Reproductive Isolation Flashcards
how is inbreeding prevented?
reproductive isolating mechanisms - a property of two species that stops them from interbreeding
what was Dobzhankys classification of isolating mechs?
pre-mating or pre-zygotic mechs that prevent the formation of hybrid zygotes
impede gene flow before transfer of sperm/pollen
what are post-mating mechs that impede gene flow?
post-zygotic - after fertilisation of zygote
pre-zygotic - after sperm/pollen transfer but before fertilisation
what is behavioural isolation?
speciation that is an incidental by-product of sexual selection - eg anole lizards with different dulaps under chin
some reasons cicadas have 11, 13 etc year cycles?
predator satiation
temporal/spatial isolation - new species benefits from increased density when co-emerging
changed calling song and shows assortative mating - shows the types of isolation
what is pollinator isolation?
when closely related species differ in pollination vector - controlled by few genes
possible that either single genes with large effect or linked cluster of genes with large effect
what is mechanical isolation?
when mating structures differ so that mating is not possible
lock and key vs post-mating comp between males
insect genitalia prevents allied species from producing bastards by adulterous connexions - hard part of male correspond so exactly with females that the organs of one species can’t fit the other
what is conspecific sperm precedence?
when a female mates two males in close succession
female flowers elaborate - potential for female flowers to influence reproduction
what is hybrid sterility?
two members of different species mate and the offspring is sterile
what were the conflicting views on hybrid sterility?
darwin - thought sterility would protect the integrity of the species
muller - thought negative interactions between genes which evolved independently of each other
what is polyploidy?
when there is a change in the number of sets of chromosomes - common in plants
what is autopolyploidy?
fusion of gametes from same parent - self
what is allopolyploidy?
when reproductively isolated from parents - crosses produce sterile hybrids due to chromosome imbalance
can originate more than once - common method of plant speciation
what is homoploid hybrid speciation?
production of a fertile homoploid hybrid species with same chromosome no. as parents
originates when recombinant that segragates from the initial hybrid is reproductively isolated from its parent species by chromosomal barrier or ecological barrier
