• Geology 1003 - Historical Geology
• Geology 3011 - Introduction to Paleontology
• Geology 7120 - Paleobiology
• Geology 7115 - Paleobiology

Current Research

In the geologic record, biotic remains preserve a record of ancient life and provide a wealth of information as sediment grains, and I integrate both types of information into my research.  The primary focus of my research is molluscan paleobiology, paleoecology, taphonomy, and phylogeny.  Current projects include a field and laboratory study of the evolutionary history of Neogene Corbulidae (Bivalvia: Myoidea) in tropical America, especially as it relates to environmental, oceanographic, and climatic changes over the last 23 million years (Neogene). I am expanding this research in collaboration with Mike Hellberg of Biological Sciences and postdoctoral associate Audrey Aronowsky to produce a systematic revision of the Corbulidae at a global scale to examine the ecology and life history characteristics of invasive marine clades. I am developing a collaboration with department colleagues Audrey Aronowsky, Annette Engel, and Huiming Bao to examine the phylogenetic, biogeographic, and geologic history of endosymbiosis between lucinid bivalves and the sulfur-oxidizing bacteria they host. I also am interested in finding reliable multitaxon and taphonomic proxies for seagrass beds in the fossil record. I have collaborated with several colleagues in Geology, Biology and Coastal Studies to evaluate oil and gas platforms on the Louisiana Continental Shelf for organisms with biotechnology potential. In other research projects, I have used taphonomic and paleoenvironmental data from macrofaunal and foraminiferal assemblages to reconstruct the climatic, environmental, and depositional history of Holocene sediments on the northeastern Gulf of Mexico shelf and the southwestern Louisiana chenier plain.

Evolution of Marine Invertebrates in the tropical American Neogene

In one current project, I am delineating the evolutionary history of Neogene Corbulidae (Bivalvia) in tropical America, especially as it relates to closure of the Isthmus of Panama and to climate change associated with the onset of continental glaciation in the Northern Hemisphere. Cladistic analyses of corbulid genera produce a very limited number of robust and well-resolved phylogenies that agree well with the fossil record. Tropical American corbulids are not monophyletic, although two crown groups are endemic. These clades and two other genera first appear in the Miocene of tropical America, which is also the time of greatest morphospace occupation in Caryocorbula, the most abundant and diverse corbulid genus in the region. Subsequent Plio-Pleistocene extinctions preferentially eliminate large-bodied corbulid genera and Caryocorbula species in the tropical western Atlantic. These extinction-driven size trends probably are caused by decreased nutrient availability in the tropical western Atlantic as the Panama Isthmus emerged.

In related work, I am currently documenting variation in shell accretion in corbulids to test the hypotheses that shell shape is highly constrained in Caryocorbula. Interspecific allometry is very strong in Caryocorbula and appears to be controlled by some developmental or pleiotropic constraint, perhaps related to the inequivalved shell characteristic of the family or to a complex ontogeny of shell accretion. In collaboration with Dave Goodwin (LSU postdoc), I am currently testing these inferences using geochemical and schlerochronologic techniques.

Evolutionary History of the freshwater corbulid Pachydon

With Joseph Hartman (University of North Dakota) I am examining the evolutionary relationships of among species of Pachydon, a fresh to brackish water corbulid genus. Miocene Pachydon are thought to represent an endemic radiation of marine bivalves into a large freshwater system with intermittent marine connections that was located within the western Amazon Basin. A species with strong affinities to other members of Pachydon, P. mactriformis, occurs, however, in the Paleocene of the Dakotas and Saskatchewan in a similar paleoenviromental setting. Phylogenetic analysis is under way to determine whether Paleocene Pachydon are closely related to or are convergent with Miocene Pachydon. If closely related, a long missing history exists for this taxon within the Americas. If convergent, similarities between Paleocene and Miocene taxa indicate that valve shape is strongly constrained by either natural selection or architectural constraints when corbulids invade freshwater systems.

Evolution of Symbiosis Between Bacterial Endosymbionts and Their Lucinid Bivalve Hosts

Symbiosis is a fundamental driver of biological systems. In the Bivalvia, bacterial endosymbioses are common and both ecologically and evolutionarily varied, thus providing means to expand existing evolutionary models for this important class of biotic interactions. The association between thiotrophic (sulfur-oxidizing) bacteria and lucinid bivalves is intriguing because its inferred antiquity (>400 m.y.) seems at odds with the relatively loose ecologic linkage of living members. In addition, hypotheses concerning the evolutionary origin of universal endosymbiosis in the monophyletic Lucinidae + Fimbriidae clade (basal synapomorphy vs. differential extinction vs. multiple evolutionary origins) have not been tested, and cannot be tested without incorporation of fossil data. Annette Engel, Huiming Bao, Audrey Aronowsky, and I are developing a research program to test for (a) cospeciation between lucinids and their endosymbionts, (b) congruence between morphologically and molecularly defined lucinid species, and (c) a distinct d34S value for carbonate-associated sulfate (CAS) in lucinid shells.

