ארכיון יומן של אפריל 2021

אפריל 26, 2021

VARIATION OF SEPAL TRAITS IN STELLARIA PUBERA

Stellaria pubera and Stellaria corei

Present taxonomy would place a Stellaria pubera with:
(1) sepals as-long-as or longer than the petals; and
(2) sepals whose underside/abaxial surface is smooth/bald/glabrous
as Stellaria corei, originally described as a subspecies of Stellaria pubera.

However, it is apparent (see iNat observations below) that individuals of Stellaria pubera can have:
1) long pubescent sepals
2) long glabrous sepals
3) short pubescent sepals
4) short glabrous sepals

How can this be?

  • Stellaria corei is a tetraploid (4n) version of the diploid (2n) Stellaria pubera. Stellaria corei likely originated when an error in meiosis resulted in un-reduced gametes [the pollen and egg were not haploid (1n) as usual, but were instead diploid (2n), and when combined (fertilization) resulted in a tetraploid (4n) individual. This sort of thing is common in the cactus genus Opuntia.]
  • Stellaria corei (4n) can interbreed with Stellaria pubera (2n) and produce viable offspring (3n). The offspring will be sterile due to their triploid (3n) genetic composition. The triploid plants can, however, reproduce vegetatively (by rooting at stem nodes, root division, et cetera).
  • The triploid hybrids (Stellaria corei x pubera & Stellari puberi x corei) will present a mixture of traits of the parents, and be difficult or impossible to visually separate - until such time as an in-depth study is conducted across the breadth of the distribution of both species, and hybrids, that includes documentation of physical traits combined with genetic analyses. Only in this way will convincing knowledge be produced to determine whether any physical traits can definitively (statistically significant) be used to separate the species, and the hybrids from the species.
That being said, only 1 observation has been found (as of 23 May 2021) of a Stellaria pubera with pubescent sepals that are longer than the flower petals [this may be a triploid]. I therefore tentatively suggest that
  • combined traits of (1) truly glabrous sepals that are (2) longer than the petals can reliably be attributed to Stellaria corei
  • combined traits of (1) definitively pubescent sepals that are (2) shorter than the flower petals can reliably be attributed to Stellaria pubera
  • Triploid intermediates are expected to exhibit (1) a range of degree of sepal glabrousness and pubescence and (2) a range of sepal length (shorter-than or longer-than the flower petals). When the plant is neither emphatically glabrous, or emphatically pubescent then it may not be far off the mark to consider it a triploid.

What to do with the triploids? A situation that perplexes current taxonomy.

Below are iNaturalist observations of Stellaria pubera

1) Pubescent and Short Sepals
https://www.inaturalist.org/observations/75730401 pubescent short sepals
https://www.inaturalist.org/observations/75581210 pubescent short sepals
https://www.inaturalist.org/observations/75501455 pubescent short sepals
https://www.inaturalist.org/observations/75367119 pubescent short sepals

2) Glabrous and Short Sepals
https://www.inaturalist.org/observations/75620153 glabrous short sepals
https://www.inaturalist.org/observations/75432600 glabrous short sepals
https://www.inaturalist.org/observations/75309895 glabrous short sepals
https://www.inaturalist.org/observations/75367619 glabrous short sepals
https://www.inaturalist.org/observations/75823835 glabrous short sepals
https://www.inaturalist.org/observations/77168514 glabrous short sepals
https://www.inaturalist.org/observations/77386917 glabrous short sepals
https://www.inaturalist.org/observations/77702361 glabrous short sepals
https://www.inaturalist.org/observations/78464955 glabrous short sepals
https://www.inaturalist.org/observations/78925219 glabrous short sepals
https://www.inaturalist.org/observations/79358374 glabrous short sepals
https://www.inaturalist.org/observations/79594252 glabrous short sepals
https://www.inaturalist.org/observations/80194371 glabrous short sepals

3) Pubescent and Long Sepals (nearly-as-long-as or longer than the flower petals)
https://www.inaturalist.org/observations/75264055 pubescent very long sepals ***
https://www.inaturalist.org/observations/75371414 pubescent long sepals
https://www.inaturalist.org/observations/75369222 pubescent long sepals
https://www.inaturalist.org/observations/75365581 pubescent long sepals
https://www.inaturalist.org/observations/75603724 pubescent long sepals
https://www.inaturalist.org/observations/76389550 pubescent long sepals
https://www.inaturalist.org/observations/76261689 pubescent long sepals
https://www.inaturalist.org/observations/77204533 pubescent long sepals
https://www.inaturalist.org/observations/77304357 pubescent long sepals
https://www.inaturalist.org/observations/77392727 pubescent long sepals
https://www.inaturalist.org/observations/77747127 pubescent long sepals
https://www.inaturalist.org/observations/77942031 pubescent long sepals
https://www.inaturalist.org/observations/78538457 pubescent long sepals
https://www.inaturalist.org/observations/78562824 pubescent long sepals
https://www.inaturalist.org/observations/78930613 pubescent long sepals

פורסם ב אפריל 26, 2021 11:03 לפנה"צ על־ידי mjpapay mjpapay

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