Independent age estimates resolve the controversy of ancient human footprints at White Sands.

Human footprints at White Sands National Park, New Mexico, USA, reportedly date to between ~23,000 and 21,000 years ago according to radiocarbon dating of seeds from the aquatic plant Ruppia cirrhosa. These ages remain controversial because of potential old carbon reservoir effects that could compromise their accuracy. We present new calibrated 14C ages of terrestrial pollen collected from the same stratigraphic horizons as those of the Ruppia seeds, along with optically stimulated luminescence ages of sediments from within the human footprint-bearing sequence, to evaluate the veracity of the seed ages. The results show that the chronologic framework originally established for the White Sands footprints is robust and reaffirm that humans were present in North America during the Last Glacial Maximum.

Land management explains major trends in forest structure and composition over the last millennium in California's Klamath Mountains.

SignificanceWe provide the first assessment of aboveground live tree biomass in a mixed conifer forest over the late Holocene. The biomass record, coupled with local Native oral history and fire scar records, shows that Native burning practices, along with a natural lightning-based fire regime, promoted long-term stability of the forest structure and composition for at least 1 millennium in a California forest. This record demonstrates that climate alone cannot account for observed forest conditions. Instead, forests were also shaped by a regime of frequent fire, including intentional ignitions by Native people. This work suggests a large-scale intervention could be required to achieve the historical conditions that supported forest resiliency and reflected Indigenous influence.

Physico-chemical properties of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) diazonium ion: a theoretical investigation.

We have explored the physico-chemical properties of NNK diazonium ion to gain insight into its shape, bonding, charge distribution, and ro-vibrational features. This information is essential if the chemical reactivity and physical properties of this important intermediate are to be understood. NNK diazonium ion is a well-known alkylating agent. Its enzymatic production, its reaction with DNA, and its role in mutagenesis/carcinogenesis have all received significant experimental study. Computational work on the ion, however, is lacking. The species is sufficiently small such that its properties may be probed using sophisticated model chemistries. We present the first in silico investigation of NNK diazonium ion. Kohn-Sham density functional theory (B3LYP/6-311G**) and coupled cluster theory (CCSD/6-31G*) were deployed to obtain energies, geometries, electrostatic potential surfaces, molecular orbitals, and vibrational analyses for several energy-minimized structures. To provide insight into the motion of NNK diazonium ion (NNKDI) in solution, molecular dynamics simulations on the solvated intermediate were undertaken. To explore the initial reactivity of this important electrophile, local Fukui indices and natural population analysis charges were predicted. Analogous ab initio work on propane diazonium ion was also performed. Our vibrational analyses suggest a relatively weak carbon-nitrogen bond and a robust nitrogen-nitrogen interaction. Our condensed Fukui indices show that the terminal nitrogen is a site of significant electrophilicity while our electrostatic predictions yield high values near the formally charged nitrogen and its α carbon.

First record of Nesomesochorinae (Hymenoptera: Ichneumonidae) from America north of Mexico with descriptions of two new species of Nonnus Cresson.

The subfamily Nesomesochorinae is recorded for the first time from America north of Mexico. Two new species of Nonnus (Hymenoptera: Ichneumonidae: Nesomesochorinae) are described, both from Arizona, USA and Mexico. Diagnostic characters and figures are provided to distinguish these two new species from congeners in North and Central America.

Stenarella domator (Poda) [Hymenoptera: Ichneumonidae], a newly introduced species to the Nearctic, and a summary of adventive Nearctic species of Ichneumonidae.

The western Palaearctic ichneumonid Stenarella domator (Poda) is newly recorded for the Nearctic. Photographs and a new key to the genera of Nearctic Osprynchotina (Cryptinae: Cryptini) are provided. Like other species in the Osprynchotina, S. domator is an ectoparasitoid of aculeate Hymenoptera which use mud/earth in their nests. The 25 species of adventive Nearctic ichneumonids are reviewed, and the implications of their biologies for Nearctic host ranges are discussed.

The mature larva of Poemenia albipes Cresson (Hymenoptera: Ichneumonidae, Poemeniinae) and a review of the biology of Nearctic Poemenia.

The mature larva of Poemenia albipes is figured and described, providing the first knowledge of the larval morphology of this genus. Poemenia is considered to be an ectoparasitoid on the basis of this information. The implications for the larval morphology of the Poemeniinae are discussed. The biology of Nearctic Poemenia is reviewed, with the conclusion that the genus is parasitic upon small xylophilous Apoidea that either make their tunnels or utilize those made by other insects.

