Taxonomic Diversity And Functional Diversity Of Fishes In Mangrove Areas Of Guangxi

Mangrove are plentiful and widely spread in Guangxi,but the mangrove area and its biodiversity in the non-protected areas are decreasing year by year,and the ecological system structure is changing.Taking the mangrove areas in the nature reserves(Shankou Mangrove National Nature Reserve,Beilunhekou National Nature Reserve,Maowei Bay Mangrove Provincial Nature Reserve)and Nanliujiang River Estuary mangrove area(outside the reserve)as the research areas.The fish list of Guangxi mangrove areas was compiled through sampling and historical data collection,and the fish diversity pattern in the mangrove areas of Guangxi was researched in taxonomic diversity and functional diversity.In addition,taking the mangrove areas of Nanliujiang estuary as an example,the temporal distribution pattern and its driving factors of fish functional diversity based on morphological trait was also analyzed in this study.The main results are as follows:(1)A total of 181 species of fish were recorded in mangrove areas of Guangxi,among which 94 species of fish were recorded in Shankou Mangrove National Nature Reserve,67 species of fish were recorded in Beilunhekou National Nature Reserve,68 species of fish were recorded in Maowei Bay Mangrove Provincial Nature Reserve,45 species of fish were recorded in Nanliujiang River Estuary mangrove area,and fish were dominated by Perciformes in each mangrove area.(2)The results of average taxonomic difference index(Δ~+)and taxonomic difference variation index(Λ~+)in various mangrove areas of Guangxi showed that the average taxonomic difference index(Δ~+)was the lowest(52.58)and the taxonomic difference variation index(Λ~+)was the highest(283.36)in Nanliujiang River Estuary mangrove area.That is,the fish in Nanliujiang River Estuary mangrove area had the closest genetic,the most uneven taxonomic status and the lowest taxonomic diversity.(3)The results of fish functional diversity based on morphological trait in the mangrove areas of Guangxi showed that the Nanliujiang River Estuary mangrove area had the lowest functional richness of fish(14.13),where fish occupied the least functional space and had the lowest functional diversity.Shankou Mangrove National Nature Reserve had the highest functional richness of fish(206.41),where fish occupied the largest functional space and had the highest functional diversity.Spindle type fish caused the difference of fish functional space in mangrove areas of Guangxi to a certain extent.(4)Temporal patterns and driving factors of functional diversity of fish based on morphological trait in the mangrove area of Nanliujiang estuary showed that there was no spatial difference in functional diversity,functional evenness or functional divergence(P>0.05);There were seasonal differences in functional richness(P<0.05)and in functional divergence(P<0.01),but not in functional evenness(P>0.05);The functional richness has no tidal difference in by four seasons(P>0.05),the functional evenness has tidal difference only in autumn(P<0.05),and the functional divergence has tidal difference only in summer(P<0.01).Linear regression revealed that functional richness was significantly correlated with species richness(P<0.01)and raised with greater species richness,whereas functional evenness and functional divergence were not significantly correlated with species richness(P>0.05).Structural equation modeling results showed the primary driving factors of fish functional diversity were species composition(species richness),followed by hydrology factors(tidal range and creek width),and finally water quality factors(salinity,turbidity and DO),where hydrology factors indirectly affect fish functional diversity by affecting fish species richness.