Telomeres are DNA structures located at the end of chromosomes. They protect the chromosome, but shorten at each cell division. When telomeres get too short, the normal functioning of cells can be impaired. An individual’s telomere length may therefore predict its future lifespan, and understanding individual telomere dynamics could help to understand ageing in general.
Telomere shortening can be accelerated due to stress, thereby acting as a biomarker of an individual’s health status. However, some studies suggest that individual differences in telomere length are already determined at birth, and largely consistent over life.
We investigated individual telomere dynamics in a long-lived seabird, the common tern. The telomere lengths of 387 individuals, aged from 2 to 24 years, were repeatedly sampled across 10 years. We found that an individual’s telomeres shortened as they got older. Telomere shortening was also slightly increased if individuals had produced more chicks in the previous year. However, the correlation between repeated measures of an individual’s telomere length was very high, even with 6 years between measures. Nevertheless, an individual’s telomere length positively predicted its remaining lifespan, leaving the question of whether lifespan is already partly determined at the start of life.
Full article: Bichet C, Bouwhuis S, Bauch C, Verhulst S, Becker PH, Vedder O. 2019. Telomere length is repeatable, shortens with age and reproductive success, and predicts remaining lifespan in a long-lived seabird. Molecular ecology. https://doi.org/10.1111/mec.15331
The evolution of differences among females and males or sexual dimorphism (SD) is very common in animals but rare in plants. These differences emerge because there is a conflict of interests between sexes to maximize their reproductive success. Thus, moving genes of reproductive traits to low recombining regions such as the sex chromosomes might be one way to solve this conflict at the genomic level. Closely related species with young sex chromosomes, which differ in the degree of SD, are ideal systems to explore the underlining genetic architecture of SD. We have crossed a female from Silene latifolia with marked SD with a male from S. dioica with less SD. We performed a QTL analysis of reproductive and vegetative traits in the F2 hybrids to find out if sexually dimorphic traits are located on the sex chromosomes, and how they contribute to species differences. Our results support that evolutionary young sex chromosomes are important for the expression of both SD and species differences. Moreover, transgressive segregation (traits with extreme values) and a reversal of SD in the F2s indicated that SD is constrained within the species but not in the recombinant hybrids. Sexual selection can, thus, contribute to speciation.
Full article: Baena-Díaz F, Zemp N, Widmar A. 2019. Insights into the genetic architecture of sexual dimorphism from an interspecific cross between two diverging Silene (Caryophyllaceae) species. Molecular ecology. https://doi.org/10.1111/mec.15271