Mary C. Christman

Seasonal and interannual variability of climate and vegetation indices across the Amazon

Drought exerts a strong influence on tropical forest metabolism, carbon stocks, and ultimately the flux of carbon to the atmosphere. Satellite-based studies have suggested that Amazon forests green up during droughts because of increased sunlight, whereas field studies have reported increased tree mortality during severe droughts. In an effort to reconcile these apparently conflicting findings, we conducted an analysis of climate data, field measurements, and improved satellite-based measures of forest photosynthetic activity. Wet-season precipitation and plant-available water (PAW) decreased over the Amazon Basin from 1996−2005, and photosynthetically active radiation (PAR) and air dryness (expressed as vapor pressure deficit, VPD) increased from 2002–2005. Using improved enhanced vegetation index (EVI) measurements (2000–2008), we show that gross primary productivity (expressed as EVI) declined with VPD and PAW in regions of sparse canopy cover across a wide range of environments for each year of the study. In densely forested areas, no climatic variable adequately explained the Basin-wide interannual variability of EVI. Based on a site-specific study, we show that monthly EVI was relatively insensitive to leaf area index (LAI) but correlated positively with leaf flushing and PAR measured in the field. These findings suggest that production of new leaves, even when unaccompanied by associated changes in LAI, could play an important role in Basin-wide interannual EVI variability. Because EVI variability was greatest in regions of lower PAW, we hypothesize that drought could increase EVI by synchronizing leaf flushing via its effects on leaf bud development.

The North American obligate cave fauna: regional patterns

The obligate cave faunas of nine regions of the United States –Florida Lime Sinks, Appalachians, Interior Low Plateaus, Ozarks, Driftless Area,Edwards Aquifer/Balcones Escarpment, Guadalupe Mountains, Black Hills, andMother Lode – are described and compared. The number of aquatic(stygobitic) species ranged from zero (Black Hills) to 82 (Appalachians), andthe number of terrestrial (troglobitic) species ranged from zero (Florida LimeSinks) to 256 (Interior Low Plateau). Even at the level of genus, overlapbetween regions is low. Several predictor variables (karst area, number ofcaves, number of long caves, number of deep caves, distance from the Pleistoceneice margin, distance from the late Cretaceous Sea, and vegetation type – asurrogate for productivity) were assessed using rank order statistics,especially rank order multiple regression with a backward elimination procedure.For both stygobites and troglobites, only number of caves was a significantpredictor. The absence of a karst area effect suggested that the degree of karstdevelopment is better described by the number of caves rather than area ofkarst. There was no evidence that distance to Pleistocene glacial boundaries wasimportant, but there was some support for the importance of distance from late Cretaceous sea margins, a potential source of aquatic subterranean colonists. Finally,there was no indication that surface productivity had an effect on speciesrichness. Analysis was complicated by correlations among predictor variables.

The use of degraded and shade cocoa forests by Endangered golden-headed lion tamarins Leontopithecus chrysomelas

Determining habitat requirements for threat- ened primates is critical to implementing conservation strategies, and plans incorporating metapopulation str- ucture require understanding the potential of available habitats to serve as corridors. We examined how three groups of golden-headed lion tamarins Leontopithecus chrysomelas in Southern Bahia, Brazil, used mature, swamp, secondary and shade cocoa (cabruca) forests. Unlike callitrichids that show affinities for degraded forest, Leontopithecus species are presumed to depend on primary or mature forests for sleeping sites in tree holes and epiphytic bromeliads for animal prey. In this study we quantified resource availability within each habitat, compared the proportion of time spent in each habitat to that based on availability, investigated preferences for sleeping site selection, and determined how golden- headed lion tamarins allocated time to foraging behavi- our in different habitats. Each group preferred to range in certain habitats during the day, yet patterns were not consistent across groups. In contrast, all groups preferred to sleep in mature or cabruca forest. Golden-headed lion tamarins spent a greater proportion of time foraging and eating fruits, flowers and nectar in cabruca than in mature or secondary forests. Although the extent to which secondary and cabruca forests can completely sustain breeding groups is unresolved, we conclude that both habitats would make suitable corridors for the movement of tamarins between forest fragments, and that the large trees remaining in cabruca are important sources of food and sleeping sites. We suggest that management plans for golden-headed lion tamarins should focus on protecting areas that include access to tall forest, either as mature or cabruca, for the long-term conservation of the species.

