Science Rendue Possible

Reichgelt, T., A. Baumgartner, R. Feng, and D. A. Willard. 2023. Poleward amplification, seasonal rainfall and forest heterogeneity in the Miocene of the eastern USA. Global and Planetary Change 222: 104073.

Paleoclimate reconstructions can provide a window into the environmental conditions in Earth history when atmospheric carbon dioxide concentrations were higher than today. In the eastern USA, paleoclimate reconstructions are sparse, because terrestrial sedimentary deposits are rare. Despite this, the eastern USA has the largest population and population density in North America, and understanding the effects of current and future climate change is of vital importance. Here, we provide terrestrial paleoclimate reconstructions of the eastern USA from Miocene fossil floras. Additionally, we compare proxy paleoclimate reconstructions from the warmest period in the Miocene, the Miocene Climatic Optimum (MCO), to those of an MCO Earth System Model. Reconstructed Miocene temperatures and precipitation north of 35°N are higher than modern. In contrast, south of 35°N, temperatures and precipitation are similar to today, suggesting a poleward amplification effect in eastern North America. Reconstructed Miocene rainfall seasonality was predominantly higher than modern, regardless of latitude, indicating greater variability in intra-annual moisture transport. Reconstructed climates are almost uniformly in the temperate seasonal forest biome, but heterogeneity of specific forest types is evident. Reconstructed Miocene terrestrial temperatures from the eastern USA are lower than modeled temperatures and coeval Atlantic sea surface temperatures. However, reconstructed rainfall is consistent with modeled rainfall. Our results show that during the Miocene, climate was most different from modern in the northeastern states, and may suggest a drastic reduction in the meridional temperature gradient along the North American east coast compared to today.

Coca‐de‐la‐Iglesia, M., N. G. Medina, J. Wen, and V. Valcárcel. 2022. Evaluation of the tropical‐temperate transitions: An example of climatic characterization in the Asian Palmate group of Araliaceae. American Journal of Botany.

(no abstract available)

Sánchez-González, L. A., H. Cayetano, D. A. Prieto-Torres, O. R. Rojas-Soto, and A. G. Navarro-Sigüenza. 2022. The role of ecological and geographical drivers of lineage diversification in the Squirrel cuckoo Piaya cayana in Mexico: a mitochondrial DNA perspective. Journal of Ornithology.

The Squirrel Cuckoo ( Piaya cayana ) is a widely distributed neotropical species with 14 recognized subspecies. Two parapatric subspecies are distributed in Mexico. P. c. mexicana is endemic to the seasonally dry tropical forests of western Mexico, and P. c. thermophila is found in humid forests from eastern Mexico to western Colombia. The 2 taxa have a small area of overlap on the Isthmus of Tehuantepec, but there is pronounced phenotypic differentiation, and very few reported intermediate individuals between these forms, leading to debate about the taxonomic status of the Mesoamerican taxa. Based on two mitochondrial genes, we used phylogenetic, phylogeographic, morphological, and ecological modelling analyses to describe the evolutionary relationships and paleo-distributional patterns of P. cayana in Mexico. Divergence time estimates suggest that the split between P. c. mexicana and P. c. thermophila occurred during the Pleistocene, about 1.24 Mya. Morphometrics of Mexican subspecies indicate that tail length and the white tail tips are significantly longer in P. c. mexicana , while P. c. thermophila has a longer and wider bill. Ecological niche analyses indicated that niche similarity between both lineages was lower than expected by chance, while low values on cross-prediction tests suggested that the two lineages have inhabited different environmental spaces since at least the Late Pleistocene. The ecological niche difference may also be associated with a steep humidity gradient, suggesting a significant contemporary environmental barrier. Overall, our results indicate that P. c. mexicana and P. c. thermophila have divergent evolutionary histories; therefore, the current taxonomic status of the Piaya populations in Mexico reflects neither their evolutionary relationships nor their apparent divergence. Our results suggest a major split in the polytypic P. cayana coinciding with the Andes, suggesting that the western endemic P. c. mexicana and P. c. thermophila are best treated as separate species-level taxa . Die Rolle ökologischer und geografischer Faktoren bei der Abstammung und Diversifikation des Eichhornkuckucks Piaya cayana in Mexiko: von der mitochondrialen DNA her betrachtet Der Eichhornkuckuck ( Piaya cayana ) ist eine weit verbreitete neotropische Art mit 14 anerkannten Unterarten. In Mexiko gibt es zwei parapatrische Unterarten. P. c. mexicana ist in den je nach Jahreszeit trockenen tropischen Wäldern Westmexikos beheimatet, während P. c. thermophila in den feuchten Wäldern von Ostmexiko bis Westkolumbien vorkommt. Die beiden Taxa überschneiden sich in einem kleinen Gebiet an der Landenge von Tehuantepec, aber es gibt einen ausgeprägten phänotypischen Unterschied und nur sehr wenige bekannte Mischtypen zwischen den beiden und damit Anlass zu Diskussionen über den taxonomischen Status dieser mittelamerikanischen Taxa. Auf der Grundlage zweier mitochondrialer Gene haben wir phylogenetische, phylogeografische, morphologische und ökologische Modell-Analysen durchgeführt, um die abstammungsbiologischen Verbindungen und Verbreitungsmuster von P. cayana im Paläozän in Mexiko zu bestimmen. Schätzungen der Entstehungszeit der Unterschiede deuten darauf hin, dass die Trennung zwischen P. c. mexicana und P. c. thermophila während des Pleistozäns stattfand, vor etwa 1,24 Millionen Jahren. Die morphometrischen Daten der mexikanischen Unterarten zeigen, dass die Schwanzlänge und die weißen Schwanzspitzen bei P. c. mexicana deutlich länger sind, während P. c. thermophila einen längeren und breiteren Schnabel hat. Analysen der ökologischen Nischen zeigten, dass die Übereinstimmungen zwischen den beiden Linien geringer waren als durch Zufall zu erwarten wäre, während niedrige Werte bei Kreuz-Vorhersagetests darauf hindeuteten, dass die beiden Linien mindestens seit dem späten Pleistozän in unterschiedlichen Lebensräumen gelebt haben müssen. Der ökologische Nischenunterschied kann auch mit dem starken Feuchtigkeitsgradienten zusammenhängen, was auf eine bedeutende gegenwärtige Umweltbarriere hinweist. Insgesamt deuten unsere Ergebnisse darauf hin, dass P. c. mexicana und P. c. thermophila eine unterschiedliche Entwicklungsgeschichte haben; daher gibt der derzeitige taxonomische Status der Piaya-Populationen in Mexiko weder ihre evolutionäre Verwandtschaft, noch ihre offensichtlichen Unterschiede wieder. Unsere Ergebnisse deuten darauf hin, dass sich der polytypische P. cayana in den Anden aufgespalten hat, was bedeuten könnte, dass die im Westen endemischen P. c. mexicana und P. c. thermophila am besten als separate Taxa auf Artniveau behandelt werden sollten.

