The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Andrés Giménez - One of the best experts on this subject based on the ideXlab platform.
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Sperm storage reduces the strength of the mate-finding Allee effect.
Ecology and evolution, 2020Co-Authors: María V. Jiménez-franco, José D. Anadón, Andrés Giménez, Roberto C. Rodríguez-caro, Francisco Botella, Ana Sanz-aguilar, Thorsten Wiegand, Eva GraciáAbstract:Mate searching is a key component of sexual reproduction that can have important implications for population viability, especially for the mate-finding Allee effect. Interannual sperm storage by females may be an adaptation that potentially attenuates mate limitation, but the demographic consequences of this functional trait have not been studied. Our goal is to assess the effect of female sperm storage durability on the strength of the mate-finding Allee effect and the viability of populations subject to low population density and habitat alteration. We used an individual-based simulation model that incorporates realistic representations of the demographic and spatial processes of our model species, the Spur-Thighed Tortoise (Testudo graeca). This allowed for a detailed assessment of reproductive rates, population growth rates, and extinction probabilities. We also studied the relationship between the number of reproductive males and the reproductive rates for scenarios combining different levels of sperm storage durability, initial population density, and landscape alteration. Our results showed that simulated populations parameterized with the field-observed demographic rates collapsed for short sperm storage durability, but were viable for a durability of one year or longer. In contrast, the simulated populations with a low initial density were only viable in human-altered landscapes for sperm storage durability of 4 years. We find that sperm storage is an effective mechanism that can reduce the strength of the mate-finding Allee effect and contribute to the persistence of low-density populations. Our study highlights the key role of sperm storage in the dynamics of species with limited movement ability to facilitate reproduction in patchy landscapes or during population expansion. This study represents the first quantification of the effect of sperm storage durability on population dynamics in different landscapes and population scenarios.
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Assessment of the key evolutionary traits that prevent extinctions in human-altered habitats using a spatially explicit individual-based model
Ecological Modelling, 2020Co-Authors: Eva Graciá, José D. Anadón, Roberto C. Rodríguez-caro, Francisco Botella, Ana Sanz-aguilar, Angel Luis García-garcía, Thorsten Wiegand, Andrés GiménezAbstract:Abstract Identifying key evolutionary strategies that support population persistence remains a challenging task for biodiversity conservation. Here we assess if animal adaptations to cope with low densities (i.e. that facilitate mate-findings or promote spatial aggregation of individuals) can allow species to persist in human-altered habitats. A spatially explicit and individual-based model was developed to assess if, and under what circumstances, such adaptations maintain population viability. The model was parameterised with data from the movement and demography of the Spur-Thighed Tortoise (Testudo graeca) and simulated scenarios with differences in adult survivorships, initial population sizes and habitat alterations. Habitat alterations reduced population viability, and extinction rates were dependent on population characteristics and mate-finding distance. In contrast, philopatry around the birthplace did not prevent extinctions. Our results highlight the importance of considering specific spatial traits of species when assessing their vulnerability to human habitat alterations.
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Impact of habitat loss on the diversity and structure of ecological networks between oxyurid nematodes and Spur-Thighed Tortoises (Testudo graeca L.).
PeerJ, 2019Co-Authors: Julieta Benítez-malvido, Andrés Giménez, Roberto C. Rodríguez-caro, Eva Graciá, Rocío Ruiz De Ybáñez, Héctor Hugo Siliceo-cantero, Anna TravesetAbstract:Habitat loss and fragmentation are recognized as affecting the nature of biotic interactions, although we still know little about such changes for reptilian herbivores and their hindgut nematodes, in which endosymbiont interactions could range from mutualistic to commensal and parasitic. We investigated the potential cost and benefit of endosymbiont interactions between the Spur-Thighed Tortoise (Testudo graeca L.) and adult oxyurid nematodes (Pharyngodonidae order Oxyurida) in scrublands of southern Spain. For this, we assessed the association between richness and abundance of oxyurid species with Tortoises' growth rates and body traits (weight and carapace length) across levels of habitat loss (low, intermediate and high). Furthermore, by using an intrapopulation ecological network approach, we evaluated the structure and diversity of Tortoise-oxyurid interactions by focusing on oxyurid species infesting individual Tortoises with different body traits and growth rates across habitats. Overall, Tortoise body traits were not related to oxyurid infestation across habitats. Oxyurid richness and abundance however, showed contrasting relationships with growth rates across levels of habitat loss. At low habitat loss, oxyurid infestation was positively associated with growth rates (suggesting a mutualistic oxyurid-Tortoise relationship), but the association became negative at high habitat loss (suggesting a parasitic relationship). Furthermore, no relationship was observed when habitat loss was intermediate (suggesting a commensal relationship). The network analysis showed that the oxyurid community was not randomly assembled but significantly nested, revealing a structured pattern for all levels of habitat loss. The diversity of interactions was lowest at low habitat loss. The intermediate level, however, showed the greatest specialization, which indicates that individuals were infested by fewer oxyurids in this landscape, whereas at high habitat loss individuals were the most generalized hosts. Related to the latter, connectance was greatest at high habitat loss, reflecting a more uniform spread of interactions among oxyurid species. At an individual level, heavier and larger Tortoises tended to show a greater number of oxyurid species interactions. We conclude that there is an association between habitat loss and the Tortoise-oxyurid interaction. Although we cannot infer causality in their association, we hypothesize that such oxyurids could have negative, neutral and positive consequences for Tortoise growth rates. Ecological network analysis can help in the understanding of the nature of such changes in Tortoise-oxyurid interactions by showing how generalized or specialized such interactions are under different environmental conditions and how vulnerable endosymbiont interactions might be to further habitat loss.