Corbulid Bivalves: Examining Invasive Species in a Phylogenetic Framework

As human economies are increasingly globalized, invasive species are a growing threat to terrestrial, freshwater, and marine ecosystems. These invasives incur losses of over $130 billion/year in the U.S. alone, and permanently alter the ecosystems in which they become established. Mitigating the effects of existing invasives and preventing further invasions requires accurate knowledge of species’ ecology, life-history, and biogeography. This knowledge, in turn, is based on rigorously established taxonomies and phylogenies for clades that include invasive species. Mike Hellberg, Audrey Aronowsky and I are reconstructing phylogenetic relationships within the Corbulidae, a diverse (ca. 600 extant and extinct species) clade of predominantly marine bivalves. Incomplete taxonomic and phylogenetic characterization of corbulids creates an ecologic and economic information gap because some species are invasive and many act as ecosystem engineers. Like zebra mussels and many other invaders, corbulids flourish in marginal settings, including anthropogenically altered coastal areas, and can be readily transported through shipping as larvae and adults. These bivalves also have a fossil record of colonization and domination of freshwater systems. These ancient natural radiations parallel modern anthropogenically-mediated invasions, and provide a unique opportunity to identify biologic underpinnings of colonization and invasion. The proposed research will synthesize molecular, shell morphologic, and soft anatomic data in order to integrate extant and fossil diversity of the Corbulidae. The distribution of extant and fossil invasive corbulids within the clade will be established, and the correspondence between invasives and the possession of ecologic and life-history character states promoting invasive success will be tested. The same phylogeny and traits can be applied to hypotheses testing the role of ecologic and life-history character states in promoting speciation when strong dispersal barriers are absent. In addition, a well-established phylogeny will be used to test the relative roles of phylogenetic inertia and selection in causing the noted interspecific allometry in the most diverse corbulid subclade, Caryocorbula.

• Ph.D., 1991, University of Wisconsin - Madison
• M.S., 1987, Bowling Green State University (Ohio)
• B.S., 1985, University of Minnesota - Morris

Anderson, L.C., Hartman, J.H., and Wesselingh, F. 2006. Close evolutionary affinities between freshwater corbulid bivalves from the Neogene of Western Amazonia and Paleogene of the Northern Great Plains, USA. Journal of South American Earth Sciences. In press, invited.

Anderson, L. C. and Roopnarine, P. D.2005. Interplay of adaptation and constraint in morphospace utilization of Caryocorbula (Mollusca: Corbulidae) of the Caribbean Neogene. Paleontologica Electronica.

Anderson, L.C. and P.D. Roopnarine. 2003. Evolution and phylogenetic relationships of Neogene Corbulidae (Bivalvia; Myoidea) of tropical America. Journal of Paleontology, 77: 1086-1102. (Received best paper award for journal for 2003.)

Taylor, M.J., R.A. McBride, L.C. Anderson, and M.R. Byrnes. 2002. Building on the research of our founders: 65 years of chenier plain studies at Louisiana State University. In M.K. Steinberg and P.F. Hudson, eds. Cultural and Physical Expositions: Geographic Studies in the Southern United States and Latin America. Geoscience Publications, Department of Geography and Anthropology, Louisiana State University, Baton Rouge, p. 261-276.

Henderson, W.G., L.C. Anderson, and C.R. McGimsey. 2002. Distinguishing Natural and Archaeological Deposits: Stratigraphy, Taxonomy, and Taphonomy of Holocene Shell-Rich Accumulations from the Louisiana Chenier Plain. Palaios, v. 17, p. 192-205.

Anderson, L.C. 2001. Temporal and geographic size trends in Neogene Corbulidae (Bivalvia) of tropical America: Using environmental sensitivity to decipher causes of morphologic trends. Palaeogeography, Palaeoclimatology, Palaeoecology, v. 166, p. 101-120.

Anderson, L.C. 2001. Transport and spatial fidelity. In D.E.G. Briggs and P.R. Crowther, eds.  Palaeobiology II, Blackwell Scientific, London, p. 289-292.

McBride, R.A., L.C. Anderson, A. Tudoran, and H.H. Roberts. 2000. Holocene stratigraphic architecture of a sand-rich shelf and the origin of linear shoals: Northeastern Gulf of Mexico. In: K.M. Bergman and J.W. Snedden, eds. Isolated Shallow Marine Sand Bodies:  Sequence Stratigraphic Analysis and Sedimentologic Interpretation. SEPM Special Publication, v. 64, p. 95-126.

Anderson, L.C., R.A. McBride, M.J. Taylor, and M.R. Byrnes. 1998. Late Holocene record of community replacement preserved in time-averaged molluscan assemblages, Louisiana chenier plain. Palaios, v. 13, p. 488-499.

Anderson, L.C., B.K. Sen Gupta, R.A. McBride, and M.R. Byrnes. 1997. Reduced seasonality of Holocene climate and pervasive mixing of Holocene marine section:  Northeastern Gulf of Mexico shelf. Geology, v. 25, p. 127-130.

Graduate Student

Jeffrey Agnew

Jeff is looking the evolution of decapod pincers (crab claws) in the Neogene of tropical America to determine the primary selective force(s) driving long-term morphologic trends in claw size and shape, be it defence, sexual selection, foraging, or parameters of the physical environment.

Post-Doctoral Student

Audrey Aronowsky
audreya@lsu.edu
Audrey is continuing her dissertation work on the phylogeny and ecology of naticid gastropods, as well as working on both the lucinid symiont and invasive corbulid projects mentioned above.