Which of the following statements are true about the impact of competition and environmental filtering on community structure. A. Competition shapes a species fundamental niche B. Phylogenetic clustering and increased niche overlap occur when environmental filtering dominates C. Phylogenetic overdispersion and decreased niche overlap occurs when competition dominates D. Both competition and environmental filtering shape community structure

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D. Both competition and environmental filtering shape community structure.

Explanation:

Based on competition theory,  two  organisms occupying the same ecological niche can only coexist   provided  there is spatial or conditioning niche partitioning.This  prevent  competitive exclusion , ensuring survival of the two species in their niche. Since the two species developed greater variability in (over-dispersed traits)  to resist the selection  pressure,(competition).Many overdisperesed traits is present in the communities.

  However environmental filtering, is concerned with selection of species with  natural ability or triats to survive in a given communities,Thus if two species of organism  meet the same ecologocal requirements in a community, environmental filtering, fitters them and ensure their survival ahead of others who do not meet the requirements, and could not survive.

Thus the simultaneous operation of theses  two opposing selection pressures, structured communities ensuring coexistence and favoured ability of organism to survive.

i think it’s c but i might be wrong. if i am let me know! have a good rest of your day as well!