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Doug Glazier

Juniata College, Biology, Faculty Member

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Special research interests in biological scaling, ecology of small mammals and crustaceans, life history evolution, and ecology of freshwater springs

Citations of research can be found at Google Scholar and Researchgate

Teaching interests in ecology, evolution, general biology and mammalogy
Address: Huntingdon, Pennsylvania, United States

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Papers by Doug Glazier

Multiphasic allometry: the reality and significance of ontogenetic shifts in the body-mass scaling of metabolic rate

Academia Biology, Nov 8, 2024

Commonly observed multiphasic ontogenetic scaling of the rate of metabolism with body mass deserv... more Commonly observed multiphasic ontogenetic scaling of the rate of metabolism with body mass deserves increased attention because metabolism fuels all biological processes, including growth and development. Traditionally, developmental biologists have largely overlooked how ontogenetic transitions are powered by metabolic energy. The reality of multiphasic allometry in some species has also been challenged based on statistical grounds. Therefore, this article attempts to provide helpful perspectives about the reality and significance of multiphasic ontogenetic allometry in three ways. First, it is argued that recent statistical criticisms of multiphasic allometry are problematic because they are based on data that were not properly scaled in geometric (log–log) space and/or on results of analyses of covariance that were distorted by unequal sample sizes and/or unequal/nonoverlapping body-size ranges of the different developmental stages analyzed. Second, it is recommended that the existence of nonlinear (multiphasic or curvilinear) allometry should be tested by comparing linear versus curvilinear regression models or body-size scaling slopes (and their 95% confidence intervals) of different developmental stages, each analyzed with separate, statistically independent log–log regression lines. Third, ontogenetic shifts in metabolic scaling are related to other fundamental developmental changes, thus highlighting the significance of multiphasic allometry for understanding organismal development. Ontogenetic metabolic allometry should be given a more central (general) place in the field of developmental biology.

Scaling species interactions: implications for community ecology and biological scaling theory

Academia Biology, Nov 22, 2023

Background: Various biological properties of organisms relate to body size, often in regular quan... more Background: Various biological properties of organisms relate to body size, often in regular quantifiable ways. Traditionally, these biological scaling relationships have been explained in terms of internal physical constraints, but recently external ecological factors have gained increasing attention. A major goal of my review is to expand a currently developing ecological perspective of biological scaling (allometry) to include species (biotic) interactions, with a major emphasis on predation, herbivory, and parasitism. Results: I review evidence for two major kinds of interspecific body-size scaling patterns: (1) negative relationships of predator species richness and body-size range with prey body size and (2) positive relationships of parasite/herbivore species richness and body-size range with host body size. I argue that these patterns can provide new insights into the structure/function of ecological communities (including latitudinal and trophic-level gradients in biotic interactions) and various biological scaling patterns at the organism, population, community, and ecosystem levels. I further argue that exploration of the body-size scaling of other kinds of biotic interactions (e.g., competition, mutualism, commensalism, and amensalism) would also be worthwhile. Conclusion: The major findings of this review provide further foundation for a "mortality theory of ecology" and a comprehensive theory of allometry that embraces both internal physical and external ecological factors, both currently under development. Body-size scaling of biotic interactions has not only important implications for the development of synthetic theory bridging community ecology and biological scaling, but also practical applications for understanding the effects of human exploitation and climate change on living systems.

Scaling species interactions: implications for community ecology and biological scaling theory

Academia Biology, Nov 23, 2023

Background: Various biological properties of organisms relate to body size, often in regular quan... more Background: Various biological properties of organisms relate to body size, often in regular quantifiable ways. Traditionally, these biological scaling relationships have been explained in terms of internal physical constraints, but recently external ecological factors have gained increasing attention. A major goal of my review is to expand a currently developing ecological perspective of biological scaling (allometry) to include species (biotic) interactions, with a major emphasis on predation, herbivory, and parasitism. Results: I review evidence for two major kinds of interspecific body-size scaling patterns: (1) negative relationships of predator species richness and body-size range with prey body size and (2) positive relationships of parasite/herbivore species richness and body-size range with host body size. I argue that these patterns can provide new insights into the structure/function of ecological communities (including latitudinal and trophic-level gradients in biotic interactions) and various biological scaling patterns at the organism, population, community, and ecosystem levels. I further argue that exploration of the body-size scaling of other kinds of biotic interactions (e.g., competition, mutualism, commensalism, and amensalism) would also be worthwhile. Conclusion: The major findings of this review provide further foundation for a “mortality theory of ecology” and a comprehensive theory of allometry that embraces both internal physical and external ecological factors, both currently under development. Body-size scaling of biotic interactions has not only important implications for the development of synthetic theory bridging community ecology and biological scaling, but also practical applications for understanding the effects of human exploitation and climate change on living systems.

