Refined taxon sampling discloses new quinone patterns and relationships among Sundews (Drosera, Droseraceae)

Abstract

In a screening of 43 accessions of predominantly Australian sundew species (Drosera), naphthoquinones were detected convincingly for the first time in D. section Lasiocephala (D. petiolaris group, or ‘wooly sundews’), where these metabolites remain restricted to a minority of four closely related species. Great chemical similarity across the large geographic range confirms a close phylogenetic affinity between taxa of the D. peltata species group (of D. section Ergaleium, from tropical and Eastern Asia to New Zealand). Drosera barrettiorum (D. section Arachnopus) is chemically confirmed as a close relative of D. hartmeyerorum. The recently described species D. margaritacea in the same section is chemically different from the morphologically close D. finlaysoniana. Quinone data for African and South American sundews (D. sections Drosera, Ptycnostigma and Brasilianae) shed further light on the affinities between these taxonomically challenging plants.

The taxonomic relevance of Naphthoquinones in tropical pitcher plants (Nepenthes L., Nepenthaceae)

“…The taxonomic utility of the distribution of the naphthoquinone isomers ramentaceone (7-methyljuglone, M) and plumbagin (2-methyljuglone, P) in the genus Nepenthes L. (Nepenthaceae) was already indicated by the first systematic screening (Schlauer et al 2005). In some respects, the distribution of the isomers throughout the genus resembles patterns found in the closely related family Droseraceae (Culham & Gornall 1994;Schlauer et al 2017;Schlauer et al 2018;Schlauer et al 2019a-c;Schlauer & Fleischmann 2021;Schlauer & Fleischmann 2022). All Nepenthes species investigated so far share the same chromosome count of 2n = 80 (Heubl & Wistuba 1998), while chromosome counts in Droseraceae are more diverse, with most species (ca.…”

Distribution of Acetogenic Naphthoquinones in Droseraceae and Their Chemotaxonomic Utility

“…The distribution of individual naphthoquinone isomers that have been detec identified species of Droseraceae is summarized in Table 1 that also contains inform on the classification of the investigated taxa, the provenance of the investigated sa and comments that essentially relate to the (few) differences between subseq independent studies. Throughout the past decade, significant progress has been made in the screening for naphthoquinones in Droseraceae [14][15][16][17][18][19][20][21][22], and although several papers aimed to address these specific metabolites at various degrees of accuracy [1,[23][24][25], none of the recent reviews represented their meanwhile known isomer distribution satisfactorily. It is the aim of the present account to fill this gap, so that chemotaxonomic considerations can be based on adequate data.…”

“…While naphthoquinones may aid in preserving animal prey and protecting plant traps during digestion [44], and precursors acquired by carnivory are channeled into their biosynthetic pathway [45], the speculation that this may be an "important adaptation" across all carnivorous Nepenthales [46] is flawed by the fact that there are a few species of Nepenthes [47] and a comparatively large number of species of Drosera (Table 1, [21,22,27]) in which neither plumbagin nor ramentaceone have been detected. Although it was mentioned that the acetogenic naphthoquinones of carnivorous Nepenthales are lacking in all other lineages of carnivorous plants [46] where, interestingly, other characteristic acetogenic polyketides occur in some families such as the alkaloid coniine in Sarracenia [48], it was not appropriately considered that plumbagin is present in the closely related but noncarnivorous Plumbaginaceae (consecutive sister to the carnivorous clade of Nepenthales [9]) and Ancistrocladaceae (carnivory lost secondarily [9]).…”

“…Throughout the past decade, significant progress has been made in the screeni naphthoquinones in Droseraceae [14][15][16][17][18][19][20][21][22], and although several papers aimed to ad these specific metabolites at various degrees of accuracy [1,[23][24][25], none of the r reviews represented their meanwhile known isomer distribution satisfactorily. It aim of the present account to fill this gap, so that chemotaxonomic considerations c based on adequate data.…”

Attracted to feed, not to be fed upon – on the biology of Toxomerus basalis (Walker, 1836), the kleptoparasitic ‘sundew flower fly’ (Diptera: Syrphidae)

“…Hil. contain both naphthoquinone regioisomers 7-methyljuglone and plumbagin, while D. spiralis, D. magnifica, and D. × fontinalis Rivadavia contain only the former (while sympatric diploid Drosera species of D. section Drosera contain only the latter), and D. chrysolepis Taub., D. camporupestris Rivadavia and D. graomogolensis are devoid of any acetogenic naphthoquinones (Schlauer et al 2019;Schlauer & Fleischmann 2022). Hence, the naphthoquinone patterns are too variable in the documented host species to serve in host recognition, but other characteristic Drosera volatiles might be perceived by gravid Toxomerus females, allowing them to recognize their larval host plants.…”