Family Legacy: Depicting Diversity-Elevation Relationships of Tropical Tree Communities

Unveiling the ecological processes driving diversity and its relationship to the environment remains a central goal in ecological studies. Here, we investigated the elevation effect on plant diversity patterns of tropical rainforests, using beta-, phylogenetic and alpha diversities. To do so, we compiled a forest dataset with 22,236 trees (DBH ≥ 4.8 cm) from 17 plots of 1 ha each along an elevational gradient (0 – 1,200 m a.s.l) in the Atlantic Forest of Southeastern Brazil. We found high phylogenetic and species rates of turnover – beta-diversity - along the elevational gradient. Alpha phylodiversity showed a monotonic decrease with increasing elevation, including or not fern species (a distantly related clade usually ignored in tropical ecology studies), while the phylogenetic structure was highly affected by the inclusion of fern trees. Species diversity showed a unimodal pattern for the whole community, and different patterns for the richest families. The diversity pattern of the whole community emerges from differences among species distribution of the richest families, while phylogenetic diversity seems to be gradually filtered by elevation. At intermediate elevations, higher species diversification within families might have led to different strategies and cooccurrence in tropical rainforests. We also showed that intricate effects of elevation in species assemblages can be better assessed using both ecological and evolutionary approaches, stressing the importance of species selection in diversity analyzes. Finally, we demonstrate that elevation has different effects on the species distributions of the richest families and warn that these differences should be considered in conservation planning.

Vertical profiles of leaf photosynthesis and leaf traits and soil nutrients in two tropical rainforests in French Guiana before and after a 3-year nitrogen and phosphorus addition experiment

Terrestrial biosphere models typically use the biochemical model of Farquhar, von Caemmerer, and Berry (1980) to simulate photosynthesis, which requires accurate values of photosynthetic capacity of different biomes. However, data on tropical forests are sparse and highly variable due to the high species diversity, and it is still highly uncertain how these tropical forests respond to nutrient limitation in terms of C uptake. Tropical forests often grow on soils low in phosphorus (P) and are, in general, assumed to be P rather than nitrogen (N) limited. However, the relevance of P as a control of photosynthetic capacity is still debated. Here, we provide a comprehensive dataset of vertical profiles of photosynthetic capacity and important leaf traits, including leaf N and P concentrations, from two 3-year, large-scale nutrient addition experiments conducted in two tropical rainforests in French Guiana. These data present a unique source of information to further improve model representations of the roles of N, P, and other leaf nutrients in photosynthesis in tropical forests. To further facilitate the use of our data in syntheses and model studies, we provide an elaborate list of ancillary data, including important soil properties and nutrients, along with the leaf data. As environmental drivers are key to improve our understanding of carbon (C) and nutrient cycle interactions, this comprehensive dataset will aid to further enhance our understanding of how nutrient availability interacts with C uptake in tropical forests. The data are available at https://doi.org/10.5281/zenodo.5638236 (Verryckt, 2021).

Enzymatic Bioprospecting of Fungi Isolated from a Tropical Rainforest in Mexico

The humid tropical environment provides an ideal place for developing a high diversity of plants; this is why it is an interesting site for the enzymatic bioprospecting of fungi that are responsible for the recycling of organic matter in an efficient and accelerated way and whose enzymes could have multiple biotechnological applications. For this study, 1250 isolates of macroscopic and microscopic fungal morphotypes were collected from soil, leaf litter, and wood. One hundred and fifty strains (50 from each source) were selected for the enzymatic screening. From the first phase, 51 strains with positive activity for laccase, protease, amylase, xylanase, and lipase enzymes were evaluated, of which 20 were isolated from leaf litter, 18 from the soil, and 13 from wood. The 10 best strains were selected for the enzymatic quantification, considering the potency index and the production of at least two enzymes. High laccase activity was detected for Trametes villosa FE35 and Marasmius sp. CE25 (1179 and 710.66 U/mg, respectively), while Daedalea flavida PE47 showed laccase (521.85 U/mg) and protease activities (80.66 U/mg). Fusarium spp. PH79 and FS400 strains had amylase (14.0 U/mg, 49.23 U/mg) and xylanase activities (40.05 U/mg, 36.03 U/mg) respectively. These results confirm the enzymatic potential of fungi that inhabit little-explored tropical rainforests with applications in industry.

From Patagonia to Indonesia: plant fossils highlight West Gondwanan legacy in the Malesian flora

