Calla palustris (Araceae): New palynological insights with special regard to its controversial systematic position and to closely related genera

Abstract

Almost all systematic treatments agree that is a puzzling case, being a highly autapomorphic taxon with obscure relationships. In molecular-based classifications the variable placements of within Aroideae conflict strongly with those in morphologically and anatomically based systematic classifications, which treat the genus as a subfamily (Calloideae) of its own. We studied the pollen morphology and ultrastructure of by light and electron microscopy, and mapped the relevant pollen characters as well as some flower characters to the proposed placements of within the Araceae as indicated in the various molecular phylogenies. pollen is extraordinary within the entire Araceae. Pollen grains are small, and basically disulcate or with a ring-like aperture. The ornamentation is psilate to perforate, and the pollen wall consists of a sporopolleninous tectate-columellate exine. These pollen characters are shared with those of several earlier-diverging aroid taxa, especially with those of subfamily Zamioculcadoideae, whereas pollen characters in members of subfamily Aroideae deviate significantly. These findings are in accordance with other floral characters. Therefore, we propose that is best placed in a transition zone between either subfamily Zamioculcadoideae ( clade) and subfamily Aroideae (Aroideae clade) or between subfamily Zamioculcadoideae ( clade) and subfamily Lasioideae.

The Evolution of Pollinator-Plant Interaction Types in the Araceae

“…), and Nephthytis (2 spp. ), and the species Calla palustris was sequenced twice (because of its unexpected systematic placement; Ulrich et al 2013).…”

A Review on the Pollination of Aroids with Bisexual Flowers

“…2H). Its cylindrical spadix comprises white, bisexual flowers (Lehman & Sattler, 1992;Ulrich et al, 2013) and at the top a group of flowers with exclusively nonfunctional stamens (Chartier et al, 2017).…”

“…Some subfamilies, like Pothoideae, encompass species-rich genera, such as Anthurium Schott, whereas others, e.g., Gymnostachydoideae, are monotypic (Mayo et al, 1997). These plants (including the monotypic genus Calla L., possibly included in Aroideae or sister to it, but whose position remains uncertain; see Ulrich et al, 2013;Chartier et al, 2014) encompass 31 genera and about 1500 species (Mayo et al, 1997;Boyce & Croat, 2018). In contrast to taxa with unisexual flowers, their pollination mechanisms are still poorly understood (Mayo et al, 1997;Hentrich et al, 2010).…”

Target sequence data shed new light on the infrafamilial classification of Araceae

“…On the other hand, the unisexual clade is itself unsupported in the most comprehensive analyses so far published (Cabrera et al, 2008;Cusimano et al, 2011;Nauheimer et al, 2012;Chartier et al, 2014). Further ambiguity is provided by the genus Calla, which combines bisexual flowers and pollen structure more typical of bisexual-flowered genera (Ulrich et al, 2013), but which is consistently placed within the unisexual clade by molecular analyses and in very variable positions (Figure 1). The potential of phylogenomic tools to provide new evidence on the floral sexuality transition first began to be demonstrated in an analysis by Henriquez et al (2014), who studied whole plastid genomes of 37 genera and found full support for the unisexual clade, placing Calla well within it and at a position comparable to the finding of Cusimano et al (2011).…”