that all specimens are consistent with a single growth series. The absence of certain bone fusions suggests that no specimen is full-grown. Allometric patterns, as compared to growth gradients of other dinosaurs, extant ectotherms, and extant endotherms, suggest that Archaeopteryx was likely a homeothermic endotherm with rapid growth and precocial abilities for running and flying. Multivariate allometric models offer a significant potential for interpreting ontogenetic patterns and phylogenetic trends in the fossil record.

The ectoparasites of a small mammal community within an intertidal zone in the upper Gulf coast region of Texas were studied to assess the seasonal variation in abundances of the mite Gigantolaelaps mattogrossensis (Fonseca) (Acari: Laelapidae) on the marsh rice rat, Oryzomys palustris (Harlan). Further study into the ecology and dynamics of this parasite-host relationship was deemed to be necessary to expand the understanding of these potential participants in the ecology of Bayou Hantavirus, an important causative agent of Hantavirus pulmonary syndrome. The objective of this study was to determine the effects of five predictor variables on mite abundance: prevalences of hosts, relative humidity, precipitation, temperature, and length of daylight. Mite abundance was modeled as a function of the five variables with analyses of variance and multiple regressions; however, because the predictor variables pertain to the sampling period rather than to the individual rodent host, the effective sample size was small and thus the sums of squares and cross products matrix was singular. We therefore developed and used a new method for estimating regression coefficients based on the "noise-addition method" (random residual variation) combined with a bootstrap step converting the reduced rank data to full rank, providing realistic estimates of confidence intervals for the regression statistics. The population abundances of mites fluctuated significantly across collecting periods. Humidity and precipitation were the most influential variables in explaining the variation in abundances of mites. Model interpretation suggests that G. mattogrossensis is a nidicolous parasite. These results provide a baseline understanding of the seasonal interactions between parasite and host.

We live-trapped 40 northern pocket gophers across two years from the Anaconda Smelter Superfund Site, Anaconda, Montana, USA, to determine their exposure to five metal contaminants and effects of exposure on selected measurements. Soil, gopher blood, liver, kidney, and carcass samples were analyzed for arsenic, cadmium, lead, copper, and zinc. Hematological parameters, kidney and liver porphyrins, and red blood cell d-aminolevulinic acid dehydratase (ALAD) activity were also measured. Micronutrients Cu and Zn were detected in all tissues analyzed, and Cd, Pb, and As were detected less frequently. We report differences in metal distribution among different tissues and differences in bioaccumulation for different metals within the same tissue. No significant differences were observed in concentrations of Zn or Cu in any tissue across the study site, but relationships between lead in soil and lead in carcass proved especially strong (r 2 5 0.80; p , 0.001; n 5 18). Among biomarker data, we observed a negative relationship between concentration of lead in the soil and ALAD activity in gophers with detectable concen- trations of lead in their blood (r 2 5 0.45; p 5 0.006; n 5 15). Results of this study suggest that northern pocket gophers are useful biomonitors of environmental Pb, Cd, and As contamination, and their broad geographic range across North America could allow them to be an important component of site-specific metals assessments.