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Palaeobiology

Allopatric

Where a population or species occupies a different geographic region to another population or species. See also sympatric and parapatric.

 

Allopatric Speciation

Where different populations are formed, without intermediates, if physical barriers restrict gene flow. There are two types: vicariant speciation and peripatric speciation.

 

Allopolyploidy

Chromosomes donated from >1 parental species. See also polyploidy and autopolyploidy.

 

Anagenesis

The process by which evolutionary change along a single lineage creates a new species without any splitting of the phylogenetic tree (see cladogenesis).

 

Autopolyploidy

Chromosomes donated from one parental species. See also polyploidy and allopolyploidy.

Autozygous

When an individual possess’ two copies of the same allele that are identical by descent (see inbreeding coefficient).

 

Biological species concept

Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups. See also morphospecies concept and phylogenetic species concept.

 

Cast

The infill of a fossil mould.

 

Cladogenesis

The evolution of two or more daughter species from a single parent species by the splitting of a lineage.

Directional selection

Fitness increases/decreases with trait magnitude. E.g. selection on bill size in Darwin’s medium ground finch – Geospiza fortis. Population crashes in 1977, 1980 and 1982, due to droughts, selected for increased bill depth due to abundance of hard seeds of Tribulus cistoides. Deep beaks are needed to crack these seeds and therefore large bills were selected for.

 

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