Influence of Pleistocene climatic oscillations on the phylogeography and demographic history of endemic vulnerable trees (sectionMagnolia) of the Tropical Montane Cloud Forest in Mexico

Abstract

The Tropical Montane Cloud Forest (TMCF) is a highly dynamic ecosystem that has undergone frequent spatial changes in response to the interglacial-glacial cycles of the Pleistocene. These climatic fluctuations between cold and warm cycles have led to species range shifts and contractions-expansions, resulting in complex patterns of genetic structure and lineage divergence in forest tree species. In this study, we sequenced four regions of the chloroplast DNA (trnT-trnL, trnK5-matk, rpl32-trnL, trnS-trnG) for 20 populations and 96 individuals to evaluate the phylogeography, historical demography, and paleodistributions of vulnerable endemic TMCF trees in Mexico: Magnolia pedrazae (north-region), M. schiedeana (central-region), and M. schiedeana population Oaxaca (south-region). Our data recovered 49 haplotypes that showed a significant phylogeographic structure in three regions: north, central, and south. Bayesian Phylogeographic and Ecological Clustering (BPEC) analysis also supported the divergence in three lineages and highlighted the role of environmental factors (temperature and precipitation) in genetic differentiation. Our historical demography analyses revealed demographic expansions predating the Last Interglacial (LIG, ~125,000 years ago), while Approximate Bayesian Computation (ABC) simulations equally supported two contrasting demographic scenarios. The BPEC and haplotype network analyses suggested that ancestral haplotypes were geographically found in central Veracruz. Our paleodistributions modeling showed evidence of range shifts and expansions-contractions from the LIG to the present, which suggested the complex evolutionary dynamics associated to the climatic oscillations of the Pleistocene. Habitat management of remnant forest fragments where large and genetically diverse populations occur in the three TMCF regions analyzed would be key for the conservation of these magnolia populations.

The effect of climate change on Arcto‐Tertiary Mexican beech forests: Exploring their past, present, and future distribution

“…Our results exhibit that Mexican beech distributions projected from ecological niche models ( past , present , and future ) can provide a realistic potential geographic range proxy, and habitat suitability to identify ecological refugia. Nevertheless, it is necessary to consider connectivity among fragments as reported by Rodríguez‐Ramírez et al ( 2013 ) for Hidalgo Mexican beech forests, and population disequilibrium as shown in other Mexican TMCF tree species (e.g., Liquidambar styraciflua L., Ruiz‐Sanchez & Ornelas, 2014 ; Podocarpus spp., Ornelas et al, 2019 ; Magnolia schiedeana , Rico et al, 2021 ) from the perspective of autoecology, which is essential for management and conservation implications, with emphasis on the ecological refugia as was recorded in this study.…”

“…Arcto‐Tertiary Geoflora species (sensu Baskin & Baskin, 2016 ; Chaney, 1959 ) as currently distributed in the Mexican TMCFs include temperate tree genera with broad ecological tolerances (e.g., Carya , Fagus , Liquidambar , Liriodendron , Magnolia , Meliosma , and Tilia ; Graham, 1976 ). Therefore, the Mexican TMCFs have had a stable long‐term climate and remain in critical hotspots (known as Pleistocene glacial refugia; Rico et al, 2021 ) and possessed a high conservation priority for the long‐term persistence of relict‐forest communities (Tang et al, 2017 ). Before and during the Ice Ages (~100,000 year‐interval), several temperate deciduous broad‐leaved tree species (e.g., Quercus tardifolia C.H.…”

The past is uncertain: alternative responses of cloud forest mammals to the Last Glacial Maximum in the Oaxacan Highlands, Mexico

“…Soley‐Guardia et al, 2019). Alternative past climate scenarios should have led to different genetic signatures presently observable (Ornelas et al, 2019; Rico et al, 2021). Species may have passed through bottlenecks regarding expansion and contraction of abundance during the last glacial–interglacial cycle, which can be captured in the genetic signal of modern populations (Bennett & Provan, 2008; Ortiz & Jayat, 2012).…”

Glacial Expansion or Interglacial Expansion? Contrasting Demographic Models of Four Cold-Adapted Fir Species in North America and East Asia

“…Till now, the incongruence between the LGM (MIROC) and LGM (CCSM) had been widely surveyed (Guevara et al, 2019). The MIROC estimated noticeably more different climatic conditions than CCSM and suggested a remarkable different prediction of potential (Rico et al, 2021). Compared to the LGM (MIROC), the LGM (CCSM) model was much more effective and widely used in related Pinaceae species, such as the East Asian white pines (Liu et al, 2022).…”