Reestablishment of Cabomba schwartzii (Cabombaceae), an aquatic plant species endemic to the Brazilian Amazon

Abstract

Cabomba schwartzii was described by Rataj in 1977. The species discovered in the Brazilian Amazon was said to differ from other Cabomba species in having two sepals, two petals and a lobate petal base. According to the 1991 study of Ørgaard, C. schwartzii is similar to C. aquatica in other morphological characters (C. aquatica has flowers with three sepals and three petals) and since variation in number of floral parts is common in the genus, Ørgaard synonymized both species. After an analysis of C. schwartzii type material, other herbarium collections and location of four populations (two with C. schwartzii characteristics and two with C. aquatica characteristics), we conducted an integrated morphological and genetic study to evaluate whether or not C. schwartzii is a distinct species from C. aquatica. The results reveal the species to be distinct from each other and therefore C. schwartzii should be reestablished. The floral formula for C. schwartzii is K2 C2 A2+2 G1, versus K3 C3 A3+3 G2 for C. aquatica. A detailed species description and the geographical distribution of C. schwartzii are presented with a dichotomous key to distinguish both species, together with illustrations.

Notes on the distribution of Brasenia schreberi (Cabombaceae) in the Neotropics, with a new country record for Costa Rica

“…(Amborellaceae), the order Nymphaeales is sister to all the remaining extant angiosperms, based on phylogenetic evidence from both plastid and nuclear DNA sequence data (Li et al, 2019;Yang et al, 2020;Zhang et al, 2020). Although not particularly species-rich (94 spp: Barbosa et al, 2018;Govaërts, 2021;Lima et al, 2021), Nymphaeales has a subcosmopolitan distribution, being widespread in lentic, or rarely lotic, freshwater habitats of all continents and regions, except the polar ones and, with few exceptions, most deserts and mountainous regions (Stevens, 2001;La-ongsri et al, 2009;Christenhusz et al, 2017). Of the three families of the order, morphologically aberrant Hydatellaceae (13 species: Govaërts, 2021) is restricted to India, Australia and New Zealand (Sokoloff et al, 2019).…”

“…Finally, Cabombaceae is native to all continents, except Antarctica and Europe, but outside the Americas its distribution seems to be restricted and localized. It only has seven accepted species (Ørgaard, 1991;Wiersema, 1997;Barbosa et al, 2018) in two genera: Cabomba Aubl. (6 species) and Brasenia Schreb.…”