What limitsinfluences distributions 1 Historical Factors factors associated

What limits/influences distributions? 1) Historical Factors – factors associated with past events or distance (in geologic time); contingency and priority effects 2) Contemporary Factors – factors operating in ecological time (e. g. behavioral, abiotic and biotic factors) that limit or affect patterns of distribution

1) Historical Factors Evidence that geologic history plays a role in distributions: A. Continental drift – Marsupial, ratite and Nothofagus distribution (vicariance explanation - fragmentation of environ; ie. splitting of a tectonic plate) in contrast to dispersal limits B. Glaciation – Temperate forest tree distributions C. Area spatially inaccessible – non-native species (e. g. starlings, cane toads, large mammals on islands, etc) D. Insufficient time (relative to dispersal speed)

How can we determine if historical or contemporary factors have affected distributions?

Examine historical record Fig. 3. 1

Examine fossil record and consider continental drift Godwana in Permian (286 -245 mya). See also Fig. 4. 7 in Krebs

Outside of range Fig. 3. 2 Do manipulative/transplant experiments

2) Contemporary factors A. Habitat selection – Why are some habitats occupied? Individuals ‘choose’ based on stimuli from: 1. 2. 3. 4. 5. Landscape, terrain Type of nesting or feeding sites Density of resources &/or conspecifics Life stage, size of individual ‘Cultural’ based on early experiences Evol’n reasons – ultimate reason(s) Ecological reasons – proximate

worst best Fig. 5. 8. Ideal distribution model of habitat selection

2) Contemporary factors A) Habitat selection – individuals ‘choose’ based on stimuli from: 1. 2. 3. 4. 5. Landscape, terrain Type of nesting or feeding sites Density of resources &/or conspecifics (aphids) Life stage, size of individual ‘Cultural’ based on early experiences Evol’n reasons – ultimate reason(s) Ecological reasons – proximate

2) Contemporary factors B. Biotic factors 1. 2. 3. 4. Limitation by competition Limitation by predation Allelopathy Mutualism

2) Contemporary factors C. Abiotic factors – means and extremes – Leibig’s rule of the minimum – Shelford’s law of tolerance – Acclimation Fig. 3. 3

How do organisms expand ranges? Modes of dispersal 1. Diffusion - gradual spread 2. Jump- movement across long distance “Colonization rates are driven not by the mean dispersal rates, but by extreme dispersal events (Krebs 2001). ” 3. Secular - spread in conjunction with adaptation

Fig. 4. 1 Zebra mussel dispersal; Sometimes all three operate together

Fig. 5. 2. Multiple causation; factors that affect realized niche