Parental care

Genome Size Covaries More Positively with Propagule Size than Adult Size: New Insights into an Old Problem

Biology, 2021

The body size and (or) complexity of organisms is not uniformly related to the amount of genetic ... more The body size and (or) complexity of organisms is not uniformly related to the amount of genetic material (DNA) contained in each of their cell nuclei (‘genome size’). This surprising mismatch between the physical structure of organisms and their underlying genetic information appears to relate to variable accumulation of repetitive DNA sequences, but why this variation has evolved is little understood. Here, I show that genome size correlates more positively with egg size than adult size in crustaceans. I explain this and comparable patterns observed in other kinds of animals and plants as resulting from genome size relating strongly to cell size in most organisms, which should also apply to single-celled eggs and other reproductive propagules with relatively few cells that are pivotal first steps in their lives. However, since body size results from growth in cell size or number or both, it relates to genome size in diverse ways. Relationships between genome size and body size sho...

Clutch Mass, Offspring Mass, and Clutch Size: Body Mass Scaling and Taxonomic and Environmental Variation

Life Histories, 2018

In this chapter, I show how clutch mass, offspring (egg) mass, and clutch size relate to body mas... more In this chapter, I show how clutch mass, offspring (egg) mass, and clutch size relate to body mass among species of branchiopod, maxillipod, and malacostracan crustaceans, as well as how these important life history traits vary among major taxa and environments independently of body size. Clutch mass relates strongly and nearly isometrically to body mass, probably because of physical volumetric constraints. By contrast, egg mass and clutch size relate more weakly and curvilinearly to body mass and vary in inverse proportion to one another, thus indicating a fundamental trade-off, which occurs within many crustacean taxa as well. In general, offspring (egg) size and number and their relationships to body mass appear to be more ecologically sensitive and evolutionarily malleable than clutch mass. The body mass scaling relationships of egg mass and clutch size show much more taxonomic and ecological variation (log-log scaling slopes varying from near 0 to almost 1 among major taxa) tha...

Urgent plea for global protection of springs

Conservation Biology, 2020

Marco Cantonati , Roderick J. Fensham , Lawrence E. Stevens , Reinhard Gerecke , Douglas S. Glazi... more Marco Cantonati , Roderick J. Fensham , Lawrence E. Stevens , Reinhard Gerecke , Douglas S. Glazier , Nico Goldscheider , Robert L. Knight , John S. Richardson , Abraham E. Springer , and Klement Tockner 10,11 MUSE – Museo delle Scienze, Limnology & Phycology Section, Corso del Lavoro e della Scienza 3, Trento, 38123, Italy School of Biological Sciences, The University of Queensland, St Lucia, Brisbane, 4072, Australia Springs Stewardship Institute, Museum of Northern Arizona, 3101 N. Ft. Valley Rd., Flagstaff, AZ 86001, U.S.A. Eberhard Karls University of Tübingen, Tübingen, 72076, Germany Department of Biology, Juniata College, Huntingdon, PA 16652, U.S.A. Institute of Applied Geosciences, Karlsruhe Institute of Technology (KIT), Kaiserstr. 12, Karlsruhe, 76131, Germany Howard T. Odum Florida Springs Institute, 23695 US 27, High Springs, FL 32643, U.S.A. Department of Forest and Conservation Sciences, University of British Columbia, 3041-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada School of Earth and Sustainability, Northern Arizona University, P.O. Box 4099, Flagstaff, AZ 86011, U.S.A. Leibniz-Institute of Freshwater Ecology and Inland Fisheries IGB, and Institute of Biology, Freie Universität, Berlin, Germany Austrian Science Fund FWF, Sensengasse 1, Vienna, 1090, Austria

Rediscovering and Reviving Old Observations and Explanations of Metabolic Scaling in Living Systems

