Oral communication 1 : Morphometrics and ontogenetic growth of Forest and Savannah African elephants
Oral communication 2 : Phylogeography of Forest and Savannah African elephants

Abstract

Abstract

Debruyne Régis
2005. in Abstracts of Plenary, Symposium, Poster and Oral Papers (International Mammalogical Congress 9). The Science Council of Japan and the Mammalogical Society of Japan, Sapporo, pp.27-28.

Abstract

A case study of apparent controversy between molecular phylogenies: the interrelationships of African elephants.
Debruyne, Régis.
Cladistics 2005, 21(1):31-50.

Abstract

Recent molecular phylogenies of the African elephants suggest that there is an evolutionary structure within Loxodonta africana. Some nuclear results (Roca et al., 2001) support the separation of the forest African elephant subspecies L. a. cyclotis as a species distinct from the savannah elephant L. a. africana, on the basis of the recognition of both forming highly divergent (reciprocally monophyletic) clades. Conversely, a mitochondrial survey (Eggert et al., 2002), while admitting a geographic partitioning of the genetic structure within African elephants, suggests retaining the status quo. They recognize three diagnosible entities (western, central and south-eastern Africa) with non-overlapping ranges within L. africana sensu lato. In order to address these conflicting views (historical fragmentation and speciation or isolation by distance, respectively), we have sequenced two datasets of 1961 bp (for 50 elephants) and about 3700 bp, respectively (for 20 elephants) of the mitochondrial DNA for both forms of elephants (cyclotis and africana). They span the cytochrome b gene, the control region and several RNAs. When compared with former mtDNA data, they provide the most comprehensive view of the African elephant phylogeny (78 mtDNA haplotypes, of which 44 are new) and provide the first insight into populations from the Democratic Republic of Congo. The genetic diversity of mtDNA was appraised and the stability of alternative phylogenetic trees was investigated. Our results are inconsistent with both those prior studies. They revealed two highly divergent molecular clades referred to as F and S, that do not conform to the morphological delineations of cyclotis and africana. A non-negligible proportion of specimens of L. a. africana display haplotypes prevailing in forest elephant populations (clade F). The geographic distribution of clades and areas of their co-occurrence support the hypothesis of incomplete isolation between forest and savannah African elephant populations, followed by recurrent interbreeding between the two forms. We state that the conclusions of prior studies resulted from insufficient character and ⁄ or geographic sampling. We conclude that there is no satisfying argument which can recognize two or more species of African elephants. We briefly comment on the meaning of such an attitude in a conservation viewpoint.Original material

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Abstract

African elephants are conventionally classified as a single species: Loxodonta africana (Blumenbach 1797). However, the discovery in 1900 of a smaller form of the African elephant, spread throughout the equatorial belt of this land, has given rise to a debate over the relevance of a second species of elephant in Africa. The twentieth century has not provided any definite answer to this question. Actually, recent molecular analyses have sustained this issue by advocating either a division of forest elephants into a valid species, or their inclusion as a subspecies of L. africana. Our work initiated at the National Museum of Natural History of Paris provides new molecular (mitochondrial) and morphological (and morphometrical) evidence making it possible to propose a comprehensive phylogenetic hypothesis. It appears that there is no conclusive argument to keep forest elephants (cyclotis form) and savannah elephants (africana form) apart in two distinct species. A high level of mitochondrial introgression between the two forms, as well as a continuum in the morphology of the skulls of the two morphotypes rather suggests that, despite an ancient division, these two taxa freely interbreed wherever their ranges intersect. We thus adopt a conservative systematic position in considering these two forms as two subspecies, respectively: L. africana africana, the savannah elephant, and L. africana cyclotis, the forest elephant. We finally discuss the conservation topic in the light of this systematic framework.

Résumé

Les éléphants d’Afrique sont classiquement rangés dans une seule espèce : Loxodonta africana (Blumenbach 1797). Toutefois, la découverte en 1900 d’une forme plus petite de l’éléphant d’Afrique, répandue dans toute la frange équatoriale du continent, a suscité un débat quant à l’éventualité d’une deuxième espèce d’éléphant en Afrique. Ce débat n’a pas trouvé de réponse définitive au cours du vingtième siècle. De fait, de récentes analyses moléculaires des populations d’éléphants d’Afrique sont venues jeter le trouble en prônant soit une séparation des éléphants de forêt dans une espèce à part entière, soit leur inclusion en tant que sous-espèce de L. africana. Notre travail initié au Muséum National d’Histoire Naturelle de Paris permet d’apporter de nouveaux arguments moléculaires (mitochondriaux) et morphologiques (et morphométriques) afin de produire une hypothèse phylogénétique cohérente au vu de toutes les données disponibles. Il apparaît qu’il n’existe à ce jour aucun argument satisfaisant pour séparer les éléphants de forêt (forme cyclotis) et les éléphants de savane (forme africana) dans deux espèces distinctes. En revanche, un niveau élevé d’introgression mitochondriale entre les deux formes, associé à l’existence d’un continuum de forme entre les crânes des deux morphotypes, suggère que ces deux taxons, malgré une divergence ancienne, se croisent librement là où leurs aires de distribution se rencontrent. Nous adoptons donc une position systématique conservatrice de ces deux formes comme des sous-espèces, respectivement : L. africana africana, l’éléphant de savane, et L. africana cyclotis, l’éléphant de forêt. Nous discutons le point de la conservation des éléphants dans ce cadre systématique.

