Ecology

Natural selection within a species

1.Favors those individuals who can produce the most offspring - number of offspring per mating • at 2 per mating (5 generations): 2→4 →8 →16 →32 • at 3 per mating (5 generations): 3 →9 →27 →81 →243 - number of times individual can reproduce over its lifetime • 1 time @ 2 young = 2 • 10 times @ 2 young = 20 2) Favors those who survive the given environmental conditions (fitness) - offset by parental investment • lower number of young permits increased parental care • increasing number of young decreases amount of parental care possible The number of young produced by a species is inversely related to the amount of parental care required. This is why mammals and birds produce few young per mating that other organisms. There is a significant investment in providing shelter and food for their young, which decreases the number than can be successfully produced.

Evolution by speciation

Basic requirement: reproductive isolation between populations • Reproductive isolation - prezygotic: prevention of mating - postzygotic: production of nonviable offspring Prezygotic - environmental - behavioral - mechanical - physiological Postzygotic - offspring weak, do not survive to maturity - developmental problems • sterility • abnormalgonads - segregational - F2 breakdown The most important requirement for speciation is reproductive isolation - either the organisms can no longer mate at all or if they do, they no longer produce viable offspring.

Descriptive ecology

Descriptive ecology: -We set mist nets and camera traps to see what kinds of animals inhabited each community. -We would never have seen any of these animals without the mist nets and camera traps!

Scientific method

-Natural history observations (can be broad/ ex: flow of river or fish in the river) -question -hypothesis (from question develop 1 or more)(something diff about the soil chemistry) -predictions -experimental design (project) -data collection and analysis (from experimental design) -comparing predictions and data (on soil chemistry, go back to predictions to compare differences of nutrients) unsuccessful: -prediction -hypothesis rejection successful predictions: -hypothesis confirmed -question answered -additional testing

Overriding factors

-avoidance or escape mechanisms -acclimation How can a species live in a place where the environmental conditions say it should not be able to? It either has a mechanism to escape unfavorable conditions (e.g., migrating south for the winter, hibernating or estivating) or the species can acclimate to the condition. Acclimation is the ability to adjust to a new environment. Think about a temperature outdoors of 50F. In the summer when our average temperature is 80 or 90F, 50F feels very cold. But in the winter, when our average temperature is in the 40sF, 50F would feel warm. That's acclimation. It's important to not the difference between adaptation and acclimation, in terms of ecology. Adaptation in ecology is a genetic natural selection response. Acclimation is a response by an individual, no genetics involved.

Levels of integration studies in biology

-biosphere -landscapes -ecosystems -communities -population -indivisible organisms(ecology starts) -organ systems -organs -tissues -cells -sub cellular organelles -molecules (start/smaller) decreasing scientific understanding -We understand more about molecules and cells and how they work than we understand communities and ecosystems and the way they work. As you follow the arrow up, the levels of integration get more and more complex - with more and more variables controlling them - therefore, our scientific understanding of them decreases. The asterisks denote the levels of integration that are studied in the discipline of ecology.

Directional selection for beak size in the Galapagos ground finch, geospiza forza

Directional selection. This species is one of Darwin's famous finches on the Galapagos Islands. The small species is adapted to eating seeds of a number of species of grasses and there is genetic variability in the bill size. Bill size in birds is classically related to the size and types of seeds they consume. About 40 years ago, a severe El Nino event occurred and caused a multiple-year drought in the Galapagos, which caused the local extinction of many species of grasses. Researches saw extremely fast natural selection for bill size in this species as a result. Those individuals with smaller bills didn't fare so well when grasses with tiny seeds disappeared. But the individuals with larger bills could feed on a diversity of seeds. So on this slide, you can see the survival of birds from this El Nino event was related to the bill size and drove the average bill size of these finches larger in the years following the drought.

Disruptive selection in the three-spine stickleback in British Columbia, (a) smaller, limnetic form, (b) larger, benthic form

Disruptive selection. We don't see many examples of this, maybe because they aren't very noticeable. This is the 3-spine stickleback; both (a) and (b) are individuals of the same species, but they look very different and have different preferred habitats. The (a) form lives in the water column and the (b) form lives on the bottom. At some time in the past these were interbreeding, but now they are not. The (a) form interbreeds with other (a) forms and the (b) form interbreeds only with other (b) forms. They may be headed to speciation in the future, but for now they are still capable of interbreeding, so they are still the same species.

Production of young blue tits in relation to clutch size, Wytham Woods, Oxford, EnGland

For this species, survival of young birds in manipulated nests is poor; the birds incubate only a specific number of eggs. For some species, the number of young produced is genetic. Good or bad environmental conditions don't matter, the birds will always produce the same number of young. This was tested in nests of blue tits in England which produce clutches of 11 eggs. When the researchers either removed or added eggs to the nests, the survival rates decreased. These birds wanted 11 eggs, no more, no less.

Number of house wren chicks fledged from manipulated broods - disagreement with Lack's hypothesis

For this species, survival of young is not controlled by the clutch size. On the other end of the scale are house wrens. Their clutch sizes vary from year to year based on how plentiful food is. When researchers manipulated house wren nests, there was no change in survival percentage. If there are a lot of insects, house wrens will produce big clutches. If there aren't many insects around, food for the young is scarce and the wrens produce smaller clutches.

