Taxonomic investigation of the Xanthium strumarium L. complex (Asteraceae) distributed in Iran inferred from morphological, palynological and molecular data

Abstract

Abstract. Noedoost F, Vaezi J, Nikzat Siahkolaee S. 2021. Taxonomic investigation of the Xanthium strumarium L. complex (Asteraceae) distributed in Iran inferred from morphological, palynological and molecular data. Biodiversitas 22: 1961-1974. Unclear species boundaries due to high morphological similarities lead to different opinions on Xanthium classification. To solve this problem, we conducted investigation on morphological, palynological and molecular (ITS sequencing) of three species of Xanthium (i.e., X. strumarium, X. sibiricum, and X. brasilicum) forming Xanthium strumarium complex in Iran. We randomly collected 110 plant individuals of the Xanthium strumarium complex as well as X. spinosum from 30 geographical populations in eight provinces of Iran. Pollen grains of 19 populations were studied by scanning electron microscope (SEM). Results obtained from the analysis of morphological characters showed that the three species, X. strumarium, X. brasilicum and X. sibiricum were placed nearly together specially X. strumarium and X. brasilicum are obviously overlapped. Palynological results indicated the pollen grains of section Acanthoxanthium (i.e., X. spinosum) and Xanthium (i.e., X. strumarium, X. sibiricum, and X. brasilicum) are clearly differing by their LM and SEM characters. However, no significant difference found between the pollen of X. strumarium and X. brasilicum. The Bayesian phylogenetic tree of the ITS region of rDNA sequences revealed that X. strumarium, X. sibiricum and X. brasilicum could not be discriminated as independent species. Overall, the morphological, palynological and molecular data provided evidence to synonymize X. brasilicum and X. strumarium with X. orientale and X. sibiricum with X. strumarium.

Pollen morphological characters variation among species of Strobilanthes s.l. from Sumatra, Indonesia and its taxonomic implications

“…Pollen size and pollen shape also can further give information concerning species identification (Krachai and Pornpongrungrueng 2015;House 2016;Noedoost et al 2021). The study noticed that pollen size and shape were the characters that helped to distinguish the taxa at the species level (Akhila and Beevy 2015).…”

“…They can be used to solve the taxonomic problems of plant groups, such as identification, taxa delimitation, classification and relationship assessment (Yao and Zhang 2016;Al-Hakimi et al 2017;Tripathi et al 2017;Ruiz-Domínguez et al 2019;Chen et al 2019;de Souza et al 2019;Ragho 2020). The pollen morphological characters such as polar axis length (P), equatorial diameter (E), P/E ratio, pollen sculpture or exine ornamentation (Via do Pico and Dematteis 2013;Ferrauto and Pavone 2014;Sarwar et al 2015;Al-Hakimi et al 2018), pollen size, pollen shape, exine thickness (Akhila and Beevy 2015;Krachai and Pornpongrungrueng 2015;Noedoost et al 2021) are valuable for distinguishing and identification of many plant groups.…”

Direct and indirect targets of carboxyatractyloside, including overlooked toxicity toward nucleoside diphosphate kinase (NDPK) and mitochondrial H + leak

“…This perplexing situation suggests that X. orientale may in fact be an ecotype/hybrid/transition morphotype of X. strumarium , which is supported, e.g., by internal transcribed spacer (ITS) sequencing (Noedoost et al. 2021 ). Therefore, the term ‘ X. strumarium complex' might reflect a spectrum of this polymorphic species (Noedoost et al.…”

“…Therefore, the term ‘ X. strumarium complex' might reflect a spectrum of this polymorphic species (Noedoost et al. 2021 ; Müller-Kiefer and Tomasello 2022 ). This multitude of names results from the fact that the members of the Xanthium genus exhibit extensive variation in mature bur morphology within the same population and between isolated populations ( Figure 2 ), including the size of the bur, which is frequently and inaccurately referred to as fruit (Löve and Dansereau 1959 ; Löve 1975 ; Hare 1980 ; Weaver and Lechowicz 1983 ; Abbas et al.…”

“… 2005 ; Tomasello 2018 ; Noedoost et al. 2021 ; Ullah, Khan, Ali, et al 2021 ; Ullah, Khan, and Rahman 2021 ; Jepson Flora Project 2022 ; Ullah, Khan, and Ali 2022 ; Ullah, Khan, Hewitt, et al 2022 ). In fact, the bur is the fruit pod developed from fused involucre in which bract tips are transformed into spines, and the bur derives from fruiting, thus the female (pistillate) flower head (capitulum).…”