Parallel Prairies

Most of Apterra's biomes contain a diverse array of plant species. In any stretch of temperate pseudoforest, there could be canopy-palms, feather-palms, basket-bushes, a variety of shade-tolerant skystalks, small basket-grasses, Exopoa and other small basal grasses, rat-briars, and perhaps the occasional wax-palm. The savannas have a combination of tall grasses, scattered pseudotrees, and ground-covering plants. Of course, species-richness is at its highest in the tropics, where nearly every major and minor plant clade has representatives. Even arctic and desert regions are home to many species of disparate origins, often converging on similar structures to survive similar conditions. Across the planet, the Middle Muricene has become a hotbed of speciation, with tens of thousands of species adapting in new ways with every passing generation, and all of its habitats grow more diverse as time goes on.

All, that is, but the grasslands. Even as far back as 100,000 PA, the split between rat-grassland and woodlouse-grassland was beginning to solidify. On one side, there was a family of fast-growing plants with near-inedible foliage, bountiful seeds, and a mutualistic relationship with granivorous rats. On the other side, lush-looking and calorie-dense, was a group with an even closer tie to a particular clade of isopods. Each was the foundation of its own food web, supporting vastly different faunal communities. While woodlouse-grasslands and rat-grasslands occupy the same climate zones, their characteristic flora don't commingle. Instead, each environment makes life hellish for any species that's specialized to live in the other.

Apterra's largest rat-grassland can be found across the Sub-Abelian interior, everywhere that the sea's humid air doesn't reach. Here, rat-grains reign supreme; over 80% of plant biomass is made of various rat-wheat and rat-corn plants. Prairie rat-grasses are present here as well, though not as dominant as they are on mainland Abeli and Loxodia. This is due to the action of rattalopes, the dominant local herbivores, who prefer the rat-grains over the less-abundant seeds of their family members. By selectively feeding on only a few species, they unknowingly maintain a near-monocrop where a single genus dominates all others. When creating their nightly resting places, though, the rattalopes tend to trample a small patch of grass, allowing different plants to sprout in its place. This is a perfect environment for annual barrel-grasses, which take advantage of the disturbed ground and flourish until the rat-grains regrow. The dry rat-grass stalks are also highly flammable, resulting in regular wildfires that provide further opportunities for the barrels, as well as the occasional smokestalk that seems to pop up out of nowhere just days later. 

Ratweasels prowl low to the ground, staying out of sight below the tall, dense grass. Few birds live here, as their long, narrow beaks are poorly-suited for cracking tough rat-grass seeds. The once-fearsome A. nidivenator, which fed on the helpless young of earlier rat species, has faded into extinction due to the rise of precocial rattalopes and ratweasels. In a few niches, though, avian life does manage to survive. The subterranean kiwis of the Early Muricene have become the genus Subterrapteryx, whose burrows are even larger and more complex than their ancestors'. These are the descendants of A. subterraneus that lived south of the mid-Abelian ridge, having migrated here some 700,000 years ago. Their northern counterparts have not survived to the present day, while Subterrapteryx has expanded across Abeli, Sub-Abeli, and parts of southern Loxodia. Feeding on large, solitary woodlice, their tough bills make them the only animals in the area invulnerable to their prey's long, sharp spines. Isopods like those that Subterrapteryx feeds on are vital to the grassland's survival; there aren't any larger organisms that bother eating rat-grass foliage, so the armored crustaceans are left to clean up the decaying matter from previous growing seasons. 

Across the world, in the middle of Ailuropia stands the largest example of woodlouse-grassland ecology. Amber skystalks and other prairie-specialized forms dominate here; while the area is slightly more diverse than the rat-grassland, this one subfamily contains more than 75% of local plants by mass. Prairie-baskets and various annual barrel-grasses can be found below the two-meter-high skystalks, with sodstalks forming a dense lower layer atop the soil. Plague isopods regularly cut gouges through this lush landscape, as there is much nutrition in every leaf and stem. They are not as big a threat as in the woodlands, though, and a given area will often not see a Plague for many years. Kiwizelles are the dominant large herbivores, weighing around thirty kilos on average (with the exception of the cave kiwizelle, which is about a tenth that size). They travel in herds, cutting and slicing vegetation, which ferments it in the crop to extract as many calories as possible. 

As woodlouse-grassland herbivores are larger than their rodent analogues, predatory kiwis have grown to larger proportions as well. Terror kiwis prowl the open plains, with the largest reaching heights of about a meter and a half but remaining lighter than their kiwizelle prey due to their slim frames. These hunters are solitary except during the breeding season, during which they rejoin the same partner year after year. Chicks are independent after about six weeks, but in some cases they will remain with their parents until the next egg is laid, at which point they are driven out so the parents can focus their energy on their new offspring. Young individuals (and smaller members of the genus) primarily target herbivores of their own size class, as well as insectivores like pillbirds and the skeeter-snapper. During the annual migrations of certain mountain kiwi species, these too may be on the menu while they cross the open plains between their summer and winter habitats.

Overall, these two mutually-isolated ecosystems are at a stalemate. Neither can gain ground due to their vastly different ecologies, and for the time being they remain stable as alternate answers to similar environmental conditions. Nowhere is the contrast starker than in the dry temperate zones of southern Abeli. This is one of the only places in the world where rat-grassland and woodlouse-grassland meet, bordering one another along a wide strip between the continent's two mountain ranges. This is not a smooth transition between biomes as one might see, for instance, between a pseudoforest and a desert. Instead, the boundary is sharp; the two grasses grow directly adjacent to each other but do not mix. Their native animals don't bother crossing either, for their preferred food sources are absent on the other side. The border might move a meter or two each year; rat-grasses are marginally better-adapted for arid conditions, while skystalks handle extreme temperatures more easily, so short-term changes in weather patterns often shift the balance slightly. On the whole, though, no progress is made one way or the other.

This situation cannot last forever. Woodlouse-grasslands and rat-grasslands cannot occupy the same niche in the same place without one overtaking the other eventually. Over the millennia, one will win out. Time will tell which will win the battle in the end, or if an entirely different group of plants will upset the balance in some unexpected way.