Local ecological knowledge can provide a unique source of data for conservation, especially in efforts to investigate the status of rare or possibly extinct species, but it is unlikely to remain constant over time. Loss of perspective about past ecological conditions caused by lack of communication between generations may create "shifting baseline syndrome," in which younger generations are less aware of local species diversity or abundance in the recent past. This phenomenon has been widely discussed, but has rarely been examined quantitatively. We present new evidence of shifting baselines in local perception of regional species declines and on the duration of "community memory" of extinct species on the basis of extensive interviews with fishers in communities across the middle-lower Yangtze basin. Many Yangtze species have experienced major declines in recent decades, and the Yangtze River dolphin or baiji (Lipotes vexillifer) and Yangtze paddlefish (Psephurus gladius) may have become extinct during the 21(st) century. Although informants across all age classes were strongly aware of the Yangtze ecosystem's escalating resource depletion and environmental degradation, older informants were more likely to recognize declines in two commercially important fish species, Reeves' shad (Tenualosa reevesii) and Yangtze pufferfish (Takifugu fasciatus), and to have encountered baiji and paddlefish in the past. Age was also a strong predictor of whether informants had even heard of baiji or paddlefish, with younger informants being substantially less likely to recognize either species. A marked decrease in local knowledge about the Yangtze freshwater megafauna matched the time of major population declines of these species from the 1970s onwards, and paddlefish were already unknown to over 70% of all informants below the age of 40 and to those who first started fishing after 1995. This rapid rate of cultural baseline shift suggests that once even megafaunal species cease to be encountered on a fairly regular basis, they are rapidly forgotten by local communities.

Rapidly shifting baselines in Yangtze fishing communities and local memory of extinct species.

Summary A protocol for gynogenesis of P. spathula was developed in order to produce inbred lines and to develop a technique to preserve the endangered Chinese paddlefish (Psephurus gladius). Diploid gynogenesis was induced in P. spathula using ultraviolet (UV)-irradiated Amur sturgeon (Acipenser schrenckii) sperm for 4.5-min, 5-min or 5.5-min and subsequent heat shock treatment. UV irradiation of sperm for 5 min at a UV intensity (254 nm) of 863 l wc m )2 was the optimum dose to achieve diploid gynogenesis on the basis of observations on hatching rate of eggs. Three microsatellite loci were used to monitor exclusive maternal inheritance of gynogenetic progenies. The results showed all maternal genome among offspring with no paternal genome. The cytogenetic analysis showed that meiotic gynogenetic diploids possessed 120 chromosomes in metaphase plates, while haploid control groups N1–3 possessed 60 chromosomes.

Induction of meiotic gynogenesis in paddlefish (Polyodon spathula) and its confirmation using microsatellite markers

We surveyed paddlefish Polyodon spathula from 12 geographic locations encompassing the species' entire range at five polymorphic DNA microsatellite loci. Nearly all pairwise estimates of genetic heterogeneity among geographic samples were significant, as was the overall test of genetic heterogeneity. A test for isolation by distance was not significant. A neighbor-joining phenogram did not reveal any obvious phylogeographic patterns, other than a high degree of distinctiveness of the samples from the Tombigbee River and Grand Lake of the Ozarks and, to a lesser extent, the Mermentau River. The distinctiveness of the Mermentau and especially the Tombigbee River populations is not surprising because they are in different drainages. The distinctiveness of the Grand Lake population is accompanied by reduced heterozygosity, perhaps due to low effective population size or past stocking practices. We interpret the distribution of genetic variation in paddlefish as one of historically high levels of gene...

Rangewide Genetic Structure in Paddlefish Inferred from DNA Microsatellite Loci

The reduction of the size and range of populations, and the destruction of their breeding sites has led to situations in which the existence of a population depends on breeding performed by humans in controlled conditions. Such conservation and restoration work should be based on maintaining the ability of protected populations to adapt to environmental conditions. This ability is determined by genetic variation within populations as well as individual genetic characteristics specific to a given population. Managing and preserving the genetic variation of a conserved population is one of most important factors that determine the success of a conservation program. This paper reviews a method based on DNA microsatellite polymorphism and its associated techniques for detection, management and conservation of genetic variation. It covers the use of this method in detecting and monitoring changes in intrapopulation genetic variability. It also covers the usefulness of this technique in assembling breeding pairs based on their genetic profiles, evaluating genetic differences between populations, optimizing and managing genetic variation resources deposited in banks of cryopreserved gametes, and evaluating the effectiveness of programs for conservation and restoration of species. Finally, suggestions for further development of the method are included.

