Divergence and reticulation in the Mexican white oaks: ecological and phylogenomic evidence on species limits and phylogenetic networks in the Quercus laeta complex (Fagaceae).

Background And Aims: Introgressive hybridization poses a challenge to taxonomic and phylogenetic understanding of taxa, particularly when there are high numbers of co-occurring, intercrossable species. The genus Quercus exemplifies this situation. Oaks are highly diverse in sympatry and cross freely, creating syngameons of interfertile species.

Leaf morphometric analysis and potential distribution modelling contribute to taxonomic differentiation in the Quercus microphylla complex.

Mexico is a major center of evolutionary radiation for the genus Quercus, with oak species occurring across different habitat types and showing a wide variation in morphology and growth form. Despite representing about 20% of Mexican species, scrub oaks have received little attention and even basic aspects of their taxonomy and geographic distribution remain unresolved. In this study, we analyzed the morphological and climatic niche differentiation of scrub oak populations forming a complex constituted by six named species, Quercus cordifolia, Quercus frutex, Quercus intricata, Quercus microphylla, Quercus repanda, Quercus striatula and a distinct morphotype of Q.