Causes and consequences of variation in early‐life telomere length in a bird metapopulation

Abstract

Environmental conditions during early‐life development can have lasting effects shaping individual heterogeneity in fitness and fitness‐related traits. The length of telomeres, the DNA sequences protecting chromosome ends, may be affected by early‐life conditions, and telomere length (TL) has been associated with individual performance within some wild animal populations. Thus, knowledge of the mechanisms that generate variation in TL, and the relationship between TL and fitness, is important in understanding the role of telomeres in ecology and life‐history evolution. Here, we investigate how environmental conditions and morphological traits are associated with early‐life blood TL and if TL predicts natal dispersal probability or components of fitness in 2746 wild house sparrow ( Passer domesticus ) nestlings from two populations sampled across 20 years (1994–2013). We retrieved weather data and we monitored population fluctuations, individual survival, and reproductive output using field observations and genetic pedigrees. We found a negative effect of population density on TL, but only in one of the populations. There was a curvilinear association between TL and the maximum daily North Atlantic Oscillation index during incubation, suggesting that there are optimal weather conditions that result in the longest TL. Dispersers tended to have shorter telomeres than non‐dispersers. TL did not predict survival, but we found a tendency for individuals with short telomeres to have higher annual reproductive success. Our study showed how early‐life TL is shaped by effects of growth, weather conditions, and population density, supporting that environmental stressors negatively affect TL in wild populations. In addition, shorter telomeres may be associated with a faster pace‐of‐life, as individuals with higher dispersal rates and annual reproduction tended to have shorter early‐life TL.

Longitudinal telomere dynamics within natural lifespans of a wild bird

“…We have previously found no associations between nestling TL and survival in these sparrow populations, which showed high (presumably extrinsic) juvenile mortality 50 . Effects of selective disappearance of individuals with short TL and/or higher telomere shortening rates could therefore be masked by the majority of individuals having only one early-life TL measurement.…”

“…2). This suggests that the negative effects of growth 48 , environmental stressors 50 and inbreeding 86 on early-life TL previously described in these populations may have lasting effects on TL later in life 19,84 . Recent studies have found a positive genetic correlation close to 1 between TL measurements within individuals, suggesting that the same genes are involved in controlling TL at different ages 32,42,47 .…”

“…Finally, we explore factors affecting ∆TL through life in the two populations. These populations differ in the values of several key life-history traits 49 and we have previously found differences in the associations between environmental conditions and early-life TL of these two populations 50 . Furthermore, both TL and ∆TL may be sex-specific in some species 51 and TL may be negatively associated with body size in house sparrows 43,48 and in other species 16 .…”

“…Study system. This study involved two unmanipulated island populations of house sparrows in an archipelago in northern Norway that are part of a metapopulation study (see map in 50 ). Birds were monitored on Hestmannøy (66° 33′ N, 12° 50′ E) from 1994 to 2020 and on Traena (66° 30′ N, 12°05′ E) from 2004 to 2020.…”

Spatial variation in the evolutionary potential and constraints of basal metabolic rate and body mass in a wild bird

“…The study populations were included in a longterm study (e.g. Jensen et al, 2013;Kvalnes et al, 2017;Le Pepke et al, 2021;Pepke et al, 2021;Ringsby et al, 1820;Rønning et al, 2016;Stubberud et al, 2017), where a large proportion of birds (>85%) were captured annually at Leka and Vega during winters 2002-2015(Vega until 2014 and since 2012 at Lauvøya (Kvalnes et al, 2017). They have a known history of different selection regimes, as Leka and Vega were subjected to an artificial selection experiment (on tarsus length) during 2002-2005(Kvalnes et al, 2017Pepke et al, 2021;Ringsby et al, 1820).…”