An endangered flightless grasshopper with strong genetic structure
maintains population genetic variation despite extensive habitat loss
Abstract
Conservation research is dominated by vertebrate examples but the
shorter generation times and high local population sizes of
invertebrates may lead to different management strategies. Here we
investigate the genetic structure of an endangered flightless
grasshopper, Keyacris scurra, used in classical evolutionary
studies in the 60s. It had a wide distribution across New South Wales
(NSW) and Victoria in pre-European times but has now become threatened
because of land clearing for agriculture. We revisited remnant sites of
K. scurra, with populations now restricted to only one area in
Victoria and a few small patches in NSW and the Australian Capital
Territory (ACT). Using DArTseq to generate SNP markers as well as mtDNA
sequence data, we show that the remaining Victorian populations in an
isolated valley are genetically distinct from the NSW populations and
that all populations are genetically unique, with large FST values up to
0.8. We also find that, with one exception, the NSW/ACT populations
separate genetically into chromosomal races (2n = 15 vs. 2n = 17).
Isolation by distance was detected across both the SNP and mtDNA data
sets, and there was substantial differentiation within chromosomal
races. Genetic diversity as measured by heterozygosity was not
correlated with the size of remaining habitat patches, with high
variation present in some remnant cemetery sites. However, inbreeding
correlated negatively with estimated habitat size at 25-500 m patch
radius. These findings emphasize the importance of small fragments in
conserving genetic variation across the species, and they highlight
populations suitable for future translocations.