Is the Italian stream frog (Rana italica Dubois, 1987) an opportunistic exploiter of cave twilight zone?

Subterranean Biology, Mar 2018

Studies on frogs exploiting subterranean environments are extremely scarce, as these Amphibians are usually considered accidental in these environments. However, according to recent studies, some anurans actively select subterranean environments on the basis of specific environmental features, and thus are able to inhabit these environments throughout the year. We present the first study on the abundance and spatial use of the Italian stream frog, Rana italica, in subterranean environments. We monthly collected data from 66 cave sectors during a whole year (2013), recording > 120 detections of R. italica. Frogs were more frequently found close to the cave entrance, without significant differences between age classes or sexes. Adults generally were observed being higher up along cave walls compared to juveniles. Frogs abundance was higher in areas showing specific environmental features, such as warm temperature, low incident light and the presence of potential prey. Rana italica likely occupies subterranean areas characterized by a combination of microclimatic suitability and prey availability.

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Is the Italian stream frog (Rana italica Dubois, 1987) an opportunistic exploiter of cave twilight zone?

Subterranean Biology Is the Italian stream frog (Rana italica Dubois, 1987) an opportunistic exploiter of cave twilight zone? Enrico Lunghi 0 Giacomo Bruni Gentile Francesco Ficetola Raoul Manenti 0 Universität Trier Fachbereich VI Raum-und Umweltwissenschaften Biogeographie , Universitätsring 15, 54286 Trier , Germany 2 Museo di Storia Naturale dell'Università di Firenze, Sezione di Zoologia “La Specola” , Via Romana 17, 50125 Firenze , Italy 3 Natural Oasis, Via di Galceti 141, 59100 Prato , Italy 4 Vrije Universiteit Brussel, Boulevard de la Plaine 2, 1050 Ixelles, Bruxelles , Belgium 5 Department of Environmental Science and Policy, Università degli Studi di Milano , Via Celoria 26, 20133 Milano , Italy 6 Univ. Grenoble Alpes, CNRS , Laboratoire d'Écologie Alpine (LECA) , F-38000 Grenoble , France Studies on frogs exploiting subterranean environments are extremely scarce, as these Amphibians are usually considered accidental in these environments. However, according to recent studies, some anurans actively select subterranean environments on the basis of specific environmental features, and thus are able to inhabit these environments throughout the year. We present the first study on the abundance and spatial use of the Italian stream frog, Rana italica, in subterranean environments. We monthly collected data from 66 cave sectors during a whole year (2013), recording > 120 detections of R. italica. Frogs were more frequently found close to the cave entrance, without significant differences between age classes or sexes. Adults generally were observed being higher up along cave walls compared to juveniles. Frogs abundance was higher in areas showing specific environmental features, such as warm temperature, low incident light and the presence of potential prey. Rana italica likely occupies subterranean areas characterized by a combination of microclimatic suitability and prey availability. - Copyright Enrico Lunghi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Introduction Several amphibian species are known to regularly exploit subterranean environments but, besides numerous reports concerning several salamanders species (Niemiller and Miller 2007, Pierce et al. 2014, Manenti et al. 2017, Soares et al. 2017, Vörös et al. 2017) , only a few species of frogs and toads (Anura) are known to exploit these environments (Fenolio et al. 2005, Köhler et al. 2010, Lunghi et al. 2014, Koller 2017) . Frogs have been usually considered as an accidental presence in subterranean environments (Bressi and Dolce 1999) , but recently many authors