Distribution and abundance of the horned lark in North America, 1994-2003

Let's look at some real distribution and abundance data. This map is the distribution and abundance of the horned lark in North America (not in Houston) across a ten year period Colors represent number of birds that were spotted. -Where is it most abundant (dark red)? East and west of Rocky Mountain!! High concentration -What is the limit of its distribution (line between blue and pale green)? By observational data! -purple line is the BBS limit (breading bird surface limit) didn't look at breeding birds. So we see there are no horned larks in most of Canada or in the SE U.S. and into the lower Appalachian Mountains. Why? Hint: horned larks are grassland birds. -they like the dessert (west Texas)

Relationship between distribution and abundance

No individuals average density very low moderate density -high density Krebs' definition of ecology is "the study of the interactions that determine the distribution and abundance of organisms". So let's start with how distribution and abundance are related. This slide shows how most organism populations occur. In places where there are lots of resources (e.g., food, space), the density of the population will be high. Outside that main area, resources may be decreased and the population density is lower. Outside that area, population densities get lower and lower, until there are no individuals at all. The edge of the distribution of this populations is the line between the light orange (average density very low) and yellow (no individuals) areas on the slide. To say it another way, in order to have a distribution, the density must be greater than zero.

Cecropia trees and Azteca ants

Obviously, the Cecropia tree is providing habitat for the Azteca ants. But they need food and in many ant- plant relationships, the ants have to leave the plant to forage for food and bring it back to the colony. Not so for Cecropia. Cecropia keeps its ants in/on the tree by providing everything the ants need. Bead bodies are secretions from the stomata under the Cecropia leaves that are high in glucose. Mullerian bodies are secreted in the green branches and supply glycogen (animal starch!) for the ants. Both bead bodies and Mullerian bodies are shaped like ant eggs, so the ants think they're returning wayward eggs to the inside of the tree. Ant-plant coevolutionary relationships are generally mutualistic, meaning the relationship benefits both species. The ants get housing (and food, in the case of Cecropia); the plants get protection as the ants dispatch various herbivores that might attack the plants. However, not all coevolutionary relationships are mutualistic - remember the rabbit and lynx example a few slides ago?

Tropical ant-plant relationships • Primary domatia malastomataceae legume: inga

On the left are melastome domatia that have been cut to show the ants and eggs inside. On the right is another ant-plant, the legume Inga, which support domatia in the large veins of the compound leaves. Notice the nodes at the intersection of the leaflets, this is how the ants go in and out of the domatia.

Tropical ant-plant relationships

Primary domatia tropical plant family melastomataceae The tropical plant family Melastomataceae has many species that are "ant-plants". Ant-plants have morphologies that can house ant symbionts (primary domatia). These are part of the species' phenotypes and are present whether or not inhabited by ants (i.e., not "built" by the ants. In the photo on the left, the domatia are in the petiole of the plant's leaves; in the photo on the right, the domatia are in the base of the leaf. When colonized by specific species of ants, the domatia provide housing for the colony throughout the plant. Why are ant-plants common in the tropics? There are lots of insect herbivore predators and this is a mechanism by plants to use nasty ants to protect their leaves from herbivory. The traits involved: creation of the domatia structure by the plants and ant behavior to occupy the domatia.

Hypothetical transplant experimenT

The first experiment conducted when studying the distribution of a species is a transplant experiment. You know where the species occurs and you know where it doesn't occur, so you transplant some individuals into the area where the species does not occur. [Note: we don't do this with species we know are invasive!] If the transplant does not survive, then we conclude that there is something about that environment that the species cannot tolerate. However, if the transplant survives, then why doesn't it occupy that area?

Cecropia trees and Azteca ants

The five species of Cecropia trees in the Amazon are ant-plants on steroids. These are relatively short-lived trees (about 30 years) that colonize "new" land (formed by river meanders) or disturbed land (abandoned farms) along the Amazon River. When a tree is just a seedling, it can be colonized by an Azteca ant queen, who produces all of the ants for the colony that grows as the tree does. It's an effective strategy - notice that these leaves do not appear to be grazed on!

Ecology

The study of house/home (earth) its a broad field. It's been a challenge to narrow definition down to study.

Three hypothesis for speciation

These models are described on the next slide. The usual case for speciation is allopatric (physical separation); however there are examples of parapatric speciation as well. Sympatric speciation is largely theoretical.

Ecology is a very broad science and biologists over the have tried to put a scientific definition on it. Some of those definitions are shown in this slide, although all of them are very general. We'll come back to Eugene Odum's take on the science of ecology later in the course.

This is the definition of ecology that we'll use for our course - the one coined by the author of the text our course is based on. Charles Krebs is an emeritus professor of ecology at the University of British Columbia, from where he retired in 2001. He studied rodent populations, including lemmings, and snowshoe hares, and as you'll see from examples used throughout the course, also has a fondness for birds and Australia. Krebs defined ecology as the scientific study of the interactions that determine the distribution and abundance of organisms. And that's what we'll be focusing on: distributions, abundances and interactions.

Approaches to studying ecology Functional ecology

Using the functional ecology approach, we took soil samples and analyzed the soil composition, nutrients, moisture, etc. And we studied chlorophyll levels in each community as a measure of the community productivity. Each little project gave us one kind of answer, but needed to compile all of the data together to get a big-picture answer for the differences in these three communities.

