Entité de rattachement
Interactions et Evolution Végétale et Fongique (INEVEF)

Contact

Courriel
sabine.hennequin [at] mnhn.fr
Téléphone
01 40 79 80 58
Fax
01 40 79 37 39
Adresse(s)

57 rue Cuvier

CP48

75005 Paris

Enseignements

Présentation

Presentation

bandeau Sabine Hennequin © MNHN

Research

I study evolutionary patterns and processes in seed-free plants belonging to the ferns and lycophytes. This involves reconstructing evolutionary relationships between lineages (phylogenies), which can be used to understand morphological evolution, biogeography and adaptation to particular habitats. Whenever available, fossils are used to calibrate these phylogenies, thus providing the time scale for evolutionary events. A second part of my research interests focuses on the assembly of diversity on oceanic islands, in other words, its geographical whereabouts, the role of immigration or speciation and how it is phylogenetically structured.

The assembly of fern diversity in the Mascarene Islands

Mountain rainforest at La Grande Montée, with the tree ferns Cyathea glauca emerging from the canopy © S. Hennequin

Mountain rainforest at La Grande Montée, with the tree ferns Cyathea glauca emerging from the canopy

Crédits
S. Hennequin

 The Mascarene Islands consist of three main islands (La Réunion, Mauritius and Rodrigues) located east of Madagascar in the Indian Ocean and part of the South West Indian Ocean hotspot of biodiversity and endemism. Although these oceanic islands share similar geological history, they differ in size, elevation profile, age, distance to the nearest larger land mass (Madagascar) and biodiversity. Ferns are well known for their high dispersal capacity as a result of their reproductive biology, which includes the formation of small meiospores and potentially hermaphrodite gametophytes. Consequently, frequent colonization by ferns from Madagascar and other areas around the Indian Ocean, or even further, is expected, as well as exchange between the Mascarene islands. Indeed, ferns make up an important component of the diverse flora of the Mascarenes, especially in the rain forests, with more than 240 reported species, among which 20% are endemic to these islands. After the Hawaiian Islands, the Mascarenes are the oceanic islands with the highest fern diversity, making them especially suited to study fern evolution in a real-scale Darwinian laboratory. The objectives of this study are multiple : to investigate the patterns of fern diversification in the Mascarene Islands, especially groups undergoing cladogenesis, to identify the processes of island community assembly and to investigate characteristics (such as morphology and life forms) that may be related to better chances of colonization versus speciation.

Erica mountain thicket with Sphagnum (“avoune” type) © L. Echternacht

Erica mountain thicket with Sphagnum (“avoune” type)

Crédits
L. Echternacht
Cyathea glauca (Cyatheaceae) or “fanjan femelle”, an emblematic tree fern endemic to La Réunion © S. Hennequin

Cyathea glauca (Cyatheaceae) or “fanjan femelle”, an emblematic tree fern endemic to La Réunion

Crédits
S. Hennequin

This project has been funded by two ATM of the MNHN Paris (2010-2012), the British Council Darwin Now Award (2009), and a Marie Curie Intra-European Fellowship (2008-2010).

This project is currently expanded to the whole South-West Indian Ocean Region, including Madagascar, in collaboration with G. Rouhan. In addition, we are collaborating with a Brazilian team (A. Salino, UFMG Brazil) with a view to comparing how fern diversity is assembled in two geographically distinct areas sharing similar ecology : the Indian Ocean region and the Atlantic Forest in Brazil.

Fern systematics, biogeography and evolution

In relation to my project on the ferns from the Mascarene Islands, I am interested in reconstructing the evolutionary relationships in several groups of ferns, especially the genus Ctenitis (Dryopteridaceae) which appears to have radiated in the Indian Ocean region and in the Mascarenes, and the families Thelypteridaceae and Polypodiaceae.

Main coll. : H. Schneider (NHM London), J.-Y. Dubuisson, M. Gaudeul & G. Rouhan (UMR 7205), A. Salino (UFMG, Brazil), A. Ebihara (National Museum of Nature and Science,Tokyo, T. Ranker (U. of Colorado).

