Island colonization and island biogeography Relevant pages in
Island colonization and island biogeography Relevant pages in Jackson: 33 -44
Colonization of oceanic volcanic islands Surtsey: “born” Nov. 1963
Colonization of Surtsey • 6 months: bacteria, fungi, seabirds, seeds • 1. 5 yrs: sea rocket (Cakile edentulata) establishing • 4 yrs: mosses establishing • 10 yrs: 13 species vascular plants, 66 species of mosses
Krakatau Island
Plants dispersed by physical forces are first to arrive in primary succession Rakata Island (post-Krakatau eruption) Forest as of 1920 Ricklefs (2001)
Colonization of the Galápagos
The “unbalanced” flora and fauna of the Gálapagos • Flora (see Table 4, Jackson) – Species with small, wind-dispersed seeds most abundant – Species with large, heavy seeds uncommon • Fauna: – Reptiles and seabirds well represented – Amphibians absent – Few mammals
Natural modes of transport • Sea – Active transport (swimming) – Passive transport (floating/rafting)
Natural modes of transport • Air – Active (flying) – Passive (floating)
Natural modes of transport • Birds – Internal (digestive tracts) – Attachment to feathers, feet
Modes of transport of plants to the Galápagos (D. Porter) • 59% by birds (77% of flowering plants bird-transported) • internal transport most common • 32% by wind • 9% by ocean drifting
Establishment: another “sieve” of natural selection
Establishment
Orchids have tiny seeds but are underrepresented on the islands
some lizards are capable of parthenogenesis
Island biogeography -64° -63° 18° -62° -61° Anguilla Guadeloupe 16° -60° 18° 16° Dominica The Lesser Antilles (Caribbean) 14° Lesser Martinique Antilles St. Lucia 14° St. Vincent 12° From Stiling (2002) -64° Grenada -63° -62° -61° 12° -60°
From Stiling (2002) 1. 2 0. 8 Reptile and amphibian species Butterfly species 1. 6 2. 0 1. 6 1. 2 0. 8 0. 4 1. 0 1. 5 2. 0 2. 5 3. 0 3. 5 Area 1. 6 1. 2 0. 8 2. 0 Bird species 2. 0 Bat species Species-area relationships among animal taxa the Lesser Antilles 2. 0 1. 6 1. 2 0. 8 0. 4 1. 0 1. 5 2. 0 2. 5 3. 0 3. 5 Area
General equation for species-area relationships S = c. Az or:
The Equilibrium Theory of Island Biogeography (Mc. Arthur and Wilson, 1963) Ŝ
Ŝfar Ŝnear
Ŝsmall Ŝlarge
island area also can influence immigration rate (the “target effect”) Gurevitch et al. (2002)
Testing island biogeography theory: terrestrial and freshwater birds From Ricklefs (2001)
Testing island biogeography theory: mangrove islands
D. Simberloff: area reduction experiment (mangrove islets) R 1 Number of species 100 WH 1 SQ 1 G 1 MUD 1 75 J 1 CR 1 IN 1 (2) Control for 1 st cut MUD 2 Control for 2 nd cut 50 50 100 225 Area(m 2) 500 1000
Simberloff: Testing effect of distance From Ricklefs (2001)
Ponds and lakes: islands in an ocean of land
Habitat islands: mountaintops (a) Nevada 17 Sierra Nevada 4 3 5 7 8 6 14 13 12 10 2 From Stiling (2002) 9 16 15 11 1 18 19 Rockies
Habitat fragmentation
- Slides: 34