SE Iberian Peninsula Research Articles

Diapausing egg banks, lake size, and genetic diversity in the rotifer Brachionus plicatilis M\xfcller (Rotifera, Monogononta)

Diapausing egg banks are reservoirs of ecological and genetic diversity in continental zooplankton. However, although habitat size has often been used as a proxy for population size, the relationship between diapausing egg bank size and genetic diversity has not been explicitly tested in zooplankton. We estimated the density and size of diapausing egg banks, habitat size and genetic diversity (for mitochondrial and nuclear markers) of 14 populations of the rotifer Brachionus plicatilis in an endorheic basin in the SE Iberian Peninsula. The size of B. plicatilis diapausing egg banks ranged across eight orders of magnitude (from 257 to 4.9 × 1010 eggs). Despite the small geographical scale, populations were strongly structured genetically, but with no evidence of isolation by distance. Habitat size (lake area) was a better predictor of genetic diversity than total diapausing egg bank size, but only for mtDNA haplotype diversity. However, as these results were driven by the strong effect of the largest lake in the database, they should be taken with caution. Our results suggest that large lakes could have a disproportionate effect on genetic diversity and that more work is needed to support the use of habitat size as a proxy of population size in rotifers.

Water availability and species identity control shrub colonization in abandoned semiarid steppes

The increase in shrub cover and density is a widespread phenomenon in drylands worldwide. Its causes and consequences are complex and strongly idiosyncratic. Detailed knowledge of the rate of shrub colonization, and its abiotic and biotic drivers is crucial to fully understand and manage these areas. We used a set of aerial photographs (1956, 1978, 1985, 1998 and 2009) and field data to relate shrub patch dynamics, and abiotic and biotic properties of 27 abandoned steppes in SE Iberian Peninsula. Shrub patch density in 2009 ranged from 11 to 143patchesha−1, and increased by an average of ∼180% between 1956 and 2009. Temporal changes in shrub patch density followed non-linear functions (monomolecular, logistic and exponential) describing early, gradual and late recruitment, respectively. Differences in shrub patch colonization rate were related to the identity of patch-forming species, but contingent on water availability. Total increases in shrub patch density were larger when patches were dominated by late colonizer species. Overall shrub patch dynamics was mostly related to the identity of patch-forming species and climatic conditions, and to a lesser extent physical factors such as aspect and rock cover. Given the sensitivity of patch-forming species to climatic conditions, new challenges for steppe management will emerge over the next decades. Species able to thrive under harsh conditions may increase their dominance at the expense of species adapted to less demanding conditions.

Latest Early Pleistocene remains of Lynx pardinus (Carnivora, Felidae) from the Iberian Peninsula: Taxonomy and evolutionary implications

The Iberian lynx (Lynx pardinus) is a critically endangered felid that, during the last fifty years, has been subject to an intensive conservation program in an attempt to save it from extinction. This species is first recorded at ca. 1.7–1.6 Ma (late Villafranchian, late Early Pleistocene) in NE Iberian Peninsula, roughly coinciding with the large faunal turnover that occurred around the middle to late Villafranchian boundary. Here we describe the largest collection of L. pardinus remains available to date from the Iberian late Early Pleistocene (Epivillafranchian), including localities from the Vallparadís Section (Vallès-Penedès Basin, NE Iberian Peninsula) and Cueva Victoria (Cartagena, SE Iberian Peninsula). The morphology and biometry of the studied material attests to the widespread occurrence of L. pardinus in the Mediterranean coast of the Iberian Peninsula since the latest Early Pleistocene, i.e., about 0.5 million years earlier than it was generally accepted (i.e., at the beginning of the Middle Pleistocene). Based on the features observed in the large sample studied in this paper, we conclude that Lynx spelaeus is a junior synonym of L. pardinus and further propose to assign all the Epivillafranchian and younger fossil lynxes from SW Europe to the extant species L. pardinus. Due to the arrival of the Eurasian lynx (Lynx lynx) into Europe at the beginning of the Late Pleistocene, the attribution of specimens younger than MIS 5e to either this species or L. pardinus solely on morphological grounds has proven equivocal. Here we discuss the main diagnostic features of both species of European lynxes and further review their evolutionary history and paleobiogeography throughout the Pleistocene.