Examining the effects of chronic, lake-wide elevated temperatures on behavioural expression in largemouth bass, Micropterus salmoides.

Many behaviours have differential fitness consequences across thermal and ecological contexts, indicating that both ecological shifts and warming temperatures induced by climatic change may alter how organisms behave. However, empirical evidence of temperature-driven behavioural selection in natural systems is lacking. We compared behaviours and behavioural syndromes related to activity, exploration, boldness and aggression in populations of largemouth bass (Micropterus salmoides) from ambient lakes to the those from artificially warmed, power plant cooling lakes to investigate changes in behaviours associated with warmer environments. Activity, exploration, boldness and aggression of juvenile largemouth bass were assessed in laboratory conditions using a novel environment assay and a risky situation assay. We found that activity and exploratory behaviours were higher and decreased through first year ontogeny in populations from heated lakes, whereas these behaviours were lower and showed no relationship through ontogeny in populations from ambient lakes. We attribute these differences to the changes in food source availability in heated lakes associated with temperature-driven ecological effects. Bold and aggressive behaviours tended to differ between populations, as did correlations between behaviours, but did not differ between ambient and heated lakes. The findings of this work identify that large ecological changes associated with warming environments, such as food availability, may drive changes in some aspects of behavioural expression in largemouth bass but that other aspects of behavioural expression may be driven by lake-specific factors not related to warming.

Growth and physiological responses in largemouth bass populations to environmental warming: Effects of inhabiting chronically heated environments.

Ectotherms are susceptible to increasing environmental temperatures associated with anthropogenic warming. Supra-optimum temperatures lead to declining aerobic capacity and can increase exposure to lethal temperatures, resulting in reduced performance. Although the capacity of phenotypic plasticity to minimize the effects of temperature on physiological processes is well studied, evidence of generational changes (e.g. transgenerational plasticity and rapid adaptation) in response to environmental warming is limited in natural populations. We investigated metabolism, growth, and thermal tolerance of largemouth bass (Micropterus salmoides) populations inhabiting thermally altered lakes (i.e. power plant cooling lakes) which have year-round elevated temperature regimes and exhibit supra-optimum temperatures on a yearly basis, and compared these traits with those in largemouth bass populations from ambient lakes. Largemouth bass from ambient and heated groups (n = 3 populations per group) were spawned in an ambient, common garden pond environment, then acclimated to either a normal summertime temperature (24 °C) or a supra-optimum temperature (30 °C). Fish from heated populations had significant reductions in the resting metabolic rate at both temperatures and markedly increased growth rates at 30 °C. By comparing pond-raised fish to fish removed directly from heated lakes, we showed that developmental plasticity played little role in establishing the metabolic rate. A lower resting metabolic rate contributed to an increase in the conversion efficiency of food to biomass of largemouth bass from heated lakes, regardless of temperature. Despite inhabiting heated lakes for many decades, neither critical thermal maximum nor minimum were altered in heated populations when raised in a common garden environment. These results suggest that largemouth bass can lessen sub-lethal effects of warming by altering physiological processes to reduce the impact of warming on aerobic scope and that these changes are generationally transient, but changes in maximum thermal tolerance in response to warming is limited to phenotypic plasticity.

Palaeoenvironmental, epigraphic and archaeological evidence of total warfare among the Classic Maya.

Despite over a century of archaeological research, the nature and broader consequences of Maya warfare remain poorly understood. Classic period (250-950 CE) Maya warfare has largely been viewed as ritualized and limited in scope1-6. Evidence of violent warfare in the Terminal Classic period (800-950 CE) is interpreted as an escalation of military tactics that played a role in the socio-economic collapse of the Classic Maya civilization7,8. The implications of specific textual references to war events (war statements) remain unknown, however, and the paucity of field data precludes our ability to test collapse theories tied to warfare. Here we connect a massive fire event to an attack described with a Classic period war statement. Multiple lines of evidence show that a large fire occurred across the ancient city of Witzna, coincident with an epigraphic account describing an attack and burning of Witzna in 697 CE. Following this event, evidence shows a dramatic decline in human activity, indicating extensive negative impacts on the local population. These findings provide insight into strategies and broader societal impacts of Classic period warfare, clarify the war statement's meaning and show that the Maya engaged in tactics akin to total warfare earlier and more frequently than previously thought.

Effects of maternal cortisol treatment on offspring size, responses to stress, and anxiety-related behavior in wild largemouth bass (Micropterus salmoides).

