Blastorbis globusmile
As Fungera cirrufractulus grew in population, a new problem started showing up: there's finite algae. And as the population increased, competition first became more likely and then rose dramatically when it was near-inevitable. So how do you stop this? Latch onto a different species, of course. While the fungus latched onto Karpalgearous yellowus no problem without any speciation, another population became speciated from latching onto the species Spheralgearous hostus, which eventually became Fungera globusmile.
So the fungi that latched onto the sphere speciated for one single reason: you can't really hold onto it very well with its original method? While you can do it, it's really hard and you're forced to use the rare disconnected vines. The fungi survived long enough to reproduce a few time, but they didn't really thrive. F. globusmile found a very simple way to fix this though: just hold onto the edges of individual cells rather then the whole vine. They developed a flexible, hook-shaped flagella to do this, and often accidentally pierces its host cell (though this isn't that big of a deal since the flagella block the hole to prevent anything from leaking.)