The Logical Basis for the use of Continuous Characters in Phylogenetic Systematics

Abstract

It has been argued that continuous characteristics should be excluded from cladistic analysis for two reasons: because the data are considered inappropriate; and because the methods for the conversion of these data into codes are considered arbitrary. Metric data, however, fulfill the sole criterion for inclusion in phylogenetic analysis, the presence of homologous character states, and thus cannot be excluded as a class of data. The second line of reasoning, that coding methods are arbitrary, applies to gap and segment coding, but quantitative data can be coded in a nonarbitrary manner by means of tests of statistical significance. These procedures, which are both objective and repeatable, determine the probability that two taxa possess an homologous character state; that is, if they have inherited a particular central tendency and distribution of individual variates unchanged from a common ancestor. Thus, the application of statistical tests to quantitative data empirically detects the presence of evolutionary change, the raw material of phylogenetic reconstruction. ᮊ 1998 The Willi Hennig Society ''I advise my philosophy students to develop hypersensitivity for rhetorical questions in philosophy. They paper over whatever cracks there are in the arguments.'' Ž .

Investigating the peopling of North America through cladistic analyses of Early Paleoindian projectile points

“…As Maddison et al (1984), Felsenstein (1988), Swofford and Olson (1990), Thiele (1993), Lieberman (1995) and, most recently, Rae (1998) have pointed out, there is no intrinsic difference between qualitative and morphometric characters as far as cladistics is concerned. The only criterion a character must fulfill for use in a cladistic analysis is that its states are homologous, and morphometric characters can meet this criterion as well as qualitative characters (Rae, 1998). The artificiality argument can also be easily refuted, for coding is no more artificial than is the decision to break up into discontinuous states what is, with few exceptions, continuously distributed morphology.…”

Why is there a lack of Mode 3 Levallois technologies in East Asia? A phylogenetic test of the Movius–Schick hypothesis

“…continuous) characters are fundamentally different from 'discrete' qualitative characters and should be excluded from phylogenetic analyses (e.g., Crisp and Weston, 1987;Pimentel and Riggins, 1987;Cranston and Humphries, 1988;Crowe, 1994). However, such a position has been rebutted by numerous authors (e.g., Baum, 1988;Chappill, 1989;Thiele, 1993;Rae, 1998;Swiderski et al, 1998;MacLeod, 2002) who have shown that qualitative characters are invariably points along a continuous scale of variation yet, confusingly, are described in a manner that merely implies 'discreteness' (e.g., 'moderately curved', 'curved', 'highly curved', etc.). As MacLeod (2002, p. 103) has wryly noted, even a seemingly unambiguous and so-called 'discrete' character such as colour, which is sometimes used by those who criticise the use of metric characters (e.g., Pimentel and Riggins, 1987), is actually a ratio-scale variable based on the frequency spectrum of reflected light.…”

“…For instance, while a character such as 'length' could arbitrarily be divided into 'long', 'medium' and 'short' character states via qualitative assessment, variations of such a character will be evident both within and between OTUs. If such states overlap, or even come close to overlapping, character state assignation will inevitably become increasingly subjective (Rae, 1998). Conversely, the use of morphometric data allows character state assignations to be made on a non-arbitrary basis via statistical analysis of character variation and difference, even in the event of some degree of overlap (e.g., Thorpe, 1984).…”

“…Several procedures have been proposed for converting morphometric data into discrete character states (e.g., Simon, 1983;Thorpe, 1984;Baum, 1988;Mickevich and Johnson, 1976;Archie, 1985;Thiele, 1993). As noted by Rae (1998), the most effective coding methods are those that assign character codes in a non-arbitrary manner on the basis of statistical inference. Indeed, as Richter (2005) has recently argued, the analysis of homology is a two-stage process, whereby putative morphological homology (i.e.…”

Maxillary sinus atelectasis in a wild born gibbon (Hylobates moloch)

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