Tetrathyridia in an endemic lizard from Chile: molecular evidence for South America.

Mesocestoides is a controversial tapeworm with significant lack of data related to systematics and life cycles. This helminth has an indirect life cycle with vertebrates, mostly carnivorous mammals, as definitive hosts. Theoretically, a coprophagous arthropod would be the first intermediate host, and herptiles, mammals, and birds, which prey on these insects, would represent the second intermediate hosts. However, recent evidence suggests that this life cycle would require only two hosts, with no arthropods involved. In the Neotropics, although there are records of mammals and reptiles as hosts for Mescocestoides, no molecular analyses have been performed. This work aimed to record an additional intermediate host and molecularly characterize the isolated larvae. Thus, 18 braided tree iguanas (Liolaemus platei) from Northern Chile were collected and dissected during 2019. One lizard was parasitized by three morphotypes of larvae compatible with tetrathyridia of Mescocestoides. To achieve its specific identity, a molecular approach was performed: 18S rRNA and 12S rRNA loci were amplified through cPCR. The inferred phylogenies confirmed the morphological diagnosis and stated that all morphotypes were conspecifics. The sequences for both loci formed a monophyletic clade with high nodal support, representing a sister taxon to Mescocestoides clade C. This study represents the first molecular characterization of any taxon of Mescocestoides from the Neotropics. Future surveys from potential definitive hosts would help to elucidate its life cycle. Furthermore, an integrative taxonomic approach is required in additional studies from the Neotropical region, which would contribute to a better understanding of the evolutionary relationships of this genus.

Connecting genomic patterns of local adaptation and niche suitability in teosintes.

The central abundance hypothesis predicts that local adaptation is a function of the distance to the centre of a species' geographic range. To test this hypothesis, we gathered genomic diversity data from 49 populations, 646 individuals and 33,464 SNPs of two wild relatives of maize, the teosintes Zea mays ssp. parviglumis and Zea. mays. ssp. mexicana. We examined the association between the distance to their climatic and geographic centroids and the enrichment of SNPs bearing signals of adaptation. We identified candidate adaptive SNPs in each population by combining neutrality tests and cline analyses. By applying linear regression models, we found that the number of candidate SNPs is positively associated with niche suitability, while genetic diversity is reduced at the limits of the geographic distribution. Our results suggest that overall, populations located at the limit of the species' niches are adapting locally. We argue that local adaptation to this limit could initiate ecological speciation processes and facilitate adaptation to global change.

The Strait of Gibraltar as a major biogeographic barrier in Mediterranean conifers: a comparative phylogeographic survey.

The Strait of Gibraltar (SG) is reputed for being both a bridge and a geographic barrier to biological exchanges between Europe and Africa. Major genetic breaks associated with this strait have been identified in various taxa, but it is unknown whether these disjunctions have been produced simultaneously or by independent biogeographic processes. Here, the genetic structure of five conifers distributed on both sides of the SG was investigated using mitochondrial (nad1 b/c, nad5-1, nad5-4 and nad7-1) and chloroplast (Pt1254, Pt15169, Pt30204, Pt36480, Pt71936 and Pt87268) DNA markers. The distribution of genetic variation was partially congruent between types of markers within the same species. Across taxa, there was a significant overlapping between the SG and the genetic breaks detected, especially for the four Tertiary species surveyed (Abies pinsapo complex, Pinus nigra, Pinus pinaster and Taxus baccata). For most of these taxa, the divergence of populations across the SG could date back to long before the Pleistocene glaciations. However, their strongly different cpDNA G(ST) and R(ST) values point out that they have had dissimilar population histories, which might include contrasting amounts of pollen-driven gene flow since their initial establishment in the region. The fifth species, Pinus halepensis, was genetically depauperated and homogenous on both sides of the SG. A further analysis of nuclear DNA sequences with coalescent-based isolation with migration models suggests a Pleistocene divergence of P. halepensis populations across the SG, which is in sharp contrast with the pre-Pleistocene divergence dates obtained for P. pinaster. Altogether, these results indicate that the genetic breaks observed across this putative biogeographical barrier have been produced by independent evolutionary processes related to the biological history of each individual species instead of a common vicariant phenomenon.

Comparative population dynamics of the bug Mepraia spinolai, a sylvatic vector of Chagas' disease, in different hosts.