Resilience of Mediterranean terrestrial ecosystems and fire severity in semiarid areas: Responses of Aleppo pine forests in the short, mid and long term

In recent decades, the fire regime of the Mediterranean Basin has been disturbed by various factors: climate change; forest management policies; land cover; changed landscape. Size and severity have notably increased, which in turn have increased large fires events with >500ha burned (high severity). In spite of Mediterranean ecosystems' high resilience to fire, these changes have implied more vulnerability and reduced natural recovery with irreparable long-term negative effects. Knowledge of the response of ecosystems to increasing severity, mainly in semiarid areas, is still lacking, which is needed to rehabilitate and restore burned areas.Our approach assessed the resilience concept by focusing on the recovery of ecosystem functions and services, measured as changes in the composition and diversity of plant community vegetation and structure. This will be validated in the long term as a model of ecosystem response. Also, depending on the pre-fire characteristics of vegetation, fire severity and the post-fire management, this approach will lead to tools that can be applied to implement post-fire restoration efforts in order to help decision making in planning activities.Regarding Mediterranean ecosystems' ability to recover after wildfires, this study concludes that pre-fire communities are resilient in these fire-prone areas, but the window for natural recovery in semiarid areas of Aleppo pine forest in SE Iberian Peninsula varied from 3 to 15 post-fire years. Fire severity was also key for effects on the ecosystem: the vegetation types of areas burned with low and medium severity recovered naturally, while those areas with a high-severity burn induced shrublands. We concluded that very strong regeneration activity exists in the short term, and that the negative effects of medium- and high-severity fire are evidenced in the mid and long term, which affect natural recovery. Adaptive forest management to rehabilitate and restore burned Mediterranean ecosystems should be implemented.

Amino acid epimerization dating of Quaternary coastal deformation in SE Iberian Peninsula: The region between Aguas and Antas Rivers’ mouths

The coastal area between the mouths of the Aguas and Antas Rivers presents a deformed system of raised marine deposits, some of which have been strongly affected by active tectonics. The use of amino acid epimerization dating of Glycymeris shells from raised coastal deposits allowed determining the age of these marine deposits, all of them linked to highstand sea levels in the Mediterranean realm, with ages between MIS 11 and MIS 1. These results allowed corroborating the age of some previously studied sites, and using new sampling sites, the general aminostratigraphy for the Quaternary raised marine deposits on the Mediterranean coast was confirmed. The main deformation event took place after MIS 11 and continued until MIS 5, and was linked to the activity of the Palomares Fault.

Designing conservation strategies to preserve the genetic diversity of Astragalus edulis Bunge, an endangered species from western Mediterranean region.

Astragalus edulis (Fabaceae) is an endangered annual species from the western Mediterranean region that colonized the SE Iberian Peninsula, NE and SW Morocco, and the easternmost Macaronesian islands (Lanzarote and Fuerteventura). Although in Spain some conservation measures have been adopted, it is still necessary to develop an appropriate management plan to preserve genetic diversity across the entire distribution area of the species. Our main objective was to use population genetics as well as ecological and phylogeographic data to select Relevant Genetic Units for Conservation (RGUCs) as the first step in designing conservation plans for A. edulis. We identified six RGUCs for in situ conservation, based on estimations of population genetic structure and probabilities of loss of rare alleles. Additionally, further population parameters, i.e. occupation area, population size, vulnerability, legal status of the population areas, and the historical haplotype distribution, were considered in order to establish which populations deserve conservation priority. Three populations from the Iberian Peninsula, two from Morocco, and one from the Canary Islands represent the total genetic diversity of the species and the rarest allelic variation. Ex situ conservation is recommended to complement the preservation of A. edulis, given that effective in situ population protection is not feasible in all cases. The consideration of complementary phylogeographic and ecological data is useful for management efforts to preserve the evolutionary potential of the species.

