Furthermore, the early ancestors of Cannabis and Humidas may have been interfertile
for a very long time, probably since before the oldest known macrofossils were found near the K-T boundary in North America (see Johnson, 2002; Plate 6:1 for aff.
Loasoideae): Are interfertile
species and inbred populations results of a recent radiation?
The mating group C was genetically interfertile
strains from rice (Hseieh et al.
These two taxa are also interfertile
and hybrids have been observed in nature (R.
However, if you trace them around the North Pole, at about the same latitude, you find that there is a series of interfertile
sub-species that link the two, each similar in appearance to those either side of it.
Hybridity was central to both monogenist and polygenist theories as a criterion defining the boundaries between species of animals and possibly also between races of people: members of the same species were interfertile
while those of different species usually were not.
The two diploid subspecies are fully interfertile
and an impressive set of genomics tools, including linkage maps, QTL data sets, ESTs, BAC libraries, and arrays is available for analysis of the H genome, which is homeologous with the A, B, and D genomes of hexaploid wheat (Hayes et al.
Lee Silver resolves the problem by suggesting that there would be intervention in the molecules bonding sperm and ova in such a way that all children who had benefited from such genetic enhancement would not be interfertile
with those who had not benefited from it.
Reproductive isolation and speciation apparently occurred before gametic incompatibility closed off the possibility of gene flow, and as in two sympatic species of asteroids in the genus Patiriella that do not have gamete incompatibility (Byrne and Anderson, 1994), other mechanisms need to be found to explain how species integrity is maintained in these closely related, interfertile
forgetiana are interfertile
species that grow sympatrically and parapatrically throughout southern Brazil, but they form no hybrids in the wild.
silvestris, two well-recognized species of the Hawaiian group, are interfertile
in the lab but are strongly isolated in mate-choice experiments (Kaneshiro 1976; Carson 1978).
Other models of hybrid zone maintenance include a greater role of ecological factors, with hybrids occurring in intermediate habitats along an environmental gradient (Endler 1977), or where a patchy distribution of habitats brings interfertile
species into close contact (mosaic hybrid zones: Rand and Harrison 1989).