Techniques based on the polymorphism of microsatellite dna as tools for conservation of endangered populations

Summary When paddlefish, Polyodon spathula, eggs were fertilized with UV irradiated (863 l Wc m )2 ) sperm of Amur sturgeon, Acipenser schrenckii, viable gynogenetic diploid progeny with approximately 120 chromosomes occurred due to spontaneous diploidization of the maternal set of chromosomes (SDM). Distant hybridization of P. spathula eggs by A. schrenckii sperm induced inviable gynogenetic haploid progeny with approximately 60 chromosomes. When eggs gynogenetically activated by heterospecific sperm were heatshocked with 37� C for 2 min at 18 min post-fertilization, a small proportion (7.8%) of viable gynogenetic diploid progeny appeared. The female inheritance of these gynogenetic diploid progeny was verified by chromosome analyses and microsatellite genotyping.

Production of gynogenetic diploid Polyodon spathula using fertilization with irradiated sperm followed by spontaneous diploidization and distant hybridization caused by heat shock

Examining patterns of genetic diversity has become an integral component of many management plans concerning endangered species. Chinese paddlefish (Psephurus gladius Martens), a large-sized freshwater fish, is the only member of the family Polyodontidae present in Asia and in the main stream of the Yangtze river. Since the Gezhouba Dam, which was built in 1981, blocked the channel and prevented sturgeon from swimming into the lower-middle section of the Yangtze river, currently the Chinese paddlefish is found only in the upper main stem of the Yangtze river. Furthermore, in the last two decades, the over-catching, habitat destruction and pollution have caused a rapid reduction of the wild population of Chinese paddlefishes, such that the species is now listed as endangered (Category I of the State Key Protected Wildlife List, in the CR Category of the IUCN and on Appendix II of the CITES; Yue et al. 1998). Multiple factors are implicated in species extinction, including habitat loss, and fragmentation, demographic instability, inbreeding and other genetic factors (Lande 1988). If one of these factors, namely recent changes in genetic diversity, can be tested and perhaps rejected, then research and management can focus on the other extinction mechanisms. Moreover, species endangerment often derives from the erosion of genetic diversity (Chen 1993). The loss of genetic diversity predicts lower individual fitness and lower population adaptability (Lande 1998). Consequently, information on genetic diversity may contribute to a better understanding of the causes of species endangerment and thereby help in the development of management strategies for species conservation. Genetic diversity surveys in endangered populations typically determine the variation currently maintained in the population rather than the magnitude or rate of loss of genetic diversity over time (Matocq et al. 2001). Finding evidence of temporal changes in genetic diversity is challenging. Difficulties include finding appropriate molecular markers, methods of analysis (Luikart et al. 1998) and establishing a baseline or reference point from previous specimens against which to measure change (Taylor et al. 1994). DNA fingerprinting is a good marker system for small populations (Wan et al. 2004) and has revealed the loss of genetic diversity (Wan and Fang 2002, 2003; Wan et al. 2003a), genetic variation between subpopulations (Fang et al. 2002a, 2003), and genetic differentiation of populations (Wan et al. 2003b) of endangered animals. Besides a reliable genetic marker, detecting the loss of genetic diversity also requires archival specimens from which DNA can be obtained. A considerable number of historic samples were preserved by formalin-fixation. The formalin-induced cross-linking between DNA and proteins resulted in the extraction of only fragmented DNA from fixed samples, limiting the use of these archival specimens in conservation genetics (Wan et al. 2004). However, a recent study reported the isolation of high molecular weight DNA from formalin-fixed samples and the successful use of such DNA for fingerprinting studies (Fang et al. 2002b). In this study, we compared genetic diversity of historical collections of Chinese paddlefishes with recent collections, to see whether there has been a loss of genetic diversity in this species as its range and population size

Xue-Chang Wu

Papers

The loss of genetic diversity in the Chinese paddlefish (Psephurus gladius Martens) as revealed by DNA fingerprinting.