In 1993, three ecologists reported1 that an isolated population of the butterfly Euphydryas editha that inhabited a meadow in Nevada was starting to evolve a preference for laying its eggs on Plantago lanceolata — a non-native plant introduced to the region by cattle ranchers. In a paper in Nature, two of these researchers now show2 that the butterflies became completely dependent on the exotic plant, with adverse consequences.
Originally, E. editha laid its eggs on the native plant Collinsia parviflora, but the longer life span of Plantago enabled larvae to feed on it for longer, increasing larval survival. In the current study, Singer and Parmesan report that all the female butterflies they examined in 2005 preferred to lay their eggs on Plantago (pictured, E. editha resting on Plantago). And by 2007, all the larvae they found in the field were feeding on this non-native plant.
But cattle ranching ceased in 2005, leading to a rapid build-up of grassy vegetation and a decline in the dominance of Plantago. This, in turn, led to the extinction of the isolated E. editha population between 2007 and 2008, probably because the long grasses blocked out sunlight, cooling the warmth-loving larvae. The growth of the grasses quickly abated, but the butterfly population remained extinct until between 2013 and 2014, when E. editha recolonized the field, laying its eggs on Collinsia, and so setting the stage for the process to begin again.
These findings demonstrate how the adaptation of insect populations to human-induced environmental change can render those populations dependent on the continuation of specific human practices — a potentially precarious position, given the rapidity with which such things can change.
Nature 557, 171 (2018)