presentation_21 - Lecture 21 Case histories of speciation...

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1 Lecture 21 Case histories of speciation Silverswords Tarweed Hawai’ian silverswords - ~5 MY Hawai’i Maui - Nui Oahu Kuaui
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2 Phylogeny of Hawai’ian silverswords Baldwin & Sanderson 1998 3 genera (W, D & A) Copyright ©1998 by the National Academy of Sciences Baldwin, Bruce G. and Sanderson, Michael J. (1998) Proc. Natl. Acad. Sci. USA 95, 9402-9406
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3 Rapid evolution in regulatory genes (flower, photosynthesis) in silverswords vs. tarweeds Leaf shape variation is associated with habitat Lo Annual rainfall Hi Species
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4 Outgroup (NA) genus A D W leaf shape habitat Wet: large & round Bog (physiologically dry): smaller, round or thin Dry: short or long, thin Allopatric vs. sympatric in Hawai±ian silverswords “sympatric” speciation is common (different habitats) Hawai’I (7/0) Maui - Nui (12/8) Oahu (4/2) Kuaui (13/13) (Total species / # evolved sympatrically)
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5 • Monophyletic clade of 16 species within the genus Tetragnatha • Lost the use of building webs • 4 “ecomorphs”: correspond to hunting habit & prey size • Green (A): actively moving, lives on leaves, small flying insects • Maroon (B): lives on moss, weak flying insects • Small brown (C): actively moving, lives on twigs, very small flying insects • Large brown (D): slow moving, lives on tree bark, caterpillars Spiny leg spiders in the Hawai’an Islands (~20 species; Gillespie 2004 Science 2004) Blow-up of E. Maui Distribution of ecomorphs on islands
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6 • Within any locality, 2-4 ecomorphs co-occur (not all ecomorphs are always present). • Similar sets of ecomorphs occur in most habitats, regardless of island age. • There is never more than one species of a given ecomorph at a locality.
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This note was uploaded on 09/28/2008 for the course BIOEE 2780 taught by Professor Geber during the Fall '07 term at Cornell University (Engineering School).

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presentation_21 - Lecture 21 Case histories of speciation...

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