Lecture 9 - Species area relationships

Question 1

define community

Answer 1

all indvs of all species that inhabit area

Question 2

define species richness

Answer 2

no. species found at site

Question 3

diversity types (a, y, B)

Answer 3

alpha = richness within site
gamma = all sites
beta = turnover across sites

Question 4

Jaccard coefficient measures

Answer 4

B diversity, compare community composition of 2 sites

Question 5

Jaccard coefficient equation

Answer 5

a/ a+b+c
- a = no. both sites
- b = site 1 
- c = site 2
identical = 1, totally different = 0

Question 6

define nestedness

Answer 6

distribution of species across locations

• nested = some same species reoccur in each site
• can predict identities of species absent in smaller sites

Question 7

species area relationships (SARs)

Answer 7

how many co-occur at each site, how species richness varies within area

• S = no. species
• A = area
• c = intercept
• z = exponent (gradient dy/dx)

Question 8

species area relationships equation

Answer 8

S = cA^z

1. take log of both axes - log10 S = log10 (cA^z
2. log10 S = log10 c + z log10 A
y = c + mx)
3. c = 10 log10 c

Question 9

why are SARs non linear

Answer 9

large islands = more niches = more species

e. g. west indies reptiles = saturating curve
- intercept c = varies on taxa in region
- slope z = varies, close to 0.26 in true islands

Question 10

habitat fragmentation experiment

Answer 10

Brazilian Amazon since 1970s

- biological dynamics = mimics fragmentation common in heavily logged forest

Question 11

habitat patches

Answer 11

small isolated like islands

e.g. ediths checkerspot butterfly - monophagous, egg laying and movements locally adapted to diff host plants

Question 12

SARs in conservation (mountain peaks)

Answer 12

• peaks create island of habitats e.g. boreal mammals
• highest elevation = mixed coniferous
• mid altitudes = pinion juniper woodland
• surveyed alpha diversity on p.j
• 3 degrees increase = altitudinal shift in habitat, pj restricted to mountain tops
• reduction habitat area, all communities decline

Question 13

saturation and equilibrium

Answer 13

• mainland = shallower slope, predictor of max diversity
• most distant islands = less saturated
• alpha d. = declines with isolation

Question 14

simple null model

Answer 14

same species richness per island (e.g. lizards, amphibians)

• species present is random subset of regional species pool - lose nestedness
• species on sites with few species, also present on richer sites

Question 15

larger and smaller site species

Answer 15

large = common, rare
small = only common
- e.g. white tailed jack rabbit, Beldings ground squirrel = likely extinction