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Evolutionary Ecology. Evidence of local adaptation. Environmental or Genetic Variation in WesternYarrow?. Creeping Bent Grass - Agrostis stolonifera. Adaptation in Trinidad Guppies Poecilia reticulata. Male and Female. Two males. Adaptation and natural selection in guppy populations.

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Fig. 3. Mean ± SE body size (top) and egg to adult development time (bottom) as a function of latitude for lab-reared families of yellow dung fly males and females from six different latitudinal populations in Europe, at 15°C in the sequential experiment (CH: Switzerland; GB: England; D: Germany; S: Sweden; ISL: Iceland).

Blanckenhorn W U , and Demont M Integr. Comp. Biol. 2004;44:413-424

The Society for Integrative and Comparative Biology

cline allen s rule
Cline – Allen’s Rule

Arctic Cool Temperate Warm Temperate Desert


Cline in



by white

clover –

dark circle populations with


white circle lack cyanide

clinal variation in gulls
Clinal variation in gulls

Herring Gull

Lesser Black-backed Gull

morphological species concept
Morphological species concept:
  • Assemblages of individuals with morphological features in common and separable from other such assemblages by correlated morphological discontinuities in a number of features.

from Davis and Heywood

biological species concept
Biological Species Concept

Comte de Buffon Ernst Mayr

biological species concept22
Biological species concept

A species consists of a groups of organisms which can sexually interbreed or at least have the potential to sexually interbreed (if geographically isolated) that are reproductively isolated from other such groups.

This is based on two criteria:

1. do populations from the same locality normally interbreed?

2. if cross-fertilization does occur, are the hybrids viable and fertile?

sibling species
Sibling species

Species which look almost identical morphologically but which do not interbreed.

Drosophila pseudoobscura


Gilia tricolor

Gilia angelensis

polytypic species
Polytypic species
  • Species made up of populations which differ morphologically but which will interbreed in nature.
potential problems with biological species concept
Potential problems with biological species concept
  • Fossil species cannot be tested for reproductive isolation
  • Asexual species also cannot be test for reproductive isolation – each clone is genetically separate from all others – Mayr calls asexual species ‘paraspecies’
phylogenetic species concept
Phylogenetic species concept
  • Species are defined based upon branching patterns in phylogenetic trees. Species are also defined based upon differences in evolutionary history. Species typically diverge when reproductively and/or geographically isolated.
  • Speciation is the formation of new species.
  • Allopatric speciation - formation of new species occurs when populations of a species become geographically separated from each other and diverge so that when they co-occur they cannot interbreed.
  • Sympatric speciation - occurs when reproductive isolation occurs within the range of a population before any differentiation of the two species can be detected.





Species of




polyploidy in spartina cordgrasses
Polyploidy in Spartina cordgrasses
  • Polyploidy - an increase in the number of chromosomes beyond the typical diploid number - may be a doubling or greater - this happens most often in plants
  • Polyploidy often occurs following the production of hybrids