Hybrids in Botany: Some Exist, Some Do Not

Table of Contents Summary
Introduction
True Hybrids
"Hybrid" as a Code Word For "This plant is confusing"

Summary

There is no doubt that hybridization occurs in plants. Studies of hybridization have produced fundamental data for genetics, and hybrids are the stars of the gardening and agriculture worlds. However, in the wild, hybrids do not occur nearly as frequently as claims for hybridization. All too often, calling a plant a hybrid is the equivalent of waving a magic wand that allows a botanist to suspend further study of a specimen or to dismiss obvious contradictions between the specimen and its species as described in a flora.

This paper gives specific examples of plants, and plant groups, where the supposed hybrid nature evaporates upon further investigation.

Introduction

True Hybrids

"Hybrid" as a Code Word For "This plant is confusing"

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Copyright © 2004 by Tom Chester and Jane Strong
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Comments and feedback: Tom Chester | Jane Strong
Last update: 27 January 2004

 i've seen hybridization in a number of subspecies, which has always taken the form of producing intermediates between the two, and usually with a number of specimens that represent the nearly pure subspecies. (examples: eriogonum fasciculatum ssp. polifolium and ssp. foliolosum; salvia mellifera and apiana; gutierrezia california and sarothrae; quercus engelmannii and berberidifolia.) i've never seen a hybrid population that produces something outside the range of the parents (although i know of no fundamental genetic reason why that might not happen in some cases). Your assumption that hybrids are always intermediate is ok but it is not a universal phenomenon. In fact, there is considerable literature that now shows that in many hybridizing taxa, hybrids may resemble one parent more so than the other (condition 1), a function of what traditionally has been called dominance or over-dominance. In other cases, hybridization leads to new character combinations that are not intermediate in the traditional sense (condition 2). In fact, Gottlieb has provided evidence for "condition 1" as above for hybrids involving virgata and pleurocarpa, based on experimental evidence. He also has shown that hybridization with other species of Stephanomeria may have influenced local variation. In fact, S. diegensis is probably derived from hybridization between S. virgata and S. exigua (most likely subsp. deanei), according to several recent published studies using molecular techniques and a re-evaluation of morphological variation. The pattern of character variation in S. diegensis is an example of "condition 2" above, something that has been referred to as "recombinational speciation".