Monday, May 5, 2008

On Boundary Crossings In Biology: Red Imported Fire Ant Colony Founding

While thinking of various forms of boundary crossings in biology, i remembered Carl Zimmer's story of marmoset chimeras inseminating their mates with their brother's sperm..


and that got me thinking of the way Fire Ants found their colonies. Their mom works hard to raise 'em up in a new colony and what do they proceed to do? They go and carry off their sisters in pupa from their mom's home and bring them to another colony, another mom, to help HER raise up more kids, their line dying out if their mom doesn't come along for the ride too and take over eventually.

Actually the story is complicated. We are talking about the Red Imported Fire Ant, Solenopsis invictus. Read all about them in Walter Tschinkel's "
The Fire Ants", which is my source for all of this. A luscious book.

What happens is that freshly inseminated fire ant mothers from dozens of colonies will land higgledy piggledy on a field and then over the next few weeks they'll dig little burrows and start raising kids. The kids then start a seemingly ridiculous free for all, taking the kids from nest to nest back and forth feeling out which nest is going to make it best until only a few robust nests are left with all the kids in them because most become abandoned as the ants bunch up. The ants in these communal nests are not necessarily related, and some of the kid ants are helping to raise families of queen-mothers not related to them, even allowing their own queen-mother and family line to die out.

Then those mothers that still got some spunk to 'em, try to get into these nests too. Eventually only a few robust nests each with one mother laying eggs survives. Daughter ants from MANY of the other mothers may have helped to build up those nests. eventually each nest with one mother comes to be inhabited by HER children only.

This is a curious cooperative phenomenon between perhaps distantly related ants/colonies. A kind of Superduperorganism. A curious way to feel out the landscape and best find the patch of soil that will support a thriving nest in the face of environmental hardships and competition between already mature fire ant colonies, which DON'T cooperate this way...

Unless they happen upon a mutation that makes them go polygyne...

These polygyne S. invicta (which can also mate with the monogyne ones) are complicated. the genetics is complicated, the reproduction is complicated, the interactions with the monogyne S. invicta is complicated, not to mention there is also hybridizing with S. richterii (which also have polygyne forms...) Life is messy indeed. Speciation is messy.

(Not to mention I have EIGHTY MORE PAGES of text on this topic to take notes on.)

The polygynes have unrelated mothers in each nest and the nests spread by budding, a mix of daughters taking a mother with them to found a new nest. Not the usual flight of a single newly mated queen mother to found a nest by herself. The nests remain connected. unrelated workers can move from nest to nest at will. nests will adopt new unrelated mothers... The mothers compete for all the daughters' attentions. the ones that get the most attention will raise up the most new mothers and therefore get to reproduce new nests.

Polygyne colonies spread like amoebas across the landscape. They don't produce as many winged reproductives that travel far. (whereas Monogyne colonies only reproduce by winged reproductives and they spread in a more scattered fashion.) The polygyne population densities become twice as high as monogynes, ant for ant. Twice the ecological impact!

Where is the organism? Where is the superorganism? Where is the superduperorganism? Where is the species?

Boundary mixing!

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