Cecropia trees and Azteca ants

When the tree is bumped or attacked by anything, then ants swarm out of the interior of the trunk and onto whatever is threatening the tree on the outside. See all of the ants in the photo on the right? This was after we shook the tree a little. Azteca ants are about 100 times meaner than our fire ants. The traits involved: creation of the domatia structure by the plants and ant behavior to occupy the domatia.

Which factor limits this distribution?

Which environmental factor limits the distribution of Plant X? Look for the tolerance values that fall outside the environmental range for that factor.

Process of evolution

• Adaptation - natural selection acts on phenotypes to cause change in the genetic make-up of a population over time • Speciation - members of a population become reproductively isolated from each other, leading in time to separate species The second process of ecological evolution involves speciation, where members of a population become so isolated from each other that they go on different natural selection paths that lead to becoming totally separate species.

Processes of evolution

• Adaptation (population characteristic) - natural selection or environment acts on phenotypes to cause change in the genetic/ genotype make-up of a population over time (adapting requires genetic variability, humans dont have that) • Speciation - members of a population become reproductively isolated from each other, leading in time to separate species Adaptation and speciation are both evolutionary processes in ecology. We'll start with adaptation and come back to speciation later.

History of Ecology

• Advances after the 17th century - Buffon (c. 1756) • Georges-Louis Leclerc, Comte de Buffon • author of Natural History • humans, plants and animals all regulated by the same processes A century later, a French naturalist / mathematician / cosmologist, Georges-Louis Leclerc (the count of Buffon), wrote and illustrated a treatise entitled Natural History, that equated the processes controlling populations of humans, animals and plants. Quite heretical for his time because at the time plants and animals might be equated, but his work opened the door up for Darwin and other scientists of the 19th century.

History fo ecology

• Advances after the 17th century - Adolphe Quetelet (c. 1835) • potential ability of a population to grow geometrically is balanced by an inherent resistance to growth (slow down growth doesn't matter if they had to much food or not) - Pierre-François Verhulst (c. 1838) (most important) • derived equation describing growth of a population over time: logistic • his work was overlooked for 100 year (published but no one listened until 1900s) We will get into Verhulst's immense contribution to the science of population ecology in the second section of the course. His logistic equation explains how population growth is limited by the available resources and forms the foundation for all of our competition and predator-prey models.

Levels of integration in biology

• Ecosystem - group of interacting communities, linked by lines of energy transfer - abiotic features - biotic features - examples • Galveston Bay • East Texas piney woods (bigger than Galveston bay) • pond • mattress (just listen to some of those commercials!) Up another level and we're at ecosystem, a group of communities linked by lines of energy transfer (e.g., food webs). Whereas in communities, populations and species we are looking at only the organisms (biotic), at the ecosystem level, we add it the nonliving (abiotic) components, such as substrate, soil type, nutrients, climate, salinity, etc. Ecosystems can be of any size. Galveston Bay is an excellent example of a local ecosystem; the communities that make up the Galveston Bay ecosystem include coastal prairie grasslands, bottomland hardwood forests, bay bottom benthos, salt marsh wetlands, and more.

Ecology and evolution

• Evolution (in ecological terms) - change in traits of a population over time - involves changes in the frequency of individual genes in a population from one generation to the next (directional selection) Evolution in ecological terms is simply the change in genetic traits of a population over time.

Distribution of light and dark forms of B. betularia in Great Britain, 1950s

Figure shows the relationship between light and dark forms at each of these locations.

Approaches to studying ecology

-descriptive ecology (what?) -functional ecology (how?) -evolutionary ecology (why?) These are the three approaches used by ecologists. • Descriptive ecology asks "what" questions. These kinds of studies are what we watch with great interest on the National Geographic or Animal Planet channels, or any nature show on TV. They show us what lives where, what the organisms do in their daily existences, what they eat, what their habitats are, etc. These kinds of studies are largely observational, but are what every ecologist gets into this science to do. They are usually big projects and often generate additional, complex questions while trying to answer what looked simple on the surface. An example would be an ecologist studying the nesting habitat of the red- cockaded woodpeckers (an endangered species) in East Texas. • Functional ecology asks "how" questions. In these studies, ecologists are trying to figure out how organisms adapt to their environments, how they metabolize food, etc. An example would be an ecologist studying how brown shrimp adapt to varying salinities in Galveston Bay. These studies usually are done in a lab setting, so one of the drawbacks to functional ecology studies is that you get an answer, but it may be far removed from reality if the experiment was done in a controlled lab setting. The flip side of this is that without the controlled lab setting, you may not have been able to get an answer at all! • Evolutionary ecology asks the big "why" questions. Most of these questions cannot be answered because we're asking why something exists today the way it does, without being able to actually study it. This is where the fossil record comes in.

The four biological disciplines closely related to ecology

-physiology -behavior -evolution (natural selection) -genetics The science of ecology draws from genetics, physiology, evolutionary and behavioral sciences.

