So we are looking for animals and plants that survive and thrive despite pollution and its correlating side effects (acid rain, low light conditions), thus make it to the Exodus, then survive the various wars (an thus the break down of supporting infrastructure), then somehow survive the Dark Times (a time of starvation and mass extinction), and thus become prominent at Year Zero.
Starting with the questions:
What would survive an eco-disaster? Things that are hardy
What would survive a breakdown of supporting infrastructure? Things that do not require mankind to procreate and survive any condition without support.
What would surive the Dark Times? Something that can run away, breed faster than it is eaten, is imprinted on the human pyschie, or can fight back.
I vould see the following plants surviving:
Tubers - so radishes, turnips, carrots and potatoes would be the go to foods.
Grains - Corn has been around forever, though with the breakdown of modern fertilizers and pesticides - only certain breeds would survive. So that multicolored shriveled up corn you see decorating the thanksgiving table, that is what would be considered a bounty.
Cacti and suculants - they would spread slowly but I have seen cacti growing in Winnipeg, so I can see them slowly appearing across the landscape.
Animal wise I can see the following surviving:
The boar, which you have models of, is an amazing adapting creature.
Rats and mice are an obvious creature that could survive. Lesser considered animals that seem to do well in an urban environments: Raccoons,Squirrels, Skunks, and coyotes would also survive.
Dogs, well they would be both wild and domestic variants (side note: if you ever read the comic Wasteland, there is a collection about the Dog Tribe. Very good stuff.) They would become I think the most common predator and scavenger, a new breed of mutts that would weed out some of those weaknesses we, as humans, have bred in. Closer to Coyote in coloration, size a bit bigger, with the capability to run down prey. Depending on the circumstances they can be used for food.
Cats. People will coddle their pets, cats would be one such pet to probably survive. And while Dogs have reached a certain level of universal domestication, cats are still very independent.
Ground Hogs and gophers, they are able to live most anywhere, though depending on the desperation of those around them, they also could be consumed during the Fall.
Goats, considered one of the best animals for space colonization due to its sturdiness, utility (milk) and willingness to eat nearly anything would probably do well.
Tilapia (as a fish) are very adaptable, they can even breath air should the water become too polluted.
Iguanas I see being frequent in tropical climes, in fact there is an "plague" of iguanas in Key West.
Gators/Crocodiles/Caymans: They live in some of the most fetid waters in the world and thrive. Ambush predators that could easily survive in the back waters and bayous, and the great swamps created by the rising waters.
As mentioned earlier, Wild/Feral Chickens, also are a problem in Key West.
So the above are all good candiates for surviving the Eco-disaster, and the break down of infrastructure.
So from a predator pyramid standpoint
Lakes/Rivers
Talapia>Gators
Tropical
Iguanas> Snakes
Plains
Ground Hogs> Feral Dogs
Mountains and Hills
Feral Goats> Feral Dogs
Forests
Boars> very desperate Feral Dogs
Ruins
Roaches>Rats>Cats
Sorry for the long and rambling post, but I think I communicated what I wanted.
That to exist in numbers in Year Zero, the animal has to survive the destruction of the environment prior to the Exodus, then the devastation and cross-species starvation up to and during the Dark Times, and then finally fit in the predator pyramid.
Of course this is just my opinion, and I am not a scientist by any stretch of the imagination, so take this all with a grain of salt.
A good source of info might be found here - but it hinges on the assumption that man "vanishes" which we know in Wreck-age is not the case:
en.wikipedia.org/wiki/Aftermath:_Population_Zero