Mauch.indd 207 Jadranka Mauch Lenardić: First record of the root vole Microtus oeconomus (PALLAS, 1776) (Arvicolidae, Rodentia, Mammalia) in Croatia... � AB STRA CT Late Pleistocene remains of Microtus oeconomus (PALLAS, 1776), a species that is not any more a member of the extant fauna of Croatia, have been recently found in Vindija Cave sediments. The sample of 21 teeth shows a slight increase of M1 length and decrease of A/L ratio within the cave sequence from older (G complex; 32 to 42 ka) to- wards younger strata (E+F complex; layer E is dated at ca. 18.5 ka). The most frequent morphotype is type B sensu NADACHOWSKI (1982). The new record does not allow further detailed ecological implications than what is al- ready known about the Late Pleistocene habitats in this region. Keywords: root vole, Microtus oeconomus, teeth, morphometric analyses, Late Pleistocene, Vindija Cave, Croatia First record of the root vole Microtus oeconomus (PALLAS, 1776) (Arvicolidae, Rodentia, Mammalia) in Croatia – fossil remains from the Late Pleistocene of Vindija Cave � Jadranka Mauch Lenardić Institute for Quaternary Palaeontology and Geology, Croatian Academy of Sciences and Arts, Ante Kovačića 5/II, HR–10000 Zagreb, Croatia; (jml@hazu.hr) doi:104154/gc.2011.17 Geologia Croatica 64/3 207–212 5 Figs. 4 Tabs. Zagreb 2011 Geologia CroaticaGeologia Croatica 1. INTRODUCTION Vindija Cave is a well known Pleistocene locality in Croatia. Its Pleistocene sediments (MIS 6 – MIS 2) (Figs. 1 & 2), con- tain numerous small mammal remains and other faunal rep- resentatives. During more than a decade of continuous exca- vations at the site (1974–1986 conducted by Mirko MALEZ), these discoveries were collected with variable care and/or ap- propriate methods (MIRACLE et al., 2010, and references therein). More accurate collecting has been performed during excavation of complex G (32–>42 ka /HIGHAM et al., 2006; WILD et al., 2001/), containing Neanderthal remains and of complex E+F (18.5–30 ka /WILD et al., 2001/), with remains of modern humans (Fig. 2). The majority of the dental and other skeletal microvertebrate remains including Microtus oeconomus (MAUCH LENARDIĆ, 2004, 2005), originates from the sediments of these strata, while one M1 originates from older sediments of the layer I (ca. 88 ka; WILD et al., 2001). Microtus oeconomus is the only extant Microtus species with a holarctic distribution and ranges from northwest Eu- rope, eastward through north and central Asia to Alaska and northwest Canada (BRUNHOFF et al., 2003). Four phylo- geographical groups have been identifi ed and traced back to several glacial periods. They refl ect late glacial and postgla- cial range expansions and shifts as well as fragmentation of populations (idem). 2. GEOLOGICAL SETTINGS The geographic position of the cave is 46° 18’ 12’’ N, 16° 14’ 38’’ E, and the entrance is 275 m a.s.l. (PAUNOVIĆ et al., 2001; WILD et al., 2001, and references therein). The cave consists of a single, funnel-shaped chamber over 50 m long, 28 m wide and 20 m high, although prior to exca vation, the cave roof was less than 3 m above the surface (MIRA- CLE et al., 2010). Geologia Croatica 64/3Geologia Croatica 208 Thirteen layers (from the youngest A /Holocene/ to the oldest M /MIS 6 or older/) show different sedimentation cy- cles, and comprise faunas of different composition. Microtus oeconomus teeth have been uncovered from stratigraphic units I, G lower, G upper (inclusive signature G2), complex E+F and layer E (after original signature; see Fig. 2). 