A conceptual framework for organismal biology: linking theories, models, and data

Lower-level predictors and behavioral correlates of maximal aerobic capacity and sprint speed among individual lizards

The standard paradigm of organismal biology views lower-level traits (e.g. aspects of physiology) as determining organismal performance ability (e.g. maximal sprint speed), which in turn constrains behavior (e.g. social interactions). However, few studies have simultaneously examined all three levels of organization. We used focal observations to record movement behaviors and push-up displays in the field for adult male Sceloporus occidentalis lizards during the breeding season. We then captured animals, measured aspects of their physiology, morphology and performance, and counted ectoparasites and endoparasites as potential predictors of sprint speed and maximal oxygen consumption (V̇O2,max). Field behaviors were statistically repeatable, but not strongly so. Sprint speed and V̇O2,max were repeatable using residuals from regressions on body mass (speed: r=0.70; V̇O2,max: r=0.88). Both calf [standardized partial regression (path) coefficient B=0.53] and thigh [B=-0.37] muscle mass (as residuals from regressions on body mass) were significant predictors of sprint speed; hemoglobin concentration (B=0.42) was a predictor of V̇O2,max. In turn, V̇O2,max predicted the maximum number of four-legged push-ups per bout (B=0.39). In path analysis, log likelihood ratio tests indicated no direct paths from lower-level traits to behavior, supporting the idea that morphology, in the broad sense, only affects behavior indirectly through measures of performance. Our results show that inter-individual variation in field behaviors can be related to performance ability, which in turn reflect differences in morphology and physiology, although not parasite load. Given the low repeatability of field behaviors, some of the relationships between behavior and performance may be stronger than suggested by our results.

Immune Defense in Hypoxic Waters: Impacts of CO2 Acidification

AbstractPeriodic episodes of low oxygen (hypoxia) and elevated CO₂ (hypercapnia) accompanied by low pH occur naturally in estuarine environments. Under the influence of climate change, the geographic range and intensity of hypoxia and hypercapnic hypoxia are predicted to increase, potentially jeopardizing the survival of economically and ecologically important organisms that use estuaries as habitat and nursery grounds. In this review we synthesize data from published studies that evaluate the impact of hypoxia and hypercapnic hypoxia on the ability of crustaceans and bivalve molluscs to defend themselves against potential microbial pathogens. Available data indicate that hypoxia generally has suppressive effects on host immunity against bacterial pathogens as measured by in vitro and in vivo assays. Few studies have documented the effects of hypercapnic hypoxia on crustaceans or bivalve immune defense, with a range of outcomes suggesting that added CO₂ might have additive, negative, or no interactions with the effects of hypoxia alone. This synthesis points to the need for more partial pressure of O₂ × low pH factorial design experiments and recommends the development of new host∶pathogen challenge models incorporating natural transmission of a wide range of viruses, bacteria, and parasites, along with novel in vivo tracking systems that better quantify how pathogens interact with their hosts in real time under laboratory and field conditions.

Entropy, Statistical Evidence, and Scientific Inference: Evidence Functions in Theory and Applications

Scope and Goals of the Special Issue: There is a growing realization that despite being the essential tool of modern data-based scientific discovery and model testing, statistics has major problems [...].

Trade-Offs (and Constraints) in Organismal Biology

AbstractTrade-offs and constraints are inherent to life, and studies of these phenomena play a central role in both organismal and evolutionary biology. Trade-offs can be defined, categorized, and studied in at least six, not mutually exclusive, ways. (1) Allocation constraints are caused by a limited resource (e.g., energy, time, space, essential nutrients), such that increasing allocation to one component necessarily requires a decrease in another (if only two components are involved, this is referred to as the Y-model, e.g., energy devoted to size versus number of offspring). (2) Functional conflicts occur when features that enhance performance of one task decrease performance of another (e.g., relative lengths of in-levers and out-levers, force-velocity trade-offs related to muscle fiber type composition). (3) Shared biochemical pathways, often involving integrator molecules (e.g., hormones, neurotransmitters, transcription factors), can simultaneously affect multiple traits, with some effects being beneficial for one or more components of Darwinian fitness (e.g., survival, age at first reproduction, fecundity) and others detrimental. (4) Antagonistic pleiotropy describes genetic variants that increase one component of fitness (or a lower-level trait) while simultaneously decreasing another. (5) Ecological circumstances (or selective regime) may impose trade-offs, such as when foraging behavior increases energy availability yet also decreases survival. (6) Sexual selection may lead to the elaboration of (usually male) secondary sexual characters that improve mating success but handicap survival and/or impose energetic costs that reduce other fitness components. Empirical studies of trade-offs often search for negative correlations between two traits that are the expected outcomes of the trade-offs, but this will generally be inadequate if more than two traits are involved and especially for complex physiological networks of interacting traits. Moreover, trade-offs often occur only in populations that are experiencing harsh environmental conditions or energetic challenges at the extremes of phenotypic distributions, such as among individuals or species that have exceptional athletic abilities. Trade-offs may be (partially) circumvented through various compensatory mechanisms, depending on the timescale involved, ranging from acute to evolutionary. Going forward, a pluralistic view of trade-offs and constraints, combined with integrative analyses that cross levels of biological organization and traditional boundaries among disciplines, will enhance the study of evolutionary organismal biology.

