Long‐Term Landscape Development Processes in Amazonia

Irion, Georg; Kalliola, Risto

doi:10.1002/9781444306408.ch11

Cited by 14 publications

(19 citation statements)

References 44 publications

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“…These periods actually correspond to two different developmental phases of the main drainage. In the Plio–Pleistocene, the Amazon river (and its tributaries) would have been more entrenched and likely with vast fluctuations in discharge controlled by Quaternary climate fluctuations (see Irion & Kalliola, ). Such debate poses specific challenges to biological interpretations regarding the RBH based on estimates of divergence times.…”

Section: Introductionmentioning

confidence: 99%

Testing main Amazonian rivers as barriers across time and space within widespread taxa

Pirani

Werneck

Thomaz

et al. 2019

Journal of Biogeography

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Aim Present Amazonian diversity patterns can result from many different mechanisms and, consequently, the factors contributing to divergence across regions and/or taxa may differ. Nevertheless, the river‐barrier hypothesis is still widely invoked as a causal process in divergence of Amazonian species. Here we use model‐based phylogeographic analyses to test the extent to which major Amazonian rivers act similarly as barriers across time and space in two broadly distributed Amazonian taxa. Local Amazon rain forest. Taxon The lizard Gonatodes humeralis (Sphaerodactylidae) and the tree frog Dendropsophus leucophyllatus (Hylidae). Methods We obtained RADseq data for samples distributed across main river barriers, representing main Areas of Endemism previously proposed for the region. We conduct model‐based phylogeographic and genetic differentiation analyses across each population pair. Results Measures of genetic differentiation (based on FST calculated from genomic data) show that all rivers are associated with significant genetic differentiation. Parameters estimated under investigated divergence models showed that divergence times for populations separated by each of the 11 bordering rivers were all fairly recent. The degree of differentiation consistently varied between taxa and among rivers, which is not an artifact of any corresponding difference in the genetic diversities of the respective taxa, or to amounts of migration based on analyses of the site‐frequency spectrum. Main conclusions Taken together, our results support a dispersal (rather than vicariance) history, without strong evidence of congruence between these species and rivers. However, once a species crossed a river, populations separated by each and every river have remained isolated—in this sense, rivers act similarly as barriers to any further gene flow. This result suggests differing degrees of persistence and gives rise to the seeming contradiction that the divergence process indeed varies across time, space and species, even though major Amazonian rivers have acted as secondary barriers to gene flow in the focal taxa.

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Section: Introductionmentioning

confidence: 99%

Testing main Amazonian rivers as barriers across time and space within widespread taxa

Pirani

Werneck

Thomaz

et al. 2019

Journal of Biogeography

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“…Based on the evolutionary history of the Madeira River paleolandforms analyzed here, these features did not originate according to the hypothesis of ria formation due to erosion during the Last Glacial Maximum low sea level followed by sediment aggradation during the Holocene transgression (i.e. Irion, ; Irion and Kalliola, ). Due to the sandy nature, the active channel deposits were not used for radiocarbon dating.…”

Section: Discussionmentioning

confidence: 73%

“…Previous publications have related the genesis of Amazonian fluvial rias to sediment aggradation at the mouth of tributary channels (Sioli, ; Tricart, ). This process would have occurred as a result of fluvial erosion in the Last Glaciation Maximum low sea level, followed by sediment aggradation during the Holocene transgression (see a review in Irion and Kalliola, ). On the other hand, a few authors have also suggested a neotectonic origin for the Amazonian fluvial rias (Sternberg, , ; Mauro et al ., ; Dumont, ; Dumont and Fournier, ; Bezerra, ).…”

