Speciation: Chromosomal Mechanisms

Abstract

Abstract Chromosomal speciation is one of the major modes of the origin of new species through the splitting of preexisting species. New species may originate by gene speciation, and also by the establishment of post‐mating reproductive isolation through structural chromosome rearrangements. The latter may induce low‐hybrid fitness, generated by macromutations, and even by micromutations, that is, molecular changes causing meiotic disturbances (e.g. GC incompatibilities), although the latter awaits empirical support. Criticism against the traditional model of chromosomal speciation led to renewed theoretical models arguing that chromosomal rearrangements can generate reproductive isolation between species by suppressing recombination within rearranged regions. Reduced recombination permits the accumulation of alleles contributing to reproductive isolation and adaptive divergence and radiation. Likewise, coding and noncoding genomes, and novel chromosomal breakpoint regions can generate novel combinations of genes and regulatory elements that contribute to both adaptive radiation and ecological speciation. Chromosomal speciation is certainly an important speciation mode across life, although we cannot yet quantify it in relation to other modes. The spalacid example of blind subterranean mole rats in the East Mediterranean is presented as a widely studied case of chromosomal ecological speciation. The proportion of chromosomal speciation in nature, particularly in animals, remains a future challenge. Key Concepts: Speciation – the evolutionary process leading to the multiplication of species and generating biodiversity. Chromosomal speciation – the theory asserting that chromosomal rearrangements cause reproductive isolation between populations and lead to speciation. Peripatric speciation – the origin of a new species by budding from a parental species established beyond the periphery of the parental species range. Sympatric speciation – speciation without geographic (spatial) isolation; the origin of a new species within a deme. Polyploidy – the condition in which the number of chromosomes is an integral greater than two of the haploid numbers. Biological species concept (BSC) – defines species as groups of interbreeding natural populations that are reproductively (genetically) isolated from other such groups. Allopatric speciation – the evolution of a population into a separate species involving a period of geographic isolation. The evolutionary divergence of a single phyletic line into different niches or adaptive zones.