Paul E. Hertz

Bio: Paul E. Hertz is an academic researcher from Barnard College. The author has contributed to research in topics: Anolis & Niche. The author has an hindex of 25, co-authored 39 publications receiving 4888 citations. Previous affiliations of Paul E. Hertz include Harvard University & Columbia University.

Why tropical forest lizards are vulnerable to climate warming

Abstract: Biological impacts of climate warming are predicted to increase with latitude, paralleling increases in warming. However, the magnitude of impacts depends not only on the degree of warming but also on the number of species at risk, their physiological sensitivity to warming and their options for behavioural and physiological compensation. Lizards are useful for evaluating risks of warming because their thermal biology is well studied. We conducted macrophysiological analyses of diurnal lizards from diverse latitudes plus focal species analyses of Puerto Rican Anolis and Sphaerodactyus. Although tropical lowland lizards live in environments that are warm all year, macrophysiological analyses indicate that some tropical lineages (thermoconformers that live in forests) are active at low body temperature and are intolerant of warm temperatures. Focal species analyses show that some tropical forest lizards were already experiencing stressful body temperatures in summer when studied several decades ago. Simulations suggest that warming will not only further depress their physiological performance in summer, but will also enable warm-adapted, open-habitat competitors and predators to invade forests. Forest lizards are key components of tropical ecosystems, but appear vulnerable to the cascading physiological and ecological effects of climate warming, even though rates of tropical warming may be relatively low.

Evaluating temperature regulation by field-active ectotherms: the fallacy of the inappropriate question.

Abstract: We describe a research protocol for evaluating temperature regulation from data on small field-active ectothermic animals, especially lizards. The protocol requires data on body temperatures (Tb) of field-active ectotherms, on available operative temperatures (Te, "null temperatures" for nonregulating animals), and on the thermoregulatory set-point range (preferred body temperatures, Tset). These data are used to estimate several quantitative indexes that collectively summarize temperature regulation: the "precision" of body temperature (variance in Tb, or an equivalent metric), the "accuracy" of body temperature relative to the set-point range (the average difference between Tb and Tset), and the "effectiveness" of thermoregulation (the extent to which body temperatures are closer on the average to the set-point range than are operative temperatures). If additional data on the thermal dependence of performance are available, the impact of thermoregulation on performance (the extent to which performance is enhanced relative to that of nonregulating animals) can also be estimated. A sample analysis of the thermal biology of three Anolis lizards in Puerto Rico demonstrates the utility of the new protocol and its superiority to previous methods of evaluating temperature regulation. We also discuss several ways in which the research protocol can be extended and applied to other organisms.

Behavioral drive versus behavioral inertia in evolution: a null model approach.

Abstract: Some biologists embrace the classical view that changes in behavior inevitably initiate or drive evolutionary changes in other traits, yet others note that behavior sometimes inhibits evolutionary changes. Here we develop a null model that quantifies the impact of regulatory behaviors (specifically, thermoregulatory behaviors) on body temperature and on performance of ectotherms. We apply the model to data on a lizard (Anolis cristatellus) and show that ther- moregulatory behaviors likely inhibit selection for evolutionary shifts in thermal physiology with altitude. Because behavioral adjustments are commonly used by ectotherms to regulate physiological per- formance, regulatory behaviors should generally constrain rather than drive evolution, a phenomenon we call the "Bogert effect." We briefly review a few other examples that contradict the classical view of behavior as the inevitable driving force in evolution. Overall, our analysis and brief review challenge the classical view that behavior is invariably the driving force in evolution, and instead our work supports the alternative view that behavior has diverse—and some- times conflicting—effects on the directions and rates at which other traits evolve.

Is a Jack-of-All-Temperatures a Master of None?

Abstract: FIG. I. Hypothetical performance curves of ectotherms as function of body temperature. (a) Example predicted from the Principle of Allocation, involving a tradeoff between maximum performance and breadth of performance. The categories \"specialist\" and \"generalist\" are not discrete but are endpoints on a continuum. (b) Example contradicting the Principle, in which traits that promote performance at one temperature promote performance at all temperatures. .. u c o E

Niche lability in the evolution of a Caribbean lizard community

Abstract: Niche conservatism--the tendency for closely related species to be ecologically similar--is widespread. However, most studies compare closely related taxa that occur in allopatry; in sympatry, the stabilizing forces that promote niche conservatism, and thus inhibit niche shifts, may be countered by natural selection favouring ecological divergence to minimize the intensity of interspecific interactions. Consequently, the relative importance of niche conservatism versus niche divergence in determining community structure has received little attention. Here, we examine a tropical lizard community in which species have a long evolutionary history of ecological interaction. We find that evolutionary divergence overcomes niche conservatism: closely related species are no more ecologically similar than expected by random divergence and some distantly related species are ecologically similar, leading to a community in which the relationship between ecological similarity and phylogenetic relatedness is very weak. Despite this lack of niche conservatism, the ecological structuring of the community has a phylogenetic component: niche complementarity only occurs among distantly related species, which suggests that the strength of ecological interactions among species may be related to phylogeny, but it is not necessarily the most closely related species that interact most strongly.

