That stem is like no kava I've ever seen. The raised, almost spiky lenticels on them especially on what appears to be a young stem. The petioles/branches being so long and thin for such a small plant. The fact that there appears to be just a single stem.
None of these rules it out completely, but to my eye, it just doesn't look like kava. A botanist or someone who has been exposed to many more cultivars of kava in many different countries will know more and might say I'm wrong about this.
There are between
1000 and 2000 species in the piper family, many of them endemic to Central and South America.