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1.  Proximate determinants of telomere length in sand lizards (Lacerta agilis) 
Biology Letters  2010;6(5):651-653.
Telomeres are repeat sequences of non-coding DNA that cap the ends of chromosomes and contribute to their stability and the genomic integrity of cells. In evolutionary ecology, the main research target regarding these genomic structures has been their role in ageing and as a potential index of age. However, research on humans shows that a number of traits contribute to among-individual differences in telomere length, in particular traits enhancing cell division and genetic erosion, such as levels of free radicals and stress. In lizards, tail loss owing to predation attempts results in a stress-induced shift to a more cryptic lifestyle. In sand lizard (Lacerta agilis) males, telomere length was compromised by tail regrowth in a body size-related manner, so that small males, which already exhibit more cryptic mating tactics, were less affected than larger males. Tail regrowth just fell short of having a significant relationship with telomere length in females, and so did age in males. In females, there was a significant positive relationship between age and telomere length. We conclude that the proximate effect of compromised antipredation and its associated stress seems to have a more pronounced effect in males than in females and that age-associated telomere dynamics differ between the sexes.
PMCID: PMC2936144  PMID: 20356883
autotomy; telomere length; predation stress
2.  Consistent male–male paternity differences across female genotypes 
Biology Letters  2009;5(2):232-234.
In a recent paper, we demonstrated that male–female genetic relatedness determines male probability of paternity in experimental sperm competition in the Peron's tree frog (Litoria peronii), with a more closely related male outcompeting his rival. Here, we test the hypothesis that a male–male difference in siring success with one female significantly predicts the corresponding difference in siring success with another female. With male sperm concentration held constant, and the proportion of viable sperm controlled statistically, the male–male difference in siring success with one female strongly predicted the corresponding difference in siring success with another female, and alone explained more than 62 per cent of the variance in male–male siring differences. This study demonstrates that male siring success is primarily dictated by among-male differences in innate siring success with less influence of male–female relatedness.
PMCID: PMC2665838  PMID: 19324659
genetic compatibility; good genes; paternity; relatedness; sperm traits; amphibian
3.  Differential sex allocation in sand lizards: bright males induce daughter production in a species with heteromorphic sex chromosomes 
Biology Letters  2005;1(3):378-380.
In sand lizards (Lacerta agilis), males with more and brighter nuptial coloration also have more DNA fragments visualized in restriction fragment length polymorphism analysis of their major histocompatibility complex class I loci (and, hence, are probably more heterozygous at these loci). Such males produce more viable offspring, with a particularly strong viability effect on daughters. This suggests that females should adjust both their reproductive investment and offspring sex ratio in relation to male coloration (i.e. differential allocation). Our results show that experimental manipulation of partner coloration in the wild results in significantly higher maternal effort and a 10% higher proportion of daughters than sons. This supports the hypothesis that females increase their maternal energetic expenditure and adjust their offspring sex ratio in response to high-quality partners. However, it also suggests that this has probably evolved through natural selection for increased offspring viability (primarily through production of daughters), rather than through increased mate attraction (e.g. sexy sons).
PMCID: PMC1617163  PMID: 17148211
sex allocation; maternal allocation; male attractiveness; major histocompatibility complex; heteromorphic sex chromosomes
4.  Costly parasite resistance: a genotype-dependent handicap in sand lizards? 
Biology Letters  2005;1(3):375-377.
Male sand lizards (Lacerta agilis) with a specific restriction fragment length polymorphism fragment in their major histocompatibility complex (MHC) genotype (‘O-males’) are more resistant to ectoparasites (a tick, Ixodes ricinus) than are males that lack this fragment (‘NO-males’). However, emerging evidence suggests that such adaptive immune responses are costly, here manifested by reduced body condition and a compromised defence against secondary infections by haemoprotid parasites that use the ticks as vectors. Subsequent to tick encounter, O-males suffer from a higher leucocyte–erythrocyte ratio, and higher haemoprotid parasitaemia, in particular in relation to vector encounter rate. Furthermore, O-males (i.e. successful tick defenders) with more haemoprotid parasites remaining in their blood stream were in better body condition, whereas this did not apply in NO-males, demonstrating that the adaptive immunoreaction can—in the short term—be energetically even more costly than being moderately parasitized. In agreement with Zahavian handicap theory, O-males had a (marginally) higher reproductive success than males that lacked this fragment.
PMCID: PMC1617138  PMID: 17148210
MHC; costly parasite resistance; handicap; sand lizard

Results 1-4 (4)