Extra‐pair paternity in a population of Chilean Swallows breeding at 54 degrees south

Abstract

ABSTRACT. Geographic patterns of variation in life-history traits have puzzled researchers for decades. However, the widely accepted idea that mating systems exhibit a tropical-temperate latitudinal trend, with extra-pair mating systems being the norm among temperate species and genetic monogamy the norm among tropical species, is supported by sparse data, particularly for birds breeding in the tropics and even more so for birds that breed in the southern hemisphere temperate zone. Our objective was to examine the genetic mating system of Chilean Swallows (Tachycineta meyeni) breeding at 54°S in Tierra del Fuego, Argentina. From 2006 to 2009, we examined the paternity of young in 52 broods. Contrary to predictions based on their congeners that breed at equivalent latitudes in the northern hemisphere, Chilean Swallows in our study had low rates of extra-pair paternity (EPP), with 13.5% of nests (N = 52) having at least one extra-pair young and 6.8% of all nestlings (N = 161) fathered by extra-pair males. These rates are also lower than those reported for species of Tachycineta swallows that breed at tropical latitudes. We found no support for a tropical-south temperate latitudinal cline in EPP rates. The highly unpredictable weather of the island of Tierra del Fuego might be influencing parental investment at this site; small clutch sizes and low EPP rates are expected if biparental attention is crucial for chick survival and reproductive success for these aerial insectivores. We argue that the sparse sampling of mating systems in birds worldwide may have contributed to a misapprehension of a global pattern. More studies of tropical and south-temperate systems are needed to build on theories based on a wider set of taxa. RESUMEN. Paternidad extra-pareja en una población de Golondrina Patagónica a los 54 grados surLos patrones de variación geográficos en rasgos de historias de vida han intrigado a los investigadores por décadas. Sin embargo, la idea ampliamente aceptada que establece que los sistemas de apareamiento presentan una tendencia latitudinal del trópico a las latitudes templadas, con sistemas de apareamiento extra-pareja siendo la norma en las especies templadas, y la monogamia genética la norma entre especies tropicales, se apoya en muy pocos datos; en especial para especies de aves que se reproducen en el trópico, y más aun para aquellas de la zona templada del hemisferio sur. Nuestro objetivo fue estudiar el sistema genético de apareamiento de la golondrina Patagónica Tachycineta meyeni a los 54°S en Tierra del Fuego, Argentina. Entre 2006-2009 examinamos la paternidad de los polluelos de 52 nidadas. Contrario a nuestras predicciones basadas en los congéneres que se reproducen en latitudes equivalentes del hemisferio norte, en nuestro estudio las golondrinas Patagónicas tienen tasas muy bajas de paternidad extra-pareja con 13.5% de nidos con por lo menos un polluelo extra-pareja (N = 52) y 6.8% de polluelos extra-pareja en la población (N = 161). Estas tasas son más bajas que las encontradas en especie...

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