The aim of this work was to determine the impact of specific hosts on a population of Mepraia spinolai (Porter) (Hemiptera, Reduviidae), a sylvatic vector of Chagas' disease in Chile. We assessed whether a recently introduced host could be an important epidemiological factor in maintaining Chagas' disease in Chile. The study stressed the variations in survival, individual weight and fecundity in the insect population when the vector was raised with a species-specific food supply. The study compared the European rabbit Oryctolagus cuniculus, introduced in Chile

Cross-species amplification of mitochondrial DNA sequence-tagged-site markers in conifers: the nature of polymorphism and variation within and among species in Picea.

Primers previously developed to amplify specific non-coding regions of the mitochondrial genome in Angiosperms, and new primers for additional non-coding mtDNA regions, were tested for their ability to direct DNA amplification in 12 conifer taxa and to detect sequence-tagged-site (STS) polymorphisms within and among eight species in Picea. Out of 12 primer pairs, nine were successful at amplifying mtDNA in most of the taxa surveyed. In conifers, indels and substitutions were observed for several loci, allowing them to distinguish between families, genera and, in some cases, between species within genera. In Picea, interspecific polymorphism was detected for four loci, while intraspecific variation was observed for three of the mtDNA regions studied. One of these (SSU rRNA V1 region) exhibited indel polymorphisms, and the two others ( nad1 intron b/c and nad5 intron1) revealed restriction differences after digestion with Sau3AI (PCR-RFLP). A fourth locus, the nad4L- orf25 intergenic region, showed a multibanding pattern for most of the spruce species, suggesting a possible gene duplication. Maternal inheritance, expected for mtDNA in conifers, was observed for all polymorphic markers except the intergenic region nad4L- orf25. Pooling of the variation observed with the remaining three markers resulted in two to six different mtDNA haplotypes within the different species of Picea. Evidence for intra-genomic recombination was observed in at least two taxa. Thus, these mitotypes are likely to be more informative than single-locus haplotypes. They should be particularly useful for the study of biogeography and the dynamics of hybrid zones.

Population genetic analysis of the genes APOE, APOB(3'VNTR) and ACE in some black and Amerindian communities from Colombia.

A population genetic study was carried out with the APOE, APOB and ACE loci in 17 Colombian human populations. Ten of them were Amerindian communities coming from the northeastern part of Colombia, Pacific region, Eastern Plains and Amazonia. Six were black populations from Providence Island, Caribbean and Pacific coasts. Finally, the Mestizo population of Bogota was studied as well. The APOE and ACE loci were in Hardy-Weinberg equilibrium, whereas the APOB locus was not studied in all populations. The genetic heterogeneity was substantially greater among the Amerindian populations (G(ST) = 0.059) than in the Afrocolombian populations (G(ST) = 0.009). Also the gene flow population pair estimates were so much higher among the Afrocolombian populations (Nm = 49.08 +/- 43.07) than among Amerindian populations (Nm = 9.66 +/- 18.04). Different phylogenetic and multivariant analyses showed that the Amerindian populations analyzed were clustered in three different arrays: one constituted by the Colombian northeastern and Pacific populations, the second one by the two Amazon populations (Coreguaje and Nukak) and the last one by the Yuco (the unique Caribbe-speaking population among those studied). The latter population was highly divergent from a genetic point of view from the remainder Amerindian populations studied. By using the Mantel test, the existence of a positive and significant correlation between the genetic and geographical distances found among Amerindian populations was demonstrated. This fact was not observed among the Afrocolombian populations. Nevertheless, an isolation-by-distance Slatkin analysis test did not show a significant clear structure of this special pattern among the Indian tribes studied.

Contrasting evolutionary forces driving population structure at expressed sequence tag polymorphisms, allozymes and quantitative traits in white spruce.

Patterns of variation in quantitative characters and genetic markers were compared among six regional populations of white spruce [Picea glauca (Moench) Voss]. Although some phenotypic characters were correlated with latitude (r = 0.791), longitude (r = -0.796) and precipitation during the growing season (r = 0.789), variability at genetic markers was not correlated with geographical or bioclimatic variables, and followed neutral expectations. Estimates of genetic diversity and population differentiation for 14 allozymes (translated regions of coding genes) were essentially indistinguishable from those observed for 11 expressed sequence tag polymorphisms (ESTPs) from untranslated regions of coding genes. Variation among populations for quantitative traits such as eighth year height (Q(ST) = 0.082), thirteenth year height (Q(ST) = 0.069), total wood density (Q(ST) = 0.102) and date of budset (Q(ST) = 0.246), was greater than for allozymes (G(ST) = 0.014) and ESTPs (G(ST) = 0.019). These trends suggest a strong adaptive response in quantitative traits, contrasting to allozymes and ESTPs where no selective response could be detected and where populations appeared to be essentially in a migration-drift equilibrium.