announcements midterm exam (1 hour) next week, here in ilc. bring your field trip data and...
TRANSCRIPT
Announcements
• Midterm exam (1 hour) next week, here in ILC. Bring your field trip data and calculator, too (for after exam) Sign up next week for date for presentations
• Extra Credit Opportunities (12 points each) ASDB (5 volunteers) - contact Erin Keller• Catalina Boy’s School (1 volunteer, next week, male,
30 min drive with Lee, name and ssn needed - contact Doug or Lee)
• 2 people for October 28th, Friday, 12-2:30, Koffler 511
Marine Community Ecology
• How do marine animals get to the reef?(reproduction and dispersal)
• How and where do they land on the reef?
• What determines who wins in competition for space on rocks?
• What can rocky intertidal community tell us about species diversity in general? (intermediate disturbance hypothesis)
Marine Invertebrates - How do they reproduce and disperse?
•Eggs and sperm•Internal or external fertilization•Planktonic larvae*•Metamorphosis on the reef into adult
*Definition: larvae = a pre-adult form, often free-floating in marine invertebrates
Tadpole larvae of adulttunicate (Botryllus) above
Life cycle
http://life.bio.sunysb.edu/marinebio/shallowsubtidal.htmlR.K. Grosberg
Actinula larvaeof a hydroid
Phylum CnidariaClass HydroideaTubularia
http://raven.zoology.washington.edu/embryos/
http://www.mbl.edu/marine_org/marine_org.php?func=reveal&myID=BX10002
Veliger larvae of a snail
Phylum MolluscaClass GastropodaCalliostoma
http://raven.zoology.washington.edu/embryos/
http://www.marlin.ac.uk/species/Calliostomazizyphinum.htm
Setigerlarvae of a polychaeteworm(note gut)
Phylum AnnelidaClass PolychaetaSerpula
http://raven.zoology.washington.edu/embryos/
http://www.marlin.ac.uk/baski/image_viewer.asp?images=Server&topic=Species
http://www.marlin.ac.uk/baski/image_viewer.asp?images=Server&topic=Species
Setiger larvaeof a polychaeteWorm
Phylum AnnelidaClass PolychaetaSabellaria
http://raven.zoology.washington.edu/embryos/
http://www.mba.ac.uk/PMF/PMF_Sp_Sabalv.htm
Tailbud embryoof a tunicate
Phylum ChordataCorella
http://raven.zoology.washington.edu/embryos/
http://life.bio.sunysb.edu/marinebio/shallowsubtidal.html
Pilidium larvae of a ribbon worm
Phylum Nemertea, Micrura
http://raven.zoology.washington.edu/embryos/
http://www.nwmarinelife.com/htmlswimmers/m_verrilli.html
Veliger larvaeof a scallop
Phylum MolluscaClass BivalviaChlamys
http://raven.zoology.washington.edu/embryos/
http://www.seaotter.com/marine/research/chlamys/rubida/html/pacscallop.jpg.html
Pluteuslarvaeof a brittlestar
PhylumEchinodermataClass StelleroideaSubclass OphiuroideaOphiopholis
http://raven.zoology.washington.edu/embryos/ (above)
http://www.afsc.noaa.gov/kodiak/photo/misophiur.htm (right)
Actinotroch larvaeof a phoronid worm
Phylum PhoronidaPhoronis“horseshoe worms”
http://raven.zoology.washington.edu/embryos/ http://www.ucmp.berkeley.edu/brachiopoda/phoronida.html
Larvae
Summary of invertebrate reproduction and larvae
Most marine invertebrates have planktonic larvae
They feed and drift passively in the water untilthey settle out on the reef and metamorphoseinto the adult form.
Larvae use chemical and physical cues to tell themwhere to settle and metamorphose (key decision!)
The adults produce gametes, that develop into larvae,that are released into the water.
Some larvae travel 100s of miles, some a few feet.
What happens after the larvae find a good spot?
