Most animal species are selfish about sharing their genetic material with others. Indeed, most biologists define species that require two sexes for reproduction by their characteristic hoarding of their genes. If populations breed freely among themselves but refuse to share their DNA with other groups, then they are considered a species separate from all other species. For whatever reason, though, many plants are much more casual about such things. Many kinds considered as species by botanists readily hybridize with close relatives—and sometimes with more distant kinds. Oaks, for example, are infamous for their willingness to share, and in some limited areas, almost every tree will show some mixture of traits from different species. Yet, overall, most oaks retain their recognizability as separate kinds.
Such indiscretions, however, tend to make plant evolution somewhat
different from that of animals. Most animals, once separated into distinct species, are
forever immune from the genetic influence of relatives. Many plants, on the other hand,
happily retain a web, however tenuous, of genetic interconnections for ages beyond what
would be considered decent in animals.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.