Dataset Information

Morphological and Genetic Variation in Monocultures, Forestry Systems and Wild Populations of Agave maximiliana of Western Mexico: Implications for Its Conservation.

ABSTRACT: Forestry systems in Mexico are examples of traditional management of land and biodiversity that integrates the use, conservation and restoration of forest elements. Current in situ management practices of Agave maximiliana in western Mexico include the tolerance of many forest elements, reintroduction of young Agave plants and germination of seeds. More intense forms of management include monocultures, which are agroindustrialized systems developed in more recent times and characterized by the establishment of high densities of A. maximiliana plants in deforested areas and abandoned agricultural lands. We compared monocultures, forestry systems and wild populations (i.e., non/slightly-exploited forests) in order to evaluate whether these practices have had an effect on intraspecific morphological and genetic variation and divergence. We also tested whether divergence has a positive relationship with environmental and geographic distance. We analyzed 16 phenotypic traits in 17 populations of A. maximiliana, and 14 populations were further examined by amplifying 9 SSR loci. We employed multivariate methods and analyses of variance in phenotypic and genetic traits to test whether clusters and the percentage of variation contained in the managed and wild categories can be identified. Tests of isolation by environment (IBE) and distance (IBD) were performed to detect the magnitude of divergence explained by climatic and geographic variables. We found that forestry systems are effective as reservoirs of morphological and genetic diversity, since they maintain levels similar to those of wild populations. Moreover, the monocultures showed similar levels, reflecting their recent emergence. While the species showed high morphological diversity (IMD = 0.638, SE ± 0.07), it had low to intermediate genetic diversity (A = 2.37, H E = 0.418). Similar morphological and genetic divergences were found among populations, but these were not correlated with each other in population pairs. Non-significant morphological differentiation was found among categories. Only IBE was significant in the genetic structure (? = 0.32, p = 0.007), while neither IBE nor IBD was detected in the morphological differentiation. We discuss the implications of these results in the context of the weaknesses and strengths of A. maximiliana in the face of the socio-ecological changes predicted for the study area in the short term.

SUBMITTER: Cabrera-Toledo D

PROVIDER: S-EPMC7313679 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Morphological and Genetic Variation in Monocultures, Forestry Systems and Wild Populations of Agave maximiliana of Western Mexico: Implications for Its Conservation.

Cabrera-Toledo Dánae D Vargas-Ponce Ofelia O Ascencio-Ramírez Sabina S Valadez-Sandoval Luis Mario LM Pérez-Alquicira Jessica J Morales-Saavedra Judith J Huerta-Galván Oassis F OF

Frontiers in plant science 20200617

Forestry systems in Mexico are examples of traditional management of land and biodiversity that integrates the use, conservation and restoration of forest elements. Current in situ management practices of Agave maximiliana in western Mexico include the tolerance of many forest elements, reintroduction of young Agave plants and germination of seeds. More intense forms of management include monocultures, which are agroindustrialized systems developed in more recent times and c ...[more]

PMID: 32625225

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Project description:The agaves are plants of cultural importance which have been used by humans for about 10,000 years and about 40 specific uses. The most culturally and economically important of those uses are for the production of fermented (pulque) and distilled beverages (mescal). Pulque continues to be produced in nearly all of Mexico, and the agaves used for this purpose have shown domestication syndrome. We carry out an ethnobotanical, morphological, and genetic analysis of the traditional varieties of pulque agave used in the production of aguamiel (agave sap) and pulque in the state of Hidalgo. We did semi-structured interviews, free listings, and tours with 11 agave managers. We analyzed morphology and studied genetic diversity and structure using nuclear microsatellites. We found wild-collected, tolerated, transplanted, and cultivated varieties of agave. This comprised 19 traditional varieties of pulque agave, 12 of them in production during the study, which corresponded to the species Agave americana, A. salmiana y A. mapisaga and five intraspecific entities. The varieties were grouped morphologically according to a management gradient; the wild-collected varieties were the smallest, with more lateral teeth and a larger terminal spine. The cultivated varieties clearly exhibited domestication syndrome, with larger plants and smaller dentition. The expected heterozygosity (He) of the varieties ranged from 0.204 to 0.721. Bayesian clustering suggested the existence of three genetic groups, both at the level of traditional varieties of pulque agaves and for management categories, a result that matches multivariate clustering. Pulque producers in the studied localities maintain high agrobiodiversity. The cultivated varieties exhibit domestication syndrome, as has been reported for other species of the genus with the same selection purposes. Our results support the hypothesis of a decrease in genetic diversity in crops compared to wild-growing agaves, which seems to be due to vegetative propagation, among other factors.