Human biochemical genetics

Abstract: So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Climate change and evolutionary adaptation

Abstract: Evolutionary adaptation can be rapid and potentially help species counter stressful conditions or realize ecological opportunities arising from climate change. The challenges are to understand when evolution will occur and to identify potential evolutionary winners as well as losers, such as species lacking adaptive capacity living near physiological limits. Evolutionary processes also need to be incorporated into management programmes designed to minimize biodiversity loss under rapid climate change. These challenges can be met through realistic models of evolutionary change linked to experimental data across a range of taxa.

Adaptive versus non‐adaptive phenotypic plasticity and the potential for contemporary adaptation in new environments

Abstract: Summary 1The role of phenotypic plasticity in evolution has historically been a contentious issue because of debate over whether plasticity shields genotypes from selection or generates novel opportunities for selection to act. Because plasticity encompasses diverse adaptive and non-adaptive responses to environmental variation, no single conceptual framework adequately predicts the diverse roles of plasticity in evolutionary change. 2Different types of phenotypic plasticity can uniquely contribute to adaptive evolution when populations are faced with new or altered environments. Adaptive plasticity should promote establishment and persistence in a new environment, but depending on how close the plastic response is to the new favoured phenotypic optimum dictates whether directional selection will cause adaptive divergence between populations. Further, non-adaptive plasticity in response to stressful environments can result in a mean phenotypic response being further away from the favoured optimum or alternatively increase the variance around the mean due to the expression of cryptic genetic variation. The expression of cryptic genetic variation can facilitate adaptive evolution if by chance it results in a fitter phenotype. 3We conclude that adaptive plasticity that places populations close enough to a new phenotypic optimum for directional selection to act is the only plasticity that predictably enhances fitness and is most likely to facilitate adaptive evolution on ecological time-scales in new environments. However, this type of plasticity is likely to be the product of past selection on variation that may have been initially non-adaptive. 4We end with suggestions on how future empirical studies can be designed to better test the importance of different kinds of plasticity to adaptive evolution.

The Evolution of Ecological Specialization

Abstract: The evolution of "niche breadth," or "niche width," was a more popular topic in the evolutionary ecological literature of the 1960s and 1970s than it has been recently (109, 118, 120, 134, 155, 156). This review summarizes current hypotheses on the evolution of specialization and generalization and suggests areas in which future research might be rewarding. The topic is so broad that every area of biology bears on it. We cannot hope to offer an exhaustive review of evidence and in particular have slighted much of the ecological literature to emphasize genetic and evolutionary perspectives. We limit our discussion almost entirely to animals. We adopt Hutchinson's (86) representation of a population's ecological niche as an n-dimensional hypervolume, the axes of which are environmental variables or resources. Along each of these, the population displays a wide or narrow tolerance or pattern of utilization, relative to other populations or species. Specialization and generalization must be defined with reference to particular axes (e.g. temperature, range of food particle sizes). Brown (9) suggests that niche breadth along different axes is positively correlated and that this explains positive correlations across species between local abundance and breadth of geographic range. Multidimensional specialization might be expected if species arise in localized regions that differ in several ecological respects from those occupied by parent species. Cody (20), however, suggested that the breadth of habitat is negatively correlated with diet breadth among certain bird species. In practice, quantitative measurement of niche breadth can be difficult (22,

Niche Conservatism: Integrating Evolution, Ecology, and Conservation Biology

Abstract: ▪ Abstract Niche conservatism is the tendency of species to retain ancestral ecological characteristics. In the recent literature, a debate has emerged as to whether niches are conserved. We suggest that simply testing whether niches are conserved is not by itself particularly helpful or interesting and that a more useful focus is on the patterns that niche conservatism may (or may not) create. We focus specifically on how niche conservatism in climatic tolerances may limit geographic range expansion and how this one type of niche conservatism may be important in (a) allopatric speciation, (b) historical biogeography, (c) patterns of species richness, (d) community structure, (e) the spread of invasive, human-introduced species, (f) responses of species to global climate change, and (g) human history, from 13,000 years ago to the present. We describe how these effects of niche conservatism can be examined with new tools for ecological niche modeling.