Sand-binding roots in Haemodoraceae: global survey and morphology in a phylogenetic context

Abstract

Aims To illustrate the morphology of sand-binding roots of Haemodoraceae, to conduct a comprehensive survey of the trait, spanning different climates across four continents, and to explore evolutionary hypotheses within a molecular phylogenetic framework. Methods Sand-binding roots in Haemodoraceae were examined, measured and photographed in the field and on herbarium specimens. Photomicrographs were taken of southwest Australian species. The presence and absence of the sand-binding trait was mapped onto previously published phylogenies and an ancestral state reconstruction was performed. Results Sand grains were very tightly bound to the root surface by persistent root hairs in Haemodoraceae. The majority of genera and species were found to possess sand-binding roots and only 2 of the 14 genera, Conostylis and Tribonanthes, had sister taxa with and without the trait. The trait was recorded in tropical, sub-tropical and wet temperate species, but mainly in semi-arid species. Sand-binding roots were likely to have been present in the ancestor of the family and both sub-families.Conclusions The presence of sand-binding roots is the probable ancestral condition for Haemodoraceae, associated with a high degree of phylogenetic conservatism and some secondary loss, notably in Conostylis. Experimental studies are needed to understand the ecological and evolutionary forces at work.

Total evidence phylogeny of Pontederiaceae (Commelinales) sheds light on the necessity of its recircumscription and synopsis of Pontederia L.

“…These authors also state that all studied specimens of Philydraceae and Pontederiaceae had non-sand-binding roots, in contrast to Haemodoraceae. On the other hand, sand-binding roots are commonly observed in several lineages of Commelinaceae, but especially in species growing in dry environments (Smith et al 2011; Pellegrini, pers. observ.).…”

“…are suggested here for the first time. Sand-binding roots were recovered by Smith et al (2011) as plesiomorphic for Haemodoraceae and probably for all Commelinales, despite the authors’ not sampling Hanguanaceae in their analysis. These sand-binding roots produce specialised hairs that bind soil, especially larger sand crystals, creating a protective layer that envelops the roots (Smith et al 2011).…”

“…Sand-binding roots were recovered by Smith et al (2011) as plesiomorphic for Haemodoraceae and probably for all Commelinales, despite the authors’ not sampling Hanguanaceae in their analysis. These sand-binding roots produce specialised hairs that bind soil, especially larger sand crystals, creating a protective layer that envelops the roots (Smith et al 2011). These authors also state that all studied specimens of Philydraceae and Pontederiaceae had non-sand-binding roots, in contrast to Haemodoraceae.…”

Biodiversity hotspots and Ocbil theory

“…Extremely nutrient-impoverished soils are commonplace across all Ocbils recognised to date (Lambers et al 2008(Lambers et al , 2010Cramer 2010;Cramer et al 2014;Edwards et al 2015;Oliveira et al 2015), but the consequences of Pdeficient soils are only beginning to emerge. Severe nutrient limitations entail constraints for plant growth rates , investment in sexual reproduction (Fujita et al 2014) and the evolution of unique functional diversity strategies for nutrient acquisition (Lambers et al 2010;Smith et al 2011;Abrahão et al 2014).…”

“…inselberg biodiversity and adaptations (Gibson et al 2010;Poot et al 2012;Millar et al 2014;Tapper et al 2014a, b). plant phylogeny (e.g., Smith et al 2011), semiarid speciation processes (Cardillo and Pratt 2013;Ellis et al 2014;Rix et al 2014). paleoendemism (Sole et al 2013;Proches 2014).…”