Do Hybrid Animals Live in Their Parents Natural Habitats?

Many subspecific forms are known that are sympatric over extensive parts of their range. These hybridize more freely than would generally allow them to be classified as species, and yet typically show assortative mating similar to although less strong than that in ‘true’ species. On the other side of the species boundary, hybrids between many pairs of animal species (as well as plant species) are also known. These hybrids are often (though by no means always) fertile enough to backcross to the parents.

Adaptation to the arid environment is associated with a chromosomal inversion, 2La, which is ancestral to the arid-adapted species A. arabeinsis [89]. Critically, genetic analyses have revealed that introgression from A. arabeinsis into A. gambiae resulted in the transfer of the 2La inversion [63,65,66]. Thus, transfer of a key genomic region via introgression appears to have enabled A. gambiae to expand beyond its ancestral range by conferring adaptive traits in the novel habitat. An alternative route by which hybridization enables range expansion is by increasing genetic variance that potent

In cetacean species, hybridization has been documented both in captive breeding sites and in the wild [115,116], with around 20% of species known to hybridize [117]. Cross-breeding was shown to be more common between species that have similar morphological and behavioral traits [117,118,119], ...

Sampling of hybrid zones can be in linear transects or over large areas (e.g., [94]). However, linear transects can make clines look broader or sharper depending on the whether the transect is orthogonal to the hybrid zone [18]. Restricted geographic sampling of a hybrid zone can obscure patterns of variation, particularly in mosaic hybrid zones where overlap can be extensive and occupied habitat patches can appear and disappear with shifting species distributions. If sampled only at a fine scale, the area of contact or shifts in ranges can be missed (Figure I).

This initially took place in the context of two evolutionary hypotheses: stasipatric speciation, in which a new chromosomal rearrangement spreads at the expense of parental forms (Key, 1968; White, 1968, 1978), and phase III of Wright's shifting balance model, in which a new adaptive peak spreads to other populations (Wright, 1977, 1982; Barton, 1992; Kondrashov, 1992). The widespread occurrence of natural hybrid zones, the taxonomic questions they pose and the opportunities they present for investigating processes of species isolation make them a research field in their own right (Barton and Hewitt, 1985).

Despite the active role of ecological barriers found to limit hybridization in some Mediterranean regions18,19, variable degrees of admixture have been detected throughout the European continent and across habitat types as a consequence of human pressures2,20,21,22,23,24,25,26, leading to a complete hybrid swarm in wild-living cats in Scotland12.

To compare, only 16.1 percent of 137 Cuban crocs raised in captivity showed genetic indications of hybridization in his study. Miles O'Brien pets a wild Cuban crocodile captured in the Zapata swamp.

Among ducks, mallards widely hybridize with many other species, and the genetic relationships between ducks are further complicated by the widespread gene flow between wild and domestic mallards. One of the most common interspecific hybrids in geese occurs between Greylag and Canada geese (Anser anser x Branta canadensis). One potential mechanism for the occurrence of hybrids in these geese is interspecific nest parasitism, where an egg is laid in the nest of another species to be raised by non-biological parents.

Common chimpanzees had been known to hybridize with bonobos in captivity and rarely in the wild.