Section: Introductionmentioning

confidence: 99%

Understanding Amazonian fluvial rias based on a Late Pleistocene–Holocene analog

Bertani

Rossetti

Hayakawa

et al. 2014

Earth Surf Processes Landf

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Fluvial rias are elongated lakes at tributary mouths that can reach dozens of kilometers in length, constituting one of the most remarkable features in the Amazonian landscape. Thus far, definitive data which documents the genesis of fluvial rias have not been published. The main goal of this work was to integrate morphological, sedimentological and chronological information in order to characterize fluvial paleorias in the interfluve of the Purus and Madeira Rivers and discuss the most likely hypothesis for their genesis. These paleorias were first observed through remote sensing imagery as several elongated and interconnecting belts of open vegetation that are in sharp contact with the surrounding dense forest. The belts are branched and form a dendritic pattern similar to many modern drainage networks. The sedimentary record of these belts revealed the prevalence of sharp‐based sandstones and mudstones arranged into fining‐upward successions, which are compatible with deposition within channels. Active channel and abandoned channel deposits were recognized. These are topped by continuous mudstones related to rapid channel abandonment and formation of a low energy basin or ria environment. Radiocarbon dating of these deposits recorded only Late Pleistocene and Holocene ages ranging from 21 547–22 285 cal yr bp to 5928–6124 cal yr bp. This chronology for sediment deposition is not compatible with the hypothesis of Amazonian rias being formed by fluvial erosion during the Last Glaciation Maximum low sea level, with sediment accumulation during the subsequent Holocene transgression. Instead, the studied paleorias record previous tributaries of the Madeira River that became abandoned as the position of this river shifted southeastward and its interfluve tilted northward, inverting the drainage systems. Therefore, a neotectonic origin of some Amazonian paleorias seems most likely. This hypothesis should be considered in further investigations aiming at understanding the origin of numerous modern fluvial rias that typify the Amazonian landscape. Copyright © 2014 John Wiley & Sons, Ltd.

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“…Over the last 30 million years (Ma), Amazon biodiversity evolved amidst extraordinary geomorphological dynamics. While the western sedimentary portion suffered several changes (Hoorn, Guerrero, Sarmiento, & Lorente, ;Hoorn et al, ;Rossetti, Toledo, & Góes, ;Vonhof, Wesselingh, & Ganssen, ), the eastern granitic shields experienced relative stability (Aleixo & Rossetti, ;Irion & Kalliola, ). How the evolution of the Amazonian biota reflects these environmental changes is still not fully understood (Leite & Rogers, ;Ribas, Aleixo, Nogueira, Miyaki, & Cracraft, ).…”

Section: Introductionmentioning

confidence: 99%

Hidden in the DNA: How multiple historical processes and natural history traits shaped patterns of cryptic diversity in an Amazon leaf‐litter lizardLoxopholis osvaldoi(Squamata: Gymnophthalmidae)

Marques‐Souza

Pellegrino

Brunes

et al. 2019

Journal of Biogeography

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Aim To investigate the cryptic diversity and diversification timing in the putatively low‐dispersal Amazonian leaf‐litter lizard Loxopholis osvaldoi, and to ask how geography (rivers, isolation by distance, IBD), ecological drivers (isolation by environment, IBE) and historical factors (climatic refugia) explain intraspecific genetic variation. Location Central Amazonia, Brazil. Taxon Squamata; Gymnophthalmidae; Loxopholis osvaldoi. Methods We sequenced two mitochondrial and two nuclear markers in 157 individuals. Phylogeographic structure and the occurrence of independent evolving lineages where explored through phylogenetic and coalescent analyses. A species tree and divergence dates of lineages were inferred with *BEAST, employing multiple DNA substitution rates. The potential genetic impacts of geographical distance among localities, the environment and the position of localities in relation to main rivers were tested by redundancy analysis (RDA). Results We detected 11 independently evolving and largely divergent intraspecific lineages. Lineage distribution patterns are complex and do not match any conspicuous barrier to gene flow, except for the Amazon River. Most lineages appear to have originated in the lower Miocene and Pliocene, in disagreement with the Pleistocene refuge hypothesis. IBD, IBE and rivers appear to have acted in concert establishing and maintaining genetic structure. However, when controlling for other explanatory variables, IBD explains significantly more variation than rivers, IBE or historical factors. Main Conclusions Our results strongly suggest that L. osvaldoi is a species complex. Future taxonomic work should use an integrative approach to explore whether morphological variation is present and congruent with the genetic data. While the use of a sensitive dating analysis allowed us to better describe the diversification history of L. osvaldoi, the lack of a spatial model of Neogene river dynamics prevents the test of specific, more informative river barrier hypotheses. The data suggest that nonlinear correlation analyses (e.g. RDA) should be preferred to detect factors that affect phylogeographic patterns in the Amazon, instead of linear multiple regressions (e.g. Mantel tests). Given the high level of cryptic diversity detected within this and other Amazonian species, we caution against hypothesis tests based solely on the distribution of nominal taxa, which can provide a rather incomplete view of the processes behind Amazonian diversity.

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Long‐Term Landscape Development Processes in Amazonia

Cited by 14 publications

References 44 publications

Testing main Amazonian rivers as barriers across time and space within widespread taxa

Testing main Amazonian rivers as barriers across time and space within widespread taxa

Understanding Amazonian fluvial rias based on a Late Pleistocene–Holocene analog

Hidden in the DNA: How multiple historical processes and natural history traits shaped patterns of cryptic diversity in an Amazon leaf‐litter lizardLoxopholis osvaldoi(Squamata: Gymnophthalmidae)

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