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Wallabies Rock the Basis of Speciation

Credit: Henry Cook

Credit: Henry Cook

By Sally Potter & Mark Eldridge

Six rock-wallaby species in Queensland have different numbers of chromosomes, yet gene flow somehow occurs between them. What does this tell us about how new species form?

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Six closely related species of rock-wallaby from north-east Queensland have long been considered a classic example of chromosomal speciation. Each of these species is similar in almost every way, yet each differs in the shape and number of their chromosomes.

These chromosome differences should make gene flow between these species almost impossible, since hybrids would have reduced fertility due to their chromosome differences.

However, contrary to expectations, we have found no relationship between the degree of chromosome differences and the amount of gene flow among these species. For example, we found relatively high levels of gene flow between some species that differ by multiple chromosome changes, and alternatively we found low gene flow between species with similar chromosomes.

This indicates that the mechanisms driving species formation are much more complex than just the incompatibilities caused by chromosome rearrangements. It appears then that complex interactions between the way genetic material is packaged into chromosomes and how the chromosomes differ in their shape, number and arrangement is driving species formation.

Chromosomes are the long molecules of deoxyribonucleic acid (DNA) found in each cell that contain all the genetic information each organism requires to function. For example, each human cell contains about 2...

The full text of this article can be purchased from Informit.