Lecture Outline for your use in preparing for the second test

Lecture Outline for your use in preparing for the second test This is the revised lecture outline
(Dan Perlmutter-9/27/02)

What's their biogeography?

Island fauna are strange compared to mainland fauna

Island fauna not unique unto themselves in that they are similar from island to island

Island fauna in Indian Ocean was ravaged by Dutch sailors

Mascarenes islands were stocked w/ non-native animals

Native tortoises and Dodos were hunted out by humans and affected by introduced species

English & Dutch didn’t much like giant tortoise meat

Animals could be kept alive on boats for fresh meat over long trips

Thus the Mascarene tortoises depleted

Some of Seychelles islands were also depleted of their tortoises

Aldabra island in the Indian Ocean is the last of wild stock of Geochelone gigantean

Modern synthesis in genetics,a combination of: evolution + paleontology + modern genetics + molecular biology

Allopatric speciation is the evolutionary development of new species when populations of a single species are isolated from each other geographically over a long period of time. This type of speciation is often considered the norm. Sympatric speciation is the evolutionary development of new species when populations of a singe species inhabit the same geographical area but are isolated from each other due to changes in behavior or changes in the choice of habitats. This type of speciation is considered less common.

Leopold Von Busch 1825 felt that individuals can lead to varieties of species due to differences in their location and their segregation from .

In 1841 he publishes the idea that boundaries, such as rivers, mountains, or deserts can separate members of a population and lead to the formation of varieties that can, with continued geographical isolation become distinct species.

This is known as his Separationstheorie

He states that isolation is absolutely necessary for speciation

Migration introduces organisms onto new environments

and speciation occurs and becomes fixed due to isolation

Darwin is not so sure

Darwin saw examples of sympatric speciation

Two species of Rhea, large flightless birds, on plains of Patagonia

Darwin suggests ecological constraints have led to........

Phyletic evolution & reproductive isolation

Ernst Mayr says that species develop from groups of actually, or potentially, interbreeding populations which in time become reproductively isolated from each other.

Speciation results from mutations that change individuals, geographical or ecological isolation which amplifies this change, which leads to reproductive isolation.

Phyletic evolution - species change over time in which there is the gradual replacement of forms from one type to another

Speciation is usually considered as the physical separation of populations leading to reproductive isolation and the creation of two distinct species from a single ancestor.

Both process work to create new species, but phyletic evolution is a replacement process and speciation as such is a multiplying process.

The genetics of Mendel and the recognition of the role of mutation reinforced the concept of sympatric speciation

Isolation as a driving force in speciation and it was overlooked for awhile.

But Mayr believes what appears as sympatric speciation really just reflects an earlier or more subtle allopatric speciation.

Island communities can contain: flightless birds, a few amphibians, big reptiles and dwarf mammals (hippos & elephants)

Islands often contain few mammals and even fewer carnivorous mammals (Thylacinus cynocephalus the now extinct marsupial wolf of Tasmania, an island province off of southeastern Australia)

Species attributes are considered as a result of evolution and community characteristics (the number and kinds of animals assembled together) a result of ecology

Species attributes are of importance in determining the community of life on islands and these attributes include: an organism's ability to disperse & establish a popultion on islands.

Experimentation is unusual for evolutionary biology & island biogeography. Most of what we've examined falls under the realm of survey or descriptive science. However catastrophes may create a "natural experiment" which enables us to compare and contrast processes.

Krakatau an island that blew up in 1883 was located west of Java

6 cubic miles rocks blown into the sky

This atmospheric material cooled the earth (resulting in a sun that sometimes appeared green or even blue)

The explosion was heard as far away as Perth, Australia

36,000 died in Sumatra & Java from this eruption.

A tidal wave (tsunami )100 ft. high radiated out from the island and traveled as fast as freight train.

Everything on the island was incinerated

resettlement and recolonization of a new island or an island where life has been eradicated (Rakata post eruption - this is the former island of Krakatau)

1883 - 1 spider – got there by ballooning using silk as a travelling device

1886 - an algal mat appears on the shoreline – the island also received fern spores composite seeds

1887 – a number of small trees & grasses are present

1889 – butterflies, beetles, and a single monitor lizard are found on the island

wind – examples are fern spores, spiders

water – examples are coconuts or life on flotsam

chunks of land may be ripped off by hurricanes

they may support coconut palms 20-30 ft. tall

pumice from volcanoes forms a coating over the water

animals - examples are transport on birds (on the mud on their feet)

But flight dispersal may be limited

many birds don’t fly over open water

pigeons travel over ocean

they may migrate seasonally for seeds & fruit

they can be found on remote islands (Sao Thome –west Africa, Anjouan-north of Madagascar)

for example the Mascarene Islands have both dodos and the pigeon Hollandais,
(extinct 1835, pink pigeon)

            the pigeons are widely traveled yet rarely enough to allow for isolation & evolution.
            Their dispersal & establishment on an island is often a path to extinction (flightly birds vulnerable)
            But when birds are successful in reahing an island they.....

because their feathers, skin, dried mud on feet, feces

carry plants (spores, etc.) & animals

sexual reproduction requires mates. However the gecko lizard uses parthenogenesis an asexual form of reproduction.