Amauropelta heteroptera, Grammitis melanoloma, Ctenitis crinita © L.Echternacht

(4.) Amauropelta heteroptera (Thelypteridaceae), endemic to La Réunion -
(5.) Grammitis melanoloma (Polypodiaceae), an epiphyte endemic to La Réunion, showing round nude sori and characterized by a black margin -

(6.) Ctenitis crinita (Dryopteridaceae) and sori, endemic to Mauritius. According to our results this genus radiated in the Mascarenes.

Crédits
L. Echternacht

This is not to forget my first research interest : the Hymenophyllaceae, or filmy ferns, easily recognized by their very thin leaves (typically one-cell thick) and their marginal sori. During my Ph.D. I studied a genus of the family, Hymenophyllum, which includes approximately 300 species. The phylogeny inferred allowed to propose a new classification for the genus. I was also especially interested in the evolution of morphological characters within the genus, and deciphering its complex biogeographical history is still underway. This requires broadening the taxon sampling of the inferred phylogeny and acquiring nuclear markers. I also draw my attention to the issue of chromosome numbers evolution in the genus, where very variable numbers are reported with n = 11, 12, 13, 14, 18, 21, 22, 26, 28, 36. (coll. J.-Y. Dubuisson, UMR7205 and A. Ebihara, National Museum of Nature and Science, Japan).

Hymenophyllum decurrens (Hymenophyllaceae) © J.-Y. Dubuisson

Hymenophyllum decurrens (Hymenophyllaceae) from Guadeloupe grows as an epiphyte, as nearly all other Hymenophyllum species

Crédits
J.-Y. Dubuisson
Chromosome number evolution in Hymenophyllum © MNHN

Chromosome number evolution in Hymenophyllum

Crédits
MNHN

Another project targeted molecular rate heterogeneity between the two lineages of Hymenophyllaceae : hymenophylloids (= Hymenophyllum) and trichomanoids. We demonstrated that there is a slow-down in the molecular evolutionary rate in the hymenophylloids, and that this phenomenon occurs not only at the chloroplast level, but also seems to take place on the mitochondrion and nuclear levels. With a view to understanding the causes for this deceleration of rate, we investigated the evolutionary history in the family by estimating divergence times and by reconstructing the evolution of the different habitats found in the family (terrestrial, hemiepiphytic and epiphytic). Our results imply that filmy ferns were ancestrally terrestrial and that epiphytism evolved several times independently in the family during the Cretaceous and the Tertiary. Coll. K. Pryer (Duke University) and E. Schuettpelz (U. North Carolina).

Together with J.-Y. Dubuisson, we are further investigating morphological and anatomical evolution in the trichomanoids in relation to habitat. We also aim to propose a biogeographical scenario for the history of the lineage.

Habitat evolution and divergence times in Hymenophyllaceaem © MNHN

Habitat evolution and divergence times in Hymenophyllaceaem

Crédits
MNHN

Fieldwork

Fieldwork is an essential part of my work in order to obtain material of the studied species and to understand their ecological preferences. Collected specimens are preserved as herbarium specimen, contributing to enriching the herbarium collections of the MNHN Paris, and as silica-dried material for DNA-based studies.

  • Mata Atlantica, Brazil : 2013
  • La Réunion : 2002, 2009, 2010
  • Mauritius : 2009, 2010
  • Guadeloupe : 2006
  • Canary Islands : 2010
  • Madeira : 2004
Collecting Ctenitis maritima in La Réunion (endemic to the Mascarenes) © L. Echternacht

Collecting Ctenitis maritima in La Réunion (endemic to the Mascarenes)

