Cross-taxon Congruence And The Effectiveness Of Indicator Taxa In Nature Reserves Of China

Indicator taxa have been widely used in biological conservation when data on the taxa of conservation interest are lacking.However,many studies that focus on using common taxa(e.g.,vascular plants,birds,reptiles,amphibians and mammals)have found little consistent correlation.It is unclear if this lack of correlation is also applied to other less studied taxa and how sample size and environmental factors may affect between-taxon richness correlation.In this study,I collected data on a wide range of species taxa and environmental factors from 361 nature reserves of China.The taxa include macro-fungi,bryophytes,ferns,gymnosperms,angiosperms,mammals,birds,reptiles,amphibians,insects.The environmental data include longitude,latitude,reserve area,elevation range,the widely used 19 Bioclimatic variables,normalized difference vegetation index,soil PH,soil organic carbon,soil total nitrogen density,field capacity,soil carbon density,soil cation exchange capacity and annual potential evapotranspiration.The objectives of my thesis research are:(1)to model the betweentaxon richness correlations,and identify any possible single indicator taxa in nature reserves of China;(2)to explore the effect of sample size on the between-taxon richness correlation;and(3)to test the competing ecological mechanisms contributing to between-taxon richness correlation.The main results of my study are:(1)The correlations in richness between taxa,except for macrofungi-insects and bryophytes-birds,were significant and positive among all taxonomic groups.There was no single indicator taxon universally predicting species richness of all other taxonomic groups in the reserves of China.(2)The variation in the between-taxon richness correlations was decreased with the increase of the number of sampling reserve,and the statistical power increased with the increase of number of sampling plots.If 0.8 was considered as the conventionally acceptable minimal power for measuring the reliability of the results,it was found that100 reserves were needed to ensure that.(3)The energy hypothesis was found to contribute to between-taxon richness correlation most,while productivity,environmental heterogeneity and climate stability also contributed significantly to between-taxon richness correlation.The reason these hypotheses were important lies in the fact that environmental factors such as the min temperature of the coldest month,annual potential evapotranspiration,precipitation seasonality,elevation range and normalized difference vegetation index commonly underly these hypotheses.In summary,there was no single indicator taxon in nature reserves of China that could indicate the richness of other taxa.Energy input,productivity,habitat heterogeneity and climatic stability significantly contributed to between-taxon richness correlation.In addition,between-taxon richness correlation was affected by the number of sample reserves.This study emphasizes the importance of considering uncommon taxa,numbers of sample reserves,environment factors in the study of between-taxon richness correlation,and suggests 100 reserves(sample size)are needed to reveal possible congruence between-taxon richness.