Ancient DNA elucidates the lost world of western Indian Ocean giant tortoises and reveals a new extinct species from Madagascar

Kehlmaier, Christian; Graciá, Eva; Ali, Jason R.; Campbell, Patrick D.; Chapman, Sandra D.; Veerappan, Deepak; Ihlow, Flora; Pierre-Huyet, Laure; Samonds, Karen E.; Vences, Miguel; Fritz, Uwe

doi:10.1126/sciadv.abq2574

Cited by 12 publications

(9 citation statements)

References 78 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One can envisage similar landscapes pre‐contact in Madagascar. Recent phylogenetic studies of Malagasy tortoises reveal an out of Africa radiation of three species with divergent niches (Kehlmaier et al, 2023). However, we know very little about the ecology of these extinct giant tortoises in Madagascar, and no tortoise samples have been analyzed from the primarily open, grassy ecosystems of the Central Highlands.…”

Section: Biodiversity Of Grassy Ecosystems In Madagascarmentioning

confidence: 99%

The grassy ecosystems of Madagascar in context: Ecology, evolution, and conservation

Silander,

Bond,

Ratsirarson

2023

Plants People Planet

View full text Add to dashboard Cite

Societal Impact StatementMadagascar is famous for its unique forests and their fauna. Most of the island is covered by flammable grassy ecosystems long considered to be of human origin and threatening the remaining forests. Yet new studies show that many plants and animals of the grassy systems are unique to Madagascar and restricted to these open habitats. Open grassy ecosystems have markedly different management requirements from forests and bring different contributions to society. We argue that the grassy ecosystems can benefit Madagascar if understood and managed wisely using expanded knowledge bases that also include collaboration with locals.SummaryUntil recently, nearly all research and interests in Madagascar focused on forested habitats. To help place Madagascar's grassy ecosystems in context, we provide a summary of the origin, development, and evolution of open tropical, C4 grassy ecosystems elsewhere, especially those from Africa; we summarize similarities and differences with the distribution of C3 and C4 grasses in the Malagasy landscape, their plant traits, and inferences on the evolutionary legacy of grasses. We also discuss the animal communities that use and have coevolved in these grassy systems; to help resolve controversies over the pre‐settlement extent of grassy ecosystems, we suggest a variety of complementary geochemical, palaeobotanical, and molecular genetic tools that have been effectively used elsewhere to untangle forest/grassy ecosystem mosaics and the ecological and evolutionary processes that influence them. Many of these tools can and should be employed in Madagascar to fully understand the spatio‐temporal dynamics of open, grassy, and closed forest systems across the island; as regards conservation, we discuss the ecosystem services provided by grassy systems, which are too often ignored in general, not only as a biome, vis‐à‐vis forests, but also for their global importance as a carbon sink and role they play in water management and providing goods to local villagers. We conclude by outlining the necessary research to better manage open ecosystems across Madagascar without threatening endangered forest ecosystems.

show abstract

Section: Biodiversity Of Grassy Ecosystems In Madagascarmentioning

confidence: 99%

The grassy ecosystems of Madagascar in context: Ecology, evolution, and conservation

Silander,

Bond,

Ratsirarson

2023

Plants People Planet

View full text Add to dashboard Cite

show abstract

“…Indeed, A. gigantea may assist in restoring megafauna‐dependent seed dispersal and germination of endemic trees ( A. gigantea consumed over 70% of fruit of Adansonia rubrostipa ; Pedrono et al, 2013; Andriantsaralaza et al, 2014). The reintroduction of Aldabrachelys to Madagascar was inspired by phylogeographic confirmation of Aldabrachelys gigantea as the closest surviving relative of extinct Malagasy A. abrupta (Kehlmaier et al, 2023; Pedrono et al, 2022) and improved insights into the central functional roles played by giant tortoises in shaping Malagasy ecosystems. With the aim of ultimately re‐establishing historical numbers that foster ecosystem resilience and biodiversity (Pedrono et al, 2013), five male and seven female subadult Aldabrachelys were released into Anjajavy Reserve, in north‐west Madagascar, in 2018, with Malagasy government support.…”

Section: Introductionmentioning

confidence: 99%

Can rewilding with giant tortoises increase woody habitat and limit fire across Madagascar's grasslands?

