doubtful species

基本解释

Taxus L. is a problematic genus, not only its species are discouragingly similar, but also its family circumscription are still doubtful.
紅豆杉種屬的問題，不但它的種類驚人地相似，而且其科的界限也非常模糊。
Given these pressures, and additional ones affecting other animals, it's doubtful that most mammal species will experience much of an overall growth spurt anytime soon.
在這些壓力以及以及其它一些因素的作用下，大多數哺乳動物很難在短時間內出現躰型上的巨大變化。
There are 51 species of the Gasteromycetes, in Shaanxi Province, including 2 doubtful species and 13 new records of Shaanxi Province, belonging to 19 Genus, 9 Families and 6 Orders.
本文報道了産於陝西省的腹菌綱真菌51種，其中包括2個疑難種和13個省內新記錄種，隸屬於6目、9科19屬。