Dataset Information

The phylogeography of the cycad genus Dioon (Zamiaceae) clarifies its Cenozoic expansion and diversification in the Mexican transition zone.

ABSTRACT: Background and Aims:Biogeographic transition zones are promising areas to study processes of biogeographic evolution and its influence on biological groups. The Mexican transition zone originated due to the overlap of Nearctic and Neotropical biota, which promoted great biological diversification. However, since most previous studies in this area were focused on revealing the phylogeography of Nearctic plants, how historical biogeographic configuration influenced the expansion and diversification of the Neotropical flora remains almost unknown. Using the cycad genus Dioon (Zamiaceae), this study aimed to test whether the biogeographic provinciality of the Mexican transition zone reflects the history of diversification of Neotropical plants. Methods:Two chloroplast DNA (cpDNA) regions were analysed from 101 specimens of 15 Dioon species to reveal the distribution of haplogroups. In addition, genome-wide single nucleotide polymorphisms (SNPs) from 84 specimens were used to test the concordance between phylogenetic clusters and the biogeographic provinces. An ultrametric tree was constructed from the sequences containing SNPs to reconstruct the biogeographic events of vicariance and dispersal of Dioon across the Neotropical biogeographic provinces. Key Results:Four Dioon lineages with strong phylogeographic structures were recognized using both cpDNA and SNP data. The lineages correspond to two clades that originated from a common ancestor in Eastern Mexico. One clade expanded and diversified in South-east Mexico and Central America. Another clade diversified into three lineages that dispersed to North-east, South and North-west Mexico. Each lineage was biogeographically delimitated. Biogeographic provinces might have provided disparate ecological conditions that facilitated speciation in Dioon since the Miocene. Conclusions:The current genetic structure and species diversity of Dioon depict the history of expansion and diversification of the northernmost Neotropical provinces. Past biogeographic connectivities were favoured by elevated topographies, since mountain systems served as corridors for the migration of Dioon and as refugia of tropical communities that diversified during the formation of modern Neotropical forests.

SUBMITTER: Gutierrez-Ortega JS

PROVIDER: S-EPMC5838841 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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The phylogeography of the cycad genus Dioon (Zamiaceae) clarifies its Cenozoic expansion and diversification in the Mexican transition zone.

Gutiérrez-Ortega José Said JS Salinas-Rodríguez María Magdalena MM Martínez José F JF Molina-Freaner Francisco F Pérez-Farrera Miguel Angel MA Vovides Andrew P AP Matsuki Yu Y Suyama Yoshihisa Y Ohsawa Takeshi A TA Watano Yasuyuki Y Kajita Tadashi T

Annals of botany 20180301 3

<h4>Background and aims</h4>Biogeographic transition zones are promising areas to study processes of biogeographic evolution and its influence on biological groups. The Mexican transition zone originated due to the overlap of Nearctic and Neotropical biota, which promoted great biological diversification. However, since most previous studies in this area were focused on revealing the phylogeography of Nearctic plants, how historical biogeographic configuration influenced the expansion and divers ...[more]

PMID: 29293877

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Project description:Background and Aims:Aridification is considered a selective pressure that might have influenced plant diversification. It is suggested that plants adapted to aridity diversified during the Miocene, an epoch of global aridification (?15 million years ago). However, evidence supporting diversification being a direct response to aridity is scarce, and multidisciplinary evidence, besides just phylogenetic estimations, is necessary to support the idea that aridification has driven diversification. The cycad genus Dioon (Zamiaceae), a tropical group including species occurring from humid forests to arid zones, was investigated as a promising study system to understand the associations among habitat shifts, diversification times, the evolution of leaf epidermal adaptations, and aridification of Mexico. Methods:A phylogenetic tree was constructed from seven chloroplast DNA sequences and the ITS2 spacer to reveal the relationships among 14 Dioon species from habitats ranging from humid forests to deserts. Divergence times were estimated and the habitat shifts throughout Dioon phylogeny were detected. The epidermal anatomy among Dioon species was compared and correlation tests were performed to associate the epidermal variations with habitat parameters. Key Results:Events of habitat shifts towards arid zones happened exclusively in one of the two main clades of Dioon. Such habitat shifts happened during the species diversification of Dioon, mainly during the Miocene. Comparative anatomy showed epidermal differences between species from arid and mesic habitats. The variation of epidermal structures was found to be correlated with habitat parameters. Also, most of the analysed epidermal traits showed significant phylogenetic signals. Conclusions:The diversification of Dioon has been driven by the aridification of Mexico. The Miocene timing corresponds to the expansion of arid zones that embedded the ancestral Dioon populations. As response, species in arid zones evolved epidermal traits to counteract aridity stress. This case study provides a robust body of evidence supporting the idea that aridification is an important driver of biodiversity.