showed that some Anuran species can be quite common in these sites, selecting caves with specific environmental features (Köhler et al. 2010, Rosa and Penado 2013, Biswas 2014, Lunghi et al. 2014, Matavelli et al. 2015) . One of these species is the Italian stream frog Rana italica Dubois, 1987, which is endemic of Italian Apennines (Lanza et al. 2006, Canestrelli et al. 2008, Buono et al. 2014, Sindaco and Grieco 2014) . According to the known habitat requirements, R. italica is strongly bounded to freshwater environments and usually occurs in forested areas; in some circumstances, the species is also found in natural and artificial subterranean sites, where it seems to be able to breed (Lanza et al. 2006, Vanni and Nistri 2006) . Although most of the previous observations of R. italica refer to individuals trapped in wells and vertical caves (Bressi and Dolce 1999) , recent studies underlined that this frog is able to actively exploit subterranean environments during the whole year (Lunghi et al. 2017) . Subterranean environments are characterized by peculiar microclimatic features: in temperate areas, they generally have a relatively constant temperature, which roughly corresponds to the mean annual temperature at the surface. Furthermore, air humidity is generally very high, and incoming light is only present within the first meters after the cave entrance (Romero 2009, Lunghi et al. 2015) . Close to the surface (cave entrance and twilight zone), the inner microclimate is mostly affected by external environmental conditions, and such peculiarity can promote the abundance of troglophile species (Manenti et al. 2015, Lunghi et al. 2017) . The microclimate characterizing the shallow part of subterranean environments seems to be particularly suitable for Rana italica (Lunghi et al. 2014) ; therefore, the use of subterranean spaces during periods characterized by unsuitable (e.g., dry) surface conditions may be of key importance for population survival (Forrester et al. 2015, Lunghi et al. 2017) . Beside a suitable microclimate, in subterranean environments R. italica probably finds shelter from predators (Vanni and Nistri 2006) . Nevertheless, information on the biology of Italian stream frogs in subterranean environments, and on the relevance of these habitats for its conservation, is extremely limited. With this study we aim to provide the first assessment of R. italica in subterranean environments, mostly focusing on population abundance and habitat use. Methods Data collection From January 2013 to December 2013, we monthly surveyed nine subterranean environments located in the north of Tuscan Apennines (between 43°53'17"N, 11°06'22"E and 44°03'48"N, 10°48'09"E), where the presence of Rana italica was already assessed by a previous study (Lunghi et al. 2014) . All surveyed environments did not show a morphology hampering frogs to move freely between subterranean and outdoor areas. Three of them were World War II refuges, one was a drainage tunnel, while the remaining six were natural caves (Table 1). Subterranean environments were explored until the point in which speleological equipment was necessary, and only when environmental conditions did not pose a risk (e.g., flooding). All studied environments were divided into portions of 3-linear meters of length (hereafter sectors); this subdivision allows a good data collection for both biotic and abiotic features characterizing subterranean environments (Lunghi et al. 2015, Manenti et al. 2015, Lunghi et al. 2017) . Within each sector we recorded air temperature and humidity (measured with a Lafayette TDP92 thermo-hygrometer; accuracy: 0.1 °C and 0.1%) and the average incident light (obtained by averaging max and min illuminance recorded with a Velleman DVM1300 light meter; minimum recordable light: 0.1 lux). We recorded the abundance of Rana italica within sectors using visual encounter surveys (VES; Crump and Scott 1994) and adopting a standardized survey method (7.5 min/sector) which limits potential effects of imperfect species detection (Banks-Leite et al. 2014, Lunghi et al. 2017) . Using the same procedure (VES + standardized survey method), we assessed the presence of seven invertebrate species which potentially represent prey items for R. italica: one dipteran (Limonia nubeculosa Meigen, 1804), three spiders (Meta menardi (Latreille, 1804), Tegenaria Latreille, 1804 sp., Metellina merianae (Scopoli, 1763)), one cricket (Dolichopoda laetitiae Minozzi, 1920) and two gastropods (Chilostoma planospira (Férussac, 1832), Oxychilus draparnaudi (Beck, 1837)). All considered species have stable populations in subterranean environments, even if they are not obligate cave species (Lunghi et al. 2017) . We measured the snoutvent length (SVL) of all captured frogs (Fig. 1a); individuals with SVL ≤ 30 mm were considered juveniles (Buono et al. 2014) . Within adults, we recognized males on the basis of secondary sexual characters (nuptial pads). For each frog, we measured the distance from the cave entrance and the elevation from the cave ground floor. Statistical analyses We used Generalized Linear Mixed Models (GLMM) to assess whether abundance of Rana italica was related to both biotic and abiotic recorded parameters. As dependent variable we used the observed abundance of R. italica, which represents an index of frog abundance (Barke et al. 2017) . Microclimatic features (temperature, humidity and illuminance), biotic features (presence/absence of the seven prey species), month of survey and sector depth were used as independent variables; sector and cave identity were used as random factors. We used Linear Mixed Models (LMM) to identify whether differences in spatial use of caves occur between age classes or sexes. To assess differences between adults and juveniles, we run two LMMs using age class and month of survey as independent variables, while both cave and sector identity were included as random factors. The distance of individuals from cave entrance, and the vertical position of frogs (i.e., height above the cave floor) were the dependent variables of the two LMMs. This procedure was repeated on adults only, replacing the independent variable age class with sex, in order to detect differences between adult males and females. All analyses were performed in the R environment using packages lme4, lmerTest, nlme and unmarked (Fiske and Chandler 2011, Douglas et al. 2015, Kuznetsova et al. 2016, Pinheiro et al. 2016, R Core Team 2016) . Results We performed a total of 765 surveys within 66 cave sectors (missing data due to unfavorable climatic condition represent 4.42%), recording 122 detections of Rana italica (60 females, 9 males, 38 juveniles and 15 unsexed individuals) (Table 1); on average (±Error Standard; ES), we observed 1.14 ± 0.21 individuals per survey (Fig. 2). The abundance of R. italica was strongly related to the depth of the sector (F1,98.28 = 30.40, P < 0.001), air temperature (F1,716.39 = 4.29, P = 0.038), illuminance (F1,143.82 = 8.01, P = 0.005) and to the presence of two insect species, Dolichopoda laetitiae (F1,645.63 = 7.71, P = 0.006) and Limonia nubeculosa (F1,730.17 = 5.50, P = 0.019). Overall, frogs were more abundant in shallow sectors with less light and warmer temperature, and with the presence of both D. laetitiae and L. nubeculosa. Furthermore, we detected significant differences of frog abundance among months (F11,704.58 = 2.46, P = 0.005). March and November were the survey months in which we recorded the highest frog abundance (Fig. 2). All other considered variables were not significant (P > 0.17). The distance from the cave entrance did not show significant differences between age classes, without differences among survey months (age class: F1,67 = 0.80, P = 0.374; month: F9,67 = 1.04, P = 0.417) (Fig. 3A), nor between sexes (sex: F1,30 = 0.56, P = 0.46; month: F9,30 = 0.45, P = 0.894) (Fig. 3B). The use of walls was significantly different