Isolation and adaptation: Population genetics and morphometric patterns of butterfly <i>Itylos titicaca</i> in the Andean wetlands

Abstract Within the Chilean Altiplano, located at 4000 meters above sea level, we find Itylos titicaca , a small butterfly (10 mm) with low dispersal capacity that inhabits only the Andean wetlands. The extreme climate of this environment, characterized by strong winds, extreme temperature fluctuations and high solar radiation, combined with structural landscape changes (volcanic events, orogenesis, glaciations), can create substantial selective pressures on the flora and fauna of the Altiplano. To characterize and unravel patterns of differentiation in living organisms of the northern region of the Chilean Altiplano, we used I. titicaca as a biological model. Little is known about the life history or ecology of this small butterfly, and this work constitutes the first exploratory study to investigate this species using tools of geometric morphometrics and population genetics. The study was conducted on eight populations of I. titicaca , associated with three Altiplano basins, through the analysis of their wing shape (forewing and hindwing) and the amplification and sequencing of the COI gene. The analysis of genetic structure revealed low diversity, characterized by the presence of a limited number of haplotypes. Nevertheless, three genetic groups were identified within the species' distribution range. Moreover, the morphometric data demonstrate clear variation in the forewing shape among some populations. These findings are associated with the different Altiplano basins and provide evidence of processes such as range expansion and reproductive isolation, driven by the geographic isolation of the Andean wetlands. This study underscores the adaptive capabilities of I. titicaca in extreme and geographically fragmented environments, while emphasizing the importance of conserving these isolated ecosystems that harbor significant biodiversity.