Possible interest for some:
Ligon, R. A., C. D. Diaz, J. L. Morano, J. Troscianko, M. Stevens, A. Moskeland, T. G. Laman and E. Scholes III (2018). “Evolution of correlated
complexity in the radically different courtship signals of birds-of-paradise.”
PLoS Biology 16(11): e2006962.
Open access:
https://journals.plos.org/plosbiology/article/file?id=10.1371/journal.pbio.2006962&type=printable (accessed 13 March 2019)
Abstract: Ornaments used in courtship often vary wildly
among species, reflecting the evolutionary interplay between mate preference functions and the constraints imposed by natural selection. Consequently, understanding the evolutionary dynamics responsible for ornament diversification has been a longstanding
challenge in evolutionary biology. However, comparing radically different ornaments across species, as well as different classes of ornaments within species, is a profound challenge to understanding diversification of sexual signals. Using novel methods and
a unique natural history dataset, we explore evolutionary patterns of ornament evolution in a group—the birds-of-paradise—exhibiting dramatic phenotypic diversification widely assumed to be driven by sexual selection. Rather than the tradeoff between ornament
types originally envisioned by Darwin and Wallace, we found positive correlations among cross-modal (visual/acoustic) signals indicating functional integration of ornamental traits into a composite unit—the “courtship phenotype.” Furthermore, given the broad
theoretical and empirical support for the idea that systemic robustness—functional overlap and interdependency—promotes evolutionary innovation, we posit that birds-of-paradise have radiated extensively through ornamental phenotype space as a consequence of
the robustness in the courtship phenotype that we document at a phylogenetic scale. We suggest that the degree of robustness in courtship phenotypes among taxa can provide new insights into the relative influence of sexual and natural selection on phenotypic
radiations.
Author summary
Animals frequently vary widely in ornamentation, even among closely related species. Understanding the patterns that underlie this variation
is a significant challenge, requiring comparisons among drastically different traits—like comparing apples to oranges. Here, we use novel analytical approaches to quantify variation in ornamental diversity and richness across the wildly divergent birds-of-paradise,
a textbook example of how sexual selection can profoundly shape organismal phenotypes. We find that color and acoustic complexity, along with behavior and acoustic complexity, are positively correlated across evolutionary timescales. Positive links among ornament
classes suggests that selection is acting on correlated suites of traits—a composite courtship phenotype—and this integration may be partially responsible for the extreme variation in signal form that we see in birds-of-paradise.
Prost, S., E. E. Armstrong, J. Nylander, G. W. C. Thomas, A. Suh, B. Petersen, L. Dalen, B. W. Benz, M. P. K. Blom, et al. (2019). “Comparative
analyses identify genomic features potentially involved in the evolution of birds-of-paradise.”
GigaScience, giz003, https://doi.org/10.1093/gigascience/giz003. Download at:
https://academic.oup.com/gigascience/advance-article/doi/10.1093/gigascience/giz003/5300102
Abstract: The diverse array of phenotypes and courtship
displays exhibited by birds-of-paradise have long fascinated scientists and laymen alike. Remarkably, almost nothing is known about the genomics of this iconic radiation. There are 41 species in 16 genera currently recognized within the birds-of-paradise family
(Paradisaeidae), most of which are endemic to the island of New Guinea. In this study, we sequenced genomes of representatives from all five major clades within this family to characterize genomic changes that may have played a role in the evolution of the
group's extensive phenotypic diversity. We found genes important for coloration, morphology, feather and eye development to be under positive selection. In birds-of-paradise with complex lekking systems and strong sexual dimorphism, the core birds-of-paradise,
we found GO categories for “startle response” and “olfactory receptor activity” to be enriched among the gene families expanding significantly faster compared to the other birds in our study. Furthermore, we found novel families of retrovirus-like retrotransposons
active in all three de novo genomes since the early diversification of the birds-of-paradise group, which might have played a role in the evolution of this fascinating group of birds.
Robin Hide