between age classes (F1,67 = 4.92, P = 0.03) (Fig. 3C) without differences among survey months (F9,67 = 1.86, P = 0.073); adults generally occupied higher position compared to juveniles. Within adults, we did not detect differences between males and females (month: F9,30 = 1.07, P = 0.413; sex: F1,30 = 0.01, P = 0.912) (Fig. 3D). Discussion Rana italica was observed in subterranean environments throughout the year, even though the number of observations varied between months (Fig. 2). The abundance of Rana italica in subterranean environments was higher in areas close to the cave entrance, but deep enough to show almost no light. These particular areas correspond to the twilight zone (Culver and Pipan 2014) , where external influence is moderate and abundance of non-strictly cave-dwelling species is the highest (Lunghi et al. 2015, Lunghi et al. 2017) . The amount of incoming light represents an important factor for R. italica, as it influences both presence and abundance of the species in subterranean environments (Lunghi et al. 2017) . Stream frogs are mostly nocturnal, and preference for twilight areas might help them to avoid predators (Vanni and Nistri 2006); however, we cannot exclude that the selection of sectors without light may be also related to the avoidance of harsher climatic conditions (hot and dry), which are present close to the surface (Hetema et al. 2012, Everall et al. 2014) . Temperature was an additional parameter strongly related to abundance of R. italica. Frogs were more abundant in relatively warm cave sectors. The temperature of cave sectors is the result of complex interactions between external temperature, mean annual temperature, and air circulation of karstic systems (Badino 2004, Badino 2010, Lunghi et al. 2015) . In winter, temperature is highest far from the surface, thus these sectors represent ideal shelters during hibernation. Conversely, in summer the temperature is highest close to cave entrance where prey richness is highest (Manenti et al. 2015, Lunghi et al. 2017) . Indeed, the abundance of frogs was positively related to the presence of invertebrates such as the cave cricket Dolichopoda laetitiae and the fly Limonia nubeculosa. Stream frogs are generalist predators of small invertebrates, and these two insects are often abundant in subterranean environments, therefore they have a key role in sustaining subterranean trophic networks (de Pasquale et al. 1995, Lavoie et al. 2007, Manenti et al. 2015) . Recent studies underlined that the occurrence of the cricket D. laetitiae is strongly related to inner cave temperature, as this cricket prefers cave areas with relatively warm temperature (Lunghi et al. 2015, Lunghi et al. 2017) . No particular information is available on the seasonal occupancy of caves by Limonia nubeculosa. Therefore, the relationship between R. italica abundance and the occurrence of these species is likely to represent the result of trophic interactions. As already observed for other amphibians present in subterranean environments, individuals of R. italica probably face a trade-off between the selection of suitable conditions, and the need of trophic resources. Thus, frogs occupy cave portions that are deep enough to have a suitable microclimate and lack of predators, but that are not too far from feeding areas (Ficetola et al. 2013, Lunghi et al. 2016) . The abundance and the frequency of individuals found in subterranean environments suggest that further investigations should be performed on the trophic role and the impact that R. italica may have on the cave food web. In a study performed on the pickerel frog (Rana palustris (LeConte, 1825)) involving analyses with both stable isotopes and stomach contents, authors identified a significant predator activity of this species within the cave habitat (Fenolio et al. 2005) . In our study, the correlation between R. italica and the two insect species suggests that some trophic relationships may occur, as it is