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Cox R, Phillips EK, Rakotondrazafy AFM. Gullying and landscape evolution: Lavaka in Lac Alaotra, Madagascar shed light on rates of change and non-anthropogenic controls. SCIENCE ADVANCES 2024; 10:eadi0316. [PMID: 38728401 PMCID: PMC11086618 DOI: 10.1126/sciadv.adi0316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Accepted: 04/09/2024] [Indexed: 05/12/2024]
Abstract
Gully evolution remains poorly understood, largely because multidecadal analysis is lacking. Large gullies (called lavaka) that pepper Madagascar's highlands are generally attributed to human impact; but longitudinal data are few, and anthropogenic causation is inferred not verified. We focus on Lac Alaotra, Madagascar's largest lake and wetland, its major rice-growing region, and an ecological hotspot surrounded by fault-controlled steep hills with abundant lavaka. Analysis of historical aerial photographs and recent orthoimagery reveals that the proportion of highly active lavaka has decreased since mid-20th century. At the same time, human population, farming intensity, and livestock density have increased exponentially. This suggests that background factors, including seismicity, are primary drivers of lavaka formation. Although human activities may contribute to erosion overall, land management policies that overemphasize human causation of gullying and neglect background forcing factors (in Madagascar and elsewhere) are unlikely to be effective in erosion mitigation.
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Affiliation(s)
- Rónadh Cox
- Geosciences Department, Williams College, Williamstown, MA, USA
- School of Earth Sciences, University College Dublin, Dublin, Ireland
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Joseph GS, Seymour CL. Dispersal limitation and fire feedbacks maintain mesic savannas in Madagascar: Comment. Ecology 2023; 104:e4045. [PMID: 37261396 DOI: 10.1002/ecy.4045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 10/12/2022] [Accepted: 10/20/2022] [Indexed: 06/02/2023]
Affiliation(s)
- Grant S Joseph
- Percy FitzPatrick Institute of African Ornithology, DST/NRF Centre of Excellence, Department of Biological Sciences, University of Cape Town, Cape Town, South Africa
| | - Colleen L Seymour
- Percy FitzPatrick Institute of African Ornithology, DST/NRF Centre of Excellence, Department of Biological Sciences, University of Cape Town, Cape Town, South Africa
- South African National Biodiversity Institute, Kirstenbosch Research Centre, Claremont, South Africa
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Salmona J, Dresen A, Ranaivoson AE, Manzi S, Le Pors B, Hong-Wa C, Razanatsoa J, Andriaholinirina NV, Rasoloharijaona S, Vavitsara ME, Besnard G. How ancient forest fragmentation and riparian connectivity generate high levels of genetic diversity in a microendemic Malagasy tree. Mol Ecol 2023; 32:299-315. [PMID: 36320175 PMCID: PMC10100191 DOI: 10.1111/mec.16759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Revised: 10/13/2022] [Accepted: 10/17/2022] [Indexed: 11/07/2022]
Abstract
Understanding landscape changes is central to predicting evolutionary trajectories and defining conservation practices. While human-driven deforestation is intense throughout Madagascar, exceptions in areas such as the Loky-Manambato region (north) raise questions regarding the causes and age of forest fragmentation. The Loky-Manambato region also harbours a rich and endemic flora, whose evolutionary origin remains poorly understood. We assessed the genetic diversity of an endangered microendemic Malagasy olive species (Noronhia spinifolia Hong-Wa) to better understand the vegetation dynamics in the Loky-Manambato region and its influence on past evolutionary processes. We characterized 72 individuals sampled across eight forests through nuclear and mitochondrial restriction-associated DNA sequencing data and chloroplast microsatellites. Combined population and landscape genetics analyses indicate that N. spinifolia diversity is largely explained by the current forest cover, highlighting a long-standing habitat mosaic in the region. This sustains a major and long-term role of riparian corridors in maintaining connectivity across these antique mosaic habitats, calling for the study of organismal interactions that promote gene flow.