Cortisol, the main glucocorticoid stress hormone in teleost fish, is of interest as a mediator of maternal stress on offspring characteristics because it plays an organizational role during early development. The present study tested the hypothesis that maternal exposure to cortisol treatment prior to spawn affects offspring phenotype using wild largemouth bass (Micropterus salmoides). Baseline and stress-induced cortisol concentrations, body size (i.e. length and mass), and behavior (i.e. anxiety, exploration, boldness, and aggression) were assessed at different offspring life-stages and compared between offspring of control and cortisol-treated females. Cortisol administration did not affect spawning success or timing, nor were whole-body cortisol concentrations different between embryos from cortisol-treated and control females. However, maternal cortisol treatment had significant effects on offspring stress responsiveness, mass, and behavior. Compared to offspring of control females, offspring of cortisol-treated females exhibited larger mass right after hatch, and young-of-the-year mounted an attenuated cortisol response to an acute stressor, and exhibited less thigmotaxic anxiety, exploratory behavior, boldness and aggression. Thus, offspring phenotype was affected by elevated maternal cortisol levels despite the absence of a significant increase in embryo cortisol concentrations, suggesting that a mechanism other than the direct deposition of cortisol into eggs mediates effects on offspring. The results of the present raise questions about the mechanisms through which maternal stress influences offspring behavior and physiology, as well as the impacts of such phenotypic changes on offspring fitness.

Invasive planktivores as mediators of organic matter exchanges within and across ecosystems.

Bighead carp (Hypophthalmichthys nobilis) are an invasive planktivore that can greatly deplete planktonic resources. Due to the inefficient conversion of food into fish tissue, large portions of consumed materials are egested and shunted to benthic habitats. We explored how bighead carp alter pools of organic matter between planktonic and benthic habitats, and across ecosystem boundaries. Here, we report evidence from a manipulative experiment demonstrating that bighead carp greatly reapportion pools of organic matter from planktonic to benthic habitats to such a degree that additional effects propagated across ecological boundaries into terrestrial ecosystems. Strong direct consumption by bighead carp reduced filamentous algae, biomass and production of zooplankton, and production of a native planktivorous fish within planktonic habitats. Reduced herbivory indirectly increased phytoplankton (chlorophyll a). Direct consumption of organic matter by bighead carp supported high carp production and concomitant losses of materials due to egestion. Perhaps in response to organic matter subsidies provided by fish egestion, ponds having bighead carp had higher standing crop biomass of Chironomidae larvae, as well as cross-boundary fluxes of their adult life stage. In contrast, we detected reduced cross-boundary fluxes of adult Chaoboridae midges in ponds having bighead carp. Consideration of bighead carp as mediators of organic matter exchanges provides a clearer framework for predicting the direct and extended impacts of these invasive planktivores in freshwater ecosystems. The perception of bighead carp must evolve beyond competitors for planktonic resources, to mediators and processors of nutrients and energy within and across ecosystems.

Size-Dependent Consequences of Exogenous Cortisol Manipulation on Overwinter Survival and Condition of Largemouth Bass.

Little is known about the size-dependent consequences of stressors on wild animals, which is particularly relevant during winter where size-specific trends in survival are common. Here, exogenous cortisol manipulation was used to investigate the effect of a physiological challenge on overwinter mortality and spring condition of largemouth bass (Micropterus salmoides) across a range of body sizes. Fish were wild-caught in the fall, assigned into either control or cortisol manipulated treatments, and held in replicated experimental ponds. For bass that survived the winter, length, mass, and health metrics (e.g., gonadosomatic index [GSI], hepatosomatic index [HSI], and water content) were determined in the spring. Winter survival was marginally lower for cortisol treated bass; however, there was no influence of initial length, mass, or condition on overwinter survival. When bass were grouped by size, survival was significantly higher for bass 300-350 mm in length compared to those <200 mm. The treatment did not strongly influence spring health metrics, suggesting that largemouth bass that survived the winter were able to recover from the effects of the cortisol elevation. Initial size and sex were linked to some spring health metrics, with large females having the highest GSI and HSI scores. Overall, results from this study do not support the notion that there are size-dependent responses to cortisol manipulation in a teleost fish. Rather, this type of physiological challenge may modulate the natural rates of winter mortality that are primarily driven by starvation and predation, independent of body size, in subadult and adult largemouth bass.

Does prey community composition affect the way different behavioral types interact with their environment?

