Hydrological Effects on the Reproduction of the Giant South American River Turtle Podocnemis expansa (Testudines: Podocnemididae)

Simoncini, Melina Soledad; Sousa, Heitor Campos de; Portelinha, Thiago Costa Gonçalves; Falcon, Guth Berger; Collicchio, Erich; Balestra, Rafael Antônio Machado; Luz, Vera Lúcia Ferreira; Colli, Guarino R.; Malvásio, Adriana

doi:10.1643/h2020152

Cited by 4 publications

(4 citation statements)

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“…Changes in climate patterns can potentially harm turtle populations. For instance, excessive moisture in nesting areas may lead to the death of embryos, while inadequate moisture can negatively affect their development (Simoncini et al., 2022). Furthermore, changes in climate have the potential to influence physiological processes and interactions between species, thereby contributing to variations in the structure and composition of genetic groups (Hughes, 2000).…”

Section: Discussionmentioning

confidence: 99%

“…While it is more common to observe nests on beaches characterized by low vegetation productivity, P. unifilis is known to nest in diverse environments, including areas with undergrowth, close to forests in overgrown regions, ravines, and floodplains. Furthermore, the species utilizes various substrates such as sand, clay, mud, and soil(Andrade, 2015;Andrade et al, 2022;Ferrara et al, 2017;Simoncini et al, 2022;…”

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confidence: 99%

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Riverscape features determining the genetic structure of the Yellow‐Spotted Amazon River Turtle (Podocnemis unifilis) in Brazilian Amazonia

Agostini,

Machado,

Ritter

et al. 2024

Biotropica

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Landscape characteristics can influence gene flow depending on the species ability to disperse. This imposes different levels of resistance to movement, determining the genetic structure and diversity of populations. Waterfalls and rapids in the Amazon basin have been suggested as contributing factors to the diversification and genetic structure of freshwater species, including turtles. Thus, along some main rivers of the Brazilian Amazon: Juruá, Madeira, Amazonas, Trombetas, Tapajós, Xingu, Tocantins, and Araguaia, we evaluated the spatial distribution of genetic diversity and characterized the population structure of Podocnemis unifilis, a widely distributed and endangered Amazonian turtle, using the mitochondrial DNA control region. We tested for isolation by geographic distance and by resistance models through an integrative approach using genetic, geographic, and ecological data, comparing these matrices with genetic distance. We found heterogeneous levels of genetic diversity and no spatial patterns. Results supported the isolation by resistance hypothesis, where the movement of individuals was influenced by freshwater, vegetational, climatological, and geomorphological variables, explaining the genetic distance of P. unifilis. Rapids and waterfalls impose greater resistance although they are barriers with different levels of permeability to the P. unifilis gene flow. Thus, the idiosyncrasies of each sub‐basin must be considered in the interpretation of the patterns found in assessing phylogeographic history.Abstract in Portuguese is available with online material.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Riverscape features determining the genetic structure of the Yellow‐Spotted Amazon River Turtle (Podocnemis unifilis) in Brazilian Amazonia

Agostini,

Machado,

Ritter

et al. 2024

Biotropica

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“…The increase in the area of sand bars can affect the connectivity of river systems and the ecogeomorphological dynamics of species adapted to hydroclimatic and hydrogemorphological regimes (LENHART; NABER; NIEBER, 2013). When bars increase in size, they can obstruct water flow, reduce the depth of the channel, and hinder the circulation of fish and other aquatic organisms (FERREIRA JÚNIOR; CASTRO, 2003;SIMONCINI et al, 2022). In addition, the increase in bars indicates greater erosion upstream, changes in the dynamics of floods and droughts and impacts on water quality, damaging the health of aquatic ecosystems and the conservation of biodiversity (RESTREPO; KETTNER; SYVITSKI, 2015).…”

Section: Influences On River Connectivity and Ecogeomorphological Dyn...mentioning

confidence: 99%

Temporal trends in sand bars and water bodies on the right side of the world's largest fluvial island - Javaés River

