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BELL CURVE IN SPECIATION. "Darwin already noted that there is an evolutionary continuum between varieties and species. This implies that taxa described as varieties (or subspecies) should be groups of individuals that possess evolutionary relevant properties distinguishing them consistently from other members of the species." https://lnkd.in/dK-A3iM View in LinkedIn

INTERMEDIATE VERSUS PARENTAL. "While intermediacy is often the expected state in hybrids, it has been shown when averaging over several studies that only about half of the characters in hybrids for interspecific crosses were intermediate, with other characters approaching the morphology of one of the parents." https://lnkd.in/dK-A3iM View in LinkedIn

INTERMEDIATE PHENOTYPES. "Other qualitative characters, on the other hand, either tended towards the morphology seen in one of the parents (stamen hairs were mostly present in the intermediates, as in R. irroratum; ovary glands were consistently absent, as in R. delavayi or showed a combination of intermediate and parental characters (styles were either hairy, or glandular and hairy; and ovaries were either hairy, intermediate, or densely hairy." https://lnkd.in/dK-A3iM View in LinkedIn

STRONG PHENOTYPE DIFFERENCES. "Several characters were identified that could distinguish between the species. The quantitative characters that showed high discrimination potential ‘flowers in inflorescence’, ‘stigma width’, ‘corolla (width/length)’ and also ‘leaf (dist apex-mid/length)’, tended towards intermediate values for the hybrids. As quantitative characters are generally considered to be under polygenic control, this can be expected." https://lnkd.in/dK-A3iM View in LinkedIn

GENEROUS DELTA. "Apart from a few exceptions, the variances of repeated measurements for individuals of the same group were significantly different from each other." https://lnkd.in/dK-A3iM View in LinkedIn

TRAITS VERSUS CONSENSUS. "The morphological characters ‘stamen hairs’ and ‘style hair-coverage’ were then tested for correlation with the above calculated hybrid index." https://lnkd.in/dK-A3iM View in LinkedIn

ACCUMULATED MUTATIONS. "However, in most cases, the gradual accumulation of deleterious mutations during growth is more likely to negatively influence fitness because these mutations can be potentially transmitted from shoot meristems to gametes when flowering occurs. As long as somatic mutations do not limit clonal growth, they should accumulate over the life span of genets." http://www.pnas.org/content/112/29/8859.full View in LinkedIn

HETEROSTYLY AND COMPATIBILITY. “The lengths of stamens and pistils in heterostylous flowers are adapted for pollination by different pollinators, or different body parts of the same pollinator. Thus, pollen originating in a long stamen will reach primarily long rather than short pistils, and vice versa. When pollen is transferred between two flowers of the same morph, no fertilization will take place, because of the self-incompatibility mechanism.” https://en.m.wikipedia.org/wiki/Heterostyly View in LinkedIn

BENEFICIAL MOSAICS. "The great size and longevity of many trees and clonal plants is predicted to be associated with the accumulation of numerous somatic mutations in cell lineages. Some have argued for the adaptive benefits of this type of variation because of the formation of genetic mosaics and their role in plant defense." http://www.pnas.org/content/112/29/8859.full View in LinkedIn

SO ENDS this first weekend contemplation of plant hybrids. Historical reversals of plant species assignments have not been rare, and the case study of the rampantly hybrid species rhododendron through an exhaustive study of traits illustrate how slippery the assignments can be. This is further confounded by transgressive segregation which is the formation of extreme phenotypes when compared to the parental lines, making the hybrid resemble a new species. https://lnkd.in/ddar4m9 View in LinkedIn