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Title: Announcements 1 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 Boys 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, 12-230, Koffler 511
  • 2
  • 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)
  • 3 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
  • 4 Life cycle Tadpole larvae of adult tunicate (Botryllus) above http// al.html R.K. Grosberg 5 Actinula larvae of a hydroid Phylum Cnidaria Class Hydroidea Tubularia http// php?func revealmyIDBX10002 http// 6 Veliger larvae of a snail Phylum Mollusca Class Gastropoda Calliostoma http// http// Calliostomazizyph inum.htm 7 Setiger larvae of a polychaete worm (note gut) Phylum Annelida Class Polychaeta Serpula http// http// viewer.asp?im agesServertopicSpecies 8 http// gesServertopicSpecies 9 Setiger larvae of a polychaete Worm Phylum Annelida Class Polychaeta Sabellaria http// http// 10 Tailbud embryo of a tunicate Phylum Chordata Corella http// http// al.html 11 Pilidium larvae of a ribbon worm Phylum Nemertea, Micrura http// http// i.html 12 Veliger larvae of a scallop Phylum Mollusca Class Bivalvia Chlamys http// http// /r ubida/html/pacscallop.jpg.html 13 Pluteus larvae of a brittle star Phylum Echinode rmata Class Stelleroidea Subclass Ophiuroidea Ophiopholis http// (above) http// m (right) 14 Actinotroch larvae of a phoronid worm Phylum Phoronida Phoronis horseshoe worms http// http// .html 15 Larvae 16 Summary of invertebrate reproduction and larvae Most marine invertebrates have planktonic larvae They feed and drift passively in the water until they settle out on the reef and metamorphose into the adult form. Larvae use chemical and physical cues to tell them where 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. 17 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 colony Reef marine habitat of hard substrate (rock, coral, worm) Intertidal area covered and uncovered by the tides each day Subtidal area below the intertidal 18 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) 19 Botryllus schlosseri (tunicate) Fusion occurs between close relatives Instead of fighting with your relatives, you fuse with them. Benefits larger colonies compete better, reproduce earlier. CostsReduces offspring of your genotype, but genes passed on in relatives. R. Grosberg, UC Davis 20 (No Transcript) 21 Life cycle Tadpole larvae of adult tunicate (Botryllus) above http// al.html R.K. Grosberg 22 http// al.html Three colonies of tunicates - overgrowth in direction of arrows. Two are fused on left, one colony on right. What do you predict about degree of relatedness between the three colonies? 23 http// al.html Two colonies on the left are probably closely related genetically, And both more distantly related to the colony on right. 24 What is it? How many clones? http// al.html 25 Fusion of multiple colonies (clones) of bryozoans. Those more closely related are more fused. http// al.html 26 Another bryozoan species Symmetry suggests one clone, but it is actually two clones! Black dots are original settlers. http// al.html 27 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)
  • 28 Division green algae (Chlorophyta) Require most light Example Sea lettuce (Ulva) Division brown algae (Phaeophyta) Need moderate light Example Zoned-fan algae (Padina) Division Red algae Rhodophyta) Can grow with least light Example Encrusting coralline algae 29 (No Transcript) 30
  • 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 species
  • where there is intermediate disturbance)
  • We will focus on this one today.
  • 31
  • Intermediate Disturbance Hypothesis Background
  • Connell 1972 Diversity in tropical rain forests and coral
  • reefs
  • Disturbance (eg, tree falls, storms) creates patchiness
  • and 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.
  • 32
  • Two studies we will focus on today
  • Sousa, Wayne (1979) Disturbance in marine intertidal boulder
  • fields the non-equilibrium maintenance of species diversity.
  • Lubchenco, Jane (1978) Plant species diversity in a marine
  • intertidal community importance of herbivore food preference
  • and 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?
  • 33 Sousa Study (California) Boulder fields - number of Newtons to move boulders Number of (algae) species beneath boulders over time 34 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 35 Species diversity - how to measure? 36 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 37 Break and activity 38 Contrast the likely life history characteristics of the most abundant species on boulders that roll over often versus those that move seldom. 39 For many years, ecologists have debated what is meant by disturbance. What aspects of disturbance did Sousa look at in his study? 40 Why might some snails prefer some algae over others? 41 Imagine what 300 snails per meter squared looks like. Is this a reasonable density for snails in this habitat? Why is this an important question?
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