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Affiliation(s)
- Jordi Salmona
- CNRS-UPS-IRD, UMR5174, Laboratoire Évolution & Diversité Biologique, Université Paul Sabatier, Toulouse, France
| | - Axel Dresen
- CNRS-UPS-IRD, UMR5174, Laboratoire Évolution & Diversité Biologique, Université Paul Sabatier, Toulouse, France
| | - Anicet E Ranaivoson
- CNRS-UPS-IRD, UMR5174, Laboratoire Évolution & Diversité Biologique, Université Paul Sabatier, Toulouse, France.,Faculté des Sciences, Université de Mahajanga, Mahajanga, Madagascar
| | - Sophie Manzi
- CNRS-UPS-IRD, UMR5174, Laboratoire Évolution & Diversité Biologique, Université Paul Sabatier, Toulouse, France
| | | | - Cynthia Hong-Wa
- Claude E. Phillips Herbarium, Delaware State University, Dover, Delaware, USA
| | - Jacqueline Razanatsoa
- Herbier, Département Flore, Parc Botanique et Zoologique de Tsimbazaza, Antananarivo, Madagascar
| | | | | | | | - Guillaume Besnard
- CNRS-UPS-IRD, UMR5174, Laboratoire Évolution & Diversité Biologique, Université Paul Sabatier, Toulouse, France
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Culbertson KA, Treuer TLH, Mondragon‐Botero A, Ramiadantsoa T, Reid JL. The eco‐evolutionary history of Madagascar presents unique challenges to tropical forest restoration. Biotropica 2022. [DOI: 10.1111/btp.13124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Katherine A. Culbertson
- Department of Environmental Science, Policy, and Management University of California Berkeley California USA
| | | | | | - Tanjona Ramiadantsoa
- Department of Life Science University of Fianarantsoa Fianarantsoa Madagascar
- Department of Mathematics University of Fianarantsoa Fianarantsoa Madagascar
- Department of Integrative Biology University of Wisconsin‐Madison Madison Wisconsin USA
| | - J. Leighton Reid
- School of Plant and Environmental Sciences Blacksburg Virginia USA
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Hansford JP, Turvey ST. Dietary isotopes of Madagascar's extinct megafauna reveal holocene browsing and grazing guilds. Biol Lett 2022; 18:20220094. [PMID: 35414222 PMCID: PMC9006009 DOI: 10.1098/rsbl.2022.0094] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Megafauna play a disproportionate role in developing and maintaining their biomes, by regulating plant dispersal, community structure and nutrient cycling. Understanding the ecological roles of extinct megafaunal communities, for example through dietary reconstruction using isotope analysis, is necessary to determine pre-human states and set evidence-based restoration goals. We use δ13C and δ15N isotopic analyses to reconstruct Holocene feeding guilds in Madagascar's extinct megaherbivores, which included elephant birds, hippopotami and giant tortoises that occurred across multiple habitats and elevations. We compare isotopic data from seven taxa and two elephant bird eggshell morphotypes against contemporary regional floral baselines to infer dietary subsistence strategies. Most taxa show high consumption of C3 and/or CAM plants, providing evidence of widespread browsing ecology. However, Aepyornis hildebrandti, an elephant bird restricted to the central highlands region, has isotope values with much higher δ13C values than other taxa. This species is interpreted as having obtained up to 48% of its diet from C4 grasses. These findings provide new evidence for distinct browsing and grazing guilds in Madagascar's Holocene megaherbivore fauna, with implications for past regional distribution of ecosystems dominated by endemic C4 grasses.