Joseph,

Rakotoarivelo,

Pedrono

et al. 2024

Plants People Planet

View full text Add to dashboard Cite

Societal Impact StatementTo better understand the impact of human settlement on vegetation distribution and disturbance regimes in Madagascar, the 2021 Malagasy Grassy Biomes Workshop called for an examination of the role of extinct megafauna in determining the historic distribution of habitat mosaics across regions that are today dominated by vast treeless grasslands. A systematic literature review facilitated the reconstruction and evaluation of giant tortoise habitat, feeding habitats, diets and Aldabrachelys tortoise impacts on disturbance regimes. In conclusion, reintroduction of mixed‐feeding Aldabrachelys (the diets of which were often dominated by C3 woody material, but never by C4 grasses, across its range), will likely impact plant species composition, select a tree‐rich habitat mosaic, reduce fire frequency, re‐establish lost ecological functions and improve landscape productivity at a range of scales, including rangeland palatability, benefitting both biodiversity and human wellbeing.SummaryGrasslands with little tree cover today comprise 80% of Madagascar's habitat. Determining their extent at human settlement can guide ecological restoration and enhance human well‐being, so the 2021 Malagasy Grassy Biomes Workshop identified the role of extinct megafauna in determining habitat as a critical knowledge gap. Using a systematic literature review, combined with extracted datasets, we address this, examining anticipated habitat selection by giant tortoises following reintroduction to Madagascar (where the Aldabran giant tortoise, Aldabrachelys gigantea, provides ecological functions lost when A. abrupta and A. grandidieri went extinct). When comparing current and historical tortoise selection of habitat across the Mascarenes and Aldabra with contemporary Malagasy habitat, areas in Madagascar where giant tortoises historically ranged, today have a significantly different habitat composition to the forested habitat that supported giant tortoises on other islands. Dietary 13C isotope ratios show that Malagasy Aldabrachelys and Mascarene tortoises were mixed feeders, with diets often dominated by C3 woody intake, but never by C4 grasses. Across systems, giant tortoises required and selected, tree‐rich habitat mosaics, different to current pastoralist fire‐selected Malagasy grasslands characterized by sparse tree cover. Furthermore, Aldabran Aldabrachelys tortoise turf, restricted to small areas (large tracts of unshaded vegetation present physiological challenges to Aldabrachelys' survival), is compositionally different to Malagasy and African obligate C4 grazing lawns. Ecological, palaeoecological, geomorphological and molecular evidence support a lost Malagasy habitat mosaic where hippo and tortoise diets were C3‐dominated, because they inhabited closed‐canopy systems, with abutting open‐canopy areas harbouring endemic‐rich, C4 grassy understories and limited grasslands. The review suggests that rewilding with A. gigantea will help restore ecological functions, productivity and landscape‐scale degradation lost through cattle‐based pastoralism, re‐establish tree‐rich habitat mosaics, and mitigate against frequent bushfires, benefiting biodiversity and humans at multiple scales.

show abstract

“…For example, a phylogeny obtained from 98 mitogenomes has contributed to address how ancestral extinctions, niche diversity and biogeography have impacted extant diversity (16).…”

Section: Introductionmentioning

confidence: 99%

“…However, microevolutionary processes like gene flow, genomic recombination, introgression or hybridization cannot be extensively addressed using only mitogenomes trees (16). Nuclear reference genomes are also becoming increasingly available.…”

Section: Introductionmentioning

confidence: 99%

“…Genetic and genomic resources for chelonians have increased over the past few years. For example, a phylogeny obtained from 98 mitogenomes has contributed to address how ancestral extinctions, niche diversity and biogeography have impacted extant diversity (16). However, microevolutionary processes like gene flow, genomic recombination, introgression or hybridization cannot be extensively addressed using only mitogenomes trees (16).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Taking advantage of reference-guided assembly in a slowly-evolving lineage: application to Testudo graeca

Mira-Jover,

Graciá,

Giménez

et al. 2024

Preprint

Self Cite

View full text Add to dashboard Cite

Background Obtaining de novo chromosome-level genome assemblies greatly enhances conservation and evolutionary biology studies. For many research teams, long-read sequencing technologies (that produce highly contiguous assemblies) remain unaffordable or unpractical. For the groups that display high synteny conservation, these limitations can be overcome by a reference-guided assembly using a close relative genome. Of chelonians, terrestrial tortoises are considered one of the most endangered taxa, which calls for more genomic resources. Here we make the most of high synteny conservation in chelonians to produce the first chromosome-level genome assembly of genus Testudo with one of the most iconic tortoise species in the Mediterranean basin: T. graeca. Results We used high quality, paired-end Illumina sequences to build a reference-guided assembly with the chromosome level assembly of Gopherus evgoodei. We reconstructed a 2.29 Gb haploid genome with a scaffold N50 of 107.598 Mb and 5.37% gaps. We sequenced 25998 protein-coding genes, and a 41.2% fraction was determined as repetitive in our assembled genome. Demographic history reconstruction based on the genome revealed two events (population decline and recovery) consistent with previously suggested phylogeographic patterns for the species. This outlines the value of genomes like this for phylogeographic studies. Conclusions Our results highlight the value of using close relatives to produce de novo draft assemblies in species where such resources are unavailable. Our Testudo graeca annotated genome paves the way to delve deeper into the species' evolutionary history and provides a valuable resource to increase making direct conservation efforts on their threatened populations.

show abstract

Ancient DNA elucidates the lost world of western Indian Ocean giant tortoises and reveals a new extinct species from Madagascar

Cited by 12 publications

References 78 publications

The grassy ecosystems of Madagascar in context: Ecology, evolution, and conservation

The grassy ecosystems of Madagascar in context: Ecology, evolution, and conservation

Can rewilding with giant tortoises increase woody habitat and limit fire across Madagascar's grasslands?

Taking advantage of reference-guided assembly in a slowly-evolving lineage: application to Testudo graeca

Contact Info

Product

Resources

About