Gori, B., T. Ulian, H. Y. Bernal, and M. Diazgranados. 2022. Understanding the diversity and biogeography of Colombian edible plants. Scientific Reports 12.

Despite being the second most biodiverse country in the world, hosting more than 7000 useful species, Colombia is characterized by widespread poverty and food insecurity. Following the growing attention in Neglected and Underutilized Species, the present study will combine spatial and taxonomic analysis to unveil their diversity and distribution, as well as to advocate their potential as key resources for tackling food security in the country. The cataloguing of Colombian edible plants resulted in 3805 species. Among these, the most species-rich genera included Inga, Passiflora, Miconia, Solanum, Pouteria , Protium , Annona and Bactris . Biogeographic analysis revealed major diversity hotspots in the Andean humid forests by number of records, species, families, and genera. The departments of Antioquia, Boyacá, Meta, and Cundinamarca ranked first both in terms of number of unique georeferenced records and species of edible plants. Significant information gaps about species distribution were detected in the departments of Cesar, Sucre, Atlántico, Vichada, and Guainía, corresponding to the Caribe and Llanos bioregions, indicating the urgent need for focusing investigation in these areas. Furthermore, a significant level of geographic specificity was found in edible plant species’ distributions between 13 different bioregions and 33 departments, hinting the adoption of tailorized prioritisation protocols for the conservation and revitalization of such resources at the local level.

Cano, Á., F. W. Stauffer, T. Andermann, I. M. Liberal, A. Zizka, C. D. Bacon, H. Lorenzi, et al. 2022. Recent and local diversification of Central American understorey palms. Global Ecology and Biogeography 31: 1513–1525.

