Recent work has shown testudines can escape actuarial senescence for extended periods. However, understanding how the interplay between somatic aging and reproductive investment in highly fecund, long-lived ectotherms align with broader phylogenetic patterns remains a critical knowledge gap. Here, we present a comprehensive demographic analysis of age-specific changes in reproduction and mortality using a unique dataset on captive, known-aged green sea turtles Chelonia mydas. Despite substantial intraspecific variation, cumulative egg production showed no decline, increasing linearly for over two decades. However, mortality patterns followed the Gompertz Law, increasing exponentially with age. These results demonstrate a significant decoupling between sustained reproductive performance and age-specific mortality, building on a body of work that challenges the notion of uniformly arrested senescence. Nevertheless, life history strategies across testudines, including sea turtles, produce similar aging rates and remain low relative to endothermic tetrapods, reflecting conserved life-history patterns.

Understanding the energetic demands of reproduction on female sea turtles is crucial for devising effective conservation strategies aimed at supporting the reproductive health and resilience of populations at nesting habitats. We studied the ovaries of 69 green turtles (Chelonia mydas) preyed upon by jaguars (Panthera onca) during three nesting seasons at Tortuguero, Costa Rica, the main green turtle Atlantic nesting beach. Our findings revealed a bimodal distribution of vitellogenic follicles, with 'dominant' follicles destined for ovulation and 'non-dominant' follicles to be resorbed. Female green turtles lay, on average, six clutches with ~110 eggs each per nesting season, and a size hierarchy was also found within dominant follicles. During the nesting season, the diameter of small dominant follicles increased by 66% prior to ovulation. Analysis of yolk composition showed that small dominant follicles had higher percent water content than large dominant follicles, which indicates dry matter deposition rather than hydration is responsible for the pre-ovulatory increase in diameter of green turtle dominant follicles during the nesting season. Furthermore, percentages of lipid, nitrogen (N) and phosphorus (P) in the yolk dry matter were constant across green turtle vitellogenic follicles, which underscores that the increase in follicle size results from provisioning with yolk containing similar proportions of these nutrients. Atretic follicles had higher water and lower P percentages than dominant follicles, indicating an accelerated resorption of phosphorus over lipids and N, which could be due to the importance of this nutrient for eggshell production. Finally, >49% of the energy required for egg production was still to be invested during the nesting season, and yolk from non-dominant follicles would not have provided sufficient energy for most females to complete yolk deposition. These insights into follicular dynamics and nutrient provisioning clarify the ongoing reproductive investments made by female green turtles at Tortuguero.

Assessing conservation status and pursuing applicable management priorities for marine megafauna across multiple scales pose significant challenges. Because marine turtles exemplify these challenges, the IUCN Marine Turtle Specialist Group (MTSG) developed the 'conservation priorities portfolio' (CPP) framework in 2011 to evaluate population risk and threats for regional management units (RMUs). Here, the MTSG has updated the 2011 CPP framework through an inclusive assessment process. Expert elicitation results involving 145 individuals from 50 countries suggests that marine turtle conservation status appears to be improving, but significant challenges remain. Since the previous assessment, long-term abundance trends increased on average, and threat impact scores improved for nearly twice as many RMUs (53%) as worsened (28%) (>= 10% threshold for changes in numeric scores). While expert-assessed threat impacts have generally decreased, fisheries bycatch remains the highest scored threat across regions and species. Risk-threat staus improved for most (54%) RMUs. Over 40% of RMUs were scored as low risk-low threats, of which 8 were green turtles Chelonia mydas RMUs. Less than 20% of RMUs were scored as high risk-high threats, of which 4 were leatherback turtles Dermochelys coriacea. Most high risk-high threats RMUs were in the Pacific Ocean, while most low risk-low threats RMUs were in the Atlantic Ocean. Eleven RMUs were evaluated as having critical data needs. Our results-also provided through an interactive data dashboard-underscore the importance of context-specific planning to effectively target limited conservation resources. Future assessments should further prioritize inclusion of under-represented topics, researchers, and regions to better address multi-faceted conservation challenges.

