Jr. Stone, USING SHELL PARAMETERS AS COMPLEMENTARY DATA IN PHYLOGENETIC SYSTEMATIC ANALYSES - EVOLUTION OF FORM IN 5 SPECIES OF LITTORINIDS (MOLLUSCA,GASTROPODA), The Veliger, 40(1), 1997, pp. 12-22
Gastropod shells contain records of ontogeny and so, house a wealth of
biological information. In this paper, I present a methodology for th
e analysis of shell forms which yields data that may be used in phylog
enetic systematic analyses. I use a mathematical model which considers
two aspects of a shell's aperture throughout growth, the ''aperture t
rajectory'' and the ''aperture scaling,'' to describe shell shape and
size. The aperture trajectory describes the path in space followed by
the center of the aperture from the apex to the final lip of a shell,
while the aperture scaling represents the changes in the dimensions of
the aperture along the trajectory. I treat each whorl of a shell as a
separate entity, consider horizontal and vertical components of the t
rajectory and scaling as characters, code character states in a conser
vative manner, and use them in a cladistic analysis. As an example, I
apply the method to shells of five species of periwinkles (Gastropoda:
Littorina). I obtain a phylogeny (interpreted cladogram) that differs
from recently published hypotheses derived from other types of data,
and I compare, contrast, and combine my results with these. Finally, I
discuss the assumptions and limitations of the methodology I present.