Lateglacial to Early Holocene recursive aridity events in the SE Mediterranean Iberian Peninsula: The Salines playa lake case study

Twelve pollen-inferred aridity major and minor events (S1 to S12) have been identified at Salines playa lake (SE Iberian Peninsula, 475 m asl, 38° 30′ 02″ N 00° 53′ 18″ W) from the Lateglacial to the Early Holocene (Boreal). These dry events consist of an increase in the aridity quotient calculated as a function of selected pollen taxa at 13.4, 13, 12.55, 12.2, 11.9, 11.45, 11, 10.6, 10.3, 10, 9.5 and 8.3 ka cal BP. These dry events correspond to the previous identified cold spells such as the Younger Dryas, as well as the 8, 7, 6 and 5 Bond events, and 11.4 and 9.3 events. This climate record highlights the complex glacial-interglacial transition in extra-tropical latitudes, with centennial-scale abrupt climate fluctuations, a signature scarcely recorded in other palaeoecological records of the SE Iberian Peninsula. This work has major implications for the study of human socio-ecological systems and resilience in SE Iberia during the Epipaleolithic and Mesolithic periods.

Lateral Offset Quality Rating along Low Slip Rate Faults: Application to the Alhama de Murcia Fault (SE Iberian Peninsula)

Seismic hazard assessment of strike-slip faults is based partly on the identification and mapping of landforms laterally offset due to fault activity. The characterization of these features affected by slow-moving faults is challenging relative to studies emphasizing rapidly slipping faults. We propose a methodology for scoring fault offsets based on subjective and objective qualities. We apply this methodology to the Alhama de Murcia fault (SE Iberian Peninsula) where we identify 138 offset features that we mapped on a high-resolution (0.5 × 0.5 m pixel size) Digital Elevation Model (DEM). The amount of offset, the uncertainty of the measurement, the subjective and objective qualities, and the parameters that affect objective quality are independent variables, suggesting that our methodological scoring approach is good. Based on the offset measurements and qualifications we calculate the Cumulative Offset Probability Density (COPD) for the entire fault and for each fault segment. The COPD for the segments differ from each other. Tentative interpretation of the COPDs implies that the slip rate varies from one segment to the other (we assume that channels with the same amount of offset were incised synchronously). We compare the COPD with climate proxy curves (aligning using the very limited age control) to test if entrenchment events are coincident with climatic changes. Channel incision along one of the traces in Lorca-Totana segment may be related to transitions from glacial to interglacial periods.

Taxonomical identity of <em>Sarcocornia fruticosa</em> and <em>S. hispanica</em> in the Iberian Peninsula

Guillo, A., Alonso, M.A., Lendinez, M.L., Salazar, C. & Juan, A. 2014. Taxonomical identity of Sarcocornia fruticosa and S. hispanica in the Iberian Peninsula. Anales Jard. Bot. Madrid 71(2): e011. The recent description of Sarcocornia hispanica, from SE Iberian Peninsula evidences the notable morphological complexity of this genus. This species is quite close to S. fruticosa, as they both show an erect habit and lack of rooting stems. Besides, S. fruticosa has been traditionally recorded for the same geographical area of S. hispanica. However, the original description of S. hispanica did not include any mention about these two taxa would live together and which ones are the differential morphological characters. Our study aims to clarify their main morphological differences and to address two questions. Firstly, if two close species would be coexisting or secondly, if both species would not live together and then only one erect shrubby species should be recognised for the southeastern peninsular. Therefore, a detailed morphological study of these two species was carried out using vegetative and reproductive characters together with SEM features. Based on the original description, the main morphological features of S. hispanica were compared, plus other features which would support their identification. Our data pointed out the existence of a marked overlapping for most of the studied characters independently of the geographical procedence of the samples. As a result, no significant morphological differences have been found between both taxa, and S. hispanica is proposed as a mere synonym of S. fruticosa.

