Persistence of Egg Recognition in the Absence of Cuckoo Brood Parasitism: Pattern and Mechanism

Abstract

Broad ecological shifts can render previously adaptive traits nonfunctional. It is an open question as to how and how quickly nonfunctional traits decay once the selective pressures that favored them are removed. The village weaverbird (Ploceus cucullatus) avoids brood parasitism by rejecting foreign eggs. African populations have evolved high levels of within-clutch uniformity as well as individual distinctiveness in egg color and spotting, a combination that facilitates identification of foreign eggs. In a companion study, I showed that these adaptations in egg appearance declined following introductions of weavers into habitats devoid of egg-mimicking brood parasites. Here, I use experimental parasitism in two ancestral and two introduced populations to test for changes in egg rejection behavior while controlling for changes in egg appearance. Introduced populations reject foreign eggs less frequently, but the ability of source and introduced populations to reject foreign eggs does not differ after controlling for the evolution of egg color and spotting. Therefore, egg rejection behavior in introduced populations of the village weaver has been compromised by changes in egg appearance, but there has been no significant decline in the birds' ability to recognize foreign eggs. This result reconciles earlier studies on this system and provides insights into the ways behavior can change over generations, especially in the context of recognition systems and the avoidance of brood parasitism.

Evolution of defences against cuckoo (Cuculus canorus) parasitism in bramblings (Fringilla montifringilla): a comparison of four populations in Fennoscandia

“…An examination of egg characteristics also supports that local adaptations do not develop in bramblings because it shows that cuckoo eggs found in Kittilä would have equal acceptance probability in non-parasitised populations (in preparation, see e.g. Lahti 2006). In this situation, widespread historical parasitism is not an absolute prerequisite for evolution of widespread defence (Gomulkiewicz et al 2000;Lenormand 2002).…”

“…2). These traits have likely evolved because they facilitate efficient and cost free egg recognition (Swynnerton 1918;Brooke and Davies 1988;Kilner 2006;Lahti 2006;Stokke et al 2007b;Moskát et al 2008a).…”

Testing the Carotenoid Trade‐Off Hypothesis in the Polychromatic Midas Cichlid, Amphilophus citrinellus

“…We assessed reflectance at 5-nm intervals over the wavelength range of 200-800 nm using a 400-mm reflection probe (R400-7; Ocean Optics). The probe was held at a 45Њ angle 5 mm from the sample (Lahti 2006;Clotfelter et al 2007). Integration time was set at 100 ms, reflectance was averaged over 100 scans, and boxcar smoothing was set to 50.…”

Pigment limitation and female reproductive characteristics influence egg shell spottiness and ground colour variation in the house sparrow (Passer domesticus)

“…For different bird taxa, this variation has been explained in the context of egg mimicry to face predation risk (e.g. Bakken et al 1978;Lloyd et al 2000;Blanco and Bertellotti 2002), to permit egg recognition in the case of brood parasitism (Stokke et al 1999(Stokke et al , 2002Davies 2000;Soler et al 2000;Lahti 2005Lahti , 2006, or more recently also in the context of sexual selection, where egg colour may signal the female's physical condition and antioxidant capacity (e.g. Moreno and Osorno 2003;Soler et al 2005;Siefferman et al 2006;Hanley et al 2008).…”