In the common yellowthroat the “mask” (the black band across the eyes) varies in
ID: 121515 • Letter: I
Question
In the common yellowthroat the “mask” (the black band across the eyes) varies in size among males. A study by Dunn and colleagues (Evolution, Volume 67, Issue 3, pages 679–687, March 2013) found that male mask size is correlated with genetic diversity at the MHC loci, which are important for immune responses (their figure 1, which is copied below). They also found that male mask size is correlated with male resistance to Plasmodium (malaria) parasites.
a.) Based on this knowledge, what would you predict about female mate choice in this system and why?
b.) Separate research has also shown that males with larger masks provide less parental care. How does this information change your answer for part 1? Do you expect a high proportion of extrapair copulations in common yellowthroats?
Explanation / Answer
a. In appearance females are similar to males, but they have paler underparts and also they lack the black mask. Females and young yellowthroats do not have a mask. Immature birds are same in appearance like that of the adult female. Females who lack in mask, are brownish olive from above and buffy from below. They have some yellow especially on the throat. Also they have a faint buffy eye ring. Yellowthroats live in grassy marshes, or in wet meadows or thickets. Female mask size is not correlated like that of male. But they have more resistance to Plasmodium (malaria) parasites.
b. Parental hypothesis predict that males with larger masks will be providing more care while the another hypothesis i.e. differential allocation and trade-off hypotheses tells that they will be providing less care. The relationship between male ornamentation and parental care in two populations of common yellowthroats where the sexually selected male ornament differs implies that more ornamented males provided less parental care in both populations, contrary to the good parent hypothesis. As, females did not feed their nestlings more frequently when mated with more masked males and this is an additional prediction of the differential allocation hypothesis. While the trade-off hypothesis suggests that more ornamented males provide less care because they spend more of their effort in comparision to females in pursuing extrapair mates or defending their territories from other males.