Beobachtungen zur Hybridisierung zwischen Ctenosaura similis (Gray, 1831) und Ctenosaura bakeri Stejneger 1901 auf Utila, Honduras.
Elaphe N.F. 15: 55-59.
Die honduranische Karibikinsel Utila ist der einzige bekannte Ort der Welt, an dem drei Großleguanarten vorkommen. Währenddem Iguana iguana rhinolopha primär die Feuchtwälder bewohnt und Ctenosaura bakeri exklusiv die schattigen Mangrovensümpfe besiedelt, bevorzugt Ctenosaura similis semiaride bis aride Lebensdräume mit starker Sonneneinstrahlung. Trotz dieser ökologischen Trennung wurde bereits in der Vergangenheit von fertilen Hybriden zwischen C. similis und C. bakeri berichtet. Neben der Beschreibung eines möglichen Hybridgürtels mit beonbachteten potenziellen Bastarden, wird die ökologische Anpassungs- und Ausbreitungsfähigkeit von C. similis aufgezeigt.
Impact of genomic leakage on the conservation of the endangered Milky Stork.
Biological Conservation 229(e1400253). DOI:10.1016/j.biocon.2018.11.009
Siehe auch Zeitungsartikel: https://www.eurekalert.org/news-releases/623399
Endangerment and extinction of threatened populations can often be accelerated by genomic contamination through infiltration with alien alleles. With a growing anthropogenic footprint, many such hybridization events are human-mediated. The Milky Stork (Mycteria cinerea) is one such species whose genomic composition is threatened by human-mediated hybridization with its sister taxon, the Painted Stork (Mycteria leucocephala). A comprehensive investigation of the stork population in Singapore using three complementary population-genomic approaches revealed a large proportion of hybrids that have undergone several generations of genomic leakage from Painted Storks and fall along a genetic cline that closely mirrors a phenotypic cline from pure Milky to pure Painted. Although originating from a limited number of introduced Painted Storks, these hybrids are now an integral part of both the wild and captive Singaporean and southern peninsular Malaysian stork population. Genetically informed conservation management including the isolation of hybrids in captivity and a strict removal of hybrids from the wild along with a release of genetically pure Milky Storks is imperative for continued survival. Similar approaches must become routine in endangered species conservation as human-mediated hybridization increases in volume.
Preliminary notes on the F1 bongo antelope x sitatunga hybrids Taurotragus eurycerus x Tragelaphus spekei at Antwerp Zoo.
Int. Zoo Yb. 8: 137-139.
In June 1960 Antwerp Zoo rceived a male Bongo antelope. "Nabeli", from Epulu in the Congo. The only other Bongo antelope in captivity at that time was a female, "Karen", at Cleveland Zoo ... It was then decided to try and cross the male Bongo antelope with a female sitatunga. The nearly 3 year old male Bongo was put with a group of some 12 female sitatungs for about 6 months. As soon as the male showed sexual interest in the females, the Bongo and 2 sitatungas were separated from the main herd ... Births occured on 4 September 1964 giving a gestation period of 309 days. ... the second young was born on 4 February 1965 by caesarian section ...
Third case of a Bongo x Sitatunga hybrid.
GNUSLETTER 33 (1):12
The only so far reported case of hybridization between Tragelaphus eurycerus and Tragelaphus spekii resulted in two fertile females at Antwerp Zoo. The two Bongo x Sitatunga hybrids born at Antwerp were both females. One of these ‘Bongsi’ produced an healthy foal when mated with a sitatunga male. The coexistence of several different species in a large enclosure at the Fasano Safari Park (Brindisi, southern Italy) resulted in the unexpected birth of a female Bongo x Sitatunga F1 in 2012.As in Antwerp, even the Fasano Bongsi has horns. While in general appearance it resemble more the paternal species, its locomotion and shyness resemble those typical of sitatunga.I was not able to know the exact birth date of the bongsi. It is healthy at the date of writing and horns are longer (December 2015). As no sitatunga or bongo individuals are actually present in the Safari park, no breeding from this bongsi is expected.
Speciation with gene flow in equids despite extensive chromosomal plasticity.
Proc. Natl. Acad. Sci. U S A. 2014 Dec 30; 111(52): 18655–18660.
