Lepidopteran biodiversity of Ethiopia: current knowledge and future perspectives

Abstract Lepidoptera is the second largest order of insects. Encompassing moths and butterflies, it is regarded as one of the most important components of biodiversity. Here, an updated comprehensive overview of Lepidoptera recorded in Ethiopia is presented, composed of 2,438 taxa in 48 families, of which 664 are endemic. Records were compiled from various literature sources and website databases. Although still being far from complete, this review provides important baseline data for understanding zoogeographic patterns and thus for undertaking effective conservation action. Further research on Ethiopian Lepidoptera is encouraged.


Introduction
Ethiopia is among the largest countries in the African continent, located in the horn of Africa, covering a total area of 1,127,127 km 2 (Gordon and Carillet 2003;EBI 2015;Tesfu et al. 2018). It belongs to the Afro-tropical Region (former Ethiopian Region) and, based on the bioclimatic classification of Burgess et al. (2004), comprises the zones "Sahelian Savanna", "Somalian Xeric Bushland and Shrubland" and "Ethiopian Montane forest and Alpine Moorland" (Hacker 2019). The country's topography is very diverse, with 20 mountains peaks above 4,000 meters. The highest mountain, Ras Dashen, peaks 4,620 m above sea-level, the fourth-highest in Africa, whilst the third-lowest point in Africa, the Danakil Depression, reaches down to 125 m below sea level. The dominating topographic element is the vast and fertile central highland that accounts for 37% of the land area of the country with an average elevation from 1,500 to 2,400 m that deserved the country to be known as 'roof of Africa'. It is the largest block of land above 1,500 m in Africa (Clausnitzer and Dijkstra 2005), dissected by the Great Rift Valley and surrounded by lowlands along the periphery (Gordon and Carillet 2003). The mean annual rainfall ranges from 500 mm to 2,800 mm and the mean annual temperatures range from around 10° to above 30 °C. Because of these diverging abiotic parameters, the country is endowed with an amazingly diversity of plant, animal and microbial organisms (EBI 2015). According to Clausnitzer (2014), the rate of endemism in Ethiopia's flora and fauna is exceptionally high as a result of vast highlands being isolated by the surrounding dry lowlands. Only the most eurytopic and mobile species (usually those of the lowlands) tend to be found in both Ethiopia and the rest of tropical Africa. In the same manner, Kravchenko et al. (2007) stated that the territory of Ethiopia hosts an extraordinarily diverse landscape including high mountains, lowlands, deserts and tropical rain forests that resulted in a hyperdiverse fauna and flora. Likewise, in consequence of its rich biodiversity, Ethiopia is acknowledged as one of the 20-mega-biodiverse countries in the world (Mittermeier et al. 2011;Tesfu et al. 2018).
Lepidoptera represent the second largest insect order, which consists of approximately 140 different families and 160,000 species that have been described and recognised worldwide, so far (Biodiversity Institute of Ontario 2006; Kristensen et al. 2007;Nieukerken et al. 2011). Lepidoptera comprise nearly 17% of all insect species, and some recent estimates suggest that the real number of Lepidoptera species would set up to 500,000 species (Brandao et al. 2009).
The aims of this paper are to give an updated comprehensive presentation of the actual knowledge of Ethiopian Lepidoptera and to provide some estimates for the expected biodiversity of this major insect order in the country.

Materials and methods
The present review is based on all pertinent published scientific papers. In addition, records from up to date and relevant online databases were also included, particularly, records from the Natural History Museum of London website ("NHMUK": Beccaloni et al. 2003), the Barcode of Life Data Systems ("BOLD": Ratnasingham and Hebert 2007), the African moth website (Goff 2008), LepiMap (Navarro 2007), the African Butterfly Database (Sáfián et al. 2009), the Afromoth website (De Prins and De Prins 2019) and the Afrotropical Butterflies and Skippers digital encyclopaedia (Williams 2018). In all cases, records were included only when sample identifica-tions were made at specific (or subspecific) level, and the provenience from Ethiopia was clearly indicated. Data from entomological collections but not publicly accessible were not considered.
We followed the classification system and nomenclature (valid names and synonymies) used in De Prins and De Prins (2019) with some updates coming from more recent publications. For Rhopalocera, the Afrotropical Butterflies and Skippers digital encyclopaedia (Williams 2018) served as reference. These two outstanding references have also represented the fundamental database and resource for our compilation of the lepidopteran fauna of Ethiopia.

