Natural hybridisation among Quercus glabrescens, Q. rugosa and Q. obtusata (Fagaceae): Microsatellites and secondary metabolites markers

Abstract

Natural hybridization has significant ecological, genetic and evolutionary consequences altering morphological and chemical characters of individuals. Quercus glabrescens, Q. rugosa and Q. obtusata are white oak species well separated by their morphological characters when they occur in allopatry in Mexican temperate forests. However, in sympatry, individuals with atypical morphology have been observed, suggesting hybridization events. In this study, we determined with microsatellites and secondary metabolites if interspecific gene flow occurs when these three-oak species coexist in sympatry. In total, 180 individuals belonging to seven populations [three allopatric (one for each parental species) and four sympatric sites] were analyzed. Allopatric populations represent well defined genetic groups and the sympatric populations showed genetic evidence of hybridization between Q. glabrescens × Q. rugosa and Q. glabrescens × Q. obtusata. The hybridization percentage varied between sites and combination of involved species. We registered the presence of unique flavonoid compounds for Q. glabrescens (caffeic acid and flavonol 2), Q. rugosa (flavonol 5), Q. obtusata (flavonol 1). Three compounds (quercetin rhamnoside, flavonol 3 and alkyl coumarate) were expressed in all taxa. Finally, the hybrid genotypes identified in this study (Q. glabrescens × Q. rugosa and Q. glabrescens × Q. obtusata) showed particular chemical profiles, resulting from combination of those of their parental species. These results show that hybridization events between these oak species alter chemical expression of secondary metabolites, creating a mosaic of resources and conditions that provide the substrate for different combinations of foliar-associated species as herbivores, endophytic fungi or epiphyte plants. This article is protected by copyright. All rights reserved.

Hybridization: a ‘double-edged sword’ for Neotropical plant diversity

“…This is likely to be modulated by differential introgression across the genome resulting from selection against hybrids in different environments (Ramos-Ortiz et al, 2016;Pérez-Pedraza et al, 2021). In other Central American Quercus spp., evidence of older reticulation at deep phylogenetic scale has also been shown with RADseq data, albeit on a localized basis (Eaton et al, 2015), and that hybridization can alter expression of secondary metabolites and generate variation in these traits (Castillo-Mendoza et al, 2019).…”

Oaks: an evolutionary success story

“…Hybridization is widespread within sections of the Quercus genus and has received considerable attention during the last decade, as illustrated by examples in white oaks, sect. Quercus (Ishida et al , ; Curtu et al , ; Lepais & Gerber, ; Castillo‐Mendoza et al , ), southern live oaks, sect. Virentes (Cavender‐Bares & Pahlich, ; Eaton et al , ), red oaks, sect.…”

Species delimitation in the genus Quercus (Fagaceae)

“…Studies on oak hybridization and introgression are generally carried out in two-species systems, however in the last decade, some analyses have identified three-to sixspecies systems with gene flow in American oaks (Dodd & Afzal-Raffii 2004, Peñaloza-Ramírez et al 2010, Zhang et al 2015, Sullivan et al 2016, Castillo-Mendoza et al 2018.…”