Abstract
Identifying associations between phenotypes and environmental parameters is crucial for understanding how natural selection acts at the individual level. In this context, genetically isolated populations can be useful models for identifying the forces selecting fitness-related traits. Here, we use a comprehensive dataset on a genetically and ecologically isolated population of the strictly marine bird, the brown booby Sula leucogaster, at the tropical and remote Saint Peter and Saint Paul Archipelago, mid-Atlantic Ocean, in order to detect phenotypic adjustments from interindividual differences in diet, foraging behaviour, and nest quality. For this, we took biometrics of all individuals of the colony breeding in 2014 and 2015 and tested their associations with nest quality, diet parameters, and foraging behaviour. While body size was not related to the foraging parameters, the body size of the females (responsible for nest acquisition and defence) was significantly associated with the nest quality, as larger females occupied high-quality nests. Our findings suggest that the small breeding area, rather than prey availability, is a limiting factor, emphasizing the role of on-land features in shaping phenotypic characteristics and fitness in land-dependent marine vertebrates.
Highlights
Identifying associations between phenotypes and environmental parameters is crucial for understanding how natural selection acts at the individual level
All the seven prey items were identified to the species level, and the tropical two-wing flyingfish Exocoetus volitans was the most important prey item (PSIRI = 62.8%), followed by the bigwing halfbeak Oxyporhamphus micropterus (Table 1; Supplementary Fig. 1)
Significant differences in the mean body size were detected between the females nesting in low and high-quality nests, but associations of diet and foraging trip parameters with body size of both genders were not observed
Summary
Identifying associations between phenotypes and environmental parameters is crucial for understanding how natural selection acts at the individual level. Combining traditional and innovative techniques makes it possible to investigate natural selection, even in free-living animals, such as seabirds Despite their high mobility, seabirds are known to contain population structure associated with colony-specific environmental conditions[16,17], presenting gene flow disruption even between sympatric populations[18]. Seabirds are known to contain population structure associated with colony-specific environmental conditions[16,17], presenting gene flow disruption even between sympatric populations[18] In this context, genetically isolated seabird populations arise as interesting models for testing individual quality and detecting fitness-related traits due to their high intraspecific diversity, high philopatry, colonial breeding, and dependence on resource availability around colonies[19]
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