Lepidoptera exploration in Ethiopia: from early explorers to present
Many entomologists have contributed to our current knowledge of the Ethiopian Lepidoptera fauna. The following selection provides the most significant contributions made by past pioneers and current explorers.
Johann Christoph Friedrich Klug in 1829 was the first to mention Abyssinia, the former name of Ethiopia, in the description of a new Lepidoptera species, the butterfly Pontia eupompe (Klug, 1829) now Colotis danae ssp. eupompe (Nazari et al. 2011), indicating as locus typicus "in Arabia deserta, in Sinai monte, in Dongala et Habessinia".
From the mid-nineteenth century, additional descriptions came from few authors such as Félix Edouard Guérin-Méneville (1849), Louis Reiche (1850), and Hippolyte Lucas (1852). However, the most significant advance in the nineteenth century was made by the French entomologist Achille Guenée, who published various contributions between 1852 and 1858. He described 31 new species belonging to the Noctuoidea and Geometroidea, based on material collected mainly by Georg Wilhelm Schimper in 1850. In all cases, the locus typicus was indicated as "Abyssinia" (Guénée 1852).
The geometrid genus Prasinocima Warren, 1897 was subject of an extensive review focused on Ethiopian species, based on an investigation carried out in 100 collection localities in the country for more than 15 years, which included an integrative taxonomic analysis based on morphology and DNA barcodes (Hausmann et al. 2016). As a result of this contribution, the species number was raised from eight previously known Ethiopian species to 40, of which 19 were new to science. After the publication, another seven new species for the Ethiopian fauna were described. Authors of the same article estimated the number of Ethiopian geometrids to exceed 700 species once the unidentified material in their hands is examined, which may suggest a more realistic total species number in excess of 1,000 for the whole country.
Another contribution came from the revision that Hacker carried out on the subfamily Nolinae (Nolidae; Hacker et al. 2012;Hacker 2014), where many of the published data concerned sub-Saharan Africa. For Ethiopia, only three species were previously reported. After Hacker's monograph, the number was raised to 61 species, with 27 newly described taxa from Ethiopia. For Kenya, he raised the figure from 12 to 73, a number not far from that of Ethiopia.
Although these are two examples of taxonomically particularly difficult groups, we can assume similar multiplicators for the so called 'Microlepidoptera' resulting in an estimate for the entire order of Lepidoptera in Ethiopia which may exceed 10,000 species, of which a number of species new for science. This estimate is based on, and in concordance with the usual ratio of geometrid species number versus lepidopteran species number of roughly 1:10, and on the usual ratio of the Rhopalocera (400+ species in Ethiopia) versus lepidopteran species number of roughly 1:20, as it results from large museum material (e.g. ZSM) and from various fauna inventories (e.g. Bavaria: Haslberger and Segerer 2016; Europe: Karsholt and Razowski 1996;North America: Hodges et al. 1983). For the moth fauna of Africa, 38,988 species group names of them are listed by Afromoths (2019), of which 5510 (14%) are geometrids. The total number, however, does not include Rhopalocera names, with 4405 species (Williams 2018) and Microlepidoptera taxonomy is underrepresented, hence also here the "10%-rule" for the Geometridae ratio seems to apply, at least roughly.