Aim Central America is largely covered by hyperdiverse, yet poorly understood, rain forests. Understorey palms are diverse components of these forests, but little is known about their historical assembly. It is not clear when palms in Central America reached present diversity levels and whether most species arrived from neighbouring regions or evolved locally. We addressed these questions using the most species-rich American palm clades indicative of rain forests. We reconstructed and compared their phylogenomic and biogeographical history with the diversification of 54 other plant lineages, to gain a better understanding of the processes that shaped the assembly of Central American rain forests. Location Central America. Time period Cretaceous to present. Major taxa studied Arecaceae: Arecoideae: Bactridinae, Chamaedoreeae, Geonomateae. Methods We sampled 218 species through fieldwork and living collections. We sequenced their genomic DNA using target sequence-capture procedures. Using 12 calibration points, we reconstructed dated phylogenies under three approaches (multispecies coalescent, maximum likelihood and Bayesian inference), conducted biogeographical analyses (dispersal–extinction–cladogenesis) and estimated phylogenetic diversity metrics. Results Dated phylogenies revealed intense diversification in Central America from 12 Ma. Local diversification events were four times more frequent than dispersal events, and we found strong phylogenetic clustering in relationship to Central America. Main conclusions Our results suggest that most understorey palm species that characterize the Central American rain forests today evolved locally after repeated dispersal events, mostly from South America. Understorey palms in Central American rain forests diversified primarily after closure of the Central American Seaway at c. 13 Ma, suggesting that the Great American Biotic Interchange was a major trigger for plant diversification in Central American rain forests. This recent diversification contrasts with the much earlier existence of rain forest palms in neighbouring South America since c. 58 Ma. We found similar timings of diversification in 54 other seed plant lineages, suggesting an unexpectedly recent assembly of the hyperdiverse Central American flora.

Williams, C. J. R., D. J. Lunt, U. Salzmann, T. Reichgelt, G. N. Inglis, D. R. Greenwood, W. Chan, et al. 2022. African Hydroclimate During the Early Eocene From the DeepMIP Simulations. Paleoceanography and Paleoclimatology 37.

The early Eocene (∼56‐48 million years ago) is characterised by high CO2 estimates (1200‐2500 ppmv) and elevated global temperatures (∼10 to 16°C higher than modern). However, the response of the hydrological cycle during the early Eocene is poorly constrained, especially in regions with sparse data coverage (e.g. Africa). Here we present a study of African hydroclimate during the early Eocene, as simulated by an ensemble of state‐of‐the‐art climate models in the Deep‐time Model Intercomparison Project (DeepMIP). A comparison between the DeepMIP pre‐industrial simulations and modern observations suggests that model biases are model‐ and geographically dependent, however these biases are reduced in the model ensemble mean. A comparison between the Eocene simulations and the pre‐industrial suggests that there is no obvious wetting or drying trend as the CO2 increases. The results suggest that changes to the land sea mask (relative to modern) in the models may be responsible for the simulated increases in precipitation to the north of Eocene Africa. There is an increase in precipitation over equatorial and West Africa and associated drying over northern Africa as CO2 rises. There are also important dynamical changes, with evidence that anticyclonic low‐level circulation is replaced by increased south‐westerly flow at high CO2 levels. Lastly, a model‐data comparison using newly‐compiled quantitative climate estimates from palaeobotanical proxy data suggests a marginally better fit with the reconstructions at lower levels of CO2.

Reichgelt, T., D. R. Greenwood, S. Steinig, J. G. Conran, D. K. Hutchinson, D. J. Lunt, L. J. Scriven, and J. Zhu. 2022. Plant Proxy Evidence for High Rainfall and Productivity in the Eocene of Australia. Paleoceanography and Paleoclimatology 37.

During the early to middle Eocene, a mid‐to‐high latitudinal position and enhanced hydrological cycle in Australia would have contributed to a wetter and “greener” Australian continent where today arid to semi‐arid climates dominate. Here, we revisit 12 southern Australian plant megafossil sites from the early to middle Eocene to generate temperature, precipitation and seasonality paleoclimate estimates, net primary productivity (NPP) and vegetation type, based on paleobotanical proxies and compare to early Eocene global climate models. Temperature reconstructions are uniformly subtropical (mean annual, summer, and winter mean temperatures 19–21 °C, 25–27 °C and 14–16 °C, respectively), indicating that southern Australia was ∼5 °C warmer than today, despite a >20° poleward shift from its modern geographic location. Precipitation was less homogeneous than temperature, with mean annual precipitation of ∼60 cm over inland sites and >100 cm over coastal sites. Precipitation may have been seasonal with the driest month receiving 2–7× less than mean monthly precipitation. Proxy‐model comparison is favorable with an 1680 ppm CO2 concentration. However, individual proxy reconstructions can disagree with models as well as with each other. In particular, seasonality reconstructions have systemic offsets. NPP estimates were higher than modern, implying a more homogenously “green” southern Australia in the early to middle Eocene, when this part of Australia was at 48–64 °S, and larger carbon fluxes to and from the Australian biosphere. The most similar modern vegetation type is modern‐day eastern Australian subtropical forest, although distance from coast and latitude may have led to vegetation heterogeneity.

Lima‐Rezende, C. A., G. S. Cabanne, A. V. Rocha, M. Carboni, R. M. Zink, and R. Caparroz. 2022. A comparative phylogenomic analysis of birds reveals heterogeneous differentiation processes among Neotropical savannas. Molecular Ecology 31: 3451–3467.

