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Gut microbial communities provide essential functions to their hosts and are known to influence both their ecology and evolution. However, our knowledge of these complex associations is still very limited in reptiles. Here we report the 16S rRNA gene faecal microbiota profiles of two lizard species endemic to the Balearic archipelago (Podarcis lilfordi and P. pityusensis), encompassing their allopatric range of distribution through a noninvasive sampling, as an alternative to previ- ous studies that implied killing specimens of these IUCN endangered and near-threatened species, respectively. Both lizard species showed a faecal microbiome composition consistent with their omnivorous trophic ecology, with a high representa- tion of cellulolytic bacteria taxa. We also identified species-specific core microbiota signatures and retrieved lizard species, islet ascription, and seasonality as the main factors in explaining bacterial community composition. The different Balearic Podarcis populations are characterised by harbouring a high proportion of unique bacterial taxa, thus reinforcing their view as unique and divergent evolutionary entities.

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In this article an introduction is given on the geological history leading to the separation of Podarcis lilfordi (GÜNTHER, 1874) and Podarcis pityusensis (BOSCÁ, 1883) as separate species, as well as a Holocene sea level rise model which combined with bathymetric data leads to an estimation of recent divergence time in populations of the Balearic lizards.

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New data on estimated divergence times of the populations of lacertid lizards in the Balearic Islands are provided in this second update of the October 2011 article: Estimating recent divergence time in populations of Podarcis lilfordi (GÜNTHER, 1874) and Podarcis pityusensis (BOSCÁ, 1883) (VAN DEN BERG 2011), which received its first update May 2012. In most cases better estimations of divergence times were available by using the NAVIONICS SonarCharts™webapp.

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This is our fifth report in a series on our whereabouts while collecting data for a future revision of the present subspecific order of the endemic Balearic sisterspecies Podarcis lilfordi (GÜNTHER, 1874) and Podarcis pityusensis (BOSCÁ, 1883), which data are stored in our free accessible database at www.pityusensis.nl (VAN DEN BERG & ZAWADZKI 2011 ; VAN DEN BERG et al. 2013 ; VAN DEN BERG et al. 2014a ; VAN DEN BERG et al. 2014b). During this trip from the 9th of May until the 23rd of May 2015, we were able to collect data on a few mainland Ibiza locations, as well as the following adjacent islands: Punta Galera, Es Canaret, Illa de la Xanga (Sal Rossa), Pouet de Ses Illetes, Formentera, Purroig, Es Vedrà, Rates, Malví Pla (North), Malví Rodó (South), S’Espardell, Calders, Penjats and Ses Margalides. We continue with the ventral coloration as a possible determining key as introduced in our 2014 trip report (VAN DEN BERG et al. 2014b). Images of the anal shields are presented of each lizard for purposes of illustration.

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Phylogenetic relationships and timings of major cladogenesis events are investigated in the Balearic Island lizards Podarcis lilfordi and Podarcis pityusensis using 2675 bp of mitochondrial and nuclear DNA sequences. Partitioned Bayesian and Maximum Parsimony analyses provided a well-resolved phylogeny with high node-support values. Bayesian MCMC estimation of node dates was investigated by comparing means of posterior distributions from different subsets of the sequence against the most robust analysis which used multiple partitions and allowed for rate heterogeneity among branches under a rate-drift model. Evolutionary rates were systematically underestimated and thus divergence times overestimated when sequences containing lower numbers of variable sites were used (based on ingroup node constraints). The following analyses allowed the best recovery of node times under the constant-rate (i.e., perfect clock) model: (i) all cytochrome b sequence (partitioned by codon position), (ii) cytochrome b (codon position 3 alone), (iii) NADH dehydrogenase (subunits 1 and 2; partitioned by codon position), (iv) cytochrome b and NADH dehydrogenase sequence together (six gene–codon partitions), (v) all unpartitioned sequence, (vi) a full multipartition analysis (nine partitions). Of these, only (iv) and (vi) performed well under the rate-drift model. These findings have significant implications for dating of recent divergence times in other taxa. The earliest P. lilfordi cladogenesis event (divergence of Menorcan populations), occurred before the end of the Pliocene, some 2.6 Ma. Subsequent events led to a West Mallorcan lineage (2.0 Ma ago), followed 1.2 Ma ago by divergence of populations from the southern part of the Cabrera archipelago from a widely-distributed group from north Cabrera, northern and southern Mallorcan islets. Divergence within P. pityusensis is more recent with the main Ibiza and Formentera clades sharing a common ancestor at about 1.0 Ma ago. Climatic and sea level changes are likely to have initiated cladogenesis, with lineages making secondary contact during periodic landbridge formation. This oscillating cross-archipelago pattern in which ancient divergence is followed by repeated contact resembles that seen between East-West refugia populations from mainland Europe.

