Molecular and cellular studies in evolutionary physiology of natural vertebrate populations: influences of individual variation and genetic components on sampling and measurements.

Studies combining ecological, genetic and physiological approaches are needed in evolutionary biology. Although the combination of approaches has been emphasized, such studies have been rare with regard to molecular and cellular studies on natural vertebrate populations. The major reasons for this are that the generation time of vertebrates is long and it is difficult to find a molecular or cell physiological measurement that is both relevant for the fitness of the population and can be repeated an adequate number of times to enable estimations of individual variability. The paucity of suitable physiological parameters is partly due to the fact that most physiological studies have not been directed towards understanding the behaviour of populations but towards understanding the basic mechanisms of the function of individuals. Also, physiological measurements that appear most relevant from the point of view of evolutionary studies are often integrative functions, composed of the function of many genes. When dissecting the integrative functions into components, it is often observed that the same integrative response can be achieved via different routes, i.e. changes in the responses of different genes. To enable cellular and molecular physiological studies to be increasingly combined with ecological and genetic studies, it is important that such studies include and report individual variability and that the sample size is increased. In addition, more sophisticated statistical methods should be used than is traditionally done, and when the function of most genes in the integrative response are not known, techniques such as QTL mapping should be used. Hitherto in vertebrates, the methodology has mainly been used in production biology (e.g. meat or milk production). With regard to combining genomic and physiological studies, one must bear in mind that the massive datasets associated with genomic studies need to be further enlarged to enable estimates of individual variation. It is also important to remember that microarray and proteomic data give the levels of mRNA and proteins, respectively. Since the function of the protein can be regulated independently of its transcription or its level in the cell, direct physiological measurements are also needed if estimations of protein activity in the individuals of a population are wanted.