Conservation Biology: Status Quo and Challenges
Conservation genetics deals with the genetic factors that affect extinction risk and genetic management regimes required to minimize these risks. In this review, we introduce the advance from the genetic diversity study and the influence of genetic diversity on ecosystem. Until now, most of conservation genetic studies still adopt selective neutral genetic markers, which generate a large amount of valuable information for conservation theory and practice. Two important implications of conservation genetics are introduced: (1) the identification of individuals, genetic unit or species, which is very important for conservation strategy making and efficiency improving; and (2) cryptic bottleneck caused by reproduction and dispersal limitation, which is often neglected in conservation practice. Generally, neutral genetic markers may not provide enough information for the genetic basis of species adaptation. In recent years, along with the development of genomics, more and more studies begin to investigate the genetic basis of adaptation by using adaptive genetic markers. Limited by lack of the functional gene information, most of these studies adopt the genome scanning approach. The development of landscape genetics promotes the understanding of the neglected relationship between genetic diversity and the landscape heterogeneity. In addition to the genetic diversity study itself, some studies found that plant genetic diversity may influence the ecosystem structure and function. This illustrates that genetic diversity in both endangered species and common species can play an important role to ecosystem integrity and sustainability. Finally, we briefly discuss how to integrate the genetic diversity into conservation practice more effectively. And, we also indicate the gap between Chinese and international advanced studies at the area of conservation genetics.
The commercial production and extensive environmental release of genetically modified (GM) crops have aroused worldwide concerns and debates over the biosafety of these crops. Transgene escape and its potential environmental risks are among the most debated biosafety issues. Transgene(s) can move from a GM crop to its non-GM counterparts and wild relatives via pollen-mediated gene flow, potentially causing various types of environmental problems. Effective biosafety assessment and research can facilitate the safe and sustainable application of GM crops. Following the framework of risk assessment, there are two critical steps for assessing environmental risks caused by transgene escape: (1) to measure frequencies of transgene escape from a GM crop to its non-GM counterpart or wild relative species (including weedy forms) via pollen-mediated gene flow; and (2) to determine the persist and spread of escaped transgene(s) in wild or weedy populations through introgression. The study of hybridization-introgression represents one of the most important and common phenomena in plant evolutionary, the study of which also includes the two important steps: to estimate frequencies of hybridization and to know the introgression of gene(s) in question within or among populations. The evolutionary theory of hybridization-introgression has a very close relationship with research and assessment of transgene escape and its potential environmental risks. The process of hybridization-introgression usually results in speciation, endangered status, extinction, or adaptive evolution of plant species. This is because important effects such as genetic assimilation, demographic swamping, and selective sweeps during the hybridization-introgression process, can considerably affect the evolutionary process of plant populations, into which the incorporation of transgenes may complicate the evolutionary process. If transgenes in question can significantly increase the fitness of individuals, they will quickly spread in the populations through fast introgression and significantly influence population dynamics bring certain evolutionary consequences. Therefore, we recommend applying the evolutionary theory of hybridization-introgression to guide the research and assessment of potential environmental risks caused by transgene escape.
Construction cost is a quantifiable measure of energy demand for biomass production, and reflects specific growth strategies. Low construction cost is hypothesized to give plant invaders a growth advantage through efficient energy utilization. In this study, three invasive alien species (Mikania micrantha, Wedelia trilobata and Ipomoea cairica) and their co-occurring or phylogenetically related native species (Paederia scandens, Wedelia chinensis and Ipomoea pescaprae) in South China were used as materials for comparing leaf construction costs. These three invasive species exhibited lower mass- (CCmass) and area- (CCarea) based leaf construction costs than the corresponding native species had. Taking the three invasive species as a group, the mean leaf CCmass and CCarea of invasive species were 1.17 g glucose/g and 22.34 g glucose/m2, respectively, which were significantly lower than those for the native species (CCmass = 1.32 g glucose/g and CCarea= 36.93 g glucose/m2). The results testified the lower construction costs for invasive species compared with native ones, which might be a potential mechanism for the successful invasion of plants. Further, statistical analysis revealed significant correlations between leaf construction cost and leaf carbon content, nitrogen content and ash content (Ash) in invasive species. It suggested that the lower leaf construction costs of invasive species were partly due to their lower carbon and nitrogen content, and higher Ashrelative to their corresponding native species.
