Extreme haustorial parasites have long captured the interest of naturalists and scientists with their greatly reduced and highly specialized morphology. Along with the reduction or loss of photosynthesis, the plastid genome often decays as photosynthetic genes are released from selective constraint. This makes it challenging to use traditional plastid genes for parasitic plant phylogenetics, and has driven the search for alternative phylogenetic and molecular evolutionary markers. Thus, evolutionary studies, such as molecular clock-based age estimates, are not yet available for all parasitic lineages. In the present study, we extracted 14 nuclear single copy genes (nSCG) from Illumina transcriptome data from one of the “strangest plants in the world”, Hydnora visseri (Hydnoraceae). A ∼15,000 character molecular dataset, based on all three genomic compartments, shows the utility of nSCG for reconstructing phylogenetic relationships in parasitic lineages. A relaxed molecular clock approach with the same multi-locus dataset, revealed an ancient age of ∼91 MYA for Hydnoraceae. We then estimated the stem ages of all independently originated parasitic angiosperm lineages using a published dataset, which also revealed a Cretaceous origin for Balanophoraceae, Cynomoriaceae and Apodanthaceae. With the exception of Santalales, older parasite lineages tend to be more specialized with respect to trophic level and have lower species diversity. We thus propose the “temporal specialization hypothesis” (TSH) implementing multiple independent specialization processes over time during parasitic angiosperm evolution.

The genus Peperomia is one of the largest genera of basal angiosperms, comprising about 1500 - 1700 pantropically distributed species. The currently accepted infrageneric classification di...

A striking feature of early angiosperm lineages is the variety of life forms and growth forms, which ranges from herbs, aquatic herbs, climbers, and epiphytes to woody shrubs and trees. This morphological and anatomical diversity is arguably one of the factors explaining how angiosperms dominate many ecosystems worldwide. However, just how such a wide spectrum of growth forms has evolved in angiosperms remains unclear. In this review, we investigate patterns of growth form diversification in Piperales, an early-diverging lineage (with stem age estimated at 201-128 Myr ago) and the most morphologically diverse clade among magnoliids. We outline patterns of growth form diversity and architecture as well as the biomechanical significance of developmental characters, such the organization, loss, and gain of woodiness. Asaroideae and Saururaceae are terrestrial as well as semiaquatic to aquatic herbaceous perennials bearing rhizomes. The Aristolochioideae and Piperaceae show higher levels of growth form diversity and biomechanical organization, with complex patterns of increasing or decreasing woodiness and architectural organization. The climbing habit has probably evolved independently in the Aristolochiaceae and Piperaceae, while mechanically unstable shrubs and, less frequently, treelets have evolved several times within these two most species-rich clades. A key developmental character underlying diversity in most Piperales-with the exception of the herbaceous Saruma (Asaroideae)-is the conserved development of the wood cylinder, in which fusiform initials are limited to fascicular carnbial initials. The resulting large fraction of raylike tissue in the stem-a highly characteristic feature of woody species in the Piperales-potentially introduced mechanical constraints on the diversification of self-supporting architectures. This was possibly circumvented by the architectural development of repeated, large-diameter meristems in some shrublike habits via sympodial growth. Patterns of growth form evolution within Piperales potentially mirror some of the overall trends observed among early-diverging angiosperms as a whole as well as angiosperms in general. These include profound changes in life form and growth form linked to large-scale transitions in woodiness, diversity of mechanical organization, and shifts in architectural development