"Candidatus Accumulibacter" population structure in enhanced biological phosphorus removal sludges as revealed by polyphosphate kinase genes

We investigated the fine-scale population structure of the "Candidatus Accumulibacter" lineage in enhanced biological phosphorus removal (EBPR) systems using the polyphosphate kinase 1 gene (ppk1) as a genetic marker. We retrieved fragments of "Candidatus Accumulibacter" 16S rRNA and ppk1 genes from one laboratory-scale and several full-scale EBPR systems. Phylogenies reconstructed using 16S rRNA genes and ppk1 were largely congruent, with ppk1 granting higher phylogenetic resolution and clearer tree topology and thus serving as a better genetic marker than 16S rRNA for revealing population structure within the "Candidatus Accumulibacter" lineage. Sequences from at least five clades of "Candidatus Accumulibacter" were recovered by ppk1-targeted PCR, and subsequently, specific primer sets were designed to target the ppk1 gene for each clade. Quantitative real-time PCR (qPCR) assays using "Candidatus Accumulibacter"-specific 16S rRNA and "Candidatus Accumulibacter" clade-specific ppk1 primers were developed and conducted on three laboratory-scale and nine full-scale EBPR samples and two full-scale non-EBPR samples to determine the abundance of the total "Candidatus Accumulibacter" lineage and the relative distributions and abundances of the five "Candidatus Accumulibacter" clades. The qPCR-based estimation of the total "Candidatus Accumulibacter" fraction as a proportion of the bacterial community as measured using 16S rRNA genes was not significantly different from the estimation measured using ppk1, demonstrating the power of ppk1 as a genetic marker for detection of all currently defined "Candidatus Accumulibacter" clades. The relative distributions of "Candidatus Accumulibacter" clades varied among different EBPR systems and also temporally within a system. Our results suggest that the "Candidatus Accumulibacter" lineage is more diverse than previously realized and that different clades within the lineage are ecologically distinct.     

Monitoring the impact of bioaugmentation on the start up of biological phosphorus removal in a laboratory scale activated sludge ecosystem

The acclimatisation of activated sludge to enhanced biological phosphorus removal (EBPR) conditions requires a period of about 40–100 days but its output remains hazardous. The impact of bioaugmentation on the start-up of a laboratory scale EBPR sequencing batch reactor was evaluated by process parameters measurement and microbial community dynamics monitoring using 16S rDNA targeted polymerase chain reaction-single strand conformation polymorphism electrophoresis (PCR-SSCP). Bioaugmentation: (1) speeded up the installation of good and stable EBPR in the bioaugmented reactor by about 15 days; (2) correlated with the transient enrichment of the sludge in the added microbial populations; and (3) favoured the long-term enrichment of the sludge in the phosphorus-accumulating organism (PAO) Candidatus Accumulibacter phosphatis. However, despite a lag time period, the control non-bioaugmented reactor ended up with comparable reactor parameters and microbial community evolution, suggesting that the same PAO populations were already present from the beginning in the original non-P-accumulating seed sludge. The potential of a true installation of the added microbial populations within the bioaugmented reactor compared to their substitution by indigenous similar populations is discussed. Competition between PAOs and the antagonistic glycogen accumulating organism Candidatus Competibacter phosphatis is also highlighted during EBPR start-up.     

Net P-removal deterioration in enriched PAO sludge subjected to permanent aerobic conditions

Recently, some research in the field of enhanced biological phosphorus removal (EBPR) has been focused on studying systems where the electron donor (substrate) and the electron acceptor (nitrate or oxygen) are present simultaneously. This can occur, for example, in a full scale wastewater treatment plant during heavy rainfall periods when the anaerobic hydraulic retention time is temporarily shortened. To study this situation that could induce EBPR failure, the operation of a sequencing batch reactor (SBR) working under alternating anaerobic-aerobic conditions with an enriched EBPR population (50% Candidatus Accumulibacter phosphatis and less than 1% Candidatus Competibacter phosphatis) was shifted to strict aerobic operation. Seven cycle studies were performed during the 11 days of aerobic operation. Net P-removal was observed in this aerobic SBR during the first 4 days of operation but the system could not achieve net-P removal after this period, although the microbial composition, in terms of percentage of Accumulibacter and Competibacter, did not change significantly. The observed changes in the different compounds analysed (phosphorus, acetate, glycogen and PHB) as well as in the OUR profile indicate that metabolic changes are produced for the adaptation of PAO to aerobic conditions.     

Global ubiquity and local endemism of free‐living terrestrial protists: phylogeographic assessment of the streptophyte alga Klebsormidium

Despite considerable research attention during the last 10 years, the distribution and biogeography of protists remain as highly controversial issues. The presumably huge population sizes and unlimited dispersal capabilities should result in protist ubiquity. However, recent molecular investigations suggest that protist communities exhibit strong biogeographic patterns. Here, we examined the biogeographic pattern of a very common green algal genus Klebsormidium. We evaluated the geographic distribution of rbcL genotypes for 190 isolates sampled in six sampling regions located in Europe, North America and Asia. Measures of correlation between genetic and geographic distance matrices revealed a differential distribution pattern on two geographic levels. Globally, the populations were genetically homogeneous; locally, the genotypes were patchily distributed. We hypothesized that a local fine‐scale structuring of genotypes may be caused by various ecological factors, in particular, by the habitat differentiation of particular genotypes. Our investigations also identified a large number of new, previously unrecognized lineages. A total of 44 genotypes were identified and more than 66% of these were reported for the first time.     