Three types of selection on phenotypic character

Adaptation works on the phenotypes of individuals to causes changes in the genotypes of populations. Here are three ways that can occur. Using height as the phenotype (and assuming height is heritable), we start out with a population in which height is normally distributed (original distribution). A normal distribution indicates that most of the population is of medium height, with a few at the "extremes" or "tails" of the curve - very tall or very short. In directional selection(most common), one of the tails/extremes is selected against (not fit or not as fit as the rest of the curve). In this example it's the short individuals (shaded area). We won't say here that they die, just that they don't reproduce, which means since short heights will be lost from the phenotype, they will also be lost from the genotype. What does this do to the population? It shifts the bell curve to the right (taller) heights. The population gets gradually taller each succeeding generation. You can see the change on the slide in the bottom figure where the "old" mean line is not at the population mean any more. In stabilizing selection, both extremes or tails are selected against. This causes most of the population to be more "average" height and narrows the bell curve. Mean doesn't change but distribution of height narrows. In disruptive selection, the average is selected against. How does this happen? Short heights mate with only short heights and tall heights mate with only tall heights. Eventually you may end up with a tall population and a short population. Directional selection is the most frequent natural selection mechanism, followed by stabilizing selection. And we do have a few examples of disruptive selection as well. Some examples on the next slides.

History of ecology

Advances after the 17th century - Thomas Malthus (c. 1798) most important • author of Essay on Population (more heretical than Buffons writing) • numbers of organisms increase geometrically, but their relative food supply may never increase more than arithmetically • concluded that food supply limits population (chart adds by 2 on population and food supply times 2, exponential vs. linear) Thomas Malthus' ideas related to the controls on natural population growth were hotly debated at the time. In his Essay on Population, Malthus theorized that numbers of organisms of any population (including humans) tended to grow geometrically when resources were available, but their resources would never keep up (would grow arithmetically in comparison - see math on slide). He concluded that all populations are ultimately limited in size by the amount of their relative food supply.

How natural selection works

And this is how natural selection works.

Approaches to studying ecology •descriptive ecology

And we did some descriptive ecology work too. - functional ecology: We did some plot and transect sampling to identify the plants in each community (what was there & hoe far space they were). Studied the chlorophyll of the leaves of the trees ( called floralfalis= thicker in camping than castings, took soil and moisture smaples) to put numbers in statistics.

Evolution in the common peppered moth in England since 1950

As pollution controls were established and the air was improved, the trees no longer were covered with soot, shifting natural selection back to the light (normal) form.

Evolution and "arms race" between parasitic cowbird and parasitized species that try to defend their nests by ejecting cowbird chicks

Coevolution involving competition or predator-prey relationships is often called a silent "arms race". In North America, we have one of these arms races occurring between the brown-headed cowbird and many songbird species. The cowbirds are parasitic - they don't make their own nests, instead the lay one of their eggs in each of several nests of other host species. The cowbird chicks usually hatch before the host chicks and get all of the host parents' feeding attention, causing failure of the host species nests. Some studies have shown that some host species are "learning" the difference between their own chicks and cowbird chicks and remove them from the nests. So what must the cowbirds do to improve their strategy? Both species are always coevolving.

Approaches to studying ecology

Evolutionary ecology : -low casting forest -high casatinga woodland (lower grown trees, sunlight on ground, -campina Here's an example of all three approaches from a research project I did with some UHCL students in the Amazon. In places along the blackwater rivers in the Amazon are specialized "white sand" forest communities. Three types of white sand forests are pictured in this slide (from left to right): low caatinga forest, high caatinga woodland and campina. In our study area, all three of these types occurred along a 1⁄4- mile transect. The low caatinga forest has dense, tall trees with little light reaching the forest floor. The high caatinga woodland is less dense, with enough light reaching the forest floor that bromeliads can grow on the ground (bromeliads are usually found in the treetops). The campina has very sparse, low growing trees and looks sort of like a little desert. The evolutionary ecology approach would ask why these three communities exist in such close proximity. They all get the same amount of rainfall.

Spread of the Africanized honeybee (Apis melifer adasonii) in the Americas since 1956

Here's a good example. The European honeybee (Apis melifer melifer) that is established in North America is a relatively docile bee that is a good honey producer, but is adapted to temperate climates and does not do well in the tropics. The African subspecies (Apis melifer adasonii) is adapted to tropical climates, but is aggressive and does not produce much honey. In the late 1950s, researchers in Brazil wanted to develop a honey producer that would tolerate tropical temperatures, so they brought some individual African honeybees to a lab in Rio de Janeiro to cross with the European honeybees in the hope of producing a docile honey-producer that would tolerate tropical temperatures. Well, as luck would have it, a few Africanized European honeybees escaped the lab. They were well-adapted to tropical temperatures and were able to survive and establish themselves in southern Brazil. Unfortunately, the Africanized bees were not docile (they were actually quite aggressive) and were not honey-producers. But they were really good at dispersing - all the way through South America, then Central America then into North America. The question for all of those years was what would limit the distribution of the Africanized honeybees, because it was looking like there was no distribution limit for a while.

Evolution and "arms races" between rough-skinned newt (Taricha granulosa) from western N. America and garter snake (Thamnophis sirtalis) that preys on these newts

Here's an example of coevolution between the rough-skinned newt and its predator, a garter snake. The newt produces toxins in its skin to deter the snake. The snake becomes tolerant to the toxins so it can prey on the newt. So the newt makes new toxins to deter the snake. And the snake develops new tolerances to the newt's new toxins. And it goes on and on.

