Craig Wm Schneider's Seaweed Lab

L-system computer simulations of branching divergence in some dorsiventral members of the tribe Polysiphonieae (Rhodomelaceae, Rhodophyta)

C.W. SCHNEIDER and R.E. WALDE (1992)

Phycologia 31: 581-590


A form of string rewriting systems known as L-systems is used to model the branching patterns of some genera and species in the dorsiventral members of the marine red algal (Rhodophyta) tribe Polysiphonieae (Rhodomelaceae). L-systems provide a method of deriving a set of production rules comprised of specific character strings, and these have been used previously to generate realistic computer graphic images of inflorescences, trees, ferns and landscapes. A set of production rules is developed and used to describe the branching topology of several filamentous Polysiphonieae and demonstrate that minor changes in the production rules used to generate any one of the genera will result in production rules for the others. Images with accurate branching patterns representing Aphanocladia, Dipterosiphonia, Ditria, Herpopteros, Herposiphonia, and Metamorphe have been produced. An analysis of the L-system models for these genera corroborates a plausible explanation for the evolutionary divergence of branching pattern in these taxonomically related genera and species, and supports the hypothesis that they arose from either an erect, spirally-branched or erect distichous ancestor, thus constituting independent evolutionary lines of development.

Key words: Aphanocladia, Dipterosiphonia, Ditria, Herpopteros, Herposiphonia, L-systems, Metamorphe, Polysiphonieae

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