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Human-mediated secondary contact of two Tortoise lineages results in sex-biased introgression
Scientific Reports, 2017Co-Authors: Eva Graciá, Andrés Giménez, Roberto C. Rodríguez-caro, Ana C. Andreu, Uwe Fritz, Francisco BotellaAbstract:Human-mediated secondary contact of recently diverged taxa offers valuable opportunities for studying the evolutionary mechanisms involved in the establishment and maintenance of genetic boundaries between taxa. We used mitochondrial and microsatellite markers to examine a recently introduced population of the Spur-Thighed Tortoise ( Testudo graeca ) of mixed origin in the Doñana National Park (SW Spain). The earliest records of Tortoises in Doñana trace back to the 18th century, but several population reinforcements in the 20th century with animals from Morocco are well-documented. Consequently, different genetic lineages, which represent distinct subspecies, are thought to co-exist there. Our results confirmed the presence of distinct lineages by revealing that Tortoises of the subspecies T. g. marokkensis were introduced into a local allochthonous T. g. graeca population. Unexpectedly, T. g. marokkensis haplotypes exclusively appeared in males, and admixture levels were statistically sex-biased toward males. The sex ratio of the population deviated from parity, with males being 2.36-fold more abundant than females. Our results indicated that population reinforcements had a strong effect on the genetic composition of this population and aggravated its sex ratio deviation. We predict that this sex-biased pattern of introgression is ephemeral and advocated to the near loss of T. g. marokkensis haplotypes.
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Low Tortoise abundances in pine forest plantations in forest-shrubland transition areas.
PloS one, 2017Co-Authors: Roberto C. Rodríguez-caro, José D. Anadón, Eva Graciá, C. S. Oedekoven, Stephen T. Buckland, Miguel Ángel Esteve-selma, Julia Martínez, Andrés GiménezAbstract:In the transition between Mediterranean forest and the arid subtropical shrublands of the southeastern Iberian Peninsula, humans have transformed habitat since ancient times. Understanding the role of the original mosaic landscapes in wildlife species and the effects of the current changes as pine forest plantations, performed even outside the forest ecological boundaries, are important conservation issues. We studied variation in the density of the endangered Spur-Thighed Tortoise (Testudo graeca) in three areas that include the four most common land types within the species' range (pine forests, natural shrubs, dryland crop fields, and abandoned crop fields). Tortoise densities were estimated using a two-stage modeling approach with line transect distance sampling. Densities in dryland crop fields, abandoned crop fields and natural shrubs were higher (>6 individuals/ha) than in pine forests (1.25 individuals/ha). We also found large variation in density in the pine forests. Recent pine plantations showed higher densities than mature pine forests where shrub and herbaceous cover was taller and thicker. We hypothesize that mature pine forest might constrain Tortoise activity by acting as partial barriers to movements. This issue is relevant for management purposes given that large areas in the Tortoise's range have recently been converted to pine plantations.
Eva Graciá - One of the best experts on this subject based on the ideXlab platform.
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Differences in Reproductive Success in Young and Old Females of a Long-Lived Species.
