· The number of species found in any one habitat varies considerably. Large tracts of boreal forest across North America and Eurasia have only a handful of tree species, while the Amazon basin may house 16,000.
· 单一栖息地发现的物种数量差异巨大。北美和欧亚大陆的大片寒带森林仅有几个树种，而亚马逊盆地却可能有16,000种之多。