3 ecological and evolutionary principles notes for marine biology: function, biodiversity, ecology...
TRANSCRIPT
3 Ecological and Evolutionary Principles
Notes for Marine Biology: Function, Biodiversity,
Ecologyby Jeffrey S. Levinton
©Jeffrey S. Levinton 2001
The Ecological Hierarchy
• Biosphere
• Ecosystem
• Community
• Population
• Individual
Ecological Processes
• Competition
• Predation
• Disturbance
• Parasitism
• Larval Dispersal
• Facilitation
Interactions Between Individuals
• +- Territoriality
• +- Predation
• + - Parasitism
• ++ Mutualism
• + 0 Commensalism
PREDATION TYPES:
Stationary:e.g., anemones
Mobile: (a) sit and wait and attack e.g., (b) pursuite.g., Shark
OVEREXPLOITATION - prey population collapse, occasional predator-prey cycles
PREY ESCAPE(a) rapid recovery rate(b) defenses(c) predators limited by other factors (e.g., octopus by den sites)(d) refuges (space, time)
Effects of Predation
Predation Example: Stationary Predator Anthopleura xanthogrammica, anemone living in tide pools of Pacific coast. Feeds on larger invertebrates that fall into its tentacles, such as mussels.
Crypsis: A marine flatfish with chromatophores that allows it to match its sedimentary background (fish outlined with arrows)
Inducible defenses
A bryozoan makes spines when placed in contact with a predatory nudibranch.
A hydrozoan, Hydractinia, produces defense stolons armed with nematocysts when in contact with another colony.
Inducible Defense: The conical (right) and bent (left) forms of the acorn barnacle Chthamalus anisopoma. The animal develops the bent form if predatory snails are present.
Inducible Defense 2: Often has a cost. Barnacle with bent form does not feed as well. Therefore, it is a good strategy to make the defense optional.
Escape behavior: The bivalve Lima hians can swim from predators by rapidly clapping its valves and expelling water in jets through the hinge. It also has mantle tentacles that secrete a sticky distasteful material that discourages predators.
Optimal Predator Models
• Diet breadth - food scarce --> increase breadth
Optimal Predator Models 2
Time spent in a patch - greater the distance between patches --> spend more time in a given patch
Optimal Predator Models 3
Optimal size of prey --> intermediate is usually preferred, yields the most food per unit time (larger prey good in reward but takes relatively long to eat, smaller prey fast to east but food per prey item is small)
Energy reward of a mussel as function of size
Preference of crab for different mussel sizes
Shore crab Carcinus maenas feeding upon the mussel Mytilus edulis.
Parasitism
• Parasites evolve to reduce damage to host
• Commonly involve complex life cycles with more than one host
• Parasites may invade specific tissues, such as reproductive tissue of the host
Invasion of the parasitic rhizocephalan barnacle Sacculina into the body of a crab
Complex life cycle found in a trematode parasite living in several marine animal hosts
Mutualism: Cleaner wrasse removes ectoparasites from a number of species of fish that visit localized “cleaning stations” on a coral reef. Fish (b) is a mimic species that actually attacks fish that would normally be a “client” of the cleaner wrasse.
Commensalism
Commensal crab and fish live in this burrow of Urechis caupo
Construction of a Population Model
dN/dT = f (N,M,R,I,E)
N = population sizeM = mortalityR = reproductionI = immigrationE = emigration
M is a function of physical environment, competition, predation, etc.
R function of physical environment, resources (e.g., food)
Example of Population Model
Barnacles: What parameters matter the most?
dN/dT = f (N, I, M)
I is larval settlement
M a function of larval-adult interactions, overgrowth, predation
Note R doesn't matter if planktonic larvae mainly go elsewhere
Mortality pattern expected for a species with a planktonic larva. Note higher mortality rate of larval stage.
Planktonic Post-settling stagelarvalstage
Sur
vivo
rs
Modes of Population Change
Exponential Growth
Logistic growth Random change
Metapopulation
• Definition: A group of interconnected subpopulations among which there is movement of individuals
Metapopulation 2
• Definition: A group of interconnected subpopulations among which there is movement of individuals
• Some subpopulations are sources of individuals that move to other subpopulations
Metapopulation 3
• Definition: A group of interconnected subpopulations among which there is movement of individuals
• Some subpopulations are sources of individuals that move to other subpopulations
• Other subpopulations are sinks, which means that they may receive individuals from other subpopulations, but they are not sources (example, only juveniles disperse, but the subpopulation in question does not have individuals that reproduce successfully.