possible that frogs are more abundant in cave sectors with the presence of potential prey. On the other hand, it is also possible that some unrecorded features (e.g., availability of resources) positively influence the abundance of multiple species, including both frogs and insects. Indeed, as recently underlined for aquatic subterranean sites, amphibian predators exploiting subterranean environments not only contribute to the top-down control of prey, but also provide an important subsidy in terms of energy for such environments (Barzaghi et al. 2017) . Frog distribution within caves was similar between age classes and sexes (Fig. 3A–B), suggesting that there is neither spatial segregation between age classes, nor between adult sexes. Actually, no information exists on a possible spatial segregation between individuals of Rana italica. In our study, the abundance and diversity of potential prey observed in subterranean environments likely promote the co-existence of different individuals. However, the use of the subterranean space by R. italica was not limited to the cave floor, as frogs often climbed walls (Figs 1B, 3C–D). This particular behavior, which is generally unusual for frogs, might be compared to observations reported for other two anuran species. In green frogs (Pelophylax synklepton hispanicus (Bonaparte, 1839)) some adults were observed preying on high tree branches (Mori et al. 2013) . In artificial subterranean environments, the Iberian frog (Rana iberica Boulenger, 1879) has been observed climbing up the walls, probably looking for shelters (Rosa and Penado 2013) . In our study, adults were observed more frequently being up higher along cave walls compared to juveniles (Fig. 3C); this divergence could be related to a different climbing ability and/or behavior between age classes. Conclusions This study represents the first analysis on the factors related to the abundance and the spatial use of Rana italica in subterranean environments. The obtained results enable us to hypothesize that subterranean abundance of R. italica is mostly related to foraging activities, thus likely make this species one of the top predators of the twilight zone. Our study underlines that the trophic role of terrestrial predators exploiting subterranean environments should be taken into account for the ecological comprehension of determinants which have promoted the colonization of caves. Nonetheless, subterranean environments may also be of key importance to maintain the viability of anuran populations in the light of the occurring global warming. Acknowledgements The Ministry of the Environment and Protection of Land and Sea and Provinces of Prato and Pistoia provided authorization to perform this study (Permits n. 0046894/ PNM,15/10/2013; n. 448, 13/2/2013; n. 731, 21/02/2013). We thank L. Kaven for checking the manuscript spelling. Badino G ( 2004 ) Cave temperatures and global climatic change . International Journal of Speleology 33 : 103 - 114 . https://doi.org/10.5038/1827-806X. 33 .1. 10 Badino G ( 2010 ) Underground meteorology - “what's the weather underground?” . Acta Carsologica 39 : 427 - 448 . https://doi.org/10.3986/ac.v39i3. 74 Banks-Leite C , Pardini R , Boscolo D , Righetto Cassano C , Püttker T , Santos Barros C , Barlow J ( 2014 ) Assessing the utility of statistical adjustments for imperfect detection in tropical conservation science . Journal of Applied Ecology 51 : 849 - 859 . https://doi. org/10.1111/ 1365 - 2664 . 12272 Barke RJ , Schofield MR , Link WA , Sauer JR ( 2017 ) On the reliability of N-mixture models for count data. Biometrics 1-9 . https://doi.org/10.1111/biom.12734 Barzaghi B , Ficetola GF , Pennati R , Manenti R ( 2017 ) Biphasic predators provide biomass subsidies in small freshwater habitats: a case study of spring and cave pools . Freshwater Biology 62 ( 9 ): 1637 - 1644 . https://doi.org/10.1111/fwb.12975 Biswas J ( 2014 ) Occurrence and distribution of cave dwelling frogs of peninsular India . Ambient Science 1 ( 2 ): 17 - 25 . https://doi.org/10.21276/ambi. 2014 . 