Animals : an open access journal from MDPI, 2021Co-Authors: Amalia Segura, Roberto C. Rodríguez-caro, Eva Graciá, Pelayo AcevedoAbstract:Long-lived species are particularly interesting for investigation of trade-offs that shape reproductive allocation and the effective contribution to the next generations. Life history theory predicts that these species will buffer environmental stochasticity via changes in the reproductive investment, while maintaining high adult survival rates. The Spur-Thighed Tortoise was selected as a case study in order to investigate the relationship between the linked maternal characteristics (size and age) and related traits in their hatchlings. We tracked naturally emerging hatchlings from young and old females under semi-natural conditions to test variations in hatchling numbers, body mass, size and survival over two years. We used linear mixed-effect models to analyze variations in hatchling body mass and size, and a mark–release–recapture framework to model their survival. Our study illustrates that old females of long-lived species have greater offspring numbers, greater survival and smaller size when compared with those of young females. The interannual variability evidenced the reduced offspring number and survival in the lower autumn rainfall and spring mean temperature year. Our results highlight the role of maternal age and climatic conditions in the population dynamics and the need for long-term studies of reproduction traits for designating adequate conservation strategies.
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From troubles to solutions: conservation of Mediterranean Tortoises under global change
Basic and Applied Herpetology, 2020Co-Authors: Eva Graciá, Roberto C. Rodríguez-caro, Marcos Ferrández, Albert Martínez-silvestre, Irene Pérez-ibarra, Rabie Amahjour, Carmen Aranda, Hadj Aissa Benelkadi, Albert Bertolero, Marta BiagginiAbstract:Chelonians are among the animal groups with the poorest conservation status. Since Tortoises are long-lived species that need very long time to reach sexual maturity, they are extremely vulnerable to human pressure. Despite their endangered status, there are no common strategies for the development of conservation actions. At the “Mediterranean workshop to develop Tortoise conservation strategies”, scientists, conservation associations, environmental managers, IUCN advisers and CITES inspectors met in October 2019 in Alicante (Spain). The aims were to update the diagnosis of the conservation status of the Hermann’s Tortoise (Testudo hermanni) and the Spur-Thighed Tortoise (Testudo graeca) and to suggest strategies that guarantee their preservation at the Mediterranean Region. The main conclusions are summarized by: i) Mediterranean Tortoises are wild endangered species that must be protected in, and together with, their natural habitat. Their main threats are habitat loss and fragmentation and pet trade, but we should also pay attention to wildfires, spread of diseases, the introduction of exotic species or lineages and climate change. ii) Long-term efforts and stablished protocols are needed to accurately diagnose and monitor the conservation status of wild populations, as well as flows among captive and wild animals. iii) Tortoise trade should be banned because it threatens the conservation of wild populations of Tortoises. Illegal practices related to Tortoises should be decidedly persecuted. People should consider Tortoises as wild animals that are endangered and deserving of protection. It is possible to enjoy them by responsibly observing them in their habitat. iv) Tortoises may carry pathogens or parasites and their sanitary status cannot be fully assessed. They should always be considered potential vectors of Tortoise diseases and of zoonosis. Hygiene protocols should be implemented when managing them. v) The researchers attending this workshop aimed to develop a scientific network for the long-term monitoring of graeca and T. hermanni populations in the Mediterranean Region. They will need the support from public administrations.
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Sperm storage reduces the strength of the mate-finding Allee effect.
Ecology and evolution, 2020Co-Authors: María V. Jiménez-franco, José D. Anadón, Andrés Giménez, Roberto C. Rodríguez-caro, Francisco Botella, Ana Sanz-aguilar, Thorsten Wiegand, Eva GraciáAbstract:Mate searching is a key component of sexual reproduction that can have important implications for population viability, especially for the mate-finding Allee effect. Interannual sperm storage by females may be an adaptation that potentially attenuates mate limitation, but the demographic consequences of this functional trait have not been studied. Our goal is to assess the effect of female sperm storage durability on the strength of the mate-finding Allee effect and the viability of populations subject to low population density and habitat alteration. We used an individual-based simulation model that incorporates realistic representations of the demographic and spatial processes of our model species, the Spur-Thighed Tortoise (Testudo graeca). This allowed for a detailed assessment of reproductive rates, population growth rates, and extinction probabilities. We also studied the relationship between the number of reproductive males and the reproductive rates for scenarios combining different levels of sperm storage durability, initial population density, and landscape alteration. Our results showed that simulated populations parameterized with the field-observed demographic rates collapsed for short sperm storage durability, but were viable for a durability of one year or longer. In contrast, the simulated populations with a low initial density were only viable in human-altered landscapes for sperm storage durability of 4 years. We find that sperm storage is an effective mechanism that can reduce the strength of the mate-finding Allee effect and contribute to the persistence of low-density populations. Our study highlights the key role of sperm storage in the dynamics of species with limited movement ability to facilitate reproduction in patchy landscapes or during population expansion. This study represents the first quantification of the effect of sperm storage durability on population dynamics in different landscapes and population scenarios.
