Wings, Horns, and Butterfly Eyespots: How Do Complex Traits Evolve?
Antónia Monteiro*, Ondrej Podlaha
Citation: Monteiro A, Podlaha O (2009) Wings, Horns, and Butterfly Eyespots: How Do Complex Traits Evolve? PLoS Biol 7(2): e1000037. doi:10.1371/journal.pbio.1000037
Published: February 24, 2009
Copyright: © 2009 Monteiro and Podlaha. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: We thank the National Science Foundation (NSF IOB–0653399) for financial support. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Abbreviations: CRE, cis-regulatory element
* To whom correspondence should be addressed. E-mail: antonia.monteiro@yale.edu
Antónia Monteiro and Ondrej Podlaha are with the Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America.
“If we take modularity at all seriously, then any attempt to use developmental mechanisms as phylogenetic tools is doomed: how could one hope to distinguish between bona fide conservation (a stable history between mechanism character) and re-use or (worse yet) re-invention?”—von Dassow and Munro, 1999 [1]
Throughout their evolutionary history, organisms have evolved numerous complex morphological, physiological, and behavioral adaptations to increase their chances of survival and reproduction. Insects have evolved wings and flight, which allowed them to better disperse [2], beetles have grown horns to fight over females [3], and moths and butterflies have decorated their wings with bright circles of colored scales to scare off predators [4]. The way that most of these and other adaptations first evolved, however, is still largely unknown. In the last two decades we have learned that novel traits appear to be built using old genes wired in novel ways [5], but it is still a mystery whether these novel traits evolve when genes are rewired de novo, one at a time, into new developmental networks, or whether clusters of pre-wired genes are co-opted into the development of the new trait. The speed of evolution of novel complex traits is likely to depend greatly on which of these two mechanisms underlies their origin. It is important, thus, to understand how novel complex traits evolve.
So far, our understanding of how adaptations and novel morphological traits are acquired is mostly founded on single gene case studies. On the one hand, researchers have focused on changes to morphology that involve regulatory or structural mutations in enzyme-coding loci predominantly at the termini of regulatory circuits (see reviews in [6,7]), and, on the other hand, researchers have dissected the genetic and/or developmental changes that underlie the modification or disappearance of pre-existent complex traits (Table 1). Few studies, however, have tried to directly address the genetic and developmental origins of new complex traits.
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