Analysis of Genetic Diversity and Relationships of Seven Chinese Indigenous Pig Breeds and Three Exotic Pig Breeds Using the DNA Differential Display Technique

The genetic diversity and relationships of seven Chinese indigenous pig breeds （Meishan, Erhualian, Hezuo, Bamei, Qingping, Tongcheng, and Huainan） and three exotic pig breeds （Large White, Landrace, and Duroc） were analyzed using the DNA differential display technique by means of eight primer combinations. A total of 123 reproducible bands were used to calculate mean Nei＇s gene diversity, and mean Shannon＇s information index for each pig population. Based on these the Nei＇s standard genetic identity and distance were estimated, which was used to construct a dendrogram tree for the 10 pig breeds. The experimental results obtained and the method used in this study for evaluating the genetic diversity and relationships of pigs were also discussed.

Neighborhood diversity structure and neighborhood species richness effects differ across life stages in a subtropical natural secondary forest

Natural secondary forest has a strong capacity to regrow naturally and recover biodiversity rapidly on abandoned lands.However,at the neighborhood scale,which can truly reflect the facilitative or competitive interactions among individual plants,the local diversity spatial structure in secondary forest and the feedback effects of neighborhood diversity on natural regeneration remain unclear,and this may be the key to properly understand the mechanisms of natural secondary forest species diversity recovery.To this end,this study established a dynamic plot in a rehabilitated secondary forest after disturbance and conducted a comprehensive survey of 68,336 individual plants with repeated measurements at 5-year interval to assess the characteristics of neighborhood diversity structure across life history stages and link the neighborhood species richness(NSR)effect translated by species interactions at species diversity structure with individual trees recruitment/mortality in secondary forest regeneration.The results showed that,compared with tropical and temperate natural forests,a higher proportion of diversity accumulators and a lower proportion of repellers in subtropical secondary forests resulted in neighborhood diversity structures characterized by heterospecific or high-diversity patches,which are beneficial to the maintenance or restoration of biodiversity.As an important supplement to the research on the relationship between diversity and productivity,our findings show a positive diversity-survival relationship in subtropical secondary forests.Importantly,we observed that the neighborhood diversity structure exhibited a trend of accumulator-dominated to neutral-dominant changes with life stage from sapling to adult,which,in turn,determined the direction and strength of NSR effects on recruitment/mortality.Specifically,diverse local neighborhoods at a later successional stage characterized with‘neutral’species-species interactions can act as a‘welfare net’by offering favorable microhabitats for the most vulnerable recruitments or saplings,i.e.,the NSR effects that promoted individual recruitment/survival in our study.These results not only enrich our understanding of the biodiversity-productivity-survival relationship but also highlight the importance of retaining latesuccessional species of native trees in intensive forest production or in situ conservation policies.

Plant diversity promotes soil fungal pathogen richness under fertilization in an alpine meadow

Aims The effects of fertilization on fungal plant pathogens in agricultural soils have been studied extensively.However,we know little about how fertilization affects the relative abundance and richness of soil fungal plant pathogens in natural ecosystems,either through altering the soil properties or plant community composition.Methods Here,we used data from a 7-year nitrogen(N)addition experiment in an alpine meadow on the Qinghai-Tibetan Plateau to test how N addition affects the relative abundance and richness of soil fungal plant pathogens,as determined using Miseq sequencing of ITS1 gene biomarkers.We also evaluated the relative importance of changes in soil properties versus plant species diversity under N addition.Important Findings Using general linear model selection and a piecewise structural equation model,we found that N addition increased the relative abundance of soil fungal plant pathogens by significantly altering soil properties.However,higher host plant species richness led to higher soil fungal plant pathogen richness,even after excluding the effects of N addition.We conclude that the relative abundance and richness of soil fungal plant pathogens are regulated by different mechanisms in the alpine meadow.Continuous worldwide N inputs(through both fertilizer use and nitrogen deposition)not only cause species losses via altered plant species interactions,but also produce changes in soil properties that result in more abundant soil fungal plant pathogens.This increase in pathogen relative abundance may seriously threaten ecosystem health,thus interrupting important ecosystem functions and services.