Systems, 2018

Why the rate of metabolism varies (scales) in regular, but diverse ways with body size is a peren... more Why the rate of metabolism varies (scales) in regular, but diverse ways with body size is a perennial, incompletely resolved question in biology. In this article, I discuss several examples of the recent rediscovery and (or) revival of specific metabolic scaling relationships and explanations for them previously published during the nearly 200-year history of allometric studies. I carry out this discussion in the context of the four major modal mechanisms highlighted by the contextual multimodal theory (CMT) that I published in this journal four years ago. These mechanisms include metabolically important processes and their effects that relate to surface area, resource transport, system (body) composition, and resource demand. In so doing, I show that no one mechanism can completely explain the broad diversity of metabolic scaling relationships that exists. Multi-mechanistic models are required, several of which I discuss. Successfully developing a truly general theory of biological scaling requires the consideration of multiple hypotheses, causal mechanisms and scaling relationships, and their integration in a context-dependent way. A full awareness of the rich history of allometric studies, an openness to multiple perspectives, and incisive experimental and comparative tests can help this important quest.

Resource Supply and Demand Both Affect Metabolic Scaling: A Response to Harrison

Trends in Ecology & Evolution, 2018

Effects of Contingency versus Constraints on the Body-Mass Scaling of Metabolic Rate

Challenges, 2018

I illustrate the effects of both contingency and constraints on the body-mass scaling of metaboli... more I illustrate the effects of both contingency and constraints on the body-mass scaling of metabolic rate by analyzing the significantly different influences of ambient temperature (T a) on metabolic scaling in ectothermic versus endothermic animals. Interspecific comparisons show that increasing T a results in decreasing metabolic scaling slopes in ectotherms, but increasing slopes in endotherms, a pattern uniquely predicted by the metabolic-level boundaries hypothesis, as amended to include effects of the scaling of thermal conductance in endotherms outside their thermoneutral zone. No other published theoretical model explicitly predicts this striking variation in metabolic scaling, which I explain in terms of contingent effects of T a and thermoregulatory strategy in the context of physical and geometric constraints related to the scaling of surface area, volume, and heat flow across surfaces. My analysis shows that theoretical models focused on an ideal 3/4-power law, as explained by a single universally applicable mechanism, are clearly inadequate for explaining the diversity and environmental sensitivity of metabolic scaling. An important challenge is to develop a theory of metabolic scaling that recognizes the contingent effects of multiple mechanisms that are modulated by several extrinsic and intrinsic factors within specified constraints.

Ontogenetic body-mass scaling of nitrogen excretion relates to body surface area in diverse pelagic invertebrates

Limnology and Oceanography, 2016

Many physiological and ecological processes depend on body size and the supply of limiting nutrie... more Many physiological and ecological processes depend on body size and the supply of limiting nutrients. Hence, it is important to derive quantitative predictions based on a mechanistic understanding of the influence of body size on metabolic rate and on the ratios of consumed to excreted elements. Among diverse pelagic invertebrates that change shape during ontogeny, recent analysis has demonstrated a significant positive correlation between the body-mass allometry of respiration rates (measured as the ontogenetic body mass-scaling exponent b R) and the allometry of body surface area (b A , as predicted from body-shape changes using a Euclidean model). As many pelagic invertebrates use a large portion of their external body surface for both resource uptake and waste excretion, we predicted that body-mass scaling exponents for rates of excretion of soluble N (b N) should also then relate to the degree of body-shape change during growth. We tested this hypothesis using literature data on b N for 39 species of pelagic invertebrates across five different phyla, and find strong support: b N is significantly positively correlated with predicted b A , whilst also co-varying with b R. Intraspecific differences between b N and b R values reveal ontogenetic shifts in the ratio of O 2-consumed to N-excreted. We suggest that a variety of factors, including adaptive developmental shifts in the relative anabolism and catabolism of proteins and lipids, may cause these shifts in consumption-excretion ratios. Diverse pelagic invertebrates that dominate vast open water ecosystems falsify the predictions of general metabolic scaling theories built upon resource-transport networks, but support predictions of surfacearea dependent theory.

