Lecture 3 notes- Mate guarding PDF

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BLGY3135 Advanced Topics in Behaviour: from sex to death

Lecture 3- Mate guarding 1 - Precopula (before) 2 - Amplexus (during) 3 - Postcopula (after) Differs from courtship: Duration- over several days Function (waiting for female to be available vs stimulating receptivity (courtship). Paternity guarding

Questions? Why might it evolve? Why might it occur in 1 species, but be absent from a closely related species? Precopulary mate guarding Amphipod Gammarus Females: - Receptivity of females is asynchronous – different females available for mating on different days - Females have a small window of when they are able to mate - Oogenesis- build up of resources around eggs- transfer to eggs as oocytes develop, lay eggs, malt at same time - When they malt- newly laid eggs are deposited to their brood pouch - They are then available for mating by males - Females have a monthly cycle but not synchronous Males: - Males can mate all time during month except day when they are malting- too fragile Sandhoppers - No mate guarding - Both male and female sand hoppers hop up beach to mate at full moon - this is influenced by spring tides when the tides are low - Synchronous with the moon Hypothetical population of shrimp • Males are looking for females • Female are not in the correct state to mate • Females are still brooding eggs from their previous mating

BLGY3135 Advanced Topics in Behaviour: from sex to death

• Purple circle- days till female lays next eggs • 0 days- males will mate with her • Only few females available at a time Genetic editing:

- Mutation created in males- able spot if a female is going to mate soon

- Arthropods use olfactory cues to detect how close a female is to mating

Females are next pair up Instantly mate with the male

BLGY3135 Advanced Topics in Behaviour: from sex to death

Some males have mutation where they are able to know if a female is close to mating- day 1/2 Males will guard them

Those males that have evolved new behaviour These males do better than the males swimming around Mutated males invest 2 days into guarding females

Other males are swimming round looking for females Slim chance of them finding a mate

Genes for guarding should spread throughout the population

Eventually gets to the point where there is no point in investing a long time in a female eg 28 days Better to take a risk than guard Trail off between how frequent guarding is and how common females are What is the sex ratio?

Sex ratio is 50-50

Ratio of available males to available females is 4:1 Operation sex ratio- strongly male bias And females come into receptivity at different times If all females were receptive at same time there would be no advantage in guarding females Guarding genes will therefore spread

BLGY3135 Advanced Topics in Behaviour: from sex to death

Precopula guarding may evolve when the OSR is male biased Sex ratio SR= ratio of males to females Operational sex ratio OSR = ratio of males to receptive females Gammarus used to show male complex mating decisions Precopula mate guarding may be selected when: - Breeding is restricted in time - Only a small proportion of females are receptive at any one time - Female receptivity is asynchronous

Size assortative paring 1. Male/male competition - Only big males get to big females - Fight off rival 2. Loading constraints - Small males can’t hold onto large females - Males are washed downstream- they use their swimming effort to hold on than swim Size assortative pairing in G. duebeni Big males mate with big females Small females are guarded by small males Why?- Do they prefer each other? Size & fecundity in female G. duebeni Big females have more eggs - Bigger brood pouch - More eggs Males compete for bigger females - Not many in supply Size assortative pairing & loading constraints Big males need to guard females smaller to swim and hold onto the female at same time Slow flowing water- ratio for male and female are similar in size Fast flowing water- larger difference in ratio- male and female are different sizes - females are smaller Size of pairs formed was affected by stream speed Fast speed- males guard small females

BLGY3135 Advanced Topics in Behaviour: from sex to death

Costs of precopula 1. Loss of time to search for other mates How long should a male guard? Male selected to minimise his search time + guard time Male biased sex ratio - Long precopula- 7 days More females- abundant - male choosiness - short guard time Time spent guarding depends on population sex ratio Sex ratio increases precopuila duration increases 50%- 2 weeks 5%- 8 days 2. Physiological costs - Swimming against the current - Carrying extra body mass 3. Increased risk of predation – visual predators Dunn et al 2008 Animal Behaviour 76; 1289-1295 Risk of predation affects pairing Chuck animals in tanks See how quickly they form pairs Wait 30 minutes Pairs were higher in control than in one where fish tank water was dropped in No predator but smells- olfactory cues of a potential predator Risk of predation may make males less choosey Premature cue water - Males are less choosy - grab first female they see - 50 50 for large and small females chosen Control water (no predator cue) - Spent more time choosing female - Twice as likely to pick large females

Amplexus

BLGY3135 Advanced Topics in Behaviour: from sex to death

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Toads live on land Come to the river for breeding season Female is going towards pond Male guards her in order to fertilise her eggs Females wraps string of eggs round vegetation Male fertilises them if they have not been beaten up by a lager male

BLGY3135 Advanced Topics in Behaviour: from sex to death

Davies & Halliday 1977 Nature 269 Davies and Halliday 1979 Anim Behav 27 Toads in the pond during breeding season Toads breed in the spring Males arrive at pond in March By April all males of the population are at the pond 300 males in pond over duration of 2 weeks Never meet more than 80 females normally in pond Females come to the pond once a year Make way to pond guarded by a male, lay eggs then leave Males hang around pond for the whole of the breeding season to mate with as many females as possible Paired and single toads in the pond during breeding season There are no single females Many single males Strong operational sexual bias Breeding is asynchronous Breed within 2 weeks but on different days Strong selection for males to guard

Sizes of paired & single males Smallest males are the males that are single on land Largest male is the male in spawning pair Small males are ousted by larger males

