High genetic diversity and stable Pleistocene distributional ranges in the widespread Mexican red oak Quercus castanea Née (1801) (Fagaceae)

Abstract

The Mexican highlands are areas of high biological complexity where taxa of Nearctic and Neotropical origin and different population histories are found. To gain a more detailed view of the evolution of the biota in these regions, it is necessary to evaluate the effects of historical tectonic and climate events on species. Here, we analyzed the phylogeographic structure, historical demographic processes, and the contemporary period, Last Glacial Maximum (LGM) and Last Interglacial (LIG) ecological niche models of Quercus castanea, to infer the historical population dynamics of this oak distributed in the Mexican highlands. A total of 36 populations of Q. castanea were genotyped with seven chloroplast microsatellite loci in four recognized biogeographic provinces of Mexico: the Sierra Madre Occidental (western mountain range), the Central Plateau, the Trans‐Mexican Volcanic Belt (TMVB, mountain range crossing central Mexico from west to east) and the Sierra Madre del Sur (SMS, southern mountain range). We obtained standard statistics of genetic diversity and structure and tested for signals of historical demographic expansions. A total of 90 haplotypes were identified, and 29 of these haplotypes were restricted to single populations. The within‐population genetic diversity was high (mean hS = 0.72), and among‐population genetic differentiation showed a strong phylogeographic structure (NST = 0.630 > GST = 0.266; p < .001). Signals of demographic expansion were identified in the TMVB and the SMS. The ecological niche models suggested a considerable percentage of stable distribution area for the species during the LGM and connectivity between the TMVB and the SMS. High genetic diversity, strong phylogeographic structure, and ecological niche models suggest in situ permanence of Q. castanea populations with large effective population sizes. The complex geological and climatic histories of the TMVB help to explain the origin and maintenance of a large proportion of the genetic diversity in this oak species.

Climatic and anthropogenic influences on vegetation changes during the last 5000 years in a seasonal dry tropical forest at the northern limits of the Neotropics

“…Therefore, late-Holocene fossil pollen spectra in this study point to a larger presence of this plant community at the site. This agrees with evidence on the permanence of a large population of Q. castanea in the TMVB since the Pleistocene (Peñaloza-Ramírez et al, 2020).…”

Nuclear and chloroplast DNA phylogeography reveals high genetic diversity and postglacial range expansion in Quercus mexicana

“…All the populations of Q. mexicana revealed high nuclear genetic diversity values, consistent with those reported in other studies of oaks in North America (Craft et al, 2002;Craft and Ashley, 2007;Abraham et al, 2011;Ortego et al, 2012;Ramos-Ortiz et al, 2016;Oyama et al, 2018;Peñaloza-Ramírez et al, 2020) and Asia (Ohsawa et al, 2011;San Jose-Maldia et al, 2017;Jiang et al, 2019).…”

“…The maintenance of high levels of genetic diversity within this species may be related to its longterm stable distribution and large effective population sizes for a long period. Habitat stability has been positively associated with high genetic diversity in other plant species (Gugger et al, 2013;Loera et al, 2017;Peñaloza-Ramírez et al, 2020).…”

“…The chloroplast genetic diversity of Q. mexicana was also high compared to most of the American oaks and comparable only to two species, Q. deserticola in Mexico (Rodríguez-Gómez et al, 2018) Interestingly, the cpDNA diversity of the species and its distribution varied greatly; for example, haplotype diversity ranged from 0.0 to 0.95, and 74% of the sampling locations showed private haplotypes. Despite that large effective population sizes for long periods may have promoted high levels of genetic variation, wide distribution, and high levels of private haplotypes suggests historical isolation of populations due to low acorn dispersal capacity, as is common in oaks (Ruíz-Sánchez et al, 2012;Ramos-Ortiz et al, 2016;Sork et al, 2016;Rodríguez-Gómez et al, 2018;Ochoa-Zavala et al, 2019;Peñaloza-Ramírez et al, 2020).…”

The role of niche breadth in oak phylogeography: Quercus glaucoides as a study case

“…Previous phylogeographic studies in widespread and abundant neotropical oak species have consistently revealed high genetic diversity and moderate differentiation, even at cpDNA markers, suggesting a different population history in comparison to oak species distributed in temperate latitudes. The interpretation has been that these differences in phylogeographic patterns reflect contrasting population histories: While temperate oaks experienced dramatic reductions and shifts in their distribution areas, range size fluctuations were moderate in neotropical species, with altitudinal rather than latitudinal migrations and more constant effective population sizes (González‐Rodríguez et al, 2004; Peñaloza‐Ramírez et al, 2020; Rodríguez‐Gómez et al, 2018; Tovar‐Sánchez et al, 2008). According to present and historical potential distribution maps, the geographic range size of Q. glaucoides fluctuated from −49% (during the LIG and the MH) to +8% (during the LGM) in comparison to the present‐day range size, which is comparable to the fluctuations inferred in other Mexican oaks (Peñaloza‐Ramírez et al, 2020; Rodríguez‐Gómez et al, 2018).…”