Ecology of ontogenetic body-mass scaling of gill surface area in a freshwater crustacean

The Journal of Experimental Biology, 2017

Several studies have documented ecological effects on intraspecific and interspecific body-size s... more Several studies have documented ecological effects on intraspecific and interspecific body-size scaling of metabolic rate. However, little is known about how various ecological factors may affect the scaling of respiratory structures supporting oxygen uptake for metabolism. To our knowledge, our study is the first to provide evidence for ecological effects on the scaling of a respiratory structure among conspecific populations of any animal. We compared the body-mass scaling of gill surface area (SA) among eight spring-dwelling populations of the amphipod crustacean Gammarus minus. Although gill SA scaling was not related to water temperature, conductivity or G. minus population density, it was significantly related to predation regime (and secondarily to pH). Body-mass scaling slopes for gill SA were significantly lower in four populations inhabiting springs with fish predators than for four populations in springs without fish (based on comparing means of the population slopes, or slopes calculated from pooled raw data for each comparison group). As a result, gill SA was proportionately smaller in adult amphipods from springs with versus without fish. This scaling difference paralleled similar differences in the scaling exponents for the rates of growth and resting metabolic rate. We hypothesized that gill SA scaling is shallower in fish-containing versus fishless spring populations of G. minus because of effects of size-selective predation on size-specific growth and activity that in turn affect the scaling of oxygen demand and concomitantly the gill capacity (SA) for oxygen uptake. Although influential theory claims that metabolic scaling is constrained by internal body design, our study builds on previous work to show that the scaling of both metabolism and the respiratory structures supporting it may be ecologically sensitive and evolutionarily malleable.

Ecological Influences and Morphological Correlates of Resting and Maximal Metabolic Rates across Teleost Fish Species

The American naturalist, May 1, 2016

Rates of aerobic metabolism vary considerably across evolutionary lineages, but little is known a... more Rates of aerobic metabolism vary considerably across evolutionary lineages, but little is known about the proximate and ultimate factors that generate and maintain this variability. Using data for 131 teleost fish species, we performed a large-scale phylogenetic comparative analysis of how interspecific variation in resting metabolic rates (RMRs) and maximum metabolic rates (MMRs) is related to several ecological and morphological variables. Mass- and temperature-adjusted RMR and MMR are highly correlated along a continuum spanning a 30- to 40-fold range. Phylogenetic generalized least squares models suggest that RMR and MMR are higher in pelagic species and that species with higher trophic levels exhibit elevated MMR. This variation is mirrored at various levels of structural organization: gill surface area, muscle protein content, and caudal fin aspect ratio (a proxy for activity) are positively related with aerobic capacity. Muscle protein content and caudal fin aspect ratio are ...

Sexual dimorphism and physiological correlates of horn length in a South African isopod crustacean

Journal of Zoology, 2016

Although isopod crustaceans frequently show sexual dimorphism in body size, sexual differences in... more Although isopod crustaceans frequently show sexual dimorphism in body size, sexual differences in other non-reproductive (secondary sexual) traits have been rarely studied. Furthermore, little is known about the physiological correlates of variation in the expression of sexually dimorphic traits in animals generally. Here, we show that the unusual dorsal horns of the South African horned isopod Deto echinata exhibit significantly different allometric scaling relationships with body size in males versus females. Not only are the horns of adult males substantially longer than those of adult females but also their log-log scaling slope with body length is significantly steeper than that of females and juveniles. Furthermore, in males relative horn length is positively correlated with body condition, as estimated by body mass relative to body length, and with resting metabolic (CO 2 release) rate, also adjusted to body length. However, although showing a weak positive trend, the relative horn length of males is not significantly correlated with body length adjusted active metabolic rate. It is also not significantly correlated with the relative rates of whole body or cuticular water loss rates or with two measures of activity level. We hypothesize that the sexual dimorphism of horn length in D. echinata is the result of sexual selection and that horn length is a reliable indicator of the ability of a male to acquire and process resources, which in turn may be critical to female mate choice and (or) male-male competition for mates. However, this hypothesis requires further testing based on direct observations of female mate choice and male-male behavioral interactions, which have not yet been carried out.

