Browsing by Autor "Kyle G. Dexter"

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Compositional response of Amazon forests to climate change
(Wiley, 2018) Adriane Esquivel‐Muelbert; Timothy R. Baker; Kyle G. Dexter; Simon L. Lewis; Roel Brienen; Ted R. Feldpausch; Jon Lloyd; Abel Monteagudo‐Mendoza; Luzmila Arroyo; Esteban Álvarez‐Dávila
Most of the planet's diversity is concentrated in the tropics, which includes many regions undergoing rapid climate change. Yet, while climate-induced biodiversity changes are widely documented elsewhere, few studies have addressed this issue for lowland tropical ecosystems. Here we investigate whether the floristic and functional composition of intact lowland Amazonian forests have been changing by evaluating records from 106 long-term inventory plots spanning 30 years. We analyse three traits that have been hypothesized to respond to different environmental drivers (increase in moisture stress and atmospheric CO<sub>2</sub> concentrations): maximum tree size, biogeographic water-deficit affiliation and wood density. Tree communities have become increasingly dominated by large-statured taxa, but to date there has been no detectable change in mean wood density or water deficit affiliation at the community level, despite most forest plots having experienced an intensification of the dry season. However, among newly recruited trees, dry-affiliated genera have become more abundant, while the mortality of wet-affiliated genera has increased in those plots where the dry season has intensified most. Thus, a slow shift to a more dry-affiliated Amazonia is underway, with changes in compositional dynamics (recruits and mortality) consistent with climate-change drivers, but yet to significantly impact whole-community composition. The Amazon observational record suggests that the increase in atmospheric CO<sub>2</sub> is driving a shift within tree communities to large-statured species and that climate changes to date will impact forest composition, but long generation times of tropical trees mean that biodiversity change is lagging behind climate change.
Evolutionary diversity in tropical tree communities peaks at intermediate precipitation
(Nature Portfolio, 2020) Danilo M. Neves; Kyle G. Dexter; Timothy R. Baker; Fernanda Coelho de Souza; Ary Teixeira de Oliveira‐Filho; Luciano Paganucci de Queiroz; Haroldo C. de Lima; Marcelo Fragomeni Simon; Gwilym P. Lewis; Ricardo A. Segovia
Evolutionary diversity is associated with wood productivity in Amazonian forests
(Nature Portfolio, 2019) Fernanda Coelho de Souza; Kyle G. Dexter; Oliver L. Phillips; R. Toby Pennington; Danilo M. Neves; Martin J. P. Sullivan; Esteban Álvarez‐Dávila; Atila Indalecio Marques Alves; Iêda Leão do Amaral; Ana Andrade
Evolutionary heritage influences Amazon tree ecology
(Royal Society, 2016) Fernanda Coelho de Souza; Kyle G. Dexter; Oliver L. Phillips; Roel J. W. Brienen; Jérôme Chave; David Galbraith; Gabriela López‐González; Abel Monteagudo Mendoza; R. Toby Pennington; Lourens Poorter
Lineages tend to retain ecological characteristics of their ancestors through time. However, for some traits, selection during evolutionary history may have also played a role in determining trait values. To address the relative importance of these processes requires large-scale quantification of traits and evolutionary relationships among species. The Amazonian tree flora comprises a high diversity of angiosperm lineages and species with widely differing life-history characteristics, providing an excellent system to investigate the combined influences of evolutionary heritage and selection in determining trait variation. We used trait data related to the major axes of life-history variation among tropical trees (e.g. growth and mortality rates) from 577 inventory plots in closed-canopy forest, mapped onto a phylogenetic hypothesis spanning more than 300 genera including all major angiosperm clades to test for evolutionary constraints on traits. We found significant phylogenetic signal (PS) for all traits, consistent with evolutionarily related genera having more similar characteristics than expected by chance. Although there is also evidence for repeated evolution of pioneer and shade tolerant life-history strategies within independent lineages, the existence of significant PS allows clearer predictions of the links between evolutionary diversity, ecosystem function and the response of tropical forests to global change.