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Assessment of the key evolutionary traits that prevent extinctions in human-altered habitats using a spatially explicit individual-based model
Ecological Modelling, 2020Co-Authors: Eva Graciá, José D. Anadón, Roberto C. Rodríguez-caro, Francisco Botella, Ana Sanz-aguilar, Angel Luis García-garcía, Thorsten Wiegand, Andrés GiménezAbstract:Abstract Identifying key evolutionary strategies that support population persistence remains a challenging task for biodiversity conservation. Here we assess if animal adaptations to cope with low densities (i.e. that facilitate mate-findings or promote spatial aggregation of individuals) can allow species to persist in human-altered habitats. A spatially explicit and individual-based model was developed to assess if, and under what circumstances, such adaptations maintain population viability. The model was parameterised with data from the movement and demography of the Spur-Thighed Tortoise (Testudo graeca) and simulated scenarios with differences in adult survivorships, initial population sizes and habitat alterations. Habitat alterations reduced population viability, and extinction rates were dependent on population characteristics and mate-finding distance. In contrast, philopatry around the birthplace did not prevent extinctions. Our results highlight the importance of considering specific spatial traits of species when assessing their vulnerability to human habitat alterations.
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Impact of habitat loss on the diversity and structure of ecological networks between oxyurid nematodes and Spur-Thighed Tortoises (Testudo graeca L.).
PeerJ, 2019Co-Authors: Julieta Benítez-malvido, Andrés Giménez, Roberto C. Rodríguez-caro, Eva Graciá, Rocío Ruiz De Ybáñez, Héctor Hugo Siliceo-cantero, Anna TravesetAbstract:Habitat loss and fragmentation are recognized as affecting the nature of biotic interactions, although we still know little about such changes for reptilian herbivores and their hindgut nematodes, in which endosymbiont interactions could range from mutualistic to commensal and parasitic. We investigated the potential cost and benefit of endosymbiont interactions between the Spur-Thighed Tortoise (Testudo graeca L.) and adult oxyurid nematodes (Pharyngodonidae order Oxyurida) in scrublands of southern Spain. For this, we assessed the association between richness and abundance of oxyurid species with Tortoises' growth rates and body traits (weight and carapace length) across levels of habitat loss (low, intermediate and high). Furthermore, by using an intrapopulation ecological network approach, we evaluated the structure and diversity of Tortoise-oxyurid interactions by focusing on oxyurid species infesting individual Tortoises with different body traits and growth rates across habitats. Overall, Tortoise body traits were not related to oxyurid infestation across habitats. Oxyurid richness and abundance however, showed contrasting relationships with growth rates across levels of habitat loss. At low habitat loss, oxyurid infestation was positively associated with growth rates (suggesting a mutualistic oxyurid-Tortoise relationship), but the association became negative at high habitat loss (suggesting a parasitic relationship). Furthermore, no relationship was observed when habitat loss was intermediate (suggesting a commensal relationship). The network analysis showed that the oxyurid community was not randomly assembled but significantly nested, revealing a structured pattern for all levels of habitat loss. The diversity of interactions was lowest at low habitat loss. The intermediate level, however, showed the greatest specialization, which indicates that individuals were infested by fewer oxyurids in this landscape, whereas at high habitat loss individuals were the most generalized hosts. Related to the latter, connectance was greatest at high habitat loss, reflecting a more uniform spread of interactions among oxyurid species. At an individual level, heavier and larger Tortoises tended to show a greater number of oxyurid species interactions. We conclude that there is an association between habitat loss and the Tortoise-oxyurid interaction. Although we cannot infer causality in their association, we hypothesize that such oxyurids could have negative, neutral and positive consequences for Tortoise growth rates. Ecological network analysis can help in the understanding of the nature of such changes in Tortoise-oxyurid interactions by showing how generalized or specialized such interactions are under different environmental conditions and how vulnerable endosymbiont interactions might be to further habitat loss.
Pelayo Acevedo - One of the best experts on this subject based on the ideXlab platform.
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Differences in Reproductive Success in Young and Old Females of a Long-Lived Species.