We examined how different exploratory behavioral types of largemouth bass responded to differing prey communities by determining effects on growth, survival and diet in experimental ponds. We found evidence that non-explorer largemouth bass target young-of-year bluegill early on in life, but bluegill were not an important diet item by late summer. The presence of young-of-year bluegill as prey does appear to affect the foraging strategy of the two exploring types differently. In the absence of small bluegill, both behavioral types feed primarily on benthic invertebrates and zooplankton. When small bluegill were present, we saw a shift away from zooplankton as prey for largemouth bass. However, that shift was toward more benthic invertebrates for non-exploring behavioral types and toward terrestrial insects for exploring behavioral types. Thus, it appears that prey community composition can have important effects on the way in which different behavioral types interact with their environment.

Is winter worse for stressed fish? The consequences of exogenous cortisol manipulation on over-winter survival and condition of juvenile largemouth bass.

Over-winter mortality is an important selective force for warm-water fish (e.g., centrarchids) that live in temperate habitats. Inherent challenges faced by fish during winter may be compounded by additional stressors that activate the hypothalamic-pituitary-interrenal axis, either before or during winter, leading to negative sub-lethal impacts on fish health and condition, and possibly reducing chance of survival. We used experimental cortisol manipulation to test the hypothesis that juvenile largemouth bass (Micropterus salmoides) exposed to semi-chronic elevation in cortisol prior to winter would experience higher levels of over-winter mortality, physiological alterations and impaired immune status relative to control and sham-treated bass. Over-winter survival in experimental ponds was high, averaging 83%, and did not differ among treatment groups. Over the study period, bass exhibited an average increase in mass of 19.4%, as well as a slight increase in Fulton's condition factor, but neither measure differed among groups. Hepatosomatic index in cortisol-treated bass was 23% lower than in control fish, suggesting lower energy status, but white muscle lipid content was similar across all groups. Lastly, there was no difference in spleen somatic index or parasite load among treatment groups, indicating no long-term immune impairment related to our cortisol manipulation. The current study adds to a growing body of literature on glucocorticoid manipulations where field-based findings are not consistent with laboratory-based conceptual understanding of multiple stressors. This suggests that field conditions may provide fish with opportunities to mitigate negative effects of some stressors.

Response of largemouth bass (Micropterus salmoides) from different thermal environments to increased water temperature.

Due to concerns of global climate change, additional research is needed to quantify the thermal tolerance of species, and how organisms are able to adapt to changes in thermal regime. We quantified the thermal tolerance and thermal stress response of a temperate sportfish from two different thermal environments. One group of largemouth bass (Micropterus salmoides) inhabited thermally enhanced reservoirs (used for power plant cooling), with water temperatures typically 2-5°C warmer than nearby reservoirs. We tested fish for chronic thermal maxima and reaction to an 8°C heat shock using three common physiological indices of stress. We observed no evidence of differences between groups in thermal maxima. We observed no differences in thermal maxima between fish from artificially warmed and natural systems. Our results disagree with research, suggesting differences due to adaptation to different thermal environments. We speculate that behavioral modifications, lack of adequate time for genetic divergence, or the robust genetic plasticity of largemouth bass explain the lack of difference between treatment groups.

Biology, early stages and description of a new species of Adelognathus Holmgren (Hymenoptera: Ichneumonidae: Adelognathinae).

Adelognathus leucotrochi Shaw & Wahl sp. nov. is described from Britain where it is a univoltine slightly gregarious koinobiont ectoparasitoid of late stage larvae of the tenthredinid sawfly Nematus leucotrochus Hartig feeding on Ribes uva-crispa. Defensive reactions by the host to prospecting females are described. The developmental biology of A. leucotrochi is described in detail: the host is only temporarily paralysed by the injection of a venom that has no other effect on the host, and eggs are laid on the host's dorsum without involvement of the ovipositor-that is, the egg issues direct from the genital opening. Prior to oviposition the adult female parasitoid prepares the site by spreading an adhesive substance from her ovipositor. Host-feeding by adult females occurs on haemolymph and sometimes also other tissues obtained at the site of a wound made always by the mandibles, but appears not to be obligatory. It may be concurrent or non-concurrent with oviposition; in the latter case, it may be either destructive or non-destructive. Larval development is very rapid, taking about 70 hr at 18-22ºC, and the host continues to feed for approximately the first half of this period. Five larval instars were detected, and their cephalic sclerites are described and illustrated, as are those of the final instars of a further three species of Adelognathus for comparison. The rather featureless final instar larva is also figured, as is the tough cocoon in which the winter is passed as a prepupa. The biology of some idiobiont Adelognathus species is discussed in comparison with that of A. leucotrochi, and several other instances of eggs not issuing from the ovipositor in non-aculeate ectoparasitoid Hymenoptera, whether koinobionts or idiobionts, are briefly reviewed. It is concluded that this habit seems to arise rather easily when there is direct bodily contact between the adult and the host/prey, as indeed is the case in all carnivorous aculeates that do not practice continuous provisioning. 

