BIO331 Module 1

List the main environmental factor that distinguishes promiscuity from hermaphroditism

Abundance of mating partners. In promiscuity there are many partner options; in hermaphroditism there are few partner options.

2. List two important scientific differences between the theory of Fisherian runaway selection and the handicap process of sexual selection.

1) Fisherian = trait and preference get genetically coupled (unlike handicap, which does not posit anything about genetics of preference). 2) Handicap = makes predictions about the information contained (Fisherian does not make any assumptions about signaling information in trait).

What makes lek and scramble competition polygyny distinct from the two forms of defense polygyny?

1) Males aren't defending females in lek and scramble competition polygyny. 2) Males don't provide any material benefits, other than sperm/genes, to females in lek and scramble competition polygyny.

Imagine that you have designed an experiment in which you experimentally shortened and elongated the tails of long-tailed widowbirds. As with previous experiments, you find that birds with experimentally elongated tails produce a greater number of nests than birds with experimentally shortened tails. You have the idea of also tracking their survival rates across years, and find that birds that had experimentally shortened tails survived at a higher rate. Using your understanding of natural selection, why would we not have enough evidence to say that short tails have been selected for?

A common mistake that people make is equating survival and fitness. Though survival and longevity often predict fitness, sometimes it does not. A widowbird that lives 15 years but produces no offspring has a lower fitness than a widowbird that lives 2 years and produces 30 offspring. The next generation of widowbirds would have more genes from the short-lived and long-tailed widowbird than the long-lived and short-tailed widowbird. Also, from the information at hand, there is no evidence that there is a heritable basis to variation in tail length in these birds.

Which is NOT a type of signal?

All are correct (auditory, visual, electrical, tactile, chemical)

Among all other possible sex differences, this is the key trait that gives rise to traditional sex differences in reproductive investment and mate advertisements, competitions, and selections:

Anisogamy

Explain why heritability is challenging to calculate, even within lifetimes or generations of individuals.

Because environmental conditions and interactions with genes (namely gene expression) are constantly changing, thus affecting genetic and environmental variance

Absolutely! Holland and Rice (1998) recognized that both processes - Fisherian runaway and handicap signalling - likely exist in natural populations. There are some mutant males in natural populations that are cheating female's calculated honesty of a signal and its costs, and others who are more honest. In a population where signals are honest, cheaters could be favored by natural selection because they pay lower costs for better signals. But this means that the "cheater" genotype should quickly spread through the population, and females should then start to receive lower (or begin paying) costs for choosing the more exaggerated ornament. This in turn selects for females to disprefer the most ornamented males. The evolution of negative preference for the ornament should then:

Any of the above are possible (Select for males with weaker ornaments, Select for the signal to become more strongly linked to underlying traits of interest, restoring honest communication, Cause complete loss of the signal, because it is beneficial to neither males nor females, Select for males to cheat even more, by presenting an even more exaggerated or different ornament)

Describe why sexual conflict does not always result in maximal fitness in both sexes

Because males and females have genuinely different strategies that maximize their fitness. Males, on average, are favored to inseminate many females and care little for offspring. Females are favored to care for young they know is theirs and that they rarely produce (and thus are prized occurrences). Someone has to give in this battle, and depending on which sex achieves more of their fitness maximum, the other one suffers by comparison.

Explain why mating with only one partner for life is typically maladaptive in animals.

Because this is a risky and limiting fitness strategy. If your mate dies or leaves you, and other animals in the population take on a new mate under a similar circumstance, they then have more opportunities than you to pass on more genes. This ultimately means that your "stubborn faithfulness" (and associated genotype) is likely to be outpaced by the other strategy of continuing to mate/breed later in life.

Male bullfrogs produce loud vocalizations (croaks) during the mating season. Body size is a strong predictor of vocalization frequency, with larger males producing deeper croaks. Devise a hypothesis to explain how male vocalization frequency and/or body size may provide females with mating benefits

Bigger males may be superior competitors, fighting off rival males and giving females access to superior resources in the environment. Due to their large size, bigger males may produce more sperm and increase a female's likelihood that her eggs are inseminated. Bigger males with deeper croaks may have better genes and thus provide a female with higher-quality offspring. If male croak frequency or body size is heritable and preferred as a sexual trait, females may inherit those genes for her male offspring, such that sons also have these advantageous traits.

