Approaches to the Study of Ecology - Wilkes University

Community Theory Kenneth M. Klemow, Ph.D. Wilkes University Pre-modern community concept Communities static entities Composition depended on: Climate Temperature Rainfall Soils Disturbance www.fws.gov/arizonaes Dynamic concept Result of work by H. Cowles Communities change over time Parameters include Species composition Relative density Due to internal processes www.oceanservice.noaa.gov Clementsian Community Concept

Introduced by Frederic Clements Dominated ecological thinking in first 40 years of 20th Century Key concepts Association Super-organismal analogy Succession with seres, converging to monoclimax. www.nceas.ucsb.edu www.tarleton.edu Association Group of coevolved species. Characteristic of climate Extends for many square miles

Characteristic species composition Can be classified Equated to super-organism Adjoining communities interface at ecotone. www.bigsurlandtrust.org Succession Deterministic, orderly change of species composition on a site. Can be classified into Primary Secondary www.nescb.org Can be classified into Hydrarch Mesarch Xerarch Consists of a series of seral stages. Relay floristics. Converge to monoclimax characteristic

of area. Equated to ontogenetic development in organism www.tarleton.edu Clementsian idea of species change along gradient Individualistic dissent Proposed by Henry Gleason in 1920s and 1930s. Communities not highly coevolved aggregations of species Instead, chance assemblages of species having overlapping tolerances for prevailing environment. Rejected deterministic, superorganismal analogy Species change along gradients by blending continuum Tight ecotones may occur when environmental change abrupt, but not necessarily true. www.botany.org

Gleasonsian idea of species change along gradient Evaluating Clements vs Gleason www.nceas.ucsb.edu www.botany.org Robert H. Whittaker Ph.D University of Illinois. Conducted analysis of woody plants Computed importance values for each species Related to obvious environmental gradient Smoky Mountains, TN Siskyou Mountains, Oregon Santa Catalina Mountains, Arizona. oz.plymouth.edu Whittakers findings Whittakers findings Siskyou Mountains, Oregon Santa Catalina Mountains, Arizona.

home.messiah.edu What if an overriding gradient is not evident? Perform an indirect gradient analysis through ordination or other statistical technique Main steps: Calculate Importance Values for each species in each community Determine Coefficient of Community (CC) for each pair of communities Determining Coefficient of Community (CC) CC = min IV Where min IV is lower Importance Value for each species Sp. C1 C2 CC

A 30 20 20 B 10 30 10 C 20 0 0 D 40 10

10 E 0 40 0 100 100 40 Tot. Generate matrix of CC values C1 C2 C3 C4 C1 100 C2

40 100 C3 10 60 100 C4 30 30 50 100 Generate matrix of Dissimilarity Indices DI = 100 - CC C1 C2

C3 C4 C1 C2 C3 C1 100 C1 0 C2 40 100 C2 60 0 C3 10

60 100 C3 90 40 0 C4 30 30 C4 70 70 50 50 100 C4 0

Determine community pair with highest DI These become endpoints of axis. C1 C2 C3 C1 0 C2 60 0 C3 90 40 0 C4 70

70 50 C4 0 C1 0 C3 20 40 60 80 100 Place other communities at Euclidean distance from reference C4 is 70 from C1, 50 from C3 C1

C2 C3 C1 0 C2 60 0 C3 90 40 0 C4 70 70 50

C4 C4 50 70 C1 C3 0 0 20 40 60 80 100 Place other communities at Euclidean distance from reference C4 is 70 from C1, 50 from C3 Drop perpendicular C1 C2

C3 C1 0 C2 60 0 C3 90 40 0 C4 70 70 50 C4

50 70 C1 C4 C3 0 0 20 40 60 80 100 Where would C2 go? C1 C2 C3

C1 0 C2 60 0 C3 90 40 0 C4 70 70 50 C4 C1

C4 C3 0 0 20 40 60 80 100 Where would C2 go? C1 C2 C3 C1 0 C2

60 0 C3 90 40 0 C4 70 70 50 C4 C2 60 40 C1

C4 C3 0 0 20 40 60 80 100 Where would C2 go? C1 C2 C3 C1 0 C2

60 0 C3 90 40 0 C4 70 70 50 C4 60 40 C1 C2 C4

C3 0 0 20 40 60 80 100 Now plot IV values for each species against community positions IV 0 C1 20 40 60

C2 C4 80 C3 100