To explore the composition and interannual dynamics of tree seedlings in a broad-leaved Korean pine mixed forest, 600 25 m2 (5 m×5 m) seedling quadrats were set up in a 25-ha plot of the forest in Changbai Mountain. All seedlings in these quadrats were tagged, measured and identified to species. Based on three seedling censuses between 2006 and 2008, we analyzed species composition, spatial distribution, and interannual dynamics of tree seedlings. A total of 21 tree species were recorded in these quadrats, which was consistent with the composition of trees with ≥1 cm diameter at breast height. There was no significant interannual difference on species composition, but great variations among different seedling subplots. There were 11,959 tree seedlings recorded in three censuses, of which Fraxinus mandshurica and Tilia amurensis comprised of 72.75%. The seedling numbers of F. mandshurica, T. amurensis, and Pinus koraiensis varied greatly among three censuses, while the numbers of other species varied little. Recruit seedlings of 15 species were recorded in three censuses, of which 10 species (T. amurensis, F. mandshurica, P. koraiensis and so on) were found every year. The numbers of recruit seedlings showed great interannual variations among different species and quadrats. Compared spatial distribution of tree seedlings with their seeds and large trees, we found that there were significant differences on individual numbers among different species. For T. amurensis, F. mandshurica, Acer mono, and A. pseudo-sieboldianum, their seeds and seedlings could be found in the entire 25-ha plot. For Ulmus japonica and Maackia amurensis, the distributions of their seedlings were inconsistent with their seeds and large trees. For T. mandshuricaand Malus baccata, with fewer seeds, seedlings, and large trees, the distributions of seedlings were consistent with these of their seeds and large trees.
Litter decomposition as one of the important ecosystem functions has strong interactions with ecosystem biodiversity. This is because recycling of nutrients during litter decomposition has major control over the carbon cycle and nutrient availability. Therefore, decomposition is crucial to qualify diversity effects on ecosystem processes. Here, we conducted a litterbag experiment in temperate grassland of Inner Mongolia, China, to examine the effects of altering plant functional group diversity on litter decomposition. We performed three related decomposition experiments within the Inner Mongolia Grassland Removal Experiment (IMGRE), which was established with a manipulated gradient of functional group diversity. (1) The first experiment is a microenvironment experiment, in which litters of Kochia prostrata and Potentilla bifurca were used to examine the decomposition rates of different functional group assemblages. (2) The second experiment is litter quality experiment, which included four species,Leymus chinensis, Stipa grandis, Allium tenuissimum,and Chenopodium aristatum. Different litter combinations of the four species were placed in a homogeneous environment to test the effects of litter composition on the decomposition. (3) The third experiment was a combination of the above two experiments. The single or a combination of plant litter from species rich plots was placed back to its original plots. Our results showed that decomposition rates of both Kochia prostrataand Potentilla bifurca litter increased with the number of functional groups in the decomposing environment in the first experiment. Non-additive patterns of mass loss were observed in the second experiment. A significant negative correlation between carbon content of the litter mixtures and litter mass loss rate, and positive correlations between nitrogen, phosphorus concentrations and litter mass loss rates were observed. When decomposition microenvironment and litter composition were assessed simutanously, no significant correlations were observed between decomposition rates and the number of functional groups or species diversity. However, a positive correlation was found between nitrogen loss and functional groups. Thus, we concluded that litter diversity itself had smaller effects than species identity, and decomposition was less sensitive to changes in plant diversity compared with other ecosystem processes which depend more on vitality of plants. Furthermore, our results have the implication that higher plant species richness allows vegetation to exploit soil resources more efficiently.
Pollinator specificity has traditionally been considered as the main mechanism of reproductive isolation in orchids. Cypripedium smithii and C. tibeticum are two closely related species with similar characters and sympatric distributions. With the knowledge of reproductive biology of C. tibeticum, we studied the reproductive biology of C. smithii and compared the morphological characters between C. tibeticum and C. smithii. The results showed that a series of intermediate types occurred between typical C. smithiiand typical C. tibeticum, indicating that no distinct taxonomic boundary existed between C. tibeticum and C. smithii. Pollination experiment showed that both C. smithii and C. tibeticum were pollinated by bumble queens. The hand-pollination experiments indicated that C. tibeticum and C. smithii were cross-fertilized, so that they could hybridize in the natural conditions and produced transitional types. It is better to combine them as one identical species rather than separate them as two distinct species.
The research in conservation biology started in 1990 and is currently in a stage of rapid development in China. To understand the status quo of conservation biology in China, we used the term “conservation biology” as the keyword to search and collect Chinese and English literatures in conservation biology which were written by Chinese researchers in ISI Web of Knowledge and Chinese Journals Full-Text Database. These publications were analyzed with methods of bibliometrics, on the distribution of the publication year, the author and organization distribution, the journal distribution, the research funds, the research regions and the objects. The results indicate that core research groups working in the field of conservation biology in China have been already formed, although the distribution of research groups was scattered over institutions and universities. Dispersion and concentration coexisted in the journal distribution of Chinese and English publications—a majority of publications was clumped in a small number of journals, while a minority was scattered in a large number of journals. In China, there is only one professional journal publishing papers on conservation biology— Biodiversity Science. Thus it is reasonable to launch an English conservation biology journal in the country. Research funds for conservation biology have a wide array of sources. An important part of the papers in Chinese was supported by the National Natural Science Foundation of China and provincial foundations, while those in English were supported either by National Natural Science Foundation of China or international funds. Field studies in conservation biology were mainly conducted in the regions of high biodiversities in south and southwest China. Plants, mammals and birds were the main objects of those studies. In the studies on single species, 90% were studies on endangered species. Studies on bio-inventory and genetic diversity represented a significant proportion of publications, while little was published about the strategies and practices of conservation.