Project description:In México, at least 37 Agave species are extracted from wild populations for producing distilled spirits. This activity involves harvesting mature agaves just before producing their inflorescences, which cancels sexual reproduction of plants used. The increasing demand of agaves spirits in national and international markets is determining a strong pressure on wild populations, most of them lacking adequate management. In addition, the dynamics of agave populations may be affected by natural phenomena like oscillation of rainfall regimes, which affects the recruitment of agave seedlings, or the scarcity of pollinators that may affect seed production and general population dynamics. We studied the demography of wild populations of Agave inaequidens to analyze critical conditions for populations recovery, modelling the effects of rainfall trends on the demographic performance of this species, and exploring response of populations to hypothetical extraction regimes and reforestation efforts. Our study was performed in four well-conserved wild populations in Central Western Mexico, each population was sampled in a plot of about one hectare composed by 10 subplots 50 x 5 m (2500 m2). Populations were monitored yearly between 2011 and 2013, measuring plant size, reproductive individuals, and fecundity. Data were analyzed through integral projection models by using the IPMpack for R, to perform prospective analyses. We in addition constructed stochastic models to explore the possible influence of rainfall variation on species demography, using data for the drier and wetter years of the study period. Population growth varied from λ=1.003 to λ=0.899 among populations and years, and exceptionally λ=0.559 after a fire event. Low rainfall decreases λ values, indicating especial limitations to harvesting agaves during dry years whose frequency most probably will increase. In general, extraction rates from 10% to 30% of mature individuals are viable to maintain λ above 1, and these rates may be higher if new plants are introduced in populations. Depending on levels of extraction, our models suggest that it is necessary to carry out actions of reforestation, and in situ management according to the trends found in each site. This is one indispensable condition to maintain λ close to or greater than 1. Sustainable extraction of wild agaves is possible, some communities are already carrying out a repertoire of goods practices in this direction, but together with ecological criteria and good management techniques, strict regulations and social organization are needed to achieve it.

Project description:BackgroundGenetic diversity is fundamental for the survival of species. In particular, in a climate change scenario, it is crucial that populations maintain genetic diversity so they can adapt to novel environmental conditions. Genetic diversity in wild agaves is usually high, with low genetic differentiation among populations, in part maintained by the agave pollinators such as the nectarivorous bats. In cultivated agaves, patterns of genetic diversity vary according to the intensity of use, management, and domestication stage. In Agave tequilana Weber var. azul (A. tequilana thereafter), the plant used for tequila production, clonal propagation has been strongly encouraged. These practices may lead to a reduction in genetic diversity.MethodsWe studied the diversity patterns with genome-wide SNPs, using restriction site associated DNA sequencing in cultivated samples of A. tequilana from three sites of Jalisco, Mexico. For one locality, seeds were collected and germinated in a greenhouse. We compared the genomic diversity, levels of inbreeding, genetic differentiation, and connectivity among studied sites and between adults and juvenile plants.ResultsAgave tequilana presented a genomic diversity of HT = 0.12. The observed heterozygosity was higher than the expected heterozygosity. Adults were more heterozygous than juveniles. This could be a consequence of heterosis or hybrid vigor. We found a shallow genetic structure (average paired FST = 0.0044). In the analysis of recent gene flow, we estimated an average migration rate among the different populations of m = 0.25. In particular, we found a population that was the primary source of gene flow and had greater genomic diversity (HE and HO ), so we propose that this population should continue to be monitored as a potential genetic reservoir.DiscussionOur results may be the consequence of more traditional management in the studied specific region of Jalisco. Also, the exchange of seeds or propagules by producers and the existence of gene flow due to occasional sexual reproduction may play an important role in maintaining diversity in A. tequilana. For populations to resist pests, to continue evolving and reduce their risk of extinction under a climate change scenario, it is necessary to maintain genetic diversity. Under this premise we encourage to continue acting in conservation programs for this species and its pollinators.

