Aim
The role that geography plays in promoting speciation by spatially isolating populations has been studied extensively, but less attention has been devoted to assessing the role of isolation by ...time mediated by spatial variation in climate as a mechanism promoting population divergence. Gene flow between populations differing in their reproductive schedules might be reduced relative to that between populations with overlapping breeding seasons, potentially leading to genetic divergence. Assuming that precipitation influences reproductive schedules, we explored the effect of asynchronous precipitation regimes on intraspecific genetic divergence. In addition, we examined whether microevolutionary processes are reflected in macroevolutionary patterns by assessing whether regions with more asynchronous precipitation across space have higher frog species richness and have experienced greater speciation rates than regions with more spatially synchronous precipitation regimes.
Location
Central and South America.
Taxon
Anurans: across 38 species of Neotropical frogs.
Methods
For microevolutionary analyses, we assessed the relationship between spatial asynchrony in precipitation and mitochondrial DNA genetic divergence accounting for ecological connectivity using multiple regression and phylogenetic meta‐analyses. For macroevolutionary analyses, we assessed the relationship between species richness, speciation rates estimated from a comprehensive molecular phylogeny, and the degree of spatial asynchrony in precipitation using generalized linear models.
Results
We found that spatial asynchrony in precipitation is positively associated with genetic differentiation in 39% of the species tested, resulting in a weak cross‐species effect. However, the effect of asynchrony in precipitation on population divergence seems not to scale to macroevolutionary patterns because spatial asynchrony in precipitation was not associated with geographical patterns of species richness nor speciation rates.
Main Conclusions
Our results indicate that asynchronous breeding may promote genetic divergence even in the absence of geographical barriers in species where breeding is associated with water availability, but such effects may not be stable enough through time to influence macroevolutionary patterns.
Colombia hosts the second highest amphibian species diversity on Earth, yet its fauna remains poorly studied, especially using molecular genetic techniques. We present the results of the first ...wide-scale DNA barcoding survey of anurans of Colombia, focusing on a transect across the Eastern Cordillera. We surveyed 10 sites between the Magdalena Valley to the west and the eastern foothills of the Eastern Cordillera, sequencing portions of the mitochondrial 16S ribosomal RNA and cytochrome oxidase subunit 1 (CO1) genes for 235 individuals from 52 nominal species. We applied two barcode algorithms, Automatic Barcode Gap Discovery and Refined Single Linkage Analysis, to estimate the number of clusters or "unconfirmed candidate species" supported by DNA barcode data. Our survey included ~7% of the anuran species known from Colombia. While barcoding algorithms differed slightly in the number of clusters identified, between three and ten nominal species may be obscuring candidate species (in some cases, more than one cryptic species per nominal species). Our data suggest that the high elevations of the Eastern Cordillera and the low elevations of the Chicamocha canyon acted as geographic barriers in at least seven nominal species, promoting strong genetic divergences between populations associated with the Eastern Cordillera.
Leishmania is a unicellular protozoan that has a limited transcriptional control and mostly uses post-transcriptional regulation of gene expression, although the molecular mechanisms of the process ...are still poorly understood. Treatments of leishmaniasis, pathologies associated with Leishmania infections, are limited due to drug resistance. Here, we report dramatic differences in mRNA translation in antimony drug-resistant and sensitive strains at the full translatome level. The major differences (2431 differentially translated transcripts) were demonstrated in the absence of the drug pressure supporting that complex preemptive adaptations are needed to efficiently compensate for the loss of biological fitness once they are exposed to the antimony. In contrast, drug-resistant parasites exposed to antimony activated a highly selective translation of only 156 transcripts. This selective mRNA translation is associated with surface protein rearrangement, optimized energy metabolism, amastins upregulation, and improved antioxidant response. We propose a novel model that establishes translational control as a major driver of antimony-resistant phenotypes in Leishmania.