3. MATERIAL AND METHODS The determinations, terminology and metrical methods were used after VAN DER MEULEN (1973), RABEDER (1981) and NADACHOWSKI (1982). Measurements: The overall tooth length (L), the length of anteroconid com- plex (a) and width (W) have been measured and A/L index was calculated (according to VAN DER MEULEN, 1973). All measurements are in millimetres (mm). The parameters have been statistically calculated with STATISTICA 6.0 Figure 1: Location map of Vindija Cave. Figure 2: Stratigraphic column of Vindija Cave sediments with 14C and U/Th data (after WILD et al., 2001). * – data after HIGHAM et al. (2006); ar- rows mark the layers with Microtus oeconomus. Geologia Croatica 209 Jadranka Mauch Lenardić: First record of the root vole Microtus oeconomus (PALLAS, 1776) (Arvicolidae, Rodentia, Mammalia) in Croatia... (StatSoft.Inc., 1994–2001 for Windows). On graphs standard deviation (SD), standard error of the mean (SE) and mean values are indicated. Morphotypes: Morphotypes of M1 have been determined and named after NADACHOWSKI (1982) (Fig. 3). Morphotype B: with pronounced LSA5. Morphotype C: with smooth BSA4 and BRA4 of vary- ing size (example a – lesser distinct, example b – more dis- tinct). Width between T5 and T6 (confl uence) varies. Morphotype D: with BSA4 very well developed, con- nection between T5 and T6 is very narrow (not confl uent). The fossil material is stored at the Institute for Quater- nary Palaeontology and Geology of the Croatian Academy of Sciences and Arts in Zagreb. Abbreviations: Used abbreviations are: sin. (sinister = left), dext. (dexter = right), M1 (fi rst lower molar), M2 (second lower molar), LSA5 (fi fth lingual salient angle), BSA4 (fourth buccal sa- lient angle), BRA4 (fourth buccal re-entrant angle), T5, T6 (fi fth, sixth triangle), ka (thousands of years), n (number of specimens), min. (minimal value), max. (maximal value), MIS (Marine Isotope Stage), LG (Last Glacial). 4. RESULTS Order Rodentia BOWDICH, 1821 Suborder Myomorpha BRANDT, 1855 Superfamily Muroidea, ILLIGER, 1811 Family Cricetidae FISCHER VON WALDHEIM, 1817 Subfamily Arvicolinae GRAY, 1821 Tribe Arvicolini GRAY, 1821 Genus Microtus SCHRANK, 1798 Microtus oeconomus (PALLAS, 1776) 1982 Microtus oeconomus – NADACHOWSKI, p. 74–81, fi gs. 20, 21, 22; Material: 7 M1 sin. (Inv. numbers: 23-1, 32-1, 70-1, 164-1, 202-1, 213-1 and 419-2), 12 M1 dext. (Inv. numbers: 20-1, 39-1, 40-1, 45-1, 50-1, 73-1, 77-1, 160-1, 206-1, 207-1, 45-proba III and 46-proba III), and 2 M2 sin. (Inv. numbers: 23-1 and 70-1). Description: M1 with four, rarely with fi ve closed trian- gles; with weakly developed T6; BSA4 sometimes present; specifi cally shaped anterior cap (lobus) with fl attened buc- cal side. T5 is mostly broadly confl uent with T6 and anterior lobus on the occlusal surface (Fig. 3). Measurements: First lower molars (M1): L, a, W and A/L values are given in Figs. 4 and 5, and Tab. 1. Measured parameters were grouped and compared for two complexes – E+F and G. Mean values for L, a and W are greater for the samples from the E+F complex than for the G complex (Figs. 4 and 5), while for the A/L index is opposite. Figure 3: Morphotypes of Microtus oeconomus fi rst lower molars (M1) from Vindija Cave: B (layer E, Inv. No. 207; inverted image), C (a – layer G2, Inv. No. 70; b – layer I, Inv. No. 419), and D (layer G2, Inv. No. 40; inverted image). Bar scale is 1 mm. Figure 4: Graph of mean values, standard error of the mean values (SE) and standard deviation (SD) for length L (a) and length of anteroconid complex a (b) of Microtus oeconomus M1 for the Vindija Cave E+F and G complexes. Geologia Croatica 64/3Geologia Croatica 210 Second lower molars (M2): Only two M2 (Tab. 2) with values of L and W enable no mor- phometrical analysis. Morphotypes: On 19 M1 of Microtus oeconomus, (12 of them are from the G complex), morphotypes B, C and D sensu NADACHOW- SKI (1982) have been identifi ed (Fig. 3; Tab. 3), while mor- photype A is completely absent. In the small sample, the most abundant morphotype is B (10 teeth or 52.6 %). 