The two countries became neighbors, once Panama rose from the sea 3 million years ago, creating a a lodgical land bridge for the distribution of species back and forth, and has been so for land animals.
Howler monkeys are found in both countries, as are coatis and have both migrated north.
,
Howler above in Colombia.a Coati, on the grounds of the Panamanian embassy below
But the water parameters are very different.
In rivers like the Rio Negro, amd Orinoco, mineral content is mostly low, with neutral pH 7 down to pH 4 in parts.
Whereas even river in the Darien where I test, mineral content is high, and pH hardly ever drops below 8.
This has lead to some interesting speciation.
Andinoacara coerluleopunctatus and A pulcher (the wild form) are almost indentical superficially, yet have diverged into two species in order to adapt to opposite water parameters.
The gar characin, Ctenolucius hujeta prefers a pH range of 5 to 7, yet I catch its sister species Ctenolucius beani in pH waters of 8.2.
Another water parameter enigma species are from the genus Sturomatichthys, where S. leightoni, usually are found in slightly acidic pH of 6, to 7,
whereas Sturomatichthys panamensis is normally found at an @ pH of 8 or abave.