Colonization can be initially rapid but reaches equilibrium
for instance

1908 Rakat had13 land bird species

1921 – there were 27 species

1934 – there were the same number of species (or maybe fewer)

In essence a balance is achieved between immigraton and extinction

They need mates to establish a population

and they need mothering to care for their vulnerable offspring

As in New Zealand where there are no non-flying mammals

But only bats (from Australia or New Caledonia)

Islands of the Galapagos, Caribbean, Indonesia have species of rats that were brought in by Pre-European mariners

Elephants – Swim from Ceylon to nearby islands, from Kenya to off-shore islands

Fossil elephantids are found in the Philippnes, on Indonesian islands and on islands in Mediterranean Sea (Malta, Crete, Sicily)

The former existence of a land bridge is the usual explanation for their distribution to these islands but....

Elephant swimming has been observed (for as long as 6 hours )

The Channel Islands off the coast of southern California have fossil remains of the elephant Mammuthus exilis, a pygmy form

A land bridge has been offered as an explanation for these fossils– but there are no other fossil mammals on these islands and........

the Bathymetry (ocean bottom) is deep between islands and California

Hippos & deer share the elephant distribution on islands in the Mediterranean, Indonesian, and Japan

Extinct channel island elephant was 6 foot tall (mainland extinct form was 14 feet), tiny deer are found on the Mediterranean islands, Indonesian island hippos are pig-sized.

Snakes may be either larger or smaller and sometimes that's due to competition between them

Thus Dwarfism vs. gigantism may occur between congenerics (different species of the same genus)

Such as in the case of rattlesnakes on the Channel islands Croatalus ruber vs C. mitchelli

Which may be an example of sympatric speciation as a result of niche separation

However Lizards are often larger on islands uch as the Channel island skinks, Jamaican anguids, etc.
Komodo dragons are an example

They are found on Komodo & surrounding islands (west Flores & others) in Indonesia

This species is known as Varanus komodoensis

and was reputed as big as 23 feet long

But Auffenberg’s studies establish the max length at 10 ft. + few inches

Why is this lizard so large?

It's known that many predators match their prey size and weight

Well Komodos eat deer, humans, boar, and water bufflo which is ten times its size

Komodo's are lurk and lurch predator

They feed on herds of Rusa deer

Their current prey are recent island arrivals

But their former prey may be the now extinct miniature elephants.

Become fast & furious when food’s available

Jared Diamond suggested that the komodos ate prehistoric elephants (Stegodon sompoensis)

Fossil Stegodons are found on Flores Island (near Komodo)

Komodos have been on both islands (Flores and Komodo) for a long time

There were no other prey (till humans, deer, buffalo came along)

These fossil elephants were small (5 ft tall, like buffalo)

6 meters (18 feet) long

2000 kg (nearly 4400 lbs)

Some mammals smaller (elephants, rhinoceros, hippos, deer, rabbits, foxes, pigs) but rodents larger – Foster’s rule big mammals become smaller and small mammals become bigger)

Reptiles are bigger (tortoises, lizards – monitors & iquanas & geckos & skinks) but snakes are smaller

Birds are both bigger & smaller

Insects are both bigger (earwigs, walking sticks [cigar-sized], cockroach) & smaller (moths on Galapagos

Rodents grow bigger because there's less competition for resources due to population self-control.(inherent population growth control such as cannibalism occurs with crowding) & predation, larger rodents survive better thru leaner food times,

Overall for rodents the biggest of the litter has a better success at survival & reproduction (Natural Selection)

Artiodactyls (cloven hoofed-even toed ) deer, hippos, pigs don’t limit their populations when crowded as do rodents.

Thus their resources can become limiting

So a smmaller size at reproduction is a benefit under these conditions.

The key to evolution on islands is that these restricted populations have a smaller gene pool with a restricted gene flow to other populations

1.Evolution (as such) – it takes place

2.Common descent – groups of organisms with common ancestor

3.Multiplication of species – species multiply by splitting into 2 spp. at various times.

4.Gradualism – evolution an accumulation of small changes

5.Natural selection – many individuals born, population w/ genetic variability, few individuals survive to reproduce, beneficial traits spread, population genetics changes

Natural selection occurs because.....