5. DISCUSSION Based on M1 morphology alone, a specifi c determination be- tween Microtus oeconomus and Chionomys nivalis might be in some cases problematic, since (as shown by ANGER- MANN, 1971) that both species share common M1 morpho- types. In his paper about Late Quaternary rodents of Poland, NADACHOWSKI (1982) elaborated this problem in fossil material. The „oeconomus« morphotype is the most frequent in the Polish Late Pleistocene samples, but decreases during the Late Glacial. NADACHOWSKI (1982) assumes that at the margin of the species range, non-typical morphological features occur more frequently, which parallels the situation during the last glaciation when under the infl uence of ame- liorating climate the root vole retreat to the north, and the frequency of the „alien« morphotypes increased to 36 %. Also the extreme frequency of the nivalid morphotype (35 %) is observed in recent populations inhabiting the tundra zone (NADACHOWSKI, 1982). The comparison between the frequency of Microtus oeconomus of various Polish sites shows even greater differences (from 2–5 % to 46 %), but up from the Upper Pleniglacial a gradual decrease is ob- served: from 10–30 % in the Upper Pleniglacial, to 4–17 % in the Late Glacial and eventually to 1–8 % during the Ho- locene (NADACHOWSKI, 1982). However, analysing the vole dentition from Bacho Kiro cave (Bulgaria) NADA- CHOWSKI (1984) corrected the previous determination of M1 of Microtus cf. oeconomus to extreme variants (morpho- type A) of the snow vole Chionomys nivalis (MARTINS, Figure 5: Graph of mean values, standard error of the mean values (SE) and standard deviation (SD) for width W (a) and A/L index (b) of Microtus oeconomus M1 for the Vindija Cave E+F and G complexes. Table 1: Minimum (min.), mean and maximum (max.) values of L and A/L for Microtus oeconomus M1 from Vindija Cave. Layer/ complex L A/L n min. mean max. n min. mean max. E 4 2.57 2.69 2.83 4 40.13 48.01 50.18 E+F 2 2.61 2.70 2.78 2 49.64 49.92 50.19 Gupper 10 2.29 2.56 2.76 10 47.16 48.87 52.90 Glower 2 2.57 2.66 2.75 2 49.42 49.99 50.55 I 1 2.94 1 47.96 Table 2: Measurements (L and W) for Microtus oeconomus M2 from Vindija Cave. Inv. no. Layer/complex L W 23-3 (sin.) E+F 1.48 0.87 70-1 (sin.) G2 1.54 0.96 Table 3: Morphotype frequencies for Microtus oeconomus M1 from diff er- ent layers/complexes of Vindija Cave. Layer/ complex MORPHOTYPES B C D TOTAL n % n % n % n % E+F 4 66.7 2 33.3 6 31.6 Gupper 6 60.0 3 30.0 1 10.0 10 52.6 Glower 2 100 2 10.5 I 1 100 1 5.3 TOTAL 10 52.6 8 42.1 1 5.3 19 100 Geologia Croatica 211 Jadranka Mauch Lenardić: First record of the root vole Microtus oeconomus (PALLAS, 1776) (Arvicolidae, Rodentia, Mammalia) in Croatia... 1842) based on data of fossil and recent samples from Swit- zerland, the Tyrol, Murańska cave and other localities in the Tatras, Greece, Romania, Bulgaria etc. In the M1 of Vindija Cave, the most frequent morpho- type is B (52.6 %; four closed triangles), morphotype C is less abundant, morphotype D is represented by one tooth only, and morphotype A is completely lacking. These data would fi t roughly between the values of the Late Glacial and recent condition in Polish samples, documented by NADA- CHOWSKI (1982): Lower Pleniglacial (LP) – 61.7 %, Up- per Pleniglacial (UP) – 60.9 %, Late Glacial (LG) – 46.8 %, recent (R) – 59.2 %. The metrical analysis of M1 of Microtus oeconomus shows an increase of the length and a decrease of the A/L index from the older G to the younger E+F complex. Also NADACHOWSKI (1982) observed a distinctive increase of M1 length during the Late Quaternary of Poland (with the smallest specimens in the Lower Pleniglacial, and the big- gest in the extant fauna – idem). The mean A/L values from Poland fl uctuate between 48 and 49 but the differences be- tween the groups are not statistically signifi cant. In the Vindi ja sample, the maximal values are somewhat smaller, and mini- mal values are slightly bigger compared to the Polish sam- ples, whereas the mean values remain more or less similar. However, L and A/L are smaller in the Croatian samples compared to the Polish ones (Tab. 4) (NADACHOWSKI, 1982; MAUCH LENARDIĆ, 2005). Comparison of M1 length gives similar mean values for the Vindija E+F com- plex sample and recent German specimens (Tab. 4; TAST, 1982). According to SPITZENBERGER & BAUER (2001), a morphological rather similar ancestor of Microtus oeconomus fi rst appeared in the Lower Pleistocene, and specimens of the present shape during the Middle Pleistocene respectively. They quote the oldest ‘true’ M. oeconomus as