A few years later, work done by Russell Lande (1980, 1981) and Mark Kirkpatrick (1982), using mathematical models of evolution, showed that exaggerated and preferred traits need not be linked to the viability of males, and an ornament could evolve in this condition. Therefore, there was a tremendous conflict between the idea that ornaments evolve to reflect traits that are beneficial to females, and that ornaments can evolve with no underlying purpose whatsoever. How could these ideas coexist?

Both processes CAN exist, depending on the particulars of the population, and one process could be stronger than the other at some points in evolutionary time.

Fireflies that produce flash displays are rather unique among nocturnal insects in that they use a visual rather than a chemical signal to communicate. Provide a hypothesis to explain why visual signals are rare among nocturnal insects.

Darkness (lack of sun) at night means that color/behavioral visual signals are difficult to perceive by signal receivers. Chemicals or sounds, however, are not dependent on access to a large amount of light for successful environmental transmission.

Do you expect dishonest signaling to occur more frequently among members of the same species or members of different species? Explain your answer.

Dishonest signaling should occur more often in members of different species, due to the fact that they share fewer genes in common and thus are less likely to cooperate towards a common goal (e.g. mating, parenting, resource defense). Instead, they may be more likely to deceive or eavesdrop to their own selfish benefit. Now that's not to say that members of the same species do not signal dishonestly - there certainly are some examples of deceit that can occur between the sexes or between parents and offspring. But they're notably less common within species than between species (especially in predator-prey contexts).

A heritability of zero means that there is no variation in the behavioral trait among individuals.

False

Maternal environmental effects do not have a genetic component.

False

There is a low environmental potential for polygamy in bullfrogs because these animals breed synchronously and in high densities.

False

Communicating parties using a sexual signal can be from different species. Do you think this is true or false?

False. Sexual signals facilitate mating decisions within species (between the two sexes). There are instances in nature where mistakes are made and animals attempt to mate with the wrong species (or even wrong objects, like some frogs who mount rocks), but in this case there is no net benefit for both the sender and receiver, and thus it does not officially involve a signal. Also, if a different species is exploiting a sexual signal for its benefit, it is no longer used a signal at this point, i.e. it is a cue. Lastly, a signal by definition must have evolved for its communicative purpose. Because reproductive barriers prevent two species from mating (species hybrids being the lone odd exception), sexual signals cannot evolve for the purpose of increasing mating success between two species.

A hypothetical insect species that exploits a predictable, clumped resource base and experiences high predation would be predicted to have a mating system typical of ____________ polygyny.

Female-defense

3. Give one direct benefit and one indirect benefit that female animals can gain by selecting a high-quality mate.

Females can directly get resources, good father, or good protection. Females can indirectly get good genes, diverse genes, different/complementary genes

1. Provide two reasons why female animals tend to be more choosy when selecting mates than do males and one reason why we occasionally observe sex role reversal in some species.

Females produce large, expensive eggs, so they are more heavily invested into reproductive events than males (who produce small, cheap sperm). Also, females (as egg incubators or live-bearers) are more certain the offspring are their own and thus are more willing to invest in them, thus leaving them more choosy towards mates. Sex role reversal occurs when males become more invested than females in reproduction, due to extenuating environmental circumstances (breeding season is short, safe locations to keep eggs are rare).

Why might a female choose to mate with a male that has good genes?

Females then acquire good genes for her offspring, whether it be for their survival or for traits that assist in their reproduction (e.g. attractiveness, competitiveness).

