Final answer:
Several environmental factors can induce solitary species to form massive swarms, including hydrological changes, introduction of new genotypes, catastrophic events like droughts or hurricanes, and the introduction of new species that trigger rapid population expansions.
Step-by-step explanation:
Environmental factors that could lead to the sudden formation of voracious giant swarms in species that are typically solitary include a variety of biotic and abiotic changes. These can be brought about by hydrological changes that modify habitats, the introduction of new genotypes that offer better adaptation to local conditions, as well as changes in climate, such as particularly harsh winter conditions or disease that may affect some populations but not others. It's also important to note that when small, isolated populations face catastrophic events, such as flood, fire, drought, or hurricanes, they can be wiped out, whereas larger populations in more extensive habitats may survive due to having a larger genetic pool that better enables them to recover and recolonize areas post-disaster.
Specifically, the sudden invasion by long-present figs in south Florida was spurred by the arrival of pollinating fig wasps, indicating that the introduction of new species can play a significant role. In addition, the arrival of differently adapted individuals, such as the cold-tolerant European green crab genotypes or the genetically diverse brown anole lizards in Florida, can cause rapid population expansions. Furthermore, selection pressures, such as the scattering of pea seeds by a person, might affect the survival and reproduction by changing the environmental factors they are exposed to. Inter-species interactions and environmental variations play crucial roles in speciation and the adaptation process, eventually leading to the formation of new species or sudden population surges in existing ones.