Convergent Evolution of Wing Morphologies in Birds and BatsBy: Kevin Varty

Convergent Evolution• The independent evolution of

analogous structures or features.• Similar in function but

different in structure.• Features not present in the last

common ancestor of individuals in question.

• Caused by environmental pressures.

• Selection for the traits of the individuals best suited for their environment.

Convergence on the molecular level

SEBA’S SHORT-TAILED BAT

BOTTLE-NOSED DOLPHIN

Opposable ThumbsTHE GIANT PANDA CHIMPS/APES/HUMANS

Evolution of Wings

What causes these similar morphologies?• Previous studies have shown similar genetic mechanisms are

responsible for the morphologies of wings in each group of animals.

• Digit elongation• BMP Pathway genes (BMP3) (Welten et al. 2005; Sears et al.

2006; Sears, 2007; Wang et al. 2010)• Small hollow or porous bones• Sonic hedgehog (Shh) (Sears, 2007)

Seba’s Short-Tailed Bat (Carollia perspicillata)• Found in deciduous and

evergreen forests near stagnant water.

• Predominately feeds on fruit, occasionally flowers and insects.• Foraging occurs near

ground level.• Most common bat species

found in zoos today.• Relatively easy to breed.• Commonly used in studies

(Cretekos, et al. 2005; Sears, et al. 2006)

The Domestic Chicken (Gallus gallus domesticus)• A subspecies of the red

junglefowl.• Outnumbers any other

species of bird or domestic animal.

• A huge source of food for people all over the world.

• Found in almost all environments where people can be found.

• Has been used in previous studies (Zuo et al. 2016)

Aim 1Compare gene expression in the extended forelimbs of bats and birds.• Studies have shown Bmp3 to be a possible gene

responsible (Welten et al. 2005; Sears, et al. 2006; Sears, 2007; Wang, et al. 2010)

Methodology• Obtain 10 embryos from each species• Use laser capture microdissection (LCM) to take cells from

the wings of each embryo once the wings have been defined.

• Use CRISPR/Cas9 with a guide RNA sequence to knock out the Bmp3 gene in captured cells.

• Inject altered cells back into wings of embryos.• Allow test subjects to be born and reach adulthood.• Compare wingspans to established average ranges.• 45-65cm for chickens and 21-25cm for bats

CRISPR/Cas9

1:05- 2:47

Aim 1Expected Outcomes• The wingspans of test subjects will fall below established averages.• Based on previous studies (Wang, et al. 2010).

Possible Complicaitons• Death of test subjects.• Up-regulation of other BMP pathway genes• Gene knockdown versus gene knockout.

Aim 2Compare gene expression in the development of light bones in bats and in birds.• Studies have shown Sonic hedgehog (Shh) to play a role in the

reduction of length, width, and density of the ulna in bat forelimbs (Sears, 2007)

Methodology• Obtain 20 embryos from each species.• Use LCM to capture cells from the ulna of 10 embryos from each

species.• Use CRISPR/Cas9 and a guide RNA sequence to knockout the Shh

gene.• Inject altered cells back into the 10 embryos of each species.• Allow test subjects to be born and reach adulthood.• Compare ulna size 20 experimental embryos versus 20 control

embryos using dual energy X-ray absorptiometry.

Aim 2Expected Outcomes• Ulna size of the 20 test embryos will be greater than the 20

control embryos in length, width, and density.• Based on previous studies (Sears, 2007)

Possible Complications• Death of test subjects.• Up-regulation of other genes.• Gene knockdown versus gene knockout.

Broader Impacts• Increased understanding of the genetic mechanisms

behind convergence.• Increased understanding of limb development• Shaping the minds of little children.

Questions?