An osteological documentation of hybrid wildebeest and its bearing on black wildebeest (Connochaetes Gnou) evolution

ABSTRACT Wildebeest are part of the sub family Alcelaphinae and the genus Connochaetes. There are two extant species of wildebeest namely Connochaetes gnou (black wildebeest) and Connochaetes taurinus (blue wildebeest). From fossil evidence, it is thought that co-generic blue and black wildebeest diverged ca. 1Ma. Historically, geographic ranges of these two species have overlapped, but different social behaviour and habitat preference prevented sexual interaction. It has been proposed that reproductive isolation between C. taurinus and C. gnou may have disappeared due to artificial management. This has caused mate choice to change in the absence of species-specific mates, resulting in hybridisation. Most documented cases of hybridisation have occurred from dispersing blue wildebeest bulls introgressing into black herds however, the opposite has been observed. Genetic studies on a population where the blue males have introgressed with black females, show that the blue wildebeest populations are “pure” and that the black wildebeest populations are receiving an influx of blue alleles. In this research, 14 skeletons of modern hybrid Connochaetes taurinus and Connochaetes gnou, from more than one post-hybridisation generation from the Spioenkop reserve, were morphologically as well as metrically compared with a sample of ten modern “pure” blue and 15 black wildebeest. This project showed that univariate, bivariate statistical analyses of selected measurements of the skeletons were successful in identifying all of the Spioenkop individuals as hybrids. Morphologically, the hybrids exhibit a general increase in body size, and have unusual horns. The auditory bullae of the Spioenkop specimens are highly deformed, as are some axes. There is unusual bone growth on most of the post crania, morphological differences are observed on the distal ends of the metapodials, and the radius and ulna are fused in many specimens

Size variation and body proportions in an isolated Holocene-aged population of Hominids from Palau, Micronesia and its impact on our understanding of variation in extinct Hominids.

This thesis investigated whether a fragmented assemblage of fossilized Homo sapiens remains collected from Palau; Micronesia represents a population exhibiting a case of insular dwarfing. The earliest occupation of Palau is ca. 4000 YBP, and the fossil assemblage studied here dates between 2900 – 1400 YBP, thus providing a relatively short time in which body size reduction, due to insular dwarfism could occur. There are well known cases, in both the modern and fossil context, where insular dwarfism and body size reduction is known to occur in human populations that are isolated, but the results of this reduction are seen over a much longer period (e.g., tens of thousands of years). Metric dimensions of the humerus, radius, ulna, femur, tibia, and fibula and os coxa are quantified in order to evaluate other potential insular dwarfs in fossil hominin assemblages, such as Homo floresiensis. Previous studies have shown that the Palau archipelago has remained relatively isolated from human contact due to the surrounding currents, providing ideal conditions for insular dwarfism to occur. Comparing measurements taken on populations encompassing a reasonable range of human variation, this study quantified and compared the Palauan measurements and joint ratios to determine which variables might differentiate among these population groups, thus indicating traits potentially uniquely signalling a reduction in human body size. Disproportionate joint sizes were observed in the humerus, ulna, tibia, and femur of the Palauan sample. While individual measurements from the Palau sample all fall comfortably within the range of measurements taken from other small-bodied human individuals, the articular surfaces of Palauan specimens do not resemble those from other well-established, small-bodied insular populations. As the articular surfaces are smaller relative to the epiphyseal diameters and may be a reflection of the relatively short time in which the reduction has taken place. Morphologically the Palauan population exhibits small orbits, a large interorbital distance, an inflated glabella region and protruding supraorbital tori. A reduction in the mandible may account for the overcrowding of teeth observed in the dentition. The Palauan individuals have disproportionately large maxillary teeth. The mandibular dentition, however, varies: the incisors, canine and first molars are large, while reduction is seen most easily in the premolars and the second molar. This dental reduction is coupled with significant differences between the cervico-enamel junctions for these teeth and the corresponding crown measurements. Large teeth, inflated glabella, and protruding supraorbital tori may be an indication of a founding population. These traits are all found in Australomelanesian populations, and it is thus possible that the Palauan population under study originated from Melanesia (e.g. New Guinea or South East Asia). Application of the present study to Homo floresiensis, a fossil hominin suggested by some authors to have undergone insular dwarfing, reveals that while H. floresiensis is small for some measurements, most fall within the range of the small-bodied comparative sample from Palau. The stature of H. floresiensis is not unusually small and falls within the ranges of the comparative sample used here. The only comparison that can be made for joint size is that both the Palauan and H. floresiensis femoral heads are small and both exhibit the same disproportionate dimensions of the proximal tibia. As potential body size reduction is possibly responsible for the Palauan traits, the similarity in joint proportions may be attributed to insular dwarfing when the population first became isolated, as these joint irregularities are not seen in established insular dwarfs (Andaman and Nicobarese). The differences present in the measurements obtained for all the small-bodied samples examined suggests that even though insular populations may present as small-bodied, the island populations (fossil or extant) should be viewed as a case by case study. Isolation, life history, founding population (genetics) and environmental conditions all affect population body size over time, but to assume that all isolated populations will decrease body size in the same way is incorrect. What is seen in Palauan specimens is likely the adaptive responses of a isolated population from Melanesia, resulting in the insular dwarfism observed. By examining the available aspects of this insular population and found that it was consistent in reflecting size and proportions of small-bodied populations

