Inbreeding, immune defence and ectoparasite load in different mockingbird populations and species in the Galápagos Islands

Abstract

Inbreeding may impair an individual's immune system, render it more susceptible to disease and hence contribute to the extinction risk of small and isolated populations, as often found on islands. So far, surprisingly few studies have assessed the effects of inbreeding on immunocompetence in wild populations. Using 26 microsatellite loci and genetic data from museum specimens and contemporary samples, we calculated short-term and long-term inbreeding in 13 different mockingbird populations covering the range of all 4 species in the Galapagos Islands and compared them with three different measures of innate immunity and ectoparasite load. We found no significant effect of either measure of inbreeding on natural antibody or complement enzyme titres, heterophil-lymphocyte ratio or feather louse abundance. Hence, our results do not support a link between inbreeding and immunocompetence. However, overall statistical power and repeatabilities of antibody and complement enzyme titres were low. Nevertheless, generally, natural antibody titres were high suggesting that the mockingbirds may be equipped with a strong first line of defence, as found in other island species.

Balancing selection and genetic drift create unusual patterns of MHCIIβ variation in Galápagos mockingbirds

“…). All individuals from Galápagos and the mainland were genotyped at 26 microsatellite loci following previously established protocols (Hoeck & Keller ), using primers that were designed based on four individuals from three GM populations (Hoeck et al . ).…”

“…DNA extraction was performed as described previously (Hoeck et al 2009). All individuals from Gal apagos and the mainland were genotyped at 26 microsatellite loci following previously established protocols (Hoeck & Keller 2012), using primers that were designed based on four individuals from three GM populations (Hoeck et al 2009). For 12 of the islands, the microsatellite data were adopted from Hoeck & Keller (2012).…”

“…All individuals from Gal apagos and the mainland were genotyped at 26 microsatellite loci following previously established protocols (Hoeck & Keller 2012), using primers that were designed based on four individuals from three GM populations (Hoeck et al 2009). For 12 of the islands, the microsatellite data were adopted from Hoeck & Keller (2012). New microsatellite genotypes for this study were generated for the population of M. parvulus from Pinta and for M. polyglottos using the same primers as in Hoeck & Keller (2012).…”

Observed variation in the heterophil to lymphocyte ratio values of birds undergoing investigation of health status

“…Typically, a suite of haematological analytes are assessed (Fudge 2000) and many publications have reported the haematological characteristics of both healthy birds (Howlett et al 1995;Samour et al , 2005Samour et al , 2010Spagnolo et al 2006Spagnolo et al , 2008Black et al 2013) and birds with disorders of health (Hawkey et al 1983(Hawkey et al , 1984aD'Aloia et al 1994;Samour and Peirce 1996;Bienzle et al 1997;Bienzle and Smith 1999;Jaensch and Clark 2004;Tell et al 2004;Clark et al 2013a, b). Analysis of blood has also been incorporated in many physiological and ecological studies of birds (Ots and Hõrak 1996;Ots et al 2001Ots et al , 2002Hanssen et al 2005;Eeva et al 2005;Artacho et al 2007;Parejo et al 2007;Fokidis et al 2008;Buehler et al 2008;Newbrey and Reed 2009;Norte et al 2009;Vinkler et al 2010;Bried et al 2011;Lobato et al 2011;Cirule et al 2012;Hoeck and Keller 2012;Müller et al 2011;Hegemann et al 2012;Zylberberg et al 2012). Examination of Romanowsky-stained blood films, using light microscopy, has been the most frequently adopted haematological technique, commonly for determination of the heterophil to lymphocyte ratio (H/L) (Ots and Hõrak 1996;Ots et al 2001Ots et al , 2002…”

“…Analysis of blood has also been incorporated in many physiological and ecological studies of birds (Ots and Hõrak 1996;Ots et al 2001Ots et al , 2002Hanssen et al 2005;Eeva et al 2005;Artacho et al 2007;Parejo et al 2007;Fokidis et al 2008;Buehler et al 2008;Newbrey and Reed 2009;Norte et al 2009;Vinkler et al 2010;Bried et al 2011;Lobato et al 2011;Cirule et al 2012;Hoeck and Keller 2012;Müller et al 2011;Hegemann et al 2012;Zylberberg et al 2012). Examination of Romanowsky-stained blood films, using light microscopy, has been the most frequently adopted haematological technique, commonly for determination of the heterophil to lymphocyte ratio (H/L) (Ots and Hõrak 1996;Ots et al 2001Ots et al , 2002Parejo et al 2007;Newbrey and Reed 2009;Norte et al 2009;Hoeck and Keller 2012) and less frequently as part of a broader assessment of avian haematological characteristics (Vinkler et al 2010;Bried et al 2011;Hegemann et al 2012).…”