Zoogeography Flashcards
Odontocetes
- lots of variation
Examples:
a. sperm whales - deep water, wide latitudinal range (pygmy and dwarf occupy warm T latitudes)
b. narwhal (and many populations of belugas) - pagophilic, discontinuous circumpolar distribution (Arctic Ocean)
c. beaked and bottlenose whales - deep water, very cryptic, antitropical
Delphinids - d. deep, warm water (Stenella spp., Delphinus spp., Steno sp., and Lagenodelphis sp.)
e. antitropical, offshore (Lagenorhyncus spp. and Lissodelphis spp.)
f. coastal (humpback dolphins, Irrawaddy, Cephalorhynchus spp.)
g. blackfish - wide range: tropical, antitropical, and killer whale (everywhere!)
Mysticetes
- predominantly migratory (some spp. further than any other mammal) - food/energy and mating/nursing/calving
- ex.s: bowhead whale - exclusively Arctic; gray whale - limited to shelf waters but highly migratory; blue/fin/sei/humpback - cosmopolitan
Dugongs
- exclusively marine
- seagrasses in Indo-West Pacific
- sheltered warm waters (though can travel 100s of km)
West Indian manatee
- salt/brackish/freshwater
- access to aquatic plants
- coastal range: SE US to Bahia Brazil (some in EP - transplantation in 1960s)
Amazonian manatee
confined to freshwater habitats
Otariids
mostly inhabit cool temperate and subpolar (or low latitudes influenced by cold, nutrient rich currents)
2. Arctocephalus spp. - distribution affected greatly by sealing
3. Zalophus spp. - 3, distinct populations: Japanese sea lion (Z. c. japonicus - may be extinct), Galapagos sea lion (Z. c. wollebaeki), California sea lion (Z. c. californianus)
Phocids
most widespread of pinnipeds: cover most latitudes and both hemispheres
Phocinae
northern group: e.g. bearded seals, ringed seals
Monachinae
southern group: e.g. monk seals, elephant seals
Baikal seals
lake Baikal in eastern Russia
SEA otters
- Pacific coast - fragmented (exploitation); reintroduction
- coastal (obligate consumers of benthic invertebrates)
POLAR BEARS
- distribution mirrors northern phocid seals (primarily ringed seals) - live in close association with ice packs - depend on ice
- male polar bears: true nomads
all marine mammals evolved from 2 terrestrial groups:
- Order Carnivora
2. Ungulata (group) - includes 5 Orders - hooved mammals
POLAR BEARS evolution
- evidence – recent evolutionary offshoot of the
brown bear
SEA OTTERS evolution
- evolved from other mustelids (ferrets, weasels, etc.)
PhocidEvolution
- most suggest otariids evolved first and then gave rise to phocids
- monk seals – considered most basal/primitive
Otariid Evolution
- separation of fur seals and sea lions is based SOLELY on morphology: 1. underhair and 2. size
- within subfamilies – distinguished by non-overlapping ranges
Odobenid Evolution
- not sure if more closely related to otariids or phocids
- distinguished from ancestors by development of tusks - distinguished from other pinnipeds by suction feeding
Suborder Archaeoceti
– extinct by end of Eocene - tidal and estuarine habitats
- had hind limbs (fossils)
- look reptilian
3 major changes from this to fully aquatic:
- shift from 4-legged locomotion to swimming, 2. ability to drink seawater, 3. ability to give birth in water
Odontocete Origins
- not defined by retention of teeth (ancestral); possess 5 digits in flippers
- rather: telescoped maxilla, asymmetrical skulls and soft tissue of face, unique diverticula in nasal passages, hypertrophied fatty melon, one nostril echolocation
Mysticete Origins
- evolutionary transition in feeding (single prey to numerous, small prey) - evolved from cetaceans with teeth
- only extant spp. to retain 5 digits: right whales (Family Balaenidae)
SIRENIANS evolution
• related to ungulate clade that includes: elephants • have vestiges of pelvic girdle
• fossil record is taxonomically rich (but only 2 living groups: manatees and dugongs)
