Mate selection based on labile traits affects short-term fitness in a long-lived seabird

Abstract

In long-lived monogamous social species, partner compatibility can play a crucial role in reproductive success. We evaluated assortative mating based on body condition (plasma triglyceride concentration), diet (δ 15 N), and foraging habitat (δ 13 C) in the blue-footed booby Sula nebouxii, a long-lived monogamous seabird. We investigated the effects of assortative mating (sum of triglycerides in a pair) and asymmetry within pairs (residuals from regression of female-male triglycerides) on reproductive performance and offspring growth (alkaline phosphatase, ALP). We found that strong assortative mating determined by body condition and diet seemed to be related to a signalling mechanism (nutritional state). This mating pattern had a substantial effect on the breeding parameters and influenced offspring ALP. Within-pair asymmetry did not influence any reproductive parameters, but the ALP of offspring was related to the within-pair relative female condition. Overall, our results indicate that individuals seek the best possible match to maximize their breeding investment and/or individuals are limited in their mate options by their current body condition, which has consequences for offspring fitness in the short term. Our findings show that assortative mating based on body condition produces notable variation in the joint condition of the pair, which determines their breeding success.

Nutritional state variations in a tropical seabird throughout its breeding season

“…Plasma metabolites are commonly used as indicators of individual quality, a term that is linked to long-term heterogeneity between individuals (Wilson and Nussey 2010 ). Previous studies in Blue-footed Boobies confirmed a relationship between female triglyceride concentrations (sampled during courtship) and the summed triglycerides of a pair to their reproductive performance (González-Medina et al 2018 ; 2020 ). González-Medina et al ( 2020 ) also found a correlation between the summed triglycerides of a pair measured during courtship and those measured during chick-rearing.…”

“…In a related species, the Australasian gannet ( Morus serrator ), each sex targeted prey that differs in nutrient content (Machovsky-Capuska et al 2016 ). However, previous studies found no dietary segregation between the sexes in Blue-footed boobies (González-Medina et al 2017 , 2020 ). Nevertheless, it is possible that females have a higher assimilation rate during the pre-laying period and are freer to forage than males due to their differential breeding roles, thus foraging at specific areas and prey species to satisfy their nutritional needs.…”

“…Body condition may affect the foraging decisions of animals (Saraux et al 2011 ), and the nutritional state of individuals may be decisive for animals to reproduce or not, and how much to invest in any given reproductive attempt (Wendeln and Becker 1996 ; Ellis et al 2000 ; Dehnhard et al 2015 ; González-Medina et al 2020 ). In long-lived species such as seabirds, which can breed for many years, adults should carefully trade-off their survival with reproductive investment (sensu ‘the prudent parent hypothesis’; Drent and Daan 1980 ).…”

“…Although seabirds have been extensively used as model species to investigate breeding investment strategies based on body condition and individual quality (e.g. Weimerskirch 1998 ; Jenouvrier et al 2018 ; González-Medina et al 2020 ), information on the individual variation of the nutritional state of seabirds throughout breeding is limited. In one example, adult Scopoli’s shearwaters Calonectris diomedea showed distinct patterns of body mass and plasma metabolites as indicators of nutritional state throughout the breeding season from egg formation to chick-rearing (Navarro et al 2007 ).…”

“…Therefore, it has been suggested that males operate at a physiological maximum (Velando and Alonso-Alvarez 2003 ) but can adjust their parental care and foraging according to the demands of chicks (González-Medina et al 2015 ). Previous research indicated that body condition and plasma triglyceride concentrations affect mate choice in Blue-footed boobies, i.e., pairs mated assortatively based on these traits (González-Medina et al 2020 ). Further, elevated plasma triglyceride concentrations in females were linked to a high-quality diet and increased breeding performance (González-Medina et al 2018 ).…”