lecture 18 – speciation/species- origin of species.Speciationis the process that produces new species from an ancestor speciesSpeciationis invoked to explain the diversity of types of organismsWhat is a species?oTwo general possibilitiesSpecies are truly distinct real entities, orThe ‘species’ is an idea we have imposed on natureo(Or something in between, or either, depending upon the situation?)oDefinition: “An evolutionarily independent population or group of populationsSpeciation- a process under most models, species are not creatd instantly but over long periods of timeTwo patterns: (lecture 18 slide 6 for example)oPhyletic speciation àAnagenesisoPhylogenetic speciation àCladogenesisIf microevolution occurs in two halves of a gene pool that has split then we have speciationSpeciation:oRemember that we are occupying a “point in time” àspecies can be in fluxoAnd remember that current “species” are not fixed genetically àSpecies have variability and natural selection operates all the timeoSo it’s difficult to draw boundaries around “species”*understanding the forkspecies characteristics are dynamic, changing over time, but its label is that its character is fixedWe consider morphology (body form) as well as physiology (internal functions), biochemistry, DNA, geography, and behaviourBiological Species Conceptinvolving reproductive isolation “Populations whose members have the potential to interbreed in nature to produce viableand fertileoffspring”“Reproductive compatibility” within species“Reproductive isolation” between speciesono gene flow between breeding groupsoCan lead to speciation, provided isolation is sufficiently long-lastingoCan then maintain separate gene pools as separate speciesoFor sexually reproducing speciesoPre and Post zygotic Barriers:Serve to reproductively isolate a population from other gene pools, Create and maintain speciesPre-zygotic: :before the zygote” Reproductive isolation prior, Impede mating or prevent fertilization
A) those that prevent mating –1. habitat isolation (“ecological isolation”) ex. Desert sping lizard (open areas), clarks spiny lizard (trees)2. Geographic isolation ex. Tucuxi Dolphins (pronounced (too-koo-shee) have separate marine and riverine gene pools3. Temporal isolation ex. Eastern Spotted Skunk and Western Spotted Skunk overlap geographically, but one species mates in winter and the other in summer. Another example (day vs night)4. Behavioural isolation: ex, In Blue-footed Boobies, there is a scripted courtship that involves foot waving, and it secures the reproductive attention only of other Blue-footed Boobies5. Mechanical islolation ex,Damselflies and Dragonflies have highly complex genitalia that work like lock and key and that vary considerably between otherwise closely related species.