1 Introduction Ecologists usually define a population as… – Characterized by the number of individuals and their density. Additional characteristics of a population include… BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

2 Distribution Limits _____________________ limits geographic distribution of a species. – Organisms can only compensate so much for environmental variation. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

3 Niches _______: Summarizes environmental factors that influence growth, survival, and reproduction of a species. – Grinnell’s definition focused on the effects of the physical environment – Elton’s definition included biotic and abiotic factors BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

4 Niches Hutchinson defined niche as: – n equates the number of environmental factors important to survival and reproduction of a species. – ___________________ - hypervolume – ___________________ includes interactions such as competition that may restrict environments where a species may live. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

5 Kangaroo Distributions and Climate BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

6 Kangaroo Distributions and Climate Limited distributions may not be __________ determined by climate. – Climate often influences species distributions via: BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

7 Tiger Beetle of Cold Climates Tiger Beetle (Cicindela longilabris) lives at higher latitudes and elevations than most other species in NA. – Schultz et. al. found metabolic rates of C. longilabris are higher and preferred temperatures ____________ than most other species. Supports generalization that the physical environment limits species distributions. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

8 Tiger Beetle of Cold Climates BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

9 Distributions of Plants Along a Moisture- Temperature Gradient Encelia species distributions correspond to variations in temperature and precipitation. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

10 Distributions of Barnacles Along an Intertidal Gradient BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

11 Distributions of Barnacles Along an Intertidal Exposure Gradient Organisms living in an intertidal zone have evolved to different degrees of resistance to… – Barnacles show … Connell found Chthamalus stellatus restricted to upper levels while Balanus balanoides is limited to middle and lower levels. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

12 Distributions of Barnacles Along an Intertidal Gradient Balanus appears to be more vulnerable to _____________, excluding it from the upper intertidal zone. Chthamalus adults appear to be excluded from lower areas by _____________ with Balanus. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

13 Distribution of Individuals on Small Scales _____________: Equal chance of being anywhere. – _____________: Uniformly spaced. – – _____________: Unequal chance of being anywhere. – – BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

14 Distribution of Individuals on Small Scales BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

15 What pattern? Why? BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

16 What pattern? Why? BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

17 Species of aggressive stingless bees that forage over clumped resources… how would you predict they be distributed? How about passive species foraging on regularly spread resources? BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

18 Distribution of Tropical Bee Colonies – As predicted, four species with regular distributions were highly aggressive. Fifth was non-aggressive and ___________ distributed. Prospective nest sites marked with ____________. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

19 Distributions of Desert Shrubs Traditional theory suggests desert shrubs are regularly spaced due to competition but…. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

20 Distributions of Desert Shrubs Traditional theory suggests desert shrubs are regularly spaced due to competition but…. – Phillips and MacMahon found distribution of desert shrubs changes from ___________ to _________ patterns as they grow. – Young shrubs clumped for (3) reasons: BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

21 Distributions of Desert Shrubs Phillips and MacMahon proposed as plants grow, some individuals in clumps die, reducing clumping. – Competition among remaining plants produces higher mortality. Eventually creates __________ distributions. Brisson and Reynolds found competitive interactions with neighboring shrubs appear to influence distribution of creosote roots, Larrea tridentata. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

22 Distributions of Individuals on Large Scales Bird Populations Across North America – Root found at continental scale, bird populations showed __________ distributions in Christmas Bird Counts. – Clumped patterns occur in species with widespread distributions. – Brown found a relatively small proportion of study sites yielded most of records for each bird species in Breeding Bird Survey. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

23 Plant Distributions Along Moisture Gradients Whittaker examined distributions of woody plants along moisture gradients in several North American mountain ranges. – Documented moisture gradient from moist canyon bottoms up to the dry southwest-facing slopes. Tree species showed a highly clumped distribution along moisture gradients, with densities decreasing substantially toward the edges of their distribution. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

24 Plant Distributions Along Moisture Gradients BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

25 Organism Size and Population Density In general, population density declines with increasing organism size. – Damuth found the population density of herbivorous mammals decreased with increased body size. – Peters and Wassenberg found aquatic invertebrates tend to have higher population densities than terrestrial invertebrates of similar size. WHY?!? Mammals tend to have higher population densities than birds of similar size. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

26 Organism Size and Population Density BIOL 3240 Plant and Animal Ecology – Distribution & Abundance Density decreases as body size… How does aquatic invertebrate density cmopare to that of other animals of comparable size? How does mammal density compare to bird density?

27 Plant Size and Population Density Plant population density ___________ with ____________ plant size. – Underlying details are very different. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

28 Commonness and Rarity Rabinowitz devised commonness classification based on (3) factors: Populations that are least threatened by extinction, have extensive geographic ranges, broad habitat tolerances, and some large local populations. – All seven other combinations create some kind of rarity. BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

29 Rarity Rarity I – Peregrine Falcon Rarity II – Passenger Pigeon BIOL 3240 Plant and Animal Ecology – Distribution & Abundance

30 Rarity Rarity III – California Condor BIOL 3240 Plant and Animal Ecology – Distribution & Abundance