[This corrects the article DOI: 10.1371/journal.pone.0292727.].

Concerns over the sustainability of green turtle grazing have become a central topic in discussions of seagrass protection. Understanding grazing plot dynamics and aging is critical to evaluating the sustainability of grazing and understanding the role green turtles play in structuring seagrass foraging habitats. We investigated grazing plot dynamics and aging at 2 naturally grazed seagrass meadows in the Caribbean: one experiencing increasing grazing and one experiencing decreasing grazing. By integrating in-water characterization of grazing plots with aerial imagery of naturally grazed meadows, we show that green turtle grazing plots are dynamic, with establishment of new plots, expansion and merging of existing plots, and abandonment and regrowth of plots occurring within 3 and 13 mo periods. We also document that green turtles contribute to a component of habitat complexity by increasing edge habitat in seagrass meadows, and that they can maintain grazing plots for more than 9 yr. By July 2019, green turtles had been maintaining grazing plots for at least 6.65 yr where grazed area was decreasing and for at least 9.22 yr where grazed area was increasing. We offer new insight into the life cycle of grazing plots and show that green turtle grazing plot use is sustainable over longer periods than previously documented. Future studies investigating grazing plot dynamics and evaluating the sustainability of green turtle grazing over longer periods, across seasons, and in different regions, as well as evaluating cumulative effects of anthropogenic stressors, will be key to effective co-management of green turtles and globally declining seagrasses.

As climate-related impacts threaten marine biodiversity globally, it is important to adjust conservation efforts to mitigate the effects of climate change. Translating scientific knowledge into practical management, however, is often complicated due to resource, economic and policy constraints, generating a knowledge-action gap. To develop potential solutions for marine turtle conservation, we explored the perceptions of key actors across 18 countries in the Mediterranean. These actors evaluated their perceived relative importance of 19 adaptation and mitigation measures that could safeguard marine turtles from climate change. Of importance, despite differences in expertise, experience and focal country, the perceptions of researchers and management practitioners largely converged with respect to prioritizing adaptation and mitigation measures. Climate change was considered to have the greatest impacts on offspring sex ratios and suitable nesting sites. The most viable adaptation/mitigation measures were considered to be reducing other pressures that act in parallel to climate change. Ecological effectiveness represented a key determinant for implementing proposed measures, followed by practical applicability, financial cost, and societal cost. This convergence in opinions across actors likely reflects long-standing initiatives in the Mediterranean region towards supporting knowledge exchange in marine turtle conservation. Our results provide important guidance on how to prioritize measures that incorporate climate change in decision-making processes related to the current and future management and protection of marine turtles at the ocean-basin scale, and could be used to guide decisions in other regions globally. Importantly, this study demonstrates a successful example of how interactive processes can be used to fill the knowledge-action gap between research and management.

Drifting aggregations of Sargassum algae provide critical habitat for endemic, endangered, and commercially important species. They may also provide favorable microclimates for associated fauna. To quantify thermal characteristics of holopelagic Sargassum aggregations, we evaluated thermal profiles of 50 aggregations in situ in the Sargasso Sea. Sea surface temperature (SST) in the center of aggregations was significantly higher than in nearby open water, and SST differential was independent of aggregation volume, area, and thickness. SST differential between aggregation edge and open water was smaller than those between aggregation center and aggregation edge and between aggregation center and open water. Water temperature was significantly higher inside and below aggregations compared to open water but did not vary inside aggregations with depth. Holopelagic Sargassum aggregations provide warmer microhabitats for associated fauna, which may benefit marine ectotherms, though temperature differentials were narrow (up to 0.7 °C) over the range of aggregation sizes we encountered (area 0.01–15 m 2 ). We propose a hypothetical curve describing variation in SST differential with Sargassum aggregation size as a prediction for future studies to evaluate across temporal and geographic ranges. Our study provides a foundation for investigating the importance of thermal microhabitats in holopelagic Sargassum ecosystems.

