Identification “by eye”: integrative character assessment informs regional field identification of greater fritillary butterflies (Nymphalidae: Speyeria)

Abstract

The pronounced morphological variability exhibited by Speyeria butterflies can hinder the identification of these taxa, and thus presents a challenge to their management and conservation. While several studies have documented declines in American populations of Speyeria due to habitat change, the response of Canadian populations of Speyeria to widespread anthropogenic pressures remains poorly understood due to their difficult identification. Here, we assessed the utility of morphological characters recommended in regional field guides for the identification of Speyeria butterflies in Canada, focusing on three morphologically variable subspecies that inhabit boreal forests subject to widespread oil sands extraction: S. aphrodite manitoba, S. atlantis hollandi, and S. hesperis beani. We scored 159 specimens for 11 morphological characters, and complimented this data by sequencing the barcode region of the COI gene for 15 of these specimens. Our results indicate a high level of intraspecific variability in several characters, and the COI gene revealed that initial morphological identifications were incorrect. A further assessment of character reliability identified sets of morphological characters that, in combination with specimen sex and species natural history, improved subspecies identification. Notably, we found that a relatively novel field marker—in vivo eye color—consistently distinguished S. aphrodite manitoba from S. hesperis beani and S. atlantis hollandi. Our results emphasize the importance of using an integrative approach for the accurate identification of morphologically variable species, particularly in situations where molecular methods are not readily available, such as citizen science programs.