Dr. Watt's research deals with the rise of complex biological adaptations from simpler beginnings. His team uses as a study system a group of insects whose field and lab biology are both well known, allowing for greater analytical power to study the whole process of natural selection, from chemical mechanisms to actual differences in fitness among inheritable variants in the wild. Also, the fact that these insects' energy-demanding flight uses physiology common to all cellular life makes the studies of this "evolutionary model" system of general relevance to many other physiologically active animals (including humans).
Recently, Dr. Watt has found evidence of a historical "innovative step" in the structure of a particular catalytic protein which is central to animal energy processing. This "step" confers sharply increased resistance to heat stress on populations and species which carry it, as compared to other ancestral species. Perhaps as a consequence, in one population of a lowland species, now thermally resistant in this energy processing mechanism, Dr. Watt and his team find a very wide range of new variation experiencing temperature-related natural selection. Further, out of this range of variants, new and more complex combinations are becoming successful. This work will first explore the nature of the processes generating these combinations, and then test the generality of the findings among genes and species.
This work will bear on major conceptual issues in evolutionary biology, such as: - How living complexity arises from simple beginnings, which has been a central focus since Darwin; - The likelihood that some living mechanisms may exhibit chronic natural variability, rather than there routinely being one superior "type" which is predominant in populations; - Clarification of the connections between large-scale, long-term "macroevolution" across populations and species, and local "microevolution" adjusting populations to local conditions in the short term.
Understanding the complexity of adaptation to naturally changed thermal conditions will be important in understanding the stresses placed on these mechanisms by rapid human-caused change of local and global thermal conditions. There are implications here for conservation and environmental management and for agriculture and medicine as the environmental context for both change rapidly.
Ward B. Watt, Principal Investigator The best explanation of living complexity and diversity available to science is Darwin’s process of evolution by natural selection. This is well established as scientific fact. We are just beginning to understand how it works in practice. Beginning in the early 1900s, scientists have shown that specific cases of the process can be studied in "real time", just as can any other natural process. We've participated in this work since the 1960s, using tools developed by molecular biology, biochemistry, and biophysics in laboratory and field studies to study how natural, inheritable variants are subjected to natural selective presssures in the wild. As in other life-sciences work, one must choose for study a species of organism, and aspects of that organism’s biology, with which one can ask important questions. One seeks principles that apply to living creatures in general, but one must do so by study of particular species. We work with an insect system which is accessible to laboratory and field study, and has a short generation time and large populations. We focus on natural variation in mechanisms of energy processing which support basic physiological functions (here, insect flight), crucially affecting search for food and potential mates, survival of bad weather and escape from predators, etc. in the wild. These mechanisms are similar in all multicellular life forms, and the energy demands of insect flight are as intense, on a per-weight basis, as those even of trained human athletes. Thus findings about the evolution of these mechanisms in our system can illuminate physiological demands and adaptive responses in species of agricultural, environmental, or medical interest – including ourselves, our pathogens, and our domesticated crop animals or plants. Our previous work found highly selected natural variation in catalytic proteins, or enzymes, of the central energy processing pathway called glycolysis. We could predict differences in flight performance and resulting Darwinian fitness in the wild among such natural variants of glycolysis by studying their biochemical functions in the laboratory, and could then devise experimental tests of these predictions in the wild. In the first such genetic enzyme system we studied, we confirmed our predictions in field study, and detected up to ten-fold differences in Darwinian fitness among the variants. Thus we found strong natural selection maintaining variability in response to natural fluctuations of the environmental factors generating the selective pressures. With the present award, we’ve built on these successes to begin addressing a central, important problem: how are increasingly complex adaptations to environment built up by natural selection from simpler beginnings? We’ve taken three basic approaches to addressing this problem: 1) For our best understood gene-enzyme system – phosphoglucose isomerase or "PGI" – we’ve begun to study how the native protein structure of this enzyme is altered by the different genetic variants we have found in the wild. Work on this topic by a doctoral research student and the Principal Investigator has produced the first structural analysis of one of these protein variants at high resolution, and now that the techniques are well established a range of these variants will be studied more quickly. Other analysis techniques have suggested that one more complex difference between variants, which is associated with differences between species in resistance to natural heat stress, acts by altering internal structural bonds in the protein and thus affecting its overall stability. This hypothesis will be among those tested directly by our structural studies. 2) We had initial data on the evolution of two other gene-enzyme steps which connect glycolysis to related energy storage or processing pathways. Two research undergraduates and the Principal Investigator have designed new studies of the structural and functional impacts of variation at these steps, and of their impact on reproductive performance in the wild. 3) We’ve used new "genomics" to begin screening all the steps of glycolysis for natural variation, to infer alternative evolutionary scenarios affecting this variation (e.g. maintenance of variation, or of consistent "wild type" features and rejection of variation in these, or randomized variation in the absence of selective effects). The P.I., another doctoral student, a Research Associate, and several research undergraduates are carrying out these studies of evolutionary complexity at the next levels of organization above single genes. In addition to the impact of participation in this work on the educational development of the diverse research students (equally distributed between women and men) mentioned above, we’re making information about our, and others', results available to the public even as they are still developing. In 2010 we organized a symposium, open to the general public, on "Evolution and Genomics". Public response to this was so encouraging that our Research Associate and the P.I. are planning a formal "Continuing Studies" course for the public on this topic, including practical applications of evolutionary genomics to agriculture, environmental management, and medicine.