Animals : an open access journal from MDPI, 2021Co-Authors: Amalia Segura, Roberto C. Rodríguez-caro, Eva Graciá, Pelayo AcevedoAbstract:Long-lived species are particularly interesting for investigation of trade-offs that shape reproductive allocation and the effective contribution to the next generations. Life history theory predicts that these species will buffer environmental stochasticity via changes in the reproductive investment, while maintaining high adult survival rates. The Spur-Thighed Tortoise was selected as a case study in order to investigate the relationship between the linked maternal characteristics (size and age) and related traits in their hatchlings. We tracked naturally emerging hatchlings from young and old females under semi-natural conditions to test variations in hatchling numbers, body mass, size and survival over two years. We used linear mixed-effect models to analyze variations in hatchling body mass and size, and a mark–release–recapture framework to model their survival. Our study illustrates that old females of long-lived species have greater offspring numbers, greater survival and smaller size when compared with those of young females. The interannual variability evidenced the reduced offspring number and survival in the lower autumn rainfall and spring mean temperature year. Our results highlight the role of maternal age and climatic conditions in the population dynamics and the need for long-term studies of reproduction traits for designating adequate conservation strategies.
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Implications for Conservation of Collection of Mediterranean Spur-Thighed Tortoise as Pets in Morocco: Residents' Perceptions, Habits, and Knowledge.
Animals : an open access journal from MDPI, 2020Co-Authors: Amalia Segura, Miguel Delibes-mateos, Pelayo AcevedoAbstract:The trading and collection of wild animals as pets may be cause for concern regarding animal welfare and species conservation. These concerns can be exemplified by Mediterranean Spur-Thighed Tortoise (Testudo graeca), a long-living species whose use as pets is long established. The human dimension plays a major role in the wildlife for the pet collection, and is particularly important in countries like Morocco, where this might pose a threat to the conservation of the species involved. This study, which is based on a questionnaire survey (n = 480 participants), documents the fact that many people in Morocco keep Tortoises as pets: 55% of the participants in the survey and over two Tortoises/person. Importantly, most captive Tortoises, particularly juveniles, had been collected directly from wild populations by their owners (42%, n = 264). In general, the Tortoise owners had limited knowledge of their Tortoises’ habits and requirements, although rural people were more likely to acknowledge that the Tortoise is a wild and threatened species. Our study reveals that non-commercial collection is a common activity in Morocco that may threaten wild Tortoise populations and hence species conservation, and it could have consequences regarding the welfare of the animals. We were also able to identify the profile of people towards whom education campaigns should be directed in order to reduce the number of Tortoises collected from wild populations. Additional field research should also be conducted to quantify the impact of pet collection on wild Tortoise populations.
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Predation of young Tortoises by ravens: the effect of habitat structure on Tortoise detectability and abundance.
Scientific Reports, 2020Co-Authors: Amalia Segura, José Jiménez, Pelayo AcevedoAbstract:The predation of young Tortoise is considered a major cause of mortality for many Tortoise species. The predation by common ravens has been identified as being responsible for significant decreases in Tortoise populations. Mediterranean Spur-Thighed Tortoise hatchlings and juveniles in Maamora forest (Morocco) were studied in order to describe the size/age class predation of common ravens on young Tortoises and infer the drivers of predation risk and population abundance. The results showed a high level of predation on young Tortoises (
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The importance of protected and unprotected areas for the Mediterranean Spur-Thighed Tortoise demography in northwest Morocco
Amphibia-Reptilia, 2019Co-Authors: Amalia Segura, Pelayo AcevedoAbstract:Abstract Collection for the pet trade has been considered one of the major threats to the Mediterranean Spur-Thighed Tortoise Testudo graeca, since it modulates the size and structure of the species’ populations and, therefore, their demography. Maamora forest is one of the most suitable habitats for this species. The proximity of the forest to Rabat indicated the possibility of these Tortoise populations being particularly sensitive to over-collecting. Population demography was studied in four populations, in protected and unprotected areas in Maamora forest. The results showed significant differences as regards population size and structure between protected and unprotected areas. They specifically highlighted: i) higher density (23-17 indiv · ha−1) balanced populations in the protected areas, in which young adults were predominant, ii) a higher body condition in the protected areas, especially the females, and iii) a low density (5.5 ind · ha−1) more unbalance population in the unprotected areas, in which older females and younger males were predominant. In addition, a survey carried out by interviewing local adults () showed that most people owned Tortoises (61%, ), mainly juveniles (65%, ). The respondents stated that their Tortoises had been captured in the forest (68%, ). Maamora forest is home to one of the highest density populations of Mediterranean Spur-Thighed Tortoises documented to date, and its conservation is essential if this species is to be maintained. Our social survey suggested that one of the challenges is to change the social perception of the Mediterranean Spur-Thighed Tortoise as a pet and highlight its intrinsic ecological value.
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Tick parasitism in the Mediterranean Spur-Thighed Tortoise in the Maamora forest, Morocco.
