Measures of genetic diversity across populations of the Hawaiian endemic ‘ākala, Rubus hawaiensis (Rosaceae)

Abstract

Rubus hawaiensis (‘ākala), is a raspberry species endemic to the Hawaiian Islands that occursonly at higher elevations (>900 meters). Previous research on R. hawaiensis has focused on the species scale, carrying out phylogenetic research on the origin and hybridization patterns of the species. Little is known about genetic variability and population structure within the species, but it is distributed widely across the archipelago, and therefore likely has variation across the populations, either following geographical separation or environmental disparities. To characterize this variability, populations from Hawai‘i, Maui, and Kaua‘i were sampled and compared based on indices of genetic diversity and distances. Sequence information was gathered using multiplexed ISSR genotyping by sequencing (MIG-seq). Most notably, genetic diversity and distances were greatest among the three islands. There was also variation in the genetic composition of populations within each of the islands, especially on Hawai‘i Island. Physical distance between populations was not corelated with genetic distance as expected. Factors linked to elevation and habitat type seemed to be responsible for the patterns seen in genetic similarities across populations. Results suggest that factors other than distance and isolation impact the divergence among populations. Gene flow between distant populations with similar environmental conditions (soils, rainfall, elevation, etc.) may have been sufficient to maintain their genetic similarities.