Micro-
and Macroevolution in Deep-sea Ostracodes
Monday,
4 June 2007
An
NMNH paleobiologist and evolutionary biologist,
with a close connection to the RTP students,
(an RTP intern in the class of 1995),
Dr. Gene Hunt presented an enlightening
lecture to begin Paleobiology Day. "Micro
& Macroevolution in Deep-Sea Ostracodes"
reconciled current hot issues in science
and served as an example of the scientific
success garnered by a former RTP intern.
Describing
the wealth of information retrieved from
the 3 billion years covered in the fossil
record, Dr. Hunt highlighted the history
of the scientific exploration of evolution,
beginning with Darwin, the Father of Evolution.
After tracing some of the history of the
study of evolution in the fossil record,
Hunt began discussing his own research
into the evolution of the tiny bi-valved
crustaceans known as ostracodes.
Studying
the ostracode genus Poseidonamicus
through the fossil record, Dr. Hunt encountered
a trend of increasing body size over time
within species. Researching to understand
that trend, Dr. Hunt explored the relationship
of Cope's Rule of "increasing size
over time" and Bergmann's Rule of
"increasing size with decreasing
temperature," two kinds of body size
relationships within species. Dr. Hunt
explained how a Cope's Rule macroevolutionary
pattern of increasing body size in Poseidonamicus
could result from Bergmann's Rule occurring
within individual lineages, combined with
an overall cooling of the oceans over
the past 50 million years. Dr. Hunt demonstrated
that the macroevolutionary change in the
deep-sea ostracode population in the Cenozoic
era was an accumulation of changes within
lineages.
Turning
to a discussion of ostracode morphology
and development, the NMNH Curator of Ostracoda
spoke of natural selection… in Fossils!
The students were fascinated with Dr.
Hunt's images of cell divisions inferred
from fossils, including apparent "mistakes"
in the normal sequence of cell divisions
that occurred as the animals grew. Dr.
Hunt cited a particular cell-division
variant he showed to have "lower
fitness" as an example of a trait
that, despite having ample variation,
did not evolve over time. He concluded
that in this example of microevolution,
individuals with the variant morphology
did not evolve because of their lower
fitness.
Dr. Hunt's research suggests that micro
& macroevolution are not divorced,
as indicated in the Cenozoic fossil record
which provides deep insight into the tiny
Ostracodes found in the deep sea.
-
Morgan Little