Dynamics of microbial community structure of and enhanced biological phosphorus removal by aerobic granules cultivated on propionate or acetate

Aerobic granules are dense microbial aggregates with the potential to replace floccular sludge for the treatment of wastewaters. In bubble-column sequencing batch reactors, distinct microbial populations dominated propionate- and acetate-cultivated aerobic granules after 50 days of reactor operation when only carbon removal was detected. Propionate granules were dominated by Zoogloea (40%), Acidovorax, and Thiothrix, whereas acetate granules were mainly dominated by Thiothrix (60%). Thereafter, an exponential increase in enhanced biological phosphorus removal (EBPR) activity was observed in the propionate granules, but a linear and erratic increase was detected in the acetate ones. Besides Accumulibacter and Competibacter, other bacterial populations found in both granules were associated with Chloroflexus and Acidovorax. The EBPR activity in the propionate granules was high and stable, whereas EBPR in the acetate granules was erratic throughout the study and suffered from a deterioration period that could be readily reversed by inducing hydrolysis of polyphosphate in presumably saturated Accumulibacter cells. Using a new ppk1 gene-based dual terminal-restriction fragment length polymorphism (T-RFLP) approach revealed that Accumulibacter diversity was highest in the floccular sludge inoculum but that when granules were formed, propionate readily favored the dominance of Accumulibacter type IIA. In contrast, acetate granules exhibited transient shifts between type I and type II before the granules were dominated by Accumulibacter type IIA. However, ppk1 gene sequences from acetate granules clustered separately from those of propionate granules. Our data indicate that the mere presence of Accumulibacter is not enough to have consistently high EBPR but that the type of Accumulibacter determines the robustness of the phosphate removal process.     

Determinants of distribution and prevalence of avian malaria in blue tit populations across Europe: separating host and parasite effects

Although avian malarial parasites are globally distributed, the factors that affect the geographical distribution and local prevalence of different parasite lineages across host populations or species are still poorly understood. Based on the intense screening of avian malarial parasites in nine European blue tit populations, we studied whether distribution ranges as well as local adaptation, host specialization and phylogenetic relationships can determine the observed prevalences within populations. We found that prevalence differed consistently between parasite lineages and host populations, indicating that the transmission success of parasites is lineage specific but is partly shaped by locality-specific effects. We also found that the lineage-specific estimate of prevalence was related to the distribution range of parasites: lineages found in more host populations were generally more prevalent within these populations. Additionally, parasites with high prevalence that were also widely distributed among blue tit populations were also found to infect more host species. These findings suggest that parasites reaching high local prevalence can also realize wide distribution at a global scale that can have further consequences for host specialization. Although phylogenetic relationships among parasites did not predict prevalence, we detected a close match between a tree based on the geographic distance of the host populations and the parasite phylogenetic tree, implying that neighbouring host populations shared a related parasite fauna.     

Phylogenetic plant community structure along elevation is lineage specific

The trend of closely related taxa to retain similar environmental preferences mediated by inherited traits suggests that several patterns observed at the community scale originate from longer evolutionary processes. While the effects of phylogenetic relatedness have been previously studied within a single genus or family, lineage‐specific effects on the ecological processes governing community assembly have rarely been studied for entire communities or flora. Here, we measured how community phylogenetic structure varies across a wide elevation gradient for plant lineages represented by 35 families, using a co‐occurrence index and net relatedness index (NRI). We propose a framework that analyses each lineage separately and reveals the trend of ecological assembly at tree nodes. We found prevailing phylogenetic clustering for more ancient nodes and overdispersion in more recent tree nodes. Closely related species may thus rapidly evolve new environmental tolerances to radiate into distinct communities, while older lineages likely retain inherent environmental tolerances to occupy communities in similar environments, either through efficient dispersal mechanisms or the exclusion of older lineages with more divergent environmental tolerances. Our study illustrates the importance of disentangling the patterns of community assembly among lineages to better interpret the ecological role of traits. It also sheds light on studies reporting absence of phylogenetic signal, and opens new perspectives on the analysis of niche and trait conservatism across lineages.     

Phylogeographic analysis of the Bufo gargarizans species complex: a revisit

Using mtDNA sequencing and allozyme electrophoresis data, we tested the "vicariance followed by dispersal" hypothesis of the Bufo gargarizans species group and re-evaluated the species status in the general lineages species concept. A phylogenetic analysis suggested that dispersal, instead of vicariance, dominated the history of the species group. There was a general trend of west to east dispersal, while some lineages from the east subsequently returned to the west. The secondary admixture of those previously allopatric lineages produced substantial levels of sympatric genetic diversity, often as high as 7.0% pairwise difference within populations. The phylogenetic hypothesis does not support the current two species designation. Neither B. andrewsi nor B. gargarizans represents an independent evolutionary lineage, and monophyletic groups did not correspond to geographically discrete groups. Allozyme data also failed to reveal any fixed allelic difference among the populations. Therefore, we recommend regarding the complex as a single species, Bufo gargarizans, without subspecies division.     