BLGY3135 Advanced Topics in Behaviour: from sex to death

Amplexus in Bufo bufo Start- a - 41 x 3 toads in tank - 1 female and 2 males (small and large) - Both equally likely to garb onto her at start 5 mins- b - 18 to large male - 23 to small male 24h- d - If big male got onto female first he wouldn't get kicked off by small one - If small male got onto female first he could get kicked off by large male - 13 kept by small male - 10 taken by large male

BLGY3135 Advanced Topics in Behaviour: from sex to death

Postcopulatory mate guarding Dung flies- Scatophagia sterocaria Guarding paternity Make sure no one else ousts your sperm - Insects - Bird - Humans • • • • • • • • •

Flies lay their eggs in cow pats Female arrives and is mated by male Starts to lay eggs Males hang around Guards female Inseminated female Spermathecal duct full of sperm Find new female?- more mates for offspring Waits 15mins

1. Camouflage? Bright male 2. Threat or sacrifice. Bird can take both male and female 3. Aid oviposition. Difference in how fast eggs are laid 4. Reduce competition from future mates.

Last male precedence Important aspect of mating Seen in lots of vertebrates and invertebrates Insects demonstrate last males sperm precedence Last male to mate gets most of the matings 1st female Female mated with m1 and m2 100 fertile 2nd female Female mated with male 1 Male 2- irradiated – sperm would fertilise egg but it wouldn't develop 20% viable 3rd female Mates with irradiated male then normal male 80% viable eggs No equal chances in fertilisation Best strategy- be the last male When does it pay to guard? Pays to guard when there is competition Cost to guarding- time No competition- don’t waste time guarding

BLGY3135 Advanced Topics in Behaviour: from sex to death

Any competition- guarding males will be last male If never mated before- 100% of eggs are his If she has mated before- 80% will be his fertilised 1. mating immediately precedes fertilisation 2. high male density & struggles for females 3. In multiple matings, last male precedence 4. Males succeed in preventing majority of take overs Bird song • Attract mates • Defend territory • Guard mates- tell other males not to try and mate with their female Bird song & mate guarding • Song rate will peak when females are most fertile • Males in better condition will produce more songs (costly) • Rival males will be deterred by guarder’s song Male song & guarding Great tits Don’t sing much while nest building Until shortly before first egg- 1 week Song rate goes up Peaks when egg is laid

BLGY3135 Advanced Topics in Behaviour: from sex to death

Males in good condition sing more Males eat extra food so their song rate increases which can be costly Complex songs deter rivals Strong selection for complex songs by experienced males with good food resource Duetting in rufous-and-white wrens Paternity guarding hypothesis: Male creates duets to advertise their partners mated status and minimize EPC attempts Play song to males See how they respond Played during: Fertile period- Big risk – extra pair copulation Non fertile period- Low risk Intrusion stage- play songs from intruder male Duetting stage- play songs from resident female- does he duet? To deter pretend rival males? If duetting perform function of rival male- higher in female fertile period Threat of a rival male: More duetting More physical guarding

BLGY3135 Advanced Topics in Behaviour: from sex to death

Duetting is higher in fertile than non fertile period A lot to loose Extra pair copulation

Control Not just territory Other sounds as well Same amount of independent songs

BLGY3135 Advanced Topics in Behaviour: from sex to death

Physical guarding Higher in fertile period

Threat of other males encourages males to duet with female when in fertile period Risk of EPC leads to EP paternity

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Bird duets When females fertile males increased deuting But not other song They physically guarded more Experimental evidence for paternity guarding hypothesis

Marriage & mate guarding • Non contact mate guarding • Marriage status • Female wears ring mostly

Mate guarding effort highest at women’s ovulation Ovulation detected through pheromonal cues Human sexual behaviour Jealousy is high when female is ovulating Days since menstrual onset Day 11- females are fertile Number of days since start of period till ovulation Money earned- sex workers Some physical contact with males Men detect ovulation tipped higher Other studies show this too Survey women or men Attitude or partners behaviour More jealousy during ovulation cycle Water striders- Aquarius paludum insularism Water striders- Aquarius paludum insularism Post copula guarding during egg laying Increased eggs female lays Reduce parasitism Avoidance of egg parasitism through submerged oviposition by tandem pairs in the water strider, Aquarius paludum insularis (Heteroptera: Gerridae)

BLGY3135 Advanced Topics in Behaviour: from sex to death

Number of eggs laid (open squares) and proportion of parasitized eggs (solid triangles) as a function of the distance from the bottom of pool. Zero depth means the water surface and the higher values of depth are nearer to the bottom of the pool. Error bar: SD. Hosts to parasitoids wasps Lay eggs in larvae then burst out Female water striders are guarded Lay her eggs at deeper depth Less likely to be parasitised Depth- has effect on parasitism Water strider guarding decreases parasitism by the wasp Tiphodytes gerriphagus - Aquarius paludum insularis - Females carry gurading males on their backs - Guarded females lay eggs deeper in water - Increased egg number - % eggs parasited decreased with depth Decreased parasitism by - Guarding benefits females and males Jumping spider Phidippus clarus • Guarding also reduces • Female remating • Cohabitation: males spin a silk retreat next to subadult females and guard them until they are mature Precopula guarding also reduces Female remating Black- cohabited with male White- none More likely to remate if she hasn’t been guarded by male in subadult phase – white bars Less likely to mate with other males if guarded...