Rnr 4103 Conservation Genetics: Lect 16 Units Of Conservation

Front 1

What is an ESU?

Back 1

Evolutionary Significant Units:
A population or group of populations that merit separate management or priority for conservation because of high distinctiveness (Genetic & ecological). Definition is controversial

Front 2

Name the principles/criteria used to identify ESUs.
(3)

Back 2

–Reproductive isolation and adaptation
–Reciprocal monophyly
–Exchangeability of populations

Front 3

ESU: Reciprocal monophyly

Back 3

-all DNA sequences within an ESU must share a more recent common ancestor with each other than with lineages from other ESUs
-quick and easy approach
-ESUs should be reciprocally monophyletic for mtDNAin animals and show significant divergence of allele frequencies at nuclear loci

Front 4

ESU: Exchangeability of populations

Back 4

Individuals can be moved between populations, occupy the same niche, and perform the same ecological role without loss of fitness

-Not practical approach

Front 5

ESU: Reproductive isolation and adaptation

Back 5

•Long-term reproductive isolations (hundreds of generations) so that ESU represents a product of unique past evolutionary events unlikely to re-evolve
•Ecological or adaptive uniqueness: each unit represents a reservoir of genetic & phenotypic variation

Front 6

Name the three main schools of taxonomic classification?

Back 6

-Phenetics
-Cladistics
-Evolutionary classification

Front 7

Taxonomic Classification:
-Phenetics

Back 7

–Phenotypic similarity
–Similarity of allele frequencies
–Clustering to produce a phenogram

Front 8

Taxonomic Classification:
Cladistics

Back 8

–Phylogenetic relationships
–Group organisms that share derived traits (from a common ancestor)
–Only monophyletic groups recognized
–Only genealogical data considered
–Produce a cladogramor phylogeny

Front 9

Taxonomic Classification:
-Evolutionary classification

Back 9

-Phenetics& cladistics combined
-Usually classified based on phylogeny, but sometimes groups that are phenotypically different are recognized as separate groups (e.g. birds & dinosaurs)
-most commonly used today

Front 10

Monophyletic group:

Back 10

a group of taxa that includes all species, ancestral & derived, from a common ancestor

Front 11

Derived trait

Back 11

-trait that is only found in a particular lineage within a larger group

ex: Feathers are derived characters that distinguish birds from reptile ancestors

Front 12

How does a management unit differ from an ESU?

Back 12

-MUs don’t show long-term independent evolution or strong adaptive differentiation like ESUs
-MUs usually smaller than ESUs

Front 13

Why is it important to correctly recognize a taxon?

Back 13

•Failing to recognize a taxon can result in insufficient protection and extinction

•Identification of too many taxa wastes resources

Front 14

Give four reasons why a gene tree may differ from the true species phyloge

Back 14

1.lineage sorting
2. natural selection
3. introgresssion
4.sampling error

Front 15

lineage sorting - how can it affect gene trees?

Back 15

Different genes sort at different rates, can get discrepant genealogical relationships for different types of genes
e.g. nuclear and mtDNAgenes

Front 16

natural selection - how can it affect gene trees?

Back 16

Directional selection and balancing selection can cause gene trees to differ from species trees
•Directional
–Rapid divergence at a locus
–Estimation of sp divergence wrong
•Balancing
–Same lineages maintained in long-isolated species
–Estimation of sp divergence wrong

Front 17

introgression - how can it affect gene trees?

Back 17

•Hybridization and backcrossing can cause an allele from species X to introgress into species Y
•E.g. coyote mtDNA has introgressed into wolf populations

Front 18

Sampling error - how can it affect gene trees?

Back 18

•Genes
–Need to use many different genes or independent DNA sequences to avoid error caused by sampling too few or an unrepresentative set of loci
•Individuals & populations
–Too few or non-representative individuals are sampled for a species
–Too few geographic locations for a species are sampled

Front 19

characterizing genetic relationships
:individual-based methods

Back 19

Identify populations by identifying genetically similar individuals first then look at relationships among populations
•Dendrograms where each tip is an individual
•No assumptions about how many populations exist or where the boundaries are

Front 20

characterizing genetic relationships:
population-based methods

Back 20

•Make a dendrogram based on genetic similarity of populations

•Calculate a genetic differentiation statistic –e.g. FST

•Use a clustering algorithm to group populations with similar allele frequencies

Front 21

What does phylogeography do

Back 21

•Assesses correspondence between phylogeny & geography
•Expect geographic structuring among populations with long-term isolation (hundreds of generations)
–spp with limited dispersal, philopatry, distributions that span barriers to gene flow
•Rivers, mountains, roads
•Conservation: detecting phylogeographic structure important for identifying long-isolated populations with distinct gene pools and local adaptation
–Long-term reproductive isolation used to identify units of conservation
•Can identify biogeographic provinces containing distinct flora & fauna

Front 22

List three units of conservation discussed in class

Back 22

-Species
-Evolutionary Significant Units -Management Units

Front 23

Phylogenetic species concept

Back 23

•Monophyly–all members of a sp must share a common ancestor
–Deals better with asexuality & allopatricforms but probs with hybridization

Front 24

Biological species concept

Back 24

•Reproductive isolation & isolating mechanisms
•Criticisms
–Allopatricspp: non-overlapping pops, can’t observe reproductive barriers
–Asexual spp
–Introgression between highly distinct forms

Front 25

species (as a unit of conservation)

Back 25

•No agreement on definition of a species
1. Biological concept
or
2. Phylogenetic concept

Front 26

management units

Back 26

•Populations that are demographically independent
•Growth rates depend on birth & death rates, not immigration
•e.g. fish stocks
•Useful for short-term management
–Hunting & fishing areas, harvest quotas, population status