Abstract

Retrouvez des extraits de l’émission au format .mp3:

• Extrait 1 [2'10]: introduction
• Extrait 2 [3'40]: the extinction of mammoths
• Extrait 3 [3'15]: the risks of extinction for the elephants
• Extrait 4 [1'50]: differences between Africa and Asia
• Extrait 5 [3'15]: mortuary rites and elephant society
• Extrait 6 [0'55]: genetics and inbreeding

Oral presentation:

Status of the so-called African pygmy elephant (Loxodonta pumilio (Noack, 1906)): phylogeny of cytochrome b and mitochondrial control region sequences.
Debruyne Régis, Arnaud Van Holt, Véronique Barriel, & Pascal Tassy.
Comptes Rendus Biologies 2003, 326(7):687-697.
DOI: 10.1016/S1631-0691(03)00158-6

Abstract

Among the African elephants, it has been unanimously acknowledged that the forest elephants (cyclotis form) are peculiar, so that they have been elevated to the specific rank. The development of molecular analyses of extant Loxodonta has only focused on two forms yet: the savannah form (africana) and the forest form (cyclotis), disregarding the so-called pygmy elephants (pumilio or fransseni) the systematic status of which has been debated since their discovery. Therefore, we have sampled nine dwarfed-labelled specimens in collection and eight specimens of typical forest elephants that we compared to three savannah elephants and two Asian elephants. Because of the degraded nature of the nuclear DNA content in bone samples of old specimens, we assayed mitochondrial markers; 1961 bp of the mitochondrial genome were sequenced (over a continuous range spanning the cytochrome gene, tRNA Thr, tRNA Pro, hypervariable region 1 and central conserved region of the control region). Pumilio and cyclotis are not sister-taxa: the phylogenetic analyses rather account for the inclusion of the so-called pygmy elephants within a monophyletic group of forest elephants sensu lato. The internal structure of this clade reveals to depend on isolation and remoteness between populations, characteristics that may have been extensively influenced by climatic variations during the Quaternary period. We conclude that the specific taxon Loxodonta pumilio (or Loxodonta fransseni) should be abandoned.

Resume

Au sein des éléphants d’Afrique, la singularité des éléphants de forêt (forme cyclotis) est désormais unanimement reconnue, au point que certains en font une espèce à part entière. Le développement des analyses moléculaires sur les Loxodonta actuels n’a porté jusqu’à aujourd’hui que sur deux formes : la forme de savane (africana) et la forme de forêt (cyclotis), négligeant les éléphants dits nains (pumilio ou fransseni), dont le statut systématique est débattu depuis leur découverte. En conséquence, nous avons échantillonné neuf spécimens enregistrés comme nains en collection ainsi que huit spécimens d’éléphants de forêt typiques, que nous avons comparés à trois éléphants de savane et deux éléphants asiatiques. Les marqueurs utilisés sont mitochondriaux du fait de la dégradation de l’ADN nucléaire des échantillons osseux prélevés sur des spécimens anciens ; 1961 paires de bases du génome mitochondrial ont été séquencées (couvrant une zone continue allant du gène du cytochrome , à l’ARNt Thr, l’ARNt Pro, la région hypervariable 1 et la région centrale conservée de la région de contrôle). Pumilio et cyclotis ne sont pas des groupes frères : les analyses phylogénétiques démontrent que les éléphants dits nains sont en fait inclus dans un groupe monophylétique d’éléphants de forêt sensu lato. La structuration interne de ce clade apparaît comme étant largement fonction de l’isolement et de la distance entre les populations et a pu être influencée de façon extensive par les variations climatiques au cours de la période Quaternaire. Nous concluons que le taxon de rang spécifique Loxodonta pumilio (ou Loxodonta fransseni) devrait être abandonné.

Original material

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Further reading

This article has been cited 16 times since its original publication. Acces its citation report on Web of Science.
Its is notably cited on the wikipedia page of the forest African elephants.
Naturally, this article has caused some reactions in the realm of cryptozoology.