Solitary, dioecious, and mostly endemic to Andean cloud forests, wax palms (Ceroxylon Bonpl. ex DC. spp.) are currently under worrisome conservation status. The establishment of management plans for their dwindling populations rely on detailed biological data, including their reproductive ecology. As in the case of numerous other Neotropical palm taxa, small beetles are assumed to be selective pollinators of wax palms, but their identity and relevance in successful fruit yield were unknown. During three consecutive reproductive seasons we collected data on population phenology and reproductive and floral biology of three syntopic species of wax palms native to the Colombian Andes. We also determined the composition of the associated flower-visiting entomofauna, quantifying the extent of the role of individual species as effective pollinators through standardized value indexes that take into consideration abundance, constancy, and pollen transport efficiency. The studied populations of C. parvifrons (Engel) H. Wendl., C. ventricosum Burret, and C. vogelianum (Engel) H. Wendl. exhibit seasonal reproductive cycles with marked temporal patterns of flower and fruit production. The composition of the associated flower-visiting entomofauna, comprised by ca. 50 morphotypes, was constant across flowering seasons and differed only marginally among species. Nonetheless, a fraction of the insect species associated with pistillate inflorescences actually carried pollen, and calculated pollinator importance indexes demonstrated that one insect species alone, Mystrops rotundula Sharp, accounted for 94%–99% of the effective pollination services for all three species of wax palms. The sequential asynchronous flowering of C. parvifrons, C. ventricosum, and C. vogelianum provides an abundant and constant supply of pollen, pivotal for the maintenance of large populations of their shared pollinators, a cooperative strategy proven effective by high fruit yield rates (up to 79%). Reproductive success might be compromised for all species by the population decline of one of them, as it would tamper with the temporal orchestration of pollen offer.

The phylogenetic position of Rangaeris (Schltr.) Summerh. has been one of the most problematic issues of angraecoid orchid taxonomy. A recently published phylogenetic tree with nearly comprehensive taxon sampling of African angraecoid orchids suggested that this genus was polyphyletic, as its species appear nested within different subclades of the Cyrtorchis–Tridactyle clade. However, the lack of DNA data for the generic type, R. muscicola (Rchb. f.) Summerh., and for the little-known species R. longicaudata (Rolfe) Summerh. and R. trilobata Summerh., has precluded an integrative reappraisal of the delimitation of this genus. Here we present the results of a new phylogenetic analysis of one nuclear (ITS) and five plastid markers (matK, rps16, trnC-petN intergenic spacer, trnL-trnF intergenic spacer, ycf1) for all six species of Rangaeris, including those recently transferred to Podangis Schltr. and Ypsilopus Summerh., together with a representative sampling of 14 other species of the genera Cyrtorchis Schltr., Listrostachys Rchb. f., Plectrelminthus Raf., Summerhayesia P. J. Cribb, Tridactyle Schltr., and Ypsilopus. Based on molecular and morphological evidence, R. muscicola is transferred to Podangis, where Rangaeris is reduced to the rank of section. In addition, R. longicaudata and R. trilobata are each moved to new monotypic genera, Planetangis Stévart & Farminhão and Aziza Farminhão & D'haijère, respectively. An identification key for all genera of the Cyrtorchis–Tridactyle clade is presented, together with one for the three species of recircumscribed Podangis. Finally, taxonomic accounts of the new genera are presented, including amended descriptions, illustrations, distribution maps, and preliminary conservation status assessments of their species.

Lamiids, a clade composed of approximately 15% of all flowering plants, contains more than 50,000 species dispersed across 49 families and eight orders (APG IV, 2016). This paper is the eighth in a series that analyzes pollen characters across angiosperms. We reconstructed a maximum likelihood tree based on the most recent phylogenetic studies for the Lamiids, comprising 150 terminal genera (including six outgroups) and covering all eight orders and 49 families within the clade. To illustrate pollen diversity across the Lamiids, pollen grains from 22 species (22 genera in 14 families) were imaged under light, scanning, and transmission electron microscopy. Eighteen pollen characters that were documented from previous publications, websites, and our new observations were coded and optimized onto the reconstructed phylogenetic tree using Fitch parsimony, maximum likelihood, and hierarchical Bayesian analysis. Pollen morphology of the Lamiids is highly diverse, particularly in shape class, pollen size, aperture number, endoaperture shape, supratectal element shape, and tectum sculpture. In addition, some genera show relatively high infrageneric pollen variation within the Lamiids: i.e., Coffea L., Jacquemontia Choisy, Justicia L., Pedicularis L., Psychotria L. nom. cons., Sesamum L., Stachytarpheta Vahl, and Veronica L. The plesiomorphic states for 16 pollen characters were inferred unambiguously, and 10 of them displayed consistent plesiomorphic states under all optimization methods. Seventy-one lineages at or above the family level are characterized by pollen character state transitions. We identified diagnostic character states for monophyletic clades and explored palynological evidence to shed light on unresolved relationships. For example, palynological evidence supports the monophyly of Garryales and Metteniusaceae, and sister relationships between Icacinaceae and Oncothecaceae, as well as between Vahliales and Solanales. The evolutionary patterns of pollen morphology found in this study reconfirm several previously postulated evolutionary trends, which include an increase in aperture number, a transition from equatorially arranged apertures to globally distributed ones, and an increase in exine ornamentation complexity. Furthermore, there is a significant correlation between pollen characters and a number of ecological factors, e.g., pollen size and pollination type, pollen ornamentation and pollination type, and shape class and plant growth form. Our results provide insight into the ecological, environmental, and evolutionary mechanisms driving pollen character state changes in the Lamiids.