Crédits
L. Echternacht

Publications

2022
  • Dubuisson Jean-Yves, Péchon Timothée Le, Hennequin Sabine, Rouhan Germinal, Salino Alexandre, Deblauwe Vincent, Droissart Vincent, Tuomisto Hanna, Lehtonen Samuli & Ebihara Atsushi, 2022New insights into the diversity, taxonomy and history of the fern genus Trichomanes (Hymenophyllaceae, Polypodiidae), with a focus on Africa and the western Indian Ocean. Botanical Journal of the Linnean Society vol. 198, n° 2, p. 215-239
    ISSN
    0024-4074, 1095-8339
  • Hennequin Sabine, Faillace Thiesen Julia, Le Pechon Timothée, Stauffer Viveros Raquel, Salino Alexandre, Wood Kenneth R. & Ranker Tom A., 2022Origin of Hawaiian ferns of the genus Ctenitis (Dryopteridaceae). Botany Letters vol. 169, n° 3, p. 375-389
    ISSN
    2381-8107, 2381-8115
  • Dubuisson Jean-Yves, Boucheron-Dubuisson Elodie, Le Pechon Timothee, Bausero Pedro, Droissart Vincent, Deblauwe Vincent, Ebihara Atsushi, Hennequin Sabine & Rouhan Germinal, 2022Diversity and taxonomy of the fern genus Vandenboschia Copel. (Hymenophyllaceae, Polypodiidae) in the Afro-Malagasy region and description of a new species. BOTANY LETTERS vol. 169, n° 2, p. 268-283 tex.earlyaccessdate: APR 2022 tex.eissn: 2381-8115 tex.orcid-numbers: Rouhan, Germinal/0000-0002-0751-5352 Droissart, Vincent/0000-0001-9798-5616 tex.researcherid-numbers: Rouhan, Germinal/P-4717-2019 Droissart, Vincent/K-2507-2016 tex.unique-id: WOS:0007
    ISSN
    2381-8107
2021
  • Almeida Thais, Salino Alexandre, Dubuisson Jean-Yves & Hennequin Sabine, 2021Insights into long-distance dispersal and ecological and morphological evolution in the fern genus Microgramma from phylogenetic inference. Botanical Journal of the Linnean Society , , p. 1-19
  • Dubuisson Jean-yves & Hennequin Sabine, 2021Correction for the taxonomy of the African fern Hymenophyllum senterreanum as synonym of the newly validated Hymenophyllum mildbraedii (Hymenophyllaceae, Polypodiidae). Phytotaxa vol. 522, n° 3, p. 263-264
    ISSN
    1179-3155
  • Almeida Thais Elias, Salino Alexandre, Dubuisson Jean-Yves & Hennequin Sabine, 2021Insights into long-distance dispersal and ecological and morphological evolution in the fern genus Microgramma from phylogenetic inference. Botanical Journal of the Linnean Society vol. 196, n° 3, p. 294-312
    ISSN
    0024-4074
2020
  • Liu Hongmei, Rakotondrainibe France, Hennequin Sabine & Schneider Harald, avril 2020The significance of Rouxopteris (Gleicheniaceae, Polypodiopsida): a new genus endemic to the Madagascan region. Gleichenia boryi is a poorly known species of Gleicheniaceae endemic to Madagascar and La Réunion Island. Although Kunze… Plant Systematics and Evolution vol. 306, n° 2, p. 30 ISBN: 0378-2697 Publisher: Springer Verlag (Germany) Type: 10.1007/s00606-020-01657-9
    ISSN
    0378-2697, 2199-6881
  • Almeida Thais, Salino Alexandre, Dubuisson Jean-Yves & Hennequin Sabine, 2020Insights on long-distance dispersal, ecological and morphological evolution in the fern genus Microgramma from phylogenetic inferences. Préprint. , , dir. bioRxiv
2018
  • Wei Ran, Ebihara Atsushi, Zhu Yan-Mei, Zhao Cun-Feng, Hennequin Sabine & Zhang Xian-Chun, 2018A total-evidence phylogeny of the lady fern genus Athyrium Roth (Athyriaceae) with a new infrageneric classification. Molecular Phylogenetics and Evolution vol. 119, , p. 25-36
    ISSN
    1055-7903
  • Dubuisson J.-Y. & Hennequin S., 2018Correction for the taxonomy of Trichomanes foeniculaceum as synonym of Abrodictyum parviflorum (Hymenophyllaceae, Polypodiidae). Phytotaxa vol. 343, n° 1, p. 99-100
    ISSN
    11793163