This study analyses the carnivore component of African fossil faunas from three time slices: 7–5 Ma, 4–3 Ma, and 2.5–1.2 Ma, using cluster analysis and principal coordinate analysis (PCO) of presence/absence data on genera. The faunas mostly cluster by time slice, with the exception of Laetoli (Tanzania) and Ahl al Oughlam (Morocco), which differ from all other faunas. The separation during the Late Miocene of a Chado–Libyan bioprovince from the remainder of Africa is supported. No such distinctions are present in the other time slices. Taxonomic distance is not generally correlated with geographic distance, though if Langebaanweg is removed from the 7–5 Ma time slice, the correlation at that time is significant. Comparison of these paleontological results with phylogeographic studies of modern species leads to some general comments on the analytic power of the fossil record with regard to interregional migrations.
Cette étude analyse la composante carnivore des faunes fossiles africaines de trois périodes, 7–5 Ma, 4–3 Ma et 2,5–1,2 Ma, en utilisant l’analyse cluster et l’analyse en coordonnées principales des données d’absence/présence des genres. Les faunes se regroupent essentiellement par période temporelle, à l’exception de Laetoli (Tanzanie) et Ahl al Oughlam (Maroc) qui diffèrent de toutes les autres faunes. La séparation, au cours du Miocène supérieur, d’une bioprovince Tchadolibyenne du reste de l’Afrique est corroborée. De telles distinctions n’apparaissent pas au cours des autres périodes. La distance taxonomique n’est généralement pas corrélée à la distance géographique bien que, si l’on retire Langebaanweg de la période 7–5 Ma, cette corrélation soit alors significative. La comparaison de ces résultats paléontologiques avec les études phylogéographiques d’espèces modernes conduit à des commentaires généraux sur le pouvoir analytique de l’enregistrement fossile en ce qui concerne les migrations inter-régionales.
Modern-day Africa is divided into a large number of ecoregions as well as smaller units
A notable exception is Reed and Lockwood
This study is based on the carnivoran constituent of the mammal faunas of Africa between 7 and 1.2 Ma (henceforth just called “faunas”). It focuses on three time slices: 7–5 Ma, 4–3 Ma, and 2.5–1.4 Ma. These time slices are of special significance. The first, 7–5 Ma, encompasses the time of origin of the first bipedal hominids, and therefore, so current thinking goes, the first members of our lineage, the hominins. The second time slice, 4–3 Ma, is the time of greatest species richness among African carnivorans
Two main statistical methods are used. One is paired-group (UPGMA) clustering
As a complement to the cluster analysis, principal coordinate analysis (PCO) was used
Statistical analyses were carried out using PAST, version 1.82
The faunas used in this paper are listed in
The first analysis is a cluster analysis of all localities from all time slices. The results are shown in
The subsequent split is between East African faunas of the 4–3 Ma and 2.5–1.2 Ma time slices, except that the younger Shungura D–F clusters with the 4–3 Ma time slice and the older Shungura B and Usno with the 2.5–1.2 Ma time slice. The latter time slice is further split into a cluster uniting the two Olduvai members with two Koobi Fora members and Shungura G, while the other cluster unites the Okote Mb. of Koobi Fora with the Omo faunas Shungura B and Usno. In the 4–3 Ma cluster, South Turkwell is united with Shungura D–F and these are well separated from the other faunas of the time slice, which are very similar to each other.
