Reconstrucción las características de historia de vida en los ancestros de los tordos: un análisis de las adaptaciones al parasitismo de cría.

PUJOL, E. MANUELA; MERMOZ, M. E.

Buenos Aires

Congreso; XI Reunión Argentina deOrnitología; 2005

Asociación Ornitológica del Plata

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Avian brood parasitism evolved independently seven times. Therefore, it might be possible that some characteristics present in the ancestors could have facilitated its evolution. Hamilton and Orians (1965) stated that non-parasitic ancestor of cowbirds accelerated its incubation period and nestling growth, while later it was suggested that it developed small-sized eggs. However, these hypotheses could not be tested without a proposal of the genealogical relationship of cowbirds and their sister species. Based on recent molecular phylogenies, parasitic cowbirds evolved within the “Grackles and allies”. Accordingly, we tested if small-sized eggs with short incubation periods and nestlings with accelerated growth evolved in the immediate ancestor of “Grackles and allies”. We built a working phylogeny by condensing all information on published phylogenies. Then, we used two comparative methods to recreate the hypothetical ancestor of all “Grackles and allies”: reconstruction of the ancestral state and generation of the prediction intervals. We applied two evolutionary models incorporating the external phylogeny in three steps within both methodologies. Thus, we obtained six approximations within each methodology. Both methodologies showed that the ancestor of “Grackles and allies” never shortened its incubation period. Similarly, during 4/6 ancestor reconstruction, neither egg or female weight changed. Contrary to expectations, in remaining two reconstructions the ancestor of “Grackles and allies” increased both egg and female weights. However, prediction intervals indicated that those increments did not imply an allometric change in size. Consequently, neither a small egg weight nor a short incubation period evolved in the immediate ancestor of “Grackles and allies”.