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Plant Systematics and Evolution (2018) 304:511–519
https://doi.org/10.1007/s00606-018-1502-7
ORIGINAL ARTICLE
Incipient speciation in a neotropical Gesneriaceae: Columnea
kucyniakii is nested within C. strigosa
James F. Smith
1
· Maggie T.‑Y. Ooi
1
· John L. Clark
2
Received: 16 August 2017 / Accepted: 25 January 2018 / Published online: 13 February 2018
© Springer-Verlag GmbH Austria, part of Springer Nature 2018
Abstract
Speciation is an ongoing process. Many recognized species are fully divergent from each other and their ancestors, whereas
others are in earlier stages in the diversification process. Such incipient speciation may create patterns when one or a few
populations are phenotypically distinct, but lack genomic level coalescence from each other or from their ancestral species.
As a result, such progenitor-derivative species pairs are likely to lack reciprocal monophyly or generate paraphyletic ancestral
species. Here we examine phylogenetic patterns in the Columnea strigosa (Gesneriaceae) complex to evaluate whether popu-
lations that have been named C. kucyniakii are reciprocally monophyletic with C. strigosa, its presumed ancestral species.
Molecular phylogenetic results do not support reciprocal monophyly of the two species, implying that incipient speciation is
occurring within the C. strigosa complex. We hereby recommend that C. kucyniakii be recognized at the specific rank despite
the fact that it creates a paraphyletic C. strigosa. These findings bear importance in taxonomic decisions about paraphyletic
taxa and recognizing evolutionary and morphologically distinct lineages.
Keywords Coalescence · Paraphyly · Progenitor-derivative species pairs · Reciprocal monophyly
Introduction
Speciation is the process of an ancestral species diverging
into two distinct species (Darwin 1859). Speciation can be
rapid in a few documented cases of allopolyploidy (Ownbey
1950; Soltis and Soltis 1989; Ozkan et al. 2001), but more
often is considered a slow process whereby localized and
often isolated populations diverge from the remainder of the
ancestor species either through drift or selection (Rice and
Salt 1988; Benton and Pearson 2001; Rosindell et al. 2010).
Early in the speciation process (incipient speciation), it is
possible that a small subset of populations or even a single
population may diverge from the remainder and be read-
ily recognized on the basis of phenotypic characters (mor-
phology, behavior, ecology) from the ancestral species, yet
complete genomic coalescence is likely to lag, creating a
monophyletic descendent and a paraphyletic progenitor spe-
cies (Gottlieb 1973; Crawford and Smith 1982; Crawford
2010). It is expected that given sufficient time, both ances-
tor and descendent species would coalesce to monophyly,
either through gene flow among the ancestral paraphyletic
populations of the ancestor species, or extirpation of popula-
tions that cause the ancestor to be paraphyletic (Anacker and
Strauss 2014). Discovery of paraphyly in ancestor–descend-
ent species pairs implies an early stage in the speciation
process.
Advances in molecular phylogenetics have been able to
identify populations that are diagnosable on the basis of phe-
notypes within a larger polymorphic group. In many cases,
not all of the phenotypically diagnosable groups are mono-
phyletic (Anacker and Strauss 2014; Lachance and Fedor
2014; Dantas et al. 2016; Stervander et al. 2016; Yin et al.
2016; Demos et al. 2017). In most cases, such advances
have altered the taxonomy such that taxa at all levels reflect
monophyly.
Handling editor: Yunpeng Zhao.
Electronic supplementary material The online version of this
article (https ://doi.org/10.1007/s0060 6-018-1502-7) contains
supplementary material, which is available to authorized users.
* James F. Smith
jfsmith@boisestate.edu
1
Department of Biological Sciences, Boise State University,
1910 University Drive, Boise, ID 83725, USA
2
The Lawrenceville School: Science Department, The
Lawrenceville School, 2500 Main Street, Lawrenceville,
NJ 08648, USA
@Phil_Robichaud
@deepthiw
@JoseServera