Single-Copy Nuclear Genes Place Haustorial Hydnoraceae within Piperales and Reveal a Cretaceous Origin of Multiple Parasitic Angiosperm Lineages
Figure 5
The “temporal specialization hypothesis” (TSH) postulates increasing specialization during the evolution of parasitism in plants.
Relationship of stem age, species number, host range, trophic type and host attachment site of the parasitic lineages is shown. The estimated age of each parasite lineage is plotted relative to lineage size (the species numbers are taken from the review by Westwood et al. [51]). The color of the symbol represents the trophic type for the indicated lineage (blue: autotrophic; yellow: hemiparasitic; red: holoparasitic), the shape indicates the mode of attachment (square: root parasite; round: stem parasite; rhomb: stem and root parasite; rimmed: endophytic) and the size represents host range (large: generalist on more than five families; medium: intermediate host range of two to five families; small: specialist on only one host family; shaded: all types of host ranges). Santalales and Balanophoraceae are plotted separately and together since phylogenetic analyses to date are inconclusive about the origin of Balanophoraceae within Santalales [36]. As the host range is difficult to capture, we chose three categories. A lineage is categorized by the typical host range and exceptions may exist. For Hydnoraceae hosts typically occur in just two families (Fabaceae, Euphorbiaceae), however, Prosopanche bonacinae has a broad host spectrum of numerous families. Abbreviations: Apo: Apodanthaceae; Bal: Balanophoraceae; Cas: Cassytha; Cus: Cuscuta; Cyn: Cynomoriaceae; Cyt: Cytinaceae; Hyd: Hydnoraceae; Kra: Krameriaceae; Len: Lennoaceae (Boraginaceae sf. Lennooideae); Mit: Mitrastemonaceae; Oro: Orobanchaceae; Raf: Rafflesiaceae; San: Santalales.