Leaf morphology of progenies in Q. suber, Q. ilex, and their hybrids using multivariate and geometric morphometric analysis

Abstract

The genus Quercus is known for the occurrence of frequent hybridization events between species. Although this phenomenon is not common among holm oak (Q. ilex) and cork oak (Q. suber), these species can hybridize when they coexist in mixed stands. The result of hybridization is a viable hybrid progeny with very heterogeneous leaf morphology. Literature concerning the leaf morphology of suber-ilex hybrid seedlings is scarce, and non-existent from a quantitative point of view. In the case of the leaf morphology of hybrids and their progeny, it has been observed a high frequency of leaves with fluctuating asymmetry or developmental abnormalities, which can have a marked effect on fitness. In this work, we have characterized seedlings' leaf morphology corresponding to two-and four-year-old half-sib progenies of holm oak, cork oak and their hybrids. For this purpose, three to ten leaves of each individual were collected, and two methodologies were used for analysis. Firstly, we used a classic morphological analysis of twelve variables that were reduced using multivariate techniques. On the other hand, shape of the leaves was thoroughly analyzed by geometric morphometric analysis methods. The extent of fluctuating asymmetry and the presence of developmental abnormalities of seedlings were analyzed calculating an asymmetry index. The results indicate that thickness is the most discriminating trait between species, and that the hybrid progenies do not show a third different phenotype compared to the parental species. However, half-siblings tend to show similar leaf morphology between them, depending on the genetic adscription of the parents. While fluctuating asymmetry was found in half-sib progenies of the parental species and the hybrids, a significant proportion of hybrid half-sibs showed strong leaf asymmetry, probably due to modifications of the epigenetic systems that control leaf development at the shoot apical meristems and leaf primordia.

ddRAD Sequencing-Based Identification of Genomic Boundaries and Permeability in Quercus ilex and Q. suber Hybrids

“…Later on, other combinations can also be deleterious, as confirmed by the low germination rate of hybrid acorns in this study (56.92% in hybrids, compared to 89.24% in Q. suber and up to 92.95% in Q. ilex), consistent with previous studies in other areas (Loṕez de Heredia et al, 2018a). Although many morphological anomalies already described in Q. suber x ilex hybrid seedlings (Loṕez de Heredia et al, 2017;Loṕez de Heredia et al, 2018b) were present in part of the seedlings, we have scored low mortality in nursery conditions over three years since seedlings emergence. Nevertheless, selection against certain genomic combinations-late-acting genetic incompatibilitiesduring the juvenile phases of hybrid individuals with major Q. suber ancestry could also account for the higher contribution of Q. ilex to the genome of surviving hybrids.…”

Qualitative and Quantitative Anatomical Analysis of the Constitutive Bark of Q. ilex x Q. suber Hybrids

“…The occurrence of Q. ilex x suber hybrids ( Quercus x morisii Borzí; Quercus x avellaniformis Colmeiro & E. Boutelou) has long been known and botanical descriptions present these hybrids as having viable acorns with conical cupules with free bracts, glabrescent leaves of light green tone and strongly cracked bark [ 14 , 15 , 16 , 17 , 18 ]. These hybrids also present micro-morphological and anatomical characters related to the presence/absence and distribution of foliar trichomes [ 19 ] and to the thickness of the leaf lamina [ 20 ].…”

Divergent scute asymmetry among pure and crossed individuals of Testudo hermanni (Gmelin, 1789)

“…In the literature there are well-documented situations in which inter-species hybridisation increases bilateral asymmetry, both in vegetal species (Albarrán-Lara et al, 2010;Cuevas-Reyes et al, 2018;De Heredia et al, 2018) and in animals (Alibert et al, 1994; Table 1. Measurement error Procrustes ANOVA for shape of plastral scute symmetry for female T. hermanni hermanni (n = 23) and their crosses (n = 8), with a significant effect of 'side*individual' effect (FA) for both groups.…”

“…Both genomic and environmental changes can increase FA, representing a possible deterioration in developmental homeostasis that is apparent in adult morphology (de Coster et al, 2013;Ducos and Tabugo, 2014). Hybridization is one of the biological factors underlying the changes in levels of FA (De Heredia et al, 2018). Genetic hypotheses have been proposed to explain the changes of FA in hybrids, as any change in genetic pool can result in a change of developmental stability (Carter et al, 2009;Albarrán-Lara et al, 2010;Demontis et al, 2010).…”