Evolution, Biodiversity, and Community Processes La Cañada High School Dr. E

Biodiversity

How do we get Biodiversity?

Biodiversity Biodiversity increases with speciation decreases with extinction Give-and-take between speciation and extinction  changes in biodiversity Extinction creates evolutionary opportunities for adaptive radiation of surviving species

Interpretations of Speciation Two theories: 1. Gradualist Model (Neo-Darwinian): Slow changes in species overtime 2. Punctuated Equilibrium: Evolution occurs in spurts of relatively rapid change

Adaptive Radiation Emergence of numerous species from a common ancestor introduced to new and diverse environments Example: Hawaiian Honeycreepers

Convergent Evolution Species from different evolutionary branches may come to resemble one another if they live in very similar environments Example: 1. Ostrich (Africa) and Emu (Australia). 2. Sidewinder (Mojave Desert) and Horned Viper (Middle East Desert)

Coevolution Evolutionary change Example: Wolf and Moose One species acts as a selective force on a second species Inducing adaptations that act as selective force on the first species Example: Wolf and Moose Acacia ants and Acacia trees Yucca Plants and Yucca moths Lichen

Extinction Extinction of a species occurs when it ceases to exist; may follow environmental change - if the species does not evolve Evolution and extinction are affected by: large scale movements of continents gradual climate changes due to continental drift or orbit changes rapid climate changes due to catastrophic events

Extinction Background extinction - species disappear at a low rate as local conditions change Mass extinction - catastrophic, wide-spread events --> abrupt increase in extinction rate Five mass extinctions in past 500 million years Adaptive radiation - new species evolve during recovery period following mass extinction

Date of the Extinction Event Marine vertebrates and invertebrates Mass Extinctions http://www.geog.ouc.bc.ca/physgeog/contents/9h.html Date of the Extinction Event Percent Species Lost Species Affected 65 mya (million years ago) 85 Dinosaurs, plants (except ferns and seed bearing plants), marine vertebrates and invertebrates. Most mammals, birds, turtles, crocodiles, lizards, snakes, and amphibians were unaffected. 213 mya 44 Marine vertebrates and invertebrates 248 mya 75-95 380 mya 70 Marine invertebrates 450 mya 50

Equilibrium Theory of Biodiversity Diversity is a balance of factors that increase diversity and factors that decrease diversity Production of new species (speciation), and influx can increase diversity Competitive exclusion, efficient predators, catastrophic events (extinction) can decrease diversity Physical conditions variety of resources Predators environmental variability

Comparison of Two Communities Richness (number of species) Relative abundance How do we describe these differences?

Biogeographical Changes Richness declines from equator to pole Due to: Evolutionary history Climate Generally tropical communities are older than temperate than polar communities Organisms have a richer evolutionary history in an area where they are adapted to the climate. Energy input (solar) and water availability factor into this phenomenon. Fig 53.23 Bird species numbers

Geographic (Sample) Size Species-area curve The larger the geographic area, the greater the number of species Note that both scales are logarithmic Fig. 23.25 North American Birds

Species Richness on Islands Depends on: Rate of immigration to island Rate of extinction on island These in turn depend on: Island size Distance from mainland Because of their size and isolation, islands provide great opportunities for studying some of the biogeographic factors that affect the species diversity of communities. Imagine a newly formed island some distance from the mainland. Robert MacArthur and E. O. Wilson developed a hypothesis of island biogeography to identify the determinants of species diversity on an island.

How do species move? Humans (accidental and intended) Animals (sticky seeds and scat) Wind and ocean currents (+ or -) Land bridges Stepping stone islands affected by climactic changes (glaciation) ocean levels short-term weather patterns Aerial dispersal cause by wind, birds, flying insects. Dependent on long-term viableility of seeds, spores, etc. Decreasing ocean levels may allow flow of organisms between land masses normally isolated. This allows for genetic mixing. Coconuts are a good example of well adapted marine dispersed organism. Long-lasting climactic changes such as glaciation may allow for the expansion and subsequent reduction of range, but during that expansion, gene-flow will occur.

