Lesson 6: Diversity and Abundance PDF

8/8/2024 1 Diversity and Abundance...

8/8/2024 1 Diversity and Abundance © Learning objectives 2 oCalculate and interpret species richness and Shannon diversity index. Distinguish between habitats that are speciose vs. even oInterpret a rank-abundance curve. oExplain what features of an environment would lead to higher or lower species diversity. Why are the tropics so biodiverse? oDefine the term biodiversity hotspot and give an example. © What makes a community diverse? 3 Photo credit: Jacky Parker/Getty Images https://www.familyhandyman.com/ar icle/wildflower-meadow/ © 1  8/8/2024 10 What is the species richness of this community? © 11 What is the species richness of this community? © Measuring Diversity 12 Community 3 Species No. Individuals pi lnpi pilnpi 1 10 0.1 -2.302 -0.2302 2 5 0.05 -2.995 -0.1497 3 0 0.00 0.00 0.00 4 0 0.00 0.00 0.00 5 1 0.01 -4.605 -0.04605 6 73 0.73 -0.314 -0.2292 7 0 0.00 0.00 0.00 8 0 0.00 0.00 0.00 9 6 0.06 -2.813 -0.1687 10 5 0.05 -2.995 -0.1497 100 1.00 H’ = (-Σ) = 0.973 What is the species richness of this community? © 4  8/8/2024 What can explain the patterns of diversity we 16 see in nature? © Environmental Complexity 17 oSpecies diversity is higher in complex habitats (typically!) oKarr and Roth (1971) found warbler diversity increased as vegetation stature (complex environment) increased. Measured environmental complexity as foliage height. oGreater the foliage height (FHD) resulted in more diverse bird communities (BSD) © Nutrient Availability 18 oThe availability of nutrients is a major determinant of biodiversity Organisms require and compete for these limiting resources oThere is a negative relationship between nutrient availability and algal and plant species diversity. Why? Competitive exclusion and eutrophication © 6  8/8/2024 19 Soil fertility vs. Species Richness According to Soons et al. (2017), the addition of nitrogen reduced plant species richness by 16% (p < 0.001). However, adding phosphorus did not alter richness. Thus, excesses of some nutrients can decrease the number of species in a habitat. © Diversity Varies Considerably Around the 20 World oSpecies diversity and richness are especially great in the tropics and generally declines in a gradient toward the poles. oLatitude and area are two key biogeographic factors that affect the species diversity of biological communities. © Biodiversity hotspots 21 oHot spots contain high numbers of endemic species (species are not found anywhere else in the world). oRecent surveys have found that diversity hot spots are mostly found in three areas of the world. Tropical areas near the equator Islands Mediterranean type ecosystems © 7