Phylogenomic Analyses Clarify True Species within the Butterfly Genus Speyeria despite Evidence of a Recent Adaptive Radiation

Abstract

When confronted with an adaptive radiation, considerable evidence is needed to resolve the evolutionary relationships of these closely related lineages. The North American genus Speyeria is one especially challenging radiation of butterflies due to potential signs of incomplete lineage sorting, ongoing hybridization, and similar morphological characters between species. Previous studies have found species to be paraphyletic and have been unable to disentangle taxa, often due to a lack of data and/or incomplete sampling. As a result, Speyeria remains unresolved. To achieve phylogenetic resolution of the genus, we conducted phylogenomic and population genomic analyses of all currently recognized North American Speyeria species, as well as several subspecies, using restriction-site-associated DNA sequencing (RADseq). Together, these analyses confirm the 16 canonical species, and clarify many internal relationships. However, a few relationships within Speyeria were poorly supported depending on the evolutionary model applied. This lack of resolution among certain taxa corroborates Speyeria is experiencing an ongoing adaptive radiation, with incomplete lineage sorting and lack of postzygotic reproductive barriers contributing to hybridization and further ambiguity. Given that many Speyeria taxa are under duress from anthropogenic factors, their legal protection must be viewed cautiously and on a case by case basis in order to properly conserve the diversity being generated.

Genomics and ecological modelling clarify species integrity in a confusing group of butterflies

“…hesperis , despite sampling both species in sympatric parts of their ranges. These results are consistent with other genetic surveys (Campbell et al, 2019; Thompson et al, 2019). Past work has qualitatively noted differences in microhabitat preference between S .…”

Phylogenomics and species delimitation for effective conservation of manta and devil rays

“…Thus, it is also possible that standing genetic variation in ancestral populations may have led to lower levels of lineage sorting in mobulid rays. Similar patterns have been identified across a wide range of taxa (Brawand et al., 2014; Pollard et al., 2006; Suh et al., 2015; Thompson et al., 2019; Wang et al., 2018) and our results highlight how the use of multilocus approaches within a coalescent framework can improve our understanding of the evolutionary processes shaping genomic variation.…”

Reconciling genomic and ecological species delimitation using a confusing group of butterflies

“…Our results consistently show that the northern S. hesperislineage is more genetically similar to S. atlantis than to any genetic clusters within the southern S. hesperis lineage, but we did not recover any evidence of admixture between S. atlantis and northern S. hesperis, despite sampling both species in sympatric portions of their ranges (mostly in Alberta, Canada); these results are consistent with other genetic surveys (Thompson et al 2019;Campbell et al 2019). Past work has noted differences in micro-habitat preference between S. atlantis and S. hesperis in regions where they co-occur (Bird et al 1995;Guppy & Shepard 2001;Dunford 2009;Riva et al 2019), and the results of our ENMs indicate that divergences in habitat associations are likely significant enough to limit gene flow between species, even in sympatric regions.…”

“…hesperis /S. atlantis (de Moya et al 2017;Campbell et al 2017Campbell et al , 2019Thompson et al 2019). It is likely that the recovered polyphyly of S. hesperis and the sister relationship between southern S. hesperis and S. zerenepresented here is partly due to the omission of other Speyeriaspecies in our phylogenetic analyses, but also due to probable introgression between S. hesperis and S. zerene, which is more explicitly indicated by SNP-based admixture and COI haplotype analyses (Fig.…”

“…Some taxonomic treatments have considered S. hesperis to be a subspecies of S. atlantis based on overall morphological similarity (Grey 1951;Miller and Brown 1981;Hammond et al2013). Recent work recognizes these taxa as distinct species, based on assessments of morphological and genetic divergence, as well as an apparent lack of hybridization between sympatric populations (Campbellet al 2017;de Moya et al 2017;Campbell et al2019;Riva et al 2019;Thompson et al 2019). However, the taxa remain difficult to reliably identify using morphology alone (Scott et al 1998;Opler & Warren 2005).…”