That's right - Fisher didn't factor in the costs of developing sexual ornaments. Sexual ornaments are exaggerated traits that, assuming they had no sexual function, would depress survival, and ultimately fitness. So, perhaps the missing piece of the puzzle was that sexual ornaments needed to serve some beneficial function. It is clear that the ornament serves a benefit to the bearer of the ornament if it helps them gain access to mating with the opposite sex. But what about the choosy sex? After all, if the choosy sex receives no benefit from mating with a male with an exaggerated ornament over one with a weaker or no ornament, then natural selection should:

Force females to disprefer the trait, leading to its eventual loss from the population

The colors and patterns of butterflies can communicate to predators that they contain toxins and should not be eaten. A Batesian mimic is a species that contains no toxins but has evolved to mimic the colors and patterns of a toxic species. The Batesian mimic takes advantage of the protection offered by the toxic species ("the model"), without having to pay the cost of building internal toxins. Explain how the relative frequency of mimics and models might influence the evolution of mimicry in this situation.

Imagine these two different scenarios: First, in one geographic area there are a high number of toxic models and a low number of non-toxic mimics. Predators that are foraging on these butterflies are, by random chance, numerically very likely to eat toxic butterflies, and thus learn to associate their colors and patterns with toxicity, and therefore avoid eating butterflies. This means that, on average, it is costly to eat butterflies. This means that developing these colors and patterns is beneficial for both models and mimics, but it is also relatively less costly for the mimic. There should also be selection for models to evolve colors less similar to their mimics, since looking like their deceitful mimics is still somewhat costly to them. At the same time, mimics should evolve to look more similar to models; thus producing an "arms-race" between the evolution of colors in models and mimics. Second, in another geographic area, imagine there is a low number of toxic models and a high number of non-toxic mimics. On average, a predator is more likely to consume the abundant, non-toxic butterflies, meaning they won't regularly learn to associate the butterfly's bright colors/patterns with toxicity; thus, the predators should continue to consume butterflies. Since the signal does not serve its intended function (of reducing predation rates), it does not benefit either the model or mimic and is costly to produce physiologically (especially for the model). Selection might either cause both the model and mimic to lose the signaling trait over evolutionary time, or it might greatly increase selection for models to look less similar to their mimics. At the same time, mimics should evolve to look more similar to models; thus producing an "arms-race" between the evolution of colors in models and mimics.

What is one way you could test for which particular benefit(s) females are gaining by mating with more than one male?

In systems with paternal care, you could experimentally remove the father to see how offspring fare (e.g. growth, survival). In systems where females gain just sperm/genes from male mates, you could examine how many males a female mates with and see if mate # is correlated with offspring productivity (i.e. fitness) by the female.

Explain the difference between intersexual selection and intrasexual selection.

Intersexual selection is mate choice by the opposite sex. Intersexual selection is competition for matings with members of your same sex.

this historical figure in the study of animal behavior is well known for his emphasis on imprinting and offspring learning:

Lorenz

2. Common crossbills are monogamous, while Gunnison's sage grouse form leks and are polygynous. How do you predict variation in male mating success might differ between these two species?

Males crossbills should have less variability in their reproductive success, while male sage grouse should have high variability in their reproductive success. Additionally, male sage grouse mating success should be skewed such that a small proportion of individuals receive a high proportion of female access.

Can you think of any other non-sexual-selection reasons for why males and females might differ in traits?

Regarding non-sexual-selection differences between males and females, it could be due to (1) feeding differences (male and female hummingbirds have differently shaped beaks because they feed on different things, such as more protein-containing insects in females); (2) anti-predator differences (males are often more mobile and need to have traits that provide more advantages in predator defense, as in mammal horns/antlers); or (3) competitive differences in the non-breeding season (flocking male and female birds sometimes differ in coloration in WINTER, because they use the color to signal dominance and settle disputes with unfamiliar rivals).

In 1930, Ronald Fisher generated the hypothesis that exaggerated ornaments used in sexual displays occur because of a genetic correlation between the expression of an ornament in a male and the preference for the exaggerated trait in females (Fisher 1930). Thus, males that express a trait would be favored by females, and over time, preference in that trait would cause further exaggeration of the ornament. As you can see, this would lead to a never-ending loop between trait expression in males and trait preference in females, ultimately leading to extremely exaggerated ornaments. Fisher proposed this process (called Fisherian runaway selection) as a way to explain the evolution of perplexing and costly colors, sounds, and smells of animals. Fisher's idea ignited a debate about the mechanics of sexual selection and how exaggerated traits appear and are maintained in organisms. But there were problems with Fisher's idea. What do you think that problem was?

