Recent evolutionary history of the Iberian endemic lizards Podarcis bocagei (Seoane, 1884) and Podarcis carbonelli Pérez-Mellado, 1981 (Squamata: Lacertidae) revealed by allozyme and microsatellite markers

Lack of country-wide systematic herpetology collections in Portugal jeopardizes future research and conservation

Natural History Collections (NHCs) represent the world's largest repositories of long-term biodiversity datasets. Specimen collection and voucher deposition has been the backbone of NHCs since their inception, but recent decades have seen a drastic decline in rates of growth via active collecting. Amphibians and reptiles are amongst the most threatened zoological groups on the planet and are historically underrepresented in most worldwide NHCs. As part of an ongoing project to review the Portuguese zoological collections in the country's NHCs, herpetological data from its three major museums and smaller collections was gathered and used to examine the coverage and representation of the different taxa extant in Portugal. These collections are not taxonomically, geographically, or temporally complete. Approximately 90% of the Portuguese herpetological taxa are represented in the country's NHCs, and around half of the taxa are represented by less than 50 specimens. Geographically, the collections cover less than 30% of the country's territory and almost all of the occurring taxa have less than 10% of their known distribution represented in the collections. A discussion on the implications for science of such incomplete collections and a review of the current status of Portuguese NHCs is presented.

Variable levels of introgression between the endangered Podarcis carbonelli and highly divergent congeneric species

Recent empirical studies have demonstrated that speciation with gene flow is more common than previously thought. From a conservation perspective, the potential negative effects of hybridization raise concerns on the genetic integrity of endangered species. However, introgressive hybridization has also been growingly recognized as a source of diversity and new advantageous alleles. Carbonell's wall lizard (Podarcis carbonelli) is an endangered species whose distribution overlaps with four other congeneric species. Our goal here was to determine whether P. carbonelli is completely reproductively isolated from its congeners and to evaluate the relevance of hybridization and interspecific gene flow for developing a conservation plan. We used restriction site associated DNA (RAD) sequencing to discover SNPs in samples from four contact zones between P. carbonelli and four other species. Principal component analysis, multilocus genotype assignment and interspecific heterozygosity suggest incomplete reproductive isolation and ongoing gene flow between species. However, hybridization dynamics vary across all pairs, suggesting complex interactions between multiple intrinsic and extrinsic barriers. Despite seemingly ubiquitous interspecific gene flow, we found evidence of strong reproductive isolation across most contact zones. Instead, indirect effects of hybridization like waste of reproductive effort in small isolated populations may be more problematic. Our results highlight the need to further evaluate the consequences of introgression for P. carbonelli, both on a geographic and genomic level and included in a comprehensive and urgently needed conservation plan. Besides, those findings will add important insights on the potential effects of hybridization and introgression for endangered species.

Increase of genetic diversity indicates ecological opportunities in recurrent-fire landscapes for wall lizards

Socioeconomic and climatic factors are modifying fire regimes with an increase of fire frequency and extension. Unfortunately, the effects of recurrent fires on biological processes that ultimately affect the genetic diversity of animal populations are mostly unknown. We examined genetic patterns of diversity in the wall lizard Podarcis guadarramae in northern Portugal, one of the European regions with the highest percentage of burnt land. This species is a small saxicolous lizard as it inhabits natural outcrops and artificial stone walls, likely in recurrent-fire landscapes. We genotyped nine microsatellites from ten populations selected according to a gradient in fire recurrence, and compared genetic diversity indexes and demographic patterns among them. At the population level, we hypothesize that a high level of mortality and population bottlenecks are expected to reduce genetic heterozygosity in sampled localities affected by recurrent fires. Alternatively, genetic signatures are expected to be absent whether fire did not cause high mortality. Regardless of levels of mortality, we expect a gain in genetic diversity whether recurrent fires facilitate lizard dispersal and migration due to the increased quality of the habitat for wall lizards. At the regional level, we examine whether a recurrent fire regime may disrupt the spatial structure of populations. Our results showed an increase in genetic diversity in recurrently burnt populations, and a decline in longer-unburnt populations. We did not detect bottleneck effects in repeatedly-burnt populations. High genetic diversity in recurrent fire populations suggests a high dispersion rate between adjacent metapopulations and perhaps immigration from outside the fire boundary. At the regional level, lizard populations show low differentiation and weak genetic structure, suggesting no effects of fire. This study confirms field-based censuses showing that recurrent-fire regimes give ecological opportunities to wall lizards that benefit from habitat openness.

