The Holy Grail of the Perfect Character: The Cladistic Treatment of Morphometric Data

Abstract

Abstract— Data scored for cladistic analyses may be quantitative or qualitative, continuous or discrete, and show overlapping or non‐overlapping values between taxa. Quantitative and qualitative are modes of expression of data, while continuous or discrete refer to properties of the set of numbers that express the data; both these pairs of terms have been confused with overlapping and non‐overlapping. The degree of overlap of values between taxa is often used to filter characters in cladistic analyses: if a minimum amount of overlap is exceeded, or a minimum amount of disjunction not reached, characters are rejected as “not cladistic". However, this rests on a confusion between features of taxa and features of individual organisms (attributes). Cladistic characters are features of taxa, and comprise frequency distributions of attribute values over individuals of a taxon. Cladistic characters logically cannot overlap, although taxa may have overlapping attribute values. Thus, a priori rejection of characters that have overlapping attribute values is non‐sensical. Such data may still be rejected from consideration for cladistic analysis if it could be demonstrated that they contain little recoverable phylogenetic signal. Few published analyses have empirically tested this. An analysis of overlapping morphometric data from three series of Banksia suggests that, at least in these cases, they map phylogeny almost as accurately as more conventional, qualitative morphological data. While more such tests are required, morphometric data should not be rejected a priori from cladistic analyses.

Insights on Using Morphologic Data for Phylogenetic Analysis in Sedges (Cyperaceae)

“…These quantitative characters are both discrete and continuous. Inclusion of continuous data in phylogenetic analyses often improves the resolution of phylogenetic trees, even when the ranges of values for different character states overlap (Thiele, 1993;Poe & Wiens, 2000;Wiens, 2004;Garcia-Cruz & Sosa, 2006). Many of the species in the ingroups are separable primarily by continuous characters (Bryson & Naczi, 2002a;Naczi, 2002;.…”

The future role of bio-ontologies for developing a general data standard in biology: chance and challenge for zoo-morphology

“…Compared to molecular data, morphological descriptions seem to be inferior with respect to transparency and reproducibility of their production. The apparent weakness of morphological characters has been addressed in a series of papers by Wiens and Jenner within the framework of phylogenetic methodology (e.g., Wiens 1995;Hillis and Wiens 2000;Poe and Wiens 2000;Wiens 2001Wiens , 2004Jenner 2002Jenner , 2004aJenner , 2004bJenner , 2004c; see also Pimentel and Riggins 1987;Stevens 1991;Thiele 1993;Kesner 1994;). According to these authors, morphological character matrices build by one phylogeneticist are often treated like a black box by other phylogeneticists, and it becomes a question of authority rather than scientiWc argumentation whether one should rely on a phylogenetic character statement of another phylogeneticist.…”

Morphological support for a clade comprising two vermiform mite lineages: Eriophyoidea (Acariformes) and Nematalycidae (Acariformes)

“…CI = consistency index; RI = retention index; RC = rescaled consistency index. Note that the values in the left column associated with two of the ratio characters (2 & 3) refer to discretized ratios (Thiele, 1993) that range from 0 to 3. (G) or (GC) indicates that the synapomoprhy unites only more derivative members of Nematalycidae with Eriophyoidea (G=only Gordialycus; GC = only Gordialycus and Cunliffea).…”

“…All of the multistate characters are unordered except the three ratio characters, which were discretized into four character states (Thiele 1993). The ratio characters are ordered because the integers (0-3) are arbitrary divisions along a continuum.…”

“…Fossil Endeostigmata were excluded because of their poor were no specimens available for measurements, data were obtained from measurements of figures from the descriptions. The ratios were log transformed and then discretized into integers from 0 to 3 in accordance with Thiele (1993).…”