A preliminary analysis of the population genetic parameters indicates critically low genetic variation in a threatened killifish ( Anatolichthys transgrediens )

Abstract

Killifishes of the Western Palearctic are a group of secondary freshwater fishes including eight genera and 42 valid species (Freyhof & Yoğurtçuoğlu, 2020). All were widespread along the coastline of the ancient Tethys Sea during the Oligocene-Miocene boundary (Hrbek & Meyer, 2003), and currently inhabit several brackish habitats in the Mediterranean Sea, Red Sea and Persian Gulf, as well as freshwater springs, streams and lakes in Turkey, North Africa and Iran (Freyhof & Yoğurtçuoğlu, 2020;Hrbek & Meyer, 2003). The most diverse and rich fauna of killifishes occurs in Anatolia (Turkey) with several species suffering a high risk of extinction, where one species has even already gone extinct (Freyhof & Yoğurtçuoğlu, 2020). Yet another species at the edge of extinction from Anatolia is Anatolichthys transgrediens (formerly Aphanius transgrediens; see Freyhof & Yoğurtçuoğlu, 2020), which is relatively a small representative of the killifishes (total length usually <5 cm), characterized by fast growth, short life-span (up to 2 years) and long spawning period (Yoǧurtçuoǧlu & Ekmekçi, 2015; Yoǧurtçuoǧlu et al., 2020). The species is ranked among the 100 most endangered species in the world due to its extremely narrow range restricted to only <1 km 2 in the springs and salt marshes of the Lake Acıgöl in Denizli-Afyonkarahisar in southwestern Turkey (Baillie & Butcher, 2012). It has rapidly declined from the early 90s possibly due to the introduction of the Eastern Mosquitofish (Gambusia holbrooki) and other ongoing threats including pollution, climate change and accompanying habitat loss (Freyhof, 2014;Wildekamp et al., 1999;Yoğurtçuoğlu & Ekmekçi, 2014). The most drastic reduction in population size has occurred within the last decade, where it has vanished from nearly 80% of its previously known range (for a detailed account see Wildekamp et al., 1999; Yoǧurtçuoǧlu & Ekmekçi, 2014; Yoǧurtçuoǧlu et al., 2020).Despite the threats sorted above likely playing a role in population declines of the species, no study has quantified the impact each may specifically result in increased population declines and extinction