Where does diversity come from? Linking geographical patterns of morphological, genetic, and environmental variation in wall lizards

BACKGROUND

Understanding how phenotypic variation scales from individuals, through populations, up to species, and how it relates to genetic and environmental factors, is essential for deciphering the evolutionary mechanisms that drive biodiversity. We used two species of Podarcis wall lizards to test whether phenotypic diversity within and divergence across populations follow concordant patterns, and to examine how phenotypic variation responds to genetic and environmental variability across different hierarchical levels of biological organization, in an explicit geographic framework.

RESULTS

We found a general concordance of phenotypic variation across hierarchical levels (i.e. individuals and populations). However, we also found that within-population diversity does not exhibit a coherent geographic structure for most traits, while among-population divergence does, suggesting that different mechanisms may underlie the generation of diversity at these two levels. Furthermore, the association of phenotypic variation with genetic and environmental factors varied extensively between hierarchical levels and across traits, hampering the identification of simple rules to explain what yields diversity.

CONCLUSIONS

Our results in some cases comply with general ecological and evolutionary predictions, but in others they are difficult to explain in the geographic framework used, suggesting that habitat characteristics and other regulatory mechanisms may have a more substantial contribution in shaping phenotypic diversity.

Run for your life, but bite for your rights? How interactions between natural and sexual selection shape functional morphology across habitats

A central issue in evolutionary biology is how morphology, performance, and habitat use coevolve. If morphological variation is tightly associated with habitat use, then differences in morphology should affect fitness through their effect on performance within specific habitats. In this study, we investigate how evolutionary forces mold morphological traits and performance differently given the surrounding environment, at the intraspecific level. For this purpose, we selected populations of the lizard Podarcis bocagei from two different habitat types, agricultural walls and dunes, which we expected to reflect saxicolous vs ground-dwelling habits. In the laboratory, we recorded morphological traits as well as performance traits by measuring sprint speed, climbing capacity, maneuverability, and bite force. Our results revealed fast-evolving ecomorphological variation among populations of P. bocagei, where a direct association existed between head morphology and bite performance. However, we could not establish links between limb morphology and locomotor performance at the individual level. Lizards from walls were better climbers than those from dunes, suggesting a very fast evolutionary response. Interestingly, a significant interaction between habitat and sex was detected in climbing performance. In addition, lizards from dunes bit harder than those from walls, although sexual differentiation was definitely the main factor driving variation in head functional morphology. Taking into account all the results, we found a complex interaction between natural and sexual selection on whole-organism performance, which are, in some cases, reflected in morphological variation.

Are mountain habitats becoming more suitable for generalist than cold-adapted lizards thermoregulation?

Mountain lizards are highly vulnerable to climate change, and the continuous warming of their habitats could be seriously threatening their survival. We aim to compare the thermal ecology and microhabitat selection of a mountain lizard, Iberolacerta galani, and a widely distributed lizard, Podarcis bocagei, in a montane area. Both species are currently in close syntopy in the study area, at 1,400 m above the sea level. We determined the precision, accuracy and effectiveness of thermoregulation, and the thermal quality of habitat for both species. We also compared the selection of thermal microhabitats between both species. Results show that I. galani is a cold-adapted thermal specialist with a preferred temperature range of 27.9–29.7 °C, while P. bocagei would be a thermal generalist, with a broader and higher preferred temperature range (30.1–34.5 °C). In addition, I. galani selects rocky substrates while P. bocagei selects warmer soil and leaf litter substrates. The thermal quality of the habitat is higher for P. bocagei than for I. galani. Finally, P. bocagei achieves a significantly higher effectiveness of thermoregulation (0.87) than I. galani (0.80). Therefore, these mountain habitat conditions seem currently more suitable for performance of thermophilic generalist lizards than for cold-specialist lizards.

