| Yellowhorn(Xanthoceras sorbifolium Bunge)is a high valued oil tree species with a range restricted to Northern China.It has been widely used as food and medical products source.However,habitat fragmentation and over-utilization threatening wild yellowhorn populations,which deemed endangered.The species is known for its low yield even under artificial conditions,and is dubbed as the species with "thousands flower but one fruit".To protect the wild populations and improve their survival capacity,this research is conducted based on the foundamental knowledge of conservation biology.Major objects includes:1)predict yellowhorn's distribution over the next 30-50 years using "Species Distribution Models(SDMs)" along with "Gap Analysis",and "Importance-performance Analysis",followed by developing suitable in situ conservation plan of wild populations distributed within the Chinese National Nature Reserves;2)using kinship analysis,a molecular markers-based conservation strategy for the ancient Xanthoceras sorbifolium,to developed a plan for the species' genetic diversity restoration through solving the minimum population size issues;3)develop a high fruit yielding planting spatial arrangement of parents and its pro et contra under open-pollinated production mode following a strategy based on yellowhorn' mating system;and 4)conduct species association analysis to select the positively associate pairwise species combinations of economic values for implementing a "close-to-nature" agroforestry production and conservation framework.The main results are including:To understand the contemporary and anticipated future(future 30-50 years)distribution of Chinese wild yellowhorn and to improve the species' in situ conservation strategy within the network of China's National Nature Reserves(NNRs),we used BiodiversityR to predict the species' distribution utilizing the "always-suitable" map concept.We then delineated the always-suitable distributions with the existing NNRs to identify potential conservation areas using an approach that concurrently considered spatial distribution,gap analysis,the role of climate change,and economic analyses.Seven bioclimatic variable predictors and 12 environmental niche modelling submodels successfully contributed to the final model assembly(AUC=0.916,k=0.398).The species range delineation indicated that 71 of the 427 NNRs were included in the always-suitable area,accounting for 26,007 km2(1.58%)of the species total distribution.This mapping endeavour highlighted the negative impact of climate change with a projected 15%-20%habitat decline and expected species' distribution centers shifting from the country's northwest to the southeast.Our results predict the continuous deterioration of X.sorbifolium because of its existing utilization as an oil source and its increased bioenergy potential.The adoption of a flexible management strategy embracing acceptable trade-offs between conservation and utilization within China's NNRs could effectively alleviate the expected species decline.We developed a molecular markers-based conservation strategy for the endemic endangered Chinese yellowhorn,Xanthoceras sorbifolium.The method utilizes pairwise kinship coefficient,a measure of genetic similarity/dissimilarity,between individuals and contrasts two mating schemes that either avoid "no co-ancestry"or allow "permitted co-ancestry" multiple matings of particular individuals as well as "hybrid:scenario between the two.Selection of mating individuals is focused on maximizing genetic dissimilarity,hence capturing maximum genetic diversity.These approaches were compared on a population of 79 ancient yellowhorn trees scattered across 13 populations Matings were evaluated based on their average pair-wise kinship,effective population size.and average number of alleles/locus.No co-ancestry has been proven to be superior to permitted co-ancestry;however,co-ancestry offered an opportunities for increasing effective population size,a desirable attribute for combating the detrimental effect of genetic drift.The hybrid approach,with reduced number of crosses,produced acceptable condition with maximum genetic diversity and high effective population size and genetic dissimilarity among the produced offspring.The advantages of marker-based genetic estimates are highlighted and discussed.Results are expected to solve the minimum population size issues for future yellowhorn genetic conservation.Compare to other species,yellowhorn has a more complicated mating system which may contribute to the low yield or low survive capacity.A replicated 6×6 complete diallel mating among six fruit shape types of yellowhorn,an andromonoecious plant known for its exceedingly low fruit and seed set,was conducted to investigate the species mating system.This mating design was implemented to investigate the relationship between fruit shape type and fruit yield,finding the most productive fruit shape-type matings,and explore maternal and paternal plants spatial arrangements for yield enhancement.The study confirmed the maternal inheritance of fruit shape type,open-pollination often associated with low fruit production,the presence of high inbreeding depression,and differential yield among fruit shape-type matings and directions and identified specific matings between fruit shape types with increased yield potential for the species' commercial production.A high fruit yield planting spatial arrangement of parents is proposed and its pro el contra under open pollinated production mode were discussed.The results will be used to increase fruit yield within the framework of the species' conservation strategy based on yellowhorn mating systems.We use NMDS ordination that explained by community composition variables and climatic variables for 12 wild yellowhorn communities,the climatic variables most likely to influence the species distribution have been identified and help to explore the wild yellowhorn communities.Next,multiple species association and pairwise species association(x^2.V.AC,PCC,Dice,Jaccard,Ochiai)indexes gave several high valued medicinal use species which reach a significant level.Based on the selected species,we catch up agroforestry for yellowhorn.We believe the species select from wild condition have more adapt capability to climatic and bio-climatic,it's also a way to makes community restoration and re-establishement back to nature(close-to-nature).Which helped to establish yellowhorn ex-situ conservation stratigy based on wild yellowhorn community. |
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