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Abstract AimTropical regions harbour over half of the world's mammals and birds, but how their communities have assembled over evolutionary timescales remains unclear. To compare eco‐evolutionary assembly processes between tropical mammals and birds, we tested how hypotheses concerning niche conservatism, environmental stability, environmental heterogeneity and time‐for‐speciation relate to tropical vertebrate community phylogenetic and functional structure. LocationTropical rainforests worldwide. Time periodPresent. Major taxa studiedGround‐dwelling and ground‐visiting mammals and birds. MethodsWe used in situ observations of species identified from systematic camera trap sampling as realized communities from 15 protected tropical rainforests in four tropical regions worldwide. We quantified standardized phylogenetic and functional structure for each community and estimated the multi‐trait phylogenetic signal (PS) in ecological strategies for the four regional species pools of mammals and birds. Using linear regression models, we test three non‐mutually exclusive hypotheses by comparing the relative importance of colonization time, palaeo‐environmental changes in temperature and land cover since 3.3 Mya, contemporary seasonality in temperature and productivity and environmental heterogeneity for predicting community phylogenetic and functional structure. ResultsPhylogenetic and functional structure showed non‐significant yet varying tendencies towards clustering or dispersion in all communities. Mammals had stronger multi‐trait PS in ecological strategies than birds (mean PS: mammal = 0.62, bird = 0.43). Distinct dominant processes were identified for mammal and bird communities. For mammals, colonization time and elevation range significantly predicted phylogenetic clustering and functional dispersion tendencies respectively. For birds, elevation range and contemporary temperature seasonality significantly predicted phylogenetic and functional clustering tendencies, respectively, while habitat diversity significantly predicted functional dispersion tendencies. Main conclusionsOur results reveal different eco‐evolutionary assembly processes structuring contemporary tropical mammal and bird communities over evolutionary timescales that have shaped tropical diversity. Our study identified marked differences among taxonomic groups in the relative importance of historical colonization and sensitivity to environmental change.
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The mechanistic, genetic and evolutionary causes of bird eye colour variation
Birds display a rainbow of eye colours, but this trait has been little studied compared with plumage coloration. Avian eye colour variation occurs at all phylogenetic scales: it can be conserved throughout whole families or vary within one species, yet the evolutionary importance of this eye colour variation is under‐studied. Here, we summarize knowledge of the causes of eye colour variation at three primary levels: mechanistic, genetic and evolutionary. Mechanistically, we show that avian iris pigments include melanin and carotenoids, which also play major roles in plumage colour, as well as purines and pteridines, which are often found as pigments in non‐avian taxa. Genetically, we survey classical breeding studies and recent genomic work on domestic birds that have identified potential ‘eye colour genes’, including one associated with pteridine pigmentation in pigeons. Finally, from an evolutionary standpoint, we present and discuss several hypotheses explaining the adaptive significance of eye colour variation. Many of these hypotheses suggest that bird eye colour plays an important role in intraspecific signalling, particularly as an indicator of age or mate quality, although the importance of eye colour may differ between species and few evolutionary hypotheses have been directly tested. We suggest that future studies of avian eye colour should consider all three levels, including broad‐scale iris pigment analyses across bird species, genome sequencing studies to identify loci associated with eye colour variation, and behavioural experiments and comparative phylogenetic analyses to test adaptive hypotheses. By examining these proximate and ultimate causes of eye colour variation in birds, we hope that our review will encourage future research to understand the ecological and evolutionary significance of this striking avian trait.
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- PAR ID:
- 10548614
- Publisher / Repository:
- British Ornithologists Union
- Date Published:
- Journal Name:
- Ibis
- Volume:
- 166
- Issue:
- 2
- ISSN:
- 0019-1019
- Page Range / eLocation ID:
- 560 to 589
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1111/ibi.13276