Rainforests with the chinquapin Castanopsis and the yellowwood conifer Dacrycarpus occur today throughout Indonesia and the larger Malesian ecoregion, but they represent, in part, a history of survival stretching tens of millions of years and thousands of kilometers to the palaeo-Antarctic. Unlike New World and African tropical rainforests, the Malesian flora’s history is closely tied to tectonic introductions from exotic terranes, and thus, much palaeobotanical data about the origins of the Malesian rainforest comes from those terranes. For example, South America, Antarctica, and Australia remained adjacent until the Eocene final separation of Gondwana, and warm climates promoted high-latitude dispersals among those landmasses. Australia’s subsequent northward movement led to the late Oligocene Sahul-Sunda collision and the uplift of New Guinea, allowing the introductions into Malesia of survivor taxa that were once widespread in mesic Gondwanan rainforests. In Patagonian Argentina, the prolific Laguna del Hunco (52.2 Ma) site preserves abundant and well-preserved fossils of an unexpectedly large number of lineages whose living relatives characteristically associate in perhumid, lower montane “oak-laurel” rainforests of Malesia, especially in New Guinea. These taxa include the angiosperms Castanopsis (Fagaceae), Gymnostoma (rhu, Casuarinaceae), Alatonucula (extinct engelhardioid Juglandaceae), Eucalyptus (gums, Myrtaceae), Ceratopetalum (coachwood, Cunoniaceae), Lauraceae (laurel family), and Ripogonum (supplejack, Ripogonaceae); conifers in Cupressaceae (cypress family: Papuacedrus), Araucariaceae (dammars and relatives: Agathis and Araucaria Section Eutacta), and Podocarpaceae (yellowwoods: Dacrycarpus, Podocarpus, and a species similar to Phyllocladus); and the fern Todea (king fern, Osmundaceae). Many of these records are the only occurrences of the respective taxa in South America, living or fossil, vastly extending their past ranges and thus the biogeographic history of part of the Malesian mountain flora. The living-fossil taxa inhabit, and several dominate, critical watershed areas of high endemism and biodiversity in Malesia’s endangered tropical-montane rainforests. In Malesia itself, there have been very few Cenozoic palaeobotanical investigations for about a century or more. To remedy this situation and improve understanding of the evolution of the Malesian flora in situ, we have begun palaeobotanical fieldwork in collaboration with Professor Yahdi Zaim and ITB, along with international colleagues. So far, we have discovered several promising new fossil sites in the Eocene-Oligocene of West Sumatra (Sangkarewang and Sawahlunto formations) and South Kalimantan (Tanjung Formation), and I will report preliminary observations.

Effects of tropical rainforest conversion to rubber plantation on soil quality in Hainan Island, China

Land-use changes can alter soil properties and thus affect soil quality. Our understanding of how forest conversion (from tropical rainforest to rubber plantations) affects soil properties and soil quality is limited. An ideal testing ground for analyzing such land-use change and its impacts is Hainan Island, the largest tropical island in China. Based on 21 soil physicochemical and biological properties, a soil quality index (SQI) employed principal component analysis to assess soil quality changes from the conversion of tropical rainforests to rubber plantations. The results showed that (i) soil available potassium, available phosphorus, microbial biomass carbon, cellulose decomposition, acid phosphatase, and urease were vital soil properties for soil quality assessment on Hainan Island. (ii) The SQI of rubber plantations decreased by 26.48 % compared to tropical rainforests, while four investigated soil properties (soil pH, total phosphorus, cellulose decomposition, and actinomyces) increased. (iii) The SQI of both the tropical rainforests and rubber plantations showed significant spatial differences, which, under tropical rainforests, was more sensitive to seasonal changes than those under rubber plantations. (iv) Structural equation modeling suggested that forest conversion directly impacted soil quality and, indirectly impacted soil qualities' spatial variation by their interaction with soil types and geographical positions. Overall, though the conversion of tropical rainforest to rubber plantation did not decrease all soil properties, the tropical rainforest with its high soil quality should be protected.

Cryptogamic organisms are a substantial source and sink for volatile organic compounds in the Amazon region

Cryptogamic organisms such as bryophytes and lichens cover most surfaces within tropical forests, yet their impact on the emission of biogenic volatile organic compounds is unknown. These compounds can strongly influence atmospheric oxidant levels as well as secondary organic aerosol concentrations, and forest canopy leaves have been considered the dominant source of these emissions. Here we present cuvette flux measurements, made in the Amazon rainforest between 2016–2018, and show that common bryophytes emit large quantities of highly reactive sesquiterpenoids and that widespread lichens strongly uptake atmospheric oxidation products. A spatial upscaling approach revealed that cryptogamic organisms emit sesquiterpenoids in quantities comparable to current canopy attributed estimates, and take up atmospheric oxidation products at rates comparable to hydroxyl radical chemistry. We conclude that cryptogamic organisms play an important and hitherto overlooked role in atmospheric chemistry above and within tropical rainforests.

Why Did the Bee Eat the Chicken? Symbiont Gain, Loss, and Retention in the Vulture Bee Microbiome

When asked where to find bees, people often picture fields of wildflowers. While true for almost all species, there is a group of specialized bees, also known as the vulture bees, that instead can be found slicing chunks of meat from carcasses in tropical rainforests.

Ceratozamia dominguezii (Zamiaceae): A New Cycad Species from Southeastern Mexico

Ceratozamia dominguezii (Zamiaceae), a new species endemic to the lowland karstic tropical rainforests of southeastern Veracruz, Mexico, is described. The new species is part of the C. robusta species complex, a group of closely related species that share unique characteristics in the genus, such as robust trunks, large strobili, and long leaves. Compared with the other species in the complex (i.e., C. robusta, C. leptoceras, C. aurantiaca and C. subroseophylla), C. dominguezii has the longest rachides, and is characterized by having papyraceous leaflets, a unique caramel color in emerging leaves, and a dark-violet color in the central portion of distal faces of male and female sporophylls. Ceratozamia dominguezii occurs within the Uxpanapa floristic refuge, which is hypothesized to have sheltered a numerous group of tropical elements during the Neogene glaciations. The recognition of C. dominguezii contributes to clarifying the present diversity of cycads in the genus Ceratozamia, and adds discussion on the role of floristic refugia in the divergence of Neotropical plants in Mexico.