Over the past five decades, many studies have examined the Janzen-Connell hypothesis, which posits that host-specific natural enemies, such as insect herbivores and fungal pathogens, promote plant species coexistence by providing a recruitment advantage to rare plant species. Recently, researchers have been exploring new and exciting angles on plant-enemy interactions that have yielded novel insights into this long-standing hypothesis. Here, we highlight some empirical advances in our understanding of plant-enemy interactions in tropical forests, including improved understanding of variation in plant species' susceptibility to enemy effects, as well as insect and pathogen host ranges. We then review recent advances in related ecological theory. These theoretical studies have confirmed that specialist natural enemies can promote tree diversity. However, they have also shown that the impact of natural enemies may be weakened, or that natural enemies could even cause species exclusion, depending on enemy host range, the spatial extent of enemy effects, and variation among plant species in seed dispersal or enemy susceptibility. Finally, we end by discussing how human impacts on tropical forests, such as fragmentation, hunting, and climate change, may alter the plant-enemy interactions that contribute to tropical forest diversity.

A 370,000-year paleoecological history of fire spanning four glacial cycles provides evidence of plant migration in response to Andean climate change. Charcoal, an indicator of fire, is only occasionally observed in this record, whereas it is ubiquitous in Holocene-aged Andean records. Fire is a transformative agent in Amazonian and Andean vegetation but is shown to be rare in nature. As humans promote fire, fire-free areas become microrefugia for fire-sensitive species. A distinction is drawn between microrefugia resulting from fire-free zones and those caused by unusual climatic conditions. The importance of this distinction lies in the lack of warmer-than-modern microrefugia aiding upslope migration in response to warming, whereas fire-free microrefugia support tree species above modern tree line or in areas of Amazonia least used by humans. The synergy between fire, deforestation, and climate change could promote a state-change in the ecosystem, one where new microrefugia would be needed to maintain biodiversity. Past tipping points are identified to have occurred within ca. 1°C–1.5°C of modern conditions. The recent climatic instability in both Amazonia and the Andes is viewed in the context of ecological flickering, while the drought-induced and fire-induced tree mortality are aspects of critical slowing down; both possibly portending an imminent tipping point.

The Neotropics are the most species-rich area of the planet. Understanding the origin and maintenance of this diversity is an important goal of ecology and evolutionary biology. Success in this endeavor relies heavily on the past work of taxonomists who have collected specimens and produced the floras and monographs that constitute the foundation for the study of plant diversity. To illustrate this, we visualize collecting efforts through time and identify the importance of past taxonomic and collection efforts in generating the bulk of specimen data that broad-scale analyses rely on today. To demonstrate the importance of taxonomy for the study of Neotropical biodiversity, we showcase selected plant groups in which in-depth taxonomic understanding has facilitated exciting evolutionary and ecological research and highlight the teams of scientists who have built on the legacy of Alwyn Gentry, one of the most prolific taxonomists of the late 20th century. We also discuss challenges faced by taxonomists, including perceived subjectivity, difficulty in measuring impact, and the need to become more interdisciplinary. We end with potential solutions going forward, including integration of taxonomists in interdisciplinary research, advocacy for continued collection efforts, increased funding for alpha taxonomic research that is performed with increasingly replicable methodology, and explicit decolonization efforts to increase inclusivity and equity in the field of taxonomy. Acknowledging the central role of taxonomy and taxonomists is essential to accurately and completely describe Neotropical biodiversity patterns in an age of unprecedented extinction risk and conservation need.