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Affiliation(s)
- James P Hansford
- Institute of Zoology, Zoological Society of London, Regent's Park, London NW1 4RY, UK.,Department of Biological Sciences, Northern Illinois University, DeKalb, IL 60115, USA.,School of Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, UK
| | - Samuel T Turvey
- Institute of Zoology, Zoological Society of London, Regent's Park, London NW1 4RY, UK
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Joseph GS, Rakotoarivelo AR, Seymour CL. Tipping points induced by palaeo-human impacts can explain presence of savannah in Malagasy and global systems where forest is expected. Proc Biol Sci 2022; 289:20212771. [PMID: 35350853 PMCID: PMC8965410 DOI: 10.1098/rspb.2021.2771] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Models aimed at understanding C4-savannah distribution for Australia, Africa and South America support transition to forest at high mean annual precipitation (MAP), and savannah grasslands of Madagascar have recently been reported to be similarly limited. Yet, when savannah/grassland presence data are plotted against MAP for the various ecosystems across the Malagasy Central Highlands, the relationship does not hold. Furthermore, it does not always hold in other sites on other continents. Instead, in high-rainfall savannahs, palaeo-human impacts appear to have selected a fire-adapted habitat, creating tipping points that allow savannah persistence despite high rainfall, suppressing forest return. We conducted the largest systematic literature review to date for global evidence of palaeo-human impacts in savannahs, and conclude that impacts are widespread and should be incorporated into models aimed at understanding savannah persistence at elevated precipitation, particularly as more palaeodata emerges. Building on existing studies, we refine the MAP savannah relationship at higher MAP. Palaeoanthropogenic impact can help explain inconsistencies in the savannah/forest boundary at higher MAP, and points to a key role for palaeoecology in understanding systems. Including these effects presents a crucial change to our understanding of factors determining global savannah distribution, supporting a human hand in much of their formation.
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Affiliation(s)
- Grant S. Joseph
- FitzPatrick Institute of African Ornithology, DSI-NRF Centre of Excellence, Department of Biological Sciences, University of Cape Town, Rondebosch 7701, South Africa
| | - Andrinajoro R. Rakotoarivelo
- Afro-mountain Research Unit, The University of the Free State Qwaqwa, Private Bag X13, Phuthaditjhaba 9866, Republic of South Africa,Natiora Ahy, Lot IIU57 K Bis, Ampahibe, Antananarivo 101, Madagascar
| | - Colleen L. Seymour
- FitzPatrick Institute of African Ornithology, DSI-NRF Centre of Excellence, Department of Biological Sciences, University of Cape Town, Rondebosch 7701, South Africa,South African National Biodiversity Institute, Kirstenbosch Research Centre, Private Bag X7, Claremont 7735, South Africa
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Tofanelli S, Bertoncini S, Donati G. Early Human Colonization, Climate Change and Megafaunal Extinction in Madagascar: The Contribution of Genetics in a Framework of Reciprocal Causations. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2021.708345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Wiorek M, Malik K, Lees D, Przybyłowicz Ł. Malagasy Polka Dot Moths (Noctuoidea: Erebidae: Arctiinae: Syntomini) of Ambohitantely-endemism in the most important relict of Central Plateau rainforest in Madagascar. PeerJ 2021; 9:e11688. [PMID: 34239780 PMCID: PMC8240653 DOI: 10.7717/peerj.11688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 06/07/2021] [Indexed: 11/20/2022] Open
Abstract
Malagasy Syntomini (Polka Dot Moths) are one of the largest endemic lineages of Lepidoptera on the island, belonging to the Tiger Moth subfamily (Arctiinae). This diverse radiation comprises nearly 100 valid described species that share a single ancestor. Despite a monograph in 1964 by Paul Griveaud, systematics of the group greatly needs modern revision, and their distribution on the island is still poorly known. This contribution concerns the diversity of Syntomini of the Réserve Spéciale d'Ambohitantely, which protects the largest remaining, but already highly fragmented, vestige of Central Plateau rainforest in Madagascar. Here we provide an annotated checklist of the eight species occurring in the Reserve. Two species are recorded from the forest for the first time, while five endemics are until now known only from Ambohitantely. We also describe for the first time the female of Thyrosticta vestigii Griveaud, 1964 and of Maculonaclia tampoketsya Griveaud, 1969, as well as a yellow morphotype of Thyrosticta dilata Griveaud, 1964, and we redescribe and illustrate the genitalia of the remaining species. The significance of such colour pattern variation in aposematic moths and the role of this Reserve as a local centre of diversity of Malagasy Syntomini together with its importance in the protection of the biodiversity of Madagascar are discussed.
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Affiliation(s)
- Marcin Wiorek
- Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Kraków, Poland
| | - Kamila Malik
- Department of Invertebrate Evolution, Institute of Zoology and Biomedical Research, Jagiellonian University, Kraków, Poland
| | - David Lees
- Department of Life Sciences, Natural History Museum, London, United Kingdom
| | - Łukasz Przybyłowicz
- Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Kraków, Poland
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