Telomere length in relation to colour polymorphism across life stages in the tawny owl

Abstract

Telomere erosion has been proposed to be tightly associated with senescence, environmental stressors and life history trade‐offs. How telomere dynamics vary across life stages and especially in relation to (heritable) phenotypic traits is still unclear. The tawny owl Strix aluco display a highly heritable melanin‐based colour polymorphism, a grey and a brown morph, linked to several fitness traits including morph‐specific telomere dynamics. As adults, brown tawny owls have shorter relative telomere length (RTL) and exhibit faster telomere shortening rate than grey owls. Here we test if these morph‐specific telomere dynamics emerge already during growth, or if they are induced only in adult life through differential physiological costs associated with the life history of the morphs. We analysed RTL from 287 tawny owl offspring and 81 first breeding adults to evaluate at what life stage morph‐specific patterns emerge. We found no differences in RTL between the two morphs during the nestling period nor at the first breeding attempt. Sex, brood size or size rank in the nest did not affect offspring RTL. Among first‐breeders, females had shorter telomeres than males suggesting a sampling‐time dependent difference in reproductive costs between sexes, due to the prominent sex roles in tawny owls in the early nestling period. The probability to return to breed after the first breeding attempt was not affected by RTL, sex or colour morph. The lack of morph‐specific difference in RTL among nestlings and first breeders suggests that previously observed morph‐specific differences in RTL dynamics in adults emerge at the onset of the breeding career and is likely due to different physiological profiles and life‐history strategies adopted by adults. We conclude that different telomere dynamics and senescence patterns among highly heritable phenotypes (colour morphs) are likely to be a result of differential costs of reproduction and self‐maintenance.

Pleiotropic effects of melanin pigmentation: haemoparasite infection intensity but not telomere length is associated with plumage morph in black sparrowhawks

“…Several studies have suggested that plumage polymorphism may be associated with differences in telomere length [ 39 – 41 ]. However, in the black sparrowhawk, we did not find any significant difference in RTL between light and dark morph birds.…”

“…Furthermore, melanin pigmentation is linked to telomere dynamics in several bird species [ 39 , 40 ]. For example, adult rufous morph tawny owls with more pheomelanin in their plumage have shorter telomeres than grey morphs and experience faster telomere shortening [ 39 , 41 ]. In the same species, haemoparasite infection status was also associated with shorter telomeres [ 39 ], and morph-specific differences in lifespan were also detected, with grey morphs having higher survival rates and higher lifetime reproductive output under harsh winter conditions [ 42 , 43 ].…”

“…Thus, there may be a link between melanin pigmentation and telomere dynamics mediated through the pleiotropic effects of genes involved in the melanin production pathway [ 3 ]. Melanin biosynthesis can cause an increase in reactive oxygen species [ 41 , 44 ], which may cause telomere shortening through increased oxidative stress [ 45 , 46 ]. Indeed, it has been found that an increase in antioxidants in the diet can reduce pathogen-induced telomere attrition in certain species [ 47 ].…”

Sex allocation is color morph-specific and associated with fledging condition in a wild bird

“…DNA was extracted during spring 2019 from the blood samples using an ammonium acetate (NH 4 Ac) protocol for avian blood (adapted from Nicholls et al 2000 ; see methods in Morosinotto et al 2021 ). Briefly, a small piece of dried blood was collected and placed in a tube with 125 μl of SET buffer; for samples collected in 2019, 125 μl of SET buffer and sample were selected.…”

Cold winters have morph-specific effects on natal dispersal distance in a wild raptor

“…During nestling growth, food requirements are morph-specific as gray offspring grow relatively better and mount higher immune responses under adverse food conditions and brown ones grow better and mount higher immune responses under favorable food conditions ( Piault et al 2009 ). The color morphs also reflect distinct physiological profiles in adulthood because brown tawny owls molt more primaries than gray ones ( Karell et al 2013 ), show higher costs of immune defense ( Gasparini et al 2009 , Karell et al 2011a ) and a faster rate of cellular senescence than gray ones ( Karell et al 2017 , Morosinotto et al 2021 ).…”