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EL ESTUDIO ABORDADO EN LA TESIS VERSA SOBRE LA CARACTERIZACION TAXONOMICA DE LA LAGARTIJA DE LAS PITIUSAS PODARCIS PITVUSENSIS. SE ANALIZAN LAS DISTINTAS POBLACIONES DESDE TRES ASPECTOS DISTINTOS: EL ANALISISBIOMETRICO EL ANALISIS ELECTROFORETICO DE DISTINTAS PROTEINAS Y EL ANALISIS COLORIMETRICO. LOS ANALISIS ESTADISTICOS APLICADOS SOBRE LAS VARIANTES BIOMETRICAS DEMUESTRAN LA EXISTENCIA DE DIVERSOS GRUPOS DE POBLACIONES MUY SEMEJANTES ENTRE SI. LA VARIABILIDAD DE LA ESPECIE NO SOLO ES FENOTIPICA SINO QUE TAMBIEN ES GENETICA DETECTANDOSE UNA DIVERSIDAD EN ESTOS CARACTERES SUPERIOR A LA ESPERADA EN REPTILES. SE OBSERVA UNA ALTA HETEROSIS QUE ES CARACTERISTICA DE LA ESPECIE LO QUE PARECE DEMOSTRAR QUE ESTA SE ENCUENTRA EN LAS PRIMERAS FASES DE COLONIZACIONY ADAPTACION A LOS DIFERENTES HABITATS OFRECEN LAS ISLAS QUE OCUPA. SE CONSTATA LA ACCION DEL EFECTO FUNDADOR Y LA DERIVA GENETICA EN LOS TRES ASPECTOS CONSIDERADOS EN LA TESIS ASI COMO UNA TENDENCIA EVOLUTIVA HACIA EL AUMENTO DE TAMAÑO SIEMPRE QUE NO EXISTA UNA PRESION SELECTIVA CONTRARIA. SUCEDE LO MISMO CON EL MELANISMO. CONSIDERANDO EL ESTADO EVOLUTIVO ACTUAL DE LA ESPECIE REFLEJADO EN LA PLASTICIDAD DE LAS DISTINTAS POBLACIONES DE ESTALAARTIJA Y EN LA ADAPTACION QUE MANIFIESTAN EN CADA NICHO CONCRETO ASI COMO EL CONCEPTO RESTRICTIVO ACTUAL DE SUBESPECIE LA AUTORA CONSIDERA QUE SOLO PUEDEN CONSIDERARSE SEIS TAXONES SUBESPECIFICOS O SUBESPECIES DE LA LAGARTIJA DE LAS PITIUSAS.

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The dorsal, side and belly colours of 118 specimens of Podarcis pityusensis have been analysed with physical methods. Twenty samples from 16 islands have been chosen, 3 of then from Eivissa Island (Ibiza), 2 from Formentera Island and 2 from Espardell Island. The results reveal great colouration differences between the same island samples and sometimes similar colouration between different islands (different subspecies). specimens. This feature seems to show the colour criteria is not useful in taxonomic subjects for this species.

