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    Migration: From Demes to Species...and back again?

    The Family Cervidae includes a variety of species we commonly call deer, elk, and moose.

    Deer first appear in the fossil record in Mongolia about 10-20 million years ago.

    Ancient deer crossed the (now vanished) land bridge between Asia (Bering Strait) and Alaska (Seward Peninsula).

    They dispersed southward and eastward, diversifying and populating North America.

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    Odocoelius Sister Species

    About a million years ago, genus Odocoileus diverged into two sister species we recognize today as

    Black-tailed or Mule Deer (Odocoileus hemionus)

    White-tailed Deer (Odocoileus virginianus)

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    Field Marks: Antler Shape

    A field mark (a.k.a. "differential" or "diagnostic" character)
    is a morphological trait used to correctly identify a species.

    White-tailed and Mule deer can be distinguished by several field marks.

    • Male White-tails have curving, "candelabra" antlers (left)
    • Male Mule Deer have branching, bifurcating antlers (right)

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    Field Marks: Forehead Coloration

    • White-tailed Deer have foreheads the same brown as the rest of the face.

    • Mule Deer have foreheads distinctively darker than the rest of the face, even at birth.

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    Field Marks: Escape Gait

    White-tails gallop to escape a predator.
    • Gallop: at least one foot is always on the ground.
    • Galloping is an effective escape gait on flat terrain.

    Mule Deer stot to escape a predator.

    • Stot: all four feet strike and leave the ground together.
    • Stotting is an effective escape gait on hilly terrain.

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(click on pic for source)

    Renewed Sympatry

    Ancestral Odocoileus branched into two species
    • allopatry
    • independent mutations
    • genetic drift
    • natural selection

    The removal of large predators contributed to range expansion by both species.
    There are now regions where the two species are sympatric.

    In these areas, limited hybridization has been documented.

    Review the levels of reproductive isolation before you try the bonus questions.

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(click on pic for source)

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    Hybrid Zones and Introgression

    A hybrid zone is an area of secondary contact between two related species, where limited hybridization is taking place between them.

    Introgression is the introduction of alleles from the gene pool of one species into that of another (closely related) species, due to limited hybridization.

    We haven't said anything about antlers or foreheads yet.

    But that doesn't mean I've forgotten about antlers and foreheads.

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Bambi Mother GIF from Bambi GIFs
    Bambi and That Other Guy
    (Or: Why You Should Never Go to the Movies with a Biologist)

    In 1942, Walt Disney Studios produced the classic animated film Bambi.

    It was based on the book by Austrian author Felix Salten.

    In Salten's book, Bambi and his family were Roe Deer (Capreolus capreolus), native to Salten's Austria.

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    Doing the Disney

    Disney studios is located in Southern California,
    where the native deer are Mule Deer.

    Disney was famous for his attention to detail and insistence that animated characters move naturally and realistically.

    To be sure his animators knew how real deer behaved and moved, he

    • brought White-tailed Deer (from Maine) into the studio
    • had the animators take field trips to local deer farms to study the native Mule Deer.

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    The Artistic Result

    Here are Bambi and his father.
    Note the antler and forehead field marks.

    Disney transformed Salten's Roe Deer into Mule Deer

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(stotting appears at 00:43 in the video)

    Further Evidence: Stotting

    On his first trip to the meadow, Bambi is enthralled by the athleticism of his male relatives.

    Although Disney called this scene "The Gallop of the Stags"
    the bucks are not just galloping.

    They are also stotting.

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    Confusion and Twitterpation

    The animators' study of both White-tailed Deer and Mule Deer created some Hollywood confusion when it came time for Bambi's mating season.

    You might remember when grown-up Bambi met grown-up Faline
    (a doe he had known as a fawn).

    He fell so in love he became "twitterpated".

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(Clear view of the tails at 1:15)

    Faline's Choice

    Bambi's romantic dream was rudely interrupted when he was challenged by another buck ("Ronno") for Faline's affections.
    (And yes...it happens in real life, too. Watch the video.)

    But wait. Examine the rival's antlers.
    What's wrong with this picture?

    Hold that thought.

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Hybrid Speciation

When closely related species hybridize, several outcomes are possible.

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(click for source)

    The Future of Oedocoileus Species

    Which brings us back to Our Friend Oedocoileus.

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