The Invasive Mussel Project
(IMP)
Peter Wimberger and Lyle Rudensey
Genetics and Exotic Mussels
• Marine Invasive Species
• Blue Mussels and the Species Problem
• Blue Mussels on the West Coast and Puget
Sound
• Genetic Monitoring of
the Mediterranean
Blue Mussel
Spartina or Cordgrass
European Green Crab
Manila Clams
Ciona – a tunicate
Asian Copepod
Where do they come from?
Shipping – ballast water
Aquaculture
Why are they a problem?
• Take over space/ outcompete natives
• Introduce Disease
• Economic Impacts ($100 billion/year!)
• Impact Endangered and Threatened Species
• Predators
• Hybridize with native species
SPECIES CONCEPTS
Biological Species Concept
Reproductive Isolation is key, but what about
hybrids?
Morphological Species Concept
Species differ consistently in form
Concept that is most used
In practice –
Species are: a) groups of individuals or
populations that are reproductively isolated from each
other or b) groups that for the most part retain their
genetic identity over most of their range.
A little mussel history
Lamy – 1936
Described group of species including Mytilus
edulis, M. galloprovincialis and M. trossulus
(our native species)
Soot Ryen – 1955
Lumped all species together as subspecies
and races of M.edulis
Numerous workers – early 1990s
Resurrect earlier 3 species as result of genetic
work
Mytilus edulis – north Atlantic (both coasts)
Mytilus galloprovincialis – Mediterranean
and Atlantic to England
Mytilus trossulus – “Our” native – Pacific
coast and NW Atlantic
All species can hybridize
More Mussel History
Mediterranean blue mussels introduced
to Pacific coast early 20th century through
ballast water.
Now used extensively in aquaculture (meatier,
grows quickly, disease resistant)
Taken over southern Californian coastline,
established in SF Bay, increasingly common
in Washington and BC
Blue Mussels are Sibling Species
- very tough to tell apart
trossulus
gallos
hybrids
Genetics can do the trick!
PCR – Polymerase Chain Reaction
Way of making LOTS of specific piece of DNA
Revolutionized molecular biology– Nobel Prize ‘92
How does PCR work?
PCR Genetic Markers
Now, a number of genes w/ unique
alleles in the three species
Byssal Thread Protein variants
M. edulis
180 bp
M. trossulus 168 bp
M. galloprov. 126 bp
PCR Gel
168 bp
128 bp
Mt
Hybrid
Mg
We know little about spread of gallo
mussels in Puget Sound/WA
• First documented 1979
• Small surveys documented presence of
gallos and hybrids in Puget Sound and Strait
of Juan de Fuca in past 10 years
• Culture of gallos spreading including to SJI
• We have found hybrids throughout Puget
Sound
Aquaculture will increase
Potential ecological impact
- unknown
• In southern California, gallo now only
mussel in intertidal
• In South Africa, gallo mussels have taken
over parts of intertidal and altered
community structure
• Here - ? Behooves us to know where it is
and determine potential ecological
effects
First question: where are gallos?
Location
Trossulus
Gallo
Hybrids
Totten Inlet
27
12
25
Tacoma
36
0
19
South
Sound
PS Totals
41
1
1
136
18
70
Second question: Can we find
morphological characters to distinguish
the two species and hybrids?
Length
Width
And Height (not pictured)
60
Heigh t (mm)
50
40
G
T
30
T/G
20
10
0
0
20
40
60
80
10 0
Le ngth (mm)
12 0
14 0
16 0
Take-home messages
•Genetics provides a reliable way
of distinguishing mussel species
and hybrids
•Shape isn’t a reliable indicator
of species identity
•Even though you can’t tell a
book by its cover, size does
matter – mussels over 65 mm are
probably gallos or hybrids.
IMP participants (IMPS) can
monitor and measure mussels
near their schools and contribute
to a growing database.