Using species ranges, in particular those derived from species distribution models (SDM), to obtain characteristics of the species’ niche such as temperature tolerances is tempting. Over the past ...decade the literature has seen the increase in the use of SDMs based on locality data and spatially explicit datasets (climate, vegetation etc.). Furthermore, several studies have explored climatic niche evolution and niche conservatism using temperature and precipitation extracted from the resulting models in a phylogenetic context. However, species´ fundamental niches (set of abiotic conditions in which a species can live) are often incompletely characterized in SDMs, reconstructed mainly based on spotty locality data (about species presence and rarely including absence data). Indeed, a species´ realized niche, the actually occupied conditions where a species live, may be a subset of their fundamental niche due to lack of habitat availability, constraints on dispersion, and biotic interactions. Here, we produced SDMs for 50 species of neotropical reptiles and amphibians and compared extreme temperature estimates extracted from the modelled area (model-inferred) with thermo-physiological estimates of critical temperatures (physiology-inferred). When comparing experimental critical thermal maximum and minimums with temperature values extracted from the estimated range, we found a general pattern of maximum temperatures experienced that are cooler than the species maximum tolerances, and minimum temperatures close to or even colder than their minimum tolerances. Characterizing niche traits from SDMs is dangerous because SDMs are not representing the fundamental niche of species as measured with thermal physiology limits and they are also not deviating from the fundamental niche in a predictable way.
Aim: The frog genus Rheobates (Anura: Aromobatidae) is endemic to mid-elevations in the Colombian Andes. Our aim was to evaluate the role of the northern Andean high peaks and the low Magdalena ...Valley in creating barriers to dispersal and promoting vicariance within Rheobates. Location: Three disjunct mid-elevation flanks of the northern Colombian Andes: the eastern and western flanks of the Eastern Cordillera, separated by high mountain peaks, and the eastern flank of the Central Cordillera, separated from the Eastern Cordillera by the arid Magdalena Valley. Methods: We analysed mitochondrial and nuclear DNA sequences from 37 individuals of Rheobates to infer their phylogenetic relationships, divergence times and ancestral areas. We used species distribution models to test the role of climatic variables in determining the present geographical boundaries of the species. Results: The phylogeny of Rheobates is largely predicted by geography, with one population from the eastern flank of the Eastern Cordillera sharing a most recent common ancestor with all other Rheobates 21 million years ago (Ma; 95% credible interval 31-10 Ma). Populations in the Central Cordillera were monophyletic, isolated across the Magdalena Valley with a divergence time estimated at 13 Ma (19-7 Ma). We also detected one recent crossing of the Eastern Cordillera, along with unanticipated latitudinal phylogeographical structure within the western flank of the Eastern Cordillera. Environmental niche tests indicated that the Magdalena Valley and the high peaks of the Eastern Cordillera are significant environmental barriers for Rheobates populations. Main conclusions: Diversification in Rheobates coincided with the early Miocene uplift of Colombia's Eastern Cordillera and the hypothesized onset of aridity in the Magdalena Valley during the middle Miocene. Our study offers broad support for the classic mountain orogeny model of vicariant divergence, but suggests that lowland habitat heterogeneity also played a long-term role in promoting vicariance, despite a long history of palaeoclimatic fluctuations.
Isthmian Central America (ICA) is one of the most biodiverse regions in the world, hosting an exceptionally high number of species per unit area. ICA was formed <25 million years ago and, ...consequently, its biotic assemblage is relatively young and derived from both colonization and in situ diversification. Despite intensive taxonomic work on the local fauna, the potential forces driving genetic divergences and ultimately speciation in ICA remain poorly studied. Here, we used a landscape genetics approach to test whether isolation by distance, topography, habitat suitability, or environment drive the genetic diversity of the regional frog assemblage. To this end, we combined data on landscape features and mitochondrial DNA sequence variation for nine codistributed amphibian species with disparate life histories. In five species, we found that at least one of the factors tested explained patterns of genetic divergence. However, rather than finding a general pattern, our results revealed idiosyncratic responses to historical and ecological processes, indicating that intrinsic life-history characteristics may determine the effect of different drivers of isolation on genetic divergence in ICA. Our work also suggests that the convergence of several factors promoting isolation among populations over a heterogeneous landscape might maximize genetic differentiation, despite short geographical distances. In conclusion, abiotic factors and geographical features have differentially affected the genetic diversity across the regional frog assemblage. Much more complex models (i.e., considering multiple drivers), beyond simple vicariance of Caribbean and Pacific lineages, are needed to better understand the evolutionary history of ICA's diverse biotas.
There are two main competing hypotheses (vicariance and vertical ecotones) that attempt to explain the tremendous diversity of the tropical Andes. We test these hypotheses at the intraspecific level ...by analyzing mitochondrial and nuclear DNA sequences from 24 populations of the high Andean frog,
Dendropsophus labialis (Anura: Hylidae). This species displays geographic variation in a number of phenotypic traits. Most of these traits covary with elevation, while few vary along the horizontal (latitudinal) axis. We found that, both, vicariance and elevation had important effects on the genetic differentiation in this species. We detected two highly divergent clades along the south–north axis using independent information from mitochondrial and nuclear genes, suggesting that this differentiation was the result of long-term barriers to gene flow rather than stochastic processes. We hypothesize mechanisms for
D. labialis strong differentiation in light of geological and paleoenvironmental models of evolution in the northern Andean highlands.
