Towards a species-level phylogeny for Neotropical Myrtaceae: Notes on topology and resources for future studies.

PREMISE: Increasingly complete phylogenies underpin studies in systematics, ecology, and evolution. Myrteae (Myrtaceae), with ~2700 species, is a key component of the exceptionally diverse Neotropical flora, but given its complicated taxonomy, automated assembling of molecular supermatrices from public databases often lead to unreliable topologies due to poor species identification. METHODS: Here, we build a taxonomically verified molecular supermatrix of Neotropical Myrteae by assembling 3909 published and 1004 unpublished sequences from two nuclear and seven plastid molecular markers. We infer a time-calibrated phylogenetic tree that covers 712 species of Myrteae (~28% of the total diversity in the clade) and evaluate geographic and taxonomic gaps in sampling. RESULTS: The tree inferred from the fully concatenated matrix mostly reflects the topology of the plastid data set and there is a moderate to strong incongruence between trees inferred from nuclear and plastid partitions. Large, species-rich genera are still the poorest sampled within the group. Eastern South America is the best-represented area in proportion to its species diversity, while Western Amazon, Mesoamerica, and the Caribbean are the least represented. CONCLUSIONS: We provide a time-calibrated tree that can be more reliably used to address finer-scale eco-evolutionary questions that involve this group in the Neotropics. Gaps to be filled by future studies include improving representation of taxa and areas that remain poorly sampled, investigating causes of conflict between nuclear and plastid partitions, and the role of hybridization and incomplete lineage sorting in relationships that are poorly supported.

Contrasting patterns of foraging behavior in neotropical stingless bees using pollen and honey metabarcoding.

Stingless bees are major flower visitors in the tropics, but their foraging preferences and behavior are still poorly understood. Studying stingless bee interactions with angiosperms is methodologically challenging due to the high tropical plant diversity and inaccessibility of upper canopy flowers in forested habitats. Pollen DNA metabarcoding offers an opportunity of assessing floral visitation efficiently and was applied here to understand stingless bee floral resources spectra and foraging behavior. We analyzed pollen and honey from nests of three distantly related stingless bee species, with different body size and social behavior: Melipona rufiventris, Scaptotrigona postica and Tetragonisca angustula. Simultaneously, we evaluate the local floristic components through seventeen rapid botanical surveys conducted at different distances from the nests. We discovered a broad set of explored floral sources, with 46.3 plant species per bee species in honey samples and 53.67 in pollen samples. Plant families Myrtaceae, Asteraceae, Euphorbiaceae, Melastomataceae and Malpighiaceae dominated the records, indicating stingless bee preferences for abundant resources that flowers of these families provide in the region. Results also reinforce the preference of stingless bees for forest trees, even if only available at long distances. Our high-resolution results encourage future bee-plant studies using pollen and honey metabarcoding in hyper-diverse tropical environments.

On the identity and typification of Solanum brasilianum Dunal (Solanaceae).

Solanum brasilianum Dunal was described by Dunal in 1813 with reference only to an illustration in an 18th century work by Leonard Plukenet. The plate is difficult to interpret and no explicitly related specimens were available so the name Solanum brasilianum has long been regarded as "unresolved" and has never been used. Material matching the Plukenet plate was discovered in the herbarium of the University of Oxford (OXF) by Stephen Harris during his study of the English privateer William Dampier's Brazilian collection. The specimen is referable to a common Brazilian Solanum that is a member of the Torva clade, Solanum paniculatum L., making Solanum brasilianum Dunal a heterotypic synonym. We lectotypify Solanum brasilianum here, and designate an epitype using the Dampier material from OXF.

Influence of biological and social-historical variables on the time taken to describe an angiosperm.

PREMISE OF THE STUDY: By convention, scientific naming of angiosperm species began in 1753; it is estimated that 10-20% of species remain undescribed. To complete this task before rare, undescribed species go extinct, a better understanding of the description process is needed. The South American Cerrado biodiversity hotspot was considered a suitable model due to a high diversity of plants, habitats, and social history of species description. METHODS: A randomized sample of 214 species (2% of the angiosperm flora) and 22 variables were analyzed using multivariate analyses and analysis of variance. KEY RESULTS: Plants with wide global distributions, recorded from many areas, and above 2.6 m were described significantly earlier than narrowly distributed, uncommon species of smaller stature. The beginning of the career of the botanist who first collected the species was highly significant, with an average delay between first collection and description of 29 yr, and between type collection and description 19 yr; standard deviations were high and rose over time. Over a third of first collections were not cited in descriptions. Trends such as scientific specialization and decline of undescribed species were highlighted. Descriptions that involved potential collaboration between collectors and authors were significantly slower than those that did not. CONCLUSIONS: Results support four recommendations to hasten discovery of new species: (1) preferential collecting of plants below 2.6 m, at least in the Cerrado; (2) access to undetermined material in herbaria; (3) fieldwork in areas where narrow-endemic species occur; (4) fieldwork by knowledgeable botanists followed by descriptive activity by the same.

Floral cost vs. floral display: Insights from the megadiverse Myrtales suggest that energetically expensive floral parts are less phylogenetically constrained.

PREMISE OF THE STUDY: Floral display describes the effect of flower size combined with the number of flowers per inflorescence. There is strong evidence that a floral-display trade-off operates under energetic constraint, with few-flowered inflorescences likely to have larger flowers than many-flowered inflorescences. Flower size can be estimated by different variables; thus, we propose that the variable for flower size that is most highly (negatively) correlated with the number of flowers per inflorescence will also be the best estimate of floral cost. Ranking the correlation with the phylogenetic signal of the variable can provide additional insight into the evolution of floral display. METHODS: The Myrtales were chosen as a model order based on age, worldwide distribution, and diversity of reproductive strategies. Ninety-nine species representing all families and one quarter of generic diversity across its geographic and ecological range were sampled to reconstruct a phylogeny based on rbcL and ndhF sequences. Correlation coefficients were calculated for flower size variables vs. the number of flowers per inflorescence. Phylogenetic signal was measured for all variables and for floral display. KEY RESULTS: Flowers per inflorescence showed significant negative correlation with the following flower size variables (weakest to strongest): filament length < anther size < flower depth < flower diameter. As the correlation of each character with number of flowers per inflorescence rose (suggesting increased cost), the values for phylogenetic signal diminished (suggesting less constraint). CONCLUSIONS: We conclude that energetically costly floral characters appear to be less phylogenetically constrained, while low-cost floral characters maintain higher levels of phylogenetic inertia.