Female plumage polymorphism is rare in hummingbirds

Clark, Christopher J.; Robinson, Barbara; Remsen, J. V.

doi:10.1007/s10336-022-01975-4

Cited by 5 publications

(2 citation statements)

References 24 publications

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“…Furthermore, we found that instances of dichromatic species where the female is the colourful sex are rare (electronic supplementary material, figure S3). It has been suggested that females of many hummingbird species exhibit plumage polymorphism—including a ‘male-like’ morph [49,83], but the phenomenon has only been confirmed for three species [84,85]. Hence, one possible hypothesis is that increased dichromatism in high-elevation mixed and open habitats is the result of enhanced visibility [29] and relaxed predation pressure against colourful plumage.…”

Section: Discussionmentioning

confidence: 99%

The evolution of sexually dimorphic traits in ecological gradients: an interplay between natural and sexual selection in hummingbirds

et al. 2022

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Traits that exhibit differences between the sexes have been of special interest in the study of phenotypic evolution. Classic hypotheses explain sexually dimorphic traits via intra-sexual competition and mate selection, yet natural selection may also act differentially on the sexes to produce dimorphism. Natural selection can act either through physiological and ecological constraints on one of the sexes, or by modulating the strength of sexual/social selection. This predicts an association between the degree of dimorphism and variation in ecological environments. Here, we characterize the variation in hummingbird dimorphism across ecological gradients using rich databases of morphology, colouration and song. We show that morphological dimorphism decreases with elevation in the understorey and increases with elevation in mixed habitats, that dichromatism increases at high altitudes in open and mixed habitats, and that song is less complex in mixed habitats. Our results are consistent with flight constraints, lower predation pressure at high elevations and with habitat effects on song transmission. We also show that dichromatism and song complexity are positively associated, while tail dimorphism and song complexity are negatively associated. Our results suggest that key ecological factors shape sexually dimorphic traits, and that different communication modalities do not always evolve in tandem.

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Section: Discussionmentioning

confidence: 99%

The evolution of sexually dimorphic traits in ecological gradients: an interplay between natural and sexual selection in hummingbirds

et al. 2022

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“…As the inference came from museum specimens spanning many geographical localities, and this genus is highly geographically variable, verifying that there are multiple female types from the same population is needed. The dearth of records of male-plumaged birds attending a nest suggests female plumage polymorphism is rare in hummingbirds [15], since male-plumaged females would, at first pass, be mistaken for an actual male. The discovery of any hummingbird species in which male-plumaged birds (whether actually male or female) attended a nest would be highly interesting for further study.…”

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confidence: 99%

Invited commentary on 'intersexual social dominance mimicry drives female hummingbird polymorphism'

Clark

2022

Proc. R. Soc. B.

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In a new study, Falk et al. [1] examine the white-necked Jacobin (Florisuga mellivora). This hummingbird is unique among hummingbirds in that it has female polymorphism [2]. Females come in two distinctive morphs: in the Panamanian population they studied, roughly 80% of females are dull-plumaged and dissimilar to males, while 20% of females have the same bright plumage of males, making them indistinguishable from males visually [3], although slight dimorphism in morphology permits identification of females in the hand. Moreover, juvenile birds of both sexes (i.e. those in their natal plumage) more closely resemble the bright plumage of adult males than the dull plumage of females. White-necked Jacobin seems completely unique in this respect: in all other dimorphic bird species, juvenile birds more closely resemble adult females.Sex-limited polymorphism is a special case of sexual dimorphism. Why does sexual dimorphism evolve? Darwin and Wallace debated the cause in birds: Darwin invoked female aesthetic preferences to explain why males were brightly coloured (i.e. sexual selection), while Wallace emphasized natural selection for camouflage on an exposed nest to explain why females were more cryptic [4].Dimorphism is most prevalent in species in which the sexes differ in how much they invest in producing offspring. For instance, Wallace's hypothesis applies to species where the female does all the work, not species where both sexes incubate. In birds, roughly 90% of species are socially monogamous, where both parents make substantial (although not necessarily equal) investment in offspring. Of the remaining 10% that are not monogamous, hummingbirds, a large clade of roughly 350 species, are fully one-third of the total. Remarkably, in not a single species are males known to help care for offspring. That is, there are no credible reports of males incubating, and no credible reports of a male provisioning either the offspring or their mother with food. But that said, for such a large clade, their mating systems are surprisingly poorly characterized (there seem to be more studies of mating systems of the 54 species of manakins (Pipridae) than of the 350 hummingbirds). While many hummingbird species apparently lek [5], in others males guard female nesting areas, or appear to engage in resource defence polygyny [6]. In at least a few species, females do not nest on male territories and males selectively allow certain females to feed from flowers on his territory [7], while guarding the territory from other hummingbirds, especially rival males.So how does female polymorphism fit in? It is not yet entirely clear. Polymorphism is fascinating because it requires special conditions, such as negative frequency-dependent selection (i.e. as one morph becomes rarer, it performs better) to maintain both morphs at the same time in the same population. Otherwise selection will tend to remove the less-fit morph. Most instances of polymorphism in birds are exhibited by both sexes [8]. Polymorphism may be limited to one sex when it ...

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Frequency distributions, dimorphisms, and allometric variation in size of the weapon on male harvestmen (Arthropoda, Arachnida, Opiliones)

Packard

2023

Evol Ecol

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Female plumage polymorphism is rare in hummingbirds

Cited by 5 publications

References 24 publications

The evolution of sexually dimorphic traits in ecological gradients: an interplay between natural and sexual selection in hummingbirds

The evolution of sexually dimorphic traits in ecological gradients: an interplay between natural and sexual selection in hummingbirds

Invited commentary on 'intersexual social dominance mimicry drives female hummingbird polymorphism'

Frequency distributions, dimorphisms, and allometric variation in size of the weapon on male harvestmen (Arthropoda, Arachnida, Opiliones)

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