What is Biodiversity?

Transcription

1 Biodiversity in Plants What is Biodiversity? Latitude & Diversity in Birds in the New World High Species Richness High Threat of Extinction High Endemism Gaston and Blackburn 2000

2 More species in Tropics! Noted by Darwin & by Wallace Why? Quick Primer to Diversity Measures Species Richness: number of species in a given area/plot -! How certain are scientists that they have catalogued all species in plot? -! Is this a fair/adequate measure of biodiversity? Species Abundance: Rothamsted Moths (collected during a single night in 1935 Rare Species Common Species Number of Species Rare species are common Common species are rare Classic example by Preston (1948: Relationship between number of species and number of individuals sampled Figure from Dobson 1998 Number of Individuals Represented in Sample! 6814 individuals collected! 197 species total! 6 species comprise ~! all individuals! 1 species comprise ~ " all individuals! 37 species represented by single individual

3 Preston s Log-normal Distribution" Number of species Number of individuals represented in sample Rothamsted, UK Lepidoptera light trap catch Figure from Dobson 1998 Number of species Number of species Data from Preston 1948, figure from Molles 2005 Number of individuals Number of individuals Sample of 87,000 moths from Canadian prairie reveals only part of the distribution Sample with 300,000 moths reveals more of the distribution Species abundance curves Patterns of abundance No. of species few many No. of individuals abundant not abundant! A few abundant species dominate! Many nonabundant species!number of species that are rare are common!number of species that are common are rare

4 Species Number Weighted by Sample Size Forest Diversity: Which forest is most diverse? "!"#$"%&'(*+,-&./*!*0*1"2345%,1#4*!&,67,789(*+,-&./*!$%$"&'#$ Explicitly consider sample because number of species discovered increases with the number of individuals sampled (non-linear, could be logarithmic. Forest A " "Forest B " "Forest C" Hemlock " "Hemlock " "Hemlock" Beech " "Beech " "Beech" Red Maple" "Red Maple" "Red Maple" Yellow Birch" White Ash" Black Cherry" Basswood" Which forest is most diverse?" Species Diversity: Components" Species Richness = number of species present " Evenness = degree of similarity in relative abundance of different species" Forest A Forest B Forest C Hemlock Beech Red Maple Yellow Birch 1 White Ash 1 Black Cherry 1 Basswood 1!Forest A: high richness and low evenness!forest B: low richness and high evenness!forest C: low richness and moderate evenness HOW CAN WE COMBINE THE TWO?

5 S i as a diversity measure Simpson s index of evenness = the proportion of the individuals in the community belonging to species i S i = 1/ (! 2 Shannon-Wiener Diversity Index# s H' = -" ( (log e i=1 H = value of Shannon-Wiener index " s = number of species in community" = proportion of the ith species" log e = the natural log of "!Incorporates both species richness and evenness"!gives more weight to common species " Calculating H' " Number Proportion ( log e ( (log e Hemlock Beech Red Maple Yellow Birch White Ash Black Cherry Basswood TOTAL Calculating H' " Number Proportion ( log e ( (log e Hemlock Beech Red Maple Yellow Birch 0 White Ash 0 Black Cherry 0 Basswood 0 TOTAL s H' = - " ( (log e i= s H' = - " ( (log e i=1 1.10

6 Which forest is most diverse?" Forest A Forest B Forest C Hemlock Beech Red Maple Yellow Birch 1 White Ash 1 Black Cherry 1 Basswood 1 H' vs. Species # Scales of Species Diversity" Alpha Diversity = local diversity within a uniform habitat type (i.e., within-habitat diversity" Beta Diversity = among-habitat diversity"! Measured as rate of species turnover between habitats "! Often expressed as Gamma/Alpha diversity" Gamma Diversity = number of species observed in all habitats within a region (i.e., regional diversity" Robert Whittaker" Scales of Diversity" Beta Diversity" Region 1 Alpha (species per mountain Gamma (species per region Beta (gamma/ alpha Beta diversity between two communities A B C D E F B C D E F A B C D E F G # = 6 $ = 7 % = 1.2 Jaccard similarity = C/(C + U 1 + U 2 Region 2 Sorenson similarity = C/((S 1 + S 2 /2 A Region 3 B C D E F G D G H I J # = 4 $ = 10 % = 2.5 C = number of species in common U = number of unique species S = number of species A B C E D F H G I # = 3 $ = 9 % = 3.0 Range 0 (dissimilar to 1 (identical Beta diversity is turnover in diversity across habitats

7 Beta Diversity" Which Mountain Do I Conserve? Species Island 1 Island 2 Island 3 A B C D E F G :7;-7<&#7=>*?&"@#&*8",*A&*8"%&*-&B&,-&,=* Greater distance = Smaller J (more diff Beta diversity (change in J increases from N to S Why? :7;-7<&#7=>*?&"@#&*?">*,&&-*=;*7,8;#B;#"=&*&<&,,&* C@#,;<&#D* General Patterns with Species Diversity! Species-area relationship! Latitude, environmental heterogeneity and habitat Productivity! More species in Tropics. Why? -! Non-equilibrium, Time hypothesis -! Equilibrium, balance between loss and gain of species (but why do they differ?

8 Species-area relationship! More species are found in larger areas than in smaller ones! S = c A z! log S = log c + z log A Larger area, more species WHY? 1.! Sampling 2.! Habitat variation 3.! Unique evol lineages across continents Islands Also Follow Species-area Relationship Birds of Solomon Islands Diamond and Mayr 1976 Number of species increases with island area. Why?! Previous three factors + probability of extinction/ colonization. How? 1 Large islands are better targets (more colonists 2 Large islands have bigger populations (less likely to go extinct. Equilibrium balance between extinction and colonization (we ll come back to this later on.

9 Islands Also Follow Species-area Relationship Anoles of the Carribean Losos and Schluter 2000 Why? General Patterns with Species Diversity! Species-area relationship! Latitude, environmental heterogeneity and habitat productivity can explain large scale patterns of diversity Latitudinal Gradient N to S gradient: Temperature/prod E to W gradient: Environ het Isolated: Dispersal

10 Within region (latitude: Habitat Complexity Within region (latitude: Habitat Complexity Within region (latitude: Productivity Within region (latitude: Productivity IJC/*I;=&,K"%* L"=&#*=6"=*8",*A&*&<"B*'#;?*;7%* ",-*=#",B7#&-*A>*B%",=M*$7<&,* E6>D* F*G&?/*C&?B*<"#7"A%&* E6>D* H*G&?/*C&?B*,;=*<"#7"A%&* Q&B#&&,=*R"=*S#"-7&,=* E6>D* "4! S#&"=&#*JM*?;#&*B&87&* A4! S#&"=&#*JM*A7$$&#* &.K,8K;,4* 84!!;#&*B;=&,K"%*';#*

11 Back to the Tropics vs. Temperate! More ecological niches! Intermediate Disturbance! Herbivore and Pathogen! Random ecological drift