Monday, August 9, 2010

Syzygium impressum

Syzygium impressum (Myrtaceae) is a very recently described species which is only valid since 2008. Botanists from IBSC found some questionable specimens of Syzygium buxifolium which consistently differed from the typical one when they were preparing the Flora of Hong Kong. All of those specimens were collected from the Sunset Peak, Hong Kong. This taxon resembles S. buxifolium very much, but could be distinguished by its ovate leaves, impressed midveins and smaller fruits. It was later named as Syzygium impressum which was derived from its conspicuously impressed midveins.

There are nine Syzygium species in Hong Kong whereas identification based on vegetative parts is sometimes difficult. However, not many species have angled young branchlets where S. impressum is one of them (see below):

In addition, by careful assessment and observation, the midveins of it are conspicuously impressed adaxially.

The general apperance of it is indeed like small-leave Ilex species as its crown is very dense. Also, there isn't major habitat overlapping between it and S. buxifolium as the former is solely recorded from streamsides in montane forests but the latter is a very common shrub in lowland forest edge and shrubland.

The recent encounter reminds me that I had seen a very similar one apart from Sunset Peak. Unfortunately I didn't take any specimen or photographs at that time and there is no way to verify unless re-visiting the site. However, woody species is comparatively having lower chance to cause endemism especially in such a tiny place. It is not unexpected to find more populations of this currently-restricted species in other parts of Hong Kong, or even Guangdong. It might probably be overlooked in the past which was confused with S. buxifolium or its allied taxa.

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