Expanding tropical forest monitoring into Dry Forests: The DRYFLOR protocol for permanent plots
(Wiley, 2020) Peter W. Moonlight; Karina Banda; Oliver L. Phillips; Kyle G. Dexter; R. Toby Pennington; Timothy R. Baker; Haroldo Cavalcante de Lima; Laurie Fajardo; Roy González‐M.; Reynaldo Linares‐Palomino
Societal Impact Statement Understanding of tropical forests has been revolutionized by monitoring in permanent plots. Data from global plot networks have transformed our knowledge of forests’ diversity, function, contribution to global biogeochemical cycles, and sensitivity to climate change. Monitoring has thus far been concentrated in rain forests. Despite increasing appreciation of their threatened status, biodiversity, and importance to the global carbon cycle, monitoring in tropical dry forests is still in its infancy. We provide a protocol for permanent monitoring plots in tropical dry forests. Expanding monitoring into dry biomes is critical for overcoming the linked challenges of climate change, land use change, and the biodiversity crisis.
Floristics and biogeography of vegetation in seasonally dry tropical regions
(Commonwealth Forestry Association, 2015) Kyle G. Dexter; Barry Smart; Cristina Baldauf; Timothy R. Baker; Michael Balinga; Roel J. W. Brienen; Sophie Fauset; Ted R. Feldpausch; L. Ferreira-Da Silva; Jonathan Ilunga Muledi
To provide an inter-continental overview of the floristics and biogeography of drought-adapted tropical vegetation formations, we compileda dataset of inventory plots in South America (n=93), Africa (n=84), and Asia (n=92) from savannas (subject to fire), seasonally dry tropicalforests (not generally subject to fire), and moist forests (no fire). We analysed floristic similarity across vegetation formations within andbetween continents. Our dataset strongly suggests that different formations tend to be strongly clustered floristically by continent, and that among continents, superficially similar vegetation formations (e.g. savannas) are floristically highly dissimilar. Neotropical moist forest,savanna and seasonally dry tropical forest are floristically distinct, but elsewhere there is no clear floristic division of savanna and seasonallydry tropical forest, though moist and dry formations are separate. We suggest that because of their propensity to burn, many formations termed “dry forest” in Africa and Asia are best considered as savannas. The floristic differentiation of similar vegetation formations from differentcontinents suggests that cross-continental generalisations of the ecology, biology and conservation of savannas and seasonally dry tropicalforests may be difficult.
Phylogenetic conservatism in the relationship between functional and demographic characteristics in Amazon tree taxa
(Wiley, 2024) Pablo Sanchez‐Martinez; Kyle G. Dexter; Frederick C. Draper; Christopher Baraloto; Iêda Leão do Amaral; Luiz de Souza Coêlho; Francisca Dionízia de Almeida Matos; Diógenes de Andrade Lima Filho; Rafael P. Salomão; Florian Wittmann
Abstract Leaf and wood functional traits of trees are related to growth, reproduction, and survival, but the degree of phylogenetic conservatism in these relationships is largely unknown. In this study, we describe the variability of strategies involving leaf, wood and demographic characteristics for tree genera distributed across the Amazon Region, and quantify phylogenetic signal for the characteristics and their relationships. Leaf and wood traits are aligned with demographic variables along two main axes of variation. The first axis represents the coordination of leaf traits describing resource uptake and use, wood density, seed mass, and survival. The second axis represents the coordination between size and growth. Both axes show strong phylogenetic signal, suggesting a constrained evolution influenced by ancestral values, yet the second axis also has an additional, substantial portion of its variation that is driven by functional correlations unrelated to phylogeny, suggesting simultaneously higher evolutionary lability and coordination. Synthesis . Our results suggest that life history strategies of tropical trees are generally phylogenetically conserved, but that tree lineages may have some capability of responding to environmental changes by modulating their growth and size. Overall, we provide the largest‐scale synopsis of functional characteristics of Amazonian trees, showing substantial nuance in the evolutionary patterns of individual characteristics and their relationships. Read the free Plain Language Summary for this article on the Journal blog.
