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The evolution of female promiscuity poses an intriguing problem as benefits of mating with multiple males often have to arise via indirect, genetic, effects. Studies on birds have documented that multiple paternity is common in natural populations but strong evidence for selection via female benefits is lacking. In an attempt to evaluate the evidence more broadly, we review studies of multiple paternity in natural populations of all major groups of nonavian reptiles. Multiple paternity has been documented in all species investigated so far and commonly exists in over 50% of clutches, with particularly high levels in snakes and lizards. Marine turtles and lizards with prolonged pair-bonding have relatively low levels of multiple paternity but levels are nevertheless higher than in many vertebrates with parental care. There is no evidence that high levels of polyandry are driven by direct benefits to females and the evidence that multiple paternity arises from indirect genetic benefits is weak. Instead, we argue that the most parsimonious explanation for patterns of multiple paternity is that it represents the combined effect of mate-encounter frequency and conflict over mating rates between males and females driven by large male benefits and relatively small female costs, with only weak selection via indirect benefits. A crucial step for researchers is to move from correlative approaches to experimental tests of assumptions and predictions of theory under natural settings, using a combination of molecular techniques and behavioural observations.

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Telomeres play a fundamental role in the protection of chromosomal DNA and in the regulation of cellular senescence. Recent work in human epidemiology and evolutionary ecology suggests adult telomere length (TL) may reflect past physiological stress and predict subsequent morbidity and mortality, independent of chronological age.Several different methods have been developed to measure TL, each offering its own technical challenges. The aim of this review is to provide an overview of the advantages and drawbacks of each method for researchers, with a particular focus on issues that are likely to face ecologists and evolutionary biologists collecting samples in the field or in organisms that may never have been studied in this context before.We discuss the key issues to consider and wherever possible try to provide current consensus view regarding best practice with regard to sample collection and storage, DNA extraction and storage, and the five main methods currently available to measure TL.Decisions regarding which tissues to sample, how to store them, how to extract DNA, and which TL measurement method to use cannot be prescribed, and are dependent on the biological question addressed and the constraints imposed by the study system. What is essential for future studies of telomere dynamics in evolution and ecology is that researchers publish full details of their methods and the quality control thresholds they employ.

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SUMMARYReproduction is energetically expensive for males as well as for females, but evolutionary biologists have typically regarded the energy costs of sperm production as trivial compared to the energy costs of overt reproductive behaviours, such as mate-searching, courtship, copulation and male-male combat. Adders (Vipera berus) offer an ideal model system in which to quantify the relative costs of spermatogenesis (and associated physiological preparations for reproductive activity) versus the costs of overt reproductive behaviours, because (i) these two activities occur sequentially rather than simultaneously, and are separated by a clear indicator (sloughing of the skin) ; and (ii) males do not feed during either of these phases. Hence, the rate of mass loss by males can be used as an index of energy costs. Surprisingly, the rate of mass loss is at least as high during the phase when males are immobile, building up sperm supplies, as when they move about and engage in reproductive behaviour. Rates of mass loss are not significantly correlated with male size or measures of the male's participation in reproductive activities. Our data suggest that sperm production may be a major energy cost to reproducing male adders, and that this species offers a useful system in which to further investigate this possibility.

In mice and man, females prefer males with a major histocompatibility complex (MHC) genotype different to their own. We tested whether this phenomenon also occurs in the Swedish sand lizard (Lacerta agilis). Females in a laboratory experiment preferred to associate with odour samples obtained from more distantly related males at the MHC class 1 loci. Data on free-ranging lizards suggest that associations between males and females are nonrandom with respect to MHC genotype. However, male spatial distribution and mobility during the mating season suggest that the non-random pairing process in the wild may also be driven by corresponding genetic benefits to males pairing with less related females.