Abstract
The purpose of this study was to assess the ecological knowledge surrounding the western queen butterfly, Danaus gilippus thersippus (H. Bates). Specifically, our objectives were to synthesize existing data and knowledge on the ecology of the queen and use results of this assessment to inform the direction of future research on this understudied species. We identified six core areas for assessment: distribution, the biodiversity of plant resources, western queen and their host plant phenology, chemical ecology, and four key life history traits. We mapped the distribution of D. g. thersippus from museum specimen records, citizen science (e.g., iNaturalist) and image sharing app-based observations, along with other observational data enumerating all current known plant resources and long-range movements. We assembled 14 larval food plants, six pyrrolizidine alkaloids plants and six nectar plants distributed in the western Mojave and Sonoran Desert regions of the United States and Baja California. We report on its phenology and its long-range movement. Butterfly species have declined across the western US, and western monarch populations have declined by 97%. Danaus g. thersippus has received little research attention compared with its famous congener D. plexippus L. Danaus g. thersippus’ desert distribution may be at its temperature limits for the species distribution and for its rare host plant Asclepias nyctaginifolia.
Highlights
Both rare and common butterfly species in California, United States (US), have declined based on a 35-year dataset of butterfly species due to the compounded effects of habitat alteration [1], increased use of neonicotinoid insecticides [2], and climate change [3,4,5]
24.89% of the data come from museum specimen records and 76.11% come from observation records via iNaturalist (N = 417), BugGuide (N = 45) and Butterflies and Moths of North America (N = 82) and other sources (N = 4)
We assembled the distribution of the queen butterfly Danaus gilippus thersippus in the western
Summary
Both rare and common butterfly species in California, United States (US), have declined based on a 35-year dataset of butterfly species due to the compounded effects of habitat alteration [1], increased use of neonicotinoid insecticides [2], and climate change [3,4,5]. Aridland butterflies may be even more vulnerable as such species and their host plants are often living at the upper limit of their physiological temperature tolerance [6,7]. Aridland butterfly populations near agricultural areas are at risk from all four unique types of risks. Plants are essential to the survival of butterflies. Danaus gilippus thersippus require host plants, which support their growth and larvae (such as milkweeds), as well as nectar plants to satisfy their caloric needs as adults. These plant resources have declined due to land development, Insects 2020, 11, 315; doi:10.3390/insects11050315 www.mdpi.com/journal/insects
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