Intergeneric Hybridization in Flowering Plants

Knobloch, Irving W.

doi:10.2307/1219229

Cited by 74 publications

(39 citation statements)

References 7 publications

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“…It has been confirmed that this phenomenon is both geographically and phylogenetically widespread (Knobloch 1972;Rieseberg 1995). Different outcomes are possible: hybrids have a very low viability and hybridization does not progress beyond the F 1 stage (Pellegrino et al 2009), or hybrid zones can stabilize and persist, a new species can be formed, introgression of genetic material of one species into the other can occur, or one of the species could go locally extinct, or cease to persist as a separate entity as a direct result of extensive gene flow from the second species (Rieseberg and Wendel 1993;Arnold 1997).…”

Section: Introductionmentioning

confidence: 74%

Hybridization in Annual Plants: Patterns and DynamicsDuring a Four-Year Study in Mixed Rhinanthus Populations

2010

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Hybridization in annual plants is rare, but their short life cycle provides an excellent opportunity to study the dynamics of hybridization. Hybridization occurs between the annual hemiparasites Rhinanthus minor and Rhinanthus angustifolius (Orobanchaceae). Using flower morphology, Kwak (1980) found a prevalence of hybrids close to R. angustifolius in a single population. We aim to find whether this pattern is also found using genetic markers, whether it is generally occurring in mixed populations, and whether these populations are stable over time. We used species-specific genetic markers to determine the number of individuals in a range of hybrid classes in three mixed populations of different ages during four consecutive years. In the young population, F 1 hybrids were found in the first year and mostly hybrids between R. minor and these F 1 s in the second year, but in the years after that, hybrids close to R. angustifolius became more abundant. We also found this in the two older populations, where hybrids close to R. angustifolius always occurred in higher frequencies than hybrids close to R. minor. Over time, R. angustifolius strongly increased in frequency in two populations. Patterns of marker presence and absence suggested that advanced-generation hybrids are mainly formed by backcrossing with one of the parents, predominantly R. angustifolius whenever its frequency in the population is higher than 15%. The dynamics of mixed populations depend on the ecological conditions that regulate the presence of the two parental species, and introgression into R. angustifolius seems prevalent.

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Section: Introductionmentioning

confidence: 74%

Hybridization in Annual Plants: Patterns and DynamicsDuring a Four-Year Study in Mixed Rhinanthus Populations

2010

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“…3). In fact such hybridization and introgression events have been reported between species belonging to different genera and even different families in some groups of organisms such as turtles, birds, and some plants (e.g., Owen 1941;Montagu 1950;Knobloch 1972;Karl et al 1995;McCarthy 2006;Fritz & Havaš 2007).…”

Section: Monophylymentioning

confidence: 99%

To name or not to name: Criteria to promote economy of change in Linnaean classification schemes

Vences¹,

Guayasamín²,

Miralles³

et al. 2013

Zootaxa

157

177

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The Linnaean classification system provides the universal reference system for communicating about the diversity of life and its hierarchic history. Several limitations that challenge the stability of this system have been identified and, as a result, alternative systems have been proposed since its early inception. The revolution caused by molecular phylogenetics has, more than ever, exemplified that Linnaean classification schemes are subject to a degree of instability that may hamper their significance and communication power. Our analysis of recent changes in the classification of several groups of organisms, with a focus on amphibians and reptiles, reveals two main sources of instability: (i) revisionary, objective (empirical) changes based on the discovery of unambiguous instances of non-monophyly and on progress in the Globe's species inventory, and (ii) subjective changes based on author preferences or on a poor analysis of the advantages and limitations of new classification schemes. To avoid subjective taxonomic instability, we review and elaborate proposals for the assignment of Linnaean rank to clades, and thereby for the naming of these clades as Linnaean taxa (Taxon Naming Criteria: TNCs). These are drafted from the perspective of practicing taxonomists and can help choosing among alternative monophyly-based classifications under a premise of economy of change. We provide a rationale for each TNC along with real and theoretical examples to illustrate their practical advantages and disadvantages. We conclude that not all TNCs lead to equally informative and stable taxonomies. Therefore, we order the various TNCs by the generality of their implications and provide a workflow scheme to guide the procedure of taxonomic decisions concerning the creation or modification of supraspecific classifications. The following criteria are considered primary when naming taxa: (i) Monophyly of the taxon in an inferred species tree; (ii) Clade Stability, i.e., the monophyly of a clade to be named as taxon should be as strongly supported as possible by various methods of tree inference, tests of clade robustness, and different data sets; and (iii) Phenotypic Diagnosability, i.e., ranked supraspecific taxa should be those that are phenotypically most conspicuous although in phenotypically cryptic groups of organisms it can be warranted to name taxa based on molecular differences alone. We consider various other criteria as secondary (i.e., the Time Banding, Biogeography, Adaptive Zone, and Hybrid Viability TNCs) and refute using them as sole arguments for the modification of established classifications or proposal of new ones. Taxonomists are encouraged to be explicit and consistent when applying TNCs for creating or modifying classifications. We emphasize that, except for monophyly, the priority TNCs are not proposed as mandatory requisites of a Linnaean taxon but as yardsticks to allow for an informed choice among various clades in a tree that could alternatively be named as Linnaean taxa. Despite a need for plurality, classifications should avoid deliberately violating any of the three primary TNCs because taxa of unstable monophyly or poor diagnosability reduce the information content and hence the utility of the Linnaean system.

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“…Hybridization and introgression have long been viewed as important in plant evolution and speciation (Knobloch 1972;Grant 1981;Ellstrand et al 1996;Arnold 1997;Rieseberg et al 2003;Mallet 2007). Hybridization involving chromosome doubling (i.e., allopolyploidization) is an especially well-established mode of speciation in plants (Levin 2002;Mallet 2007).…”

Section: Introductionmentioning

confidence: 99%

Molecular confirmation of the hybrid origin of the critically endangered western Mediterranean endemic Sonchus pustulatus (Asteraceae: Sonchinae)

2008

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The critically endangered composite Sonchus pustulatus Willk. despite being known from fewer than ten locations in southern Spain and northern Africa, has never been characterized in robust phylogenetic context. Here, we report molecular evidence that strongly supports a hybrid origin for S. pustulatus. Although parentage cannot be identified with certainty, analysis of DNA sequence variation from the internal transcribed spacer (ITS) region of nuclear ribosomal DNA (nrDNA) supports a phylogenetic placement of S. pustulatus close to other species in the poorly known section Pustulati, whereas examination of chloroplast DNA (cpDNA) places S. pustulatus most closely with species from the sections Sonchus and Asperi. This is one of several instances of topological non-concordance reported for the genus Sonchus. Monophyly of S. pustulatus in both gene genealogies supports the null hypothesis of a single origin, and the relatively large amount of nucleotide substitutions is indicative of an origin in the range of millions of years. A hypothesis of a northern African origin of S. pustulatus followed by dispersal to the Iberian Peninsula during the Messinian salinity crisis/later Quaternary glaciations is proposed on the basis of biogeographic patterns and calibrated estimations of molecular evolution.

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Intergeneric Hybridization in Flowering Plants

Cited by 74 publications

References 7 publications

Hybridization in Annual Plants: Patterns and DynamicsDuring a Four-Year Study in Mixed Rhinanthus Populations

Hybridization in Annual Plants: Patterns and DynamicsDuring a Four-Year Study in Mixed Rhinanthus Populations

To name or not to name: Criteria to promote economy of change in Linnaean classification schemes

Molecular confirmation of the hybrid origin of the critically endangered western Mediterranean endemic Sonchus pustulatus (Asteraceae: Sonchinae)

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