Biology Reference
In-Depth Information
Morphometric Data
“We may want now and then to make use of scanty data, and find a
rough estimate better than none.”
D'Arcy Thompson (1992)
Data are collected from any object of interest in order to capture
salient features of overall form and characteristics of specific regions
defined by the scientific problem under study. The purpose of the study
might be descriptive, exploratory, comparative, or explanatory, and the
type of data used may vary with the purpose of the analysis. In Part 1
of this chapter, we introduce a variety of morphometric data types, but
we emphasize landmark data. Because we are primarily concerned
with biological inquiry, we explore the biological meaning of land-
marks, then discuss various methods of landmark data collection,
including some pitfalls, and provide a design for measurement error
studies. In Part 2 of this chapter, we give a brief introduction to matrix
algebra to clarify the mathematics necessary to work with landmark
data. These concepts are then used to develop generalized approaches
to the study of measurement error for landmark data.
2.1 Types of morphometric data
2.1.1 Unidimensional measures
A single uni-dimensional measure may be all that is needed to ade-
quately describe the form under study for a particular research
purpose ( Figure 2.1.a ). Measures like crown-rump length, head cir-
cumference, and wing span give a general indication of the overall size
of a biological form and may provide enough information to determine
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