Sessile marine organisms compete fiercely for space
Definitions:Sessile = attached permanently or semi permanently
(eg, sponge, tunicate, bryozoan, coral, algae)Clone = a group of genetically identical individuals living in a
colonyReef = marine habitat of hard substrate (rock, coral, worm…)Intertidal = area covered and uncovered by the tides each daySubtidal = area below the intertidal
Competition for space on rocks in the intertidal
Space is ultimate limiting resource
Soup of larvae and food landing on the reef always
Sessile, clonal species fight for space on rocks
Two general ways to compete:
Be a good fighter (chemical warfare, overgrowth, fusion - beat ‘em or join ‘em)
Have abundant and frequent settlement of larvae(swamp out competitors, be the first one there)
Botryllus schlosseri(tunicate)
Fusion occursbetween close relatives
Instead of fighting withyour relatives, you fusewith them.
Benefits: larger coloniescompete better, reproduceearlier.
Costs:Reduces offspring of yourgenotype, but genespassed on in relatives.
R. Grosberg, UC Davis
Tadpole larvae of adulttunicate (Botryllus) above
Life cycle
http://life.bio.sunysb.edu/marinebio/shallowsubtidal.htmlR.K. Grosberg
Three colonies of tunicates - overgrowth in direction of arrows.Two are fused on left, one colony on right. What do you predictabout degree of relatedness between the three colonies?
http://life.bio.sunysb.edu/marinebio/shallowsubtidal.html
Two colonies on the left are probably closely related genetically,And both more distantly related to the colony on right.
http://life.bio.sunysb.edu/marinebio/shallowsubtidal.html
http://life.bio.sunysb.edu/marinebio/shallowsubtidal.htmlWhat is it? How many clones?
http://life.bio.sunysb.edu/marinebio/shallowsubtidal.html
Fusion of multiple colonies (clones) of bryozoans.Those more closely related are more fused.
http://life.bio.sunysb.edu/marinebio/shallowsubtidal.html
Another bryozoan species: Symmetry suggests one clone, but it is actually two clones! Black dots are original settlers.
Algae also compete for space on the reef
Macroalgae (brown, green and red algae)
•Settle out from spores in the water•Adults require light for photosynthesis•Incorporate toxins and calcium carbonate to deter predators (snails, fish, etc)
Division: green algae (Chlorophyta)Require most light Example: Sea lettuce (Ulva)
Division: Red algae Rhodophyta)Can grow with least lightExample: Encrusting coralline algae
Division: brown algae (Phaeophyta)Need moderate lightExample: Zoned-fan algae (Padina)
What determines species diversity?
LOTS of theories… •Time (older communities more diverse)•Competition (agreeable climate and niche partitioning leads to many species)•Stability (unchanging habitat allows many species to exist)•Intermediate disturbance (most specieswhere there is intermediate disturbance)*
* We will focus on this one today.
Intermediate Disturbance Hypothesis: Background
Connell 1972 “Diversity in tropical rain forests and coralreefs”
• Disturbance (eg, tree falls, storms) creates patchinessand new space to be colonized
•Patchwork is created across the landscape with- early and late successional species
- inferior and superior competitors
This theory is considered a non-equilibrium view of how natural communities are structured because landscape is a
patchwork of different stages of succession.
Two studies we will focus on today:
Sousa, Wayne (1979) Disturbance in marine intertidal boulderfields: the non-equilibrium maintenance of species diversity.
Lubchenco, Jane (1978) Plant species diversity in a marineintertidal community: importance of herbivore food preferenceand algal competitive ability.
Both researchers:- marine intertidal, temperate communities (California, Maine)- interested in explaining patterns of species diversity.- multiyear studies
Ultimate question: Why are there so many species?
Sousa Study (California)Boulder fields - number of Newtons to move bouldersNumber of (algae) species beneath boulders over time
Lubchenco Study (Maine)She observed two types of tidepools:
- dominated by one species of algae (seaweed)- 10 or more species in one pool
She noticed that density of snails (Littorina) varied, too
Species diversity - how to measure?
Species diversity - how to measure?
1) Count number of species (simplest)
2) Use an Index (mathematical formula)that considers relative abundance of each species as well as total number of species
Example: Shannon-Weaver Index H’
Break and activity
Contrast the likely life history characteristicsof the most abundant species on bouldersthat roll over often versus those that move seldom.
For many years, ecologists have debatedwhat is meant by disturbance. What aspects ofdisturbance did Sousa look at in his study?
Why might some snails prefer some algaeover others?
Imagine what 300 snails per meter squaredlooks like. Is this a reasonable density forsnails in this habitat? Why is this an importantquestion?