Taxonomy as a hypothesis: testing the status of the Bermuda buckeye butterfly Junonia coenia bergi (Lepidoptera: Nymphalidae)

Abstract

Species determination and definition in eukaryotes have traditionally been based on morphology, with little focus on genetic differentiation. Molecular methods allow for the independent assessment of morphology‐based taxonomic hypotheses. Three criteria used to define a full species for taxonomic purposes are morphological distinction, formation of a monophyletic lineage, and reproductive isolation. Junonia butterflies (Nymphalidae) are becoming an important experimental model system, but the taxonomy of many New World Junonia species is unclear. One of these species is J. coenia, which contains the subspecies J. coenia coenia, J. coenia grisea and J. coenia bergi. Previous studies suggest that J. coenia grisea may meet the criteria for full species status. Therefore, we evaluated the geographically isolated and rarely studied Bermuda buckeye butterfly J. coenia bergi to determine if it was similarly distinct. Physical examination of specimens and phylogenetic and population genetic analyses of mitochondrial cytochrome c oxidase subunit I, nuclear wingless, and complete mitochondrial genome sequences suggest that while J. coenia bergi is smaller in body size than many Junonia and has distinctive ventral hindwing colouration, it does not form a monophyletic lineage and shows indications of continued gene flow with North American mainland J. coenia coenia populations. Thus, J. coenia bergi does not meet the criteria for full species designation, but geographic isolation, morphological distinctiveness, and cultural importance suggest that it remain recognized as a subspecies of J. coenia. Similar analyses will be useful for addressing further taxonomic questions in Junonia and other taxa, especially where morphology‐based taxonomic determinations are ambiguous.

How old can we go? Evaluating the age limit for effective DNA recovery from historical insect specimens

“…In the New World Junonia , due to retained ancestral polymorphism and/or lateral transfer between species, mitochondrial haplotypes are not species‐specific (Borchers & Marcus, ; Gemmell et al ., ; Gemmell & Marcus, ). However, regardless of species, all of the Junonia from any one locality typically share mitochondrial haplotype frequencies for the two most common haplotype groups (A and B) found in most of the western hemisphere (Pfeiler et al ., ; Gemmell & Marcus, ; Peters & Marcus, ; Lalonde et al ., ; Lalonde & Marcus, ). It is noteworthy that haplotype group A is virtually absent from all species of North American Junonia except in south Florida (Gemmell & Marcus, ; Lalonde et al ., ; Lalonde & Marcus, , b).…”

“…10% of the cost of fluorescent dye‐terminated Sanger DNA sequencing (U.S.$0.83 vs 9.12 per sample at July 2019 prices and currency exchange rates). It should be noted that this new genotyping method does not involve sequencing DNA, but instead assigns mitochondrial genotypes based on the presence or absence of sequence‐ and haplotype‐specific restriction enzyme cut sites in the DNA fragments being evaluated [which were already known for each haplotype based on prior exploratory work that included conventional DNA sequencing (Borchers & Marcus, ; Gemmell et al ., ; Peters & Marcus, ; Lalonde et al ., )]. In our previous work, the fragment‐based genotyping technique worked with 100% efficiency for > 1800 specimens collected in the 20th century and contemporary specimens (1910–2016) from the butterfly genus Junonia (Lepidoptera: Nymphalidae)(Table ), as well as for a handful of 19th‐century specimens, with the oldest genotyped museum specimen dating from 1866 (Lalonde & Marcus, , b).…”

The complete mitochondrial genome of the Madagascar banded commodore butterfly Precis andremiaja (Insecta: Lepidoptera: Nymphalidae)

“…DNA was prepared (McCullagh and Marcus 2015) and sequenced by Illumina MiSeq (San Diego, California) (Peters and Marcus 2017). The mitogenome of P. andremiaja (Genbank MH917706) was assembled and annotated by Geneious 10.1.2 from 9,156,578 paired 300 bp reads using a Junonia lemonias (Lepidoptera: Nymphalidae) reference mitogenome (KP941756).…”

“…We reconstructed a phylogeny using complete mitogenomes from P. andremiaja, 24 representatives from tribe Junonini, and 4 outgroup species from other tribes within subfamily Nymphalinae (McCullagh and Marcus 2015; Peters and Marcus 2016; Peters and Marcus 2017;McCullagh and Marcus 2018). Mitogenome sequences were aligned in CLUSTAL Omega (Sievers et al 2014) and analyzed by parsimony and maximum likelihood (model selected by jModeltest 2.1.7 (Darriba et al 2012) and likelihood ratio test (Huelsenbeck and Rannala 1997)) in PAUP Ã 4.0b8/4.0d78 (Swofford 2002) (Figure 1).…”

The complete mitochondrial genome of the long-horned caddisfly Triaenodes tardus (Insecta: Trichoptera: Leptoceridae)

“…However, caddisflies in family Leptoceridae have morphological adaptations for swimming and species in leptocerid genus Triaenodes are herbivorous (Gall et al 2011). Triaenodes tardus Milne, 1934 is a widespread North American species (NatureServe 2017) whose larvae are found in littoral vegetation in lotic and slowly flowing lentic habitats (Schwiebert 2007 (Peters and Marcus 2017). The mitogenome of T. tardus (Genbank MG201852) was assembled by Geneious 10.1.2 from 8,257,770 paired 75 bp reads using an Anabolia bimaculata (Trichoptera: Limnephilidae) reference mitogenome (MF680449) (Peirson and Marcus 2017).…”