Artículo de revista
A blurring of life-history lines: Immune function, molt and reproduction in a highly stable environment
Fecha
2015Registro en:
General and Comparative Endocrinology 213 (2015) 65–73
Autor
Merrill, Loren
González Gómez, Paulina L.
Ellis, Vincenzo A.
Levin, Iris I.
Vásquez Salfate, Rodrigo
Wingfield, John C.
Institución
Resumen
Rufous-collared sparrows (Zonotrichia capensis peruviensis) from valleys in the Atacama Desert of Chile,
live in an extremely stable environment, and exhibit overlap in molt and reproduction, with
valley-specific differences in the proportion of birds engaged in both. To better understand the mechanistic
pathways underlying the timing of life-history transitions, we examined the relationships among
baseline and stress-induced levels of corticosterone (CORT), testosterone, and bacteria-killing ability of
the blood plasma (BKA), as well as haemosporidian parasite infections and the genetic structure of two
groups of sparrows from separate valleys over the course of a year. Birds neither molting nor breeding
had the lowest BKA, but there were no differences among the other three categories of
molt-reproductive stage. BKA varied over the year, with birds in May/June exhibiting significantly lower
levels of BKA than the rest of the year. We also documented differences in the direction of the relationship
between CORT and BKA at different times during the year. The direction of these relationships coincides
with some trends in molt and reproductive stage, but differs enough to indicate that these birds
exhibit individual-level plasticity, or population-level variability, in coordinating hypothalamo–pitui
tary–adrenal axis activity with life-history stage. We found weak preliminary evidence for genetic differentiation
between the two populations, but not enough to indicate genetic isolation. No birds were
infected with haemosporidia, which may be indicative of reduced parasite pressure in deserts. The data
suggest that these birds may not trade off among different life-history components, but rather are able to
invest in multiple life-history components based on their condition.