The evolutionary genetics of haplodiploids and X-linked genes share many features and are different from diploid (autosomal) genes in many respects. For example, the conditions for a stable polymorphism, the amount of genetic load, and the effective population size are all expected to be quite different between haplodiploids or X-linked genes and diploids. From experimental data, the genetic load for X-linked genes is much less than autosomal genes and appears less for haplodiploids than for diploids. The observed amount of molecular variation for haplodiploids is much less than that for diploids, even more so than predicted from the differences in effective population size. Extensive recently published data suggest that the differences in variation for X-linked and autosomal genes for Drosophila, mice, and humans are consistent with the differences predicted theoretically based on the relative effective population sizes.

Reactive oxygen species, the by-products of oxidative energy metabolism, are considered a main proximate cause of aging. Accordingly, overexpression of the enzyme Cu-Zn superoxide dismutase 1 (SOD1) can lengthen lifespan of Drosophila melanogaster in the laboratory. However, the role of SOD1 as a main determinant of lifespan has been challenged on the grounds that overexpression might be effective only in compromised genetic backgrounds. Moreover, interspecific comparisons show lower levels of antioxidant activities in longer-lived species, suggesting that life-span extension may evolve through less reactive oxygen species generation from the mitochondria rather than higher expression of SOD1. The tremendous variation in lifespan between ant castes, ranging over 2 orders of magnitude, coupled with the fact that all individuals share the same genome, provides a system to investigate the role of SOD1 in the wild. We used the ant Lasius niger as a model system, because queens can reach the extreme age of 28 years, whereas workers and males live only 1-2 years and a few weeks, respectively. We cloned SOD1 and found that long-lived queens have a lower level of expression than workers and males. Specific enzyme-activity assays also showed higher SOD1 activity levels in males and workers compared with queens, which had SOD1 activity levels similar to that of D. melanogaster. Altogether, these data show that increased expression of SOD1 is not required for the evolution of extreme lifespan, even in a system in which differential gene expression is the only way to express phenotypes with great lifespan differences.T o date, most of the genes implicated in aging have been identified in laboratory populations of short-lived model organisms such as the fruit fly Drosophila melanogaster, the nematode Caenorhabditis elegans, and the yeast Saccharomyces cerevisiae (1-4). However, it is not known whether these genes are functionally important in underlying lifespan differences in the wild or whether they may also influence lifespan of longerlived organisms.One of the more prominent antioxidant enzymes thought to be involved in lifespan extension is encoded by the gene superoxide dismutase 1 (SOD1). SOD1 overexpression was originally found to extend lifespan in D. melanogaster (5-10), and some D. melanogaster lines selected for extended longevity also show increased levels of expression of SOD1 (11, 12). However, additional experiments showed that the effect of SOD1 overexpression depends on the genetic background of the particular lines used (13-16). Most recently, it has been shown that SOD1 overexpression positively effects lifespan in some but not all natural genetic backgrounds (17).Experiments in other organisms have also provided contrasting results. In yeast, increased lifespan has been obtained by overexpression of SOD1 and the mitochondrial form of SOD (18), but in C. elegans, contradictory results were obtained for chemical mimetics of SOD dependent on laboratory conditions (19,20). In mice, manipulation of SOD1 level...

SummaryTelomere length regulation is an important aspect of cell maintenance in eukaryotes, since shortened telomeres can lead to a number of defects, including impaired cell division. Although telomere length is correlated with lifespan in some bird species, its possible role in aging and lifespan determination is still poorly understood. Here we investigate telomere dynamics (changes in telomere length and attrition rate) and telomerase activity in the ant Lasius niger , a species in which different groups of individuals have evolved extraordinarily different lifespans. We found that somatic tissues of the short-lived males had dramatically shorter telomeres than those of the much longer-lived queens and workers. These differences were established early during larval development, most likely through faster telomere shortening in males compared with females. Workers did not, however, have shorter telomeres than the longer-lived queens. We discuss various molecular mechanisms that are likely to cause the observed sexspecific telomere dynamics in ants, including cell division, oxidative stress and telomerase activity. In addition, we discuss the evolutionary causes of such patterns in ants and in other species.