Genome Skimming Reveals Widespread Hybridization in a Neotropical Flowering Plant Radiation

The tropics hold at least an order of magnitude greater plant diversity than the temperate zone, yet the reasons for this difference are still subject to debate. Much of tropical plant diversity is in highly speciose genera and understanding the drivers of such high species richness will help solve the tropical diversity enigma. Hybridization has recently been shown to underlie many adaptive radiations, but its role in the evolution of speciose tropical plant genera has received little attention. Here, we address this topic in the hyperdiverse Bromeliaceae genus Vriesea using genome skimming data covering the three genomic compartments. We find evidence for hybridization in ca. 11% of the species in our dataset, both within the genus and between Vriesea and other genera, which is commensurate with hybridization underlying the hyperdiversity of Vriesea, and potentially other genera in Tillandsioideae. While additional genomic research will be needed to further clarify the contribution of hybridization to the rapid diversification of Vriesea, our study provides an important first data point suggesting its importance to the evolution of tropical plant diversity.

Vertical stratification of Diptera abundance and species richness in an Amazonian tropical forest

Measuring species richness of tropical forests is a major challenge. Such measurement is a key information in many senses, from an evolutionary perspective to conservation of threatened, fragile habitats. Data has gradually shown that the canopy of tropical forest is a hugely complex component of the forest, but a precise assessment of the diversity of megadiverse groups in the canopy is still wanting. We collected large samples of insects were along a period of two weeks using 6-meter Gressitt-style Malaise traps set at five heights on a metal tower in a tropical forest north of Manaus—one trap at the ground level, one trap above the canopy (32 m) and three traps at intermediate levels (8, 16 and 24 m). The samples contained 37,778 specimens belonging to 18 order of insects. Fifty-seven families of flies (Diptera) were found, 39 of which were identified to 368 genera and 856 species. The species of these 39 families of flies fit into eight patterns of vertical distribution of abundance and species richness of the fauna, with patterns of one or two peaks of species at different levels. A total of 527 (61.6%) of the 856 fly species recognized in the samples were not collected at the ground level. The canopy-associated species of Diptera showed a high species richness and a relatively low abundance indicating that they represent vulnerable components of tropical diversity. The biology of the flies families and genera we collected in the canopy suggest that the evolution of flies went through a unique process: independent clades of Diptera explored in different ways the resources originated along the very evolution of the angiosperm forest canopy along the early Cenozoic. Unlike other primarily phytophagous groups of insects, flies radiated into a large array of biologies associated with the canopies: parasitoids, hematophagous, phytosaprophagous, kleptoparasites, sap feeders, gall-makers etc. The results only stress the need of additional strategies to protect this diversity.

Past and future decline of tropical pelagic biodiversity

A major research question concerning global pelagic biodiversity remains unanswered: when did the apparent tropical biodiversity depression (i.e., bimodality of latitudinal diversity gradient [LDG]) begin? The bimodal LDG may be a consequence of recent ocean warming or of deep-time evolutionary speciation and extinction processes. Using rich fossil datasets of planktonic foraminifers, we show here that a unimodal (or only weakly bimodal) diversity gradient, with a plateau in the tropics, occurred during the last ice age and has since then developed into a bimodal gradient through species distribution shifts driven by postglacial ocean warming. The bimodal LDG likely emerged before the Anthropocene and industrialization, and perhaps ∼15,000 y ago, indicating a strong environmental control of tropical diversity even before the start of anthropogenic warming. However, our model projections suggest that future anthropogenic warming further diminishes tropical pelagic diversity to a level not seen in millions of years.

Modeling Tropical Diversity in the Undergraduate Classroom: Novel Curriculum to Engage Students in Authentic Scientific Practices

A feature of science is its production of evidence-based explanations. Scientific models can both provide causal explanations and be predictive of natural phenomena. Modeling-based inquiry (MBI) is a pedagogical strategy that promotes students' deep learning about phenomena via engagement in authentic scientific practices. Some university instructors have begun to facilitate MBI in their courses, notably those aimed at aspiring K–12 science educators who, per the Next Generation Science Standards, are encouraged to implement MBI. Yet exploration of curriculum and teaching with MBI in postsecondary environments is scarce. We detail a novel MBI curriculum implemented in a postsecondary ecology course that included students interested in future careers in education. The curriculum engages students in modeling why there is greater biological diversity in tropical than in temperate regions. This biological phenomenon continues to be of great interest to the scientific community. We briefly detail how the curriculum impacted students' understanding of participation in aspects of scientific practices and their comfort with facilitating MBI.

Loss of dominant caterpillar genera in a protected tropical forest

ABSTRACTReports of biodiversity loss have increasingly focused on the abundance and diversity of insects, but it is still unclear if substantive insect diversity losses are occurring in intact low-latitude forests. We collected 22 years of plant-caterpillar-parasitoid data in a protected tropical forest and found reductions in diversity and density of these insects that appear to be partly driven by a changing climate and weather anomalies. The decline in parasitism represents a reduction in an important ecosystem service: enemy control of primary consumers. The consequences of these changes are in many cases irreversible and are likely to be mirrored in nearby forests; overall declines in the region will have negative consequences for surrounding agriculture. The decline of important tropical taxa and associated ecosystem function illuminates the consequences of numerous threats to global insect diversity and provides additional impetus for research on tropical diversity.

Vertical differentiation in tropical forest butterflies: a novel mechanism generating insect diversity?

Many tropical fruit-feeding nymphalid butterflies are associated with either the forest canopy or the understorey; however, the exceptions offer insights into the origins of tropical diversity. As it occurs in both habitats of tropical forests in Ecuador and Peru, Archaeoprepona demophon is one such exception. We compared patterns of occurrence of A. demophon in the canopy and understorey and population genomic variation for evidence of ecological and genetic differentiation between habitats. We found that butterfly occurrences in the canopy were largely uncorrelated with occurrences in the understorey at both localities, indicating independent demographic patterns in the two habitats. We also documented modest, significant genome-level differentiation at both localities. Genetic differentiation between habitat types (separated by approx. 20 m in elevation) was comparable to levels of differentiation between sampling locations (approx. 1500 km). We conclude that canopy and understorey populations of A. demophon represent incipient independent evolutionary units. These findings support the hypothesis that divergence between canopy and understorey-associated populations might be a mechanism generating insect diversity in the tropics.