Tag: A1 Evolutionary Trajectories

A 10,500 Year Paleoecological Record of the Interior Rainforest of Eastern British Columbia

Presenter: Ariana White

Mentor: Daniel Gavin

PM Session Oral Presentation

Panel Name: A1 Evolutionary Trajectories

Location: Alsea Room

Time: 11:00am – 12:00pm

Although there have been multiple investigations into the coast range and island ecosystems of British Columbia, the climate and forest history of the interior is less well studied. The interior of British Columbia houses one of the largest temperate rain forests in North America due to its location along the wet westernmost portion of the Rocky Mountains. In our investigation, we posit that this biome has shifted in location in accordance with changes to the climate system through the centuries. Morkill Lake, British Columbia, is located at the northern terminus of the inland wet belt zone in the Fraser River valley. The ecotone in which the lake is located represents the very edge of this unusual biome at the place where the rainforest gives way to drier and colder boreal forest. We present a pollen record from Morkill Lake which extends back 10,500 years BCE and illustrates the biological dynamism and basic climatological characteristics of this area through millennia of transition.

The Evolution of Rhino Arthritis in the Cenozoic

Presenter: Kelsey Stilson

Mentor: Samantha Hopkins

PM Session Oral Presentation

Panel Name: A1 Evolutionary Trajectories

Location: Alsea Room

Time: 11:00am – 12:00pm

Arthritis is one of the most common skeletal pathologies, occurring in one-sixth of humans. Rhinocerotids provide a natural system for understanding the evolutionary underpinnings of arthritis. The severity and prevalence of arthritis in Rhinocerotidae increased substantially from 50 million years ago to the present. All five living species of rhinoceros develop arthritis before they reach maturity. Fossil rhinoceros relatives from 50 million years ago (Ma) show a dramatically different pattern of arthritic development. What changed from 50 Ma to today? Rhinos became graviportal, evolving from Hyrachyus, which was about the size and shape of a large dog, to the one-ton, stout-limbed animals of today. Despite this order of magnitude increase in size, rhinos also consistently display cursoriality (the habit of running) through time. These competing factors of increasing size and cursoriality provide a possible driver for the prevalence of arthritis. This study traces the history of arthritic development in the rhino lineage, finding that the distribution of arthritis is related to increasing body size, but that there are also clearly evolutionary effects determining its prevalence. This study is especially important because it examines an apparent pathology that persisted and even worsened despite millions of years of evolution that should have selected against it.

Topographic and Climate Change Differentially Drive Pliocene and Pleistocene Mammalian Beta Diversity of the Great Basin and Great Plains Provinces of North America

Presenter: Amy Atwater

Mentor: Edward Davis

PM Session Oral Presentation

Panel Name: A1 Evolutionary Trajectories

Location: Alsea Room

Time: 1:15pm – 2:15pm

The Great Basin region of the western United States currently has elevated beta (between-site) diversity compared to that of the past 10 million years. We test two competing hypotheses to explain this pattern: 1) Pleistocene climatic cycling, with diversity drop- ping during warm intervals and increasing during cooler ‘Ice Age’ intervals; or 2) topographic change, where tectonic expansion created a diversity of habitats, packing drastically different environments close together. To test these hypotheses, we analyzed the beta diversity of non-flying land mammals from the Late Miocene (~8 million years ago) to Recent of the Great Basin of the United States, with the central Great Plains of the United States as a control. Using mammalian faunal lists from the FAUNMAP II database, we esti- mated richness- and evenness –based beta diversity for 4 time-slices based on mammalian biochronology. Our results show that beta diversity, in terms of both richness and evenness, is higher in the Great Basin than in the Great Plains at all intervals from the Late Miocene to the Recent except for the Holocene. The Holocene of the Great Plains revealed surprisingly high evenness beta diversity and is the subject of continued investigation. The overall results support our hypothesis that Great Basin beta diversity has primarily been driven by tectonic change, but the Great Plains Holocene results suggest that other factors, particularly climate change, have affected beta diversity.