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

European Green Crab

Asian Copepod

Spartina or Cordgrass

Manila Clams

Ciona – a tunicate

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 ConceptReproductive Isolation is key, but what about hybrids?

Morphological Species ConceptSpecies differ consistently in formConcept 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 historyLamy – 1936

Described group of species including Mytilus edulis, M. galloprovincialis and M. trossulus (our native species)

Soot Ryen – 1955Lumped 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 – Pacificcoast and NW Atlantic

All species can hybridize

Mediterranean blue mussels introducedto 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

More Mussel History

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 bpM. galloprov. 126 bp

PCR Gel

Mt Hybrid Mg

168 bp 128 bp

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

41 1 1

PS Totals 136 18 70

Second question: Can we find morphological characters to distinguish

the two species and hybrids?

Length Width

And Height (not pictured)

0

10

20

30

40

50

60H

eig

ht

(mm

)

0 20 40 60 80 100 120 140 160Length (mm)

T/G

T

G

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 contributeto a growing database.