生态系统多样性形成的原因可以概况为

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='20835' and id < 1816801 and id<>'1816801' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='20835' and id > 1816801 and id<>'1816801' order by id asc limit 5