Asymmetries in male aggression across an avian hybrid zone

Pearson, Scott F.; Rohwer, Sievert

doi:10.1093/beheco/11.1.93

Cited by 119 publications

(119 citation statements)

References 19 publications

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“…Male-male interactions could be the primary mechanism driving the introgression of yellow plumage if the yellow plumage is linked to advantageous behavioral traits used in male-male interactions and if such advantages lead to increased reproductive success (e.g., Kallioinen et al 1995;Rohwer and Wood 1998;Pearson and Rohwer 2000). This has been observed in other hybrid zones where there is an asymmetrical movement of a more aggressive species into the other species' range (e.g., Mallards and American black ducks, Brodsky et al 1988;black-capped and Carolina chickadees, Bronson et al 2003).…”

Section: Fig 1 (A)mentioning

confidence: 99%

Unidirectional Introgression of a Sexually Selected Trait Across an Avian Hybrid Zone: A Role for Female Choice?

Stein

2006

Evol

109

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Abstract.-Hybridization can be an evolutionary creative force by forming new polyploid species, creating novel genetic variation or acting as conduits of potentially advantageous traits between hybridizing forms. Evidence for the latter is often difficult to find because alleles under positive selection can spread rapidly across a hybrid zone and sweep to fixation. In Western Panama, an avian hybrid zone between two species of manakins in the genus Manacus exists where the unidirectional introgression of bright, yellow plumage into a white population provides evidence for the importance of hybrid zones as conduits of advantageous traits. Several lines of indirect evidence suggest that sexual selection favoring yellow plumage drives this asymmetrical spread, but more direct evidence is lacking. Along the edge of the hybrid zone, both yellow-and white-collared manakins are found in the same mating arenas or leks and compete for the same females ("mixed leks"), providing us with a unique opportunity to understand the dynamics of yellow plumage introgression. We studied these mixed leks to determine whether yellow males have a mating advantage over white males and, if so, whether the mating advantage is driven by male-male interactions, female choice, or both. We found that yellow males mated more than white males, suggesting that sexual selection favoring yellow males can, indeed, explain the spread of yellow plumage. However, we found that this advantage occurred only in mixed leks where the frequency of yellow males is greater than white males. This suggests that the advantage of yellow males may depend on the presence of other yellow males, which may slow the rate of introgression in leks where yellow frequency is low such as in areas where yellow males are beginning to colonize the white population. This, along with the geographic barrier posed by major rivers in the hybrid zone, may initially limit or slow the spread of yellow plumage. Finally, we found that yellow and white males were similar in aggression and body size, and held comparable positions within leks. Because these traits or factors are often important in or dictated by aggressive malemale interactions, these comparisons indicate that male-male interaction is not the primary mechanism for the spread of yellow plumage. However, white and yellow males received similar numbers of courtship visits from females but differed in the number of matings, suggesting that females actively rejected white in favor of yellow males. Our results indicate that sexual selection by female choice has driven the unidirectional introgression of yellow plumage into the white population, providing a mechanism for how hybrid zones act as conduits of novel and advantageous traits.

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Section: Fig 1 (A)mentioning

confidence: 99%

Unidirectional Introgression of a Sexually Selected Trait Across an Avian Hybrid Zone: A Role for Female Choice?

Stein

2006

Evol

109

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“…An additional complicating factor in studies of hybrid fitness is that the strength of selection to avoid hybridization may differ for each of the hybridizing species Pearson 2000;Pearson and Rohwer 2000;Tiffin et al 2001;Veen et al 2001). For example, hybrid fitness may be intermediate between parental types Pearson 2000;Pearson and Rohwer 2000), such as when traits associated with fitness exhibit additive genetic variance.…”

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confidence: 99%

“…For example, hybrid fitness may be intermediate between parental types Pearson 2000;Pearson and Rohwer 2000), such as when traits associated with fitness exhibit additive genetic variance. In such cases, selection may favor hybridization by one species but not the other.…”

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Differential Selection to Avoid Hybridization in Two Toad Species