Oropendolas wasps

Here's coevolution between oropendolas (Amazon birds related to our grackles) and wasps. These photos are of olive oropendolas and their nest colony. Oropendolas build long hanging nests in a group. And always situate them around a certain type of wasp nest. Why? Studies on these species have shown that the wasps don't bother the oropendolas but do not tolerate other organisms, thereby providing a level of protection for the colony. Wasps also have been found flying down into the nests and consuming ectoparasites on the skin of the chicks. Benefit to both species: the oropendolas get protection and parasite removal by the wasps, the wasps get food. The traits involved: both are behavioral - the oropendolas nest site selection and the wasp tolerance of the birds.

Distribution and abundance of the red kangaroo in Australia, 1980-1982 Krebs!

Here's the distribution map for red kangaroos in Australia?(over 2 year period) no kangaroos around edges. The limit of their distribution is also the line between blue and pale green. If you know the geography of Australia, you can see that red kangaroos do not inhabit coastal areas or deserts.

Potential effects of two limiting factors on a geographical distribution

In some cases, two limiting factors can work together to determine a distribution. Temperature and moisture are good examples. In this diagram, we see hypothetical temperature and moisture limits for a hypothetical species and how they work together to define the distribution limits for the species. On the x-axis we are measuring temperature. The minimum temperature for the species is 1.6 and the maximum is 5.3, so any temperature within this range will be conducive for the species. Moisture is plotted on the y-axis; the minimum moisture for the species is 1.1 and maximum is 5.2. There are adequate temperatures where moisture limits the distribution and adequate moisture levels where temperature will limit the distribution. And so you get the yellow box, which defines the temperature and moisture limitations, and therefore the distribution limits (based on temperature and moisture) of our hypothetical species.

Amazon water lily and scarab beetles

Last one (I promise). Coevolution between the Amazon water lily and scarab beetles. Amazon water lilies are uncommon across the Amazon, restricted to water about 10-12 feet deep with adequate dissolved nutrients. The plants are rooted on the bottom and have large, floating, pad-like leaves connected to the roots via long petioles.

Relationship between distribution and abundance

Krebs' definition of ecology is "the study of the interactions that determine the distribution and abundance of organisms". So let's start with how distribution and abundance are related. This slide shows how most organism populations occur. In places where there are lots of resources (e.g., food, space), the density of the population will be high. Outside that main area, resources may be decreased and the population density is lower. Outside that area, population densities get lower and lower, until there are no individuals at all. The edge of the distribution of this populations is the line between the light orange (average density very low) and yellow (no individuals) areas on the slide. To say it another way, in order to have a distribution, the density must be greater than Zero!! (Abundance=0 at no individuals, low density is greater than zero, moderate density= Moderately higher)

Amazon water lily and scarab beetles

Scarab beetles are attracted to the white flowers and crawl inside them the first night (photo on right shows a flower cut in half). Inside the flower is a sweet, sticky, brown sugar-like substance that the beetles feed on. They crawl into the open flower at night and stay inside the closed flower all the next day, just eating on the sugar substance. If the flower was pollinated by the beetles (we'll get to that in a minute), then when the flower opens the second night, it is purple and male. The beetles have now exhausted the food in this flower and crawl out to search out another flower. On their way out their sticky bodies get covered with pollen from the now-male flower. The beetles leave this flower and fly to another white (female) flower and as they crawl down toward the sugar they pollinate the white flower. Pretty cool. The coevolution? The lily has done all the work: white female flower, sugar substance, purple male flower. The beetles are just eating. Also interesting is the dispersal of the seeds. In the photo on the left is a fruit full of Amazon water lily seeds. Once the seeds are released, they float for exactly 24 hours, taking up water the whole time, then sink. If they sink in areas conducive to their needs, a new colony can start. And if a new colony starts, the beetles have to find it.

Levels of integration in biology organisms level of integration

Species (singular or plural) -organisms level of integration - fundamental unit in ecology - three-part definition • group of actually or potentially interbreeding organisms (produce and make) • that are reproductively isolated from other kinds of organisms, and (they can breed with each other but not other organisms/ mate but not produce offspring) • that produce viable offspring The species is the fundamental unit in ecology. We may study the cells or biochemistry of organisms in order to understand some functional element of a species, but it is the organism or species that is the most important. Although DNA technology is expanding how we see relatedness among species, ecologists still use this basic 3-part definition to identify species. Accordingly, a species is (1) a group of actually or potentially interbreeding organisms (they must be able to breed so that the species will persist in time) (2) reproductively isolated from other kinds of organisms (they can reproduce with only their species) (3) produce viable offspring (means they produce living offspring that can also reproduce

Stabilizing selection for hatching synchrony in lesser snow geese

Stabilizing selection in snow geese. Hatching synchrony is a pretty cool strategy that we see in ducks and geese. These species lay clutches (egg groups) of 10-14 eggs, but the eggs are laid only one per day. In a clutch of 14 eggs, this means it takes two weeks for the female goose to lay the whole clutch. Yet all of the eggs hatch on the same day. What delays the hatching of the first and speeds up the hatching of the last egg laid? It's sort of a mystery but involves egg survival without incubation and some egg to egg communication. It's very important for the whole clutch to hatch at the same time, because once the first duckling/gosling hatches, the parent is off the nest and leads the young into the water. These young are altricial, in that the parent leads them to water and then they start foraging for themselves very early. You can see in both figures here that for most nests, eggs hatch on the same day (lower figure) and hatching on the same day increases the fitness of the population (upper figure).