01 .2.rv02 Bressi N , Dolce S ( 1999 ) Osservazioni di anfibi e rettili in grotta . Rivista di Idrobiologia 38 : 475 - 483 . Buono V , Guarino FM , Vignoli L ( 2014 ) Maximum body size and age distribution in the Italian stream frog, Rana italica Dubois 1987 (Amphibia: Anura) . Acta Herpetologica 9 ( 2 ): 231 - 235 . https://doi.org/10.13128/Acta_Herpetol- 14209 Canestrelli D , Cimmaruta R , Nascetti G ( 2008 ) Population genetic structure and diversity of the Apennine endemic stream frog, Rana italica - insights on the Pleistocene evolutionary history of the Italian peninsular biota . Molecular Ecology 17 : 3856 - 3872 . https://doi. org/10.1111/j. 1365 - 294X . 2008 . 03870 .x Crump ML , Scott NJ ( 1994 ) Visual Encounter Surveys . In: Heyer WR , Donnelly MA , McDiarmid RW , Hayek LC , Foster MS (Eds) Measuring and monitoring biological diversity: standard methods for Amphibians , Smithsonian Institution Press, Washington, 84 - 92 . Culver DC , Pipan T ( 2014 ) Shallow Subterranean Habitats: Ecology, Evolution, and Conservation , Oxford University Press. New York, 288 pp. https ://doi.org/10.1093/acprof:o so/9780199646173.001.0001 de Pasquale L , Cesaroni D , di Russo C , Sbordoni V ( 1995 ) Trophic niche, age structure and seasonality in Dolichopoda cave crickets . Ecography 18 : 217 - 224 . https://doi. org/10.1111/j.1600- 0587 . 1995 .tb00124.x Douglas B , Maechler M , Bolker B , Walker S ( 2015 ) Fitting Linear Mixed-Effects Models using lme4 . Journal of Statistical Software 67 ( 1 ): 1 - 48 . https://doi.org/10.18637/jss.v067.i01 Everall N , Johnson MF , Wilby RL , Bennett CJ ( 2014 ) Detecting phenology change in the mayfly Ephemera danica: responses to spatial and temporal water temperature variations . Ecological Entomology 40 ( 2 ): 95 - 105 . https://doi.org/10.1111/een.12164 Fenolio DB , Graening GO , Stout JF ( 2005 ) Seasonal movement patterns of pickerel frogs (Rana palustris) in an Ozark cave and trophic implications supported by stable isotope evidence . Southwestern Naturalist 50 : 385 - 389 . https://doi.org/10. 1894 /0038- 4909 ( 2005 ) 050 [0385:SMPOPF] 2.0 .CO; 2 Ficetola GF , Pennati R , Manenti R ( 2013 ) Spatial segregation among age classes in cave salamanders: habitat selection or social interactions? Population Ecology 55 : 217 - 226 . https:// doi.org/10.1007/s10144-012-0350-5 Fiske I , Chandler R ( 2011 ) unmarked: an R package for fitting hierarchical models of wildlife occurrence and abundance . Journal of Statistical Software 43 ( 10 ): 1 - 23 . https://doi. org/10.18637/jss.v043.i10 Forrester TD , Casady DS , Wittmer HU ( 2015 ) Home sweet home: fitness consequences of site familiarity in female black-tailed deer . Behavioral Ecology and Sociobiology 69 : 603 - 612 . https://doi.org/10.1007/s00265-014-1871-z Hetema RS , Strauss WM , Fick LG , Maloney SK , Meyer LCR , Shobrak M , Fuller A , Mitchell D ( 2012 ) Activity re-assignment and microclimate selection of free-living Arabian oryx: responses that could minimise the effects of climate change on homeostasis? Zoology 115 : 411 - 416 . https://doi.org/10.1016/j.zool. 2012 . 04 .005 Köhler J , Vences M , D'Cruze N , Glaw F ( 2010 ) Giant dwarfs: discovery of a radiation of largebodied 'stump-toed frogs' from karstic cave environments of northern Madagascar . Journal of Zoology 282 : 21 - 38 . https://doi.org/10.1111/j.1469- 7998 . 2010 . 00708 .x Koller K ( 2017 ) Underground occurrences of three species of amphibians and reptiles with special emphasis on Rana latastei (Amphibia: Anura) . North-Western Journal of Zoology , 13 ( 1 ): 176 - 179 . Kuznetsova A , Brockhoff B , Christensen HB ( 2016 ). lmerTest: Tests in Linear Mixed Effects Models - R package version 2 .0- 2 .9. htp://www.r-project.org Lanza B , Andreone F , Bologna MA , Corti C , Razzetti E ( 2006 ) Fauna d'Italia . Amphibia, Calderini. Bologna, 537 pp. Lavoie KH , Helf KL , Poulson TL ( 2007 ) The biology and ecology of North American cave crickets . Journal of Cave and Karst Studies 69 : 114 - 134 . Lunghi E , Manenti R , Canciani G , Scarì G , Pennati R , Ficetola GF ( 2016 ) Thermal equilibrium and temperature differences among body regions in European plethodontid salamanders . Journal of Thermal Biology 60 : 79 - 85https ://doi.org/10.1016/j.jtherbio. 