The effect of preservation on lizard morphometrics – an experimental study

Abstract

AbstractThe millions of conserved biological specimens that are stored upon the shelves of Natural History Museums across the world constitute a capital of biological information that is becoming increasingly accessible to students of various disciplines. Most students have taken measures of body size and shape of preserved museum specimens to test various elements of ecological and evolutionary theory. One possible hazard of using morphological measurements of museum specimens is that fixation and preservation may deform bodies or body parts, but most researchers implicitely assume that the magnitude of conservation-induced distortions are insufficient to jeopardize their analyses. However, no study to our knowledge has clearly quantified those possible distortions. In this study, we have measured 17 morphological variables on a set of 65 green iguanas (Iguana iguana), starting shortly after their death and then repeatedly over a two month period, a period during which they were fixated and preserved. Our aims were (1) to quantify and compare the deformation in different morphometrics frequently used in evolutionary studies; (2) to determine the amount of temporal variation that can be attributed to reader variability; and (3) to build conversion equations that should improve the reliability of morphological comparisons of life and conserved specimens. Conserved lizards revealed major reduction in snout vent length and body weight. Changes in other measured traits are more subtle, but persistent. These facts disturb analyses when using relative measurements, especially when comparing (often small) intraspecific differences or even morphological differences within populations in a temporal frame. We urge caution in using museum specimens as direct proxies for living organisms in ecological and taxonomic studies.