Data from: Comparative genetic structure and demographic history in endemic Galápagos weevils

The challenge of maintaining genetic diversity within populations can be exacerbated for island endemics if they display population dynamics and behavioral attributes that expose them to genetic drift without the benefits of gene-flow. We assess patterns of genetic structure and demographic history in twenty seven populations of nine species of flightless endemic Galápagos weevils from nine of the islands and one winged introduced close relative. Analysis of mitochondrial DNA reveals significant population structure and moderately variable, though demographically stable, populations for lowland endemics (Fst= 0.094 to 0.541; π: 0.014 to 0.042; Mismatch p=0.003 to 0.026 and D (Tajima)=-0.601to1.203), in contrast to signals of past contractions and expansions in highland specialists on two islands (Mismatch p=0.003 to 0.026 and D (Tajima)=-0.601to1.203). We interpret this series of variable and highly structured population groups as a system of long-established independently founded island units, where structuring could be a signal of micro-allopatric differentiation due to patchy host plant distribution and poor dispersal abilities. We suggest that the severe reduction and subsequent increase of suitably moist habitat that accompanied past climatic variation could have contributed to the observed population fluctuations in highland specialists. We propose the future exploration of hybridization between the introduced and highland endemic species on Santa Cruz, especially given the expansion of the introduced species into the highlands, the sensitivity to past climatic variation detected in highland populations and the potentially threatened state of single-island endemics