Why is there greater diversity of species in lower trophic levels and ecosystem diversity related to species diversity in terms of evolutionary change?
Organisms in that group are highly prolific, they mature relatively faster, Mutate regularly and exhibit extreme biological and physiological resistance.
Hello Rk; As a point of contrast here is a classic citation that may shed some light on your question. https://books.google.com/books?hl=en&lr=&id=pPkSHx79pwoC&oi=fnd&pg=PP9&dq=why+are+large,+fierce+animals+rare&ots=Cz4rtkFzF6&sig=t19Vg24E1gKemd_BxUFmDtw_6Qw