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