Biodiversity

Why is Biodiversity Important? “At least 40 per cent of the world’s economy and 80 per cent of the needs of the poor are derived from biological resources. In addition, the richer the diversity of life, the greater the opportunity for medical discoveries, economic development, and adaptive responses to such new challenges as climate change.” www.biodiv.org

Genetic diversity Each individual species possesses genes which are the source of its own unique features: In human beings, for example, the huge variety of people's faces reflects each person's genetic individuality. The term genetic diversity also covers distinct populations of a single species, such as the thousands of breeds of different dogs or the numerous variety of roses.

Species Diversity Species diversity is a measure of the diversity within an ecological community that incorporates both species richness (the number of species in a community) and the evenness of species' abundances. Species diversity is one component of the concept of biodiversity.

Diversity = Richness + Evenness richness: count of # species evenness: relative abundance of species Ecosystem A Ecosystem B 4 oak species 3 oak species bl oak = 40 bl oak = 120 wh oak = 30 wh oak = 60 r oak = 20 r oak = 20 pin oak = 10 pin oak = 0

Formula for Shannon-Wiener Index Shannon-Wiener Index denoted by  H’ = - SUM[(pi) × ln(pi)] where        SUM = summation pi = proportion of total sample represented by species i  (Divide no. of individuals of species i by total number of samples) S = number of species, = species richness Hmax = ln(S) Maximum diversity possible E = Evenness = H/Hmax

Species Evenness H’max = maximum value of H’ = ln(s) Recall from previous slide: S = number of species, = species richness Hmax = ln(S) Maximum diversity possible E = Evenness = H/Hmax J' is constrained between 0 and 1. The less variation in communities between the species, the higher J' is Note that species evenness ranges from zero to one, with zero signifying no evenness and one, a complete evenness.

Three Scales of Diversity http://images.tutorvista.com/content/biodiversity/diversity-perspectives.jpeg

Alpha Species Diversity Index Shannon-Wiener (sometimes Shannon-Weaver) Index – - Most used because it is sensitive to change in status of rare species High values of H would be representative of more diverse communities. 2.5 – 3.0 is the generally accepted range of good biodiversity in the community A community with only one species would have an H value of 0 because Pi would equal 1 and be multiplied by ln Pi which would equal zero.  If the species are evenly distributed then the H value would be high. So the H value allows us to know not only the number of species but how the abundance of the species is distributed among all the species in the community.

Example 1: Uneven plant community Species (i) No. in sample pi ln(pi) (pi) × ln(pi) Big bluestem 60 0.60 -0.51 -0.31 Partridge pea 10 0.10 -2.30 -0.23 Sumac 25 0.25 -1.39 -0.35 Sedge 1 0.01 -4.61 -0.05 Lespedeza 4 0.04 -3.22 -0.13  S = 5 Sum = 100   Sum = -1.07 H = 1.07 Hmax = ln(S) = ln(5) = 1.61 E = 1.07/1.61 = 0.66

Alpha & Gamma Species Diversity Indices Shannon-Wiener Index