Community Ecology -Types of Species -Species Interactions

General Types of Species Examining roles of various species in ecosystems: Native species = a species that, other than as a result of an introduction, historically occurred or currently occurs in an ecosystem (Indigenous) Invasive species = an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health. (non native species, exotic, introduced etc.)

Some characteristics of Invasive Species: High rate of reproduction “pioneer species” High dispersal rates Tolerant of a wide range of conditions Generalist Impact on native ecosystems Invasive species impact 30-50% of the species currently listed as Threatened or Endangered under the U.S Federal Endangered Species Act. (Second only to habitat destruction.)

Examples of Non-natives (Invasive) Non-native herbivores, like gypsy moth, directly affect the flow of energy captured by plants from the sun.  Non-native earthworms can dramatically increase decomposition in soils. Non-native bee species (killer bees) Rats (Sandy Cay) Cane Frog (Tortola)

Keystone species ….play pivotal roles in the structure, function, and integrity of an ecosystem… affect the health and survival of other species. Their strong interactions with other species, and the fact that they process material out of proportion to their numbers makes them a Keystone Species.

Keystone Species Critical roles Include: Pollination of flowering plant species by bees, hummingbirds, bats Dispersion of seeds by fruit eating animals Predation by top carnivores to control the populations of various species Habitat modifications: bats and birds regenerate deforested area by depositing plant seeds in their droppings Loss of keystone species can lead to pop. Crashes and extinction of species that depend on it for certain services.

Indicator Species Can be described as species that serve as early warnings that a community or an ecosystem is being damaged or not stable. One example would be: Apex species (top carnivores or top predators) Are always the first to be affected by any change in their ecosystems and therefore, how their numbers indicate the health of the ecosystem

Birds as Indicator Species Birds are excellent bioindicators because they are found almost everywhere, and they respond quickly to environmental change. Migratory paths Habitat loss and fragmentation

Amphibians

The indicators for Tropical Caribbean eco-region (Marine) Species: All Sharks Blacktip shark Carcharhinus limbatus Blacktip reef shark Carcharhinus melanopterus Blue shark Prionace glauca Bull shark Carcharhinus leucas Caribbean reef shark Carcharhinus perezi Great hammerhead shark Sphyrna mokarran Carcharhinus perezi Grey reef shark Carcharhinus amblyrhynchos Lemon Shark Negaprion brevirostris Nurse shark Ginglymostoma cirratum Tiger shark Galeocerdo cuvier Whale shark – Vulnerable Rhincodon typus

Species: All Marine Turtles Most experts recognize seven species of marine turtles: the green, hawksbill, loggerhead, Kemp's ridley, olive ridley, leatherback, and flatback. All but one - the flatback - can be found in the Latin American and Caribbean region, and all are threatened by extinction.

Community structure Community~ an assemblage of populations living close enough together for potential interaction Richness (number of species) & abundance……. Species diversity Hypotheses: •Individualistic~ chance assemblage with similar abiotic requirements •Interactive~ assemblage locked into association by mandatory biotic interactions

Species Interactions: Predation Predator: feeds directly on all or part of a living organism Prey: organism fed on. Predator-prey relationship: One organism is clearly harmed. However at the population level there are benefits: improve access to food, and improve the genetic stock. Prey acquisition: herbivores vs. carnivores (pursue or ambush) Predator Avoidance: speed, highly developed senses,protective coverings

Predator Avoidance by Prey Chemical warfare camouflage camouflage Warning coloration Chemical warfare mimicry Warning coloration Deceptive looks Deceptive behavior

Predation defense Cryptic (camouflage) coloration Aposematic (warning) coloration Mimicry~ superficial resemblance to another species √ Batesian~ palatable/ harmless species mimics an unpalatable/ harmful model √ Mullerian~ 2 or more unpalatable, aposematically colored species resemble each other

Symbiotic Relationships Symbiosis is a relationship in which species live together in an intimate association. There are three types: Parasitism (special form of predation) Mutualism Commensalism

Interactions Interspecific (interactions between populations of different species within a community):

Symbiotic Species Interactions: Mutualism Reproductive mutualism: pollination Nutritional mutualism Nutritional/protection mutualism Fig. 8-12 p. 179

Symbiotic Species Interactions: Commensalism Indirect: i.e., small plants growing in shade of larger plants (redwood sorrel) Direct: i.e., epiphytes (orchids and bromeliads), remoras Fig. 8-13 p. 180

Symbiotic Species Interactions: Parasitism Parasite: organisms that feeds on another by living in or on another living organism. Parasite benefits. Host: Organism that a parasite feeds on and lives in or on. Host is harmed. (rarely killed) Endoparasites: parasites found inside the host organisms body. Ex.tapeworms,disease causing microorganisms. Ectoparasites: organisms found outside the host organisms body. Ex. Fleas, ticks, mosquitoes

Species Interactions: Competition Intraspecific competition: within a species for resources and territoriality. Interspecific competition: between different species for limited resources (niche overlap) Competing species must: Migrate to another area Shift its feeding habits or behavior through evolution and natural selection Suffer a sharp decline in population Extinction

Species Interactions: Competition Interference competition: One species influences another’s access to some resource regardless of its abundance. Ex. hummingbird Exploitation competition: Two competing species have roughly equal access but differ in how fast or efficiently they exploit it.

Competition: a closer look Competitive exclusion principle: by Gauss describes how one species eliminates another in an area through competition for limited resources.

Competition evidence Resource partitioning~ sympatric species consume slightly different foods or use other resources in slightly different ways Character displacement~ sympatric species tend to diverge in those characteristics that overlap Ex: Anolis lizard sp. perching sites in the Dominican Republic Ex: Darwin’s finch beak size on the Galapagos Islands

Resource partitioning

Resource Partitioning Resource partitioning: a method to reduce competition, dividing up the resource so that species with similar needs use them at different times, in different ways, or in different places. Fig. 8-9 p. 175; Refer to Fig. 7-13 p. 152 & Fig. 8-10 p. 175

The Niche Ecological niche~ the sum total of an organism’s use of biotic and abiotic resources in its environment; its “ecological role” √ fundamental~ the set of resources a population is theoretically capable of using under ideal conditions √ realized~ the resources a population actually uses Thus, 2 species cannot coexist in a community if their niches are identical Ex: Barnacle sp. on the coast of Scotland