being from the volcanic ash in the open-site Miesenheim near Koblenz (Rheinland-Pfalz, Germany), dated at 612 ka. Microtus oeconomus belongs to the Holarctic Pleistocene tundra- steppe fauna, which existed during the LG (more than 55 ka), and therefore also occurred on the North American con- tinent. The species also occurs in some Late Pleistocene Aus- trian localities (Gamssultzenhöhle, Grossen Ofenberger- höhle: Upper Würmian, Nixloch: Dryas – 10.55 ka until Holocene) (SPITZENBERGER & BAUER, 2001). Within the Late Pleistocene and Holocene, several populations west and south of the recent main distribution of M. oeconomus became isolated. In southern Germany, the Czech Republic and Hungary, the species was still recorded in the Holocene, in Moldova until the Neolithic, and in southern France, as the last boreal element of Ice Age fauna, the species disap- peared ca. 7000 years ago (SPITZENBERGER & BAUER, 2001). Recent investigations in Hungary have confi rmed the presence of some isolated (sub)populations, one near Bala- ton lake (NE), and a second (Barcs), about 100 km east of the Vindija site (BIHARI et al., 2007). The distribution is confi rmed by NADACHOWSKI (1982) who mentions a Late Pleistocene expansion of the range of Microtus oeconomus further west than today: in Central Europe, England, France and Switzerland as well as further south in Hungary and Romania. The species survived here longer than many other tundra adapted species; e.g., in Hungary it still occurred during the Subboreal (Bükk Phase) in the Bükk mountains, and in the caves of the Aggtelek Karst (NADACHOWSKI, 1982). At the beginning of the Holocene, the distribution of this species was divided into two parts: a tundra range and a forest-tundra range of Eu- rope, parts of Asia and North America, with isolated popu- lations in the Netherlands, Austria and the Small Hungarian Lowland (NADACHOWSKI, 1982). Microtus oeconomus is an indicator of a cold climate and tundra-forest environments with abundant water, respec- tively (NADACHOWSKI, 1982). Tundra (root) voles appear to have an extremely wide tolerance to different habitats, but may be locally restricted by competition with other mic- rotines (GUTHRIE, 1968). In some regions, Microtus oe- conomus could be restricted to low wetland communities, unforested areas, wet meadows, around lakes, streams or mar sh es (GUBÁNYI et al., 2007). Microtus oeconomus has been determined for the fi rst time in Croatia in the Late Pleistocene sediments of the Vind- ija Cave (MAUCH LENARDIĆ, 2004, 2005), and it is not part of the extant fauna in the vicinity of the cave (PETROV, 1992). Thus the fi ndings from Vindija Cave imply a some- what colder and more wet climate in this region during some phases of the Late Pleistocene than today. The youngest strata from which this species is determined in Vindija is the E+F complex (layer E is dated as ca. 18.5 ka). There are no records of this species in younger layers, neither are there in the faunal remains from other Croatian localities with con- temporaneous strata, such as Marlera I (southern Istria), the Mu jina pećina cave (middle Dalmatia; MAUCH LEN AR- DIĆ, 2005, 2008) or Vela spila on Korčula island, respecti- vely (MAUCH LENARDIĆ, in press). ACKNOWLEDGEMENT The author is grateful to Drs. Lutz C. MAUL and Nikola TVRTKOVIĆ for their valuable comments and improving the earlier draft of the man- uscript. This study was part of the authors PhD Thesis research and part of the former Institute’s projects by Ministry of Science, Education and Sports of the Republic of Croatia, Project: “Biostratigraphical correlation of Palaeolithic and Mesolithic of Croatia” no. 101711 (from 1997 till 2001), and project “Palaeolithic and Mesolithic of Croatia: settlement of the eastern Adriatic in Pleistocene” no. 0101018 (from 2002 till 2006). Table 4: Tooth length (L) and A/L index for Microtus oeconomus samples: * – Germany (Fürstenwalde near Berlin; TAST, 1982); ** – Poland (diff erent localities; NADACHOWSKI, 1982). 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