Anchialine species show restricted geographic ranges, high habitat specificity and small population sizes. These factors make them particularly vulnerable to human activities, yet little is known about their ecology and evolutionary history. Munidopsis polymorpha is a decapod endemic to an anchialine cave system of the Corona lava tube in Lanzarote (Canary Islands). The present study, the first genetic survey conducted on this largely unknown species, was designed to characterize its genetic diversity, population structure and recent demographic history using sequence data for the COI gene and eight microsatellite. A single haplotype was identified in the mitochondrial dataset. Nuclear genetic diversity was also low (average= 4.375 ± 1.685). No significant genetic structure was detected between sampling sites and years, either by AMOVA (FST = 0.006, P= 0.110) or Bayesian clustering analysis (K = 1), indicating this species should be treated as a single management unit. Neither did we find evidence for a recent bottleneck event, and estimates of effective population size were extremely low (∼ 50). The lack of population structure, low genetic diversity and extremely low effective population size reinforces the high degree of isolation and endemicity of this species and consequently the need to implement appropriate management actions.

The Canary Islands were settled in the first millennium AD by colonizers likely originating from North Africa. The settlers developed a farming economy with barley as the main crop. Archaeological evidence suggests the islands then remained isolated until European sea-travellers discovered and colonized them during the 14th and 15th centuries. Here we report a population study of ancient DNA from twenty-one archaeobotanical barley grains from Gran Canaria dating from 1050 to 1440 cal AD. The material showed exceptional DNA preservation and genotyping was carried out for 99 single nucleotide markers. In addition 101 extant landrace accessions from the Canary Islands and the western Mediterranean were genotyped. The archaeological material showed high genetic similarity to extant landraces from the Canary Islands. In contrast, accessions from the Canary Islands were highly differentiated from both Iberian and North African mainland barley. Within the Canary Islands, landraces from the easternmost islands were genetically differentiated from landraces from the western islands, corroborating the presence of pre-Hispanic barley cultivation on Lanzarote. The results demonstrate the potential of population genetic analyses of ancient DNA. They support the hypothesis of an original colonization, possibly from present day Morocco, and subsequent isolation of the islands and reveal a farmer fidelity to the local barley that has lasted for centuries.