Project description:BackgroundThis study documents cycad-human relationships in Mexico, Belize, Guatemala, El Salvador, and Honduras over the last 6000 years. The impetus was acute need for a better understanding of previously undocumented uses of cycads in this region, and the need to improve cycad conservation strategies using ethnobotanical data. We hypothesized that cycads are significant dietary items with no long-term neurological effects, are important to religious practice, and contribute to cultural identity and sense of place, but that traditional knowledge and uses are rapidly eroding. Guiding questions focused on nomenclature, food and toxicity, relationships to palms and maize, land management issues, roles in religious ceremony, and medicinal uses, among others, and contributions of these to preservation of cycads.MethodsFrom 2000 to 2017, the authors conducted 411 semi-structured ethnographic interviews, engaged in participant-observation in Mexican and Honduran communities, and carried out archival research and literature surveys.ResultsWe documented 235 terms and associated uses that 28 ethnic groups have for 57 species in 19 languages across 21 Mexican states and 4 Central American nations. Carbohydrate-rich cycads have been both famine foods and staples for at least six millennia across the region and are still consumed in Mexico and Honduras. Certain parts are eaten without removing toxins, while seed and stem starches are detoxified via several complex processes. Leaves are incorporated into syncretic Roman Catholic-Mesoamerican religious ceremonies such as pilgrimages, Easter Week, and Day of the Dead. Cycads are often perceived as ancestors and protectors of maize, revealing a close relationship between both groups. Certain beliefs and practices give cycads prominent roles in conceptions of sense of place and cultural heritage.ConclusionsCycads are still used as foods in many places. Though they do not appear to cause long-term neurological damage, their health effects are not fully understood. They are often important to religion and contribute to cultural identity and sense of place. However, because most traditional knowledge and uses are rapidly eroding, new community-based biocultural conservation efforts are needed. These should incorporate tradition where possible and seek inspiration from existing successful cases in Honduras and Mexico.

Project description:BACKGROUND:Lying in a shallow continental shelf cyclically affected by oscillating sea levels since the Miocene, the Seychelles islands are particularly interesting for evolutionary studies. Recent molecular studies are generating an emerging picture of the origin of its biota, yet very little is known regarding their phylogeographic structure or on the factors promoting diversification within the archipelago. Here we aimed to obtain a detailed depiction of the genetic structure and evolution of one of the most widespread vertebrate groups in the archipelago: the day-geckos of the genus Phelsuma. In parallel, we aimed to infer divergence times between species and subspecies, testing a long-standing hypothesis that argues for different time since sympatry between species as the cause of their different morphological differentiation across the archipelago. RESULTS:Molecular data corroborated the existence of two main lineages, corresponding to the two currently recognized species. Divergences between species likely date back to the Mio-Pliocene, while more recent, Pleistocenic, divergences are suggested within each species. Populations from outer islands share mtDNA haplotypes with inner island populations, suggesting very recent dispersals (or introductions). We found no evidence of current gene flow between species, but results pointed to the possibility of gene flow between (now allopatric) subspecies. Time estimates suggest a synchronous divergence within each species (between island groups). CONCLUSIONS:The geographic patterns of genetic variation agree with previous taxonomic subdivisions within each species and the origin of outer islands populations is clearly tracked. The similar intraspecific divergence time estimates obtained suggest that the differential body-size differentiation between species within each group of islands may be driven by factors other than character displacement proportional to time since sympatry, as previously suggested. These factors could include different habitats/resources available within each island group, niche differentiation and/or character displacement. We also bring again into consideration the hypothesis of body size being influenced by the distribution of native vegetation and social systems within this group, although it remains to be tested. Our results highlight not only the necessity of clarifying the role of ecology and interspecific interactions in this group's morphological diversification and community assemblage, but also the importance of co-evolutionary mechanisms and their importance for appropriate conservation of island biodiversity. Further, we provide a detailed description of the phylogeographic structure of these taxa across these islands, which still remain poorly characterized in this respect.

Dataset Information

The phylogeography of the cycad genus Dioon (Zamiaceae) clarifies its Cenozoic expansion and diversification in the Mexican transition zone.

Publications

The phylogeography of the cycad genus Dioon (Zamiaceae) clarifies its Cenozoic expansion and diversification in the Mexican transition zone.

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