evolutionary ecology. evidence of local adaptation
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Evolutionary Ecology
Evidence of local adaptation
Environmental or Genetic Variation in WesternYarrow?
Creeping Bent Grass - Agrostis stolonifera
Adaptation in Trinidad GuppiesPoecilia reticulata
Two males
Male and Female
Adaptation and natural selection in guppy populations
John Endler
Cline – Bergmann’s Rule
Bergmann’s Rule in BearsSun bear, Spectacled bear, Brown bear, Polar bear
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;44:413-424The Society for Integrative and Comparative Biology
Cline – Allen’s Rule
Arctic Cool Temperate Warm Temperate Desert
White clover – Trifolium repens
Cline incyanideproductionby whiteclover –dark circle populations withcyanide;white circle lack cyanide
Clinal variation in gulls
Herring Gull Lesser Black-backed Gull
What is a species?
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
Rubus - Blackberries
Biological Species Concept
Comte de Buffon Ernst Mayr
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
Species which look almost identical morphologically but which do not interbreed.
Drosophila pseudoobscura
Gilia angelensis
Gilia tricolor
Polytypic species
• Species made up of populations which differ morphologically but which will interbreed in nature.
Variation in Song Sparrows
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
• 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.
Western and Florida Scrub Jay
Speciation
• 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.
Allopatric Speciation – Galapagos Islands Finches
Darwin’sFinches
Sympatric and Allopatric Speciation – Picture Winged Drosophila
EightSpecies ofPicture-WingedDrosophila
Founder Events with Picture Winged Drosophila
Sympatric Speciation in Cichlids
Variation in Lake Malawi and Lake Tanganyika Cichlids
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
Spartina alterniflora marsh – North Carolina
Spartinaalterniflora
Spartinamaritima
Spartina x townsendii
Spartinaanglica
Spartina anglica – invasive in New Zealand