Stand management to reduce fire risk promotes understorey plant diversity and biomass in a semi‐aridPinus halepensisplantation

AbstractQuestionsHow do thinning and understorey management practices (ploughing, clearing) to reduce fire risk affect plant species composition, diversity and biomass within pine plantations on previous croplands? Do managed pine plantations promote changes in plant succession compared to unplanted areas (old fields) towards restoration goals including holm oak forest or other alternative land‐use types?LocationAltiplano del Conejo, Guadix‐Baza Basin,SEIberian Peninsula, Spain.MethodsWe evaluated plant species composition, diversity, cover and biomass in the understorey of a semi‐arid 10‐yr‐old afforestation area ofPinus halepensisthrough a manipulative experiment in which four different thinning regimes (T0 treatment: control plots; T100, T75, T60 and T48 treatments: 100%, 75%, 60%, and 48% of mean basal area removed, respectively), and two understorey vegetation treatments (clearing, ploughing) were applied, simulating stand practices to reduce fire risk. Sampling was performed annually for 5 yr (from 2006 to 2010). For comparison, four other land‐use types (rain‐fed cereal crops, old fields, alpha grass steppes and holm oak forests) were sampled to quantify understorey vegetation community composition and diversity.ResultsAfforestation plots were compositionally distinct from each other within 5 yr, mainly as a result of canopy thinning and to a lesser extent, vegetation treatments. Total species richness was highest in the low to medium densities of pines, where richness approached that found in native communities. However, afforestation plots were most similar in diversity, life‐form type and composition to abandoned agricultural fields, and large differences were found between afforestation plots, native forests and alpha grass steppes.ConclusionsThis study demonstrates that plant species composition in the understorey of pine plantations on former cropland can respond rapidly to common management practices intended to reduce fire risk. In particular, tree thinning increases both understorey plant diversity and biomass, but does not lead to recruitment of species that are typical of native forests. Rates of native forest succession appear to be slow in this semi‐arid Mediterranean ecosystem. Current pine plantation management practices, while useful for increasing understorey biomass and plant diversity will need to be coupled with additional restoration techniques (e.g. seeding and transplants) to recover species composition and structure of native forests.

Naturalization of almond trees (Prunus dulcis) in semi-arid regions of the Western Mediterranean

Agricultural land abandonment is rampant in present day Europe. A major consequence of this phenomenon is the re-colonization of these areas by the original vegetation. However, some agricultural, exotic species are able to naturalize and colonize these abandoned lands. In this study we explore the ability of almonds (Prunus dulcis D.A. Webb.) to establish in abandoned croplands in semi-arid areas of SE Iberian Peninsula. Domesticated during the early Holocene in SW Asia and the Eastern Mediterranean, the almond has spread as a crop all over the world. We established three plots adjacent to almond orchards on land that was abandoned and reforested with Aleppo pine (Pinus halepensis Mill.) and Holm oak (Quercus ilex L.) about 20 years ago. We recorded the abundance of almond seeds, seedlings, juveniles, pre-reproductives and adults in these plots, and determined their recruitment microhabitat. We found natural regeneration in all three plots, with almond density higher than 150 individuals/ha in each plot. About half of the almonds in the plots were juveniles, although 7% were one-year seedlings and 3% were adult trees. This suggests that colonization of abandoned lands is an ongoing gradual process. Most naturally established almonds were under tree cover, although this was not the most abundant microhabitat, avoiding the negative impact of browsing by Red Deer (Cervus elaphus) and domestic sheep and goats. In addition, the mean distance from the nearest seed source was 77 m. These findings suggest the action of mobile almond dispersers. Several Corvid species including the Carrion Crow (Corvus corone) and the Magpie (Pica pica) have been observed consuming and moving almonds in the study area. Our study has demonstrated that almonds are colonizing abandoned lands mostly as a consequence of effective seed dispersal by some animals. We show that almonds have the potential to become fully naturalized in the near future in many semi-arid areas of the Western Mediterranean.

