Experimental Evolution of Alkaloid Tolerance in Sibling Drosophila Species with Different Degrees of Specialization

PADRÓ, JULIÁN; DE PANIS, DIEGO N.; VRDOLJAK, JUAN; CARMONA, PABLO MILLA; COLINES, BETINA; HASSON, ESTEBAN; SOTO, IGNACIO M.

EVOLUTIONARY BIOLOGY

SPRINGER

Año: 2017

0071-3260

Drosophila buzzatii and Drosophila koepferae are sibling species with marked ecological differences related to their patternsof host exploitation. D. buzzatii is a polyphagous species with a sub-cosmopolitan distribution, while D. koepferae is endemicto the mountain plateaus of the Andes, where it exploits alkaloidiferous columnar cacti as primary hosts. We use experimentalevolution to study the phenotypic response of these cactophilic Drosophila when confronting directional selection to cactuschemical defenses for 20 generations. Flies adapted to cactus diets also experienced higher viability on alkaloid-enrichedmedia, suggesting the selection of adaptive genetic variation for chemical-stress tolerance. The more generalist species D.buzzatii showed a rapid adaptive response to moderate levels of secondary metabolites, whereas the columnar cacti specialistD. koepferae tended to maximize fitness under harder conditions. The evolutionary dynamic of fitness-related traits suggestedthe implication of metabolic efficiency as a key mediator in the adaptive response to chemical stress. Although we found noevidence of adaptation costs accompanying specialization, our results suggest the involvement of compensatory evolution.Overall, our study proposes that differential adaptation to secondary metabolites may contribute to varying degrees of hostspecialization, favoring niche partitioning among these closely related species.