Tamarix in Eurasia vs. U.S.:
Partial listing of phylogeographic differences
Eurasia
Native
All observed haplotypes evolved in situ
Single root for all haplotypes
Tip clades younger than interior clades
Lots of time for new haplotypes to evolve
Geographic distribution fairly constant
U.S.
Introduced
Most observed haplotypes evolved outside
study area
Each introduced haplotype has a separate
root (or possibly several)
Haplotypes unique to U.S. younger than
haplotypes shared with Eurasia
Little evolutionary time, but possibly a new
selective regime
Geographic distribution rapidly expanding
Expected population processes:
Eurasia
U.S.
Isolation by distance (restricted gene flow)
Multiple origins (may be confounded with
long-distance dispersal)
Extensive range expansion
Limited de novo evolution
Extensive secondary contact
De novo evolution
Limited secondary contact
Phylogeographic processes and patterns for recurrent and
historical events (endemic regions only!)
Source: A.R. Templeton, E. Routman, and C.A. Phillips. 1995. Genetics 140:767-782.
Null hypothesis:
Process
Panmixia
Effect
Geographic distribution not
correlated with evolutionary
history
Pattern
• DC and DN values random over
entire tree and at all nesting levels
Recurrent processes:
Process
Isolation by distance
Effect
Geographic distribution
correlates with age
Isolation by distance:
Short-distance dispersal
AND
adequate geographic
sampling
Isolation by distance:
Long-distance dispersal OR
poor geographic sampling
Evolutionary proximity
correlates with
geographic proximity
Evolutionary neighbors
may be geographically
distant
Pattern
• DC small for tip clades
• Large within-clade value of
DC(internal) – DC(tip)
• Larger DC at higher nesting levels
Above patterns also apply to DN
DC and DN may show different
patterns
Historical events:
Process
Contiguous range
expansion
Effect
Young (tip) haplotypes
broadly distributed
and/or distant from
evolutionary ancestors
Long-distance
colonization
Young (tip) haplotypes
distant from
evolutionary ancestors
Allopatric
fragmentation
(without extensive
2° contact)
Geographical
distributions limited;
Local populations
accumulate fixed
mutational differences
Pattern
• DC and DN large for tip clades
• Small value of DC(internal) – DC(tip)
• Small value of DN(internal) – DN(tip)
• These patterns occur in few clades and are
geographically congruent
• DC small for some tip clades
• DN large for tip clades
• Small value of DN(internal) – DN(tip)
• These patterns occur in few clades and are
geographically congruent
• Above a nesting level threshold, DC abruptly
drops and DN may abruptly rise
• Long branches separating clades with these
patterns from rest of cladogram
• These patterns occur in few clades and are
geographically congruent