Population structure and secondary production of Siriella clausii, a dominant detritus feeding mysid in Posidonia oceanica meadows (W Mediterranean Sea)

Temporal trends in abundance, demographic structure of the population and secondary production of Siriella clausii were studied at three different sectors of Posidonia oceanica meadows in the SE Iberian Peninsula, with different levels of habitat complexity. Secondary production was calculated through three methods widely employed in marine invertebrates: the Hynes method (based on demographic structure data) and models by Morin-Bourassa and Brey (based on biomass data). This filter/grazer and detritus feeder is the most abundant mysid in P. oceanica seagrass meadows in the Mediterranean. The population structure was similar in the three sectors, but the temporal pattern of abundance was different, at times even opposite. This pattern may be related to the aggregated spatial distribution, metapopulation dynamics or stochastic factors, but other potential factors could be involved, such as habitat features or predation rates. The values of production oscillated between 25 and 60 mgAFDW/m2/year, depending on the calculation method that was applied, and showed differences between sites and seagrass complexity. The present values are intermediate between those characterising highly productive systems, such as estuaries, and systems of limited productivity (bathyal habitats). Compared to other peracarids, mysid production is greater than that of isopods and less than amphipod production. This is possibly related to the life cycle and reproductive strategies. Detritus feeders such as S. clausii may play an important trophic role due their capacity to use as food the biomass associated to detritus, which constitutes larges reservoirs of carbon derived from seagrass primary production.

Deformación cortical de las Béticas Orientales observada mediante GPS y su relación con el terremoto de Lorca

On May 11 th of 2011, a seismic series occurred near the city of Lorca (Murcia). The main earthquake of magnitude Mw 5.2 has been attributed to the Alhama de Murcia Fault, one of the most active faults in the SE Iberian Peninsula. We analyzed data from 5 GPS campaigns of the CuaTeNeo network conducted between 1997 and 2011. The velocities of the stations closest to the Alhama de Murcia Fault show the reverse and strike-slip direction of motion. Stations located on the southeastern side of the fault have the maximum velocities in the area (between 1.4 and 1.8 mm/yr), oriented towards NNW direction, obliquely to the trace of the fault. The kinematics of the fault and the strain rate directions obtained from the CuaTeNeo network GPS measurements matches the calculated focal mechanism of Lorca earthquake. Detailed analysis of the time-series from the continuous GPS station at the Lorca city allows the detection of co-seismic offset of ~6 mm to the North.

Patterns of seasonal activity in a Mediterranean lizard along a 2200 m altitudinal gradient

Ectothermy in reptiles involves strong environmental temperature dependence to maintain body temperature. High mountains are extreme habitats which, because of their marked temperature decrease with altitude, impose difficulties for reptile thermoregulation, as the number of optimum-temperature days diminish in altitude. We studied the activity patterns of the lizard Psammodromus algirus, which has a wide altitudinal distribution, at six sampling stations that spanned an altitudinal range from 300 to 2500m asl in Sierra Nevada (SE Iberian Peninsula). We performed censuses of the species during the seasonal and daily activity period, and measured lizard body temperature and environmental temperature in the six sampling plots along the altitude gradient. The body temperature of the lizards remained closely the same even though environmental temperature decreased around 9°C along that gradient. Seasonal activity peaked at the beginning of the activity period in highlands, but in the middle of the season in middle and lowland regions. However, newborns appeared in the field almost at the same time along the altitude gradient. We suggest that the thermoregulatory strategies of the lizards must vary along this altitudinal gradient, permitting lizards to keep their body temperature close to a very similar optimum and thus, develop very similar circa-annual activity patterns.

