Dna barcodes to study and marine biological invasions
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DNA barcodes to study and marine biological invasions. What are marine invasions? Why are we interested? What are the challenges? How can DNA barcodes help? Examples of applications to invasive species problems. Marine Biological Invasions. Introduced species Exotic species

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Dna barcodes to study and marine biological invasions l.jpg

DNA barcodes to study and marine biological invasions

What are marine invasions?

Why are we interested?

What are the challenges?

How can DNA barcodes help?

Examples of applications to invasive species problems.


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Marine Biological Invasions

Introduced species

Exotic species

Nonindigenous species

Alien species

Marine species established with human assistance outside their native ranges.


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Invaders cause ecological and economic harm

Caulerpa taxifolia

Carcinus maenas

Potamocorbula amurensis

Eriocheir sinensis

Asterias amurensis


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Invasions are increasing in frequency

Marine invertebrate invasions in North American waters

Number of first reports

N=298

Ruiz et al. 2000



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Why study invasions?

Basic community ecology and evolutionary biology.

Why are some species good invaders but not others?

Why are some communities more vulnerable or resistant?

How do invaders adapt to new enviroments?

How much biogeography is natural or anthropogenic?

Conservation and economics.

For policy-makers: risk of harm.

Understand risks of intentional introductions.

How can we best protect native species?

What are effective management practices?


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What are some of the problems in studying invasions that DNA barcodes can solve?

I. Issues of identification of larvae and juveniles.

  • Invaders arrive as larvae.

  • Invaders spread as larvae.

    II. Issues of biogeography and systematics

  • Many species are cryptogenic: we don’t know if they are invaders or not.

  • Sibling and crypticspecies complexes confuse patterns of invasion

    III. Issues of taxonomy: the “simple” problem of identification of adults

  • Taxonomic expertise is scarce and overburdened.

  • Ecologists and managers lack data.


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Without solving these problems, pressing research is hindered

Mechanisms and pathways of invasion

Primary sources

Secondary spread

Propagule pressure

Native regions

Stepping stones

Community and population dynamics

Relation between diversity, disturbance, prior invasion history and vulnerability.

Management practices and assessments

Evaluating ballast water management practices; e.g., ballast water exchange.

Early detection and eradication

“This looks new? Is it invasive? What should I do?”


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I. Identifying larvae of invasive species in plankton hindered

(natural or ballast water)


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Larvae of most marine invertebrates are undescribed. hindered When descriptions are adequate, identification is slow and laborious.



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2001 in Morro Bay, California

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Target species or genera in Morro Bay, California

Macoma (multiple species)

Mytilus galloprovincialis

Protothaca staminea

Tivela stultorum


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Mytilus galloprovincialis in Morro Bay, California

Mytilus californianus

Macoma nasuta

Protothaca

staminea

Tresus nuttalli

Cytochrome b sequences discriminate species and contain regions that can be used to design species-specific primers.

1400 PCR products scored after gel electrophoresis.


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2001 in Morro Bay, California

2000

Low tide

High tide

High tide

Low tide

Average of available replicates

*incomplete

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*

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*sand

25-90% of larvae/sample were from an introduced mussel.

.


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II. Systematic and biogeographic problems in Morro Bay, California

Cryptogenic species

(modified from Cohen and Carlton 1995):

Species which cannot be reliably identified as native or introduced, frequently considered “cosmopolitan.”


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California Department of Fish and Game 2002. Introduced Aquatic Species in California Final Report.

7-20%

Cryptogenic species


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DNA data can solve the problem of cryptogenic species Aquatic Species in California Final Report.

Cosmopolitan species could be:

A single species, truly cosmopolitan.

A single species spread by human mediated transport.

3) Multiple species erroneously described as a single species.

Combinations of 2&3

Each scenario has a predicted genetic prediction (gene flow, founder effects, phylogenetic structure)


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Ophiactis savignyi: Aquatic Species in California Final Report. a pantropical species?

"most common brittlestar in the world"

-Clark 1946 in Roy and Sponer 2002.


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Pacific haplotypes found Aquatic Species in California Final Report.

in the Western Atlantic;

Indo-west Pacific

Closure of

Isthmus of

Panama

Eastern Pacific

Western Atlantic

500 bp mt-CO1


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Aquatic Species in California Final Report.Mytilus edulis”: once considered cosmopolitan.

Genetic data shows multiple, geographically disjunct species

“Mytilus edulis”


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Aquatic Species in California Final Report.Mytilus edulis”: once considered cosmopolitan.

Genetic data shows multiple, geographically separated species

Invasion of California was unnoticed because a native sibling species was already there.


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Next, decline of native mussel was unnoticed because it was replaced.

Geller, J.B. 1999.

  • DNA from museum collections from the late 1800’s shows M. trossulus in southern CA

  • M. galloprovincialis arrived in Southern CA in the 1930's

  • It has progressively spread northward and replaced M. trossulus

North

South

Braby and Somero 2006


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Carcinus maenas replaced.

1817

1980

1989

1900

1983

Sibling species also mask multiple invasions

16S mt-rRNA Geller et al. 1997



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~30% replaced.

California Department of Fish and Game 2002. Introduced Aquatic Species in California Final Report.

IV. Taxonomic issues: the “simple” job of

Identifying adults.



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The future of DNA barcoding for the study of marine invasions.

A complete Census of Marine Life/Barcoding project would include all invaders and all potential invaders.

Targeted DNA barcoding of known invaders and high risk species would provide tools now.

DNA barcoding coupled to innovations in sequence detection can speed identification of new invaders, assist monitoring efforts, and relieve taxonomic experts of repetitive identification requests.


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Taxonomic expertise is scarce and experts are overburdened. invasions.

Watersipora sp.

Mackie et al. 2005


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