Posted by Anon on 2/7/2003, 3:43 am
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This is a study on trees, but, presumably, the same principle would apply with respect to humans. For example, neutral markers would cluster Europeans together, apart from Middle Easterners. But, it seems that one set of personality traits have been selected for in Northern Europeans, while another set have been selected for in southern Europeans and Middle Easterners (and Negroes), perhaps explaining why most southern Europeans on this board are unable to behave in a civilized manner. See this article, for example: Worthy also correlated eye color with positions played. Dark eyed whites are overrepresented in the same positions in which blacks are overrepresented. In Worthy's theory, eye color plays a direct role. However, eye color also varies with ethnic origin, with north Europeans having more blue eyes. This suggests an Old World cline such that ability to react to opponents' actions increases to the south. What circumstances would have selected for these different abilities? Survival in fights with other males would appear to depend on quick reactions to opponents' moves. In contrast, a hunter usually stalks his prey and then chooses the time to attack. Worthy's observations could be explained if male reproductive success in colder regions varied with hunting ability, while in the tropics it varied more with fighting ability. The eye color differences could be explained if hunting was even more important in northern Europe than in southern Europe, or if southern Europeans had interbred more with farmers of Middle Eastern origin. Here are excerpts from the study: Neutral DNA markers fail to detect genetic divergence in an ecologically important trait Biological Conservation. Vol: 110 Issue: 2, April, 2003 pp: 267-275 Abstract The development of strategies for in situ, ex situ conservation and reforestation of the monkey puzzle tree ( Araucaria araucana), a vulnerable tree endemic to southern South America, has led to an interest in the level and distribution of the genetic diversity of the species. Neutral DNA markers (RAPDs) and quantitative genetic techniques were used to characterise genetic heterogeneity within and among populations from throughout the natural range of the species. Both the level and pattern of genetic variation estimated using the different techniques were essentially uncorrelated. An important discrepancy was found with the neutral markers failing to detect an important quantitative genetic divergence across the Andean Range relating to drought tolerance. This study clearly demonstrates the potential problems associated with making recommendations for conserving the genetic resource of threatened species based solely on neutral marker studies. Alternative approaches are discussed, including a stronger focus on ecologically important traits and the potential use of surrogate measures of genetic variability. Keywords: Araucaria araucana; Conservation genetics; Evolutionary potential; Quantitative genetics and RAPDs. 1. Introduction Genetic marker studies currently play a significant role in the scientific assessment of threatened species ( Haig, 1998 ) and regularly contribute to policy development for conservation management. It is assumed that genetic diversity is of prime importance for species persistence ( Frankel, 1983, Allendorf & Leary, 1986, Geburek, 1997 ) and is associated with the adaptive and evolutionary potential of populations ( Ennos et al., 1997 ). If neutral markers adequately measured adaptive variation, they would indeed allow an indirect estimate of the genetic structure needed for conservation ( Geburek, 1997 ). However, for several reasons, there is often a poor correlation between neutral marker variation and quantitative variation for adaptively important traits ( Ennos et al., 1997, Reed & Frankham, 2001, Pefender et al., 2000 ). Hence marker genes have limitations if the aim is to provide information on adaptation and long-term survival of populations ( Waldmann & Andersson, 1998 ). Furthermore, estimates of genetic variability and differentiation may differ widely depending on the choice of marker ( Geburek, 1997 ), statistics employed ( Bossart & Prowell, 1998 ) the life-stage sampled ( Alvarez-bullya et al., 1996 ) and even the laboratory in which experiments are conducted ( Jones et al., 1997 ). Additionally, it has been demonstrated that it is extremely difficult to produce a representative estimate of the `real´ neutral genetic diversity of a species using the limited number of individuals typically sampled in molecular genetics studies ( Chakraborty, 1981 ). It has been recommended that, whenever possible, studies of geographical variation in morphological or physiological traits should be included in the development of management policies ( Hamrick et al., 1991 ). However, the majority of genetic information for threatened species is from molecular markers ( Frankham, 1995 ). Only a few attempts have been made to measure both quantitative trait and neutral DNA variation in plant populations (e.g. Karhu et al., 1996, Yang, 1996, Ennos et al., 1997, Waldmann & Andersson, 1998, Lynch et al., 1999 ). Reed & Frankham, 2001 conducted a meta-analysis based on 71 data sets including measures of both molecular and quantitative genetic variation and found a weak association between the techniques for patterns of variation among populations. Similarly, Mckay & Latta 2002 surveyed the literature for studies reporting both Fst (population genetic structure detected using neutral markers) and Qst (an analogous measure for quantitative traits) and found that Qst is typically larger than and poorly correlated with Fst. This raises an important issue if the goal of a population genetic study is to make recommendations for conservation strategies, such as seed zone designation in planning for reforestation and ex situ conservation programs. The danger arises when results from studies using neutral molecular markers are used to infer the amount and distribution of variation in adaptively important traits resulting in inappropriate management recommendations, such as seed zone designation (for example, Rossetto et al., 1995, Martin et al., 1997, Hudson et al., 2000, Mattner et al., 2002 ). The species under investigation in the present study, Araucaria araucana (Molina) K. Koch (Araucariaceae), commonly known as the monkey puzzle tree or Pehuén, is a vulnerable tree of exceptional cultural, economic and ecological significance, endemic to southern Chile and Argentina. Monkey puzzle is an impressively large and long-lived conifer, attaining 50 m in height, 2.5 m in girth and reaching ages of at least 1300 years ( Montaldo, 1974 ) and is of conservation concern, owing to extensive historical clearance and current human-induced pressures. Monkey puzzle occurs over a very wide ecological range ( Veblen, 1982 ); annual precipitation decreases from west to east of the Andes from more than 400 cm on west-facing slopes in Chile to less than 20 cm on the Argentinean steppe, over an elevation range from 600 to almost 2000 m above sea level ( Delmastro & Donoso, 1980 ). In view of this strong ecological gradient and the geographic separation of coastal and Andean populations of monkey puzzle (see Fig. 1), some degree of genetic differentiation may be expected. Delmastro & Donoso, 1980 speculated that racial divergence was probable between coastal and Andean populations and observed some differences in plant form and the degree of vegetative reproduction, although the genetic basis of these traits was not assessed. Because of its status as a high profile, vulnerable species, the development of conservation strategies is a high priority, incorporating in situ and ex situ approaches, and restoration of degraded populations. These initiatives provided the motivation for studying the level and distribution of genetic variability within this species, in order to designate appropriate seed zones and identify populations of particular conservation concern. 5. Conclusion Neutral marker studies may have useful application in conservation biology in terms of providing information about the mating system, gene flow and population history of a species, including determining evolutionary lineages ( Ennos, 1996 ). However, they are not appropriate as a tool for providing information about a population's adaptive potential or to estimate local adaptation and population divergence. This was demonstrated in the present study, by the lack of congruence between both the level and distribution of adaptive versus neutral variation in populations of the monkey puzzle tree. Importantly, the neutral markers failed to detect divergence in an ecologically important trait relating to drought tolerance across the Andean Range. Several alternative approaches are suggested; the applicability of each approach would need to be assessed for each target species in terms of availability of funding, technical support, prior knowledge of the genome and the existence of other conservation priorities.