Speciation
Speciation
An evolutionary process by which a new biological species (population member that actually or potentially interbreed in nature not according to similarity of appearance (Paleontology, n.d.) arise
There are four geographic modes of speciation in nature based on the extent by which they are isolated from each other, in addition speciation can occur artificially through animal husbandry, agriculture, or laboratory experiments.
The four geographic modes:
Allopatric:
This form of speciation takes place when a population splits in to two geographically isolated populations, preventing genetic interchange. For example habitat fragmentation caused by mountain building (movement of the earth’s crust), population dispersal, island formation, human activity, the two populations undergo a number of possible changes, (Ridely, 1986)
Peripatric:
This is a sub form of the above allopatric speciation, it is where new species are formed in isolated, but peripheral populations (seen in image), meaning there rages are close together but never overlap, this form of speciation is similar to the allopatric speciation as the two populations are isolated but one breaks off and forms a much smaller group, and over time forms different characteristics much different from its origin group (example can be seen in image how different the skull of the two species of bear are) a well-documented example of this is the Polar bear through evolution this living species gave rise to that of the Brown bear. (Society., 1996)
Sympatric: In this mode the reduction in gene flow does not require any large scale distance between parts of the population.
An example of this could be exploiting a new niche some herbivorous insects could try out a new host plant and others could carry on exploiting the old plant, example of this is the apple maggot fly (Rhagoletis pomonella), (see image ) their ancestors laid their eggs on only the hawthorn plant, however today they lay their eggs on not only the hawthorn plan but on the domestic apples. The females insects will lay their eggs in the plants they grew up in either the hawthorn or the apple and the males will look for a suitable mate in the plats they grew up in either hawthorn or apple, so the hawthorn fly’s mate with other hawthorn fly and the same for the apple fly’s, meaning that gene flow between parts of the population that mate on different types of fruit is reduced (Home, n.d.), this type of speciation seems to be limited to phytophagious and zoophagiousparasites, as they exploit a genetically controlled habitat and host selection mechanism that could be subject to change, additionally this mode along with many insects displaying behavioural preference for habitat and host has played a major role in the development of insect diversity.
Evaluation
In this mode as with the others there are advantages and disadvantages for the species involved, it could open up new opportunities for the species to expand their territory and species and as their food supply has changed so more hosts could potentially be infected/ utilised, an increase in available food mean a population boom, however once the split is made each of the two groups will develop differently in their behaviour, food preference, ect and over time this will, through the process of evolution make them two distinctly different species/ sub species.
An evolutionary process by which a new biological species (population member that actually or potentially interbreed in nature not according to similarity of appearance (Paleontology, n.d.) arise
There are four geographic modes of speciation in nature based on the extent by which they are isolated from each other, in addition speciation can occur artificially through animal husbandry, agriculture, or laboratory experiments.
The four geographic modes:
- Allopatric
- Peripatric
- Parapatric
- Sympatric
Allopatric:
This form of speciation takes place when a population splits in to two geographically isolated populations, preventing genetic interchange. For example habitat fragmentation caused by mountain building (movement of the earth’s crust), population dispersal, island formation, human activity, the two populations undergo a number of possible changes, (Ridely, 1986)
- Genotypic or Phenotypic, as they both get
subjected to different selective pressures
- They could independently undergo genetic drift,
(one basis for evolution discussed on another page)
- Some different mutations arise in the population
gene pool (discussed on different page) (Ridely, 1986)
Peripatric:
This is a sub form of the above allopatric speciation, it is where new species are formed in isolated, but peripheral populations (seen in image), meaning there rages are close together but never overlap, this form of speciation is similar to the allopatric speciation as the two populations are isolated but one breaks off and forms a much smaller group, and over time forms different characteristics much different from its origin group (example can be seen in image how different the skull of the two species of bear are) a well-documented example of this is the Polar bear through evolution this living species gave rise to that of the Brown bear. (Society., 1996)
Sympatric: In this mode the reduction in gene flow does not require any large scale distance between parts of the population.
An example of this could be exploiting a new niche some herbivorous insects could try out a new host plant and others could carry on exploiting the old plant, example of this is the apple maggot fly (Rhagoletis pomonella), (see image ) their ancestors laid their eggs on only the hawthorn plant, however today they lay their eggs on not only the hawthorn plan but on the domestic apples. The females insects will lay their eggs in the plants they grew up in either the hawthorn or the apple and the males will look for a suitable mate in the plats they grew up in either hawthorn or apple, so the hawthorn fly’s mate with other hawthorn fly and the same for the apple fly’s, meaning that gene flow between parts of the population that mate on different types of fruit is reduced (Home, n.d.), this type of speciation seems to be limited to phytophagious and zoophagiousparasites, as they exploit a genetically controlled habitat and host selection mechanism that could be subject to change, additionally this mode along with many insects displaying behavioural preference for habitat and host has played a major role in the development of insect diversity.
Evaluation
In this mode as with the others there are advantages and disadvantages for the species involved, it could open up new opportunities for the species to expand their territory and species and as their food supply has changed so more hosts could potentially be infected/ utilised, an increase in available food mean a population boom, however once the split is made each of the two groups will develop differently in their behaviour, food preference, ect and over time this will, through the process of evolution make them two distinctly different species/ sub species.