Transcript PPT

Species conservation strategies
Leucaena salvadorensis:
genetic variation and
conservation
David Boshier
© CE Hughes
# trees in
population
No
Population, Country
1
2
Nueva Esparta, El Salvador
San Antonio, Honduras
16
224
3
Rio Nacaome, Honduras
120
4
La Garita, Honduras
500
5
La Galera, Honduras
181
6
Calaire, Honduras
700
7
Charco Verde, Honduras
8
San Juan Limay, Nicaragua
79
>1000
2
Nueva Esparta El Salvador
© DH Boshier
3
© DH Boshier
Calaire Honduras
4
© DH Boshier
© DH Boshier
San
Antonio
Honduras
© DH Boshier
Rio Nacaome
Honduras
5
© DH Boshier
6
© CE Hughes
L. leucocephala
self compatible
© CE Hughes
L. salvadorensis
self incompatible
© CE Hughes
7
8
Conservation alternatives
• preservation of actual diversity
• conservation of evolutionary potential
• mantain options for future generations,
while satisfying present needs
9
10
How big is “big enough”?
50/500 rule (Franklin 1980)
50 - inbreeding depression to acceptable level
500 - sufficient for new variation from mutation to
replace that lost by genetic drift
refers to effective population size (Ne) rather than
survey numbers (N) – so may need many
more!
in trees Ne smaller than N due to: overlapping
generations, dioecy, asynchronous flowering,
fecundity differences between individuals
11
Where should we conserve?
In situ - Ex situ
In situ - reserve system of undisturbed,
protected areas within natural distribution
(ecosystem based)
Ex situ - artificial maintenance of populations
outside natural distribution (species based)
12
Conservation of biodiversity in situ:
trees as a paradigm
ideal reserve model
emphasis: large, continuous, protected areas
limitations: location, size, security, biology:
–
–
–
–
movement of animals
extensive distribution of many species
gene flow between populations
upland, non agricultural areas
essential but not sufficient
13
Conservation of biodiversity ex situ:
methods and limitations
seed banks - problems of regeneration
plantations - changes in gene frequencies, few
populations
botanical gardens - deficiencies for gene pool
conservation
14
© RBG Kew
© RBG Kew
Conservation of biodiversity ex situ:
methods and limitations
• useful, but resources limit application to few
species (usually commercial)
• last gasp holding for highly endangered
species
• complimentary to other approaches
15
© DH Boshier
a large number of individuals of many species have
long ago ceased being ecologically (and
evolutionarily) reproductive; they flower but set no
These
are the
deadnever lead to
seed, or if they
set seed,
theliving
seedlings
Janzen 1986
recruitment of adults.
16
© DH Boshier
Where should we conserve?
• In situ - reserve system of undisturbed,
protected areas within natural distribution
(ecosystem based)
• Ex situ - artificial maintenance of populations
outside natural distribution (species based)
• Circa situm - conservation within altered
agricultural landscapes, within natural
distribution
17
Conservation of biodiversity in practice:
circa situm as a necessity?
• Majority of conservation in situ outside of reserves
emphasises:
– trees outside of forests
– role of indigenous/local communities
– role of forest and land administrators
– compatibility between resource management
systems and conservation objectives
18
Conservation of alleles
common - rare
what proportion?
widespread - localised what scale?
common
rare (<0.05)
widespread
easy
sample size
localised
key
luck
19
Widespread vs locally common
alleles
Allele a
b
c
d
Pop 1
0.500
0.250
0.230
0.020
frequency
2
3
0.320 0.450
0.030 0.050
0.400 0.450
0.250 0.050
4
0.550
0.050
0.350
0.050
20
Figure 2. Genetic similarities (Nei unbiased genetic
distance) between L. salvadorensis populations
21
Table 4. Gene flow (Nm - number of migrants per generation) below shaded
boxes and geographic distance (in km) above shaded boxes between L.
salvadorensis populations (details in Table 1). Correlation between gene flow
and geographic distance: r = - 0.17
Figure 3. Relationship between gene
flow between populations (Nm –
number of migrants per generation)
and geographic distance (km); based
on data from Table 4
22
Leucaena
salvadorensis
Conservation strategies – four groups
El Salvador (country specific strategy)
Honduras (country specific strategy)
Nicaragua (country specific strategy)
FAO (international perspective)
23
Leucaena salvadorensis
each group summarize on wall chart paper or
PowerPoint
Remember
need a conservation objective
prioritise actions – resources are limited
list the localised but common alleles?
list problems by type
- genetic, which pops. too small? which are different?
- other types of problems
which conservation methods - in situ, ex situ, circa situm?
who? will do, what? where?
how will you pay for it?
24