Insects 10- Sex

Insects 10- Sex

1. Polyandry- pros and cons

   • Direct benefits
     • More sperm-- queens only mate once--- get multiple amount of sperm
     • Convenience-- done in one sitting
     • Material benefits
       • Nuptial gifts
       • Nutritious sperm
     • Paternal care
   • Indirect benefits
     • Choose a better individual
     • Sperm competition-- selection pressure on sperm in males
     • Dilution of genetic imcaptability
     • Genetically diverse offspring

2. Sex lives

   • Only reproduce when colony is mature
   • Annual life cycle-- Honey bees- Death of queen
     • Pheromonal control of workers is gone-- ovaries start to develop and produce eggs
     • Many males produced
     • Reproductives produced all at once and leave the colony
   • Perrenial life cycle
     • ants, termites, stingless bees and some wasps
     • Same as annual life cycle but queens don't die-- overwinter in colony then carry on the next year
     • Queen dies- colony ceases
   • Swarms
     • Gene flow across the pop
     • Mated queens disperse to find new colonies
   • Different mating strategies
     • Honeybees
       • Male-biased mating swarms
       • Explosive- fatal ejaculation by males
       • Colony is too large- reproduction by fission-- Queen leaves
         • New queen mates with between 8 and 20 males outside nest
         • Old Queen leaves and forms new colony
         • Half workers stay in colony and raise new queen
     • Calling in ants
     • Male territories
       • scent marking
       • Bumble bees
   • Mate for life!!- No repeats

3. Why polyandry?

   • For sperm
     • More sperm= more offspring
     • Queens only store the equivalent of one male's worth of semen
     • Sperm dumped after mating flight
     • There would be selection for males with more sperm
   • Expensive
     • Energy
     • Predation
     • STi's
   • Convenience
     • Avoid confrontations
     • Females have control over when to go on mating flights and produce pheromones
   • Nuptial gifts
     • No evidence that ejaculates provide significant nutrients- can reduce female receptivity to further mating
     • No nuptial gifts
   • Genetic indirect benefits
     • Dilute incompatibility
       • Occurs during inbreeding
       • Sex-locus load in hymenoptera-- due to haplodiploidy-- female mates with male with whom she shares alleles-- and the alleles are homozygous at the matching alleles then fertilised eggs can become diploid sterile workers instead of workers
       • polyandry reduces proportion of non-viable offspring
       • Improved brood viability-- more winter survival
     • Increase with-in colony genetic diversity
       • Pogonomyrmex harvester ants-- relatedness negatively correlated with colony growth rate
       • Ants imroved allotheism
       • Increased honeybee genetic diversity across whole colony
         • Greater foraging activity
         • Greater weight gain
         • Greater brood production
         • Better nectar exploiters
     • Increase genetic diversity to improve disease resistance
       • Genetic variance in resistance to parasites shown in (different in in different patralines)
         • Bumblebees
         • Honey bees
         • Acromyrmex
       • Improved colony resistance to disease with increased genetic diversity
         • Bumblebees
         • Honey- bees
         • Leaf-cutting ants
         • Wood ants
       • Evolving to overcome the defences of a genetically similar range of hosts-- easier than that of a genetically diverse
         • Acromyrmex-- parasite fitness was higher in full siblings than half- siblings ect..

4. Weird sex

   • Sexual conflict- males don't want females to remate
     • Honeybees leave genitalia in female reproductive tract
     • Dinosaur ants- leave whole end of abdomen in female
     • Mating plugs
   • Assexual reproduction
     • females produced asexually
     • Cape honey bee- un-mated offspring can produce female offspring-
       • also in 5 species of ant
       • Clonally produced honey bees revert to sexual reproduction within a single generation
     • Produce new queens assexually
       • Prevent genome of mate from being transferred-- all own genes passed on
       • Workers produced sexually--- worker pop genetically diverse