Speciation Genes

Abstract

Even though there is no universal criterion for species definition, the key event in speciation research is the advent of reproductive isolation or barriers that prevent gene flow between populations. The search for genetic factors underlying isolating barriers is the field of speciation genetics. The development of sophisticated methods of genetic analysis coupled with statistical advances allowed a finer dissection of the genetic factors underlying the origins of species down to the level of the individual loci and even at the deoxyribonucleic acid (DNA) ‐sequence level. Traditionally, speciation geneticists concentrated, almost exclusively, on genes causing hybrid incompatibilities (especially intrinsic postzygotic barriers). However, barriers to gene flow caused by speciation genes can arise at multiple prezygotic and postzygotic life‐history stages. Thus, a general definition of speciation genes should refer to those genes that contributed to the splitting of two lineages by reducing the amount of gene flow between them. Key Concepts: The evolution of barriers to genetic exchange between groups is the crucial event for the origin of new sexually reproducing species. Barriers to gene flow can be divided in two main categories: (i) prezygotic that preclude the formation of hybrid offspring and (ii) postzygotic that later prevent the success and propagation of hybrid offspring. The identification and characterisation of genes that contribute to the interruption of gene flow between populations is currently one of the main focuses in the field of speciation. Speciation genes are the genes that contributed to the splitting of two lineages by reducing the amount of gene flow between them. The most solid evidence that a gene causes reproductive isolation combines fine mapping studies with genetic manipulation experiments (such as positional cloning, gene replacement or knockout, gene expression assays and transgenic manipulations). Alleles underlying hybrid incompatibilities between species may arise by neutral or nearly neutral processes or may be a direct consequence of positive selection or a byproduct of adaptive evolution.

Post-zygotic sterility and cytonuclear compatibility limits in S. cerevisiae xenomitochondrial cybrids

“…Generally the post-zygotic barrier of speciation resulting in hybrid inviability and hybrid sterility has been attributed to a large number of genomic regions across a wide variety of species (for reviews Maheshwari and Barbash, 2011 ; Nosil and Schluter, 2011 ; Butlin et al, 2012 ; Mensch et al, 2013 ). In higher eukaryotes most of them involve chromosomal rearrangements and incompatibilities in nuclear Dobzhansky–Muller gene pairs (Maheshwari and Barbash, 2011 ).…”