Neil W. Blackstone, Ph.D.

Professor

Education

• Ph.D., 1985, Yale University
• B.A., 1976, Harvard University

Field of Interest

Evolutionary Biology

Research

The history of life is a history of the elaboration of levels or units of evolution—molecules within cells, cells within cells, cells within organisms. At each transition, conflicts between the lower level units had to be mediated in order for the higher level unit to emerge. These mechanisms of conflict mediation may themselves have been innovations that subsequently provided the raw material for further evolution. For instance, mechanisms for mediating conflicts between mitochondria and host cells (e.g., within-cell signaling with calcium, redox state, and reactive oxygen species) were likely co-opted into mechanisms of development and conflict resolution in multicellular organisms (e.g., "second messenger" systems, between-cell redox signaling, and programmed cell death).

Thus events in the history of life that are not directly related to the major evolutionary transitions may nevertheless derive from the raw material provided by these transitions. Consider the evolution of the metazoan mouth. In deriving the cnidarian-grade body plan from the poriferan-grade body plan, the body axis and mouth were principal innovations. Arguably, such pattern formation evolved to allow more efficient sequestration of resources. Nevertheless, since colonial cnidarians often encrust surfaces over which the food supply varies in time or space, such innovations could only be effectively employed if they were responsive to food-related signals. Evolution of a body axis may thus have been concomitant with the evolution of appropriate signal transduction systems. Redox signaling, implicated in the transition from cells to "cells within cells," can provide such a system if coupled to pattern-forming genes.

A levels-of-selection viewpoint can enlighten not only studies of the history of life but current ecological interactions as well. For instance, coral bleaching is one of the central environmental issues of our time. Fundamentally, coral bleaching results from the interaction of the population of photosynthetic symbionts and their host cnidarian colony. At the level of the colony, the tentacles and oral disks of polyps may represent the "core" areas of symbiont habitat, while stolons (which in the natural habitat may typically be shaded by other encrusting organisms or by the substratum itself) may serve as pathways of within-colony migration. Accumulations of symbionts in the stolon may use redox signals to trigger polyp formation and thus provide themselves with a favorable habitat. Bleaching may employ mechanisms that can also operate on a local scale within a colony, e.g., if a single polyp or patch of polyps becomes stressed, symbionts may migrate to other more favorable parts of the colony.

Generally, in my research I seek to employ evolutionary principles to provide a predictive framework for both current ecological interactions and interactions that occurred earlier in the history of life.

Publications