INVESTIGADORES
MATTONI Camilo Ivan
artículos
Título:
Continuous characters analyzed as such
Autor/es:
GOLOBOFF, P. A., C. I. MATTONI & A. S. QUINTEROS
Revista:
CLADISTICS (PRINT)
Editorial:
Blackwell Publishing
Referencias:
Año: 2006 vol. 22 p. 589 - 601
ISSN:
0748-3007
Resumen:
Quantitative and
continuous characters have rarely been included in cladistic analyses of
morphological data; when included, they have always been discretized, using a
variety of ad hoc methods. Since
continuous characters are typically additive, they can be optimized with well
known algorithms, so that with a proper implementation they could be easily
analyzed without discretization. The
program TNT has recently incorporated algorithms for analysis of continuous
characters. One of the problems that has
been pointed out with existing methods for discretization is that they can attribute
different states to terminals that do not differ significantly or vice
versa. With the implementation in TNT,
this problem is diminished (or avoided entirely) by simply assigning to each
terminal a range that goes from the mean minus one (or two) standard deviation
to the mean plus one (or two) standard deviation; given normal distributions,
terminals that do not overlap thus differ significantly (more significantly if
using more than one standard deviation).
Three real data sets (for scorpions, spiders, and lizards) comprising
both discrete and quantitative characters are analyzed to study the performance
of continuous characters. One of the matrices has a reduced number of
continuous characters, and thus continuous characters analyzed by themselves
produce only poorly resolved trees; the support for many of the groups
supported by the discrete characters alone, however, is increased when the
continuous characters are added to the analysis. The other two matrices have larger numbers
of continuous characters, so that the results of separate analyses for the
discrete and the continuous characters can be more meaningfully compared. In both cases, the continuous characters
(analyzed alone) result in trees that are relatively similar to the trees produced
by the discrete characters alone. These
results suggest that continuous characters carry indeed phylogenetic
information, and that (if they have been observed) there is no real reason to
exclude them from the analysis.