Populations grow unchecked exponentially

But there are limits to growth such as....

Thus many offspring die

And because of genetic variability in population

Some few live to reproduce and

Their genes predominate in the future

Darwin didn't know the mechanism for inheritance

He saw inheritance as a blending of traits.

Gregor Mendel discovered the particulate nature of heredity

He was a monk who studied the characteristics of peas

Peas -wrinkled, smooth; flowers- colors

He saw some blending but also saw that distinct traits were expressed

And in fact there was a predictable appearance of these traits

Thus he surmise that these traits are particulate in nature

He published his findings in 1868 Transactionf of the Brunn Natural History Society but that news didn't travel far.

Hugo DeVries rediscovered Mendel's work in early 20th century

And this information strengthen’s Darwin’s concepts.

The Theory of Island Biogeography (1967) – Geographical Ecology: Patterns in the Distribution of Species (1972)

“To do science is to search for repeated pattersn, not simply to accumulate facts, and to do the science of geographical ecology is to search for patterns of platn and animal life that can be put on a map.”

MacArthur mathematizes ecologyMacArthur paved the way for Mathematical modelling in ecology

A reality based is an empirical model.

Reality tested models should have predictive value

reassessment occurs when the predictions don't match reality.

A model for Gigantism on islands is based on the supposition that there's little or no predation and a lack of competition
An example....

Rattites are flightless birds that inherit a mammal’s niches on islands. Mammals usually have a harder time dispersing and establishing themselves on islands.

Moas and elephant birds are two examples

These birds have a small keel (bone surface used for the attachment of flight muscles) and weak flight muscles

The elephant birds, Aepyornis, are a relict animal group meaning they were once widespread but are now limited in their distribution (These rattites were once widespread throughout the prehistoric continent of Gondwanaland)

Aepyornis was once present but went extinct in Africa and lasted until relatively recently (within historical times) as a relict population endemic to the island of Madagascar where it faced no predators (except eventually, humans)

Lamarckism is based on the ideas of Jean Baptiste Lamarck, a French naturalist who believed that an organism could acquire a characteristic within its lifetime that could then be passed onto its offspring. These characteristics weren't the result of mutation, which if it affected the reproductive cells of an organism, could indeed by tranferred to progreny. These characteristics were truly acquired, picked up by an animal in a non-genetic manner.

Darwin also considered acquired characteristics as possibly being inheritable.

He surmised that the better fliers amongst the beetle may be more lidely to be blown off the island and that......

ground hugging females among the population lead to a atrophy (atrophy = loss with disuse much like the loss of leg muscle if you were paralyzed from the waist down) of wings within an individual's lifetiime and that those characteristics of smaller wings may be transferred to progeny.

Phillip Darlington, a wartime entomologist, studied Carabidae (beetles) and noted various forms: geophiles (dirt loving), hyrdophiles (water loving) and arboreal (tree-dwelling) types. And he noted that shrunken winged flightless forms were to be found inland at high elevations or on islands. He postulated an economy of energy use in that this organism could obtain only so much energy in its lifetime and the allocation of the energy would be for certain activities like feeding, reproduction, etc. Those individuals that allocated less energy to flight might benefit in areas where flight is more risky, like on tops of mountains or on islands. So thee is a selection against less useful traits

Darlington also noted the relation of species riches to available habitat. He said that the “limitation in area of limits both number & kind of species in isolated faunas”

Tameness, lack of fear of humans, is observed with initial contacts with island organisms such as.....

Galapagos finches, tortoises, herons, warblers, and the Falkland fox.

Are these animals just dumb?

No they are ecological naive .....

Evolution prepared them for life in a little island world that is smpler and more innocent than the big world

An example is the Galapagos iquanas

They dive for food, seaweed and this is unusual for a reptile

Darwin played a toss and return experiment with these iguana

There are no predators on land

But there are sharks offshore

Amblyrhynchus cristatus - the marine iquana

Appearance - Pugish, Dark-bodied w/ some bright color patches in males

Mating - Males are territorial, dorsal spikes are raised, the body swells, the mouth gapes opens and displays red

Males head butt– for hours to establish dominance

Archipelago speciation occurs with Amblyrhynchus cristatus in the Galapagos

At first one island is colonized

Then individuals find their way to nearby islands

Each island is close but not too close so....

populations diverge genetically

A. Cristatus variety bassi- a big bodied form found on Santa Cruz in the island in the middle of the Galapagos

A. Cristatus variety venustissiumus- is brightly colored and found on Espanola in the south

A. Cristatus variety nanus- is small & dark and found on Genovesa in the northeast

Adaptive radiation is the filling of niches, as a result of intraspecies competition & sympatric speciation
An example

Mockingbirds on Galapagos result from allopatric speciation geographical isolation of populations but the finches on Galapagos show adaptive radiation.

