When hybrids are not hybrids: a case study of a putative hybrid zone betweenCattleya coccineaandC. brevipedunculata(Orchidaceae)

Abstract

Cattleya coccinea and C. brevipedunculata (Orchidaceae) are closely related species distinguished primarily by geographical distribution, vegetative morphology and flowering period. Both species inhabit high‐elevation regions in south‐eastern Brazil, but are traditionally associated with different habitats, located in cloudy forests and campos rupestres (rocky fields), respectively. We used morphometrics and genetic variation of microsatellite markers to test the occurrence of a hybrid zone between these species located in Parque Estadual do Ibitipoca (PEI), Brazil. Morphological data reveal a continuum of variation between the putative taxa, influenced mainly by characters of leaf, pseudobulb and peduncle. However, genetic data do not support the occurrence of hybridization and introgression in PEI, showing that it is a pure population of C. brevipedunculata. Differences in vegetative characters among individuals from cloudy forests and campos rupestres suggest that morphological variation may be related to phenotypic plasticity in response to environmental light fluctuations, an unknown situation for this species. These results highlight the inconsistency of morphology for the identification of hybrids and the role of vegetative characters as a possible complicating factor for the taxonomy of these species, as they are subject to environmental influence.

Contact zones and their consequences: hybridization between two ecologically isolated wild Petunia species

“…The consequences of interspecific hybridization on species persistence can vary as a function of the genetic, demographic or geographical structure of each involved taxon (Yan et al, 2017) and may promote blurring the boundaries between species and evolutionary noise (Soltis & Soltis, 2009) and genetic erosion through introgression (Rieseberg & Wendel, 1993;Kenney & Sweigart, 2016), but can also cause adaptation and genetic divergence (Ellstrand, 2014;Meier et al, 2016) or have neutral effects (Arnold, 2006), with each species maintaining its limits. In Neotropical orchids, evolutionary success is attributed to the emergence of hybrid lineages (Pinheiro et al, 2010;Veja et al, 2013;Marques et al, 2014;Leal et al, 2016;Szlachetko et al, 2017), suggesting hybridization plays an important role in increasing diversity in this region, despite the fact that only a few plant groups have been studied.…”

Plant Species Complexes as Models to Understand Speciation and Evolution: A Review of South American Studies

“…One of the advantages of this approach is to identify cases of trait convergence, to avoid the study of unrelated paraphyletic groups. Rodrigues et al (2015) constructed a phylogenetic inference for the Cattleya coccinea complex, and the recognition of different clades was important for the detailed study of Leal et al (2016a), using morphometric and microsatellite analyses. The study performed by Welker et al (2015) also identified several clades within the genus Saccharum, allowing future studies to explore particular microevolutionary processes within each species group of this genus.…”

Himantoglossum adriaticum H. Baumann × Himantoglossum robertianum (Loisel.) P. Delforge: A New Interspecific Hybrid Assessed by Barcoding Analysis

“…Moreover, floral isolation is a form of prepollination reproductive isolation that can play an important role during the process of plant speciation, and, in the absence of geographic barriers to gene flow, can be the most important prezygotic barrier [ 24 ]. The increasing development and availability of suitable molecular markers have facilitated studies of natural hybridization, allowing to detect even low levels of introgression and to provide information about the potential gene flow and reproductive barriers between species [ 25 ].…”

“…Thanks to the intrinsic value of plant novelties, interspecific hybridization represents a useful tool in ornamental breeding. Although the expression of morphological traits in hybrids is unpredictable, it often results in a mosaic of parental, intermediate and new characters [ 25 , 41 ]. Considering the above-described peculiarities of both parental species, the ultimate goal of our breeding plan was to introduce valuable traits for new potted and garden flowering plants, or cut flowers.…”