The promise and challenges of structural variant discovery: A
conservation case study in the critically endangered kākāpō (Strigops
habroptilus)
Abstract
There is growing interest in the role of structural variants (SVs) as
drivers of local adaptation and speciation. From a conservation genomics
perspective, the characterisation of SVs in threatened species provides
an exciting opportunity to complement existing approaches that use
single nucleotide polymorphisms (SNPs) to detect adaptive variation,
identify conservation units, guide pairing decisions and inform
conservation translocations. However, little is known about whole-genome
SV frequency and size distributions, especially for small populations.
To explore the impacts that SV discovery and genotyping strategies may
have on characterisation of SV diversity in non-model organisms, we
explore a near whole-species resequence dataset, and long-read sequence
data for a subset of highly represented individuals in the critically
endangered kākāpō (Strigops habroptilus). We demonstrate that even when
using a highly contiguous reference genome, different discovery and
genotyping strategies can significantly impact the type, size and
location of SVs characterised, which indicates researchers should
exercise caution when drawing conclusions at the individual-scale.
Further, we find that genotyping SVs discovered with long-read data at
the population-scale with short-read data remains challenging. Despite
this, we found that all six strategies used to characterise SVs in
kākāpō reflected similar trends at the population-scale including the
identification of population structure. We are optimistic that increased
accessibility to long-read sequencing and advancements in bioinformatic
approaches (e.g., multi-reference approaches like genome graphs) will
alleviate challenges associated with resolving SV characteristics below
the species level and facilitate the characterisation of population- and
individual-level SVs in threatened species around the globe.