Ticks and tick-borne diseases, 2018Co-Authors: Amalia Segura, Oscar Rodríguez, Francisco Ruiz-fons, Pelayo AcevedoAbstract:Macroparasites in general, and ectoparasites in particular, have the potential to regulate host population dynamics. In this context, this study addresses the tick parasitism traits of the Mediterranean Spur-Thighed Tortoise (Testudo graeca) in the core area of its distribution range (northwestern Morocco, Maamora). It was discovered that 92.5% of the Tortoises were parasitized by ticks in spring, with an infestation intensity and an abundance of 6.7 and 6.2 tick/Tortoise, respectively. The observed parasitization rates were among the highest reported worldwide for T. graeca, which could relate to density-depended effects driving host-parasite interactions. The main tick species that parasitized the Tortoises were Hyalomma aegyptium (95.6% of the ticks and in the 100% of the parasitized Tortoises), Hy. marginatum, Hy. excavatum and Hy. scupense. Individual predictors for the Tortoises, such as age, sex and the interaction between body condition and sex, were significantly related to tick abundance. Age-related behavioural differences might favour a higher host-tick effective contact in adults than in juveniles. The fact that males are more active in spring - the breeding season - might explain the observed male-bias in tick abundance and may also be responsible for the negative effect of male body condition on tick infestation rate in contrast to females. Given the potential role played by parasites as regards modulating population dynamics, our results suggest that ticks should be taken into account in the conservation and management programmes of this Tortoise species.
Roberto C. Rodríguez-caro - One of the best experts on this subject based on the ideXlab platform.
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Differences in Reproductive Success in Young and Old Females of a Long-Lived Species.
Animals : an open access journal from MDPI, 2021Co-Authors: Amalia Segura, Roberto C. Rodríguez-caro, Eva Graciá, Pelayo AcevedoAbstract:Long-lived species are particularly interesting for investigation of trade-offs that shape reproductive allocation and the effective contribution to the next generations. Life history theory predicts that these species will buffer environmental stochasticity via changes in the reproductive investment, while maintaining high adult survival rates. The Spur-Thighed Tortoise was selected as a case study in order to investigate the relationship between the linked maternal characteristics (size and age) and related traits in their hatchlings. We tracked naturally emerging hatchlings from young and old females under semi-natural conditions to test variations in hatchling numbers, body mass, size and survival over two years. We used linear mixed-effect models to analyze variations in hatchling body mass and size, and a mark–release–recapture framework to model their survival. Our study illustrates that old females of long-lived species have greater offspring numbers, greater survival and smaller size when compared with those of young females. The interannual variability evidenced the reduced offspring number and survival in the lower autumn rainfall and spring mean temperature year. Our results highlight the role of maternal age and climatic conditions in the population dynamics and the need for long-term studies of reproduction traits for designating adequate conservation strategies.
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From troubles to solutions: conservation of Mediterranean Tortoises under global change
Basic and Applied Herpetology, 2020Co-Authors: Eva Graciá, Roberto C. Rodríguez-caro, Marcos Ferrández, Albert Martínez-silvestre, Irene Pérez-ibarra, Rabie Amahjour, Carmen Aranda, Hadj Aissa Benelkadi, Albert Bertolero, Marta BiagginiAbstract:Chelonians are among the animal groups with the poorest conservation status. Since Tortoises are long-lived species that need very long time to reach sexual maturity, they are extremely vulnerable to human pressure. Despite their endangered status, there are no common strategies for the development of conservation actions. At the “Mediterranean workshop to develop Tortoise conservation strategies”, scientists, conservation associations, environmental managers, IUCN advisers and CITES inspectors met in October 2019 in Alicante (Spain). The aims were to update the diagnosis of the conservation status of the Hermann’s Tortoise (Testudo hermanni) and the Spur-Thighed Tortoise (Testudo graeca) and to suggest strategies that guarantee their preservation at the Mediterranean Region. The main conclusions are summarized by: i) Mediterranean Tortoises are wild endangered species that must be protected in, and together with, their natural habitat. Their main threats are habitat loss and fragmentation and pet trade, but we should also pay attention to wildfires, spread of diseases, the introduction of exotic species or lineages and climate change. ii) Long-term efforts and stablished protocols are needed to accurately diagnose and monitor the conservation status of wild populations, as well as flows among captive and wild animals. iii) Tortoise trade should be banned because it threatens the conservation of wild populations of Tortoises. Illegal practices related to Tortoises should be decidedly persecuted. People should consider Tortoises as wild animals that are endangered and deserving of protection. It is possible to enjoy them by responsibly observing them in their habitat. iv) Tortoises may carry pathogens or parasites and their sanitary status cannot be fully assessed. They should always be considered potential vectors of Tortoise diseases and of zoonosis. Hygiene protocols should be implemented when managing them. v) The researchers attending this workshop aimed to develop a scientific network for the long-term monitoring of graeca and T. hermanni populations in the Mediterranean Region. They will need the support from public administrations.