What allowed colonization? Niche opening No competition Endemics not utilizing resources Accessibility to colonists Colonization of young islands is especially rapid compared to older islands and especially the mainland 4 - Of course, if there is no access to colonists, there will be no colonization.

Theory of Island Biogeography Immigration rate decreases as island diversity increases Extinction increases as island diversity increases Species equilibrium on islands is a balance of immigration and local extinction

Theory of Island Biogeography Smaller islands have lower total populations Probability of extinction increases with lower population Smaller islands have lower species diversity

Theory of Island Biogeography Islands further from mainland have lower immigration rates More distant islands have lower species diversity

Community Relationships

the species’ occupation and its Niche is the species’ occupation and its Habitat location of species (its address)

Niche A species’ functional role in its ecosystem; includes anything affecting species survival and reproduction Range of tolerance for various physical and chemical conditions Types of resources used Interactions with living and nonliving components of ecosystems Role played in flow of energy and matter cycling

Niche Fundamental niche: set of conditions under which a species might exist in the absence of interactions with other species Realized niche: more restricted set of conditions under which the species actually exists due to interactions with other species

Types of Species Generalist Specialist large niches tolerate wide range of environmental variations do better during changing environmental conditions Specialist narrow niches more likely to become endangered do better under consistent environmental conditions

r and k strategists Depending upon the characteristics of the organism, organisms will follow a biotic potential or carrying capacity type reproductive strategy The r-strategists High biotic potential – reproduce very fast Are adapted to live in a variable climate Produce many small, quickly maturing offspring = early reproductive maturity “Opportunistic” organisms The K-strategists Adaptations allow them to maintain population values around the carrying capacity They live long lives Reproduce late Produce few, large, offspring

Types of Species Native species normally live and thrive in a particular ecosystem Nonnative species are introduced - can be called exotic or alien Indicator species serve as early warnings of danger to ecosystem- birds & amphibians Keystone species are considered of most importance in maintaining their ecosystem

Nonnative Species Nonnative plant species are invading the nation's parks at an alarming rate, displacing native vegetation and threatening the wildlife that depend on them At some, such as Sleeping Bear Dunes National Lakeshore in Michigan, as much as 23 percent of the ground is covered with alien species, and the rate of expansion is increasing dramatically.

Indicator Species a species whose status provides information on the overall condition of the ecosystem and of other species in that ecosystem reflect the quality and changes in environmental conditions as well as aspects of community composition

Keystone Species A keystone is the stone at the top of an arch that supports the other stones and keeps the whole arch from falling a species on which the persistence of a large number of other species in the ecosystem depends. If a keystone species is removed from a system the species it supported will also disappear other dependent species will also disappear Examples top carnivores that keep prey in check large herbivores that shape the habitat in which other species live important plants that support particular insect species that are prey for birds bats that disperse the seeds of plants

Species Interaction

Competition Any interaction between two or more species for a resource that causes a decrease in the population growth or distribution of one of the species Resource competition

Competition

Resource Competition

Competition Any interaction between two or more species for a resource that causes a decrease in the population growth or distribution of one of the species Resource competition Preemptive competition

Competition Any interaction between two or more species for a resource that causes a decrease in the population growth or distribution of one of the species Resource competition Preemptive competition Competitive exclusion

Competitive Exclusion

Competition Any interaction between two or more species for a resource that causes a decrease in the population growth or distribution of one of the species Resource competition Preemptive competition Competition exploitation Interference competition

Competition

PREDATION

Predator Adaptations Prey detection and recognition sensory adaptations distinguish prey from non-prey

Predator Adaptations Prey detection and recognition Prey capture sensory adaptations distinguish prey from non-prey Prey capture passive vs. active individuals vs. cooperative

Predator Adaptations Prey detection and recognition Prey capture sensory adaptations distinguish prey from non-prey Prey capture passive vs. active individuals vs. cooperative Eating prey teeth, claws etc.

