A Numerical Taxonomic Study of Portulaca oleracea

Abstract

A phenetic classification of 44 ecotypes of common purslane (Portulaca oleracea L.) produced 4 major groups: cool temperate; warm temperate to wet dry subtropic; humid subtropic to tropic; and cultivated. These groups were based on 36 plant characteristics; the ecotypes were collected from 18 countries and are representative of climates inhabited by common purslane. The cultivated group is comprised of robust forms which are raised for culinary purposes. For weed forms, plants of the cool temperate group were small, prostrate plants with size and growth habit increasing to maximum in the humid subtropic to tropic group.

Exploring C4–CAM plasticity within the Portulaca oleracea complex

“…A comprehensive phylogeny including as many accessions of P. oleracea as possible will be needed to solve the species paraphyletic scenario, but its cosmopolitan distribution may prove to be a challenge to this goal. In the present study, we selected genotypes sampled from independent populations and identified as different subspecies, and the clustering methods applied here confirmed previously described trends 38 , where weedy (small, prostrate and branched) phenotypes were clustered separately from more robust and erect phenotypes, e.g. commercial cultivars.…”

“…It also presents a cosmopolitan distribution, occurring in most tropical and subtropical regions 36 . Variations in chromosome number 37 , vegetative and reproductive morphology 38 – 42 are already described between accessions of this species. Because of such high phenotypical plasticity, P. oleracea is sometimes referred to as a polymorphic species 33 , 37 , or even subdivided into different subspecies 43 , 44 or microspecies 45 – 47 that form a taxonomic aggregate or complex.…”

“…To our knowledge, taxonomic reports list 19 subspecies/microspecies distinguished according to their seed size and coat ornaments 46 . On the other hand, P. oleracea is sometimes considered a polymorphic species, and due to its cosmopolitan distribution and high adaptability, it is somewhat expected to present high variability in morphological traits among populations, even forming a continuum 33,37,38,71 . Such plasticity might also affect seed attributes, making seed morphology and size alone inconclusive to differentiate subspecies, especially considering that hybrid subspecies have already been reported in mixed populations 33,37 .…”

“…Morphometric measurements were performed in at least 25 individuals of each subspecies grown for 8-10 weeks under well-watered conditions. The following parameters were selected based on existing literature 38 and analyzed: plant height (cm), fresh plant weight (g), number of primary and secondary branches, diameter of stem base and apex (cm, measured at approximately 1 cm from plant edges and used to calculate stem base/apex ratio), total and mean leaf area (cm 2 ), leaf length and width (used to calculate leaf format ratio), and succulence (saturated water content 84 ).…”

Flow cytometric, chromosomal and morphometric analyses challenge current taxonomic concepts in thePortulaca oleraceacomplex (Portulacaeae, Caryophyllales)

“…Gorske, Rhodes & Hoppen () demonstrated that the cultivated forms can be separated by, among other morphological characters, seed size from the wild representatives of the P. oleracea complex. The taxonomic value of seed characters, however, for the discrimination of the wild representatives is uncertain.…”