Metapopulation - interconnected group of subpopulations
Spatial Distribution of Individuals
Random Uniform Aggregated
COMPETITION
LIMITING RESOURCES
(1) Renewable - e.g., copepods exploiting diatom population
(2) Non-renewable - space on a rock exploited by long-lived sessile species
Limiting Resources
Space is a limiting resource to these colonies of colonial ascidians
COMPETITIVE DISPLACEMENT - one species outcompetes another for a resource
COEXISTENCE - two species exploit different resources, some process allows two species to exploit same resource withoutdisplacement
Outcomes of Competition
Interference vs. Exploitation Competition
Interference - one species overgrows another, interspecific territoriality, agonistic interaction
Exploitation - one species eats a prey resource more efficiently than another (also called scramble competition)
Styles of Competitive Interaction:
Hierarchy of competitive dominance vs. network
Indirect Effects of Competition
Note: Effectively, B and C beat up on each other, A and B beat up on each other, interaction between A and C is very weak; Bsuffers the most, A and C are not as badly affected.
CONSEQUENCES OF COMPETITION
Extinction: usually local, habitat shift
Coexistence: "niche shift" - character displacement - evolution of shift in morphology or behavior
Variable Environment: Unstable, but can permit coexistence
EVIDENCE FOR INTERSPECIFIC COMPETITION
1. EXPERIMENTAL MANIPULATIONS - remove hypothetical competitor (e.g., barnacles)
2. LABORATORY DEMONSTRATIONS - e.g., growth experiments with one and multispecies combinations - disadvantage is lack of field conditions
3. DISPLACEMENTS IN NATURE - e.g., increase of resource exploitation in estuaries. Problem - other factors could be atwork
4. CONTIGUITY OF RESOURCE USE -e.g., "adjacent niches" - could arise by evolutionary change
EVIDENCE FOR INTERSPECIFIC COMPETITION 2
1. EXPERIMENTAL MANIPULATIONS - remove hypothetical competitor (e.g., barnacles)
2. LABORATORY DEMONSTRATIONS - e.g., growth experiments with one and multispecies combinations - disadvantage is lack of field conditions
3. DISPLACEMENTS IN NATURE - e.g., increase of resource exploitation in estuaries. Problem - other factors could be atwork
4. CONTIGUITY OF RESOURCE USE -e.g., "adjacent niches" - could arise by evolutionary change
EVIDENCE FOR INTERSPECIFIC COMPETITION 3
1. EXPERIMENTAL MANIPULATIONS - remove hypothetical competitor (e.g., barnacles)
2. LABORATORY DEMONSTRATIONS - e.g., growth experiments with one and multispecies combinations - disadvantage is lack of field conditions
3. DISPLACEMENTS IN NATURE - e.g., increase of resource exploitation in estuaries. Problem - other factors could be atwork
4. CONTIGUITY OF RESOURCE USE -e.g., "adjacent niches" - could arise by evolutionary change
EVIDENCE FOR INTERSPECIFIC COMPETITION 4
1. EXPERIMENTAL MANIPULATIONS - remove hypothetical competitor (e.g., barnacles)
2. LABORATORY DEMONSTRATIONS - e.g., growth experiments with one and multispecies combinations - disadvantage is lack of field conditions
3. DISPLACEMENTS IN NATURE - e.g., increase of resource exploitation in estuaries. Problem - other factors could be atwork
4. CONTIGUITY OF RESOURCE USE -e.g., "adjacent niches" - could arise by evolutionary change
RELATION OF PREDATION TO COMPETITION -
Predation suppresses competitive success of superior species over inferior species, especially if predator prefers competitively superior prey
DISTURBANCE
Usually refers to physical change in environment that causes mortality or affects reproduction (storm, ice scour).
SPATIAL SCALE OF DISTURBANCE
Habitat wide (storms, ice, oil spill)
Localized in patches (horeshoe crabs, logs)
EFFECT CAN BE SIMILAR TO PREDATION
Suppresses effect of competition (Intermediate disturbance-predation effect)
Intermediate Disturbance-Predation Hypothesis
Low levels of disturbance or predation: Competitive dominant species takes over
Intermediate levels: Promotes coexistence, more species present
High levels: most individuals removed, reduces total number of species
SUCCESSION
Predictable order of appearance and dominance of species, usually following a disturbance.
SOME MODES OF SUCCESSION
(1) Early species modify habitat, which facilitates colonization by later species
(2) Late species exclude colonization of early species
(3) Early species hold space until death, then are replaced by late species, which do the same
Some Interactions in Succession
Genetic Variation, Species
• Marine species have genetic variation
• Variation found in populations, also frequency of genes varies over space, within a species
• Species are identified by presence of reproductive isolation
Parent-Offspring correlation indicates genetic basis for variation in trait
Cline: A regular change in gene frequencies over a geographic space (here, latitude).
Example: latitudinal change in frequency of the A’ allele in the blenny Anoplarchus purpurescens, in Puget Sound, Washington
Sibling Species in the Sea
Closely related species that are reproductively isolated butvery similar in form, to the point that they cannot be identifiedwithout sophisticated (usually molecular) markers.
Larvae of 5 species of the polychaete sibling species complex Capitella capitata
Evolutionary Tree: established by grouping species with shared characters. Leads to a hierarchy that can be plotted as a tree.
The End