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Sperm storage reduces the strength of the mate-finding Allee effect.
Ecology and evolution, 2020Co-Authors: María V. Jiménez-franco, José D. Anadón, Andrés Giménez, Roberto C. Rodríguez-caro, Francisco Botella, Ana Sanz-aguilar, Thorsten Wiegand, Eva GraciáAbstract:Mate searching is a key component of sexual reproduction that can have important implications for population viability, especially for the mate-finding Allee effect. Interannual sperm storage by females may be an adaptation that potentially attenuates mate limitation, but the demographic consequences of this functional trait have not been studied. Our goal is to assess the effect of female sperm storage durability on the strength of the mate-finding Allee effect and the viability of populations subject to low population density and habitat alteration. We used an individual-based simulation model that incorporates realistic representations of the demographic and spatial processes of our model species, the Spur-Thighed Tortoise (Testudo graeca). This allowed for a detailed assessment of reproductive rates, population growth rates, and extinction probabilities. We also studied the relationship between the number of reproductive males and the reproductive rates for scenarios combining different levels of sperm storage durability, initial population density, and landscape alteration. Our results showed that simulated populations parameterized with the field-observed demographic rates collapsed for short sperm storage durability, but were viable for a durability of one year or longer. In contrast, the simulated populations with a low initial density were only viable in human-altered landscapes for sperm storage durability of 4 years. We find that sperm storage is an effective mechanism that can reduce the strength of the mate-finding Allee effect and contribute to the persistence of low-density populations. Our study highlights the key role of sperm storage in the dynamics of species with limited movement ability to facilitate reproduction in patchy landscapes or during population expansion. This study represents the first quantification of the effect of sperm storage durability on population dynamics in different landscapes and population scenarios.
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Assessment of the key evolutionary traits that prevent extinctions in human-altered habitats using a spatially explicit individual-based model
Ecological Modelling, 2020Co-Authors: Eva Graciá, José D. Anadón, Roberto C. Rodríguez-caro, Francisco Botella, Ana Sanz-aguilar, Angel Luis García-garcía, Thorsten Wiegand, Andrés GiménezAbstract:Abstract Identifying key evolutionary strategies that support population persistence remains a challenging task for biodiversity conservation. Here we assess if animal adaptations to cope with low densities (i.e. that facilitate mate-findings or promote spatial aggregation of individuals) can allow species to persist in human-altered habitats. A spatially explicit and individual-based model was developed to assess if, and under what circumstances, such adaptations maintain population viability. The model was parameterised with data from the movement and demography of the Spur-Thighed Tortoise (Testudo graeca) and simulated scenarios with differences in adult survivorships, initial population sizes and habitat alterations. Habitat alterations reduced population viability, and extinction rates were dependent on population characteristics and mate-finding distance. In contrast, philopatry around the birthplace did not prevent extinctions. Our results highlight the importance of considering specific spatial traits of species when assessing their vulnerability to human habitat alterations.
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Impact of habitat loss on the diversity and structure of ecological networks between oxyurid nematodes and Spur-Thighed Tortoises (Testudo graeca L.).
PeerJ, 2019Co-Authors: Julieta Benítez-malvido, Andrés Giménez, Roberto C. Rodríguez-caro, Eva Graciá, Rocío Ruiz De Ybáñez, Héctor Hugo Siliceo-cantero, Anna TravesetAbstract:Habitat loss and fragmentation are recognized as affecting the nature of biotic interactions, although we still know little about such changes for reptilian herbivores and their hindgut nematodes, in which endosymbiont interactions could range from mutualistic to commensal and parasitic. We investigated the potential cost and benefit of endosymbiont interactions between the Spur-Thighed Tortoise (Testudo graeca L.) and adult oxyurid nematodes (Pharyngodonidae order Oxyurida) in scrublands of southern Spain. For this, we assessed the association between richness and abundance of oxyurid species with Tortoises' growth rates and body traits (weight and carapace length) across levels of habitat loss (low, intermediate and high). Furthermore, by using an intrapopulation ecological network approach, we evaluated the structure and diversity of Tortoise-oxyurid interactions by focusing on oxyurid species infesting individual Tortoises with different body traits and growth rates across habitats. Overall, Tortoise body traits were not related to oxyurid infestation across habitats. Oxyurid richness and abundance however, showed contrasting relationships with growth rates across levels of habitat loss. At low habitat loss, oxyurid infestation was positively associated with growth rates (suggesting a mutualistic oxyurid-Tortoise relationship), but the association became negative at high habitat loss (suggesting a parasitic relationship). Furthermore, no relationship was observed when habitat loss was intermediate (suggesting a commensal relationship). The network analysis showed that the oxyurid community was not randomly assembled but significantly nested, revealing a structured pattern for all levels of habitat loss. The diversity of interactions was lowest at low habitat loss. The intermediate level, however, showed the greatest specialization, which indicates that individuals were infested by fewer oxyurids in this landscape, whereas at high habitat loss individuals were the most generalized hosts. Related to the latter, connectance was greatest at high habitat loss, reflecting a more uniform spread of interactions among oxyurid species. At an individual level, heavier and larger Tortoises tended to show a greater number of oxyurid species interactions. We conclude that there is an association between habitat loss and the Tortoise-oxyurid interaction. Although we cannot infer causality in their association, we hypothesize that such oxyurids could have negative, neutral and positive consequences for Tortoise growth rates. Ecological network analysis can help in the understanding of the nature of such changes in Tortoise-oxyurid interactions by showing how generalized or specialized such interactions are under different environmental conditions and how vulnerable endosymbiont interactions might be to further habitat loss.
