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Ferreira, Bianca [1], Glennon, Kelsey [2], Goodman, Glynis [3].

Morphometric and molecular analysis of the Senecio achilleifolius complex (Senecioneae, Asteraceae) in South Africa.

About 300 species of Senecio L. occur in South Africa. Three currently recognised species within Senecio sensu lato, viz., S. tanacetopsis, S. seminiveus and S. achilleifolius, require clearer delimitation. The species boundaries of these three species need to be re-assessed as they appear morphologically similar and may in fact be a single species. This study aimed to understand whether this species complex contains three distinct species, or simply three different growth forms or morphs of the same species that vary according to diverse environmental pressures and habitats over different altitudinal ranges. The Senecio achilleifolius species complex was revised and delimited using morphometric (quantitative and qualitative morphological data), ecological (altitudinal and distribution data), molecular AFLP data, and DNA sequence data to determine if one or more species should be recognised. Multivariate and molecular analyses of the S. achilleifolius complex do not support the three currently recognised species. The results support the description of a new taxon incorrectly included in the S. achilleifolius species group and the combination and reassignments of two defined species, S. seminiveus and S. tanacetopsis, as varieties of a single species. Altitudinal factors and other environmental stresses appear to affect some morphological features of the populations (e.g. capitula size, distance between leaves), resulting in considerable morphological variation between and within populations of the same species. A high number of individuals from the S. seminiveus and S. tanacetopsis populations showed admixture, which is likely due to the retention of ancestral polymorphisms between species groups (not hybridisation). Collectively, these data indicate that there is potentially a unique taxon within the complex, and that the complex comprises a S. achilleifolius and S. seminiveus with two varieties.

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1 - University of the Witwatersrand, School of Animal Plant and Environmental Sciences, 1 Jan Smuts Avenue, Braamfontein, Johannesburg, Gauteng, 2169, South Africa
2 - University Of The Witwatersrand, Animal, Plant & Environmental Sciences, Private Bag X3, Johannesburg, GT, WITS 2050, South Africa
3 - University Of The Witwatersrand, 1 Jan Smuts Avenue, Johannesburg, GT, 2050, South Africa

Morphological variation
species delimitation.

Presentation Type: Oral Paper
Session: SYSTI, Systematics I: Euasterids II
Location: Virtual/Virtual
Date: Tuesday, July 20th, 2021
Time: 10:15 AM(EDT)
Number: SYSTI002
Abstract ID:713
Candidate for Awards:None

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