No abstract

The date palm, Phoenix dactylifera, has been a cornerstone of Middle Eastern and North African agriculture for millennia. It was first domesticated in the Persian Gulf, and its evolution appears to have been influenced by gene flow from two wild relatives, P. theophrasti, currently restricted to Crete and Turkey, and P. sylvestris, widespread from Bangladesh to the West Himalayas. Genomes of ancient date palm seeds show that gene flow from P. theophrasti to P. dactylifera may have occurred by ∼2,200 y ago, but traces of P. sylvestris could not be detected. We here integrate archaeogenomics of a ∼2,100-year-old P. dactylifera leaf from Saqqara (Egypt), molecular-clock dating, and coalescence approaches with population genomic tests, to probe the hybridisation between the date palm and its two closest relatives and provide minimum and maximum timestamps for its reticulated evolution. The Saqqara date palm shares close genetic ancestry with North African date palm populations, and we find clear genomic admixture from both P. theophrasti, and P. sylvestris, indicating that both had contributed to the date palm genome by 2,100 years ago. Molecular-clocks placed the divergence of P. theophrasti from P. dactylifera/P. sylvestris in the Upper Miocene and that of P. dactylifera from P. sylvestris in the earliest Quaternary. Our work highlights the ancient hybrid origin of the date palms, and prompts the investigation of the functional significance of genetic material introgressed from both close relatives, which in turn could prove useful for modern date palm breeding.

Summary.A taxonomic revision is presented of the Hydriastele wendlandiana group, a well-defined species grouping within the Indo-Pacific palm genus Hydriastele that occurs in New Guinea, the Bismarck Archipelago and northern Australia. We accept five species: Hydriastele kasesa, H. rheophytica, H. variabilis, H. wendlandiana and H. apetiolata sp. nov. and provide fundamental information about each of those taxa including a summary of the group's taxonomic history and phylogeny, a distribution map, a key to the species, species descriptions with scientific illustrations, and IUCN Red List assessments.

A taxonomic revision is presented of the Nengella group of the palm genus Hydriastele (Arecaceae: Arecoideae) in New Guinea, which comprises slender understorey or midstorey palms with small, protandrous inflorescences. Seven species are accepted: Hydriastele aprica, H. divaricata sp. nov., H. flabellata, H. montana, H. pinangoides, H. simbiakii sp. nov., and H. splendida sp. nov. All species are illustrated and their distributions are mapped. In addition, a key to species and preliminary IUCN Red List Assessments are provided.

The date palm (Phoenix dactylifera) has been a cornerstone of Middle Eastern and North African agriculture for millennia. It is presumed that date palms were first domesticated in the Persian Gulf and subsequently introduced into North Africa, where their evolution in the latter region appears to have been influenced by gene flow from the wild relative P. theophrasti, which is restricted to Crete and Turkey. However, the timing of gene flow from P. theophrasti to P. dactylifera remains unknown due to the limited archaeobotanical evidence of P. theophrasti and their exclusion from population genomic studies.We addressed this issue by investigating the relatedness and ancestry of a ~2,100-year-old P. dactylifera leaf from Saqqara (Egypt), combining genome sequencing of this ancient specimen with a broad sample of date palm cultivars and closely related species.The ancient Saqqara date palm shares close genetic ancestry with North African date palm populations. We find clear genomic admixture between the Saqqara date palm, P. theophrasti and the closest known relative P. sylvestris.Our study highlights that gene flow from P. theophrasti and P. sylvestris to North African date palms had already occurred at least ~2,100 years ago, providing a minimum timestamp for hybridisation between species.

The production of flowers and fruit below ground (geoflory and geocarpy, respectively) is a paradoxical reproductive strategy that seemingly hinders pollination and dispersal. Though rare, these phenomena occur in 33 angiosperm families. Plants that flower and fruit entirely below ground are exceptionally unusual. Pinanga subterranea (Arecaceae), a species new to science from Borneo, is the first member of the palm family recorded to flower and fruit almost exclusively below ground. This raises many questions about its evolution, pollination and dispersal, which we discuss here. Strikingly, this remarkable species is widespread across western Borneo and valued by the local people for its edible fruits but has escaped the attention of scientists until now.

A revision of the genus Heterospathe Scheff. in New Guinea and immediately adjacent islands is presented. We recognise 14 species for this area. Taxonomic and nomenclatural changes are outlined, and each species is thoroughly described, mapped and illustrated. A key to the species in the area is included as well as preliminary IUCN Red List Assessments.

A taxonomic revision of the genus Hydriastele H.Wendl. & Drude in New Guinea, Australia and immediately adjacent islands is presented. We recognise 25 species from this area including three new species of robust tree palms from New Guinea: Hydriastele calcicola, H. lanata and H. wosimiensis. All species are described in full in the taxonomic treatment, with accompanying botanical illustrations, photographs, distribution maps and preliminary IUCN Red List Assessments. In addition, a key to the species in New Guinea and Australia is provided as well as a systematic conspectus placing all 39 accepted species of Hydriastele in an informal infrageneric framework.