Pedro A. Sosa

Allozyme diversity in three endemic species of Cistus (Cistaceae) from the Canary Islands: intraspecific and interspecific comparisons and implications for genetic conservation.

Patterns of variation at 13 isozyme loci were examined in 11 populations in three Cistus species strictly endemic to the Canary Islands. Cistus osbaeckiaefolius and C. chinamadensis display low levels of isozyme variation associated with moderate to high interpopulation differentiation, which probably arose through historical bottlenecks in a landscape of habitat fragmentation, grazing, and human influence. By contrast, C. symphytifolius ranks among the subset of narrow endemics with high levels of isozyme variation and features different degrees of genetic structuring that are closely associated with taxonomic ascription. Low interpopulation differentiation in var. leucophyllus is possibly a reflection of its recent origin or of moderate levels of gene flow between its populations. High interpopulation differentiation in var. symphytifolius probably arose due to slight ecological differences between populations coupled with low levels of gene flow. Interpretation of neighbor-joining trees in the light of geological data substantiates the hypothesis that C. symphytifolius (or a very close relative) might be the ancestor of the other stands of Cistus in the islands. Conservation implications of our survey are the identification of the two populations of C. chinamadensis with the highest allele and genotype richness for preservation on genetic grounds and advice to prevent artificial gene flow in this taxon lest it might disrupt locally adapted gene combinations. All populations of C. osbaeckiaefolius should be given conservation priority on ecological grounds despite their genetic depauperation.

Molecular evidence of hybridisation between the endemic Phoenix canariensis and the widespread P. dactylifera with Random Amplified Polymorphic DNA (RAPD) markers

Abstract.We used RAPD markers to test whether morphologically intermediate individuals between the Canarian endemic Phoenix canariensis and the widespread P. dactylifera correspond to hybrids. Consistent with previous allozyme evidence, the scarcity of appropriate RAPD markers to distinguish P. dactylifera and P. canariensis indicated a close genetic relationship among these species. Only two of the 54 ten-mer primers (OPM-8 and OPK-14) tested in 221 individuals from 7 localities in different islands enabled us to unambiguously identify both species. While P. canariensis possesses two exclusive monomorphic bands of 1000 bp and 750 bp (for OPM-8 and OPM-14, respectively), dactylifera is characterised by two bands of 900 bp and 950 bp for the same primers. The additivity of these taxon-specific bands in the individuals that were morphologically intermediate provided, for the first time, firm evidence for their hybrid origin. Because these hybridisation capabilities pose clear threats to the survival of the endemic P. canariensis and some individuals that had been morphologically characterised as pure P. canariensis revealed later a hybrid nature in the RAPD analysis, we suggest that RAPD markers be used to estimate the possible incidence of introgression in the scarce extant natural populations of P. canariensis. This procedure will provide a straightforward means to select target populations to implement the “in situ” conservation strategies suggested previously on the basis of allozyme research.

Patterns of genetic diversity in Phoenix canariensis, a widespread oceanic palm (species) endemic from the Canarian archipelago

Understanding how genetic diversity is structured on oceanic island taxa requires the integration of physical, biological and anthropomorphic factors. Founder effects coupled with limited dispersal over sea barriers typically result in low levels of genetic variation in island populations. In widespread species, restriction in gene flow across large areas leads to patterns of isolation by distance (IBD), but recent population-based studies indicate that genetic structure on islands can be complex even at local scales. Here, we investigated the patterns of genetic variation in a widespread island palm (Phoenix canariensis) displaying reproductive syndromes associated with extensive dispersal (wind pollination and zoochory). Genetic variation was assessed at eight nuclear microsatellite loci in 330 individuals of 15 Canarian populations. Our results showed that levels of within-population genetic diversity in P. canariensis depend on the island considered, with a strong decreasing pattern from the easternmost and oldest island to the westernmost and youngest islands. A Mantel test supported a stepping-stone model of differentiation across the archipelago that fits the sequence of island emergence, and results from ABC and clustering analyses also corresponded with this progression rule. In addition, our analyses were congruent with the idea that the only large population found on Lanzarote has an anthropogenic origin. Despite the high dispersal potential of P. canariensis, our analyses suggest that the geographical configuration of the Canary Islands and a relatively recent pattern of differentiation across islands appear to have had a primary influence on the genetic structure of this island taxon.

Species delimitation and conservation genetics of the Canarian endemic Bethencourtia (Asteraceae)

Bethencourtia Choisy ex Link is an endemic genus of the Canary Islands and comprises three species. Bethencourtia hermosae and Bethencourtia rupicola are restricted to La Gomera, while Bethencourtia palmensis is present in Tenerife and La Palma. Despite the morphological differences previously found between the species, there are still taxonomic incongruities in the group, with evident consequences for its monitoring and conservation. The objectives of this study were to define the species differentiation, perform population genetic analysis and propose conservation strategies for Bethencourtia. To achieve these objectives, we characterized 10 polymorphic SSR markers. Eleven natural populations (276 individuals) were analyzed (three for B. hermosae, five for B. rupicola and three for B. palmensis). The results obtained by AMOVA, PCoA and Bayesian analysis on STRUCTURE confirmed the evidence of well-structured groups corresponding to the three species. At the intra-specific level, B. hermosae and B. rupicola did not show a clear population structure, while B. palmensis was aggregated according to island of origin. This is consistent with self-incompatibility in the group and high gene flow within species. Overall, the genetic diversity of the three species was low, with expected heterozygosity values of 0.302 (B. hermosae), 0.382 (B. rupicola) and 0.454 (B. palmensis). Recent bottleneck events and a low number of individuals per population are probably the causes of the low genetic diversity. We consider that they are naturally rare species associated with specific habitats. The results given in this article will provide useful information to assist in conservation genetics programs for this endemic genus.