Prey Adaptations Avoid detection camouflage, mimics, diurnal/nocturnal

Prey Adaptations Avoid detection Avoid capture camouflage, mimics, diurnal/nocturnal Avoid capture flee resist escape

Prey Adaptations Avoid detection Avoid capture camouflage, mimics, diurnal/nocturnal Avoid capture flee resist escape Disrupt handling (prevent being eaten) struggle? protection, toxins

Herbivory Herbivore needs to find most nutritious circumvent plant defenses

Herbivory Herbivore needs to find most nutritious circumvent plant defenses Herbivory strong selective pressure on plants structural adaptations for defense chemical adaptations for defense

Herbivory

Herbivory

Herbivory

Symbiosis: Mutualists, Commensalists and Parasites

Symbiosis and symbiotic relationship are two commonly misused terms Translation of symbiosis from the Greek literally means “living together” Both positive and negative interactions

Mutualism DEFINITION: An interaction between two individuals of different species that benefits both partners in this interaction

Raise the carrying capacity Mutualism Increase birth rates Decrease death rates Increase equilibrium population densities, Raise the carrying capacity

Pollination Animals visit flowers to collect nectar and incidentally carry pollen from one flower to another Animals get food and the plant get a pollination service

Yucca and Yucca Moth Yucca’s only pollinator is the yucca moth. Hence entirely dependent on it for dispersal. Yucca moth caterpillar’s only food is yucca seeds. Yucca moth lives in yucca and receives shelter from plant.

Lichen (Fungi-Algae) Symbiotic relationship of algae and fungae…results in very different growth formas with and without symbiont. What are the benefits to the fungus?

Nitrogen Fixation Darkest areas are nuclei, the mid-tone areas are millions of bacteria Gram -, ciliate

Obligatory Mutualism Obligatory: An organism can't live without the mutualism--either cannot survive or cannot reproduce. the common pollinator systems like bees and flowering plants protozoans in the guts of termites the alga in the lichen partnership

Facultative Mutualism Facultative: This is "take it or leave it" for one or both partners While the organism benefits when the mutualism is present, it can still survive and reproduce without it ant mutualisms, such as ants protecting plants from predation ants tending aphids

Commensalists Benefit from the host at almost no cost to the host Eyelash mite and humans Us and starlings or house sparrows Sharks and remora

Parasites and Parasitoids Parasites: draw resources from host without killing the host (at least in the short term). Parasitoids: draw resources from the host and kill them swiftly (though not necessarily consuming them).

Parasitic wasps Important parasites of larvae. In terms of biological control, how would this differ from predation? ovipositor

Ecological Processes

Ecological Succession Primary and Secondary Succession gradual & fairly predictable change in species composition with time some species colonize & become more abundant; other species decline or even disappear.

Ecological Succession Gradual changing environment in favor of new / different species / communities

Primary Succession Gradual establishment of biotic communities in an area where no life existed before No preexisting seed bank newly formed islands (i.e. volcanic origin) retreat of a glacier

Primary Succession Glacier Retreat

Secondary Succession Gradual reestablishment of biotic communities in an area where one was previously present. Preexisting seed bank treefall gaps "old field succession" forest fire

Disturbance Event that disrupts an ecosystem or community; Natural disturbance tree falls, fires, hurricanes, tornadoes, droughts, & floods Human–caused disturbance deforestation, erosion, overgrazing, plowing, pollution,mining Disturbance can initiate primary and/or secondary succession

Ecological Stability Carrying Capacity – maximum number of individuals the environment can support

Ecological Stability - Stress Drop in Primary Productivity Increased Nutrient Losses Decline or extinction of indicator species Increased populations of insect pests or disease organisms Decline in Species diversity Presence of Contaminants

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