, ▁or ▁DNA - based ▁methods , ▁such ▁as ▁mole cular ▁ph y log en et ics ▁and ▁DNA ▁bar c oding . ▁The ▁existence ▁of ▁extremely - similar ▁species ▁may ▁cause ▁local ▁and ▁global ▁species ▁divers ity ▁to ▁be ▁under est im ated . ▁The ▁recognition ▁of ▁similar - but - dist inct ▁species ▁is ▁important ▁for ▁disease ▁and ▁p est ▁control ▁and ▁in ▁conservation ▁bi ology ▁although ▁the ▁drawing ▁of ▁div iding ▁lines ▁between ▁species ▁can ▁be ▁inher ently ▁difficult . ▁ ▁Definition ▁ ▁A ▁species ▁complex ▁is ▁typically ▁considered ▁as ▁a ▁group ▁of ▁close , ▁but ▁distinct ▁species . ▁Obviously , ▁the ▁concept ▁is ▁closely ▁tied ▁to ▁the ▁definition ▁of ▁a ▁species . ▁Modern ▁bi ology ▁understand s ▁a ▁species ▁as ▁" separ ately ▁evol ving ▁met ap op ulation ▁line age " ▁but ▁acknowled ges ▁that ▁the ▁criteria ▁to ▁del imit ▁species ▁may ▁depend ▁on ▁the ▁group ▁studied . ▁Thus , ▁many ▁tradition ally - defined ▁species ▁defined , ▁based ▁only ▁on ▁morph ological ▁similarity , ▁have ▁been ▁found ▁to ▁be ▁several ▁distinct ▁species ▁when ▁other ▁criteria , ▁such ▁as ▁gen etic ▁different iation ▁or ▁re product ive ▁isol ation , ▁are ▁applied . ▁ ▁A ▁more ▁restricted ▁use ▁applies ▁the ▁term ▁to ▁close ▁species ▁between ▁which ▁hy brid isation ▁occurred ▁or ▁is ▁occurr ing , ▁which ▁leads ▁to ▁intermediate ▁forms ▁and ▁bl ur red ▁species ▁boundaries . ▁The ▁inform al ▁classification , ▁su pers pecies , ▁can ▁be ▁exempl ified ▁by ▁the ▁g ri zz led ▁ski pper