Project description:Domestication is a continuous evolutionary process guided by humans. This process leads to divergence in characteristics such as behaviour, morphology or genetics, between wild and managed populations. Agaves have been important resources for Mesoamerican peoples since prehistory. Some species are domesticated and others vary in degree of domestication. Agave inaequidens Koch is used in central Mexico to produce mescal, and a management gradient from gathered wild and silvicultural populations, as well as cultivated plantations, has been documented. Significant morphological differences were reported among wild and managed populations, and a high phenotypic variation in cultivated populations composed of plants from different populations. We evaluated levels of genetic diversity and structure associated with management, hypothesizing that high morphological variation would be accompanied by high genetic diversity in populations with high gene flow and low genetic structure among managed and unmanaged populations. Wild, silvicultural and cultivated populations were studied, collecting tissue of 19-30 plants per population. Through 10 nuclear microsatellite loci, we compared population genetic parameters. We analysed partition of variation associated with management categories to estimate gene flow among populations. Agave inaequidens exhibits high levels of genetic diversity (He = 0.707) and moderate genetic structure (FST = 0.112). No differences were found in levels of genetic diversity among wild (He = 0.704), silviculturally managed (He = 0.733) and cultivated (He = 0.698) populations. Bayesian analysis indicated that five genetic clusters best fit the data, with genetic groups corresponding to habitats where populations grow rather than to management. Migration rates ranged from zero between two populations to markedly high among others (M = 0.73-35.25). Natural mechanisms of gene flow and the dynamic management of agave propagules among populations favour gene flow and the maintenance of high levels of variation within all populations. The slight differentiation associated with management indicates that domestication is in an incipient stage.

Project description:BackgroundInbreeding is among the major concerns in management of local livestock populations. The effective population size of these populations tends to be small, which enhances the risk of fitness reduction and extinction. High-density SNP data make it possible to undertake novel approaches in conservation genetics of endangered breeds and wild populations.A total of 97 representative samples of domestic and wild pig populations from the Iberian Peninsula, subjected to different levels of threat with extinction, were genotyped with a 60 K SNP panel. Data analyses based on: (i) allele frequency differences; (ii) linkage disequilibrium and (iii) runs of homozygosity were integrated to study population relationships, inbreeding and demographic history.ResultsThe domestic pigs analyzed belonged to local Spanish and Portuguese breeds: Iberian ? including the variants Retinto Iberian, Negro Iberian and Manchado de Jabugo ?, Bisaro and Chato Murciano. The population structure and persistence of phase analysis suggested high genetic relations between Iberian variants, with recent crossbreeding of Manchado de Jabugo with other pig populations. Chato Murciano showed a high frequency of long runs of homozygosity indicating recent inbreeding and reflecting the recent bottleneck reported by historical records. The Chato Murciano and the Manchado de Jabugo breeds presented the lowest effective population sizes in accordance with their status of highly inbred breeds. The Iberian wild boar presented a high frequency of short runs of homozygosity indicating past small population size but no signs of recent inbreeding. The Iberian breed showed higher genetic similarities with Iberian wild boar than the other domestic breeds.ConclusionsHigh-density SNP data provided a consistent overview of population structure, demographic history and inbreeding of minority breeds and wild pig populations from the Iberian Peninsula. Despite the very different background of the populations used, we found a good agreement between the different analyses. Our results are also in agreement with historical reports and provide insight in the events that shaped the current genetic variation of pig populations from the Iberian Peninsula. The results exposed will aid to design and implement strategies for the future management of endangered minority pig breeds and wild populations.

Dataset Information

Morphological and Genetic Variation in Monocultures, Forestry Systems and Wild Populations of Agave maximiliana of Western Mexico: Implications for Its Conservation.

Publications

Morphological and Genetic Variation in Monocultures, Forestry Systems and Wild Populations of <i>Agave maximiliana</i> of Western Mexico: Implications for Its Conservation.

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