Sit-to-stand activity to improve mobility in older people: A scoping review

AIMS AND OBJECTIVES

To identify the current state of knowledge about the use of the sit-to-stand intervention with older people and to identify implications for further research.

BACKGROUND

Many older people experience mobility challenges which can negatively affect their well-being. Physical activities are vital to improving or maintaining mobility. Although there is evidence that mobility challenged older people benefit from the sit-to-stand intervention, there is a need to systematically examine the state of knowledge about this intervention.

DESIGN

Scoping review using Arksey and O'Malley's methodological framework.

METHODS

A systematic search of three databases was completed. Abstracts were evaluated for relevance using predetermined inclusion criteria. Studies that met the inclusion criteria had data extracted and were appraised for internal and external validity. Narrative synthesis was based on methods described by Popay and colleagues.

RESULTS

Of 3,041 papers, six studies met the inclusion criteria. Publications provided a range of sit-to-stand interventions with durations varying from four weeks to six months. The frequency of each intervention fluctuated from three to seven times/week with a duration of 15-45 min. Different professionals prompted the activity. Three themes were identified the following: (a) sit-to-stand activity as an intervention; (b) generalisability of findings; and (c) sustainability.

CONCLUSIONS

Most of the studies reviewed indicated improvements in performance of the sit-to-stand activity and in motor function. However, issues with studies rigour do not allow us to make generalisations. Further research is needed to confirm the effectiveness of the intervention.

IMPLICATIONS FOR PRACTICE

Healthcare providers are expected to offer evidence-based patient care. This review details current knowledge about the sit-to-stand intervention with older people.

Pleiotropic jaw morphology links the evolution of mechanical modularity and functional feeding convergence in Lake Malawi cichlids

Complexity in how mechanistic variation translates into ecological novelty could be critical to organismal diversification. For instance, when multiple distinct morphologies can generate the same mechanical or functional phenotype, this could mitigate trade-offs and/or provide alternative ways to meet the same ecological challenge. To investigate how this type of complexity shapes diversity in a classic adaptive radiation, we tested several evolutionary consequences of the anterior jaw four-bar linkage for Lake Malawi cichlid trophic diversification. Using a novel phylogenetic framework, we demonstrated that different mechanical outputs of the same four jaw elements are evolutionarily associated with both jaw protrusion distance and jaw protrusion angle. However, these two functional aspects of jaw protrusion have evolved independently. Additionally, although four-bar morphology showed little evidence for attraction to optima, there was substantial evidence of adaptive peaks for emergent four-bar linkage mechanics and jaw protrusion abilities among Malawi feeding guilds. Finally, we highlighted a clear case of two cichlid species that have -independently evolved to graze algae in less than 2 Myr and have converged on similar jaw protrusion abilities as well as four-bar linkage mechanics, but have evolved these similarities via non-convergent four-bar morphologies.

A conceptual framework for homeostasis: development and validation

We have developed and validated a conceptual framework for understanding and teaching organismal homeostasis at the undergraduate level. The resulting homeostasis conceptual framework details critical components and constituent ideas underlying the concept of homeostasis. It has been validated by a broad range of physiology faculty members from community colleges, primarily undergraduate institutions, research universities, and medical schools. In online surveys, faculty members confirmed the relevance of each item in the framework for undergraduate physiology and rated the importance and difficulty of each. The homeostasis conceptual framework was constructed as a guide for teaching and learning of this critical core concept in physiology, and it also paves the way for the development of a concept inventory for homeostasis.

Alternatives to antibiotics in animal agriculture: an ecoimmunological view

Ecological immunology (or ecoimmunology) is a new discipline in animal health and immunology that extends immunologists’ views into a natural context where animals and humans have co-evolved. Antibiotic resistance and tolerance (ART) in bacteria are manifested in antibiosis-surviving subsets of resisters and persisters. ART has emerged though natural evolutionary consequences enriched by human nosocomial and agricultural practices, in particular, wide use of antibiotics that overwhelms other ecological and immunological interactions. Most previous reviews of antibiotic resistance focus on resisters but overlook persisters, although both are fundamental to bacteria survival through antibiosis. Here, we discuss resisters and persisters together to contrast the distinct ecological responses of persisters during antibiotic stress and propose different regimens to eradicate persisters. Our intention is not only to provide an ecoimmunological interpretation, but also to use an ecoimmunological system to categorize available alternatives and promote the discovery of prospective approaches to relieve ART problems within the general scope of improving animal health. Thus, we will categorize available alternatives to antibiotics and envision applications of ecoimmunological tenets to promote related studies in animal production.