The multispecific and highly dynamic nature of pelagic longline fisheries demands a holistic view that will likely benefit the development of effective management strategies. This study aims to provide an integrated perspective of the Portuguese longline fishery targeting swordfish Xiphias gladius and blue shark Prionace glauca in the Northeast Atlantic, regarding fishing dynamics, target species catches and associated bycatch. Data from 896 observed fishing sets (887,641 hooks) collected between 2015 and 2020 were used in a cluster analysis to group sets according to the target species. These sets were investigated for spatio-temporal patterns, and the relationship between target species catches and environmental and operational characteristics were examined using generalized additive mixed models (GAMM). A total of 46,306 individuals from 54 species (30 fish, 11 sharks, 2 manta rays, 6 cetaceans, 2 sea turtles and 2 seabirds) were recorded. Swordfish and blue shark comprised over 88.3% of the total catch in numbers (33.6% and 54.7%, respectively). Overall, most of the fishing effort occurred west off mainland Portugal, congregated during autumn when vessels targeted mostly swordfish, and dispersed over the region during spring and summer, when vessels targeted mostly blue shark. The bycatch of sea turtles and a relatively higher diversity of bony fish species, yet low catch in terms of abundance, appeared more associated with sets identified as targeting swordfish. Recorded catch of tunas Thunnus spp. and pelagic sharks, such as the shortfin mako Isurus oxyrinchus and the porbeagle Lamna nasus, were more associated with blue shark sets. Bigeye thresher Alopias superciliosus, thresher Alopias vulpinus, pelagic stingray Pteroplatytrygon violacea and lancetfish Alepisauros ferox were found equally associated with both targeted species. Management strategies for the region are discussed in light of these new findings.

Populations of the green turtle (Chelonia mydas), a megaherbivore that maintains distinct areas of seagrass via cultivation grazing, are recovering worldwide. Evaluating seagrass regrowth dynamics in grazed areas following prolonged, known-durations of herbivory is challenging in situ, but is critical to understand ecosystem function as meadows return to a natural grazed state. Based on a 27-month study in a subtropical Caribbean seagrass meadow (The Bahamas; 23.46° N, 76.06° W), we evaluate Thalassia testudinum regrowth dynamics over 11 months following two durations of simulated green turtle grazing (11 and 16 months; 11clip and 16clip, respectively). By the end of the clipping treatments, simulated grazing had induced significant changes in most T. testudinum leaf morphology and nutrient variables in clipped plots compared to reference plots, while belowground biomass and nutrient content were unaffected. However, most leaf variables in clipped plots returned to levels comparable to reference plots by 6.5 months after the cessation of clipping, with the exception of leaf area index (LAI) and leaf width. The effects of grazing duration on regrowth in clipped treatments were evident in 11clip and 16clip plots. In 11clip plots, LAI increased to reference plot levels within 6.5 months after cessation of clipping, while leaves did not rewiden until 11 months post-clipping. However, LAI in 16clip plots did not reach reference plot levels until 11 months post-clipping, and leaves remained significantly narrow throughout the experiment. These regrowth patterns indicate the capacity of T. testudinum to rebound following prolonged, repetitive cropping of leaf biomass by green turtles, and that decreased leaf width and LAI after cessation of grazing may be a lingering effect of shifts in plant growth allocation in grazed systems. This study provides a valuable contribution to understand the effects of cultivation grazing and grazing duration on T. testudinum regrowth dynamics and tolerance to herbivory.