Stabilizing selection for birth weight in humans

Stabilizing selection. Birth weight in humans is a good example of stabilizing selection. Small babies have a higher mortality rate than average sized babies (arrow). But babies larger than average also have a higher mortality rate.

A good acclimation versus a poor acclimator

The acclimation ability of these two fish species is compared on this slide. The points on each graph represent the thermal acclimation and death temperatures. In these studies, the researchers increase the holding tank temperatures slowly, then see what the maximum temperature the fish can tolerate is after acclimation. For the sheepshead minnow on the left, you can see that at an acclimation temperature of 5C, the lethal limit temperature is about 32C. As the acclimation temperature is increased, the lethal limit temperature also increases. At 39C acclimation, the fish can survive a temperature of 42C. This is a good acclimator. This species has a wide geographic distribution because it can adjust to a fairly wide range of environmental temperatures. The Arctic char, on the other hand, is a poor acclimator (the name Arctic char should be a hint). This species does not acclimate to temperatures over 21C and the change in the upper lethal temperature from cold to warm acclimation is only about 2C. This means the Arctic char will have a narrower distribution and be limited pretty much to cold water environments.

Amazon water lily and scarab beetles

The plant has a fascinating flowering and reproductive strategy that involves coevolution with the scarab beetles. The lily will send up a flower bud on a long stalk from the bottom of the water, and the flower opens at night. The first night the flower is white and contains the female organs. It closes at daybreak, stays closed all day, then reopens on the second night as a purple flower with male organs. Why?

History of ecology

• Advances beginning in the 17th century - John Graunt (c. 1662) • father of demography (the study of populations) • described human populations in quantitative terms (counted people and tracked them of what growing populations) - Antony van Leewenhoek (c. 1687) • reproductive rates of grain beetles, carrion flies (1 pair → >740,000 in 3 months with all reproduction ), human lice • first attempts to calculate theoretical rates of increase for animal specIt's -Science in general really took off in the 17th century, including the disciplines that would one day weave themselves into ecology. John Graunt was an English statistician who was the first to quantify human population growth (demography is the study of human populations). -You probably remember van Leeuwenhoek as the inventor of the microscope. He used it to study tiny organisms, among which included lice/beetles and carrion flies. He discovered had incredible growth rate. His studies showed the incredible reproductive rates of some of these critters and he was first to calculate theoretical rates of increase for animals.

History fo ecology

• Advances in the 18th and 19th centuries - balance of nature versus natural selection - recognition of interrelations of organisms within communities • Edward Forbes (c. 1844) - communities in British coastal waters and Mediterranean - zones of different depths with different communities • Stephen Forbes (c. 1887) first American - author of The Lake as a Microcosm - affecting one species in a community can influence the whole community Both of these biologists (same last name but not related) studied what we now know as community ecology. Edward Forbes (Britain) travelled with fishermen and discovered that the kinds of fish caught depended on the depth of the trawls, indicating different communities with different species at different depths in the ocean. Stephen Forbes (U.S.) studied all of the organisms in a lake and determined what their feeding relationships were. He was the first to determine that all of the species are linked and removing just one of them could affect the entire community.

Myxoma virus and Oryctolagus rabbits in Australia

• Apparent coevolution between rabbits and Myxoma virus - rabbits that were fit (survived and reproduced) were resistant to lethal effects of virus and passed that trait to young - simultaneously, Myxoma virus increased its fitness by becoming less virulent • virus transmission requires mosquito vector • best strategy is intermediate virulence: not kill host before mosquito can transmit. Here's how coevolution between the rabbits and Myxoma ensured both species could survive.

Levels of integration in biology

• Community - group of interacting populations occupying a given area(roaches/rats/pets not people) - unique property = species diversity - examples (start with plants) : • bottomland hardwood plant community • coastal flatwood plant community •coastal prairie plant community • bay bottom benthic community The next level up is the community, a group of populations in a given area. We measure communities in terms of their species diversity. Most communities are named for the dominant plants they are based up. More on that later.

What is ecology?

• Definitions according to - Charles Krebs: "scientific study of the interactions that determine the distribution and abundance of organisms" (Narrow it down to talk about interaction/prey between species) • where organisms are found • how many occur there • why they live there krebs retired (now an professor of ecology a t university of Columbia retired in 2001, still writing literature)

What is ecology?

• Definitions according to - Ernst Haekel: branch in bio (broad) def: "total relations of an animal to both it organic and inorganic environment" - Charles Elton: (broad definition) "scientific natural history" - H.G. Andrewartha: (aware of environment)"scientific study of the distribution and abundance of organisms" - Eugene Odum: (still alive) "structure and function of nature" (his text book looked at structure function/ energy content)

Natural selection by adaptation

• Determination of clutch size in birds - David Lack (1947) - balance between • proximate factors - physiology of the birds control ovulation laying • ultimate factors - how many young can successfully fledge - determined by genetic, population and environmental factors Natural selection leads to what constitutes the optimal clutch (or nest or litter, etc.) size for any species. David Lack's classic work on birds laid the foundation for understanding the relationship between proximate (physiological) and ultimate (survival) factors in how many young a species will raise. Here is Lack's cost- benefit model. He looked at the energy cost of raising a certain number of young (bringing food to nest) versus the benefit (more surviving = higher benefit). A few chicks in the nest are manageable, but once more than a threshold number, the cost of raising them increases too much. The benefits (leaving genes in the population) increase dramatically when the number of chicks initially increases, but toward the right side of the curve, if there are too many chicks, the cost is not worth the benefit. Where there is a maximum difference between cost of raising and benefit of producing chicks, that's the optimal number. You can apply this to other organism groups as well. Why do humans usually have one child at a time, or cats/dogs have litters of 4-6, or cardinals lay 4 eggs, or fish produce hundreds or thousands of eggs? Why do some plants produce hundreds of seeds and others produce thousands? Cost-benefit relationships.

