This project will reconstruct the evolutionary relationships among baleen whales (mysticetes) spanning 34 million years of Earth History through detailed anatomical comparisons using state of the art technologies, including high resolution CT images. The phenotypic focus is anatomy associated with low frequency hearing. It is unknown if extinct species were as sensitive to low frequency sounds as are their living descendants. Some fossil mysticetes share ear morphology similar to living whales, but hypotheses of when or how many times morphologies associated with auditory physiology evolved throughout mysticete phylogeny remain unresolved and will be studied using phylogenetic comparative methods.
The novel morphologic descriptions and analyses produced by the research will add important new information concerning the anatomical structures involved with hearing perception, and it will also lead to an increased comprehension of the effect of human activities on living whales. In addition, the data will form a foundation for newly developed science curricula for public schools through provision of novel data to California educators for use in the classroom.
A principal objective of this project was incorporation of both molecular (DNA sequences) and morphological data in a total evidence analysis of the evolutionary relationships among well preserved fossil and extant baleen whales.This data set, the largest assembled to date, includes 115 morphological characters of the skull and skeleton scored for more than 70 species of whales. This data (i.e. detailed character descriptions and associated labeled illustrations) has been entered onto a web-based site, MorphoBank that will facilitate use by other whale researchers. Results of this portion of the research suggest that gray whales are positioned outside of balaenopterids (e.g. humpback, minke, sei and fin whales). This is significant since prior molecular data had gray whales nested within balaenopterids, a result consistently obtained by analysis of the morphological data only. The rigorous, well supported phylogenetic tree that we obtained provides the necessary framework for investigating other questions such as the evolution of the ear complex, of considerable importance to whales in communication as well in navigation and feeding. A second principal objective of this research was detailed description and illustration of the ear complex of fossil and extant baleen whales using various techniques including traditional methods of dissection as well as newer technology (i.e. CT scans). Results of this research (e.g. long cochlear canals with a high number of turns, etc.) indicate that ancestral whales were sensitive to low frequency sounds which is consistent with our understanding of hearing in living baleen whales. This suggests that low frequency hearing was ancestral for whales and retained by baleen whales. High frequency sound sensitivity was later derived within the toothed whale lineage. Given the potential harmful effects of human caused noise on whales an accurate interpretation of hearing capabilities of living whales is of paramount importance and has been little studied in baleen whales. Thus, this research contributes to our knowledge of hearing in these charismatic mammals of the sea.