Natural selection should prevent a costly trait, such as an ornament, from evolving if it serves no functional benefits

Models for how sexual selection operate are often thought of as mutually exclusive. Instead, they are probably which of the following?

Not mutually-exclusive

What are the three main parts of an animal communication event?

Sending, receiving, and responding to a signal

Polyandrous mating systems traditionally favor this form of parental investment strategy by adult males and females: ___________________.

Sex-role reversal

Which of the following study types would be least effective for discerning how heritable the migratory behaviors of butterflies are?

Sibling comparison

3. How is social monogamy similar to and different from polygynandry?

Social monogamy is similar to polygynandry in that males and females have at least one pair bond, but in polygynandry, males and females have multiple simultaneous pair bonds. In social monogamy, matings outside the pair bond are covert and extra-pair matings have the potential to disrupt pair bonds.

List the three factors that determine the environmental potential for polygamy in animals.

Spatial variation in breeding, temporal variation in breeding, operational sex ratio.

A newly discovered species of salamander was found to have male-only parental care. Because of this, we would predict that sexual selection for female display traits should be strong in this species.

True

1.Design an experiment in swans, which have strongly socially monogamous pair bonds, that tests the two different hypotheses for the evolution of monogamy.

The two hypotheses are mate-assistance (male is needed to help the female raise offspring) and mate-guarding (male follows the female to ensure his sperm fertilize her eggs). You could remove males from the presence of females at two different times. One group of males (let's call them group 1) could be removed just after the copulation period, and the other group (group 2) as the young are being raised. If, after returning males to their mate, females divorce males more often in group 1 than group 2, then it's more likely that males evolved to be monogamous in order to protect females/fertilizations. However, if females divorce males (or offspring suffer significantly more) in group 2 more than group 1, then mate assistance is likely the key male role in this monogamous species.

Describe the fundamental reason behind why mutual mate choice or sexual role reversal evolves.

These evolve when males are pressured to provide parental care. Thus, being heavily invested in reproduction, males can be choosy over female partners, either just like females are (as in mutual mate choice) or more so than females (as in sex role reversal).

Predatory katydids mimic the loud song of male cicadas, which attracts female cicadas interested in mating. Explain how this is an example of aggressive mimicry.

This is an example of aggressive mimicry because of both the mechanism for how katydids attract cicadas (by mimicking the male's song), and because of the costs and benefits incurred by each party. For katydids, the costs are that they must invest in the physical structures for producing cicada songs, but the benefits are that they receive a steady supply of food in return. For female cicadas, the costs are that approaching the katydid's song may lead them to being predated (which immediately halts all possible future opportunity to increase fitness). The female cicadas benefit (in mating) if they approach a male cicada's song, but they do not benefit if they cannot distinguish or make an error and approach a katydid song. In this exchange, the fact that katydids (the sender) benefit on average, and that cicadas (the receiver) incur costs on average, lead this to be a deceitful exchange.

Design an experiment to test for a possible innate basis for prey recognition (i.e. a search image for butterfly wing patterning) in insectivorous birds, as opposed to a learned mechanism.

This would ideally be conducted using a developmental-isolation experiment. Capture birds and house them for generations in the laboratory, while not ever feeding them butterflies (or at least the butterflies with the wing patterning to be tested). After a few generations, introduce the butterfly wing patterns to young birds to see if they will recognize them as prey (i.e peck at them). If they do not, then we can test for learning by giving one group of animals the wing pattern during feeding events (either as actual prey or as an associated stimulus), while another group is not fed these. If, after development, you give both groups the chance to feed on these butterflies, and the one developmentally exposed group of birds does so better than the unexposed group, you have demonstrated a learned basis to the feeding behavior.

