Conserving tree populations safeguards forests since they represent key elements of the ecosystem. The genetic characteristics underlying the evolutionary success of the tree growth form: high genetic diversity, extensive gene flow and strong species integrity, contribute to their survival in terms of adaptability. However, different biological and landscape contexts challenge these characteristics. This study employs 63 de novo developed microsatellite or SSR (Single Sequence Repeat) markers in different datasets of nine Neotropical Magnolia species. The genetic patterns of these protogynous, insect-pollinated tree species occurring in fragmented, highly-disturbed landscapes were investigated. Datasets containing a total of 340 individuals were tested for their genetic structure and degree of inbreeding. Analyses for genetic structure depicted structuring between species, i.e. strong species integrity. Within the species, all but one population pair were considered moderate to highly differentiated, i.e. no indication of extensive gene flow between populations. No overall correlation was observed between genetic and geographic distance of the pairwise species’ populations. In contrast to the pronounced genetic structure, there was no evidence of inbreeding within the populations, suggesting mechanisms favouring cross pollination and/or selection for more genetically diverse, heterozygous offspring. In conclusion, the data illustrate that the Neotropical Magnolias in the context of a fragmented landscape still have ample gene flow within populations, yet little gene flow between populations.

The Mexican state of Veracruz has suffered very high deforestation rates in the last few decades, and despite the establishment of protected areas and conservation projects, primary forest is now mainly persisting in mostly small, scattered, fragmented remnants. New species of Magnolia section Talauma in this state have been described with little to no reference to the already existing ones, potentially resulting in over-splitting, obscuring their taxonomic delineation and conservation status, and consequently conservation programs. To study the conservation units and their genetic diversity, we here employ 15 microsatellite markers on a highly representative sampling of 254 individuals of what are presumed to be five Magnolia species. The results support at least three species and maximum five main conservation units. We propose downgrading the latter to four, given morphological, ecological, demographical, and geographical considerations. Two out of the three sympatrically occurring species in the rainforest in the Los Tuxtlas volcanic area have weak genetic evidence to be considered separate species. Similarly, the individuals in the Sierra de Zongolica in central Veracruz, who bear a very high morphological and genetic similarity to Magnolia mexicana, have weak genetic evidence to be recognised as a separate species. Nonetheless, the individuals could be identified as Magnolia decastroi based on morphology, and further research including the full range of this species is recommended.

The Caribbean islands provide an ideal setting for studying biodiversity, given their complex geological and environmental history, and their historical and current geographical proximity to the American mainland. Magnolia, a flagship tree genus that has 15 endemic and threatened taxa (12 species and 3 subspecies) on the Caribbean islands, offers an excellent case study to empirically test Caribbean biogeographical hypotheses. We constructed phylogenetic hypotheses to: (1) reveal their evolutionary history, (2) test the current largely morphology-based classification and assess species limits, and (3) investigate major biogeographic hypotheses proposed for the region. Nuclear and chloroplast DNA sequence data of all 15 Caribbean Magnolia taxa are included, supplemented by a selection of American mainland species, and species representing most major clades of the Magnoliaceae family. We constructed phylogenetic hypotheses in a time-calibrated Bayesian framework, supplemented with haplotype network analyses and ancestral range estimations. Genetic synapomorphies in the studied markers confirm the species limits of 14 out of 15 morphologically recognizable Caribbean Magnolia taxa. There is evidence for four colonization events of Magnolia into the Caribbean from the American mainland, which most likely occurred by overwater dispersal, given age estimates of maximum 16 mya for their presence on the Caribbean islands.

Special conservation efforts should be made for relict species, as they usually have small population sizes and restricted distributions, placing them in critical extinction risk. To achieve conservation, information about genetic diversity distribution is needed. Here, using nine nuclear microsatellites, we analyzed 23 populations of five recently described species of Magnolia distributed in Mexico, which were previously assigned to Magnolia dealbata. We aimed to determine the level of genetic diversity and the distribution of genetic variation and proposed conservation measures. Compared to other endemic and relict species, we found a moderate level of genetic diversity in most populations; however, we identified two populations with no genetic variation. Additionally, we found evidence of positive values of inbreeding likely due to geitonogamy. We found a strong population structure, low effective population size, and no evidence of bottlenecks. Patterns of genetic differentiation did not support the morphological distinction of five species, so we hypothesized that the gene pools may instead represent well-differentiated populations of a single species. We argue that the pattern of genetic differentiation is explained by the natural fragmentation of the cloud forests after glaciation events, and the effects of genetic drift in small populations poorly connected by gene flow. Despite the moderate levels of genetic diversity, special attention is needed to guarantee conservation, with emphasis on the populations in the central region of the country as well as the valuable populations identified in the southwestern region.

Genetic data on threatened plant populations can facilitate the development of adequate conservation strategies to reduce extinction risk. Such data are particularly important for species affected by habitat fragmentation such asMagnolia cubensissubsp.acunae, a Critically Endangered magnolia subspecies endemic to Cuba. Using genetic data from 67 individuals, we aimed to evaluate the effect of habitat fragmentation on two subpopulations in the Guamuhaya mountain range, in Topes de Collantes Protected Natural Landscape and Lomas de Banao Ecological Reserve. We characterize the structure and genetic diversity of these subpopulations, with the objective of managing their conservation more effectively. We used Landsat satellite images to determine land-cover types at the two locations and calculated indices of habitat fragmentation. For genetic analyses, we extracted DNA from the leaf tissue of individuals from the two subpopulations and used 11 microsatellite markers to genotype them. We calculated heterozygosity, allelic richness and theF-statistics, to evaluate genetic variability. The montane rainforest in Topes de Collantes was most affected by habitat fragmentation, with smaller patches of more irregular shapes, compared to submontane forest at this location and both montane and submontane forests in Lomas de Banao. Genetic diversity was higher in Topes de Collantes, but we found no genetic differentiation between subpopulations. Our findings suggest the two subpopulations can be considered a single evolutionary unit and conservation entity. We propose to use individuals from both subpopulations for reinforcement to increase the overall genetic diversity of the subspecies.