Ontogenic differences in sexual size dimorphism across four plover populations.

Natalie Dos Remedios,András Kosztolányi,Clemens Küpper,Patricia L M Lee,Tamás Székely,Jeroen Reneerkens

doi:10.1111/ibi.12263

Natalie Dos Remedios, András Kosztolányi + Show 4 more

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https://doi.org/10.1111/ibi.12263

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Abstract

Sexual size dimorphism (SSD) among adults is commonly observed in animals and is considered to be adaptive. However, the ontogenic emergence of SSD, i.e. the timing of divergence in body size between males and females, has only recently received attention. It is widely acknowledged that the ontogeny of SSD may differ between species, but it remains unclear how variable the ontogeny of SSD is within species. Kentish Plovers Charadrius alexandrinus and Snowy Plovers C. nivosus are closely related wader species that exhibit similar, moderate (c. 4%), male‐biased adult SSD. To assess when SSD emerges we recorded tarsus length variation among 759 offspring in four populations of these species. Tarsus length of chicks was measured on the day of hatching and up to three times on recapture before fledging. In one population (Mexico, Snowy Plovers), males and females differed in size from the day of hatching, whereas growth rates differed between the sexes in two populations (Turkey and United Arab Emirates, both Kentish Plovers). In contrast, a fourth population (Cape Verde, Kentish Plovers) showed no significant SSD in juveniles. Our results suggest that adult SSD can emerge at different stages of development (prenatal, postnatal and post‐juvenile) in different populations of the same species. We discuss the proximate mechanisms that may underlie these developmental differences.

Highlights

Sexual size dimorphism (SSD) among adults is commonly observed in animals and is considered to be adaptive
Despite numerous studies focusing on patterns of adult SSD, research has only recently focused on the ontogenic development of SSD (Badyaev et al 2001a, Blanckenhorn et al 2007, Dietrich-Bischoff et al 2008, Hegyi et al 2011, Klenovsek & Krystufek 2013)
In Ceuta and Al Wathba, the tarsus length of hatchlings varied over time: in Ceuta, chicks hatching in 2008 had shorter tarsi than those hatching in other years of the study and in Al Wathba, tarsus length was shorter among those hatching later in the season (b = À0.631 Æ 0.120; Fig. 2a)

Summary

Introduction

Sexual size dimorphism (SSD) among adults is commonly observed in animals and is considered to be adaptive. SSD may emerge during three main stages: (i) prenatally, due to sex differences in embryonic growth rates resulting either from intrinsic genetic differences (Godfrey & Farnsworth 1952, Sellier 2000) or from differences in maternal investment in male and female embryos (Mu€ller et al 2012, Helle et al 2013); (ii) postnatally, due to sex differences in the rate or duration of growth of offspring (Leigh & Shea 1995, Blanckenhorn 2005, Hasumi 2010, Zhang & Liu 2013), which may be hormone-mediated (e.g. linked to differential testosterone and activity levels; Klukowski et al 2004, Cox et al 2009); or (iii) post fledging, due either to sex differences in continued growth, or to mortality differences between juvenile or adult males and females in relation to body size (Badyaev et al 2001a, Kersten & Brenninkmeijer 2008). It remains unclear whether population differences in the ontogenic growth patterns of males and females might occur in species where adult SSD is consistent across populations

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