[Taxacom] leaving coastal origins

[John Grehan]

Here's a nice example of how ignorance of some basic biogeographic
information is consequential for evolutionary models. In a recent account
of some fossil lampreys the following was stated:

"All the ancient, fishy lamprey larvae were found in saltwater
environments, Miyashita says, from brackish lakes to lagoons to offshore
river deltas. And those are some of the most biologically productive
ecosystems on Earth—think of the massive shrimp industries in the deltas of
the Mississippi or Mekong rivers."

“That’s in stark contrast to modern lampreys,” Miyashita says, most of
which live in freshwater rivers and lakes. “And all species start their
life cycles in a stream.”

"It’s not clear why lampreys would have left the rich coastal water in the
first place."

"Coates also notes that there are a number of “relic” species of fish that
have held on only in rivers and streams, mostly in North America. Bowfin,
alligator gar, and sturgeon are all the last living examples of
once-massive families of fish, which have been pushed from the open ocean
and found a refuge inland. It’s possible that lampreys are part of that
pattern."

All of this reflects a view of evolution that if taxa have a restricted
distribution they are the losers in the evolutionary race and were either
'pushed' out or 'escaped' more advanced forms. This used to be the the
story given for the origin of southern hemisphere taxa (such as marsupials
in Australia). What is clear is that the lamprey people are unaware of  the
simple biogeographic process of tectonic uplift whereby marine and coastal
taxa can be passively transported to higher or inland locations. If this
stranding and ecological change can be accommodated within the adaptive
scope of the organisms they survive. If not they don't. The same thing can
happen with sea regression where coastal taxa are 'stranded' inland
sometimes to become a geographic 'anomaly'.

John Grehan