View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Royal Holloway - Pure Convergent evolution of reduced eggshell conductance in avian brood parasites Stephanie C. McClelland1*, Gabriel A. Jamie2,3, Katy S. Waters1, Lara Caldas1, Claire N. Spottiswoode2,3 and Steven J. Portugal1 1School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK. 2Department of Zoology, University of Cambridge, Downing Street, University of 10 Cambridge, Cambridge CB2 3EJ, UK. 3FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, Cape Town, South Africa. Subject Areas: evolution, parasitism, physiology Keywords: Cuculidae, eggs, gas exchange, Indicatoridae, Viduidae Author for Correspondence: Stephanie C. McClelland, email:
[email protected] 20 1 Abstract Brood parasitism has evolved independently in several bird lineages, yet these species 30 share many similar physiological traits that optimise this breeding strategy, such as shorter incubation periods and thicker eggshells. Eggshell structure is important for embryonic development as it controls the flux of metabolic gases, such as O2, CO2 and H2O, into and out of the egg; in particular, water vapour conductance (GH2O) is an essential process for optimal development of the embryo. Previous work has shown that common cuckoos (Cuculus canorus) have a lower than expected eggshell GH2O compared to their hosts. Here we sought to test whether this is a trait found in other independently-evolved avian brood parasites, and therefore reflects a general adaptation to a parasitic lifestyle. We analysed GH2O for seven species of brood parasites from four unique lineages as well as for their hosts, and combined this with species 40 from the literature.