1. ________
__________
= 50
= 44-54

2. Marsupial – Eutherian differences Trophoblast and Placenta
(eutharians only)
Chorio-vitelline
Placenta
(most marsupials)
Chorio-Allantoic
placenta
(eutharians)

3. Costs of pregnancy vs. lactation

4. Offspring: number vs. size

5. Marsupial reproduction & developmental constraints
Neonatal movement to the pouch
necessitates forelimb function

6. Marsupial developmental constraints
from: Shears, K. E Constraints on the morphological evolution of marsupial
shoulder girdles. Evolution 58:

7. Marsupial – Placental Forelimb development
from: Shears, K. E Constraints on the morphological evolution of marsupial
shoulder girdles. Evolution 58:

8. Marsupial female reproductive cycles

9. Macropod marsupials
Reproductive flexibility

10. MARSUPIAL-PLACENTAL CONVERGENCE
Gliders
Burrowers

11. MARSUPIAL-PLACENTAL CONVERGENCE
Arboreal folivores
Ant-termite feeding

12. MARSUPIAL-PLACENTAL CONVERGENCE
Cursorial hind limbs

13. MARSUPIAL-PLACENTAL CONVERGENCE
Carnivory

15. ecological replacement?
Thylacine vs. Dingo
ecological replacement?

16. AUSTRALIAN MARSUPIALS Conservation issues
Disproportionate percentage of affected taxa are
small- to medium-sized and ground dwelling.
Omnivores & herbivores affected more than carnivores.
Multiple factors involved:
1) Changes in plant community structure due to:
a) browsing and grazing by exotic placentals
(livestock, rabbits)
b) altered fire ecology (decreased frequency and
increased severity of fires)
2) Introduced predators (dogs, cats, red fox)
3) Exotic diseases
a) Koala – sexually transmitted Chlamydia causing
infertility and other problems
b) Tasmanian Devil – facial tumor disease
c) Thylacine -- distemper virus implicated in decline
4) Direct hunting (extinction of thylacine on Tasmania)

17. MARSUPIAL-PLACENTAL COMPETITION
Evolutionary dominance of placentals
Predomonance of eutherians on northern continents
Contemporary Asian origin of marsupials and placentals;
more rapid spread of marsupials into southern continents
American faunal exchange (late Pliocene- Pleistocene)
Placental carnivores replaced S. American “marsupicarnivores”
Extinction of a much larger number of S. American placental
groups
Northern invasion and continued spread of didelphid marsupials
Prehistoric extinctions of Australian marsupials
Late Pleistocene extinction of most large-bodied marsupials,
possibly through human hunting or by predation/competion
from introduced dogs.
Extinctions may have been due to global climate change.
Comparable levels of extinction seen for placentals on
other continents.
Historic decline & extinction of Australian marsupials
A disproportionate percentage of historic mammal extinctions
have involved Australian marsupials. Competition from exotic
placentals has been directly implicated in some cases.
Native Australian placentals (rodents) show same dramatic
level of decline and extinction. Competition with exotic
placentals is only one of many factors endangering marsupials.