Efficiency of some sampling designs for spatially clustered populations

The efficiencies of two sampling designs for estimating the mean of a fixed, finite population are considered. The first is adaptive cluster sampling (ASRS; Thompson, 1990 Journal of the American Statistical Association) which is designed to adaptively increase sampling effort in the neighbourhood of units whose observed value meets some predefined condition. The other is Balanced Sampling Excluding Contiguous Units (BSEC) (Hedayat, Rao and Stufken, 1988, Journal of Statistical Planning and Inference), a conventional design in which neighbouring units are deliberately excluded from being sampled under the idea that they provide little new information to the sampling effort. We consider the effect of type of neighbourhood, initial sample size, condition for adaptively sampling neighbours, and degree and extent of clustering in the population on the efficiency of ASRS relative to BSEC and simple random sampling. Populations having different degrees of clustering are simulated using a modified Neyman–Scott process. We compare the design-based variances of two estimators, a Horvitz–Thompson-type estimator and a Hansen–Hurwitz-type estimator. While the Horvitz–Thompson-type estimator can have the lowest variance under some of the situations explored, it is also the most sensitive to changes in the conditions. The efficiency of the estimator often comes at the cost of a large effective sample size. In general, ASRS is more efficient when the population elements are rare and highly clustered although BSEC designs are generally more efficient for a wider array of combinations of conditions.

Sampling adequacy in an extreme environment: species richness patterns in Slovenian caves

Caves harbor a rich fauna unique to subterranean environments. Although extensive records of cave animals are available, only a small fraction of known caves in any region have been biologically assessed. We investigated the impact of incomplete sampling using one of the richest, best documented cave faunas in the world – that of the Dinaric karst of Slovenia. We utilized time snapshots (1940, 1970, and 2000) of the caves and cave fauna to analyze stability of hotspots, spatial pattern, and relationship between number of species and number of caves. Using data aggregated into 100 km2 hexagons, the location of hotspots, black–white joins, Morans I, and spatial autocorrelation all remained constant, at least from 1970 on. The linear regression coefficient of the relationship between number of caves and number of species declined with time. Most hexagons had been sampled, but there was no indication that any hexagon had been sampled intensively enough for the accumulation curve of number of caves versus number of species within a hexagon to reach an asymptote. This appeared to be the result of a highly skewed distribution of species richness among caves. Number and position of hotspots can be predicted from information on these few high diversity caves.

LESSONS LEARNED FROM EFFORTS TO RESTORE OYSTER POPULATIONS IN MARYLAND AND VIRGINIA, 1990 TO 2007

ABSTRACT A century-long decline of the fishery for the Eastern oyster Crassostrea virginica (Gmelin, 1791) in Maryland and Virginia stimulated numerous efforts by federal, state, and nongovernmental agencies to restore oyster populations, with limited success. To learn from recent efforts, we analyzed records of restoration and monitoring activities undertaken between 1990 and 2007 by 12 such agencies. Of the 1,037 oyster bars (reefs, beds, or grounds) for which we obtained data, 43% experienced both restoration and monitoring, with the remaining experiencing either restoration or monitoring only. Restoration activities involved adding substrate (shell), transplanting hatchery or wild seed (juvenile oysters), bar cleaning, and bagless dredging. Of these, substrate addition and transplanting seed were common actions, with bar cleaning and bagless dredging relatively uncommon. Limited monitoring efforts, a lack of replicated postrestoration sampling, and the effects of harvest on some restored bars hinders evaluations of the effectiveness of restoration activities. Future restoration activities should have clearly articulated objectives and be coordinated among agencies and across bars, which should also be off limits to fishing. To evaluate restoration efforts, experimental designs should include replication, quantitative sampling, and robust sample sizes, supplemented by pre- and postrestoration monitoring.

Morphological Differences Among Eyeless Amphipods in the Genus Stygobromus Dwelling in Different Subterranean Habitats

Abstract The amphipod genus Stygobromus occurs in a variety of subterranean habitats in North America, including caves, phreatic (groundwater) lakes, and superficial subterranean habitats (seeps and epikarst). The habitats share the absence of light but differ in other features, such as pore size of the habitat, available food, and degree of seasonality. Measurements of body size, antennal size, and antennal segment number of type specimens were compared for 56 species occurring in the eastern United States. Except for differences in body size, differences among species in the four different habitats were not significant. Body size was related to relative pore size of the habitat, e.g., epikarst, with the smallest spaces, had the smallest species. However, in all habitats, there was one very large species (> 15mm); these enigmatic species apparently occupy a distinct ecological niche, perhaps being more predatory. Differences in relative antennal size showed no significant differences among habitats, and differences in number of antennal segments were marginally significant (P  =  0.06) among habitat types and not in the predicted pattern. Differences among habitats in seasonality and available food seemed to be a minor part of the selective environment; absence of light seemed to be a major part of the selective environment.

