No abstract

The effects of specific functional groups of pollinators in the diversification of angiosperms are still to be elucidated. We investigated whether the pollination shifts or the specific association with hummingbirds affected the diversification of a highly diverse angiosperm lineage in the Neotropics. We reconstructed a phylogeny of 583 species from the Gesneriaceae family and detected diversification shifts through time, inferred the timing and amount of transitions among pollinator functional groups, and tested the association between hummingbird pollination and speciation and extinction rates. We identified a high frequency of pollinator transitions, including reversals to insect pollination. Diversification rates of the group increased through time since 25 Ma, coinciding with the evolution of hummingbird-adapted flowers and the arrival of hummingbirds in South America. We showed that plants pollinated by hummingbirds have a twofold higher speciation rate compared with plants pollinated by insects, and that transitions among functional groups of pollinators had little impact on the diversification process. We demonstrated that floral specialization on hummingbirds for pollination has triggered rapid diversification in the Gesneriaceae family since the Early Miocene, and that it represents one of the oldest identified plant-hummingbird associations. Biotic drivers of plant diversification in the Neotropics could be more related to this specific type of pollinator (hummingbirds) than to shifts among different functional groups of pollinators.

New World monkeys (platyrrhines) are one of the most diverse groups of primates, occupying today a wide range of ecosystems in the American tropics and exhibiting large variations in ecology, morphology, and behavior. Although the relationships among the almost 200 living species are relatively well understood, we lack robust estimates of the timing of origin, ancestral morphology, and geographic range evolution of the clade. Here we integrate paleontological and molecular evidence to assess the evolutionary dynamics of extinct and extant platyrrhines. We develop novel analytical frameworks to infer the evolution of body mass, changes in latitudinal ranges through time, and species diversification rates using a phylogenetic tree of living and fossil taxa. Our results show that platyrrhines originated 5-10 million years earlier than previously assumed, dating back to the Middle Eocene. The estimated ancestral platyrrhine was small - weighing 0.4 kg - and matched the size of their presumed African ancestors. As the three platyrrhine families diverged, we recover a rapid change in body mass range. During the Miocene Climatic Optimum, fossil diversity peaked and platyrrhines reached their widest latitudinal range, expanding as far South as Patagonia, favored by warm and humid climate and the lower elevation of the Andes. Finally, global cooling and aridification after the middle Miocene triggered a geographic contraction of New World monkeys and increased their extinction rates. These results unveil the full evolutionary trajectory of an iconic and ecologically important radiation of monkeys and showcase the necessity of integrating fossil and molecular data for reliably estimating evolutionary rates and trends.

Cannabis sativa has long been an important source of fiber extracted from hemp and both medicinal and recreational drugs based on cannabinoid compounds. Here, we investigated its poorly known domestication history using whole-genome resequencing of 110 accessions from worldwide origins. We show that C. sativa was first domesticated in early Neolithic times in East Asia and that all current hemp and drug cultivars diverged from an ancestral gene pool currently represented by feral plants and landraces in China. We identified candidate genes associated with traits differentiating hemp and drug cultivars, including branching pattern and cellulose/lignin biosynthesis. We also found evidence for loss of function of genes involved in the synthesis of the two major biochemically competing cannabinoids during selection for increased fiber production or psychoactive properties. Our results provide a unique global view of the domestication of C. sativa and offer valuable genomic resources for ongoing functional and molecular breeding research.

Crop wild relatives that have experienced multiple and independent domestication events provide an excellent model for understanding adaptation processes in crop populations and a first and relevant aspect to investigate is the geographic origin of landraces. The aim of this research was to establish the origin of Mesoamerican and Andean Lima bean (Phaseolus lunatus L.) landraces by analyzing chloroplast DNA and ITS polymorphisms in a sample of 59 wild and 50 landrace accessions. According to seed size, genetic distance analyses, and haplotype networks, at least two independent domestication events are proposed. The first one would have taken place in the Andes of southern Ecuador–northwestern Peru and would have given rise to the large‐seeded landraces collectively known as the “Big Lima” cultivars. The second one would have taken place in central–western Mexico, more likely in the area to the north and northwest of the Isthmus of Tehuantepec. This event, along with post‐domestication migrations of landraces in South America, would have given rise to the great variety of small‐seeded Mesoamerican landraces that exist today. We did not find any evidence supporting the existence of two discrete groups within Mesoamerican landraces that might correspond to the previously proposed “Sieva” and “Potato” cultigroups. A severe reduction in genetic diversity because of domestication, known as the “founder effect”, was detected, which may have implications for the conservation of genetic resources in this species.

Phaseolus lunatus L., Lima bean, has been domesticated at least twice in the Americas, once in the Andean region and at another time in Mesoamerica; however, the domestication history of this crop in the latter region remains unclear. In this study, a phylogeographic analysis of DNA polymorphisms in the internal transcribed spacer (ITS) region of the ribosomal DNA from a collection of wild and domesticated accessions was applied to establish where and how many times in Mesoamerica Lima bean was domesticated. The results showed evidence for two wild Mesoamerican gene pools with contrasting geographical distributions. While the MI gene pool occurs in central western Mexico, including the Pacific coastal range, the MII gene pool is widespread and occurs toward the Gulf of Mexico, the Yucatan peninsula, and Central and South America. In a cluster analysis, all Mesoamerican landraces clustered together with wild accessions from the MI gene pool (L haplotype) suggesting a unique domestication event in central western Mexico. The most likely domestication region is an area of the states of Nayarit–Jalisco or Guerrero–Oaxaca and not areas such as the Peninsula of Yucatan where the crop is currently widespread and diverse. A strong founder effect due to domestication was quantified and several recently diversified haplotypes were identified. A hypothesis about possible dispersal routes of the crop within Mesoamerica is proposed as well as an apparent late adoption of the crop into the milpa system.

No abstract

The adaptive radiation of Bromeliaceae (pineapple family) is one of the most diverse among Neotropical flowering plants. Diversification in this group was facilitated by shifts in several adaptive traits or "key innovations" including the transition from C 3 to CAM photosynthesis associated with xeric (heat/drought) adaptation. We used phylogenomic approaches, complemented by differential gene expression (RNA-seq) and targeted metabolite profiling, to address the mechanisms of C 3 /CAM evolution in the extremely species-rich bromeliad genus, Tillandsia, and related taxa. Evolutionary analyses of whole-genome sequencing and RNA-seq data suggest that evolution of CAM is associated with coincident changes to different pathways mediating xeric adaptation in this group. At the molecular level, C 3 /CAM shifts were accompanied by gene expansion of XAP5 CIRCADIAN TIMEKEEPER homologs, a regulator involved in sugar-and light-dependent regulation of growth and development. Our analyses also support the reprogramming of abscisic acid-related gene expression via differential expression of ABF2/ABF3 transcription factor homologs, and adaptive sequence evolution of an ENO2/LOS2 enolase homolog, effectively tying carbohydrate flux to abscisic acid-mediated abiotic stress response. By pinpointing different regulators of overlapping molecular responses, our results suggest plausible mechanistic explanations for the repeated evolution of correlated adaptive traits seen in a textbook example of an adaptive radiation.