Understanding the spatial scale of population processes is critical for contextualizing monitoring and prioritizing conservation actions. Green turtle ( Chelonia mydas ) abundance in the Greater Caribbean (GC) region is rebounding from centuries of overexploitation, but recovery trajectories vary among nesting populations. Maternally inherited mitochondrial DNA control region (CR) markers can link juveniles to their source populations, providing spatial ecology context for interpreting differential population trends. However, CR haplotype CM-A3 is shared across all western GC sites, limiting resolution. In this study, 387 females from Tortuguero, Costa Rica, the largest nesting population in the western Atlantic, were reanalyzed through sequencing of an expanded (817-base pair) CR fragment and the mitochondrial short tandem repeat (mtSTR) array. Variation in mtSTR sequences yielded 12 Tortuguero CM-A3 haplotypes. No structure was detected in mtSTR haplotype frequencies spatially or temporally within the Tortuguero rookery. In GC regional comparisons, Tortuguero CM-A3 mtSTR haplotype frequencies were significantly different from those of published Cayman Islands and major Florida nesting populations. This improved resolution of genetic structure reinforces the inference of demographic discreteness of these nesting populations with respect to female natal homing. Furthermore, these refinements provide critical baseline data to reduce uncertainty in future mixed stock analyses. The mtSTR may prove useful in resolving stock structure and migratory connectivity in green turtles in other regions where common CR haplotypes are broadly distributed.

The threat of population declines caused by pelagic longline fisheries in the Atlantic has increased the concern to find strategies that minimize the bycatch and mortality of non-target marine animals. Gear modification, such as the use of circle hooks instead of conventional J-hooks, has been identified as an effective bycatch reduction strategy in different pelagic longline fisheries around the world. This study aimed to verify the effectiveness of the use of circle hooks by quantifying catch rates, relative size selectivity, and anatomical hooking position for the most common target species (swordfish, Xiphias gladius, and blue shark, Prionace glauca), and some bycatch species (loggerhead sea turtles, Caretta caretta, and shortfin mako, Isurus oxyrinchus) caught by the Azorean longline fishing fleet. The trial was conducted for five consecutive years (2000-2004) using eight different types of hooks. In general, the blue shark catches using circle hooks were significantly higher compared to J (Mustad 9/0). The circle hooks also showed high probabilities of catching juvenile blue sharks. Conversely, the circle hooks were efficient in reducing the loggerhead sea turtle bycatch and were related to fewer catches of small sea turtle individuals. The use of circle hooks was also associated with reduced swordfish catches compared to J (Mustad 9/0), and the effect of hook types on length at capture was only significant for Circle (L. & P. 18/0-CLP18) and Ringed Tuna (RT). No significant differences were observed comparing hook type to either catch rates or size selectivity for shortfin mako. Additionally, circle hooks were more likely to lodge in the mouth than in deeper anatomical positions, when compared to J (Mustad 9/0), for the four species analysed. The present study demonstrated that the use of circle hooks could mitigate the impact of the pelagic longline fisheries in the Azores by decreasing the bycatch of sea turtles and reducing animal injuries caused by deep hooking.

Incidental catch or bycatch of sea turtles by pelagic longline fisheries is a major concern worldwide. The Northeast Atlantic hosts key foraging and developmental areas for oceanic juvenile loggerhead sea turtles (Caretta caretta) originating mainly from the Southeastern USA and Cape Verde. This region may be one of the most heavily fished areas by pelagic longline for which no recent assessments of fisheries interactions exist. We analysed fishery observer data collected between 2015 and 2020 to assess sea turtle bycatch by Portuguese commercial longliners targeting swordfish (Xiphias gladius) and blue shark (Prionace glauca) in the Northeast Atlantic. A total of 177 sea turtles interacted with the gear during the 896 fishing sets (887,641 hooks) moni-tored. Loggerheads (n = 139) ranging between 32 and 78 cm curved carapace length (CCL) were caught at a rate of 0.152 turtles per 1000 hooks, and leatherbacks (Dermochelys coriacea; n = 38) between 100 and 210 cm estimated length at a rate of 0.043 turtles per 1000 hooks. Loggerhead and leatherback bycatch shows a clear seasonal pattern in the region. At haul-back mortality rates of oceanic-stage juvenile loggerheads was estimated at 26% whereas no at haul-back mortality was registered for leatherback turtles. Model estimates, based on AIS derived fishing effort from Global Fishing Watch, indicate a total of 1439 interactions (552-3069 BCI) for log-gerhead, and 604 interactions (262-1129 BCI) for leatherback turtles between 2016 and 2020. Information from this study is essential to support effective management strategies for sea turtle conservation in the Northeast Atlantic.