Dynamics of Epikarst Communities: Microgeographic Pattern and Environmental Determinants of Epikarst Copepods in Organ Cave, West Virginia

Abstract The copepod community occurring in the uppermost part of karst was investigated by collecting animals from 13 ceiling drips in Organ Cave, West Virginia, over a 30 d period. A total of 444 copepods belonging to six genera and ten species were found. There was considerable heterogeneity, both spatially and temporally. Among physical parameters (oxygen, drip rate, conductivity, temperature, pH, ceiling thickness and redox), overall abundance was strongly influenced by drip rate. Community composition, analyzed by Canonical Correspondence Analysis, was correlated with drip rate, oxygen and ceiling thickness. Community similarity, as measured by Jaccard index, declined with geographic distance, but after a distance of several hundred meters, the average similarity and range of values increased, as “new” communities appeared. The overall pattern appears to be a relatively fine-scale patchwork of communities at a scale of hundred or so meters. The hotbed of copepod diversity in caves is the epikarst, not the streams.

Galactooligosaccharide supplementation reduces stress-induced gastrointestinal dysfunction and days of cold or flu: a randomized, double-blind, controlled trial in healthy university students

BACKGROUND Acute psychological stress induced by academic exams is associated with dysregulated gastrointestinal and immune function. OBJECTIVE We examined whether supplementation with galactooligosaccharides reduced gastrointestinal dysfunction and the percentage of days with cold or flu in academically stressed undergraduate students. DESIGN In a randomized, double-blind study, subjects (n = 427) received 0, 2.5, or 5.0 g galactooligosaccharides for 8 wk around the time of fall final exams. Levels of stress and cold or flu symptom intensity (SI; 0 = not experiencing to 3 = severe) were recorded daily. The SI from 9 cold or flu symptoms was summed with 1 d of cold or flu defined as a sum >6. The Gastrointestinal Symptom Response Scale was completed weekly. RESULTS Stress was positively related to diarrhea, indigestion, and reflux syndromes and with abdominal pain, average daily cold or flu SI score, and the percentage of days with cold or flu. Gastrointestinal symptom scores for diarrhea (P = 0.0298), constipation (P = 0.0342), abdominal pain (P = 0.0058), and indigestion (P = 0.0003) syndromes were lower after galactooligosaccharide supplementation. The cold or flu SI score was affected by galactooligosaccharides and stress (P < 0.0001); 2.5 g was associated with a lower SI score across all levels of stress, but 5.0 g was protective only at lower levels of stress. The percentage of days with cold or flu was associated with galactooligosaccharides within different body mass index categories (P = 0.0002), wherein a 40% reduction in the percentage of days with cold or flu was observed in normal-weight individuals with 5.0 g galactooligosaccharides. This effect was not observed in overweight or obese individuals. CONCLUSIONS Acute psychological stress was directly related to symptoms of gastrointestinal dysfunction and cold or flu. Galactooligosaccharide supplementation reduced these symptoms and the number of days with cold or flu. This trial was registered at clinicaltrials.gov as NCT01137760.

Social behavior drives the dynamics of respiratory disease in threatened tortoises

Since the early 1990s, morbidity and mortality in tortoise populations have been associated with a transmissible, mycoplasmal upper respiratory tract disease (URTD). Although the etiology, transmission, and diagnosis of URTD have been extensively studied, little is known about the dynamics of disease transmission in free-ranging tortoise populations. To understand the transmission dynamics of Mycoplasma agassizii, the primary etiological agent of URTD in wild tortoise populations, we studied 11 populations of free-ranging gopher tortoises (Gopherus polyphemus; n = 1667 individuals) over five years and determined their exposure to the pathogen by serology, by clinical signs, and by detection of the pathogen in nasal lavages. Adults tortoises (n = 759) were 11 times more likely to be seropositive than immature animals (n = 242) (odds ratio = 10.6, 95% CI = 5.7-20, P < 0.0001). Nasal discharge was observed in only 1.4% (4/296) of immature tortoises as compared with 8.6% (120/1399) of adult tortoises. Nasal lavages from all juvenile tortoises (n = 283) were negative by PCR for mycoplasmal pathogens associated with URTD. We tested for spatial segregation among tortoise burrows by size class and found no consistent evidence of clustering of either juveniles or adults. We suggest that the social behavior of tortoises plays a critical role in the spread of URTD in wild populations, with immature tortoises having minimal interactions with adult tortoises, thereby limiting their exposure to the pathogen. These findings may have broader implications for modeling horizontally transmitted diseases in other species with limited parental care and emphasize the importance of incorporating animal behavior parameters into disease transmission studies to better characterize the host-pathogen dynamics.