Published online 2014 Dec 1. doi: 10.1073/pnas.1412627111
Horses, asses, and zebras belong to a single genus, Equus, which emerged 4.0–4.5 Mya. Although the equine fossil record represents a textbook example of evolution, the succession of events that gave rise to the diversity of species existing today remains unclear. Here we present six genomes from each living species of asses and zebras. This completes the set of genomes available for all extant species in the genus, which was hitherto represented only by the horse and the domestic donkey. In addition, we used a museum specimen to characterize the genome of the quagga zebra, which was driven to extinction in the early 1900s. We scan the genomes for lineage-specific adaptations and identify 48 genes that have evolved under positive selection and are involved in olfaction, immune response, development, locomotion, and behavior. Our extensive genome dataset reveals a highly dynamic demographic history with synchronous expansions and collapses on different continents during the last 400 ky after major climatic events. We show that the earliest speciation occurred with gene flow in Northern America, and that the ancestor of present-day asses and zebras dispersed into the Old World 2.1–3.4 Mya. Strikingly, we also find evidence for gene flow involving three contemporary equine species despite chromosomal numbers varying from 16 pairs to 31 pairs. These findings challenge the claim that the accumulation of chromosomal rearrangements drive complete reproductive isolation, and promote equids as a fundamental model for understanding the interplay between chromosomal structure, gene flow, and, ultimately, speciation.
Is the endangered Grevy’s zebra threatened by hybridization?
Anim Conserv. 2009;12:505–513.
Hybridization between an abundant species and an endangered species is cause for concern. When such hybridization is observed, it is both urgent and necessary to assess the level of threat posed to the endangered species. We report the first evidence of natural hybridization between two equids: the endangered Grevy's zebra Equus grevyi and the abundant plains zebra Equus burchelli. Grevy's zebra now number <3000 individuals globally, and occur only in northern Kenya and Ethiopia. In recent years, Grevy's zebra have become increasingly concentrated in the south of their range due to habitat loss in the north. Both species are sympatric in the Laikipia ecosystem of northern Kenya, where we have observed purportedly hybrid individuals. Using mitochondrial and Y chromosome DNA, we confirmed the hybrid status of the morphologically identified hybrids and demonstrate conclusively that all first‐generation hybrids are the offspring of plains zebra females and Grevy's zebra males. Behaviorally, hybrids integrate themselves into plains zebra society, rather than adopting the social organization of Grevy's zebra. Two hybrids have successfully raised foals to over 3 months in age, including one which has reached adulthood, indicating the fertility of female hybrids and viability of their offspring. We hypothesize that hybridization occurs due to (1) skewed sex ratios, in favor of males, within Grevy's zebra and (2) the numerical dominance of plains zebra in the region where hybridization is occurring. Stakeholders have discussed hybridization as a potential threat to Grevy's zebra survival. We argue, however, based on behavioral observations, that hybridization is unlikely to dilute the Grevy's zebra gene pool in the short term. As a conservation concern, hybridization is secondary to more direct causes of Grevy's zebra declines.
Pooling strategy and chromosome painting characterize a living zebroid for the first time.
PLoS ONE 12(7): e0180158. https://doi.org/10.1371/journal.pone.0180158
We have investigated the complex karyotype of a living zebra-donkey hybrid for the first time using chromosome-specific painting probes produced from flow-sorted chromosomes from a zebra (Equus burchelli) and horse (Equus caballus). As the chromosomes proved difficult to distinguish from one another, a successful new strategy was devised to resolve the difficulty and characterize each chromosome. This was based on selecting five panels of whole chromosome painting probes that could differentiate zebra and donkey chromosomes by labelling the probes with either FITC or Cy3 fluorochromes. Each panel was hybridized sequentially to the same G-Q-banded metaphases and the results combined so that every zebra and donkey chromosome in each suitable metaphase could be identified. A diploid number of 2n = 53, XY was found, containing haploid sets of 22 chromosomes from the zebra and 31 chromosomes from the donkey, without evidence of chromosome rearrangement. This new strategy, developed for the first time, may have several applications in the resolution of other complex hybrid karyotypes and chromosomal aberrations.
Captive breeding of squirrel monkeys, Saimiri sciureus and Saimiri boliviensis: The problem of hybrid groups.
Zoo Biology 17 (2): 95-109
The electrophoretic variability of blood proteins coding for up to 32 genetic loci was analyzed in 108 squirrel monkeys (Saimiri sciureus, Saimiri boliviensis, hybrids) from two captive colonies. Twelve polymorphic loci with 31 alleles are reported. The biallelic Ada* locus, G‐statistics and Hardy‐Weinberg genotype equilibria are useful for recognizing hybrids between S. sciureus and S. boliviensis. Backcrosses in hybrid stocks and gene flow in a natural hybrid belt, however, complicate the taxonomic diagnosis of captive specimens: S. sciureus phenotypes imported from Peru possessed the allele Ada*132, which generally characterizes S. boliviensis (or species hybrids). The complex taxonomy of Saimiri spp. Requires careful planning of captive breeding. We suggest a genetic analysis of the founder individuals before their inclusion in the European studbook population and to breed S. sciureus from Guyana separately from Peruvian imports, because the latter bear a greater risk of being taxonomically heterogeneous.