In this study, we investigated the effects of food restriction and subsequent realimentation and compensatory growth on bone structure in juvenile green turtles (Chelonia mydas). Turtles were fed ad libitum food for 12 weeks (AL), restricted food for 12 weeks (R), or restricted food for 5 weeks followed by ad libitum food for 7 weeks (R-AL). After the 12th week, gross morphology (GM), microarchitecture, and mineralization of the right humerus of each turtle were analyzed. This FigShare entry includes the raw data analyzed for this project.

Dermatemys mawii is a critically endangered freshwater turtle endemic to Central America. In the wild, these turtles are thought to be wholly herbivorous as adults and feed on a variety of vegetation; however, no studies have quantitatively assessed potential dietary differences based on biotic and abiotic factors. The purpose of our study was to describe and quantify the wild diet of D. mawii and assess differences based on habitat, maturity, and sex. We evaluated the stomach contents of 66 turtles legally harvested by local hunters for personal consumption throughout the country of Belize. Percent volume (by displacement) and percent frequency of each stomach item were used to calculate an index of relative importance (IRI). One algal and 6 plant families contributed to an overall diet composition consisting of leaves, flowers, stems, seedpods, seeds, and fruit. Rocks and invertebrates were also consumed, although we believe these to be incidental consumption. The leaves of the riparian tree Inga edulis were present in 73.1% of turtle stomachs and accounted for almost half of the total volume of all stomach contents combined. We used Spearman rank correlation coefficients to test the null hypothesis that there was no correlation in the rankings of stomach items (i.e., there were differences) when comparing turtles by habitat, age, and sex. There were significant differences in the ranking of food items between river and lagoon habitats, with lagoon turtles relying heavily on the algae Nadia sp.; however, the stomach contents from both habitats were equally diverse (H-rivers = 1.68, H-lagoons = 1.64). There were no differences in IRIs between adults and juveniles or between males and females. Our results emphasize the importance of habitat in D. mawii diet selection and the importance of leaves from riparian plants species that are shed into their aquatic habitats.

Trindade Island, Brazil, is a small, remote volcanic island located 1140 km off the coast of southeastern Brazil. The green turtle (Chelonia mydas) nesting aggregation on Trindade is genetically distinct, the largest in the southwest Atlantic, and represents the southern limit of green turtle nesting in the Atlantic. Projeto TAMAR (a Brazilian conservation program) has monitored the nesting aggregation discontinuously since 1982. In 2009, a standardized protocol was established for the two beaches (Andradas and Tartarugas) with the highest nest abundance. Data from December 2009 through April 2017 (except 2013) were used in this study. Annual numbers of tracks left by females that emerged onto the beach vary between 558 and 3317 tracks for Andradas and between 760 and 3559 tracks for Tartarugas. Mean nesting probabilities (probability that an emerging female deposits eggs) for all years were 0.22 (95% HDI (highest posterior density interval) = 0.14–0.30) for Andradas and 0.45 (95% HDI = 0.37–0.53) for Tartarugas. Nesting probabilities varied among and within years and had a negative relationship with daily track counts. During our study, annual estimates of nests were stable on both Andradas (range 38–2001) and Tartarugas (range 248–2769). Nest abundance estimates between 1991 and 2008 from an earlier study indicated a stable population, extending the duration of apparent stability to 26 years with the caveat that the studies used different estimation methods. This stability is in contrast with the increasing trends for most green turtle nesting aggregations in the Atlantic.

