Abstract Detail



100 years of Baileyan Trends – Wood Evolution, Function and Future

Olson, Mark [1].

Shedding comparative wood anatomy of its Baileyan baggage.

I. W. Bailey’s Major Trends of Xylem Evolution (MTXE) are often hailed as a watershed in comparative anatomy, but in reality they have significantly retarded progress in the field. Though Bailey was working well within the modern evolutionary period, he used a pre-darwinian conceptual framework, with the MTXE being an attempt to arrange all plants along a primitive-specialized linear “phylogenetic” scheme. This anachronistic effort invoked tenets, such as phylogeny describing a linear scale of inexorable progress and Haeckelian “ontogeny recapitulates phylogeny,” that had been cogently rejected by evolutionary biologists well before 1918. Even judged by its own lights, Baileyan thinking was sloppy, with the key term “specialization” never defined and used in at least six different and often contradictory senses. Nevertheless, wood anatomists wholeheartedly followed Baileyan thinking for five decades, meaning that virtually the entire comparative anatomical literature until 1965 is of negligible scientific value beyond wood descriptions. There are no causal hypotheses to be found in the entire Baileyan canon, no cause ever postulated regarding what might drive the MTXE; only until 1966 (100 years after Darwin) was the first serious effort to interpret wood features as adaptive responses to the environment published. This, Carlquist’s “ecological wood anatomy” is now the framework most anatomists use to interpret wood from a functional point of view, not the MTXE. Despite consensus that much of wood structure is an adaptive response to habit and habitat, comparative wood anatomy is largely dominated by wood identification and its associated reasoning, leading to the production of atlases and character checklists. But the important questions in wood anatomy have to do with evolution (questions of function, which implies adaptation, or systematics), and neither atlases nor checklists contribute to these evolutionary efforts. To move comparative anatomy forward, anatomists should first and foremost be trained as evolutionary biologists, and thus be equipped to address questions of adaptation and systematics, and only after as anatomists or physiologists. Such training will optimally position students of xylem to address the many outstanding important questions in the evolution of xylem, such as which xylem synapomorphies characterize the major clades of vascular plants, as well as adaptive questions such has the role that xylem plays in plant climate adaptation and as a locus of selection in plant metabolic evolution. 


Related Links:
Olson, M. E. 2012. Linear trends in botanical systematics and the Major Trends of Xylem Evolution. Botanical Review. 78: 154-183.
Olson, M. E. 2014. Xylem hydraulic evolution, I. W. Bailey, and Nardini & Jansen (2013): pattern and process. New Phytologist 203: 7-11.


1 - Instituto de Biología, Universidad Nacional Autónoma de México, Botánica, Tercer Circuito s/n de Ciudad Universitaria, México, CDMX, 04510, Mexico

Keywords:
Adaptation
Evolution
Great Chain of Being
homoplasy
Systematics
xylem.

Presentation Type: Colloquium Presentations
Number: 0006
Abstract ID:716
Candidate for Awards:None


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