Body size and food plants drive local extinction risk in butterflies

Lepidoptera, butterflies and moths, are significant pollinators and ecosystem health indicators. Therefore, monitoring their diversity, distribution, and extinction risks are of critical importance. We aim to understand the drivers of the local extinction risks of the butterflies in Bangladesh. We conducted a systematic review to extract the diversity, distribution and local extinction risks of the butterflies of Bangladesh, and possible drivers of their extinction, e.g., body size, host plants and nectar plants. We updated the current checklist, which now consists of 463 species. We provided distribution and extinctions risk atlas showing both the diversity and extinction risks were highest in the eastern region of Bangladesh. We tested whether body size and host plants contribute to the local extinction risks of butterflies. We predicted butterflies with larger body size and fewer host plants and nectar plants would be in greater extinction risk. Accordingly, we showed that extinction risk was higher in larger butterflies than smaller butterflies, and in butterflies with a fewer number of host plants and nectar plants than the butterflies with higher number host plants. Our study highlights the contribution of body size and host plants as potential drivers of the local extinction risks of butterflies.

Sustaining biodiversity is a fundamental process to maintain a functional ecosystem. Continuous 46 monitoring of extinction risks and understanding the roles its drivers are essential to conserve 47 species and to maintain ecological balance. 48 The regional distribution of a species is thought to be a combined outcome of colonization and [6-8], which implies that some species may be more prone to extinction than others inherently [9]. 53 However, we know enough to conclude that there is a lack of data on species distributions, 54 abundance and associated ecological factors which strongly affects key biodiversity statistics 55 including determining their extinction risk [10]. 56 Butterflies have been a significant focus for ecologists because of their role as pollinators and 57 ecosystem health indicators [11,12]. Butterflies are a widely distributed insect order that evolved 58 from the early Jurassic period. A total of 180,000 species are distributed worldwide excluding 59 Antarctica [13]. They are found in all global territory and populate in desert land even in tropical 60 forests too [14]. However, many species of this insect group are in risk of extinction because of 61 habitat loss and under the influence of changing climatic condition [15]. Extinction risks of 62 butterflies have been conducted in regional scales as well global scale. Assessing the regional 63 extinction risks and its contributing factors can assist in protecting butterflies in a particular  Here, we aim to annotate the diversity, distribution, and extinction risks of the Bangladeshi 79 butterflies. We systematically search for the publications focusing on the butterflies in Bangladesh 80 and amassed occurrence records from published articles. We updated the checklist of the 81 butterflies of Bangladesh and provided a distribution atlas based on those records. Next, we 82 extracted local extinction risks of the butterflies of Bangladesh from IUCN red list and provided a 83 distribution atlas of the endangered butterflies. We then extracted data body size, larval host plants, 84 and adult nectar plants of the butterflies to understand the contributions of these factors to local 85 extinct risks. We predicted that extinction risks of the butterflies with larger body size, fewer host 86 plants, and fewer nectar plants would be greater than that of butterflies with smaller body size, 87 higher host plants, and nectar plants.

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Ethical statement 90 We collected data from published articles based on our systematic literature search. We did not 91 require ethics approval to conduct the study because we did not collect data on any endangered 92 species and did not conduct fieldwork in national parks or protected areas.  105 studies published between 1971 to 2020, and 7) publications available in full-text. We retrieved 106 the full-text of the articles and selected articles based on the inclusion criteria. Furthermore, we 107 also used full-text for cross-referencing and extracted relevant articles.

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Checklist, geographic coverage, and occurrence data 109 We compiled an updated checklist of the butterflies of Bangladesh by incorporating all the species 110 recorded within the geographical distribution of Bangladesh. We updated the taxonomic status, 111 classifications, and synonyms when applicable by following Smetacek (2017). 112 We classified the geographical distribution of the butterflies of Bangladesh into three levels  Wing size 122 We extracted the wingspan of the butterflies from the published sources (S1). We took the middle 123 value when wing size was provided in a range. All values were recorded in millimeters (mm).

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Values were converted to the millimeter when they were presented in other units. extinction risk with the following categories: least concern, near threatened, vulnerable, and 131 critically endangered. We converted the risk categories to a numeric index from least concern (1) 132 to critically endangered (5).

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To determine if the body size of butterflies was correlated with regional extinction risk, we applied

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Study selection 143 The systematic search returned a total of 92 publications (Fig 1). After an initial review of the titles 144 and abstracts, 18 publications were excluded because they did not meet the selection criteria 145 (studies did not focus on butterflies or conducted outside of the geographical distribution of 146 Bangladesh) (Fig 1). The full text of the 74 publications was obtained and screened for the 147 selection criteria (Fig 1). Of these, 18 publications were excluded because those studies did not 148 provide data for the distribution, wing size, host plants, and food plants of the butterflies of 149 Bangladesh (Fig 1). Finally, 56 publications fulfilled the selection criteria (Fig 1). A full list of all 150 publications included in this study is provided in the supplementary data (Supplementary file S1).  Barisal had the lowest species richness with 64 species (Fig 2). The central region Dhaka held a 167 moderate number of butterflies with 216 species, despite being the most urbanized region of the 168 country (Fig 2). 169 The national IUCN Red List status showed one species (Euploea crameri Moore, 1890) as 170 Critically Endangered (CR) and 112 species as Endangered (EN). The number of Vulnerable (VU), 171 Least Concern (LC), and Data Deficient (DD) species were 81, 94, and 27 respectively.

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Monitoring diversity, abundance, and extinction risks of butterflies in regional scales are essential 186 because of their contributions as pollinators. We updated the checklist of the butterflies of 187 Bangladesh and extracted their distribution records from previously published articles. We showed 188 the diversity of Butterflies is highest in the eastern region of Bangladesh. We tested contributions 189 of the body size and food plants of the butterflies to their extinction risks. We found that larger 190 butterflies are in greater extinction risk than the smaller butterflies. We further showed that 191 extinction risks of butterflies with fewer host and nectar plants are greater than butterflies with 192 higher host and nectar plants. 193 Bangladesh has high Butterflies diversity, despite being a small country. Earlier studies by Larsen,194 (2004) confirmed the presence of 427 Butterflies species in Bangladesh and suggested that the 195 total number of species could be between 500 -550. Since then, the checklist was not updated,  Nieminen (1996) 223 concluded that moth size did not affect the risk of population extinction independently. We showed 224 the larger Bangladeshi butterflies are in greater local extinction risk but it was not statistically 225 significant. Our finding corroborates previous studies.

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The diversity of butterflies, like many other insects, depends on the abundance of food sources and 227 habitats [45,46]. Butterfly larvae feed on host plant leaves and adult butterflies collect nectar from 228 multiple plant sources, therefore higher plant richness promotes greater butterfly diversity [47]. 229 Previous studies showed that larval host plant dynamics are the most important determinant  Understanding the spatial distribution and monitoring regional species diversity regularly is 250 essential to understand the population trends, extinction risks of insects. In this study, we extracted 251 occurrence and distribution data on the butterflies of Bangladesh from published literature, field 252 guides, and our unpublished data. We updated the checklist and atlas of the butterflies of 253 Bangladesh. We analyzed the regional extinction risk of the butterflies and found that butterflies  Conflict of interest: The authors declare no conflict of interest.

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Data accessibility: All data will be uploaded in figshare depository upon acceptance of the paper.