Survivorship of early life stages is key for the well-being of sea turtle populations, yet studies on animals that distribute around oceanic areas are very challenging. So far, the information on green turtles (Chelonia mydas) that use the open NE Atlantic as feeding grounds is scarce. Strandings occurring in oceanic archipelagos can provide relevant information about the biology, ecology and current anthropogenic pressures for megafauna inhabiting the open ocean. In this study, we analysed stranding events of green turtles found in the Azores archipelago to investigate interactions with marine litter. In addition, we quantified and characterized litter items stranded on beaches to provide a direct comparison between the ingested items with the debris found in the environment. A total of 21 juvenile green turtles were found stranded in the region between 2000 and 2020 (size range: 12-49 cm, CCL). Overall, 14% of the animals were entangled in marine litter and 86% of the turtles necropsied had ingested plastic. The mean abundance of items ingested was 27.86 ± 23.40 and 98% were white/transparent. Hard plastic fragments between 1 and 25 mm were the most common shape recovered in the turtles, similarly to what was found on the coastline. All of the litter items analysed with pyrolysis GC-MS revealed to be polyethylene (PE). This study provides the first baseline assessment of interactions of plastic litter with juvenile green turtles found at the east edge of the North Atlantic Subtropical Gyre. The combination of these results supports the hypothesis that migratory megafauna that use remote oceanic islands as a feeding ground are exposed to anthropogenic litter contamination dominated by plastics, even when these regions are located far away from big industrial centers or populated cities.

Abstract Populations of green turtles (Chelonia mydas), a megaherbivore that consumes seagrasses via cultivation grazing, are recovering worldwide. Information on plant‐mediated effects on herbivore foraging behavior is critical to understanding plant–herbivore interactions and sustainability of grazing as ecosystems continue to change. In a Caribbean seagrass ecosystem, we use stationary cameras and benthic surveys to evaluate the effects of seagrass morphology and leaf nitrogen content on green turtle grazing behavior. Thalassia testudinum leaf morphology has significant effects on forage intake (in milligrams of dry mass [DM] per minute) for green turtles, whereas leaf nitrogen content has no effect. Intake increases in grazed areas with shorter leaves and higher leaf biomass concentration (in milligrams of DM per cubic centimeter), indicating more efficient foraging under these conditions. Bite rate (in bites per minute) increases in grazed areas with short leaves, a result of reduced search time. Bite size (in milligrams of DM per bite) increases in grazed areas with short but dense canopies, because a turtle crops more shoots with each bite. Increased foraging efficiency and reduced search time in grazed areas with high biomass concentrations collectively maximize intake. Ingested leaves are shorter than the mean height of all available leaves in grazed areas, indicating herbivore selection for shorter leaves. Our estimate for daily intake is 86.1 g DM day−1 33‐kg turtle−1. Our study provides a novel contribution on the effects of plant‐level cues on the grazing behavior of a marine megaherbivore, and how cultivation grazing behavior optimizes the green turtle foraging strategy by maximizing foraging efficiency and intake.

Seagrasses form productive marine ecosystems that serve as important foraging grounds for grazers. Meadow productivity is vulnerable to environmental change, however, because environmental factors often strongly regulate seagrass growth. Understanding effects of grazing and environmental driver interactions on growth dynamics is therefore needed to ensure the long-term sustainability of seagrass meadow foraging habitats. We simulated natural green turtle (Chelonia mydas) grazing by experimentally clipping seagrass for 16 months in a Thalassia testudinum meadow and measured how responses in linear growth, production, the production-to-biomass ratio (P : B; compensatory growth), and leaf area index differed between clipped and unclipped seagrass in response to in situ changes in temperature and salinity. While increasing temperature and salinity had positive and negative effects, respectively, on growth rates, clipping did not alter the relationship between these abiotic drivers and seagrass growth. Simulated grazing did, however, alter effects of temperature on seagrass P : B ratio and leaf area index dynamics. Each increased significantly with temperature; however, P : B ratios only increased in experimentally clipped seagrass, whereas leaf area index only increased in unclipped seagrass. These results suggest that, given temperature-stimulated growth, grazed seagrass prioritizes increasing biomass production, whereas ungrazed seagrass prioritizes increasing photosynthetic surface area. In addition, our results demonstrate that the strength of the compensatory growth response to grazing in T. testudinum is seasonally dependent, highlighting the importance of biotic-abiotic interactions in driving growth dynamics. In a future with increasing grazer abundance and climate-driven stressors, understanding these types of interactions will be critical for long-term sustainability of seagrass ecosystems.

