Biomechanics meets the ecological niche: the importance of temporal data resolution

SummaryAs the air temperature of the Earth rises, ecological relationships within a community might shift, in part due to differences in the thermal physiology of species. Prediction of these shifts -an urgent task for ecologists -will be complicated if thermal tolerance itself can rapidly evolve. Here, we employ a mechanistic approach to predict the potential for rapid evolution of thermal tolerance in the intertidal limpet Lottia gigantea. Using biophysical principles to predict body temperature as a function of the state of the environment, and an environmental bootstrap procedure to predict how the environment fluctuates through time, we create hypothetical time-series of limpet body temperatures, which are in turn used as a test platform for a mechanistic evolutionary model of thermal tolerance. Our simulations suggest that environmentally driven stochastic variation of L.gigantea body temperature results in rapid evolution of a substantial ʻsafety marginʼ: the average lethal limit is 5-7°C above the average annual maximum temperature. This predicted safety margin approximately matches that found in nature, and once established is sufficient, in our simulations, to allow some limpet populations to survive a drastic, century-long increase in air temperature. By contrast, in the absence of environmental stochasticity, the safety margin is dramatically reduced. We suggest that the risk of exceeding the safety margin, rather than the absolute value of the safety margin, plays an underappreciated role in the evolution of thermal tolerance. Our predictions are based on a simple, hypothetical, allelic model that connects genetics to thermal physiology. To move beyond this simple model -and thereby potentially to predict differential evolution among populations and among species -will require significant advances in our ability to translate the details of thermal histories into physiological and population-genetic consequences.

Section: Predicting Body Temperature: a Heat-budget Modelmentioning

confidence: 99%

Section: Physiological Model Of the Energetic Costs Of Thermal Tolerancementioning

confidence: 99%

Biophysics, environmental stochasticity, and the evolution of thermal safety margins in intertidal limpets

Denny

Dowd

2012

“…One proposed strength of a more mechanistic approach to ecological and evolutionary modeling, especially that related to biomechanics, is the enhanced predictive power under novel environmental conditions, such as physiological understanding informing predicted responses to climate change (Denny and Helmuth, 2009;Helmuth et al, 2005;Hoffmann and Sgro, 2011;Hofmann and Todgham, 2010;Kearney et al, 2012;McGill et al, 2006;Norberg, 2004). However, the types of models described here, even with added realism from mechanistic functional responses, remain at the general end of the modeling trade-off described in the Introduction and therefore tend not to have the level of both realism and precision necessary for predictions (Levins, 1966).…”

Section: Conservation Applicationsmentioning

confidence: 99%

Integrating mechanistic organism–environment interactions into the basic theory of community and evolutionary ecology

Baskett¹

2012

SummaryThis paper presents an overview of how mechanistic knowledge of organism-environment interactions, including biomechanical interactions of heat, mass and momentum transfer, can be integrated into basic theoretical population biology through mechanistic functional responses that quantitatively describe how organisms respond to their physical environment. Integrating such functional responses into simple community and microevolutionary models allows scaling up of the organism-level understanding from biomechanics both ecologically and temporally. For community models, Holling-type functional responses for predator-prey interactions provide a classic example of the functional response affecting qualitative model dynamics, and recent efforts are expanding analogous models to incorporate environmental influences such as temperature. For evolutionary models, mechanistic functional responses dependent on the environment can serve as fitness functions in both quantitative genetic and game theoretic frameworks, especially those concerning function-valued traits. I present a novel comparison of a mechanistic fitness function based on thermal performance curves to a commonly used generic fitness function, which quantitatively differ in their predictions for response to environmental change. A variety of examples illustrate how mechanistic functional responses enhance model connections to biologically relevant traits and processes as well as environmental conditions and therefore have the potential to link theoretical and empirical studies. Sensitivity analysis of such models can provide biologically relevant insight into which parameters and processes are important to community and evolutionary responses to environmental change such as climate change, which can inform conservation management aimed at protecting response capacity. Overall, the distillation of detailed knowledge or organism-environment interactions into mechanistic functional responses in simple population biology models provides a framework for integrating biomechanics and ecology that allows both tractability and generality.

“…Far fewer studies have taken an 'ecomechanics' perspective (Wainwright et al, 1976;Denny and Gaylord, 2010) (see also Denny, 2012) to explore how physical principles affecting individuals might drive trends at population, community or ecosystem scales. Analogous methods originating in physiological fields, such as environmental tolerance constructs (Kearney et al, 2012) and dynamic energy budget models (Nisbet et al, 2012), have received somewhat more use, albeit not yet in kelp systems.…”

Section: Introductionmentioning

confidence: 99%

Roles of transport and mixing processes in kelp forest ecology

Gaylord¹,

Nickols²,

Jurgens³

2012

where B, D, I and E are the number of births, deaths, immigrants and emigrants, respectively. The biology of canopy-forming kelps like Macrocystis is such that there are multiple avenues by which physical processes influence terms on the right-hand side of Eqn 1. Among the most obvious are those affecting immigration and emigration rates, although all four parameters may be impacted. Kelps [i.e. brown algae of the order Laminariales (Abbott and Hollenberg, 1976)] produce reproductive propagules (microscopic spores) that serve as the primary agent of dispersal and have little capacity for swimming. Therefore, hydrodynamics dictate how far spores are carried, whether they exit their population of origin, and rates at which they enter adjacent populations. Properties of spore transport interact with other life history features as well. Most canopy-forming kelps have specific depth and substrate requirements, which confine them to locations where there is adequate light for growth and rocky seafloor for attachment. Especially for taxa that inhabit deeper, subtidal waters (5-30m depth), these constraints encourage discontinuities in distribution, with populations growing as disjunct forests separated by expanses Accepted 13 September 2011 Summary Fluid-dynamic transport and mixing processes affect birth, death, immigration and emigration rates in kelp forests, and can modulate broader community interactions. In the most highly studied canopy-forming kelp, Macrocystis pyrifera (the giant kelp), models of hydrodynamic and oceanographic phenomena influencing spore movement provide bounds on reproduction, quantify patterns of local and regional propagule supply, identify scales of population connectivity, and establish context for agents of early life mortality. Other analyses yield insight into flow-mediated species interactions within kelp forests. In each case, advances emerge from the use of ecomechanical approaches that propagate physical-biological connections at the scale of the individual to higher levels of ecological organization. In systems where physical factors strongly influence population, community or ecosystem properties, such mechanics-based methods promote crucial progress but are just beginning to realize their full potential.