Reach-scale land use drives the stress responses of a resident stream fish.

Abstract To date, relatively few studies have tried to determine the practicality of using physiological information to help answer complex ecological questions and assist in conservation actions aimed at improving conditions for fish populations. In this study, the physiological stress responses of fish were evaluated in-stream between agricultural and forested stream reaches to determine whether differences in these responses can be used as tools to evaluate conservation actions. Creek chub Semotilus atromaculatus sampled directly from forested and agricultural stream segments did not show differences in a suite of physiological indicators. When given a thermal challenge in the laboratory, creek chub sampled from cooler forested stream reaches had higher cortisol levels and higher metabolic stress responses to thermal challenge than creek chub collected from warmer and more thermally variable agricultural reaches within the same stream. Despite fish from agricultural and forested stream segments having different primary and secondary stress responses, fish were able to maintain homeostasis of other physiological indicators to thermal challenge. These results demonstrate that local habitat conditions within discrete stream reaches may impact the stress responses of resident fish and provide insight into changes in community structure and the ability of tolerant fish species to persist in agricultural areas.

Acclimation to a low oxygen environment alters the hematology of largemouth bass (Micropterus salmoides).

One of the most severe impacts of urbanization on aquatic systems is the increasing presence of low oxygen environments caused by anthropogenic sources of pollution. As urbanization increases nationally and globally, it is becoming exceedingly important to understand how hypoxia affects aquatic fauna, especially fish species. In an effort to better understand the impacts of prolonged hypoxia on fishes, largemouth bass were held at 3.0 and 9.0 mg L⁻¹ for 50 days, which has previously shown to be temporally sufficient to impart plastic phenotypic changes. Following the holding period, fish from each group were subjected to a low dissolved oxygen (DO) challenge of 2.0 mg L⁻¹ for 6 h, and their physiological and hematological parameters were compared with control fish held for 6 h with no change in DO. There were no differences in the physiological stress responses between the two holding groups; however, the low oxygen holding group had increased hemoglobin and hematocrit levels following the 6-h low oxygen challenge compared with the high oxygen group. These results suggest largemouth bass exposed to chronic low oxygen conditions, either naturally or anthropogenically, may possess a beneficial advantage of increased oxygen uptake capacity during periods of low oxygen.

Physiological disturbances and overwinter mortality of largemouth bass from different latitudes.

Thermal conditions associated with winter can influence the distribution of a species. Because winter severity varies along latitudes, populations of temperate fish located along a latitudinal gradient may display variation in both sublethal and lethal responses to cold stressors. Sublethal physiological disturbances were quantified in age 1 largemouth bass (Micropterus salmoides) from populations originating from Alabama and Illinois but raised in a common environment. Fish were exposed to 6 h of rapid cold shock from 20° to 8°C (controls were held at 20°C) and then sampled for white muscle, whole blood, and plasma. After cold shock, glucose concentrations were elevated in Alabama but not Illinois fish. Sodium was lower and chloride was higher in Alabama largemouth bass, but fish from Illinois had a greater propensity for potassium loss during cold shock. In Illinois ponds, Alabama largemouth bass exhibited lower overwinter survival (adult: 10%; age 0: 22%) than did those from Illinois (adult: 80%; age 0: 82%). Latitudinal variation in physiological responses to cold stressors may therefore influence overwinter survival of largemouth bass and the ability of a fish species to exist over large geographic areas.

Sex-specific consequences of experimental cortisol elevation in pre-reproductive wild largemouth bass.

Experimental implants were used to investigate the effect of elevated cortisol (the primary stress hormone in teleost fish) on energetic and physiological condition prior to reproduction in male and female largemouth bass (Micropterus salmoides). Fish were wild-caught from lakes in Illinois, and held in experimental ponds for the duration of the study. Between 9 and 13 days after cortisol treatment, and immediately prior to the start of the reproductive period, treated and control animals were sampled. Females exhibited lower muscle lipid content, lower liver glycogen content, and higher hepatosomatic indices than males, regardless of treatment. Also, cortisol-treated females had higher hepatosomatic indices and lower final mass than control females, whereas males showed no differences between treatment groups. Finally, cortisol-treated females had higher gonadal cortisol concentrations than control females. In general, we found evidence of reduced energetic stores in female fish relative to male fish, likely due to timing differences in the allocation of resources during reproduction between males and females. Perhaps driven by the difference in energetic reserves, our data further suggest that females are more sensitive than males to elevated cortisol during the period immediately prior to reproduction.