Fin whale MDH-1 and MPI allozyme variation is not reflected in the corresponding DNA sequences

The appeal of genetic inference methods to assess population genetic structure and guide management efforts is grounded in the correlation between the genetic similarity and gene flow among populations. Effects of such gene flow are typically genomewide; however, some loci may appear as outliers, displaying above or below average genetic divergence relative to the genomewide level. Above average population, genetic divergence may be due to divergent selection as a result of local adaptation. Consequently, substantial efforts have been directed toward such outlying loci in order to identify traits subject to local adaptation. Here, we report the results of an investigation into the molecular basis of the substantial degree of genetic divergence previously reported at allozyme loci among North Atlantic fin whale (Balaenoptera physalus) populations. We sequenced the exons encoding for the two most divergent allozyme loci (MDH-1 and MPI) and failed to detect any nonsynonymous substitutions. Following extensive error checking and analysis of additional bioinformatic and morphological data, we hypothesize that the observed allozyme polymorphisms may reflect phenotypic plasticity at the cellular level, perhaps as a response to nutritional stress. While such plasticity is intriguing in itself, and of fundamental evolutionary interest, our key finding is that the observed allozyme variation does not appear to be a result of genetic drift, migration, or selection on the MDH-1 and MPI exons themselves, stressing the importance of interpreting allozyme data with caution. As for North Atlantic fin whale population structure, our findings support the low levels of differentiation found in previous analyses of DNA nucleotide loci.

Molecular survey of Apicomplexa in Podarcis wall lizards detects Hepatozoon, Sarcocystis, and Eimeria species

The occurrence of apicomplexan parasites in Podarcis sp. wall lizards from the Iberian Peninsula and Balearic islands was studied by amplification and sequencing of the 18S rRNA gene. Species from 3 genera, Hepatozoon , Sarcocystis , and Eimeria , were found. The phylogenetic analysis of the 18S rRNA gene provides unexpected insights into the evolutionary history of these parasites. All Hepatozoon spp. specimens were recovered as part of a clade already identified in lizards from North Africa. The Sarcocystis species, detected in Podarcis lilfordi from Cabrera Island in the Balearic Islands, appears related to Sarcocystis gallotiae , known only from endemic Gallotia sp. lizards from the Canary Islands. Based on the lack of snake predators on this island, this parasite presumably presents an atypical transmission cycle that uses the same host species as both intermediate and final host through cannibalism, like S. gallotiae . Eimeria sp. is reported for the first time from Podarcis spp. lizards. This study shows the power of detecting multiple different apicomplexan parasites through screening of tail tissue samples and blood drops that are often collected in reptiles for other purposes.

The use of a lacertid lizard as a model for reptile ecotoxicology studies: part 2--biomarkers of exposure and toxicity among pesticide exposed lizards

As part of a wider study examining the impacts of corn pesticides on lacertid lizards in north-western Portugal, we examined various physiological, biochemical, and histological biomarkers of exposure and effect among field populations of Podarcis bocagei. Biomarkers included body condition index, standard metabolic rate, locomotor performance, parasitization, glutathione oxidative pathways and related enzyme activity, lipid peroxidation and liver and testis histology. Few of the various biomarkers investigated provided statistically significant evidence of toxic effect. However, using a weight of evidence approach, we conclude that pesticides are affecting lizards living in the vicinity of pesticide exposed corn agriculture sites. Lizards from these locations present a profile of animals under metabolic stress with reduced condition indices, increased standard metabolic rate, lower incidence of hepatocyte vacuolation, altered iron metabolism, increased activation of GSH oxidation pathways, and even increased prevalence of hemoparasites.