Make your own free website on Tripod.com

Restoration Ecology - Week 4

Genetics and Populations / Keystone Species / Reintroductions

I. Introduction
A. Island Biogeography is a powerful concept, but it considers only species number, not species quality
B. Not all species are equal, e.g. keystone species
C. Species trophic levels and lifeforms vary
D. Species exist not as individuals but as populations
E. Populations exhibit genetic variation
F. Populations have stable size or age distributions

Number at Age
Year 0 1 2 3 Total
0 1 0 0 0 1
1 2 1 0 0 3
2 5 2 1 0 8
3 12 5 2 1 20
4 29 12 5 2 48
5 70 29 12 5 116
6 169 70 29 12 273
7 408 169 70 29 676
8 985 408 169 70 1632

Proportion at Age
Year 0 1 2 3 Total
0 1 0 0 0 1
1 0.67 0.33 0 0 1
2 0.62 0.25 0.13 0 1
3 0.60 0.25 0.10 0.05 1
4 0.60 0.25 0.10 0.04 1
5 0.60 0.25 0.10 0.04 1
6 0.61 0.26 0.11 0.02 1
7 0.60 0.25 0.10 0.04 1
8 0.60 0.25 0.10 0.04 1

G. Some populations have social structure
H. Small populations are difficult to maintain
II. Genetics and Small Populations
A. Small populations are subject to rapid decline in numbers and local extinction (Overhead #1 - Fig. 11.1, Primack)
B. Three main reasons
1. Genetic problems due to loss of genetic variability, inbreeding, loss of heterozygosity and genetic drift
a. When few alleles are present there is a higher probability of their loss
i. If rare alleles constitute X% of of the gene pool
- population of N has Y copies where Y = (N x 2 copies/ ind. x X%)

For x=0.8%
N Y
10,000 800
1,000 80
100 8
-
b. Loss of heterozygosity DF = 1 / 2N (Overhead #2 - Fig. 11.2, Primack)
c. Loss of heterozygosity can be countered by immigration (Overhead #3 - Fig. 11.3, Primack)
d. Inbreeding depression (Homozygosity of deleterious genes) vs. outbreeding depression
e. Franklin (1980) suggested that at least 50 individuals needed to maintain genetic variability (based on domesticated animal populations or 500 individuals in non-domesticate populations 50/500 rule. This is the effective population size (Ne) not the actual population size (N).
f. Population geneticists define effective population size by the following formula:
Ne = 4(NmNf) /(Nm +Nf)
e.g., Consider a Florida panther population of 50 individuals, with 8 breeding males and 20 breeding females. The effective population size is: 4(7 x 23)/(7 +23) = 21.5.
2. Demographic fluctuations - due to chance variation in individual birth and death
3. Environmental fluctuations - due to variation in predation, competition, disease, resources, catastrophes, climate, etc.
C. Minimum viable population (MVP)
1. MVP - the product for any given species in any given habitat is the smallest isolated population having a 99% chance of remaining extant for 1000 years
2. Population viability analysis (PVA) - the process
3. MDA (minimum dynmaic area) can be estimated once MVP is established
4. Effects of variation (Overhead #4 - Fig. 11.11, Primack)
5. Extinction vortices (Overhead #5 - Fig. 11.12, Primack)
III. Keystone Species
A. Definition - Species that determine the ability of a large number of other species to persist in a community
B. Examples
1. Starfish (Pisaster ochraceous) rocky intertidal communities of Pacific Northwest - when Pisaster removed the mussel (Mytilus californicus) monopolized space, excluding other invertebrates and algae
2.Elephants in Africa
3.Kangaroo rats in deserts
4.Tropical figs
5. Flying Foxes (Bats of the genus Pteropsus) - many species completely dependent on these bats for pollination or dispersal. At least 186 bat-dependent species
6. Dung Beetles
7. Diadema and corals
IV. Which species to reintroduce?
A. Definitions
1. reintroducing
2. introducing
3. augmentation
B. Which ones?
1. All of them
2. Dominmant Species
3. Autotrophs
4. Rare and Endangered Species
5. Keystone Species
C. Success of reintroductions (Griffith et al 1989)
1. Greater success for game (86%) than for listed taxa (44%)
2. Greater for high quality (84%) than for poor quality (38%)
3. Greater for core (78%) than periphery or outside (48%)
4. Greater for wild-caught (75%) than for captive reared (38%)
5. Greater for herbivores (77%) than for carnivores (48%)
V. Relevance to Restoration
A.We reintroduce populations not species
B. Species vary in their functional role and importance in communities
C. Small populations are vulnerable
D. Keystone species may control the dynamics of an entire system
E. Success of reintroductions varies according to guilds
VI. Rules
A. 50 mile rule - material should come from within 50 miles of site.