Speciation: A new role for reinforcement Smadja C, Butlin R. Speciation: A new role for reinforcement. Heredity. 2006 Jun; 96 (6): 422-3. Speciation-A new role for reinforcement Plant speciation Rieseberg LH, Willis JH. Plant speciation. Science. 2007 Aug 17; 317 (5840): 910-4. Like the formation of animal species, plant speciation is characterized by the evolution of barriers to genetic exchange between previously interbreeding populations. Prezygotic barriers, which impede mating or fertilization between species, typically contribute more to total reproductive isolation in plants than do postzygotic barriers, in which hybrid offspring are selected against. Adaptive divergence in response to ecological factors such as pollinators and habitat commonly drives the evolution of prezygotic barriers, but the evolutionary forces responsible for the development of intrinsic postzygotic barriers are virtually unknown and frequently result in polymorphism of incompatibility factors within species. Polyploid speciation, in which the entire genome is duplicated, is particularly frequent in plants, perhaps because polyploid plants often exhibit ecological differentiation, local dispersal, high fecundity, perennial life history, and self-fertilization or asexual reproduction. Finally, species richness in plants is correlated with many biological and geohistorical factors, most of which increase ecological opportunities. Plant speciation The nature of plant species Rieseberg LH, Wood TE, Baack EJ. The nature of plant species. Nature. 2006 Mar 23; 440 (7083): 524-7. Many botanists doubt the existence of plant species, viewing them as arbitrary constructs of the human mind, as opposed to discrete, objective entities that represent reproductively independent lineages or 'units of evolution'. However, the discreteness of plant species and their correspondence with reproductive communities have not been tested quantitatively, allowing zoologists to argue that botanists have been overly influenced by a few 'botanical horror stories', such as dandelions, blackberries and oaks. Here we analyse phenetic and/or crossing relationships in over 400 genera of plants and animals. We show that although discrete phenotypic clusters exist in most genera ( 80%), the correspondence of taxonomic species to these clusters is poor ( 60%) and no different between plants and animals. Lack of congruence is caused by polyploidy, asexual reproduction and over-differentiation by taxonomists, but not by contemporary hybridization. Nonetheless, crossability data indicate that 70% of taxonomic species and 75% of phenotypic clusters in plants correspond to reproductively independent lineages (as measured by postmating isolation), and thus represent biologically real entities. Contrary to conventional wisdom, plant species are more likely than animal species to represent reproductively independent lineages. The nature of plant species There shall be order. The legacy of Linnaeus in the age of molecular biology Paterlini M. There shall be order. The legacy of Linnaeus in the age of molecular biology. EMBO Rep. 2007 Sep; 8 (9): 814-6. There shall be order DNA barcodes: recent successes and future prospects Dasmahapatra KK, Mallet J. DNA barcodes: recent successes and future prospects. Heredity. 2006 Oct; 97 (4): 254-5. Epub 2006 Jun 21. DNA barcodes-recent successes and future prospects The molecular genetics of crop domestication Doebley JF, Gaut BS, Smith BD. The molecular genetics of crop domestication. Cell. 2006 Dec 29; 127 (7): 1309-21. Ten thousand years ago human societies around the globe began to transition from hunting and gathering to agriculture. By 4000 years ago, ancient peoples had completed the domestication of all major crop species upon which human survival is dependent, including rice, wheat, and maize. Recent research has begun to reveal the genes responsible for this agricultural revolution. The list of genes to date tentatively suggests that diverse plant developmental pathways were the targets of Neolithic genetic tinkering, and we are now closer to understanding how plant development was redirected to meet the needs of a hungry world. The molecular genetics of crop domestication
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