Regional Patterns And Mechanisms Of Invertebrate Resting Eggs Biodiversity In Littoral Zone Of The Yellow And Bohai Sea

Global biodiversity is currently under threat from global climate change and anthropogenic disturbances.In order to maintain and protect biodiversity,it is essential to understand the state and processes that shape it.This study focused on two levels of biodiversity-species diversity and genetic diversity,hoping to discover their patterns at the regional scale,as well as preliminarily explore the relationship between diversity and environmental factors.In this study,12 coastal sampling sites and 36 freshwater sampling sites in the Yellow and Bohai Sea were selected for sediment collection.To compare the community composition and structure of resting egg in each city,mitochondrial COI gene was used to identify the species and resting eggs in sediment were counted under optical microscope.To find the influence of latitude and ecological factors on species diversity in all sites,environmental factors were obtained from the online climate databases Bio-ORACLE and Worldclim.These factors,combined with other 8environmental factors measured in the laboratory and field,were used in redundancy analysis and multiple regression analysis.To assess the genetic diversity of the coastal area and freshwater wetlands,DNA were extracted from the resting eggs of Labidocera rotunda and Eurytemora pacifica for coastal area,Neodiaptomus schmackeri and Sinodiaptomus sarsi for freshwater wetlands.Genetic differentiation and haplotype network were conducted to reveal population genetic diversity.Mantel tests were performed to detect whether the genetic structure of these four species was influenced by geographical or environmental distance.The main results were obtained as follows:Copepods overwhelmingly dominated in the invertebrate resting eggs community in coastal zone of the Yellow and Bohai Sea at the regional scale,with over 50% of abundance and richness.Kruskal Wallis test revealed a significant difference among the six communities,and non-metric multidimensional analysis indicated that this difference may be caused by cladocerans community.In the tests of latitudinal gradients of species diversity,no significant linear correlations were found between species richness,abundance,diversity indices and latitude,but evenness declined significantly with latitude.Multiple regression analysis revealed a significant correlation between sea surface temperature and all four species diversity indices,which may indicate that the distribution pattern of resting egg in the coastal area of the Yellow Bohai Sea is consistent with the species-energy hypothesis.Among the six invertebrate resting egg communities in freshwater,cladocerans,rotifers and copepods were evenly distributed in richness,while rotifers were superior in abundance.There were clear differences in the composition and structure among six communities according ro Kruskal Wallis test.Presumably because TJ was much different from other five sites.Unfortunately,we did not find a latitudinal gradient in resting egg species diversity.Instead,water salinity and precipitation were discovered significantly associated with species richness and abundance,respectively.The former may result from the presence of some sample sites with higher salinity,while the latter may be related to the more individual hypothesis.The genetic diversity and population genetic structure of two widespread coastal species in Yellow and Bohai Seas,Labidocera rotunda and Eurytemora pacifica,differed from each other.The genetic diversity of Labidocera rotunda was at a high level,with no geographical pattern and no significant genetic differentiation among six populations.However,its population genetic structure was significantly correlated with the phosphate content.The genetic diversity of Eurytemora pacifica was at a moderate level,with no obvious geographical pattern in the population genetic structure.Some genetic differentiation between populations was observed.Combined with the haplotype network,it is possible that populations in YT and TJ were dispersed to QHD and HLD.No relationship between geographical,environmental distance and genetic distance of resting eggs were detected.The genetic diversity of the two widespread freshwater copepods,Neodiaptomus schmackeri and Sinodiaptomus sarsi,was above the middle level.Analysis of the population genetic structure revealed no clear geographic pattern for either genetic structure.Notably,there was high genetic differentiation and weak gene flow between most freshwater populations,suggesting that although resting eggs of zooplankton were considered to have a strong dispersal ability,the role of founder effects and local adaptation may be much more important in freshwater systems.Above all,the species diversity and genetic diversity of invertebrate resting eggs in littoral zone of Yellow and Bohai Sea were preliminarily discussed in this study.Species diversity were no obvious latitudinal gradient.Sea surface temperatures and water salinity were probably the key factors for promoting the species diversity of coast and freshwater,respectively.Genetic diversity of copepods in both areas was above medium level,and did not have significant geographical pattern.The gene flow of copepods in coast was stronger than that in freshwater where the founder effect and local adaptation were dominant.This results identifyied and quantified the distribution characteristics and driving factors of biodiversity at the regional scale,which will help to explore the responding mechanism of biodiversity to global climate change in the future,and have some implications for management of ecosystem and biodiversity.