The first two coordinates of the PCO of all faunas together are plotted in
The results of the PCO with its MST are shown in
The result of the PCO analysis of the 4–3 Ma time slice faunas is shown in
The MST is shown on a map of Africa in
The PCO analysis and MST shown in
With only a few exceptions, the analyses of all faunas together align well with expectations (
That Shungura B and Usno group with the 2.5–1.2 Ma faunas while Shungura D–F groups with the 4–3 Ma faunas is almost certainly due to the presence at the former two localities of
The faunas placed in an intermediate position in
In the PCO analysis of the 7–5 Ma time slice, Langebaanweg falls almost at the center of the diagram (
The results of the PCO analysis of the 4–3 Ma time slice (
The faunal positions in the PCO of the 2.5–1.2 Ma time slice are relatively closely correlated with geographic distance, though not significantly so (
It is difficult to find comparisons with this study. Very few studies have compared the carnivoran faunas of South and East Africa
No previous studies have made comparisons between the carnivorans of North and East Africa, except on a locality-specific basis. However, this study agrees with studies on other groups, such as anthracotheres and hippos
At shorter time scales the situation is different. A number of phylogeographic studies of medium-sized and large African mammals have been carried out in the past decade, including giraffe,
These phylogeographic results, which broadly speaking address processes occurring over the past 0.5–1 Ma, have generally been interpreted in terms of Pleistocene climatic fluctuations and concomitant changes to the environment such as expanding or contracting forest regions, grasslands, and deserts, suggest several things. The first is that in larger carnivorans gene flow between populations may be rapid enough to disrupt genetic isolating processes occurring over time frames of 105 years or less, although more species need to be studied to determine whether this is a general pattern or specific to wild dog and lion, two of the most mobile of extant carnivorans. Studies of medium-sized taxa such as jackals,
Although the analysis above dealt with the movement of species within genera and the phylogeographic studies with the movement of subspecific units, useful insights can be gained from applying the information from the latter to the former. It must just be kept in mind that the time scale for the phylogeographies is on the order of 105 years while that of the paleontological data is on the order of 106 years. Combining the results suggests the following: similarities between East and South African faunas among the larger carnivorans at the generic or specific level are at present irrelevant to considerations of possible migration barriers between African subregions because any differences between regions in this faunal component is quickly erased by their dispersal abilities at time scales below current detection levels in the fossil record; cases where there are differences between these faunal components are of particular interest but must be studied on a case by case basis before they can be used to infer a general pattern; where there are such differences among larger carnivorans on a large scale (e.g., between the Chado–Libyan bioprovince and other African faunas as discussed above) this is evidence of barriers to dispersal and gene flow that persisted over time scales of 106 years and probably considerably more; similarities or differences between South and East African faunas among the smaller carnivorans are strong indications of disruption of gene flow (with attendant possibilities of local speciation and/or extinction) between regions at time scales of 105 years or less.
Such patterns have the potential of being observable in the fossil record. In fact, smaller carnivorans may be among the most informative of mammals in this regard, as they often have large species and genus ranges despite relatively limited dispersal abilities and many of them occupy a wide range of habitats. Indeed, some species, e.g., bat-eared fox,
It is of considerable interest that many of the large herbivores studied by phylogeographic means seem to generate phylogeographic signals on time scales similar to those of small carnivores. This surely reflects a fundamental difference between herbivores and large carnivores. The former are foodstuff specialists, but once the preferred food is present they have the ready means of consuming it. The latter are not specialists on the particular foodstuff (meat is, after all, meat), but on the particular vehicle (animal) that the foodstuff comes in. Thus, unlike herbivores, it is obtaining the food that is the problem for a large carnivore, not the presence of the foodstuff
Hominins take something of an intermediate position in this respect. Given their broad dietary tolerances, at least after the appearance of the genus
I would like to thank Dr. L. de Bonis and the RHOI program for the invitation to the workshop where these results were first presented, M.E. Lewis and S. Peigné for successful collaboration on African carnivorans and K.E. Reed and the School of Human Evolution and Social Change, Arizona State University for working facilities. My research is funded by the Swedish Research Council (VR). Satellite images copyright NASA.
Phenogram showing the results of the cluster analysis using the Raup–Crick method on faunas of all time slices. Bifurcations denoted by asterisks are not significant (nor are, of course, bifurcations above these).
Fig. 1. Phénogramme montrant les résultats de l’analyse cluster utilisant la méthode Raup-Crick sur les faunes de l’ensemble des périodes de temps. Les bifurcations indiquées par des astérisques ne sont pas significatives (comme ne le sont pas, bien sûr, les bifurcations situées au-dessus).
Diagram showing the first two coordinate axes of the PCO of faunas of all time slices. Coordinate 1 has the eigenvalue 34.71 (18.80% variation explained), coordinate 2 the eigenvalue 25.11 (13.60% variation explained). Laetoli and Ahl al Oughlam are very different from the other faunas, probably as a result of their many unique taxa. The faunas of the different time slices are shown with their convex bounding boxes: dashed line: 7–5 Ma; dotted line: 4–3 Ma; solid line: 2.5–1.2 Ma. Apart from the position of Usno (and the cases of Laetoli and Ahl al Oughlam) there is no overlap between time slices. In each case, the South African locality (specified by name in the diagram) is the most distant, creating a peak in the bounding box.
