Bioinformatics Education Dissemination: Reaching Out, Connecting and Knitting-together

Background for the Whippo Problem Space

The big picture of whale evolution

There is currently little debate that whales, are ungulates. That is, whales arose somewhere within the collection of past species that gave rise to the extant hoofed mammals (including deer, rhinoceroses, horses, camels, pigs and hippopotamuses). What is less clear is where in the tree they belong.

The two trees below represent different hypotheses about the evolutionary relationships among the whales and various ungulates. Within the hoofed mammals there is a well defined split between those with an even number and those with an odd number of toes. The even-toed hoofed mammals are often labeled as the Artiodactyla and include pigs, hippopotamuses, llamas, cattle, deer and goats. The odd-toed hoofed mammals go by the label Perissodactyla and include horses, zebras, tapirs and rhinoceroses. Due to the extensive morphological adaptation that occurred in the whales evolutionary lineage it is difficult to place them within the ungulates simply by counting their toes.

The evidence for these evolutionary hypotheses (trees) involve comparisons of molecular and morphological data across the taxonomic groups.

Some suggested investigations

The investigations listed here are not intended to be an inclusive list of possibilities but instead represent a first pass at some different ways that beginning researchers might fruitfully engage with this problem space. Some of these investigations could be supported with data found in this problem space while others would involve seeking additional resources. Our hope in listing these ideas is that both faculty and students will be stimulated to engage in research, curriculum development, or other types of scholarship that can be shared with this community. Our overarching goal is to support biology teaching and learning that more closely reflects the ways that biologists work with data to develop arguments and test hypotheses.

There are a group of phylogenetics questions that can be investigated including:

Living cetaceans are subdivided into two highly distinct suborders, Odontoceti (the echolocating toothed whales) and Mysticeti (the filter-feeding baleen whales), which are believed to have had a long independent evolutionary history. Is there any evidence that they represent two distinct evolutionary transitions from land to water? How would you go about testing this hypotheses with molecular data?

Modified from the original at UltimateUngulate.comThere are a variety of dolphin species that seem to have very different adaptations. For example some are adapted for a marine environment while others are found only in rivers. Are dolphins found in the Yangtze, Amazon and La Plata rivers closely related to one another? How are the different dolphin groups related to one another and the other cetaceans? (see Nikaido, et al 2001)

The taxonomic category Artiodactyla is intended to represent an evolutionarily significant group of species. That is, it should describe a monophyletic group such that all members of the group can trace their origins back to a shared common ancestor and all descendents of that ancestor are members of the taxonomic group Artiodactyla. Based on the available evidence do you think that Artiodactyla is a monophyletic group?

Modified from the original at UltimateUngulate.comWho are the whales closest living relatives? What is the evidence for and against this hypothesis and how can it be used to support that position? (see Gatesy, et al, 1999)

How have various characters such as carnivorous teeth, adaptations for communicating underwater, a nearly hairless body, and the absence of sebaceous glands evolved – that is how do they map to various hypothetical phylogenies that include hypothesized whale ancestors?

Useful introductory resources

There are several well-written popular descriptions of research in this area that can be accessed on the Internet. For additional resources including more general web sites, scientific papers and teaching materials please consult the bibliography section of this problem space.

The Whales Tale
Science News, Nov 6, 1999, by Richard Monastersky

This article describes some of the historical context around working on the evolutionary history of whales including a description of Darwin's observations of black bears swimming and feeding habits as evidence that they may be related to whales—a passage that he removed from later editions of the Origin after receiving much criticism.

The sometimes conflicting interpretation of the morphological and molecular evidence makes up the bulk of the discussion in this article. It includes descriptions of both new molecular approaches that focus on the analysis of interspersed elements and new fossil evidence that adds ear morphology to the data on ankle bone shapes.

Bones, molecules… or both?
Nature, News feature, volume 406, 20 July 2000, by Trisha Gura

This article discusses issues around building evolutionary trees using molecular and morphological data more broadly. In addition to whale evolution the sometimes conflicting lines of evidence are discussed with respect to hominid evolution. Some cautions related to the interpretation of LINE and SINE data are raised and the approach known as "total evidence" where the analysis of all available data are undertaken simultaneously is introduced.

From Where the Whale
StudyWorks! Online, October, 2001, by Dana Desonie

This article focuses more on the recent morphological evidence.

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