Dominance by an obligate annual affects the morphological characteristics and biomass production of a planted wetland macrophyte community

Aims Biodiversity-ecosystem function experiments can test for causal relationships between planting diversity and community productivity.Planting diversity is routinely introduced as a design element in created wetlands,yet substantive support for the finding that early diversity positively affects ecosystem functioning is lacking for wetlands.We conducted a 2-year diversity-productivity experiment using freshwater wetland mesocosms to investigate community biomass production as affected by planted macrophyte functional richness.Methods A richness gradient of macrophytes in four emergent wetland plant functional groups was established in freshwater mesocosms for two consecutive years.Species-specific aboveground morphological traits of plant size were measured at peak growth in both years;rooting depth was measured for each species in the second year.Aboveground biomass(AGB)and belowground biomass(BGB)were harvested after peak growth in the second year;first year AGB was estimated from morphological traits in constructed regression equations.Net richness effects(i.e.both complementarity effects and selection effects)were calculated using an additive partitioning method.Important Findings Species richness had a positive effect on community AGB relative to monocultures in the first year.In the second year,mean AGB was significantly reduced by competition in the most species-rich mixtures and all mixtures underyielded relative to the average monoculture.Competition for soil resources was weaker belowground,whereby root distribution at depths>20cm was reduced at the highest richness levels but overall BGB production was not affected.Changes in species biomass were strongly reflected by variation in species morphological traits,and species above and belowground performances were highly correlated.The obligate annual(Eleocharis obtusa),a dominant competitor,significantly contributed to the depression of perennial species’growth in the second growing season.To foster primary productivity with macrophyte richness in early successional communities of created wetlands where ruderal strategies are favored and competition may be stronger than species complementarity,unsystematic planting designs such as clustering the same or similar species could provide protection for some individuals.Additionally,engineering design elements fostering spatial or temporal environmental variability(e.g.microtopography)in newly created wetlands helps diversify the responses of wetland macrophyte species to their environment and could allow for greater complementarity in biomass production.

Genotypic diversity of a dominant C_(4) grass across a long-term fire frequency gradient

Aims and Methods Diversity-disturbance research has focused on community diversity,but disturbance frequency could impact diversity within species as well,with important consequences for community diversity and ecosystem function.We examined patterns of genetic diversity of a dominant grass species,Andropogon gerardii,in native North American tallgrass prairie sites located in eastern Kansas that have been subjected to a gradient of fire frequency treatments(burned every 1,2,4 or 20 years)since the 1970s.In addition,we were able to assess the relationships between genetic diversity of A.gerardii,species diversity and productivity across this range of fire frequencies.Important Findings We found no significant relationships between genetic diversity of A.gerardii at the local scale(1 m^(2) plot level)and disturbance frequency(burned 2 to 32 times over a 38-year period).However,at the site level(i.e.across all plots sampled within a site,~100 m^(2))there were differences in genotype richness and composition,as well as genomic dissimilarity among individuals of A.gerardii.Genotype richness was greatest for the site burned at an intermediate(4-year)frequency and lowest for the infrequently(20-year)burned site.In addition,genotypes found in the frequently burned sites were more similar from each other than expected by random chance than those found in the infrequently burned sites.Genotype composition of A.gerardii was not significantly different between the frequently burned sites(annual vs.2 year)but did differ between frequently burned and infrequently burned sites(1 and 2 year vs.4 and 20 year,etc.).Together,these results suggest site-level ecological sorting of genotypes in intact prairie across a broad gradient of disturbance frequencies,likely driven by alterations in environmental conditions.Frequent fire promotes the abundance of dominant grass species,reduces plant community diversity and impacts ecosystem processes such as productivity.Our study suggests that genetic diversity within dominant grass species also may be affected by disturbance frequency,which could have important implications for how species are able to respond to disturbance.