Recovery of green turtles ( Chelonia mydas ), mega‐herbivores that consume seagrasses, is resulting in dramatic ecosystem‐wide changes as meadows are returned to a natural grazed state. The green turtle grazing strategy, with long‐term cultivation of meadows and high foraging site fidelity, is distinct from other terrestrial and aquatic mega‐herbivores and may affect seagrass compensatory growth responses. Identifying the mechanisms of compensatory growth responses to grazing is essential to understand the functioning of plant systems under natural grazing regimes. In a naturally grazed Caribbean seagrass ecosystem, we identify a mechanism for compensatory growth responses to grazing by evaluating relationships between Thalassia testudinum morphology and growth, grazing intensity, and canopy light dynamics in grazed and ungrazed areas. The morphological characteristics that explain variability in T . testudinum growth differed between grazed and ungrazed areas. In grazed areas, T. testudinum leaf linear growth, leaf area growth, and productivity:biomass (P:B) significantly increased as above‐ground biomass decreased; P:B also increased with shoot density. Mass growth in grazed areas exhibited an increasing trend with shoot density and was maintained above a threshold of 2.5 g dry mass m −2 above‐ground biomass. In ungrazed areas, trends for mass growth and P:B with above‐ground biomass and shoot density were opposite to those in grazed areas. In grazed areas, shoot density significantly increased with grazing intensity while above‐ground biomass decreased and leaf area index (LAI) was not affected. Light availability at canopy height was greater in grazed areas than in ungrazed areas, and canopy light attenuation increased with shoot density in grazed areas. Synthesis . Grazing removes above‐ground biomass, which increases light availability and stimulates leaf growth and turnover (i.e. compensatory growth). Shoot density increases with grazing intensity, maintaining LAI and canopy light harvesting potential. This maximizes the potential for leaf photosynthetic activity and provides the plant with the capacity to sustain mass growth and support a compensatory growth response to grazing. This study presents novel insight for assessing the underlying mechanisms of plant compensatory growth responses to cultivation grazing and proposes potential thresholds that may be used to evaluate the sustainability of in situ grazing pressure by a recovering mega‐herbivore.

Reconstructing past events of hybridization and population size changes are required to understand speciation mechanisms and current patterns of genetic diversity, and ultimately contribute to species' conservation. Sea turtles are ancient species currently facing anthropogenic threats including climate change, fisheries, and illegal hunting. Five of the seven extant sea turtle species are known to currently hybridize, especially along the Brazilian coast where some populations can have ~32%–42% of hybrids. Although frequently observed today, it is not clear what role hybridization plays in the evolutionary diversification of this group of reptiles. In this study, we generated whole genome resequencing data of the five globally distributed sea turtle species to estimate a calibrated phylogeny and the population size dynamics, and to understand the role of hybridization in shaping the genomes of these ancient species. Our results reveal discordant species divergence dates between mitochondrial and nuclear genomes, with a high frequency of conflicting trees throughout the nuclear genome suggesting that some sea turtle species frequently hybridized in the past. The reconstruction of the species' demography showed a general decline in effective population sizes with no signs of recovery, except for the leatherback sea turtle. Furthermore, we discuss the influence of reference bias in our estimates. We show long‐lasting ancestral gene flow events within Chelonioidea that continued for millions of years after initial divergence. Speciation with gene flow is a common pattern in marine species, and it raises questions whether current hybridization events should be considered as a part of these species' evolutionary history or a conservation issue.