Turtles have been around for hundreds of millions of years, but it turns out most North American turtles we see today are new to the block.
Museum scientist Pat Holroyd and retired paleontologist Howard Hutchison have been exploring UCMP's vast collection of fossil turtles from Wyoming in hopes of tackling the little addressed question of how turtles and other aquatic reptiles respond to changing climates. These fossils have managed to tell the story of several ancient takeovers back in the Eocene, about 55 million years ago. The Eocene was when several abrupt global warming events took place - the first of which defines the start of the epoch, the Paleocene-Eocene Thermal Maximum (PETM) - and semi-tropical forests extended across the northern United States.
It turns out that with warming temperatures came a case of turtle wanderlust. While most groups of North American animals are thought to disperse via high latitude dispersal routes (like along the Bering Land Bridge or through Greenland) to the continent they call home, some reptiles, especially turtles and lizards, also opted to disperse from the south as new corridors opened up during the PETM. The eclectic mix of creatures in North America resulting from these long treks included pond turtles and tortoises from Asia and mud turtles and river turtles from Central America.
These foreign arrivals rapidly dominated their new environments, reminiscent of classic invasive species dynamics. And this doesn't only happen in the PETM. Another warming event later on in the Eocene has the same signature turnover, but with a new set of immigrants, including the ancient relatives of today's tortoises. But while the composition of North American turtles during these times shifted dramatically in favor of the migrants, there is no sign that there were any extinctions of the locals. They merely got shunted into relatively smaller abundances.
So it is critical to understand dispersal and dispersal routes in order to understand how the composition of a fauna changes in response to climate, stresses Pat. It'll be interesting to see how the turtles respond to the modern age of global warming.
Congratulation to UCMP's Jenna Judge who was awarded a spot in the NSF East Asia and Pacific Summer Institutes (EAPSI) last spring. NSF EAPSI provides funding for a graduate student to spend a summer in an East Asian or Pacific country to conduct scientific research as well as engage in societal and cultural practices. Jenna spent her summer in Japan, studying the evolutionary history and ecology of a group of limpets that live in a variety of habitats in the deep sea! Check out her adventures on her personal blog - the eclectic limpet.
Figure 1: Bolzano covers the floor of intersecting alpine valleys defined by stunning dolomite peaks (upper left). Check out the local GAP for the latest in dirndl fashion (lower left). Cin and Ivo inspect a big slab with Late Permian conifer branches (right).
This summer we headed to the Italian Alps to work on fossils from a newly discovered Late Permian plant locality in the incredibly scenic Bletterbach gorge. This research is part of a larger project, which tries to quantify the hits that the terrestrial ecosystem took during the end-Permian world-wide biotic crisis. Back in those days Europe and North America were connected and part of one and the same floral realm, not surprisingly called Euramerica. Euramerica was tropical and semi-arid, and its floras were characterized by conifers and seedferns. Floral remains from this area and time interval are few and far between and notoriously incomprehensive, and thus also is our understanding of the floras. The discovery in the north Italian Dolomites of a specimen (as well as taxon-rich macrofossil flora some years ago) therefore means a big leap forward. Last year a multidisciplinary team was assembled to make an inventory and study the various plant groups and reptilian ichnofossils collected at the site. We were there to study and photograph the conifer remains and sample them for preserved leaf cuticles.
Truckloads of fossiliferous material had already been collected by volunteers over the last few years and were ready to be worked on. As a result, the field part of our expedition was reduced to sampling cuticle bearing sediment layers - sitting right on top of the Butterloch waterfall in Geoparc Bletterbach. The remaining time was spent digging the museum collection.
The collection is housed in the natural history gem Naturmuseum Südtirol in Bolzano - or Bozen as the German speaking South Tyroleans call it. The museum in turn is housed in a beautiful respectfully converted historic building from the latest 1400s in the “Bozner Altstadt”. So - just like last year - we spent the hottest part of the European summer up on the attic of yet another natural history museum.
Our counterpart, curator Dr. Evelyn Kustatcher, turned out to be a fabulous cook as well as a wonderful host. That, together with daily macchiatos and apiretivos on café terraces, and the stunning natural beauty of the area made Bolzano a particularly difficult place to leave.
We will be back...
Figure 2: Sampling the cuticle-rich layer close to the waterfall (upper left). Our host Evelyn Kustatcher (red shirt) explains geo-tourist spectators what we are doing (lower left). A look into the Butterloch-Bletterbach Gorge from above (right).