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•The nominal species N. meridionalis is not a single species, but a complex of at least five cryptic species.•Divergence time within the N. meridionalis complex is old, splitting back ...into the early-mid Miocene.•The topographic reorganization during the Miocene was an important factor in promoting genetic divergence.•Lineages within the N. meridionalis complex show evidence for non-stationary isolation by distance.•Niche conservatism seems to be an important mechanism that promoted geographic fragmentation in the group.
The Cerrado is a wide Neotropical savanna with tremendously high endemic diversity. Yet, it is not clear what the prevalent processes leading to such diversification are. We used the Cerrado-endemic lizard Norops meridionalis to investigate the main abiotic factors that promoted genetic divergence, the timings of these divergence events, and how these relate to cryptic diversity in the group. We sequenced mitochondrial and nuclear genes from 21 sites of N. meridionalis to generate species tree, divergence time estimations, and estimate species limits. We also performed population-level analysis and estimated distribution models to test the roles of niche conservatism and divergence in the group diversification. We found that N. meridionalis is composed by at least five cryptic species. Divergence time estimations suggest that the deepest branches split back into the early-mid Miocene, when most of the geophysical activity of the Cerrado took place. The deep divergences found in N. meridionalis suggest that beta anoles invaded South America much earlier than previously thought. Recent published evidence supports this view, indicating that the Panama gap closed as early as 15mya, allowing for an early invasion of Norops into South America. The spatial pattern of diversification within N. meridionalis follows a northwest–southeast direction, which is consistent across several species of vertebrates endemic to the Cerrado. Also, we found evidence for non-stationary isolation by distance, which occurs when genetic differentiation depends on space. Our preliminary data in two out of five lineages suggest that niche conservatism is an important mechanism that promoted geographic fragmentation in the group.
Most global hotspots of biodiversity and endemism are in montane regions. One explanation is that montane regions have intrinsically higher speciation rates than lowland regions because complex ...mountain topography and climate variation facilitate genetic isolation among populations. Here, we ask from an intraspecific perspective whether frog species whose haplotypes are connected by topographically/climatically complex regions display strong genetic isolation (greater scaled genetic distances), compared with species whose haplotypes are connected by less complex regions. We analysed published DNA sequences of several frog species from tropical Central and South America for the mitochondrial cob, cox1 and 16S rRNA genes. Pairwise genetic distances among haplotypes within each species were scaled to the geographic distances between each pair of haplotypes. Topographic complexity was positively correlated with scaled genetic distances, and isolation‐by‐resistance was supported only in species from more topographically complex regions. This suggests that heterogeneous topographies increase landscape resistance, which in turn favours the appearance of isolation‐by‐resistance. Moreover, we found that the potential barriers that restrict gene flow within species are more closely related to factors associated with temperature and topography than to precipitation.
parasites cause leishmaniasis, one of the most epidemiologically important neglected tropical diseases.
exhibits a high ability of developing drug resistance, and drug resistance is one of the main ...threats to public health, as it is associated with increased incidence, mortality, and healthcare costs. The antimonial drug is the main historically implemented drug for leishmaniasis. Nevertheless, even though antimony resistance has been widely documented, the mechanisms involved are not completely understood. In this study, we aimed to identify potential metabolite biomarkers of antimony resistance that could improve leishmaniasis treatment. Here, using
promastigotes as the biological model, we showed that the level of response to antimony can be potentially predicted using
H-NMR-based metabolomic profiling. Antimony-resistant parasites exhibited differences in metabolite composition at the intracellular and extracellular levels, suggesting that a metabolic remodeling is required to combat the drug. Simple and time-saving exometabolomic analysis can be efficiently used for the differentiation of sensitive and resistant parasites. Our findings suggest that changes in metabolite composition are associated with an optimized response to the osmotic/oxidative stress and a rearrangement of carbon-energy metabolism. The activation of energy metabolism can be linked to the high energy requirement during the antioxidant stress response. We also found that metabolites such as proline and lactate change linearly with the level of resistance to antimony, showing a close relationship with the parasite's efficiency of drug resistance. A list of potential metabolite biomarkers is described and discussed.
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