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

Abstract

SUMMARY 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.

Thermal variation, thermal extremes and the physiological performance of individuals

“…Despite the current limitations in quantifying environmental variation, improvement in the ability to measure and model the types of spatial and temporal thermal variation encountered by organisms has greatly outpaced our ability to predict the physiological consequences of realistic environmental variation (Denny and Helmuth, 2009;Denny and Dowd, 2012;Nikinmaa and Waser, 2007). Contrasting the pattern of temporal variation in an organism's body temperature (Fig.…”

“…However, this focus draws attention away from the fact that contemporary patterns in biochemistry and physiology are products of selection on the variation that existed in the ancestors of present-day organisms. When confronted with changes in their environment, different individuals within a species can be quite variable in their response (Crawford and Oleksiak, 2007;Krebs and Feder, 1997;Nikinmaa and Waser, 2007;Williams, 2008). The sources and consequences of this variation are pivotal to understanding species' potentials to cope with changing environments (Whitehead and Crawford, 2006).…”

Egg yolk environment differentially influences physiological and morphological development of broiler and layer chicken embryos

“…Bennett, 1987;Peterson et al, 1998;Williams, 2008) and continues to shape comparative developmental physiology (e.g. Peterson et al, 1998;Gibbs, 1999;Nijhout, 2003;Spicer and Burggren, 2003;Burggren and Warburton, 2005;Nikinmaa and Waser, 2007;Spicer and Rundle, 2007). Numerous animal models are available, but the chicken embryo, because of both its venerable history in developmental biology and extensive artificial selection for commercially profitable traits in domesticated breeds, is an excellent model for the study of phenotypic variation between animal populations.…”

Variation in yolk precursor receptor mRNA expression is a key determinant of reproductive phenotype in the zebra finch (Taeniopygia guttata)

“…Firstly, as is the case in most studies that correlate gene expression with physiological variation in phenotype (Crawford and Oleksiak, 2007;Whitehead and Crawford, 2006), our study focused on the variation in mRNA levels. Changes in mRNA, however, do not necessarily correlate with changes in protein activity and function (Nikinmaa and Waser, 2007), and thus it will be necessary to analyse variation in the mature VTG/VLDL-R protein as well. The pattern of oocyte growth, coupled with our data on mRNA expression, would predict that VTG/VLDL-R protein will increase during follicle growth.…”