Telomere length links with physiological phenotype and breeding patterns in a long-lived seabird

Telomere length (TL) is known to covary with a suite of physiological
traits involved in energy balances that may influence breeding success.
Thus, TL may be an indicator of individual-quality, influencing mate
choice and breeding strategies. In the brown booby (Sula leucogaster), a
long-lived seabird, we investigated in a total of 72 pairs, whether TL may
indicate the individual physiological phenotype by examining how it
relates to mitochondrial DNA copy number (mtDNAcn) and corticosterone
(CORT) levels. Then, we tested if TL is associated with mating patterns by
looking for covariation with skin coloration (a condition-dependent sexual
trait), whether there is assortative mating by TL, and if the degree of TL
similarity between partners influences an individual’s likelihood of
changing mates between reproductive seasons. Because environmental
conditions can have important effects on the condition and reproductive
strategies of individuals, the study was performed in two colonies with
contrasting breeding conditions. We found that TL was positively related
to mtDNAcn (but not CORT levels), suggesting that individuals with shorter
telomeres may have a reduced mitochondrial density. TL was reflected in
sexual coloration, but only in the colony with good breeding conditions.
There was positive assortative mating by TL, however, the degree of
assortative mating was unrelated to the probability of mate change, which
greatly varied between the two colonies. Our results suggest that TL is
associated with the physiological phenotype of individuals and their
breeding patterns. Importantly, contrasting environmental conditions
influenced the link between TL and sexual coloration and the propensity of
individuals to change mate, highlighting the importance of environmental
variation on mating patterns.