Hybrid wildebeest (Artiodactyla:Bovidae) provide further evidence for shared signatures of admixture in mammalian crania

The genus Connochaetes, Lichtenstein, 1814, contains two extant species, the blue wildebeest (C. taurinus, Burchell, 1823) and the black wildebeest (C. gnou, Zimmermann, 1780). In recent years, forced sympatry in confined areas within South Africa has led to interbreeding between these taxa and to fertile hybrid offspring. Here we report on a series of cranial characteristics of a hybrid wildebeest population culled at Spioenkop Dam Nature Reserve, KwaZulu-Natal, South Africa. Dental, sutural and horn morphological anomalies occur at high frequency within these animals. Similar cranial morphological anomalies have been shown in other mammalian hybrids and this study provides further evidence that such anomalies may characterise hybridisation more broadly across phylogenetically divergent mammalian groups, although the anomalies appear to differ in their expression across taxa. An increased ability to identify hybrids may also have important applications in the conservation of the endemic black wildebeest

Hybrid wildebeest (Artiodactyla:Bovidae) provide further evidence for shared signatures of admixture in mammalian crania

The genus Connochaetes, Lichtenstein, 1814, contains two extant species, the blue wildebeest (C. taurinus, Burchell, 1823) and the black wildebeest (C. gnou, Zimmermann, 1780). In recent years, forced sympatry in confined areas within South Africa has led to interbreeding between these taxa and to fertile hybrid offspring. Here we report on a series of cranial characteristics of a hybrid wildebeest population culled at Spioenkop Dam Nature Reserve, KwaZulu-Natal, South Africa. Dental, sutural and horn morphological anomalies occur at high frequency within these animals. Similar cranial morphological anomalies have been shown in other mammalian hybrids and this study provides further evidence that such anomalies may characterise hybridisation more broadly across phylogenetically divergent mammalian groups, although the anomalies appear to differ in their expression across taxa. An increased ability to identify hybrids may also have important applications in the conservation of the endemic black wildebeest

Small-Bodied Humans from Palau, Micronesia

UNLABELLED: Newly discovered fossil assemblages of small bodied Homo sapiens from Palau, Micronesia possess characters thought to be taxonomically primitive for the genus Homo. BACKGROUND: Recent surface collection and test excavation in limestone caves in the rock islands of Palau, Micronesia, has produced a sizeable sample of human skeletal remains dating roughly between 940-2890 cal ybp. PRINCIPLE FINDINGS: Preliminary analysis indicates that this material is important for two reasons. First, individuals from the older time horizons are small in body size even relative to "pygmoid" populations from Southeast Asia and Indonesia, and thus may represent a marked case of human insular dwarfism. Second, while possessing a number of derived features that align them with Homo sapiens, the human remains from Palau also exhibit several skeletal traits that are considered to be primitive for the genus Homo. SIGNIFICANCE: These features may be previously unrecognized developmental correlates of small body size and, if so, they may have important implications for interpreting the taxonomic affinities of fossil specimens of Homo

Hybrid wildebeest (Artiodactyla: Bovidae) provide further evidence for shared signatures of admixture in mammalian crania

The genus Connochaetes, Lichtenstein, 1814, contains two extant species, the blue wildebeest (C. taurinus, Burchell, 1823) and the black wildebeest (C. gnou, Zimmermann, 1780). In recent years, forced sympatry in confined areas within South Africa has led to interbreeding between these taxa and to fertile hybrid offspring. Here we report on a series of cranial characteristics of a hybrid wildebeest population culled at Spioenkop Dam Nature Reserve, KwaZulu-Natal, South Africa. Dental, sutural and horn morphological anomalies occur at high frequency within these animals. Similar cranial morphological anomalies have been shown in other mammalian hybrids and this study provides further evidence that such anomalies may characterise hybridisation more broadly across phylogenetically divergent mammalian groups, although the anomalies appear to differ in their expression across taxa. An increased ability to identify hybrids may also have important applications in the conservation of the endemic black wildebeest

Hybrid wildebeest (Artiodactyla: Bovidae) provide further evidence for shared signatures of admixture in mammalian crania

The genus Connochaetes, Lichtenstein, 1814, contains two extant species, the blue wildebeest (C. taurinus, Burchell, 1823) and the black wildebeest (C. gnou, Zimmermann, 1780). In recent years, forced sympatry in confined areas within South Africa has led to interbreeding between these taxa and to fertile hybrid offspring. Here we report on a series of cranial characteristics of a hybrid wildebeest population culled at Spioenkop Dam Nature Reserve, KwaZulu-Natal, South Africa. Dental, sutural and horn morphological anomalies occur at high frequency within these animals. Similar cranial morphological anomalies have been shown in other mammalian hybrids and this study provides further evidence that such anomalies may characterise hybridisation more broadly across phylogenetically divergent mammalian groups, although the anomalies appear to differ in their expression across taxa. An increased ability to identify hybrids may also have important applications in the conservation of the endemic black wildebeest