Reproductive strategy and ploidy determine the genetic variability of Sorbus aria

Sorbus aria (L.) Crantz (common whitebeam) from the Canary Islands has not been characterised genetically. We analysed the genetic variability of 184 individuals belonging to seven natural populations of S. aria from the Canarian Archipelago and the Iberian Peninsula. Our main aims were to obtain essential information to enable the exploration of the genetic relationship between populations from the Canary Islands and the Iberian Peninsula; to establish the existence of a spatial genetic structure and formulate appropriate management and conservation genetics strategies. Genetic variation was analysed using nine polymorphic microsatellite loci. The Canary Island populations (triploids) were found to have very low genetic variability and to be considerably differentiated from the populations from the peninsula (diploid and triploid), although with a connection to the Sierra Nevada population in the south of the Peninsula. This population, in turn, had many different genotypes, which is indicative of the existence of various origins. The level of genetic diversity was higher in all-diploid populations, which, in addition, presented a greater interpopulation gene flow, possibly the result of a prevalence of sexual reproduction. On the other hand, the triploid populations presented lower levels of genetic variability, with a significant degree of fixed heterozygosity, possibly due to asexual reproduction, mainly by apomixis. The reproductive biology and ploidy appear to be responsible for the levels of genetic variability in S. aria.

Characterization of six microsatellite loci in Myrica faya (Myricaceae) and cross amplification in the endangered endemic M. rivas-martinezii in Canary Islands, Spain

Six novel polymorphic microsatellite markers were isolated from enriched libraries in Myrica faya Ait., recently renamed Morella faya, (fayatree, firetree, or firebush) in order to examine the genetic diversity in natural populations. Also, test cross-specific amplification and genetic diversity in Myrica rivas-martinezii, which is endemic on the Canary islands. Microsatellite loci were screened in 225 individuals of both species from different islands of the Canarian archipelago. All markers were successfully amplified from both Myrica species, with an average number of 6.5 and 9.3 alleles per locus in M. rivas-martinezii and M. faya, respectively. There was no evidence for linkage disequilibrium between loci, and the probability of null alleles ranged from 0.01 to 0.17.

The restoration of the endangered Sambucus palmensis after 30 years of conservation actions in the Garajonay National Park: genetic assessment and niche modeling

The translocation of individuals or the reinforcement of populations are measures in the genetic rescue of endangered species. Although it can be controversial to decide which and how many individuals must be reintroduced, populations can benefit from reinforcements. Sambucus palmensis is a critically endangered endemic to the Canary Islands. During the past 30 years, the Garajonay National Park (La Gomera) has carried out an intensive program of translocations using cuttings, due to the low germination rates of seeds. To assess the effect of the restorations on the population genetics of S. palmensis in La Gomera, we collected 402 samples from all the restored sites and all known natural individuals, which were genotyped with seven microsatellite markers. In addition, we conducted a species distribution modeling approach to assess how restorations fit the ecological niche of the species. Results show that there is a high proportion of clone specimens due to the propagation method, and the natural clonal reproduction of the species. Nonetheless, the observed heterozygosity has increased with the restorations and there still are private alleles and unique genotypes in the natural populations that have not been considered in the restorations. The population of Liria constitutes a very important genetic reservoir for the species. To optimize future reintroductions, we have proposed a list of specimens that are suitable for the extraction of seeds or cuttings in a greenhouse, as well as new suitable areas obtained by the species distribution models.

Alpine species in dynamic insular ecosystems through time: conservation genetics and niche shift estimates of the endemic and vulnerable Viola cheiranthifolia

BACKGROUND AND AIMS Alpine oceanic ecosystems are considered amongst the most ephemeral and restricted habitats, with a biota highly vulnerable to climate changes and disturbances. As an example of an alpine insular endemic, the past and future population genetic structure and diversity, and the future distribution of Viola cheiranthifolia (Violaceae), endemic to Tenerife (Canary Islands), were estimated. The main goals were to predict distribution changes of this alpine oceanic plant under climate change, and to assist in actions for its conservation. METHODS To perform population genetic analysis, 14 specific microsatellite markers and algorithms which considered the polyploid condition of V. cheiranthifolia were employed. The niche modelling approach incorporated temperature gradients, topography and snow cover maps. Models were projected into climate change scenarios to assess the extent of the altitudinal shifts of environmental suitability. Finally, simulations were performed to predict whether the environmental suitability loss will affect the genetic diversity of populations. KEY RESULTS Viola cheiranthifolia presents short dispersal capacity, moderate levels of genetic diversity and a clear population genetic structure divided into two main groups (Teide and Las Cañadas Wall), showing signs of recolonization dynamics after volcanic eruptions. Future estimates of the distribution of the study populations also showed that, despite being extremely vulnerable to climate change, the species will not lose all its potential area in the next decades. The simulations to estimate genetic diversity loss show that it is correlated to suitability loss, especially in Las Cañadas Wall. CONCLUSIONS The low dispersal capacity of V. cheiranthifolia, coupled with herbivory pressure, mainly from rabbits, will make its adaptation to future climate conditions in this fragile alpine ecosystem difficult. Conservation actions should be focused on herbivore control, population reinforcement and surveillance of niche shifts, especially in Guajara, which represents the oldest isolated population and a genetic reservoir for the species.