Aquatic Ent-- Week 8 Mating Systems

What are the 5 general ideas of mating systems?

1. Sexual Selection (Darwin 1871)

2. Bateman’s principle (1948)

3. Parental investment theory (Trivers 1972)

4. Handicap Principle (Zahavi & Zahavi 1997)

5. social selection (Roughgarden 2004)

Sexual selection— why do males have such elaborate behaviors and morphologies?

1. competition between males for females

2. Mate choice by females

Bateman’s principle— Why are eggs are a limiting resource and not sperm?

1. sperm in cheap; male fitness is limited by their ability to inseminate females

2. eggs are expensive— females fitness is limited by egg production

What is Parental Investment Theory?

the sex that invests more time, energy and resources in raising offspring = more selective when choosing a mate.

the sex with the lower parental involvement = compete more for mating opportunities.

What is the Handicap Principle?

Shows costly behaviors, displays; honest signals of male quality

What is social selection?

It differentiates between gender and sex

it accommodates multiple genders— some male damsel/dragon flies have different color morphs (territorial, female mimics)

What 2 things are included in swarming? What is the function of swarming?

1. swarm markers

2. Males— male dominated

3. Functions as mate selection and species identification

What is a territory? What can it cause? When can territories become dangerous?

1. territories are an oviposition site guarded by a male

2. Can cause aggression— circle fights, speed and agility competitions

3. They can become dangerous when both males are territorial (6%) or one is non-territorial (28%) → in Odonates

What are the two types of acoustic signals? How are they made? What do they mean?

1. Drumming in Plecoptera→ abdominal vibration on substrate; possible form of prezygotic isolation

2. Stridulation in waterboatman→ sound made from ‘pala’ on foretibia; males call and receptive females answer (a password)

What are hydrodynamic waves? Who causes them? And why?

1. Wave propogation on the surface

2. Hemiptera→ Gerridae and Belostomatidae cause this

3. Indicates receptivity; possibly a species identifier

What are pheromones for? Who uses them the most?

1. A species specific chemical/sent for mating, finding food, and warning

2. Diptera, Coleoptera, Trichoptera→ they have fluffy, thick antennae

What is different about odonate males? What are the steps in mating within odonates?

Males have 1 genitalia at the tip of their abdomen and a 2nd under Ab 2&3

1. Before mating, males transfer sperm to 2nd genitalia

2. Male holds female with grasping appendages (tandem)

3. Mating occurs when female loops tip of abdomen to males 2nd genitalia→ makes heart shape

What happens in sperm competition among Ebony Jewelwings (Calopteryx maculata)? What is the outcome?

1. males defend territories (non territorial males also present)

2. Males remove sperm from females after pervious matings→ last male advantage

3. Guarding the female is important for egg laying in Calopteryx (13min = 90-140 eggs guarded vs 2min= 15 eggs not guarded)

What are the 3 sexual conflicts in water striders?

1. Unnecessary Mating is costly to females

2. There is a benefit in resisting copulations

3. defense and counter-defense between males and females→ neither win

What trait has evolved in female water striders to lessen unwanted advances?

They have a little spine on their second to last abdominal segment that they can manipulate to push the male off.

What trait has evolved in male water striders to combat sexual conflict?

Males have hooks and many hairs on their hind legs, and hooks on their antenna to help grab onto females

What is the evolution of our understanding of back-brooding in Giant Water Bugs (4)?

1. 1899— We assumed females carried the eggs (traditional parenting)

2. 1899— “Male chafes under burden” hypothesis

3. 1906— Idea of Forced labor & care

4. 1976— Host Manipulation Hypothesis (HMH) is at odds with the modern selection theory

How is paternity assurance shown in Giant Water Bugs? (4)

1. males carry eggs; invest energy in care

2. Females store sperm (up to 3 months)

3. Males insist on repeated couplings

4. ~100% sperm priority— most recent sperm will fertilize eggs

What is the order of copulating activities in Giant Water Bugs?

1. Male makes a pumping motion

2. female tries to oviposit

3. male pumps again

4. copulation happens

5. male taps females back

6. pair uncouples

7. female lays ~2 eggs

8. female leaves

9. male broods eggs

What are the 2 kinds of parental care?

1. Back brooding— keeping eggs on back

2. Emergent brooding— laying eggs on vegetation & guarding them

Why did back-brooding evolve in giant water bugs? (3)

1. Large body size— big prey (frogs, fish, birds)

2. Big eggs= big problems— O2 diffuses slower in water; eggs have large SA= more need for diffusion

3. eggs dry out easily

How did water bugs evolve to be bigger? What are the constraints?

1. growing bigger between molts— Dyar’s Rule limits growth by molts to 1.4 times

2. add more molts— Hemiptera are fixed at 5 molts

3. Bigger egg size— head start on being big→ able to grow bigger; big eggs create diffusion issues

Why do males care for the eggs and not females?

1. Females can’t oviposit on themselves?— No, emergent brooding evolved first; either sex can provide parental care

2. Greater cost of parental care by females?— this could be true; it takes a lot of energy to lay eggs, and females produce eggs multiple times

3. Males are better egg defenders?— possible, males could be more readily available to guard eggs and have the energy for it.