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 2 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 2 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.
LAY SUMMARY
Telomere length (TL) may act as an integrative indicator of individual quality, which influences mating preferences and breeding success. If TL indicates individual quality, it would be expected that TL would be related to other key physiological traits linked to the individual energy balances.
We found in the Brown Booby that TL is related to mitochondrial DNA copy number (mtDNAcn), a parameter that in birds has been related to mitochondrial density and (dys)function, and to skin color, a condition-dependent sexually selected trait, but was unrelated to the individual corticosterone levels.
The probability of mate change varied greatly between 2 colonies with contrasting breeding conditions, and in both colonies, there was positive assortative mating by TL. However, the degree of assortative mating was unrelated to the probability of mate change.
Our findings suggest that TL might be an indicator of the individual quality and may influence mating patterns. Interestingly, our results highlight the importance of environmental variation on mating patterns.
Se sabe que la longitud de los telómeros (TL) covaría con un conjunto de rasgos fisiológicos involucrados en los balances energéticos que pueden influir en el éxito reproductivo. Por lo tanto, TL podría ser un indicador de la calidad del individuo, influyendo en la elección de pareja y las estrategias reproductivas. En el bobo café (Sula leucogaster), un ave marina de larga vida, investigamos en un total de 72 parejas, si la TL puede indicar el fenotipo fisiológico individual examinando cómo se relaciona con el número de copias de DNA mitocondrial (mtDNAcn) y los niveles de corticosterona (CORT). También, probamos si la TL está asociada con los patrones de apareamiento evaluando la covariación entre la TL y la coloración de la gular y las patas (un rasgo sexual dependiente de la condición), si hay apareamiento concordante por TL, y si el grado de similitud en TL entre las parejas influye en la probabilidad de que un individuo cambie de pareja entre temporadas reproductivas. Debido a que las condiciones ambientales tienen efectos importantes, el estudio se realizó en dos colonias con condiciones de reproducción contrastantes. Encontramos que la TL se relacionó positivamente con el mtDNAcn (pero no con los niveles de CORT), lo que sugiere que los individuos con telómeros más cortos pueden tener una densidad mitocondrial reducida. TL se reflejó en la coloración sexual, pero solo en la colonia con buenas condiciones para la reproducción. Encontramos apareamiento concordante positivo por TL, sin embargo, el grado de apareamiento concordante no se relacionó con la probabilidad de cambio de pareja, que varió considerablemente entre las dos colonias. Nuestros resultados sugieren que la TL se relaciona con el fenotipo fisiológico de los individuos y los patrones de reproducción. Notablemente, las condiciones ambientales contrastantes influyeron en el vínculo entre TL y la coloración sexual y la propensión de los individuos a cambiar de pareja, destacando la importancia de la variación ambiental en los patrones de reproducción.