Synopsis

Abstract

Any change in consumer–user interactions may have positive, negative, or neutral effects on relative reproduction of consumers and mean fitness of populations. At all levels of organization, individuals are characterized by “core” patterns, processes, and units (switches, circuits, protein regulation, neurotransmitter substances, motor patterns, recruitment), each of which is differentially responsive to abiotic and biotic (including social) stress. Some taxa appear to be preadapted to heterogeneous, even, near-lethal conditions (folivores), exhibiting significant thermal tolerances and resistance to thermal stress (desiccation). Flexibility as well as integration of system units is regulated by communication (“crosstalk”) and regulatory feedback between thermosensors, mitochondria, and transcription factors demonstrating “remarkable versatility” for many types of (robust and plastic) reorganization at the molecular level. Gene regulation is amenable to epigenetic effects, particularly ecological (microclimate) factors (variations in T, food), information that is stored in neural “memory,” influencing future molecular and cellular, including synaptic (“Hebbian”), events. Relative to system properties and tolerances, as well as spatiotemporal variations in limiting (functional ecological) resources (food items, nutrients, mates, breeding, conspecifics), energy is allocated to maintenance activities (system repair, homeostasis), survival (responses to parasitism, predation, interference, stress), and reproduction. At a given time, size of energy stores is limited (“elastic limit”) and limiting, but, in mammals, female thermal stores (“fat”) are proportionately larger compared to males in the same population. Some mammalian orders (rodents, bats, primates) include a number of species capable of storing energy in food pouches, and it may be of note that these orders include, as well, many social species. Several researchers highlight the paucity of field data on mammalian norms of reaction across ecological gradients, pointing out that, although much is known about separate stages from mammal genotypes to phenotypes, little is known about how the stages are coordinated and controlled from one level of system organization to another.