Derek Stefanik

Functional extinction of birds that feed on large seeds in the Brazilian Atlantic forest is associated with reduction in seed size of a palm species.  Seed size is an important trait for many aspects of a plant’s fitness, however, the size of a seed can constrain it’s dispersal capacity by reducing the number of bird taxa capable of seed dispersal because only large-bodied birds can ingest seeds above a certain size.  The probability of large seeds being dispersed is reduced when large seed feeding birds are extirpated, thereby likely lending selective pressure for reduced seed size and greater dispersal facility in the absence of birds capable of dispersing large seeds.  The authors find reduction of seed size likely occurred within the past 100 years, subsequent to human-driven deforestation and habitat fragmentation. This research suggests broad implications for the current reduction in large vertebrates on the evolutionary trajectories and community composition in many tropical forests.

Sequencing the genome of an Aboriginal Australian indicates that Aborigines diverged ~62,000-75,000 years ago from the gene pool shared by all living non-african humans, and represent a separate migration into Asia from the ancestors of modern Asians, which diverged from european ancestors ~25,000-38,000 years ago.   The authors note that their data is consistent with Aboriginal Australians being the direct descendants from the first humans in Australia, dating to ~50,000 years B.P., suggesting that Aboriginal Australians likely have one of the oldest continuous population histories outside sub-Saharan Africa today.