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Mitochondrial haplotype diversity in the Tortoise species Testudo graeca from North Africa and the Middle East
BMC evolutionary biology, 2005Co-Authors: Antoinette C. Van Der Kuyl, Donato L. Ph. Ballasina, Fokla ZorgdragerAbstract:To help conservation programs of the endangered Spur-Thighed Tortoise and to gain better insight into its systematics, genetic variation and evolution in the Tortoise species Testudo graeca (Testudines: Testudinidae) was investigated by sequence analysis of a 394-nucleotide fragment of the mitochondrial 12S rRNA gene for 158 Tortoise specimens belonging to the subspecies Testudo graeca graeca, Testudo graeca ibera, Testudo graeca terrestris, and a newly recognized subspecies Testudo graeca whitei. A 411-nucleotide fragment of the mitochondrial D-loop was additionally sequenced for a subset of 22 T. graeca, chosen because of their 12S gene haplotype and/or geographical origin. Haplotype networks generated by maximum-likelihood and neighbor-joining analyses of both the separate and the combined sequence data sets suggested the existence of two main clades of Testudo graeca, comprising Testudo graeca from northern Africa and Testudo graeca from the Turkey and the Middle East, respectively. Mitochondrial DNA haplotyping suggests that the Tortoise subspecies of T. g. graeca and T. g. ibera are genetically distinct, with a calculated divergence time in the early or middle Pleistocene. Other proposed subspecies could not clearly be recognized based upon their mt haplotypes and phylogenetic position, and were either part of the T. g. graeca or of the T. g. ibera clade, suggesting that genetic evidence for the existence of most of the 15 proposed subspecies of T. graeca is weak.
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Mitochondrial haplotype diversity in the Tortoise species Testudo graeca from North Africa and the Middle East
BMC Evolutionary Biology, 2005Co-Authors: Antoinette C. Van Der Kuyl, Donato L. Ph. Ballasina, Fokla ZorgdragerAbstract:Background To help conservation programs of the endangered Spur-Thighed Tortoise and to gain better insight into its systematics, genetic variation and evolution in the Tortoise species Testudo graeca (Testudines: Testudinidae) was investigated by sequence analysis of a 394-nucleotide fragment of the mitochondrial 12S rRNA gene for 158 Tortoise specimens belonging to the subspecies Testudo graeca graeca , Testudo graeca ibera , Testudo graeca terrestris , and a newly recognized subspecies Testudo graeca whitei . A 411-nucleotide fragment of the mitochondrial D-loop was additionally sequenced for a subset of 22 T. graeca , chosen because of their 12S gene haplotype and/or geographical origin. Results Haplotype networks generated by maximum-likelihood and neighbor-joining analyses of both the separate and the combined sequence data sets suggested the existence of two main clades of Testudo graeca , comprising Testudo graeca from northern Africa and Testudo graeca from the Turkey and the Middle East, respectively. Conclusion Mitochondrial DNA haplotyping suggests that the Tortoise subspecies of T. g. graeca and T. g. ibera are genetically distinct, with a calculated divergence time in the early or middle Pleistocene. Other proposed subspecies could not clearly be recognized based upon their mt haplotypes and phylogenetic position, and were either part of the T. g. graeca or of the T. g. ibera clade, suggesting that genetic evidence for the existence of most of the 15 proposed subspecies of T. graeca is weak.