Speciation

Species

Taxonomy - mostly focus on ways for cataloguing and information retrieval Phylogeny - definition mostly relates to relationships and history Evolutionary biology - focuses on the evolutionary process

Hierarchical system: kingdom, phylum, class, order, family, genus and species

Phenetic method (according to observable attributes) • Describe the phenotype of the holotype and deposit specimen into a museum • Other researchers compare their species to the holotype

• Lead to organisms being occasionally described as being part of a different species when they are actually different populations connected by continuous variation or have phenotyhpic polymorphisms • How much variation is ‘allowed’ within a species

Species are populations which are reproductively isolated

• Reproductive isolation • Stabilised, well-integrated genotype • Species-specific niche

• Make species as biological reality and not a taxonomists opinion • Measurable and testable • Can study speciation through reproductive isolation

• How to define asexual species • How to study and classify species from fossils • Is reproductive isolation completely necessary?

Smallest aggregate population/lineage which can be united by synapomorphic characters (shared derived characters)

Fossils and asexual organisms

• pre-mating mechanisms which prevent the formation of hybrid zygotes by impeding gene flow before sperm/pollen transfer • post-mating mechanisms can be pre-zygotic or post-zygotic

• Behavioural isolation • Ecological isolation • Mechanical isolation • Mating system isolation

Differences which result in a lack of cross-attraction between species (does strong sexual selection result in speciation?)

• Habitat isolation -> when species have a tendency to occupy different habitats in a general area resulting in a lack of gene transfer • Temporal isolation -> different breeding times • Pollinator isolation -> gene flow between angiosperms is reduced due to their different interactions with pollinators

• Have developed different life cycle lengths (11, 13, 17 & 19 years) to avoid predator satiation which has separated them from ancestors • Different mating calls to differentiate different cicadas with the same length lifecycle

Closely related Mimulus species have different pollinator vectors due to different shapes which mostly seems to be controlled by a single gene

• Copulatory mating isolation -> where individual behaviour during copulation does not allow for normal fertilisation • Gametic isolation

Noncompetitive - Intrinsic problems with transfer/storage/fertilisations of heterospecific gametes in single fertilisations between individuals Competitive - Heterospecific gametes are not properly transferred/stored when competing with gametes of the same species

• Extrinsic factors - hybrids cannot adapt to ecological niche or cannot obtain mates as intermediate characteristics are unattractive • Intrinsic factors - could be hybrid inviability where difficulties cause full/partial lethality or hybrid sterility due to physiological (gametes/reproductive development) or behavioural (neurological lesions) factors

A change in the number of chromosomes

autoploidy - duplicating of own chromosome allopolyploidy - chromosome doubling of a hybrid

Through negative interactions between genes evolving independently of eachother

When in the F1 offspring of two different animal races one sex is absent, rare or sterile, it is the heterozygous sex