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The variation in morphological and colouring features shown by the insular lacertid populations of Podarcis pityusensis is discussed from the point of view of their adaptive advantages to specific insular ecosystems. Insularity factors, i.e. area and island-age, have been found to be related to average body size, and the average luminosity of each population. Populations tend to show a size increase, a greater morphological homogeneity and darker dorsal colouring on smaller and older islands. Genetic drift seems to play a secondary role, whereas a positive selection in favour of melanism and giantism is observed. Both features are not linked as cause and effect, but seem to share a common cause: isolation and time enough to allow selection to take place. Predation, though slight in degree, does exist, and seems to be one of the selective pressure favouring melanism, together with the parallel trend towards an increase in body size and the need to an effective thermoregulation during the early hours of the day.

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An electrophoretic comparison of ten colonies of Podarcis pityusensis Bosca, 1882 (Lacertidae) from Ibiza, Formentera and neighbouring islets (Balearic Is., Spain). 71 animals from ten colonies (vide list in text) of the Ibiza wall lizard Podarcis pi- tyusensis Bosca, 1882 were analysed by electrophoresis, on 12 % starch gel, and 16 gene- tic loci were studied, by checking against samples of Podarcis muralis muralis. The genetic frequency resulting in NEI`s identity index (I), reveals no clear differen- ces between the various colonies. However, itcan be seen on the resultant dendogram that P. p. carlkochi (affinis group) is distinct from the pityusensis sensu stricto group colonies. By other means we found characteristic allels for Podarcis pityusensis in four loci: GOT-1, IDM-1, G-6-PD-2 and 6-PGD, which differed from Podarcis muralis allels.

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We examined the diets of several species of Podarcis from different western Mediterranean islands. We tested the prediction of more generalized diets in lizards from poor environments. We also examined the extert and mode of herbivory in relation to arthropod diversity in the diet. Lizards from the Tuscan Archipelago, P. sicula from Menorca, and P. tiliguerta from Corsica all show a rather generalized diet. In contrast, P. lilfordi and P. pilyusensis from the Balearic Islands and, to a lesser extent, P. hispanica from Benidorm Island, appear much more stenophagous, including a high proportion of clumped prey in their diets. Plant matter is a common food item in most of the population studied, specially in Balearic lizards. A marked seasonal shift in the degree of herbivory was observed in these species where high-energy plant parts are frequently consumed during summer. In one of the Balearic Islands (Nitge), the bulk of the summer diet was formed by pollen and nectar of one particular plant species. Herbivory, consumption of clumped prey and other dietary peculiarities of insular populations of Mediterranean lizards indicate a very flexible feeding behaviour compared to mainland congenerics. This could result from a lack of predation pressure allowing high population densities to be reached in islets with poor trophic resources. Differences found in dietary characteristics among island populations can be interpreted as a consequence of different current ecological conditions, as well as historical and biogeographical differences among the islands.

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The parasitic female of the nematode Strongyloides ophiusensis sp. n.. fund in the intestine of lizard Podarcis pityusensis (Bosca, 1883) from Balearic Islands (West Mediterranean), is described. This species differs from other similar Strongyloides species in the body size, the morphology of the stoma, the structure of the ovaries and in the stage of development of the eggs, and also in some ecological and chorological characters.

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Sequences of the cytochrome b gene were analysed for 47 samples of two species of Podarcis from the Balearic Islands (P. pityusensis from Pityuses and P. lilfordi, from Gymnesies archipelago). The average uncorrected distance between the two species studied was 9.7%. The sampled individuals from each species form reciprocally monophyletic units. Assuming an overall rate of change for cytochrome b of 2% per million years the nucleotide divergence of 9.7 ± 1.9% between P. lilfordi and P. pityusensis, could correspond to a divergence time of 4.95 ± 0.95 million years. The separation time between Gymnesies and Pityuses archipelagos according to geological hypotheses is around 5 million years, thus our results suggest the ancestors of the two present forms became isolated during this event. The most parsimonious networks suggest that currently accepted subspecies do not form monophyletic groups, and so should be reassessed. Despite our limited sampling the level of variability is much higher in P. lilfordi than P. pityusensis. Since they are sister taxa the relative age of each species is equal, therefore the differences might be due to historical population structure differences. However it seems that the forms on the islands are not genetically distinct units, implying that morphological differences are recent adaptations to their environments.