Distribution and status of medicinal leeches (genus Hirudo) in the Western Palaearctic: anthropogenic, ecological, or historical effects?

Abstract

ABSTRACT1. Distribution and status of medicinal leeches were re-considered in the light of the new taxonomy recognizing four Western Palaearctic species: Hirudo medicinalis, Hirudo verbana, Hirudo orientalis and Hirudo troctina.2. Recent records and new data obtained on expeditions to Ukraine, Russia, Azerbaijan, Kazakhstan, Uzbekistan and the Western Balkans were mapped to obtain an up-to-date overview of the distribution.3. Three hypotheses explaining the current ranges of all Hirudo species were tested. The ecological hypothesis, suggesting a strong impact of large-scale environmental factors, received the highest support, while anthropogenic influence was minimal, and no historical patterns of refugia and colonization were detected.4. Mapped localities of all Hirudo species show extensive, belt-shaped ranges extending from east to west. H. medicinalis is distributed from Britain and southern Norway to the southern Urals and probably as far as the Altai Mountains, occupying the deciduous arboreal zone. H. verbana has been recorded from Switzerland and Italy to Turkey and Uzbekistan, which largely corresponds to the Mediterranean and sub-boreal steppe zone. H. orientalis is associated with mountainous areas in the sub-boreal eremial zone and occurs in Transcaucasian countries, Iran and Central Asia. H. troctina has been found in north-western Africa and Spain in the Mediterranean zone.5. Based on the data gathered, and considering real and potential threats, global IUCN category Near Threatened is proposed for H. medicinalis, H. verbana, and H. orientalis, while H. troctina can only be assigned to category Data Deficient.

Occurrence of the medicinal leech (Hirudo medicinalis) in birds’ nests

“…Recently, it was suggested that most likely fast and efficient dispersal of medicinal leeches occurs by their mammalian hosts, for example cattle, as vectors of leech transfer between water reservoirs (Utevsky et al 2010;Trontelj & Utevsky 2012). Our study suggests that birds may play an important role in spreading of medicinal leech.…”

“…Projecting the nesting area of the western marsh harrier over the distribution range of the leech shows that they overlap to a great extent. Such great overlap is not observed for the nesting area of Eurasian coot, mute swan and black-headed gull (Cramp & Simmons 1977;Minelli 2010;Utevsky et al 2010).…”

“…Such possibility has not been taken into account until now. The results of studies by Utevsky et al (2010) and Trontelj & Utevsky (2012) shed light on the cause of the genetic uniformity of medicinal leeches on vast areas, and this phenomenon can be explained by leech parasitism on birds and the dissemination of leeches by their bird hosts. Projecting the nesting area of the western marsh harrier over the distribution range of the leech shows that they overlap to a great extent.…”

The European medicinal leech Hirudo medicinalis L.: Morphology and occurrence of an endangered species

“…Buczyńsky et al (2014) suggest that nests may be important secondary habitats for medicinal leeches, but more observations in aquatic ecosystems, where natural leech populations occur, are necessary to support this hypothesis. These observations indicate that man-made losses of habitat could be also responsible for the demise of some populations of H. medicinalis (Grosser 2004;Elliott and Kutschera 2011;Elliott and Dobson 2014;Utevsky et al 2008Utevsky et al , 2010Kovalenko and Utevsky 2012).…”

“…8A, B). It is now rare throughout Western Europe, and endangered in many countries (Wells and Coombes 1987;Utevsky et al 2008Utevsky et al , 2010Kovalenko and Utevsky 2012;Petrauskiené et al 2011;Westendorff et al 2008;Sawyer 2013aSawyer , 2013bUtevsky 2005, 2012).…”