Holocene atmospheric conditions in SE Iberian Peninsula inferred from the stable isotopes of land snail shells

Holocene atmospheric conditions in SE Iberian Peninsula inferred from the stable isotopes of land snail shells

Quaternary active tectonic structures in the offshore Bajo Segura basin (SE Iberian Peninsula – Mediterranean Sea)

Abstract. The Bajo Segura fault zone (BSFZ) is the northern terminal splay of the Eastern Betic shear zone (EBSZ), a large left-lateral strike-slip fault system of sigmoid geometry stretching more than 450 km from Alicante to Almería. The BSFZ extends from the onshore Bajo Segura basin further into the Mediterranean Sea and shows a moderate instrumental seismic activity characterized by small earthquakes. Nevertheless, the zone was affected by large historical earthquakes of which the largest was the 1829 Torrevieja earthquake (IEMS98 X). The onshore area of the BSFZ is marked by active transpressive structures (faults and folds), whereas the offshore area has been scarcely explored from the tectonic point of view. During the EVENT-SHELF cruise, a total of 10 high-resolution single-channel seismic sparker profiles were obtained along and across the offshore Bajo Segura basin. Analysis of these profiles resulted in (a) the identification of 6 Quaternary seismo-stratigraphic units bounded by five horizons corresponding to regional erosional surfaces related to global sea level lowstands; and (b) the mapping of the active sub-seafloor structures and their correlation with those described onshore. Moreover, the results suggest that the Bajo Segura blind thrust fault or the Torrevieja left-lateral strike-slip fault, with prolongation offshore, could be considered as the source of the 1829 Torrevieja earthquake. These data improve our understanding of present deformation along the BSFZ and provide new insights into the seismic hazard in the area.

Advantages and drawbacks of living in protected areas: the case of the threatened Erysimum popovii (Brassicaceae) in SE Iberian Peninsula

Protected areas help to develop regional and global strategies for the conservation of biodiversity. However, human-related activities, such as grazing, tourism, hardwood extraction, etc., may cause the decline of some species. In this study, we investigate whether inhabiting protected areas affect the conservation of Erysimum popovii, a narrow endemic and endangered plant, in Mediterranean environments with traditional human activities. We surveyed its entire distribution area in SE Spain, and located 31 populations, 16 within Nature Parks (Category V of the IUCN) and 15 in non protected areas. In each population we measured several variables related to habitat composition, pollinator community, herbivory damage and population viability. Our results show that populations in protected areas inhabit localities at higher altitudes and with more shrub cover. Most important, the abundance of a very effective pollinator type, beeflies, was significantly higher in protected populations. Curiously, damage by ungulates was also more intense in protected areas. The negative effect of herbivory offsets any positive effect played by pollinators in protected areas, and consequently there were not differences in population size or reproductive output inside and outside protected areas. It seems that allowing traditional uses in protected areas may entail negative effects for some vulnerable plant species.

Life-history traits of the invasive fish Gambusia ­holbrooki in saline streams (SE Iberian Peninsula): Does salinity limit its invasive success?

Knowledge of the adaptive ability of the highly invasive fish Gambusia holbrooki to new habitats is essential for determining its invasion potential. Our main objective was to assess the life-history of G. holbrooki in saline streams by studying its abundance, size and age structure, growth and condition. Two populations inhabiting similar streams of different salinity in the southeastern Iberian Peninsula were monitored over a 2 yr period. In both populations, the life- history of the species was characterized by a short life span, a long recruitment period with a mas- sive emergence of young-of-the-year and fast growth of individuals during the first months of their lives. The species showed a less intense recruitment (6.9% of juveniles vs. 46.4% during the recruitment period) and an earlier end of the recruitment period (at least 2 mo) in the hypersaline system, although abundance, hepatic condition and female somatic condition were higher. In addition, temporary increases in salinity diminished population abundance, recruitment, and somatic and hepatic condition. Both populations showed similar seasonal abundance variation patterns, population structures, growth rates, and somatic and hepatic condition cycles. Other environmental factors independent of salinity could have influenced the differentiation in life- history of the species between populations, thus disguising direct relationships between salinity and life-history. However, the studied parameters show that G. holbrooki presents a great ability to adapt to lotic systems with high and different levels of salinity.

