Summary Horse domestication revolutionized warfare and accelerated travel, trade, and the geographic expansion of languages. Here, we present the largest DNA time series for a non-human organism to date, including genome-scale data from 149 ancient animals and 129 ancient genomes (≥1-fold coverage), 87 of which are new. This extensive dataset allows us to assess the modern legacy of past equestrian civilizations. We find that two extinct horse lineages existed during early domestication, one at the far western (Iberia) and the other at the far eastern range (Siberia) of Eurasia. None of these contributed significantly to modern diversity. We show that the influence of Persian-related horse lineages increased following the Islamic conquests in Europe and Asia. Multiple alleles associated with elite-racing, including at the MSTN “speed gene,” only rose in popularity within the last millennium. Finally, the development of modern breeding impacted genetic diversity more dramatically than the previous millennia of human management.

No abstract

We have briefly reviewed types of genetic variation and selection in the wild as contrasted with selection in captive populations, along with the objectives of captive breeding programs, before recommending selection procedures for the genetic management of captive populations.Although some inadvertent selection for tameness and adaptation to captive environments is inevitable in captive populations, any selection that is actively applied to captive populations should have clearly defined objectives.Much of the apparent disagreement about genetic management of captive populations probably stems from the varying objectives of different captive breeding programs. Objectives differ depending on whether the populations are: (1) common species for display, (2) endangered species for long-term conservation, (3) rare species being multiplied for immediate release back into the wild, or (4) rare species not yet capable of self-sustaining reproduction in captivity.For all categories of populations we recommend selection to keep the genetic load under control.Populations in category 1 can be selected for adaptation to captive breeding, ease of handling, and for classic species phenotype.Populations in categories 2 and 3 should have no deliberate selection applied to them, apart from that to control the genetic load, so that the probability of successful release back into the wild is maximized.Populations in category 4 may require selection for captive breeding success until they attain self-sustaining status. Once this has been achieved they should be managed as under category 2 .The special cases of species that have been subjected to introgression are discussed. The multidisciplinary nature of captive population management is stressed.

Coadaptation can occur either because of local adaptation in a geographically widespread population and/or because of intrinsic adaptation to the state of other genes or choniosomes. In either event, hybridization between animals with differently coadapted gene or chromosomal complexes can result in a dccrease in fertility, viability, etc. in the initial hybrids and especially in later generations. This is known as an outbreeding depression. Moreover, releasing animals not adapted to the local environment can seriously hamper the effectiveness of a reintroduction program, and hybridization can also destroy the local adaptation. Coadapted gene complexes are best detected through studies on natural populations because the adaptive nature of the complex is often only apparent in the natural environment. In the absence of information on natural populations (but ideally as a supplement), the presence of coadapted gene complexes and population boundaries can be. detected through mating behavior, a pedigree analysis that can detect outbreeding depressions and distinguish them from inbreeding depressions, or genetic and karyotypic surveys. Once an outbreeding depression has bccn detected, it can be used to redefine the boundaries of the populations to be managed. Basically, the outbreeding depression is avoided by prevcnting hybridization between animals with the different coadapted complexes. In some cases, formal subspecific designations have been used to define the population boundaries. Unfortunately, many subspecific designations were made before populationthinking influenced taxonomy. It is important to emphasize the need to undertake modern biological studies and to collect additional information useful for systematics. If modern biological studies indicate that the subspecies have little or no biological significance, it is best to treat the animals as a single population and disregard the subspecific designations. Key words: outbreeding depression, population boundariesReceived for publication September 17, 1985; accepted October 22, 1985. Address reprint requests to Alan R. Templeton, Department of Biology, Washington University, INTRODUCTION The Definition of CoadaptationThe word "coadaptation" was used first by Dobzhanslq [1948] to describe the phenomenon that sets of genes derived from different geographical populations of the fruit fly species Drosophilu pseudoobscuru resulted in reduced fitness when brought together by hybridization, particularly in the generations following the initial hybrids. Subsequent work [Brncic, 1954;Templeton et al, 1976; Wallace et al, 19531 revealed that coadapted gene complexes can be found within a large number of Drosophilu species, although some Drosophilu species show no evidence for coadaptation despite being widespread geographically [McFarquhar and Robertson, 1963 ; Richardson and Kojima, 1965, Singh, 19721.The Drosophilu studies indicate that coadapted ene complexes are a common but not universal phenomenon. This inference should be applicable to the vast majori...

No abstract