TY - JOUR
T1 - Closely related bird species demonstrate flexibility between beak morphology and underlying developmental programs
AU - Mallarino, Ricardo
AU - Campàs, Otger
AU - Fritz, Joerg A.
AU - Burns, Kevin J.
AU - Weeks, Olivia G.
AU - Brenner, Michael P.
AU - Abzhanov, Arhat
PY - 2012/10/2
Y1 - 2012/10/2
N2 - The astonishing variation in the shape and size of bird beaks reflects awide range of dietary specializations that played an important role in avian diversification. Among Darwin's finches, ground finches (Geospiza spp.) have beaks that represent scaling variations of the same shape, which are generated by alterations in the signaling pathways that regulate growth of the two skeletal components of the beak: the prenasal cartilage (pnc) and the premaxillary bone (pmx). Whether this developmental mechanism is responsible for variation within groups of other closely related bird species, however, has remained unknown. Here, we report that the Caribbean bullfinches (Loxigilla spp.), which are closely related to Darwin's finches, have independently evolved beaks of a novel shape, different from Geospiza, but also varying from each other only in scaling. However, despite sharing the same beak shape, the signaling pathways and tissues patterning Loxigilla beaks differ among the three species. In Loxigilla noctis, as in Geospiza, the pnc develops first, shaped by Bmp4 and CaM signaling, followed by the development of the pmx, regulated by TGFβIIr, β-catenin, and Dkk3 signaling. In contrast, beak morphogenesis in Loxigilla violacea and Loxigilla portoricensis is generated almost exclusively by the pmx through a mechanism in which Ihh and Bmp4 synergize to promote expansion of bone tissue. Together, our results demonstrate high flexibility in the relationship between morphology and underlying developmental causes, where different developmental programs can generate identical shapes, and similar developmental programs can pattern different shapes.
AB - The astonishing variation in the shape and size of bird beaks reflects awide range of dietary specializations that played an important role in avian diversification. Among Darwin's finches, ground finches (Geospiza spp.) have beaks that represent scaling variations of the same shape, which are generated by alterations in the signaling pathways that regulate growth of the two skeletal components of the beak: the prenasal cartilage (pnc) and the premaxillary bone (pmx). Whether this developmental mechanism is responsible for variation within groups of other closely related bird species, however, has remained unknown. Here, we report that the Caribbean bullfinches (Loxigilla spp.), which are closely related to Darwin's finches, have independently evolved beaks of a novel shape, different from Geospiza, but also varying from each other only in scaling. However, despite sharing the same beak shape, the signaling pathways and tissues patterning Loxigilla beaks differ among the three species. In Loxigilla noctis, as in Geospiza, the pnc develops first, shaped by Bmp4 and CaM signaling, followed by the development of the pmx, regulated by TGFβIIr, β-catenin, and Dkk3 signaling. In contrast, beak morphogenesis in Loxigilla violacea and Loxigilla portoricensis is generated almost exclusively by the pmx through a mechanism in which Ihh and Bmp4 synergize to promote expansion of bone tissue. Together, our results demonstrate high flexibility in the relationship between morphology and underlying developmental causes, where different developmental programs can generate identical shapes, and similar developmental programs can pattern different shapes.
KW - Convergent evolution
KW - Craniofacial
KW - Morphogenesis
UR - http://www.scopus.com/inward/record.url?scp=84867047869&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84867047869&partnerID=8YFLogxK
U2 - 10.1073/pnas.1206205109
DO - 10.1073/pnas.1206205109
M3 - Article
C2 - 22988109
AN - SCOPUS:84867047869
SN - 0027-8424
VL - 109
SP - 16222
EP - 16227
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 40
ER -