Phylogenetic diversity of Amazonian tree communities
(Wiley, 2015) Eurídice N. Honorio Coronado; Kyle G. Dexter; R. Toby Pennington; Jérôme Chave; Simon L. Lewis; Miguel N. Alexiades; Esteban Álvarez‐Dávila; Atila Alves de Oliveira; Iêda Leão do Amaral; Alejandro Araujo‐Murakami
Abstract Aim To examine variation in the phylogenetic diversity ( PD ) of tree communities across geographical and environmental gradients in Amazonia. Location Two hundred and eighty‐three c . 1 ha forest inventory plots from across Amazonia. Methods We evaluated PD as the total phylogenetic branch length across species in each plot ( PD ss), the mean pairwise phylogenetic distance between species ( MPD ), the mean nearest taxon distance ( MNTD ) and their equivalents standardized for species richness (ses. PD ss, ses. MPD , ses. MNTD ). We compared PD of tree communities growing (1) on substrates of varying geological age; and (2) in environments with varying ecophysiological barriers to growth and survival. Results PD ss is strongly positively correlated with species richness ( SR ), whereas MNTD has a negative correlation. Communities on geologically young‐ and intermediate‐aged substrates (western and central Amazonia respectively) have the highest SR , and therefore the highest PD ss and the lowest MNTD . We find that the youngest and oldest substrates (the latter on the Brazilian and Guiana Shields) have the highest ses. PD ss and ses. MNTD . MPD and ses. MPD are strongly correlated with how evenly taxa are distributed among the three principal angiosperm clades and are both highest in western Amazonia. Meanwhile, seasonally dry tropical forest (SDTF) and forests on white sands have low PD , as evaluated by any metric. Main conclusions High ses. PD ss and ses. MNTD reflect greater lineage diversity in communities. We suggest that high ses. PD ss and ses. MNTD in western Amazonia results from its favourable, easy‐to‐colonize environment, whereas high values in the Brazilian and Guianan Shields may be due to accumulation of lineages over a longer period of time. White‐sand forests and SDTF are dominated by close relatives from fewer lineages, perhaps reflecting ecophysiological barriers that are difficult to surmount evolutionarily. Because MPD and ses. MPD do not reflect lineage diversity per se , we suggest that PD ss, ses. PD ss and ses. MNTD may be the most useful diversity metrics for setting large‐scale conservation priorities.
Phylogeny of Weinmannia (Cunoniaceae) reveals the contribution of the southern extratropics to tropical Andean biodiversity
(Elsevier BV, 2025) Ricardo A. Segovia; Eduardo Aguirre-Mazzi; Christine E. Edwards; Alexander G. Linan; A C.; Andrea Chaspuengal; Kyle G. Dexter; Francisco Fajardo‐Gutiérrez; William Farfán-Ríos; Nora H. Oleas
Seasonal drought limits tree species across the Neotropics
(Wiley, 2016) Adriane Esquivel‐Muelbert; Timothy R. Baker; Kyle G. Dexter; Simon L. Lewis; Hans ter Steege; Gabriela López‐González; Abel Monteagudo Mendoza; Roel Brienen; Ted R. Feldpausch; Nigel C. A. Pitman
Within the tropics, the species richness of tree communities is strongly and positively associated with precipitation. Previous research has suggested that this macroecological pattern is driven by the negative effect of water‐stress on the physiological processes of most tree species. This implies that the range limits of taxa are defined by their ability to occur under dry conditions, and thus in terms of species distributions predicts a nested pattern of taxa distribution from wet to dry areas. However, this ‘dry‐tolerance’ hypothesis has yet to be adequately tested at large spatial and taxonomic scales. Here, using a dataset of 531 inventory plots of closed canopy forest distributed across the western Neotropics we investigated how precipitation, evaluated both as mean annual precipitation and as the maximum climatological water deficit, influences the distribution of tropical tree species, genera and families. We find that the distributions of tree taxa are indeed nested along precipitation gradients in the western Neotropics. Taxa tolerant to seasonal drought are disproportionally widespread across the precipitation gradient, with most reaching even the wettest climates sampled; however, most taxa analysed are restricted to wet areas. Our results suggest that the ‘dry tolerance' hypothesis has broad applicability in the world's most species‐rich forests. In addition, the large number of species restricted to wetter conditions strongly indicates that an increased frequency of drought could severely threaten biodiversity in this region. Overall, this study establishes a baseline for exploring how tropical forest tree composition may change in response to current and future environmental changes in this region.
The biogeography of the Amazonian tree flora
(Nature Portfolio, 2024) Bruno Garcia Luize; Hanna Tuomisto; Robin Ekelschot; Kyle G. Dexter; Iêda Leão do Amaral; Luiz de Souza Coêlho; Francisca Dionízia de Almeida Matos; Diógenes de Andrade Lima Filho; Rafael P. Salomão; Florian Wittmann