Fig. 2. Diagramme montrant les deux premiers axes de coordonnées de l’analyse en coordonnées principales des faunes de toutes les périodes de temps. La coordonnée 1 a une valeur propre de 34,71 (18,80 % de la variation totale exprimée) et la coordonnée 2 une valeur propre de 25,11 (13,60 % de la variation totale exprimée). Laetoli et Ahl al Oughlam sont très différentes des autres faunes, ce qui est probablement dû à leurs nombreux taxons propres. Les faunes des différentes périodes de temps sont montrées dans des boîtes englobantes convexes : ligne tiretée : 7–5 Ma ; ligne pointillée : 4–3 Ma ; ligne continue : 2,5–1,2 Ma. En dehors de la position d’Usno (et des cas de Laetoli et Ahl al Oughlam), il n’y a aucun recouvrement entre les périodes temporelles. Dans chacune, la localité sud-africaine (indiquée nominalement sur le diagramme) est la plus distante, créant un pic dans la boîte englobante.
A. Diagram showing the first two coordinate axes of the PCO of the 7–5 Ma time slice faunas. Coordinate 1 has the eigenvalue 0.790 (61.26% variation explained), coordinate 2 the eigenvalue 0.212 (16.41% variation explained). B. Diagram showing the first two coordinate axes of the PCO of the 7–5 Ma time slice faunas with Langebaanweg removed. Coordinate 1 has the eigenvalue 0.790 (62.53% variation explained), coordinate 2 the eigenvalue 0.212 (16.77% variation explained).
Fig. 3. A. Diagramme montrant les deux premiers axes de coordonnées de l’analyse en coordonnées principales des faunes de la période 7–5 Ma. La coordonnée 1 a une valeur propre de 0,790 (61,26 % de la variation exprimée), la coordonnée 2 une valeur propre de 0,212 (16,41 % de la variation exprimée). B. Diagramme montrant les deux premiers axes de coordonnées de l’analyse en coordonnées principales des faunes de la période 7–5 Ma, sans Langebaanweg. La coordonée 1 a une valeur propre de 0,790 (62,53 % de la variation exprimée), la coordonnée 2 une valeur propre de 0,212 (16,77 % de la variation exprimée).
The minimum spanning tree from
Fig. 4. Arbre maximal minimal tiré de la
Diagram showing the first two coordinate axes of the PCO of the 4–3 Ma time slice faunas. Coordinate 1 has the eigenvalue 0.680 (36.30% variation explained), coordinate 2 the eigenvalue 0.410 (21.87% variation explained).
Fig. 5. Diagramme montrant les deux premiers axes de coordonnées de l’analyse en coordonnées principales des faunes de la période 4–3 Ma. La coordonnée 1 a une valeur propre de 0,680 (36,30 % de la variation exprimée), la coordonnée 2 une valeur propre de 0,410 (21,87 % de la variation exprimée).
The minimum spanning tree from
Fig. 6. Arbre maximal minimal tiré de la
Diagram showing the first two coordinate axes of the PCO of the 2.5–1.2 Ma time slice faunas. Coordinate 1 has the eigenvalue 0.500 (42.71% variation explained), coordinate 2 the eigenvalue 0.288 (24.59% variation explained).
Fig. 7. Diagramme montrant les deux premiers axes de coordonnées de l’analyse en coordonnées principales des faunes de la période 2,5–1,2 Ma. La coordonnée 1 a une valeur propre de 0,500 (42,71 % de la variation exprimée), la coordonnée 2 une valeur propre de 0,288 (24,59 % de la variation exprimée).
The minimum spanning tree from
Fig. 8. Arbre maximal minimal tiré de la
The faunas included in the present study along with the number of genera of carnivoran present and the source of the taxonomic information used. For the number and percentage of unique taxa, the first number is in relation to other faunas of that time slice while the values in parentheses are in relation to all faunas of all time slices.
Tableau 1 Faunes incluses dans cette étude, avec le nombre de genres de carnivores présents et la source de l’information taxonomique utilisée. Pour le nombre et le pourcentage des taxons propres à une faune, le premier chiffre est relatif aux autres faunes de la période de temps concernée, tandis que les chiffres entre parenthèses sont relatifs à l’ensemble des faunes toutes périodes temporelles confondues.