Tradeoffs between courtship, fighting, and antipredatory behavior by a lizard, Eumeces laticeps

Male fitness in many species depends strongly on social behaviors needed to obtain fertilizations and prevent loss of fertilizations to other males, but courtship, copulation, and fighting may incur increased risk of predation. When demands for reproductive and antipredatory behaviors conflict, fitness may be maximized by accepting some degree of risk to enhance reproductive success. To examine such tradeoffs, I introduced tethered conspecific males or females to adult male broad-headed skinks, Eumeces laticeps, in the field and observed how close they allowed a simulated predator (me) to approach before fleeing, or their latency to approach an introduced female located at different distances from the predator. When conspecific males were introduced, isolated and mate-guarding males initiated agonistic behaviors and permitted closer approach than control males, and mate-guarding males permitted closer approach than isolated males. When females were introduced, both isolated and mate-guarding males courted the introduced females and isolated males permitted closer approach than did mate-guarding males. These results for introduced males and females suggest that increasing risk was accepted when reproductive benefits were greater. Latency for isolated males to approach a conspecific female was greater when the predator was closer to the female, further suggesting sensitivity to predation risk during a reproductive opportunity. Relationships between reproductive and antipredatory behaviors have been studied much less than those between feeding and antipredatory behaviors, but this study indicates that animals balance increased risk of predation with the opportunity to perform several reproductively important behaviors. Received: 5 March 1999 / Received in revised form: 15 July 1999 / Accepted: 25 July 1999     

Relatedness and avoidance of inbreeding in the lizard, Tiliqua rugosa

Two potential mechanisms for reducing the level of inbreeding, sex-biased dispersal and kin avoidance, were examined in the Australian sleepy lizard, Tiliqua rugosa. The home range centres, and the genotypes at four polymorphic microsatellite DNA loci were determined for adult lizards in a 70-ha study area near Mount Mary, South Australia. From estimates of genetic relatedness, females were as closely related to other females as they were to males, both within the whole study area, and within home ranges. Similarly, males were as closely related to other males as they were to females. This suggests that dispersal in the population is not sex-biased. Sleepy lizards form monogamous pairs during the spring. Partners were less closely related to each other than to other potential partners in the home range area. This suggests active choice of unrelated partners. The mechanism for recognising related from unrelated individuals is unknown, but the behaviour could reduce inbreeding. Received: 7 November 1998 / Accepted: 30 May 1999     

Enhancing perspectives on lake impairments using satellite observations: A case study on High Rock Lake,North Carolina

Stakeholders developing water quality improvement plans for lakes and reservoirs are challenged by the sparsity of in-situ data and the uncertainty ingrained in management decisions. This study explores how satellite images can fill gaps in water quality databases and provide more holistic assessments of impairments. The study site is an impaired water body that is serving as a pilot for improving state-wide nutrient management planning processes. An existing in-situ database was used to calibrate semi-analytical models that relate satellite reflectance values to turbidity and total suspended solids (TSS). Landsat-7 images from 1999 to 2020 that overpass High Rock Lake, North Carolina were downloaded and processed, providing 42 turbidity and 39 TSS satellite and in-situ match-ups for model calibration and validation. Model r-squared values for the fitted turbidity and TSS models are 0.72 and 0.74, and the mean absolute errors are 14.6 NTU and 3.2 mg/L. The satellite estimates were compared to the in-situ data and simulated TSS values produced by a calibrated hydrologic-hydrodynamic model. The process-based model is considered less accurate than the satellite model based on statistical performance metrics. Comparisons between data sources are illustrated with time series plots, frequency curves, and aggregate decision metrics to highlight the dependence of lake impairment assessments on the spatial and temporal frequency of available data and model accuracy.     

Detection of coastal mud odors by loggerhead sea turtles: a possible mechanism for sensing nearby land

For sea turtles, an ability to detect land masses from a considerable distance away, and to distinguish coastal areas from the open sea, might be adaptive. The loggerhead turtle, Caretta caretta, can detect airborne odorants associated with food. To investigate whether sea turtles can also detect odors associated with land, we studied the responses of juvenile loggerheads to odors from coastal mud. Turtles were tested in a water-filled arena in which odorants could be introduced to the air above the water surface. Turtles exposed to air that had passed over a cup containing mud spent more time with their noses out of the water than did control turtles exposed to air that had passed over a cup containing distilled water. The results demonstrate for the first time that loggerheads can detect airborne odorants associated with land, an ability that might play a role in foraging, navigation, or both.     