Santos,

Cremon,

Cherem

2024

RBGeomorfologia

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Bananal Island is the largest river island in the world, located in the Araguaia River basin in central-western Brazil. Studies on the Araguaia River have shown that changes in the main channel are linked to the increase in sediment input due to agricultural expansion in the Cerrado. However, very little is known about the Javaés River, on the opposite margin of Bananal Island. This study analyzed the temporal trends of sand bars and water masses in the Javaés River from 1985 to 2021. Annual mosaics of Landsat images were generated to identify the classes of water masses and sand bars. The Mann Kendall and Sen's Slope tests were used to identify trends and statistical significance of changes over time. The results indicated an increase of 57% (6.5 km²) in the areas of sand bars and a reduction of 39% (15.2 km²) in water bodies. The tests revealed significant trends with an increase in bars and a decrease in water bodies. It was observed that changes in the distribution and rates of regional precipitation, along with the expansion of anthropogenic occupation, are contributing to an increase in sediment input, in a cascade effect, affecting the balance between erosion and deposition in the Javaés River.

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“…Considering that the variables that best explained the geographical distribution of P. uni lis were the mean annual precipitation and the duration of the water ow, the in uence of landscape resistance on the movement of individuals may be related to reproductive adaptation, or at least in uence the onset of the nesting period (which depends on the decrease in water level and varies according to the regional hydrological cycle), and even on reproductive success (Ferrara et al 2017;Simoncini et al 2022). Hydrological variables can also signi cantly affect the reproductive parameters of P. expansa, and precipitation and the river level are considered the most relevant factors that regulate populations in a locality of the Araguaia River (Simoncini et al 2022). The authors found positive relationships between clutch size, hatching success and egg breakage with rising of local river and headwaters levels, but pointed out that changes in weather patterns can put populations at risk, since excessive moisture can cause embryonic death and lack of humidity can affect embryonic development.…”

Section: Isolation By Distance and By Resistancementioning

confidence: 99%

Landscape configurations determining the genetic structure of the Yellow-Spotted Amazon River Turtle (Podocnemis unifilis) in Brazilian Amazonia

Agostini

Machado

Ritter

et al. 2023

Preprint

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Landscape features can influence gene flow detected in genetic structure and diversity. The effect will depend on the ability to disperse and may vary between species. Waterfalls and rapids in the Amazon basin have been suggested as causing the diversification and genetic structure of freshwater species, including turtles. Thus, we evaluated the spatial distribution of genetic diversity of Podocnemis unifilis, a widely distributed and endangered turtle, along the main rivers of the Brazilian Amazon. We used the mitochondrial DNA control region to characterize the population structure and test hypotheses of isolation by distance (IBD) or resistance (IBR) through an integrative approach using genetic, geographic, and ecological data. We compared matrices of geographic (linear and in-water distance) and resistance distances (niche modeling and/or waterfalls and rapids) in genetic distance. We found heterogeneous levels of genetic diversity (no spatial patterns) and a geographically complex pattern of population genetic structure. In some localities, gene flow follows watersheds, connecting watercourses, but it also has some genetic structure withing rivers, where waterfalls and rapids act as barriers to dispersal. The IBR better explains the genetic distance, the movement of individuals is influenced by aquatic, vegetational, biological, and geomorphological variables. Efforts for the conservation of the species need to be applied in all its distribution considering landscape genetics. Thus, projects that impact aquatic organisms such as dams and others need to rely on regional or even local migration of Amazonian turtle populations in rivers, verifying the connectivity within each watercourse, improving the knowledge of negative impacts.

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Hydrological Effects on the Reproduction of the Giant South American River Turtle Podocnemis expansa (Testudines: Podocnemididae)

Cited by 4 publications

References 74 publications

Riverscape features determining the genetic structure of the Yellow‐Spotted Amazon River Turtle (Podocnemis unifilis) in Brazilian Amazonia

Riverscape features determining the genetic structure of the Yellow‐Spotted Amazon River Turtle (Podocnemis unifilis) in Brazilian Amazonia

Temporal trends in sand bars and water bodies on the right side of the world's largest fluvial island - Javaés River

Landscape configurations determining the genetic structure of the Yellow-Spotted Amazon River Turtle (Podocnemis unifilis) in Brazilian Amazonia

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