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Theoretical models suggest that males should adjust their parental effort according to paternity when parental effort is costly, paternity varies among clutches, and males have a cue to assess paternity. To date, nearly all tests of this theory have been conducted using birds as model organisms. In this study we examined these three factors and the relationship between paternity and male parental care in a fish system. In the pumpkinseed sunfish (Lepomis gibbosus), parental care is provided exclusively by males (parentals), but some males (sneakers) parasitize others by sneaking fertilizations. Parental males significantly lost weight during the parental care period. Clutch size and amount of parental effort did not affect a male's probability of obtaining more eggs. Paternity was variable among broods. The proportion of young sired by a parental male was not associated with frequency of fanning eggs or defense of hatched young, but was positively correlated with levels of nest defense during the egg stage. Egg survivorship might restrict an adjustment of fanning behavior, and a general decline in parental behavior (with brood age) might explain the lack of adjustment once the eggs hatch. Parental males did not adjust their care when we experimentally manipulated one possible cue of paternity. Together, these results indicate that male pumpkinseeds do adjust their care in relation to paternity, but the cues used to assess paternity are not clear. [ABSTRACT FROM AUTHOR]

Extrapair fertilizations complicate our understanding of cooperative breeding in a number of ways. For example, auxiliaries may reduce the costs of seeking extrapair fertilizations for breeding males or females, and auxiliary males may themselves seek copulations with the breeding female in their own group. We employed microsatellite markers to examine patterns of parentage in the cooperatively breeding splendid fairy-wren (Malurus splendens melanotus). Our study population exhibited a relatively high level of extrapair paternity (42% of 386 offspring) with considerable annual variation (range = 24–52%). Across years the proportion of offspring sired by extrapair males was significantly correlated with the average number of auxiliaries per group. Furthermore, the proportion of extrapair young within a brood was related to group composition; groups with multiple auxiliaries were twice as likely as groups with zero or one auxiliary to contain extrapair young. Most offspring were sired by dominant breeding males, but auxiliary males sired approximately 25% of all extrapair young (10% of all offspring), and about half of these were cases in which the auxiliary male sired offspring in his own group. Within-group sirings by auxiliary males were most common after replacement of the breeding female, and they also appeared to be more likely when the auxiliary was not related to the breeding male. Thus, the presence of auxiliary males increased the likelihood that females would produce extrapair young, and although incest avoidance mechanisms usually prevent within-group copulations by auxiliary males, a conflict of interest among group males arises when a new female joins the group. [ABSTRACT FROM AUTHOR]

In many socially monogamous birds, males maintain close proximity to their mates during the fertile period. This is often considered an effort on the male's part to prevent other males from copulating with his mate, but other functions have been suggested and the effectiveness of males in preventing extrapair fertilizations has come into question. Moreover, it is unclear whether mate guarding conflicts with other male activities, particularly the pursuit of extrapair fertilizations. We examined mate guarding by male black-throated blue warblers (Dendroica caerulescens). Behavioral observations showed that males that guarded their mates more closely were less likely to have extrapair young in their nests. Moreover, the experimental detention of a male for 1 h during the fertility risk period increased the probability that a brood would contain extrapair young. Thus, male mate guarding was effective in reducing the risk of extrapair fertilization. Males with many opportunities for extrapair copulations appeared to guard their mates less and consequently had more extrapair young in their broods than males with few such opportunities. This suggests that mate guarding may conflict with the pursuit of extrapair fertilizations. [ABSTRACT FROM AUTHOR]

Few studies of avian mating systems have identified the sires of extrapair young, and hence it has been difficult to determine the scale at which reproductive interactions occur. For instance, females may be free to copulate with any male in the population (a “global” scale of interactions), or females may be restricted to copulating only with males on neighboring territories (a “local” scale). The scale of such interactions has important consequences for an understanding of the evolutionary causes and consequences of extrapair fertilizations. We used five hypervariable microsatellite loci and multilocus DNA fingerprinting to examine parentage of more than 400 nestling black-throated blue warblers (Dendroica caerulescens). Extrapair fertilizations were common, and the microsatellite markers allowed us to identify the sires for 89% of the young analyzed. Most identified extrapair sires were males on neighboring or nearby territories, and most nestlings for whom we could not identify a sire came from territories at the edge of the study plot. Thus, reproductive interactions appear to be more local than global in this population. Extrapair fertilizations contributed significantly to total variation in male reproductive success. However, the standardized variance in male reproductive success (0.68-0.74) was not substantially greater than that for females (0.53-0.60), and the contribution of extrapair fertilizations (9-14%) was much lower than the contribution of within-pair fertilizations (75-77%). This suggests that the local scale of reproductive interactions may limit variation in male reproductive success and hence the opportunity for selection. [ABSTRACT FROM AUTHOR]