Diversity and Radiation of Vertebrates

North Carolina vertebrates

Jawless fish (Agnatha) 3 freshwater lampreys

Cartilaginous fish (Chondrichtyes, sharks, skates, rays) NO COMPLETE LIST!

Bony fish (Osteichthyes)

  • marine NO COMPLETE LIST!
  • freshwater 210 (many of them small)
  • freshwater fish occurring only west of the Blue Ridge Escarpment 47
  • freshwater fish occurring on both sides of the Blue Ridge Escarpment 25
    (excluding 25 bass and sunfish introduced by humans all over the place)

Amphibia

  • salamanders 42+
  • frogs/toads 29

Reptiles

  • alligator 1
  • turtles 15 (plus 5 sea turtles, one of which nests on Outer Banks)
  • lizards 10
  • snakes 36

Birds

  • nesting 180 (including 27 only west of Blue Ridge Escarpment)
  • regular only in winter 89
  • regular only during migrations 46
  • total = 315 species that occur regularly (every year) in NC
  • additional species that have visited one or more times >100

Mammals

  • land mammals 77
  • marine mammals 32 (29 whales and dolphins, 2 seals, and West Indian Manatee, most of them infrequent visitors)
  • land mammals include 9 shrews, 15 bats, 29 rodents (which leaves only 24 larger land mammals!)
  • land mammals occurring only west of Blue Ridge Escarpment 23 (6 shrews, 4 bats, 2 rabbits, 2 squirrels, 6 other rodents, 2 carnivores, elk)

Some general rules for the diversity of vertebrates (and other organisms)

Diversity of species decreases with elevation

although some species have evolved to live at high altitudes

Diversity of species decreases with latitude

diversity is greatest in the tropics

  • mammals ... 25 species in Alaska, 160 in Costa Rica
  • birds ... 180 nest in NC, over 600 in northeastern Peru (even though the department of Loreto, about the same size as NC, has less diverse terrain with no mountains and no seacoast)
tropical climates: a quick review

between the Tropics of Cancer and Capricorn the sun is directly overhead at noon twice each year (at the summer solstice on the Tropic of Cancer just south of Key West, at the winter solstice on the Tropic of Capricorn in northern Argentina, twice a year every place in between ... on the Equator it is overhead at the spring and autumn equinoxes) ... when the sun is nearly overhead the earth heats up more, so air rises, rainfall increases ... when the sun is on the other side of the Equator at noon, air falls and moves toward the Equator along the surface to produce trade winds ... so in the tropics seasons alternate between rainy and dry ... near the Equator it rains hard all year around!

Diversity of species is less on islands than on mainland

number of species decreases both with the size of an island and with its distance from a larger landmass (continent or larger island) ... first rule of island biogeography

number of species is not affected (in the long run) by whether an island is oceanic (in deep ocean and never connected to a continent) or continental (on a continental shelf and connected during geological periods of low sea level) ... but kinds of species are affected ... continental islands have species also present on mainland (just a subset) ... oceanic islands have many endemic species

peninsulas show weak island biogeography (species reduced but not so much as on islands)

species resticted to high elevations also show island biogeography (for them mountaintops are islands)

for most fish, isolated lakes are "islands" ... fewer species than downstream rivers and many endemics

Radiations of species on islands

islands (particularly large complex ones or archipelagos of islands) often have radiations of endemic species ... a radiation is the evolution of many species from one ancestor (especially when the species are ecologically diverse and evolve in a relatively restricted time and place)

most oceanic islands (especially archipelagos) have radiations of some vertebrates ...

  • Darwin's finches (14 species) and mockingbirds (4 species) on the Galapagos Archipelago
  • honeyeaters (birds, 39 species) on the Hawaiian islands
  • anoles (lizards, >50 species) and bulfinches (birds, 5 species) in the Lesser Antilles

radiation of passeriform birds in Australia is perhaps the greatest radiation of all ... next lecture!