Arceuthobium M.Bieb. (Viscaceae) parasitizing an angiosperm: the unique case of A. azoricum Hawksw. & Wiens in the Azores islands

Arceuthobium azoricum Wiens & Hawksw. is a rare Azorean endemic epiphytic hemiparasite (mistletoe), that typically parasitizes branches of the gymnosperm Juniperus brevifolia (Hochst. ex Seub.) Antoine (Cupressaceae), also an Azorean endemic. Here we describe one population of A. azoricum, on Pico Island, parasitizing Erica azorica Hochst. ex Seub (Ericaceae) also an Azores endemic. Our molecular analysis (using nuclear ribosomal ITS) showed no differences between individuals parasitizing Erica and Juniperus. Moreover, a preliminary analysis showed no differences in morphological characters between accessions sampled from the different hosts. Given that this is the first bona fide record of Arceuthobium parasitizing an angiosperm, this population represents a unique host shifting event and its conservation is important because it may allow new insights into host recognition mechanisms in mistletoes. Immediate attention should be given to characterize this Pico Island population using appropriate molecular methods and additional morphological analyses.

Global models and predictions of plant diversity based on advanced machine learning techniques

Despite the paramount role of plant diversity for ecosystem functioning, biogeochemical cycles, and human welfare, knowledge of its global distribution is still incomplete, hampering basic research and biodiversity conservation. Here, we used machine learning (random forests, extreme gradient boosting, and neural networks) and conventional statistical methods (generalized linear models and generalized additive models) to test environment-related hypotheses of broad-scale vascular plant diversity gradients and to model and predict species richness and phylogenetic richness worldwide. To this end, we used 830 regional plant inventories including c. 300 000 species and predictors of past and present environmental conditions. Machine learning showed a superior performance, explaining up to 80.9% of species richness and 83.3% of phylogenetic richness, illustrating the great potential of such techniques for disentangling complex and interacting associations between the environment and plant diversity. Current climate and environmental heterogeneity emerged as the primary drivers, while past environmental conditions left only small but detectable imprints on plant diversity. Finally, we combined predictions from multiple modeling techniques (ensemble predictions) to reveal global patterns and centers of plant diversity at multiple resolutions down to 7774 km² . Our predictive maps provide accurate estimates of global plant diversity available at grain sizes relevant for conservation and macroecology.

The Global Naturalized Alien Flora (GloNAF) database

This dataset provides the Global Naturalized Alien Flora (GloNAF) database, version 1.2. GloNAF represents a data compendium on the occurrence and identity of naturalized alien vascular plant taxa across geographic regions (e.g. countries, states, provinces, districts, islands) around the globe. The dataset includes 13,939 taxa and covers 1,029 regions (including 381 islands). The dataset is based on 210 data sources. For each taxon-by-region combination, we provide information on whether the taxon is considered to be naturalized in the specific region (i.e. has established self-sustaining populations in the wild). Non-native taxa are marked as "alien", when it is not clear whether they are naturalized. To facilitate alignment with other plant databases, we provide for each taxon the name as given in the original data source and the standardized taxon and family names used by The Plant List Version 1.1 (http://www.theplantlist.org/). We provide an ESRI shapefile including polygons for each region and information on whether it is an island or a mainland region, the country and the Taxonomic Databases Working Group (TDWG) regions it is part of (TDWG levels 1-4). We also provide several variables that can be used to filter the data according to quality and completeness of alien taxon lists, which vary among the combinations of regions and data sources. A previous version of the GloNAF dataset (version 1.1) has already been used in several studies on, for example, historical spatial flows of taxa between continents and geographical patterns and determinants of naturalization across different taxonomic groups. We intend the updated and expanded GloNAF version presented here to be a global resource useful for studying plant invasions and changes in biodiversity from regional to global scales. We release these data into the public domain under a Creative Commons Zero license waiver (https://creativecommons.org/share-your-work/public-domain/cc0/). When you use the data in your publication, we request that you cite this data paper. If GloNAF is a major part of the data analyzed in your study, you should consider inviting the GloNAF core team (see Metadata S1: Originators in the Overall project description) as collaborators. If you plan to use the GloNAF dataset, we encourage you to contact the GloNAF core team to check whether there have been recent updates of the dataset, and whether similar analyses are already ongoing.

