Marshall Lab

Research

Projects recently completed (see publications for complete list) or ongoing include:

Evolutionary Dynamics

The fossil record, molecular phylogenies, and inferring biodiversity dynamics: Use of computer simulation and the fossil record to explore the ways the fossil record and molecular phylogenies complement each other when trying to understand the patterns and processes of diversification of living taxa (with Tiago Quental and Lee Hsiang Liow [Norway]).

Calibrating molecular clocks: Continued development of a new method for using the fossil record to calibrate molecular phylogenies (Marshall, Am. Nat., 2008); quantification of the geological and paleontological realities and Bayesian priors on divergence times.

Biodiveristy dynamics of shallow water marine Californian faunas during the Neogene contraction of the tropics (Lucy Chang).

Diversity Through Time

Explaining the endemism of South American canids: Using a fossil calibrated molecular phylogeny to examine the extent to which South American canid endemism is due to in situ speciation (with Deven Vyas and Tiago Quental), or extra-South American extinction.

Fossil analysis of the angiosperm radiation: Using a the comprehensive fossil pollen database compiled by Nathalie Nagalingum to provide the first comprehensive continent-scale analysis of the angiosperm radiation for Australia (with Nathalie Nagalingum).

Living cycads: Discovery using molecular phylogenetics that the living species of cycads, rather than being ancient relicts, all originated in a global burst of speciation from ~10– 5 million years ago (led by Nathalie Nagalingum and Sarah Matthews at Harvard).

Major Events in the History of Life

Cambrian explosion: Exploring the extent to which pre-adaptation underpinned the Cambrian explosion (with Jim Valentine).

Quantifying temporal trends in trilobite defensive morphologies: Use of morphometric techniques to quantify the secular trends in trilobite defenses (with Colin Teo [Harvard undergraduate honors thesis] and Andy Knoll [Harvard]).

Trilobite extinction at the end-Devonian: Analysis of the dynamics of Devonian trilobites as a window into the cause(s) of the end-Devonian mass depletion (Freddy Santistevan).

Collaborations with other labs

(Largely centered on using the fossil record to
understand the biotic impacts of global change):

South American megafaunal extinctions: Using the extensive fossil record of end-Pleistocene fossil mammals to asses the relative contributions of climate change and human impacts on the South American megafaunal extinctions (led by the Barnosky lab – my role is quantitative analysis of the stratigraphic data).

Climate analysis of central California using data from a ~130,000 year core (led by the Looy lab, along with several others co-PIs on campus).