Friday, April 13, 2018

[Ornithology / Ecology • 2018] Synergistic Selection Regimens drive the Evolution of Display Complexity in Birds of Paradise

in Miles & Fuxjager, 2018.   
 DOI: 10.1111/1365-2656.12824

1 .Integrated visual displays that combine gesture with colour are nearly ubiquitous in the animal world, where they are shaped by sexual selection for their role in courtship and competition. However, few studies assess how multiple selection regimens operate on different components of these complex phenotypes on a macroevolutionary scale.
2. Here, we study this issue by assessing how both sexual and ecological selection work together to influence visual display complexity in the birds of paradise.
3. We first find that sexual dichromatism is highest in lekking species, which undergo more intense sexual selection by female choice, than non‐lekking species. At the same time, species in which males directly compete with one another at communal display courts have more carotenoid‐based ornaments and fewer melanin ornaments.
4. Meanwhile, display habitat influences gestural complexity. Species that dance in the cluttered understorey have more complex dances than canopy‐displaying species.
5. Taken together, our results illustrate how distinct selection regimens each operate on individual elements comprising a complex display. This supports a modular model of display evolution, wherein the ultimate integrated display is the product of synergy between multiple factors that select for different types of phenotypic complexity.

KEYWORDSanimal communication, behavioural ecology, display habitat, evolutionary ecology, lek, sexual selection, signal design

Figure 1: Phylogeny of the birds of paradise from Jønsson et al. (2016), with gestural display complexity (outer ring) and dichromatism (inner ring) scores illustrated on a colour ramp. Blanks indicate species for which there was insufficient information to characterize display complexity. Illustrations depict males performing their complex integrated visual displays, with species selected that best represent the breadth of colour and display complexity found in the family

Altogether, these results offer novel insight into the macroevolutionary pattern of visual display design: different signal components can be simultaneously and independently influenced by multiple core evolutionary processes, which interact to produce the ultimate integrated visual display. This highlights the remarkable potential of diverse selection regimens, often viewed as discrete operators, to instead function independently on a single signal component, while still interacting with other processes to shape overall complexity. The result is an integrated display that conveys more information than the sum of its constituent signals—and, in the case of extraordinary bird of paradise visual displays, exemplifies the diversifying potential of animal behaviour.

Meredith C. Miles and Matthew J. Fuxjager. 2018. Synergistic Selection Regimens drive the Evolution of Display Complexity in Birds of Paradise. Journal Animal Ecology.  DOI: 10.1111/1365-2656.12824