Natural selection by adaptation Industrial melanism in the common peppered moth (Biston Betularia)

• Early 1800s: mostly light form, few melanics (carbonaria) in England • Over next 100 years, melanics increased in abundance • In some industrialized areas, found only melanics • Light or dark forms follow simple Mendelian genetics • 1950s: HBD Kettlewell's mark-recapture and ecology studies Kettlewell's classic study of industrial melanism and natural selection in common peppered moths.

Ecology versus environmental science

• Ecology: focuses on the natural world of interactions of plants and animals (including humans, but not looking at how humans are impacted) with their natural environments • Environmental science: focuses on human impacts on the Earth's environments (physical, chemical, biological

What is ecology?

• Root from Greek "oikos" (means house/home) • First used as a word by Henry David Thoreau (1817-1862) in 1858 The word "ecology" comes from the Greek "oikos" meaning house or home and "-ology", which (of course) means the study of. The word was first used by Henry David Thoreau in a letter to a colleague, but he never defined it because at that time, people who could read were schooled in Greek and Latin and would have automatically understood his meaning.

History of ecology

• Hunter-gatherers (Had to follow prey around in order to gather fro food, needed to know migration patter, seasoning, dry/wet location) • Agricultural age (People organized into communities/cities able to do that by accomplishing farming to sell/share/provide for people) rice requires water, people used ecology skills learned when to learn crops and where • Egyptians through Aristotle - fear of plagues (Disease that would wipe people out, believed main plague had to do with rainfall) - explanations relating to ecology Ecology is the oldest science known to humankind, even though it may not have come into its own as a discipline until the 1960s. All organisms must eat and reproduce to survive as species. How did early humans find their food? They hunted game and they gathered fruits and seeds. In order to find this food they learned the ecology of the plants (where the plants lived, what seasons they produced fruit, etc.) and animals (migration patterns, reproductive season, etc.). Humans parlayed this knowledge into feeding themselves in farming collectives, then cities. Aristotle (4th century BC), among other notable contributions, might be considered the first ecologist. When people started living in cities, they began suffering from diseases of crowding and feared the plagues that came all too frequently. Aristotle sought to find a reason for the plagues and theorized that excess rainfall caused them. Although an ecology-related explanation, it left out a few important steps (the rain drove rats out into the open, rat fleas carrying the plague bacillus then bit humans).

units of natural selection

• Individual • Gametic: selection at level of sperm and ova • Kin: social organization, altruistic behavior •Group: population broken into groups with different genetic, adaptive attributes •Sexual: dominance in males or females Ecology focuses mainly on individual natural selection (what we've been discussing in this unit), however, kin and sexual selection are also important. We see kin selection at work in killdeer parents who play "broken wing" to lure predators away from their nest, or sentries in meerkats. Sexual selection occurs in hoofed animal herds where males have harems and in Attwater prairie chicken colonies where males "boom" on their leks and females choose their mates from the sidelines.

Transplant experiments

• Interpretation - transplant successful • distribution of the species is limited either because the area is inaccessible or because the species fails to recognize the area as suitable living space - transplant unsuccessful • distribution is limited either by other species or by physical and/or chemical factors Possible conclusions from a transplant experiment.

Why natural selection occurs?

• Natural selection is dependent on - genetic variability among individuals (ex. Of populations of organisms that are endangered species that genetic variability is gone, its dangerous because they cannot survive an environmental change/disease) if theres no genetic variability to improve fitness they'll be dead. - heritability of genetic traits (must have the best traits but need to be able to o be passed down to your offspring, if not there will be no natural selection) - influence of the environment on survival and reproduction (environment will determine whose fit and who's not fit, those fit for cold are not fit for warm) For natural selection to work on a trait, that trait must vary among individuals in the population and it must be heritable. The last piece of the puzzle is the environment and the role it plays in the species survival. A trait that provides better fitness under changing environmental conditions will be important in natural selection.

Natural selection by adaptation

• Natural selection operates on phenotypes • Changes in gene frequencies occur only when there is a correlation between phenotype (fitness) and Genotype The phenotype is the expression of a gene in the individual. Your complex genotype for left handedness is expressed in your simple phenotype - you are left-handed. If being left-handed provides survival fitness under certain environmental circumstances (let's say hot climates for an example) - and those circumstances occur at some point (global warming) - you would adapt (survive and reproduce) when right-handed people would not. However, this would lead to a change in the frequency of left-handers in the population only if there's a correlation between left handedness and tolerating the heat.

What mechanism drives evolution?

• Neutralists - evolution occurs by chance (genetic drift) - genetic mutations occur (rarely when they do they're stable) 1/1,000,000 DNA replications - some get fixed in the population → change In ecology, genetic drift does not account for the evolution that occurs in populations. -before most scientist thought that if there were any changes in population they just occurred by chance or divine pronouncement.