Grizzly bears are known for their loud roars and large canines. They use these as signals when they encounter a rival male. Design an experiment to test among the different multiple-signal hypotheses for why male grizzly bears have these two signal types

To test whether the loud roars and large canines of grizzly bears convey multiple messages or redundant messages, we would need to manipulate the quality of these signals simultaneously. For example, one might silence the males (e.g. surgically) and using speakers to play three different examples of that male's roar: (1) normal roar, (2) after having its pitch raised, and (3) after having its pitch lowered. Thus, an experimenter could manipulate a male's roar regardless of their original phenotype. Secondly, an experimenter could modify the canine teeth to be shorter or longer than they originally were. Experimenters could then monitor the outcomes of male-male aggressive displays and see how males from the different treatments perform (high-pitched roar & long teeth, low-pitched roar & long teeth, high-pitched roar & short teeth, and low-pitched roar & short teeth). The prediction for the multiple-messages hypothesis is that experimentally altering only one of the two signals (either canine length or roar pitch) would change the outcomes of contests. This might lead us to suspect that the signal which did not appear to influence contest outcome either has no function (which would be support for the unreliable-signal hypothesis) or is used in a different context (e.g. in male-female interactions). In contrast, the prediction for the redundant-messages hypothesis would be that both signals interact to influence contest outcomes (for example, large-canine and low-pitched roar males are most likely to win a standoff). There is also the different-receiver hypothesis, which would be supported if one signal influenced, say, the response of rival males, while the other signal was attractive to females.

What type and category of mating system do modern humans exhibit and why?

Today we exhibit serial monogamy. We bond with one partner, but don't do it for a lifetime typically and we don't really have mating seasons (so we are not sequential monogamists).

What are the traditional sex roles of female animals v. male animals?

Traditional sex roles of males are as courters, competitors, and inseminators of (often many) females. They tend to be less parental. Females, by contrast, are the assessors and selective choosers of male mates, typically investing heavily into young.

Can a signal also serve as a cue? Explain why or why not.

Yes a signal can also serve as a cue when there is a third-party participant in the communication event (i.e. a sender as well as an intended and an unintended receiver). Thus, in the diagram example from this submodule, the male frog (the sender) and the female frog (intended receiver) are communicating via a signal (the male's call), but that same male call is picked up by the bat predator (unintended receiver), to whom it serves as a cue.

Yawning in several mammal clades is hypothesized to serve as a co-opted honest signal of physiological need and social threat/intimidation. Outline a series of evolutionary conditions that could have led to this trait being co-opted over evolutionary as a visual signal of internal state.

a. Yawning served an initial physiological, non-signaling function, such as to increase intake of needed oxygen b. Yawning was at some point exhibited in social contexts (i.e. fights) that often involve the use of visual signals c. Yawning provided physiological/behavioral advantages to individuals in combat, such as the ability (with extra oxygen) to sustain aerobically demanding aggressive interactions and win fights d. Yawning eventually was favored as a social signal because those individuals who yawned and revealed their physiological (i.e. oxygen-supply) and behavioral readiness for a fight intimidated their opponents and reduced his/her interest in engaging in risky, losing combat.

which of these studies would provide you with the strongest evidence for genetic control of a behavior?

artificial selection study

significant shifts in fashion and hairstyles across human generations is an example of:

cultural selection

non toxic colorful kingsnakes that mimic the appearance of noxious and venomous coral snakes are using which form of communication

deceit

which field of study is known for its historical emphasis on describing the series and sequences of animal behaviors in their natural environments?

ethology

a behavioral trait with a heritability of 0 exhibits no variation among individuals within a population

false

dishonest signals are less likely to evolve in mixed species assemblages of fish than in same species assemblages of fish

false

pick the statement that labels the behavioral explanation with the correct level of analysis

functional level - squid change their body color when a predator is nearby so that they can blend into the background and avoid detection

List some traits that may evolve to assist males in winning mating competitions with other males.

large body size, weapons, aggressive behavior, badges of status, intimidating postures, displays of physical performance (flexing, push-ups), loud vocalizations

Which level of analysis can we use to explain how baby kangaroos have the genetic predisposition to climb into their mother's pouch right after birth?

proximate

the sensory exploitation model predicts that the physiological systems and biases of signal receievers play a key role in kickstarting the evolution of new signals

true

the theory of inheritance of acquired characteristics proposed that traits improved within the lifetime of an organism can be passed on from one generation to the next

true

Electrical signals are best when..?

used in aquatic environments