From September 2006 to December 2007, we surveyed population densities of khulan (Equus hemionus) and goitred gazelle (Gazella subgutturosa sairensis) in the Mt. Kalamaili Ungulate Nature Reserve using the distance sampling method. Total length of the transect lines for investigating khulan was 6,696.4 km, altogether, we recorded 7,758 khulan. Total length of the transect lines for investigating goitred gazelle was 8,428.84 km, and we recorded 8,586 goitred gazelles. We estimated the density and encounter rates of khulan and goitred gazelle with the interactive computer program Distance 5.0. From spring to autumn, the encounter rate (the number of observed individuals/km) of khulan varied between 0.058-0.092 individuals/km, whereas that of goitred gazelle varied between 0.096-0.342 individuals/km. Suitable habitat for khulan in Kalamaili Ungulate Nature Reserve was 5,800 km2, we estimated population densities of khulan as 0.55 ± 0.20 individuals/km 2 in spring, 0.60 ± 0.13 individuals/km 2 in summer, 0.78 ± 0.19 individuals/ km 2 in autumn, and 0.54 ± 0.14 individuals/ km 2 in winter in the survey area, respectively. There were 3,379 khulan in spring, 3,965 khulan in summer, 5,318 khulan in autumn, and 3,829 khulan in winter, respectively. Suitable habitat for goitred gazelle were 10,000 km2in spring and winter, 12,000 km2 in summer, and 15,000 km2in autumn. We estimated the population densities of goitred gazelle as 1.14 ± 0.18 individuals/km 2 in spring, 0.95 ± 0.12 individuals/km 2 in summer, 1.08 ± 0.18 individuals/km 2 in autumn, and 1.54 ± 0.31 individuals/km 2 in winter, respectively. We calculated the numbers of goitred gazelle as 14,286 in spring, 6,628 in summer, 8,337 in autumn, and 19,677 in winter. We gave recommendation of using the survey transects and survey data as baseline data for long-term monitoring on klulan and goitred gazelle in the Mt. Kalamaili Ungulate Nature Reserve.
Animal domestication was one of the major contributory factors of the agricultural revolution during the Neolithic period, which resulted in a shift of paradigm in the contemporary lifestyle of human from hunting to farming. Research on the origin and domestication of animals is helpful not merely to understand the historical as well as societal transformation of human and the process of animal evolution under the influence of artificial selection but also to formulate the strategies for improving breeding varieties and conservation of domestic animals genetic diversity. Thus researches in this domain have received attention for a long time. In recent years, more archeological evidences coupled with recent developments in the molecular genetics approaches have led to a better understanding of the origin and the underlying process of domestication of animals. In this review, we attempt to state the recent progresses in the research methodologies and breakthroughs in molecular understanding of the basic issues related to the origin and subsequent domestication of animals. The first part of the paper deals with the wild ancestors of domestic animals, the sites of origin and time, the founders and the expansion routes. The second part refers to the conditions that had influenced the domestication process, the traits variation and the underlying genetic mechanisms. Finally, several shortcomings of the previous studies have been highlighted and the challenges and strategies for future direction of research have also been discussed.
Ecologists are always perplexed with the question: why do some species become invasive but others not. A number of studies from different aspects have been conducted including the comparison among different species. However, satisfactory explanations for invasion success remain elusive, and the effects of taxonomical relatedness on the comparative studies have been neglected, making the results incomparable. Comparing the invasive species with their congeners or comparing exotic species of varying invasiveness can partially avoid the bias due to taxonomical relatedness and enhance the credibility of the results. Congeneric comparisons have been widely used in the study of invasive species from the families of Asteraceae, Gramineae and Pinaceae, approaching some important issues that are stressed in the invasion biology of these taxa: biological traits, habitat invasibility, invasion prediction and control. Here we review the applications of comparative studies of congeners in invasion ecology, with an emphasis on their importance and recent progress.
Evolution hypothesis predicts that alien species may experience genetic changes in introduced ranges, facilitating adaptation to new habitats and range expansion. Responses to the selection pressures incurred by the novel abiotic and biotic factors in introduced ranges are primary causes for alien species evolution, although other factors such as intra- and inter-specific hybridizations, genetic shifts can also cause evolution. In this paper, we mainly analyze how alien plant species evolutionarily adapt to environmental changes related to different latitudes and altitudes, and to enemy release in introduced ranges. With respect to evolutionary adaptation to abiotic environments, we introduce some important common garden experiments and reciprocal transplant experiments, emphasizing the necessity to integrate the studies on evolution of phenotypic traits with those on neutral molecular makers. With respect to evolutionary adaptation to enemy release, we mainly discuss evolution of increased competitive ability (EICA) hypothesis, the refinement of EICA hypothesis, and their weaknesses in theory and practices. Finally, we introduce the hypothesis of the evolution of nitrogen allocation, which predicts that invasive plants may decrease leaf nitrogen allocations to defenses but increase allocations to photosynthesis in response to enemy release in introduced ranges.
Biodiversity Committee, CAS
Botanical Society of China
Institute of Botany, CAS
Institute of Zoology, CAS
Institute of Microbiology, CAS
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