Lecture 18- Rodents

Question 1

What percentage of Australian terrestrial mammals are rodents?

Answer 1

22%

Question 2

How many species does the order Rodentia have?

Answer 2

• 2300

- 45% of all mammals

Question 3

When did rodents evolve?

Answer 3

-65 MYA (mammals 195 MYA)

Question 4

What are the key features of rodents?

Answer 4

• molariform teeth (premolars and molars)= squarish teeth for grinding
• diastema= gap between incisors and premolars
• incisors (continuously growing and large)

Question 5

What is the weight range of rodents?

Answer 5

-4g (pygmy jerboa) to 66kg (capybara)

Question 6

What order are rats and mice etc. in?

Answer 6

-Supraorder Muroidea

Question 7

What are the two main orders of rats and mice (Muroidea)?

Answer 7

• 1 Murinae (620+ species, 11% of mammals, origin 12 MYA)

2. Sigmodontinae (380+ species, 7% of mammals)

Question 8

How did rodents get to Australia?

Answer 8

• crossed into Australia twice
• once 5 million yrs ago and then more recent (1 million yrs ago)
• from Asia (and PNG)

Question 9

What order are all the rodents in Australia?

Answer 9

Murinae

Question 10

What is the Wallace’s line?

Answer 10

• Wallace’s line= because the land masses were never connected in the last 10 million years, that is why different animals on each side
• deep ocean

Question 11

What are the second wave rodent colonizers?

Answer 11

-genus Rattus
-Second Colonizers •Pleistocene (~1 Ma) •25+ Species •Little morphological variation •High reproductive rates
•(8-12 teats)

Question 12

Who are the first wave colonizers and how do you identify them?

Answer 12

-old endemics
-have 4 teats
First Colonizers
•Pliocene (~5 Ma)
•160+ Species
•Large ecological and morphological variation
•Low reproductive rates •(4 teats)

Question 13

What are the characteristics of the Anisomyni?

Answer 13

New Guinea Endemics 12 genera Australia 1 genus, 1 species

-large terrestrial

Question 14

What are the characteristics of Pogonomys?

Answer 14

-arboreal

Question 15

What are the characteristics of Hydromini?

Answer 15

• the aquatic and terrestrial carnivores

- 10 genera Australasia Australia 2 genera, 2 species

Question 16

What are the characteristics of the Uromyini?

Answer 16

Generalized ‘rats’ 4 genera Australasia Australia 2 genera, 6 species

• live in wet tropics rainforest
• the other live in rainforest, grasslands and monsoon tropics
• 600-700g

Question 17

What are the characteristics of the Conilurus species group?

Answer 17

• Australian Endemics 3 genera, 6 species, 2 recently extinct
• tree rats
• stick nest rats (build stick nests)
• rabbit rats

Question 18

What are the characteristics of the Pseudomys species group?

Answer 18

-Australian Endemics 5 Genera, 42 species
-live everywhere
Pseudomys= biggest group in Australia
Pseudomys= everywhere except the tropics
-then Australian lemming-grass feeding
-rock rats
-hopping mouse
-short tail rats
-false mice

Question 19

How many species are there in the genus Rattus?

Answer 19

7 species (+2 extinct from Christmas Island) 18+ species New Guinea
--bush rat= one of the most widespread

Question 20

Why is there so much diversity in rodents? (Muronia)

Answer 20

• adaptable, live in diverse habitats,diversify in form as they colonize
• hopping mice = in American and Australia=== developed independently
• converge in having one of the most efficient kidney= never need to drink water, get it from break down of fats

Question 21

Are rodents declining in Australia?

Answer 21

• some are

- 29% of species are in decline

Question 22

What is the situation with Leporillus apicalis and Leporillus conditor?

Answer 22

• Leporillus apicalis=EXTINCT

- Leporillus conditor= Extinct on mainland Captive breeding, Reintroduction, only in Franklin island now

Question 23

Why does colonization lead to the diversification of species and forms?

Answer 23

1. Ecological opportunity
2. Key Innovation
3. Morphological Disparity

Question 24

What is the story with the Australian stick nest rat and the American Wood Rat?

Answer 24

• both build stick nests
• stick nest rats= build stick nets to protect from carnivores
• wood rats= independently developed wood nests that are passed down the generations and protect them

Question 25

What is special about the Sulawesi Paucidentomys vermidax?

Answer 25

Carnivore =don’t have chiseling incisors as they should
Their teeth don’t wear as much
-no molar teeth (unlike other rodents)
-this development of teeth happened in a few other species (one in the philippines)
-they are not closely related
-the water rats also not closely related
-high convergence in rats