unresolved

1
unresolved
2
carmenensis
picta
danheimae
franciscensis
espiritensis
3
Phylogenetic species concept
Sample 195 elephants from 21 populations Four
genes sequenced Conservation implications
4

• The Evolutionary Species Concept
• E. O. Wiley. 1978, 1981, 2001.
• A species is an entity composed of organisms
• maintaining its identity from other such entities
  through time and space
• and having its own independent evolutionary fate
  and historical tendencies.
• Operationalism absent
• Fixed diagnostic differences different
  evolutionary trajectories.

5

• How many species?
• Number described 1.5 1.6 million
• Number estimated 5-6 million to 100 million.
• Species smallest evolutionarily independent unit
  (fundamental unit of biodiversity).
• Species boundaries
• geographical
• genetic (spread of alleles)
• How do species originate?
• Speciation mechanisms

6
Speciation mechanisms 1. Polyploidization A.
Autoploidy doubling of homologous chromosomes B.
Alloploidy stage in the speciation
process Plants
Nicotiana
Alloploidy
Autoploidy
n 96
7

• 1. Polyploidization
• Animals
• Occasionally produces a new
• species

Hybridization Reticulate evolution
8

• 2. Most animal speciation is visualized as
  lineage splitting.
• Y
• Basic speciation models require separation of
  gene pools
• 1. Dispersal setting up peripheral isolates.
• 2. Vicariance population subdivided by
  extraneous geological and climatic events.
• 3. Habitat segregation

typically messy
9
(No Transcript)
10
Snapping shrimp species
DNA sequence divergence
Speciation by Vicariance Asynchronous closure (3
mya)
11
Speciation by Dispersal
Representative Hawaiian Drosophila diversity
12
Hybrid zones

• Patterns of variation
• Low variation in F1s
• High variation in F2s, F3s, etc.
• A measure of variation in continuous characters
• CV coefficient of variation
• CV (s/mean) x 100

13
(No Transcript)
14
(No Transcript)
15
Secondary contact
center
16
Primary contact
17
Sympatric Speciation

• Flies (Rhagoletis pomonella)
• (1) Larvae develop in hawthorns (Crataegus)
• Native to NE U.S.
• (2) Larvae develop in apples (Pyrus)
• Introduced 300 ya
• H0 The flies belong to the same species there
  is phenotypic plasticity in use of hosts.
• H1 Speciation has occurred each species of fly
  adapted to one host species.
• Since hawthorns and apples are both within the
  range of Rhagoletis, this would represent an
  example of sympatric speciation.

18

• Flies using the two types of fruit cannot be
  distinguished morphologically (cryptic).
• But, evidence of lineage splitting
• 1. Allele frequency differs for 6 different
  proteins ? can be distinguished genetically.
• 2. Flies imprint on fruit from which they
  developed.
• Mating takes place on the fruit.
• Provides some degree of physical segregation.
• Only c. 6 of matings are between the two types
  of flies.

19

• Flies are diverging because of natural selection
• Selective agent timing of fruit ripening.
• Apples ripen early.
• Hawthorns ripen 3 weeks later.
• 1. Larvae in hawthorn fruit
• Selected to develop rapidly.
• Enables pupation prior to winter.
• 2. Larvae in apples
• Selected to develop slowly.
• Prevents emergence of adults prior to winter.
• Appears to be speciation nearing completion.