The main objective of this study is to evaluate biogeographic hypotheses of diversification and connection between isolated savannas north (Amazonian savannas) and south (Cerrado core) of the Amazon River. To achieve our goal, we employed genomic markers (genotyping‐by‐sequencing) to evaluate the genetic structure, population phylogenetic relationships, and historical range shifts of four Neotropical passerines with peri‐Atlantic distributions: the Narrow‐billed Woodcreeper (Lepidocolaptes angustirostris), the Plain‐crested Elaenia (Elaenia cristata), the Grassland Sparrow (Ammodramus humeralis), and the White‐banded Tanager (Neothraupis fasciata). The population genetic analyses indicated that landscape (e.g., geographic distance, landscape resistance, and percentage of tree cover) and climate metrics explained divergence among populations in most species, but without indicating a differential role between current and historical factors. Our results did not fully support the hypothesis that isolated populations at Amazonian savannas have been recently derived from the Cerrado core domain. Intraspecific phylogenies and gene flow analyses supported multiple routes of connection between the Cerrado and Amazonian savannas, rejecting the hypothesis that the Atlantic corridor explains the peri‐Atlantic distribution. Our results reveal that the biogeographic history of the region is complex and cannot be explained by simple vicariant models.

Chevalier, M. 2022. <i>crestr</i>: an R package to perform probabilistic climate reconstructions from palaeoecological datasets. Climate of the Past 18: 821–844.

Abstract. Statistical climate reconstruction techniques are fundamental tools to study past climate variability from fossil proxy data. In particular, the methods based on probability density functions (or PDFs) can be used in various environments and with different climate proxies because they rely on elementary calibration data (i.e. modern geolocalised presence data). However, the difficulty of accessing and curating these calibration data and the complexity of interpreting probabilistic results have often limited their use in palaeoclimatological studies. Here, I introduce a new R package (crestr) to apply the PDF-based method CREST (Climate REconstruction SofTware) on diverse palaeoecological datasets and address these problems. crestr includes a globally curated calibration dataset for six common climate proxies (i.e. plants, beetles, chironomids, rodents, foraminifera, and dinoflagellate cysts) associated with an extensive range of climate variables (20 terrestrial and 19 marine variables) that enables its use in most terrestrial and marine environments. Private data collections can also be used instead of, or in combination with, the provided calibration dataset. The package includes a suite of graphical diagnostic tools to represent the data at each step of the reconstruction process and provide insights into the effect of the different modelling assumptions and external factors that underlie a reconstruction. With this R package, the CREST method can now be used in a scriptable environment and thus be more easily integrated with existing workflows. It is hoped that crestr will be used to produce the much-needed quantified climate reconstructions from the many regions where they are currently lacking, despite the availability of suitable fossil records. To support this development, the use of the package is illustrated with a step-by-step replication of a 790 000-year-long mean annual temperature reconstruction based on a pollen record from southeastern Africa.

Sluiter, I. R. K., G. R. Holdgate, T. Reichgelt, D. R. Greenwood, A. P. Kershaw, and N. L. Schultz. 2022. A new perspective on Late Eocene and Oligocene vegetation and paleoclimates of South-eastern Australia. Palaeogeography, Palaeoclimatology, Palaeoecology 596: 110985.

We present a composite terrestrial pollen record of latest Eocene through Oligocene (35.5–23 Ma) vegetation and climate change from the Gippsland Basin of south-eastern Australia. Climates were overwhelmingly mesothermic through this time period, with mean annual temperature (MAT) varying between 13 and 18 °C, with an average of 16 °C. We provide evidence to support a cooling trend through the Eocene–Oligocene Transition (EOT), but also identify three subsequent warming cycles through the Oligocene, leading to more seasonal climates at the termination of the Epoch. One of the warming episodes in the Early Oligocene appears to have also occurred at two other southern hemisphere sites at the Drake Passage as well as off eastern Tasmania, based on recent research. Similarities with sea surface temperature records from modern high southern latitudes which also record similar cycles of warming and cooling, are presented and discussed. Annual precipitation varied between 1200 and 1700 mm/yr, with an average of 1470 mm/yr through the sequence. Notwithstanding the extinction of Nothofagus sg. Brassospora from Australia and some now microthermic humid restricted Podocarpaceae conifer taxa, the rainforest vegetation of lowland south-eastern Australia is reconstructed to have been similar to present day Australian Evergreen Notophyll Vine Forests existing under the sub-tropical Köppen-Geiger climate class Cfa (humid subtropical) for most of the sequence. Short periods of cooler climates, such as occurred through the EOT when MAT was ~ 13 °C, may have supported vegetation similar to modern day Evergreen Microphyll Fern Forest. Of potentially greater significance, however, was a warm period in the Early to early Late Oligocene (32–26 Ma) when MAT was 17–18 °C, accompanied by small but important increases in Araucariaceae pollen. At this time, Araucarian Notophyll/Microphyll Vine Forest likely occurred regionally.