Terrestrial arthropod fauna of arid areas of SE Spain: Diversity, biogeography, and conservation

The goal of this paper is to provide a general description of the terrestrial arthropod fauna of arid areas of SE Iberian Peninsula. The available data show that invertebrate communities in these environments are dominated by arthropods and that the composition of the assemblages are similar to those described in other arid regions of the world. The number of species of different arthropod groups (Coleoptera, Hymenoptera, Orthoptera, Lepidoptera, Araneae) in these environments show that arid regions of SE Iberian Peninsula are inhabited by a diverse terrestrial arthropod fauna. An ecological feature of arthropod communities in arid zones of SE Spain is the spatial and temporal variability of assemblage composition at different scales, a characteristic of faunal assemblages in arid environments. Similarity in composition of assemblages between sites (Beta diversity) shows a high variability in faunal composition between apparently similar environments. The distribution patterns of species show that 8.4–9.6% of the species in these environments are local and SE Iberian Peninsula endemics. A number of eremic Mediterranean or Palaearctic species are also associated exclusively with these environments, highlighting the singularity of the invertebrate fauna in these arid habitats. Differences in assemblage composition of arid areas with more mesic surrounding environments show that arid zones of SE Spain are inhabited by a distinct fauna, increasing faunal diversity in SE Spain. A recent analysis of endangered and threatened invertebrate species in southern Spain recognizes the arid environments of SE Spain as priority areas for conservation, where habitat loss and fragmentation, changes in agricultural and grazing uses, and inadequate management constitute the main threats. We conclude that the fauna of the SE Iberian arid zones represents an important component of the high ecological diversity of the Mediterranean ecosystem in SE Spain, not only because of their arthropod diversity but also due to the important implications that these areas have for conservation in the entire SE region of the Iberian Peninsula.

Holocene paleoenvironment (∼7200–4000 cal BP) of the Los Castillejos archaeological site (SE Spain) inferred from the stable isotopes of land snail shells

Neolithic, Copper Age and modern land snail shells from the Los Castillejos archeological site (37°20′N), SE Iberian Peninsula, were analyzed for 13C/ 12C and 18O/ 16O ratios to estimate the paleoenvironmental conditions during shell deposition. Modern and ancient δ 13C values ranged from −9.2‰ to −7.7‰ and from −13.6‰ to −5.7‰, respectively, and they differed among taxa. δ 13C values were similar for Neolithic (δ 13C = −8.1 ± 2.3‰), Copper Age (δ 13C = −8.4 ± 0.6‰) and modern (δ 13C = −8.4 ± 0.5‰) herbivorous Cernuella specimens. Alternatively, fossil shells of the herbivorous Ferussacia folliculum (δ 13C = −9.9 ± 1.2‰) and the omnivorous Rumina decollata (δ 13C = −11 ± 1.2‰) showed substantially lower δ 13C values than modern specimens, which may suggest lower water stress during the early to mid Holocene than today. The δ 18O values from modern specimens ranged from −1.1‰ to +0.6‰ while the δ 18O values from fossil specimens ranged from −6.7‰ to +0‰ and they differed among species. Cernuella exhibited shell δ 18O values that increased from the Neolithic (δ 18O = −2.3 ± 1.8‰) and Copper Age (δ 18O = −1.7 ± 0.6‰) to the present (δ 18O = −0.3 ± 0.5‰). The δ 18O values of fossil shells of F. folliculum (δ 18O = −3.7 ± 1.0‰) and R. decollata (δ 18O = −4.0 ± 1.6‰) were also lower than modern shells. Calculations of a published snail-flux balance mixing model for δ 18O values indicate that early to mid Holocene shells precipitated during times when relative humidity was greater than today. The SE Iberian Peninsula was noticeably wetter ∼7200 cal BP, and experienced drier conditions thereafter. The results are consistent with other regional paleoclimatic proxies and reinforce the potential use of land snail shells as paleoenvironmental archives.