Investment in mate choice depends on resource availability in female Galápagos marine iguanas (Amblyrhynchus cristatus)
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Changes in mate selectivity can significantly alter the direction and strength of sexual selection. When the direct cost of mate search increases selectivity often declines; however, little is known about how the relative cost of mate search affects investment in mate choice. Here, I investigate whether male and female Galápagos marine iguanas (Amblyrhynchus cristatus) alter their investment in mate choice behaviors when resources are limited and the relative cost of mate search is increased. Moderate resource limitation had little effect on male reproductive behavior: in both years, a similar number of males were territorial, and the mean display rate and copulation success of territorial males did not differ. In contrast, female mate search appeared to be affected by the prevailing environmental conditions. During the reproductive season following a moderate El Niño event, when food availability declined, females were in poorer body condition, assessed fewer territorial males, and mated with a male with lower relative reproductive success. Circulating hormone levels also differed between years: when resource availability was limited, receptive females had higher levels of testosterone and stress-induced corticosterone. The frequency and magnitude of climatic fluctuations are expected to increase in the future across many regions of the globe. Determining how sexual selection is shaped by changes in resource availability is vital for predicting the impact of climate change.
KeywordsMate choice Resource availability Climate change Sexual selection Galápagos marine iguana Amblyrhynchus cristatus
I would like to thank Timothy Atwood, Kelly Boyle, Gabriela Maldonado, Mark Mitchell, Michael Niemack, Mauricio Ribadeneira, James St Clair, Coral Wolf, and Lauren Young for assistance in the field, and Caroline Zawilski and Jessica Awerman for help in conducting hormone assays. Martin Wikelski, Michael Romero, David Wilcove, and Steve Pacala provided insightful comments on previous versions of the manuscript, and Mark Mitchell provided the ultrasound and trained me in its use. I am grateful to the Charles Darwin Research Station and the Galápagos National Park Service for permission and assistance while in the field, and to TAME for logistical support. This work was funded by grants from the National Science Foundation, the Society for Integrative and Comparative Biology, Sigma Xi, and Princeton University (PLAS and the EEB Department). Animal protocols used in this study were approved by Princeton University’s Animal Care and Use Committee (IACUC #1439).
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