Pfennig

Simovich

2002

Evolution

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Abstract. The fitness consequences of hybridization critically affect the speciation process. When hybridization is costly, selection favors the evolution of prezygotic isolating mechanisms (e.g., mating behaviors) that reduce heterospecific matings and, consequently, enhance reproductive isolation between species (a process termed reinforcement). If, however, selection to avoid hybridization differs between species, reinforcement may be impeded. Here, we examined both the frequency and fitness effects of hybridization between plains spadefoot toads (Spea bombifrons) and New Mexico spadefoot toads (S. multiplicata). Hybridization was most frequent in smaller breeding ponds that tend to be ephemeral, and heterospecific pairs consisted almost entirely of S. bombifrons females and S. multiplicata males. Moreover, in controlled experimental crosses, hybrid offspring from crosses in which S. multiplicata was maternal had significantly lower survival and longer development time than pure S. multiplicata offspring. By contrast, hybrid offspring from crosses in which S. bombifrons was maternal outperformed pure S. bombifrons offspring by reaching metamorphosis faster. These data suggest that, although S. multiplicata females are under selection to avoid hybridization, selection might favor those S. bombifrons females that hybridize with S. multiplicata if their breeding pond is highly ephemeral. Generally, the strength of selection to avoid hybridization may differ for hybridizing species, possibly impeding reinforcement. Speciation by reinforcement is a potentially important means by which populations become reproductively isolated. When hybridization by two sympatric species produces offspring that have lower fitness than pure-species types, selection can lead to the evolution of premating isolating barriers (e.g., mating behaviors) that reduce hybridization

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“…If the fraction of the population 'invading' the other subspecies' range is the same then absolute numbers of schoeniclus invading (i.e., singing versus) intermedia should largely exceed those of intermedia invading (i.e., singing versus) schoeniclus. In this case, responding to both songs would be the adaptive behaviour of the individual intermedia male, as is the case in European and Iberian chiffchaffs or North American warblers (Salomon, 1989;Pearson & Rohwer, 2000). The persistence of intermedia as a separate subspecies could therefore be due to the fact that the behaviour of the males of the subspecies, i.e.…”

Section: Discussionmentioning

confidence: 96%

“…Martens, 1996;Grant & Grant, 1997; but see Baptista & Trail, 1992). Playback experiments in species with subspecies-characteristic song have shown differences in reaction to different subspecies songs {Sylvia curruca ssp., Martens & Steil, 1997; Zonotrichia leucophrys ssp., Petrinovich & Patterson, 1981;Lampe & Baker, 1994; Dendroica occidentalis and D. townsendi, Pearson & Rohwer, 2000). The chiffchaff subspecies complex {Phylloscopus collybita ssp.)…”

Section: Introductionmentioning

confidence: 99%

Subspecies song discrimination in a Mediterranean population of the reed buntingEmberiza schoeniclus intermedia

Matessi¹,

Dabelsteen²,

Pilastro³

2001

Italian Journal of Zoology

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Song represents one of the possible key factors influencing the interaction among songbird populations and can affect their evolution. We studied the effect of song differences between morphologically different subspecies of the reed bunting {Emberiza schoeniclus) on the territorial behaviour of males of the Mediterranean subspecies E. s. intermedia. Twenty males were presented with playback of different songs belonging to either their own or to the foreign subspecies, northern European E. s. schoeniclus, and their response behaviour was recorded. Both treatments elicited an aggressive approach to the loudspeaker, but the response to the foreign playback was slightly weaker. We conclude that the response of intermedia males seems close to that expected if the members of a demographically inferior subspecies need to defend resources from another, more abundant, subspecies. However, the hypothesis of song as an effective barrier between subspecies in territorial defence cannot be excluded.KEY WORDS: Playback experiments -Pre-mating barrier -Bill morphology -Territorial behaviour. ACKNOWLEDGEMENTS

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Asymmetries in male aggression across an avian hybrid zone

Cited by 119 publications

References 19 publications

Unidirectional Introgression of a Sexually Selected Trait Across an Avian Hybrid Zone: A Role for Female Choice?

Unidirectional Introgression of a Sexually Selected Trait Across an Avian Hybrid Zone: A Role for Female Choice?

Differential Selection to Avoid Hybridization in Two Toad Species

Subspecies song discrimination in a Mediterranean population of the reed buntingEmberiza schoeniclus intermedia

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