IN THE ATLANTIC FOREST: EXTINCTION OF BIRDS DRIVES EVOLUTIONARY CHANGES IN SEED SIZE

""Tucano-de-bico-preto" (Channel-billed Toucan, Ramphastos vitellinus)

"Jacutinga" (Black-fronted Piping Guan, Pipile jacutinga)

• Science 31 May 2013: 
  Vol. 340 no. 6136 pp. 1086-1090 
  DOI: 10.1126/science.1233774
• Functional Extinction of Birds Drives Rapid Evolutionary Changes in Seed Size
• Abstract (complete reference above):
• Local extinctions have cascading effects on ecosystem functions, yet little is known about the potential for the rapid evolutionary change of species in human-modified scenarios. We show that the functional extinction of large-gape seed dispersers in the Brazilian Atlantic forest is associated with the consistent reduction of the seed size of a keystone palm species. Among 22 palm populations, areas deprived of large avian frugivores for several decades present smaller seeds than nondefaunated forests, with negative consequences for palm regeneration. Coalescence and phenotypic selection models indicate that seed size reduction most likely occurred within the past 100 years, associated with human-driven fragmentation. The fast-paced defaunation of large vertebrates is most likely causing unprecedented changes in the evolutionary trajectories and community composition of tropical forests.
• 
  

Over five years, the researchers collected more than 9 thousand seeds of 22 populations of palm trees, scattered in small fragments and continuous forest areas of the Atlantic Forest between the states of Paraná and the south of Bahia.
Both birds shown in the photos above, eat large seeds and are responsible for dissemination of tropical palm trees of the Atlantic Forest, like "jussara" (photo below) commonly used for palm heart.

"Jussara", Euterpes