Levels of integration in biology population

• Population - group of organisms of the same species occupying a given area at a given time - unique property = density - examples •humans • bluebirds(1) • fox squirrels A population is a group of organisms of the same species occupying a given place at a given time. Populations are dynamic, always changing, so have to put area and time constraints on them to define them. Think about a class you were in on campus before the pandemic closure. At the start of class, the room may have been full (time = 7:15 start time of class, room = 3232 place). When class was over, what was the population of the room? 100 It went from full to zero in a short period of time. 10pm We usually measure populations in terms of their density, or how many individuals of that species are in the space. Some examples are on the slide. How many species of domesticated dogs are there??

Analyzing geographic distributions

• Questions - Why are individuals of a particular species present in some places and absent in others? - What limits the distribution of a species? The central question in this section is what determines the distribution of a species? To answer this, we often have to first determine why a species is not present in a place.

Myxoma virus and Oryctolagus rabbits in Australis

• Rabbits (Oryctolagus cuniculus) were introduced to Australia in late 1800s • They rapidly increased in abundance → severe problem, destroyed rangelands used for sheep • Myxoma was known as common parasite of new world rabbits - attacks immune system - causes smallpox-like disease - was in balance with S. American rabbit populations • Myxoma virus was introduced as a potent killer of Australian rabbits - initially killed 99.8% of the rabbit population - but within three generations, virus only 40-60% effective - rabbit populations increased and reached an equilibrium with the virus

What mechanism drives evolution? In Natural Selection

• Selectionists - evolution is driven by adaptation and natural selection (genetics) (e.g., Darwin, Wallace in the 1850s) - parameters • genetic variation • excess offspring • competition • fitness • heritability of traits Natural selection found its way into ecological thought through the research of two mid-19th century explorers: - Charles Darwin (world travels aboard the Beagle) and Alfred Russel Wallace (explorations in the Amazon). - Both separately came to the same theory that evolution is driven by adaptation and natural selection. Natural selection involves five parameters: • The species must have enough genetic variation to allow selection to find the "best" traits. (If theres no genetic variation cant be used) • excess offspring: Reproductive events must produce more offspring than the environment can support. • There is competition among those offspring for the resources in short supply. • The most fit survive. "Most fit" doesn't necessarily mean strongest; it means most fit for whatever conditions are present in the environment. -So the smallest might be the most fit, or the smartest or the meanest or the wiliest or the largest or the one that doesn't need a particular nutrient, etc.heritability of traits • Natural selection (change in genetic traits due to the above factors) only works if the traits being selected for are passed on to future generations. If being smart is not genetic, then it's not heritable and won't contribute to natural selection.

Limiting factors

• Shelford's Law of Tolerance - (adapted from Liebig's Law of the Minimum) - the distribution of a species is controlled by the one environmental factor for which the organism has the narrowest range of tolerance, adaptability or control - examples of limiting factors • physical • biological What limits the distribution of a species? Most likely it will be some aspect of the physical or biological environment. Shelford's Law of Tolerance tells us that the distribution is limited by the one (or maybe a combination of a couple) environmental factor that the species has the least ability to adapt to.

Coevolution

• Specific trait of Species A evolves in response to a specific trait of Species B, which in turn evolves in response to the trait of Species A • Ehrlich and Raven from studies on plants and insects that eat them • Specific and reciprocal • Diffuse coevolution: >2 species involved Natural selection in one species is often driven by other species. This is coevolution, where changes in a specific trait of one species drives changes in a specific trait of another species and vice versa. Diffuse coevolution involves more than two species, but our discussion here will be coevolution between only two species.

Methods used to study ecology

• Theoretical (mathematical) • Laboratory • Field • Plant ecology versus animal ecology How we study ecology. Eugene Odum's methods were to convert all life into energy and determine how energy flows through communities (theoretical). Some ecological studies are done in the lab, but we've discussed some of the pitfall of that. The best way to study ecology is in the field, but that's not always feasible. Sometimes we have to use all three methods to obtain an answer. I have found in my ecology classes over the years that more students are interested in animals than plants. In ecology, however, we have to give the plants their due attention, since all of ecology (and organismal life) depends on plants. If you have a plant community, the animals will be there too.

Natural selection in B. Betularia

• What is the specific agent of selection for fitness in the dark form moths? - industrial site: tree trunks darker from soot, dark form camouflaged - non-industrial site: dark forms stand out on lighter trunks • Number of B.betularia eaten by birds. Birds feed by sight and can see the dark form moths on light colored trees. Natural selection favored the dark form on sooty trees.

Three hypothesis for speciation

•Allopatric (geographic) speciation - physical or geographical separation - each population undergoes independent evolution, adaptation to separate environment •Parapatric speciation - part of population enters new habitat - no physical barrier •Sympatric speciation - occurs within population Before any differences can be seen

Examples of coevolution

•Oryctolagus rabbits and Myxomavirus • Tropical ant-plant relationships: melastomes and Inga • Cecropia trees and Azteca ants • Oropendulas and wasps • Amazon water lily (Victoria amazonica) and scarab beetles (Cyclocephala sp) Five examples of coevolution over the next few slides. The rabbit-virus coevolution is from Krebs (2009), the others are from our study-abroad expeditions to the Amazon.