Plant evolution

Differences between plant and animal physiology and reproduction cause minor differences in how they evolve.

One major difference is the totipotent nature of plant cells, allowing them to reproduce asexually much more easily than most animals. They are also capable of polyploidy – where more than two chromosome sets are inherited from the parents. This allows relatively fast bursts of evolution to occur, for example by the effect of gene duplication. The long periods of dormancy that seed plants can employ also makes them less vulnerable to extinction, as they can "sit out" the tough periods and wait until more clement times to leap back to life.[1]

The effect of these differences is most profoundly seen during extinction events. These events, which wiped out between 6 and 62% of terrestrial animal families, had "negligible" effect on plant families.[2] However, the ecosystem structure is significantly rearranged, with the abundances and distributions of different groups of plants changing profoundly.[2] These effects are perhaps due to the higher diversity within families, as extinction – which was common at the species level – was very selective. For example, wind-pollinated species survived better than insect-pollinated taxa, and specialised species generally lost out.[2] In general, the surviving taxa were rare before the extinction, suggesting that they were generalists who were poor competitors when times were easy, but prospered when specialised groups became extinct and left ecological niches vacant.[2]

During embryogenesis, plants and animals pass through a phylotypic stage that evolved independently[3] and that causes a developmental constraint limiting morphological diversification.[4][5][6][7]

Speciation via polyploidy: A diploid cell undergoes failed meiosis, producing diploid gametes, which self-fertilize to produce a tetraploid zygote.

Polyploidy is pervasive in plants and some estimates suggest that 30–80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy (paleopolyploidy) in their genomes.[8][9][10] Huge explosions in angiosperm species diversity appear to have coincided with ancient genome duplications shared by many species.[11] 15% of angiosperm and 31% of fern speciation events are accompanied by ploidy increase.[12] Most polyploids display heterosis relative to their parental species, and may display novel variation or morphologies that may contribute to the processes of speciation and eco-niche exploitation.[9][13] The mechanisms leading to novel variation in newly formed allopolyploids may include gene dosage effects (resulting from more numerous copies of genome content), the reunion of divergent gene regulatory hierarchies, chromosomal rearrangements, and epigenetic remodeling, all of which affect gene content and/or expression levels.[14][15][16] Many of these rapid changes may contribute to reproductive isolation and speciation.

All eukaryotes probably have experienced a polyploidy event at some point in their evolutionary history. See paleopolyploidy. In many cases, these events can be inferred only through comparing sequenced genomes. Angiosperms have paleopolyploidy in their ancestry. Unexpected ancient genome duplications have recently been confirmed in mustard weed/thale cress (Arabidopsis thaliana) and rice (Oryza sativa).

Transcription factors and transcriptional regulatory networks play key roles in plant development and stress responses, as well as their evolution. During plant landing, many novel transcription factor families emerged and are preferentially wired into the networks of multicellular development, reproduction, and organ development, contributing to more complex morphogenesis of land plants.[21]

• Evolutionary history of plants
• Annual vs. perennial plant evolution

• Evolution And Paleobotany at Britannica