Spiny but photogenic: Amateur sightings complement herbarium specimens to reveal the bioregions of cacti.

PREMISE: Cacti are characteristic elements of the Neotropical flora and of major interest for biogeographic, evolutionary, and ecological studies. We tested global biogeographic boundaries for Neotropical Cactaceae using specimen-based occurrences, coupled with data from visual observations, as a means to tackle the known collection biases in the family. METHODS: Species richness and record density were assessed for preserved specimens and human observations, and a bioregional scheme tailored to Cactaceae was produced using the interactive web application Infomap Bioregions, based on data from 261,272 point records cleaned through automated and manual steps. RESULTS: We found that areas in Mexico and southwestern USA, in eastern Brazil, and along the Andean region have the greatest density of records and the highest species richness. Human observations complement information from preserved specimens substantially, especially along the Andes. We propose 24 cactus bioregions, among which the most species-rich are northern Mexico/southwestern USA, central Mexico, southern central Mexico, Central America, Mexican Pacific coast, central and southern Andes, northwestern Mexico/extreme southwestern USA, southwestern Bolivia, northeastern Brazil, and Mexico/Baja California. CONCLUSIONS: The bioregionalization proposed shows biogeographic boundaries specific to cacti and can thereby aid further evolutionary, biogeographic, and ecological studies by providing a validated framework for further analyses. This classification builds upon, and is distinctive from, other expert-derived regionalization schemes for other taxa. Our results showcase how observation data, including citizen-science records, can complement traditional specimen-based data for biogeographic research, particularly for taxa with specific specimen collection and preservation challenges and those that are threatened or internationally protected.

Amazonia is the primary source of Neotropical biodiversity.

The American tropics (the Neotropics) are the most species-rich realm on Earth, and for centuries, scientists have attempted to understand the origins and evolution of their biodiversity. It is now clear that different regions and taxonomic groups have responded differently to geological and climatic changes. However, we still lack a basic understanding of how Neotropical biodiversity was assembled over evolutionary timescales. Here we infer the timing and origin of the living biota in all major Neotropical regions by performing a cross-taxonomic biogeographic analysis based on 4,450 species from six major clades across the tree of life (angiosperms, birds, ferns, frogs, mammals, and squamates), and integrate >1.3 million species occurrences with large-scale phylogenies. We report an unprecedented level of biotic interchange among all Neotropical regions, totaling 4,525 dispersal events. About half of these events involved transitions between major environmental types, with a predominant directionality from forested to open biomes. For all taxonomic groups surveyed here, Amazonia is the primary source of Neotropical diversity, providing >2,800 lineages to other regions. Most of these dispersal events were to Mesoamerica (∼1,500 lineages), followed by dispersals into open regions of northern South America and the Cerrado and Chaco biomes. Biotic interchange has taken place for >60 million years and generally increased toward the present. The total amount of time lineages spend in a region appears to be the strongest predictor of migration events. These results demonstrate the complex origin of tropical ecosystems and the key role of biotic interchange for the assembly of regional biotas.

Correct names for some of the closest relatives of Carica papaya: A review of the Mexican/Guatemalan genera Jarilla and Horovitzia.

Using molecular data, we recently showed that Carica papaya L. is sister to a Mexican/Guatemalan clade of two genera, Jarilla Rusby with three species and Horovitzia V.M. Badillo with one. These species are herbs or thin-stemmed trees and may be of interest for future genomics-enabled papaya breeding. Here we clarify the correct names of Jarilla heterophylla (Cerv. ex La Llave) Rusby and Jarilla caudata (Brandegee) Standl., which were confused in a recent systematic treatment of Jarilla (McVaugh 2001). We designate epitypes for both, provide weblinks to type specimens, a key to the species of Jarilla and Horovitzia, and notes on their habitats and distribution.

A dated phylogeny of the papaya family (Caricaceae) reveals the crop's closest relatives and the family's biogeographic history.

Papaya (Carica papaya) is a crop of great economic importance, and the species was among the first plants to have its genome sequenced. However, there has never been a complete species-level phylogeny for the Caricaceae, and the crop's closest relatives are therefore unknown. We investigated the evolution of the Caricaceae based on sequences from all species and genera, the monospecific Carica, African Cylicomorpha with two species, South American Jacaratia and Vasconcellea with together c. 28 species, and Mexican/Guatemalan Jarilla and Horovitzia with four species. Most Caricaceae are trees or shrubs; the species of Jarilla, however, are herbaceous. We generated a matrix of 4711 nuclear and plastid DNA characters and used maximum likelihood (ML) and Bayesian analysis to infer species relationships, rooting trees on the Moringaceae. Divergence times were estimated under relaxed and strict molecular clocks, using different subsets of the data. Ancestral area reconstruction relied on a ML approach. The deepest split in the Caricaceae occurred during the Late Eocene, when the ancestor of the Neotropical clade arrived from Africa. In South America, major diversification events coincide with the Miocene northern Andean uplift and the initial phase of the tectonic collision between South America and Panama resulting in the Panamanian land bridge. Carica papaya is sister to Jarilla/Horovitzia, and all three diverged from South American Caricaceae in the Oligocene, 27 (22-33) Ma ago, coincident with the early stages of the formation of the Panamanian Isthmus. The discovery that C. papaya is closest to a clade of herbaceous or thin-stemmed species has implications for plant breeders who have so far tried to cross papaya only with woody highland papayas (Vasconcellea).