2016 . 06 .010 Lunghi E , Manenti R , Ficetola GF ( 2014 ) Do cave features affect underground habitat exploitation by non-troglobite species? Acta Oecologica 55 : 29 - 35 . https://doi.org/10.1016/j. actao. 2013 . 11 .003 Lunghi E , Manenti R , Ficetola GF ( 2015 ) Seasonal variation in microhabitat of salamanders: environmental variation or shift of habitat selection? PeerJ 3: e1122 . https://doi. org/10.7717/peerj.1122 Lunghi E , Manenti R , Ficetola GF ( 2017 ) Cave features, seasonality and subterranean distribution of non-obligate cave dwellers . PeerJ 5 : e3169. https://doi.org/10.3986/ac.v44i1. 649 Manenti R , Lunghi E , Ficetola GF ( 2015 ) Distribution of spiders in cave twilight zone depends on microclimatic features and trophic supply . Invertebrate Biology 134 : 242 - 251 . https:// doi.org/10.1111/ivb.12092 Manenti R , Lunghi E , Ficetola GF ( 2017 ) Cave exploitation by an usual epigean species: a review on the current knowledge on fire salamander breeding in cave . Biogeographia 32 : 31 - 46 . https://doi.org/10.21426/B632136017 Matavelli R , Martins Campos A , Neves Feio R , Lopes Ferreira R ( 2015 ) Occurrence of anurans in Brazilian caves . Acta Carsologica 44 ( 1 ): 107 - 120 . Mori E , Bruni G , Domeneghetti D , Menchetti M ( 2013 ) Pelophylax synklepton hispanicus (Bonaparte, 1839) on the branches of a tree . Herpetology Notes 5 : 515 - 517 . Niemiller ML , Miller BT ( 2007 ) Subterranean reproduction of the southern two-lined salamander (Eurycea cirrigera) from short mountain , Tennessee. Herpetological Conservation and Biology 2 ( 2 ): 106 - 112 . Pierce BA , Mcentire KD , Wall AAE ( 2014 ) Population size, movement, and reproduction of the Georgetown salamander, Eurycea naufragia . Herpetological Conservation and Biology 9 ( 1 ): 137 - 145 . Pinheiro J , Bates D , DebRoy S , Sarkar D , Team RC ( 2016 ) nlme: Linear and Nonlinear Mixed Effects Models . R package version 3 . 1 - 128 , http://CRAN.R-project.org/package=nlme R Core Team ( 2016 ) R: a language and environment for statistical computing . http://www.Rproject.org/ Romero A ( 2009 ) Cave Biology: Life in Darkness (Ecology, Biodiversity and Conservation). Cambridge University Press, Cambridge, 306 pp. Rosa GM , Penado A ( 2013 ) Rana iberica (Boulenger, 1879) goes underground: subterranean habitat usage and new insights on natural history . Subterranean Biology 11 : 15 - 29 . https://doi.org/10.3897/subtbiol.11.5170 Sindaco R , Grieco C ( 2014 ) Monitoring of Salamandrina perspicillata (Savi, 1821 ) and Rana italica Dubois, 1987, twenty years later (Amphibia: Salamandridae, Ranidae) . Alytes 30 : 27 - 32 . Soares D , Adams R , Hammond S , Slay ME , Fenolio DB , Niemiller ML ( 2017 ) Evolution of coprophagy and nutrient absorption in a Cave Salamander . Subterranean Biology 24 : 1 - 9 . https://doi.org/10.3897/subtbiol.24.15013 Vanni S , Nistri A ( 2006 ) Atlante degli Anfibi e dei Rettili della Toscana, Regione Toscana, Università degli Studi di Firenze, Museo di Storia Naturale, Sezione Zoologica “La Specola” . Firenze , 379 pp. Vörös J , Maárton O , Schmidt BR , Tünde Gál J , Jelić D ( 2017 ) Surveying Europe's only cavedwelling chordate species (Proteus anguinus) using environmental DNA . PloS ONE 12 ( 1): e0170945 . https://doi.org/10.1371/journal.pone.0170945


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Enrico Lunghi, Giacomo Bruni, Francesco Gentile Ficetola, Raoul Manenti. Is the Italian stream frog (Rana italica Dubois, 1987) an opportunistic exploiter of cave twilight zone?, Subterranean Biology, 2018, 49-60, DOI: doi:10.3897/subtbiol.25.23803