Meeting Abstract

123.6  Tuesday, Jan. 7 14:45  Variation and variability in developmental studies: An analysis of skeletal ontogeny in Monodelphis domestica. MORRIS, Z. S.; The University of Texas at Austin zsmorris@utexas.edu

The field of evolutionary developmental biology (evo-devo) has provided significant insight into the evolution of skeletal development. However, most current methods for characterizing and comparing the order of ontogenetic events do not allow intraspecific variation. The lack of data on variation in these methods limits our ability to meaningfully describe and compare ontogenies. One method that does account for and quantify developmental variation and variability is Ontogenetic Sequence Analysis (OSA). My study uses OSA to characterize levels of variation and variability in the ontogeny of the skeleton of the marsupial Monodelphis domestica. I evaluated 92 events during skeletal development using 35 specimens of known age (spanning birth to 24 days), to assess the degree to which intraspecific variation may affect the results of developmental studies. I did separate analyses for cleared-and-stained (C&S) specimens and computed tomography (CT), as it was previously shown they reconstruct skeletal maturity differently. The analysis of C&S specimens finds significant levels of sequence variation, including over 800 possible sequences. Analysis of 12 CT scanned specimens found 16 potential sequences; the smaller number a function of sample size. By recovering more than one ossification sequence for Monodelphis domestica, my study demonstrates intraspecific ontogenetic sequence variation is a real phenomenon and can be quantified. As a result, evo-devo studies that use only a single sequence are likely to overestimate differences among taxa. Variation is necessary for the timing and order of ontogenetic events to evolve and, therefore, is important for understanding how ontogeny evolves. My results emphasize that methods like OSA provide a key tool for integrating ontogenetic variation into comparative developmental studies.