Tangled Bank Seminar

Wednesday November 27th the Tangled Bank Seminar will be given by Scott Lidgard at The Field Museum, Chicago (IL, USA). More information on the talk soon. 

Scott Ligard Tangled Bank lecturer 2019-11-27

Enemies and Evolution: Ecological Interactions in Living and Fossil Bryozoans

Time: 13:15-14:00

Scott Lidgard
The Field Museum, Chicago (IL, USA)

Abstract

Our fundamental understanding of the taxonomy and diversification of bryozoans is based on the evolution of the zooid skeleton. Within the largest clade, Cheilostomata, the evolutionary succession from anascans through ascophorans is widely interpreted as a progressive trend increasing the extent of calcified, protective zooid skeletal armament and presumed "defensive" zooid polymorphs: spines, ovicells, and avicularia. Comparisons demonstrate that even key innovations such as these can arise convergently, following highly similar evolutionary trajectories, across long spans of geological time. A comprehensive analysis of living bryozoans considers their importance as prey for other animals, surveying 399 species in eight phyla. Multivariate analyses reveals predator trophic groups based on dissimilar feeding mechanisms, body sizes, types of locomotion and dietary breadths. Most larger-sized predators take bryozoans as minor dietary components or as incidental by-catch in their pursuit of other invertebrates living on the colonies. Mobile epibionts such as nematodes, polychaetes, and small arthropods showed greater fidelity in their bryozoan diets. Structural defenses including zooid calcification, ovicells, spines and avicularia are known to deter some small predators. These defenses and the material strength of zooid skeletons offer trivial resistance against the mechanical forces generated by larger durophagous predators such as echinoids, decapods or fishes. As an alternative, the small epibiont predators (or parasites) causing sublethal damage to colonies are likely determinants of these evolutionary trends. One may deduce that the ubiquity of skeletal defenses is in some way proportional to the fitness costs of sublethal predation by smaller animals, yet it is only part of the story, since other life history stages are unseen in the fossil record.

Biography

I am a paleontologist and marine ecologist who studies invertebrate animals, that is, most of the different kinds of animals that have ever lived on Earth. I see my research as comparative:

  • describing and explaining the history of life that actually can be observed as patterns in the fossil record, such as the changing forms of skeletons through time, or long-term trends in biodiversity,
  • jointly studying processes that can only be inferred from fossils, such as the mechanisms of actual biological interactions, or the evolution of complexity that occurs at the different levels of organism and community, and
  • comparing these with patterns and processes that can be seen in the living world, such as the development and life cycles of organisms, and the ecological processes of communities.
Publisert 11. nov. 2019 09:04 - Sist endret 24. nov. 2019 21:02