Sept 29 2011: Physical Processes and Evolutionary Consequences

David Jacobs
Dept. Ecology & Evolutionary Biology, UCLA

Three vignettes of different scales of flow and landscape influence on
biotic process will be presented.

1) The Late Precambrian Rangeomorph fauna of Mistaken Point Newfoundland
constitute the earliest community of large multicellular organisms.
Through flow modeling we demonstrate that these organisms evolved large
size to access higher velocities in a low flow environment. Access to
velocity overcomes diffusional limits to resource acquisition in a
community dependant on dissolved resources, providing the impetus to
the evolution of large multicellular form.

2) Rapid landscape evolution of the Society Islands resulted from recent
sea-level fall from a mid-Holocene maximum. This fall first generated a
plethora of reef-top atolls in Polynesia. In the last two millennia
such islands have been eliminated preferentially from the south-sides
of the Society Islands as a consequence of wave energy from the
Southern Ocean, yielding dramatic change of reef and lagoon
environments with attendant consequences for marine life and the human

3) Coastal estuaries of California have undergone a maturation process
during the Holocene converting many estuaries from bays to lagoonal
systems dominated by the episodic/seasonal stream flow of our
Mediterranean climate. The impacts of the inter-annual details of
stream flow on dispersal of a seasonal-lagoon specialist fish, the
tidewater goby, are examined using high-resolution genotyping.
Conservation genetic and estuarine restoration issues are touched upon.