The Galapagos turtles have differently shaped shells in different island locations

A Saddle-shaped shell is good for reaching up to lower leaves and useful in an arid environment with little grass

A Dome-shaped shell is good for protection while grass grazing in a wet environment

Initial colonizers show up on islands as a random sample of the homeland population’s genetic variety

And if they are few then their reduced genetic variety affect the subsequent population.

Genetic drift in a small population is seen when rare alleles are likely to be lost by chance, through the a death of few animals with those genes.

Main points
These are regions of abundant moisture and little temperature variation
    Temperate rain forests – on the west coast of continents as found in the North West U.S.
    Subtropical rain forests – east coast of continents as found in the southeastern U.S.
    Tropical rain forests – hot, moist year round found at lower elevations around equator
        Largest tropical rain forests inSouth America covering most of Amazon
        North American tropical rain forests found in southern Mexico, Caribbean, Central America and Puerto
        Rico

Characteristics
    Equatorial rain forest with an annual temperature range of 75-90 degree F.
    They have 12 hours of sunlight throughout the year
    Located from Tropics of Cancer (N) to Caricorn (S)
    They receive 60+ inches of rain per year and all year round though some seasons are wetter than others
    The rain forest can make its own climate from evapotranspiration which results in high humidity,
    Biodiversity = total plants, animals, fungi, and microbes within an area
        Tropical rain forests have 50-90% of world's species in less than 7% of land area.
        Biodiversity is high in tropical rain forests with predation and competition as the main limiting factors
        Flowers and fruits are produced year round and plant-animal associations are strong

Forest structure
    Tall, evergreen broad leaf plants and trees, with buttressing shallow root systems
        Nutrients for plants are concentrated at the soil surface
        The shallow root system, with the help of fungi, reabsorbs and effectively recycles nutrients
    Three layers of forest provide vertical niches and most life is found at the higher levels
        The emergent layer is the upper layer where trees are 150-200 feet tall and have umbrella-shaped crowns
            Emergent trees, one or two per acre experience greater temperature extremes and lower humidity than
            lower layers
        The middle layer or main canopy, has trees 65-130 feet tall with flat or umbrella crowns
            They form a dense canopy, intercepting most of the light and rain
            The middle layer shades the forest floor
            This is the layer that contains most life
        The understory layer, with trees 15 –50 feet high with elongated (flame-shaped) crowns
            These trees have larger leaves to catch lower amount of light
        Epiphytes are plants that grow on other plants, namely trees.
            Epiphytes are not harmful to host trees.
            Epiphytes need no soil as they receive minerals from organic decay.
            Epiphytes catch the water running down tree stems, or from rain
                They collect this water in leaf “baskets”
        The ground level is an open area with little food for mammals
            The ground level is a detrital system complete with termites, millipedes, bacteria & fungi all of which
            are decomposers that recycle nutrients by quickly breaking down the layer of dead leaves.
            These nutrients are shunted to the tree roots

Threats
        Local population demands for land and global demands for resources are the main threats.
        Two hundred years ago rain forests covered 20% of the world's land area,
            now they occupy less than 7%.
        100,000 square miles are lost per year.
        Many species are lost or endangered and many of these may be useful for humankind.

Know the components of this diagram of a linear food chain. Be able to define them as well as name them. I= total energy input; L_a = light absorbed by plant cover; P_g= gross primary production; A= total assimilation; P_n = net primary proudction; P = secondary (consumer) production; NU = energy not used; NA = energy not assimilated by consumers (egested); R= respiration. Bottom line shows the energy level at several levels starting with an input rate of 3000 kcal of energy per square meter per day.

The laws of thermodynamics
1st - Energy can neither be created or destroyed but simply transformed
2nd - Every transformation of energy from one form to another results in some amount being changed into a less concentrated, and thus less useful, form such as heat.

Ecological efficiency
As energy passes up the "food chain", or trophic levels, of a system only 10% is transferred in a useful form from one level to the next

Trophic Levels - the primary producers (P) are the plants, the primary consumers (C₁) eat the primary producers (P). These are herbivores. The secondary consumers (C₂) eat the herbivores (C₁). the tertiary consumers (C3) eat the secondary consumers (C₂) and are usually the top predators of the system.

A food web is the interlocking trophic structure of specific types of organisms within the system. An organism may feed at different levels and this makes a food web more complex than a food chain.

The carrying capacity of a system is the greatest number of a particular kind of organism that it can sustain.

Amblyrhynchus cristatus - the marine iquana