The Distribution of Phytoecdysteroids among Terrestrial Vascular Plants: A Comparison of Two Databases and Discussion of the Implications for Plant/Insect Interactions and Plant Protection

Abstract

Phytoecdysteroids are a class of plant secondary compounds which are present in a wide diversity of vascular plant species, where they contribute to a reduction in invertebrate predation. Over the past 55 years, a significant body of heterogeneous literature on the presence, identities and/or quantities of ecdysteroids in plant species has accumulated, resulting in the compilation of a first database, the Ecdybase Literature Survey (ELS; 4908 entries, covering 2842 species). A second extensive database on the distribution of ecdysteroids in vascular plants is available as the Exeter Survey (ES; 4540 entries, covering 4155 species), which used standardised extraction and analysis methods to survey seeds/spores. We compare the usefulness of these two databases to provide information on the occurrence of phytoecdysteroids at the order/family levels in relation to the recent molecular classifications of gymnosperms, pteridophytes/lycophytes and angiosperms. The study, in conjunction with the other published literature, provides insights into the distribution of phytoecdysteroids in the plant world, their role in plant protection in nature and their potential future contribution to crop protection. Furthermore, it will assist future investigations in the chemotaxonomy of phytoecdysteroids and other classes of plant secondary compounds.

Keywords: 20-hydroxecdysone; Ecdybase; chemotaxonomy; ecdysone; ecdysteroids; molecular systematics.

Figure 1

Lycophytes and pteridophytes: Indication of the frequency of ecdysteroid-containing species within the orders of lycophytes and pteridophytes. The classification is according to PPG1 (Ref. [26]) and the data concerning the presence or absence of phytoecdysteroids were combined from the ‘Compilation of the literature reports for the screening of vascular plants, algae, fungi and non-arthropod invertebrates for the presence of ecdysteroids’ (ELS Version 11; www.ecdybase.org (accessed on 13 October 2021)), which provides data on 488 lycophyte and pteridophyte species, and the Exeter Survey (ES Version 1: www.ecdybase.org (accessed on 13 October 2021)), which provides data for only 17 pteridophyte species (Table S1). The data are qualitative (i.e., present or absent) and do not necessarily reflect the occurrence of high accumulators. The % frequencies of ecdysteroid-containing species amongst the assessed species in each family and order are indicated in the right-hand columns; nd = no data available.

Figure 2

Gymnosperms: Indication of the frequency of ecdysteroid-containing species within the orders of gymnosperm plants. The classification is according to Christenhusz et al. [28] and the data concerning the presence or absence of phytoecdysteroids were taken from the ‘Compilation of the literature reports for the screening of vascular plants, algae, fungi and non-arthropod invertebrates for the presence of ecdysteroids’ (ELS Version 11; www.ecdybase.org (accessed on 4 October 2021)), which provides data on 89 gymnosperm species (Table S2), and the Exeter Survey (ES Version 1: www.ecdybase.org (accessed on 4 October 2021)), which provides data on 86 gymnosperm species (Table S3). The data are qualitative (i.e., present or absent) and do not necessarily reflect the occurrence of high accumulators. The % frequencies of ecdysteroid-containing species amongst the assessed species in each order are indicated in the right-hand column; nd = no data available.

Figure 3

Angiosperms: Indication of the frequency of ecdysteroid-containing species within the orders of angiosperm plants. The classification is according to APGIV [27] and the data concerning the presence or absence of phytoecdysteroids were taken from (ELS) the ‘Compilation of the literature reports for the screening of vascular plants, algae, fungi and non-arthropod invertebrates for the presence of ecdysteroids’ (Version 11; www.ecdybase.org (accessed on 8 November 2021)), which provides data on 2282 angiosperm species (Table S4), the Exeter Survey (ES) (Version 1: www.ecdybase.org (accessed on 8 November 2021)), which provides data on 4052 angiosperm species (Table S5) and the randomly selected species of the Exeter survey (N-Series) (N-ES) comprising 2290 angiosperm species (Table S6). The data are qualitative (i.e., present or absent) and do not necessarily reflect the occurrence of high accumulators. The % frequencies of ecdysteroid-containing species amongst the assessed species in each order are indicated in the right-hand column; nd = no data available.