Biological impacts of ocean acidification: a postgraduate perspective on research priorities

Research into the effects of ocean acidification (OA) on marine organisms has greatly increased during the past decade, as realization of the potential dramatic impacts has grown. Studies have revealed the multifarious responses of organisms to OA conditions, indicating a high level of intra- and interspecific variation in species’ ability to accommodate these alterations. If we are to provide policy makers with sound, scientific input regarding the expected consequences of OA, we need a broader understanding of these predicted changes. As a group of 20 multi-disciplinary postgraduate students from around the globe, with a study focus on OA, we are a strong representation of ‘next generation’ scientists in this field. In this unique cumulative paper, we review knowledge gaps in terms of assessing the biological impacts of OA, outlining directions for future research.     

Differential responses in American (<Emphasis Type="Italic">Castanea dentata</Emphasis> Marshall) and Chinese (<Emphasis Type="Italic">C. mollissima</Emphasis> Blume) chestnut (Falales: Fagaceae) to foliar application of jasmonic acid

Summary.  Tannins are plant defense compounds that exhibit antibiotic (e.g. toxic) and antixenotic (e.g. repellent) effects against an array of plant pests. They are broadly divided into two major groups, hydrolysable tannins (gallotannins and ellagitannins) and proanthocyanidins, each with an undetermined number of compounds. We investigated constitutive levels of hydrolysable tannins and proanthocyanidins in the leaves and stems of American (Castanea dentata Marshall) (Fagales: Fagaceae) and Chinese (C. mollissima Blume) chestnut. American chestnut contained more proanthocyanidins in leaves and stems than Chinese chestnut, but Chinese chestnut contained more foliar hydrolysable tannins. Regardless of these differences, gypsy moth (Lymantria dispar L, Lepidoptera: Lymantriidae) performance did not differ when fed American and Chinese chestnuts. We also investigated the effects of jasmonic acid (JA) treatment on differential tannin induction in American and Chinese chestnut leaves and stems. JA treatment increased proanthocyanidins in American chestnut stems and hydrolysable tannins in both tissue types of American chestnut, but did not influence tannin concentrations in Chinese chestnut leaves or stems. HPLC-ESI-MS analysis of pooled samples suggested that hydrolysable tannins in each tissue were qualitatively comprised primarily of ellagitannins, and JA generally increased the number of hydrolysable tannins that could be detected by ESI-MS. Third, we investigated the performance of gypsy moths on JA treated and untreated American and Chinese chestnut. Caterpillar relative growth was not influenced by JA treatment on Chinese chestnut, but decreased in response to JA application on American chestnut. Our results indicate that JA-dependent defenses differ between these chestnut species. This study improves our understanding of ecologically important differences in tannin induction and herbivore susceptibility in Castanea, and has important implications in efforts for American chestnut restoration and commercial chestnut production.     

Agricultural drainage ditches mitigate phosphorus loads as a function of hydrological variability

Phosphorus (P) loading from nonpoint sources, such as agricultural landscapes, contributes to downstream aquatic ecosystem degradation. Specifically, within the Mississippi watershed, enriched runoff contributions have far-reaching consequences for coastal water eutrophication and Gulf of Mexico hypoxia. Through storm events, the P mitigation capacity of agricultural drainage ditches under no-till cotton was determined for natural and variable rainfall conditions in north Mississippi. Over 2 yr, two experimental ditches were sampled monthly for total inorganic P concentrations in baseflow and on an event-driven basis for stormflows. Phosphorus concentrations, Manning's equations with a range of roughness coefficients for changes in vegetative densities within the ditches, and discharge volumes from Natural Resources Conservation Service dimensionless hydrographs combined to determine ranges in maximum and outflow storm P loads from the farms. Baseflow regressions and percentage reductions with P concentrations illustrated that the ditches alternated between being a sink and source for dissolved inorganic P and particulate P concentrations throughout the year. Storm event loads resulted in 5.5% of the annual applied fertilizer to be transported into the drainage ditches. The ditches annually reduced 43.92 +/- 3.12% of the maximum inorganic effluent P load before receiving waters. Agricultural drainage ditches exhibited a fair potential for P mitigation and thus warrant future work on controlled drainage to improve mitigation capacity.     

Long-term increases in surface water dissolved organic carbon: observations, possible causes and environmental impacts

Dissolved organic carbon (DOC) concentrations in 22 UK upland waters have increased by an average of 91% during the last 15 years. Increases have also occurred elsewhere in the UK, northern Europe and North America. A range of potential drivers of these trends are considered, including temperature, rainfall, acid deposition, land-use, nitrogen and CO2 enrichment. From examination of recent environmental changes, spatial patterns in observed trends, and analysis of time series, it is suggested that DOC may be increasing in response to a combination of declining acid deposition and rising temperatures; however it is difficult to isolate mechanisms based on monitoring data alone. Long-term DOC increases may have wide-ranging impacts on freshwater biota, drinking water quality, coastal marine ecosystems and upland carbon balances. Full understanding of the significance of these increases requires further knowledge of the extent of natural long-term variability, and of the natural "reference" state of these systems.