Data from DNA barcoding
In the framework of the international Barcode of Life initiative, DNA barcodes (658bp 5' COI gene fragment, cf. Hebert et al. 2003) have been assembled for Ethiopian Lepidoptera since 2006 with the aim to establish a national DNA reference library for integrated taxonomic studies. So far, 3160 DNA barcodes have been generated from Ethiopian Lepidoptera (including many Ethiopian type specimens), belonging to 1012 genetic clusters (Barcode Index Numbers, 'BINs') which are a good proxy for real species numbers Hausmann et al. 2013). Most DNA barcodes could be assembled in the Geometridae (2290 barcodes, 571 BINs), Noctuidae (314 barcodes, 165 BINs) and Erebidae (246 barcodes, 143 BINs). Species coverage is particulary good in the smaller families such as the Saturniidae (121 barcodes, 36 BINs) and Sphingidae (70 barcodes, 24 BINs), while it is still being very poor in the 'Microlepidoptera'. All images and most metadata and molecular data are accessible in the public database BOLD (Ratnasingham and Hebert 2007).

Actual constraints and future perspectives of research on Lepidoptera Diversity of Ethiopia
Butterflies and moths are a major component of biodiversity playing a crucial role in the ecosystem as primary consumers, essential part of food-chains and pollinators. However, humans are exerting unprecedented pressures on all of the earth's ecosystems, and such pressures may affect all species (Sanchez-Bayo and Wyckhuyes 2019). Nature conservation strategies have focused most of their attention on the "charismatic megafauna", i.e., on mammals, birds, and other vertebrates. The vast majority of invertebrate speciesalthough accounting for more than 80% of the animal species -are too poorly known to allow an assessment of how they are affected by human activities, and what might be done to mitigate the damage that humans cause. In most cases, the best way that can be done is to conserve their habitats so that most inhabiting species will continue to thrive.
The greatest threats to butterflies and moths are habitat fragmentation and destruction, intensification of agricultural practice with over-use of pesticides and herbicides; climate change mainly affecting endemic species adapted to mountainous habitats, whereas scientific collecting is absolutely negligible (Hausmann 2001; Sanchez-Bayo and Wyckhuyes 2019). In general, human activity is enormously threatening the global diversity of life on the planet. Rough estimates suggest that we are currently undergoing not only unprecedented, but also accelerating rates of species extinction (UNEP 2006; Sanchez-Bayo and Wyckhuyes 2019).
In the same manner, Ethiopia is experiencing major biodiversity loss, mainly related to extensive destruction of habitats, deforestation, land degradation, intensive agricultural expansion, climate change, excessive pesticide and herbicide use, introduction of exotic plant species, among others (EBI 2015; Tesfu et al. 2018). The loss of primary or native forest areas, due to clearcutting and conversion into agroforests, farmland or settlements, are currently the major threat to the Ethiopian biodiversity in general and Lepidoptera in particular.
Despite Ethiopia being known for its rich heritage of biological diversity and many diverse ecosystems, the conservation of its habitats have received scant attention. The system of protected areas so far established includes 21 national parks, four sanctuaries, eight wildlife reserves, 20 controlled hunting areas, six open hunting areas, six community conservation areas and 58 national forest priority areas (Young 2012), covering 14% of the country (EBI 2015). However, most of its biodiversity, including Lepidoptera, is still unexplored because of significant lack of national research capacity. Hence, in parallel to conservation programs and sustainable utilisation of biological resources, efforts for the preparation of a comprehensive bio-inventory should receive highest priority. Such an instrument must be considered an essential baseline for policy makers, planners, donors and researchers working on biodiversity conservation in Ethiopia.
In order to upsurge biodiversity knowledge, capacity building in the area at various levels is needed. Lack of well organised natural history museums, specialists, and scien-tific societies providing support and fostering citizen science, international research networks and projects are among the identified gaps. Currently, most of the type specimens and reference collections are deposited outside the country of origin. In this context, the Nagoya Protocol (UNSG 2010), although intending to strengthen nations to conserve their genetic resources, to some extent could lead to the opposite effect by hampering international collaboration. Joint protocols and agreements between national actors (research institutes, governing agencies, universities, NGO's) and international research bodies should be promoted in a collaborative way, favoring shared, non-commercial biodiversity research. Close collaboration with museums and universities possessing reference collections and skills, designing and organising projects are required to teach and train a generation of highly competent scientists and managers so that collections of Ethiopian insects could be built and properly managed. In absence of these minimum requirements, establishing a national entomological museum/collection could be ineffective in promoting the study and conservation of local biodiversity resources.