Possible loss of the chloroplast genome in the parasitic flowering plant Rafflesia lagascae (Rafflesiaceae)

Rafflesia is a genus of holoparasitic plants endemic to Southeast Asia that has lost the ability to undertake photosynthesis. With short-read sequencing technology, we assembled a draft sequence of the mitochondrial genome of Rafflesia lagascae Blanco, a species endemic to the Philippine island of Luzon, with ∼350× sequencing depth coverage. Using multiple approaches, however, we were only able to identify small fragments of plastid sequences at low coverage depth (<2×) and could not recover any substantial portion of a chloroplast genome. The gene fragments we identified included photosynthesis and energy production genes (atp, ndh, pet, psa, psb, rbcL), ribosomal RNA genes (rrn16, rrn23), ribosomal protein genes (rps7, rps11, rps16), transfer RNA genes, as well as matK, accD, ycf2, and multiple nongenic regions from the inverted repeats. None of the identified plastid gene sequences had intact reading frames. Phylogenetic analysis suggests that ∼33% of these remnant plastid genes may have been horizontally transferred from the host plant genus Tetrastigma with the rest having ambiguous phylogenetic positions (<50% bootstrap support), except for psaB that was strongly allied with the plastid homolog in Nicotiana. Our inability to identify substantial plastid genome sequences from R. lagascae using multiple approaches—despite success in identifying and developing a draft assembly of the much larger mitochondrial genome—suggests that the parasitic plant genus Rafflesia may be the first plant group for which there is no recognizable plastid genome, or if present is found in cryptic form at very low levels.

First Report of Arceuthobium hondurense in Oaxaca, Mexico

Honduran dwarf mistletoe (Arceuthobium hondurense Hawksw. & Wiens) has only been found in four locations in Honduras: west of Zamorano, east of Lepaterique, Cusuco National Park, and Celaque National Park (1,2). At one time it was believed that this mistletoe could be in danger of extinction (1). However, it has also been reported in two locations in Chiapas, Mexico (3). In December 2000, ≈1 km north of Suchixtepec, Oaxaca, Mexico, near Route 175 (elevation 2,770 m), we collected a dwarf mistletoe parasitizing Pinus tecunumanii (Schw.) Eguiluz et Perry that was morphologically similar to A. hondurense (1). This population initially had been classified as A. nigrum Hawksw. & Wiens (1), but is now classified as A. hondurense based on morphology (male flower color and stigma length) (1) and analysis of nuclear rDNA internal transcribed spacer (ITS) sequences from Honduras (GenBank Accession No. AF325969) and Oaxaca (GenBank Accession No. AY055215). A comparison of these two A. hondurense ITS sequences indicated they are very closely related to each other, whereas both are distinct from A. nigrum (GenBank Accession No. L25693). Specimens of A. hondurense from Oaxaca were deposited at the Deaver Herbarium, Northern Arizona University, Flagstaff. To our knowledge, this is the first report of A. hondurense in Oaxaca, Mexico, and extends its known distribution west across the Isthmus of Tehuantepec from central Chiapas by ≈400 km. References: (1) F. G. Hawksworth and D. Wiens. Dwarf Mistletoes: Biology, Pathology, and Systematics. USDA Agric. Handb. 709, 1996. (2) R. Mathiasen et al. Phytologia 85:268, 1998. (3) R. Mathiasen et al. Plant Dis. 85:444, 2001.

First Report of Arceuthobium hondurense in Mexico

Honduran dwarf mistletoe (Arceuthobium hondurense Hawksw. & Wiens) is a rare dwarf mistletoe previously known only from Honduras (1,2). In March 2000 we collected a dwarf mistletoe from approximately 7 km west of San Cristobal de las Casas, Chiapas, Mexico near Route 190 (elevation 2,440 m), which was morphologically similar to A. hondurense (1). This population had initially been classified as A. nigrumHawksw. & Wiens (1). However, our morphological measurements and analysis of nuclear rDNA ITS sequences of A. hondurense plants from Honduras (GenBank No. AF325969) and the plants from Chiapas (AF325970) have confirmed that the Chiapan population is A. hondurense and not A. nigrum. An additional population of A. hondurense was discovered in Chiapas approximately 11 km west of Oxchuc near Route 186 (elevation 2160 m). Both of the Chiapan populations of A. hondurense were parasitizing Pinus tecunumanii(Schw.) Eguiluz et Perry. Specimens of A. hondurense from Chiapas were deposited at the Deaver Herbarium, Northern Arizona University, Flagstaff. This is the first report of A. hondurense in Mexico and extends its known distribution from northwestern Honduras (3) by approximately 500 km. Although A. hondurense has not been observed in the pine forests of Guatemala, it is probable that it also occurs there (1). References: (1) F. G. Hawksworth and D. Wiens. 1996. Dwarf Mistletoes: Biology, Pathology, and Systematics. USDA Agric. Handb. 709. (2) R. Mathiasen et al. Phytologia 36:211, 1998. (3) R. Mathiasen et al. Plant Dis. 84:372, 2000.