Springs as model ecosystems for ecology and evolutionary biology: A case study of Gammarus minus Say (Amphipoda) in mid-Appalachian springs differing in pH and ionic content

Springs offer many advantages for ecological and evolutionary studies. Here I focus on amphipods ... more Springs offer many advantages for ecological and evolutionary studies. Here I focus on amphipods in springs as a useful model system for studying the biological effects of water chemistry. The amphipod Gammarus minus is absent from central Pennsylvania springs with a pH < about 6.0 and conductivity < 25 mS cm-1, and its population density is positively correlated with pH, conductivity, and other related water-chemistry variables. To gain insight into these patterns of G. minus distribution and abundance, my students and I have undertaken three kinds of analyses: (1) surveys of body condition and reproductive output in 10 springs differing in pH and ionic content, (2) transplant studies of the effects of water chemistry on mortality and body-mass maintenance, and (3) laboratory investigations of the effects of water chemistry on organismal energy budgets. The 10-spring survey has revealed that several indices of body condition and of reproductive output vary independently of pH...

Temperature affects food-chain length and macroinvertebrate species richness in spring ecosystems

Freshwater Science, 2012

This section of the journal is for the expression of new ideas, points of view, and comments on t... more This section of the journal is for the expression of new ideas, points of view, and comments on topics of interest to aquatic scientists. The editorial board invites new and original papers as well as comments on items already published in Freshwater Science (J-NABS). Format and style may be less formal than conventional research papers; massive data sets are not appropriate. Speculation is welcome if it is likely to stimulate worthwhile discussion. Alternative points of view should be instructive rather than merely contradictory or argumentative. All submissions will receive the usual reviews and editorial assessments.

Body-Mass Scaling of Metabolic Rate: What are the Relative Roles of Cellular versus Systemic Effects?

Biology, 2015

The reason why metabolic rate often scales allometrically (disproportionately) with body mass has... more The reason why metabolic rate often scales allometrically (disproportionately) with body mass has been debated for decades. A critical question concerns whether metabolic scaling is controlled intrinsically at the intracellular level or systemically at the organismal level. Recently, the relative importance of these effects has been tested by examining the metabolic rates of cultured dermal fibroblast and skeletal muscle cells in relation to donor body mass of a variety of birds and mammals. The lack of a relationship between in vitro cellular metabolic rates and body mass suggests that systemic effects, not intrinsic cellular effects are responsible for allometric metabolic scaling observed in whole organisms. Influential resource-transport network theory claims that the most important systemic effect involved is body-size related resource-supply limits to metabolizing cells. However, comparisons of in vitro cellular metabolic rates with scaling relationships for in vivo (basal) me...

Is metabolic rate a universal 'pacemaker' for biological processes?

Biological reviews of the Cambridge Philosophical Society, Jan 23, 2014

A common, long-held belief is that metabolic rate drives the rates of various biological, ecologi... more A common, long-held belief is that metabolic rate drives the rates of various biological, ecological and evolutionary processes. Although this metabolic pacemaker view (as assumed by the recent, influential 'metabolic theory of ecology') may be true in at least some situations (e.g. those involving moderate temperature effects or physiological processes closely linked to metabolism, such as heartbeat and breathing rate), it suffers from several major limitations, including: (i) it is supported chiefly by indirect, correlational evidence (e.g. similarities between the body-size and temperature scaling of metabolic rate and that of other biological processes, which are not always observed) - direct, mechanistic or experimental support is scarce and much needed; (ii) it is contradicted by abundant evidence showing that various intrinsic and extrinsic factors (e.g. hormonal action and temperature changes) can dissociate the rates of metabolism, growth, development and other biol...

Body shape shifting during growth permits tests that distinguish between competing geometric theories of metabolic scaling

Ecology letters, 2014

Metabolism fuels all of life's activities, from biochemical reactions to ecological interacti... more Metabolism fuels all of life's activities, from biochemical reactions to ecological interactions. According to two intensely debated theories, body size affects metabolism via geometrical influences on the transport of resources and wastes. However, these theories differ crucially in whether the size dependence of metabolism is derived from material transport across external surfaces, or through internal resource-transport networks. We show that when body shape changes during growth, these models make opposing predictions. These models are tested using pelagic invertebrates, because these animals exhibit highly variable intraspecific scaling relationships for metabolic rate and body shape. Metabolic scaling slopes of diverse integument-breathing species were significantly positively correlated with degree of body flattening or elongation during ontogeny, as expected from surface area theory, but contradicting the negative correlations predicted by resource-transport network mode...

Resource allocation patterns

Resource allocation theory applied to farm animal production, 2008

This chapter discusses the energy and nutrient allocation patterns in animals, including the prio... more