Expanding our view of genomic diversity in Candidatus Accumulibacter clades

Enhanced biological phosphorus removal (EBPR) is an important industrial wastewater treatment process mediated by polyphosphate‐accumulating organisms (PAOs). Members of the genus Candidatus Accumulibacter are one of the most extensively studied PAO as they are commonly enriched in lab‐scale EBPR reactors. Members of different Accumulibacter clades are often enriched through changes in reactor process conditions; however, the two currently sequenced Accumulibacter genomes show extensive metabolic similarity. Here, we expand our understanding of Accumulibacter genomic diversity through recovery of eight population genomes using deep metagenomics, including seven from phylogenetic clades with no previously sequenced representative. Comparative genomic analysis revealed a core of shared genes involved primarily in carbon and phosphorus metabolism; however, each Accumulibacter genome also encoded a substantial number of unique genes (> 700 genes). A major difference between the Accumulibacter clades was the type of nitrate reductase encoded and the capacity to perform subsequent steps in denitrification. The Accumulibacter clade IIF genomes also contained acetaldehyde dehydrogenase that may allow ethanol to be used as carbon source. These differences in metabolism between Accumulibacter genomes provide a molecular basis for niche differentiation observed in lab‐scale reactors and may offer new opportunities for process optimization.     

Determinants of hierarchical genetic structure in Atlantic salmon populations: environmental factors vs. anthropogenic influences

Disentangling the effects of natural environmental features and anthropogenic factors on the genetic structure of endangered populations is an important challenge for conservation biology. Here, we investigated the combined influences of major environmental features and stocking with non‐native fish on the genetic structure and local adaptation of Atlantic salmon (Salmo salar) populations. We used 17 microsatellite loci to genotype 975 individuals originating from 34 French rivers. Bayesian analyses revealed a hierarchical genetic structure into five geographically distinct clusters. Coastal distance, geological substrate and river length were strong predictors of population structure. Gene flow was higher among rivers with similar geologies, suggesting local adaptation to geological substrate. The effect of river length was mainly owing to one highly differentiated population that has the farthest spawning grounds off the river mouth (up to 900 km) and the largest fish, suggesting local adaptation to river length. We detected high levels of admixture in stocked populations but also in neighbouring ones, implying large‐scale impacts of stocking through dispersal of non‐native individuals. However, we found relatively few admixed individuals suggesting a lower fitness of stocked fish and/or some reproductive isolation between wild and stocked individuals. When excluding stocked populations, genetic structure increased as did its correlation with environmental factors. This study overall indicates that geological substrate and river length are major environmental factors influencing gene flow and potential local adaptation among Atlantic salmon populations but that stocking with non‐native individuals may ultimately disrupt these natural patterns of gene flow among locally adapted populations.     

Anthropogenic dispersion of selected germplasm creates a geographic mosaic of contrasting maternal lineages in <Emphasis Type="Italic">Crescentia cujete</Emphasis> from Mesoamerica

The modification of the genetic/phenotypic composition of plant populations through artificial selection occurs both through time and space. We analyzed the role of human dispersal on the geographic distribution of maternal lineages of Crescentia cujete in Mesoamerica. We sampled 28 homegarden (224 individuals) and 12 wild populations (159 individuals). Semi-structured interviews provided information on the origin of cultivated trees. Six chloroplast microsatellites allowed for the identification of 21 haplotypes, four of them exclusively in 83% of homegarden trees. Wild haplotypes from local C. cujete and Crescentia alata were found at low frequencies (17%) under cultivation. Cultivated and wild haplotypes constituted two different haplogroups. Accordingly, barriers to seed dispersal were detected among neighboring cultivated and wild populations. Recorded events of human dispersal of cuttings and seeds attaining up to >?200 km agreed with homegardens’ lower diversity (Nei’s h?=?0.55, dropping to 0.32 when excluding wild haplotypes). Wild populations displayed high diversity (h?=?0.71) and isolation by distance, in agreement with physiographic provinces. Our results support the native status of wild C. cujete and a Pre-Columbian introduction of cultivated lineages that generated a novel genetic mosaic superimposed on native maternal lineages. The results reveal the active role of farmers in maintaining the identity of cultivated lineages through time, while chloroplast capture from local congeners has increased the diversity of maternal lineages under cultivation. Additional data are needed on the origins of cultivated lineages, but our results contribute new insights into tree domestication in this center of crop diversity.     

Effects of patch number and dispersal patterns on population dynamics and synchrony

In this paper, we examine the effects of patch number and different dispersal patterns on dynamics of local populations and on the level of synchrony between them. Local population renewal is governed by the Ricker model and we also consider asymmetrical dispersal as well as the presence of environmental heterogeneity. Our results show that both population dynamics and the level of synchrony differ markedly between two and a larger number of local populations. For two patches different dispersal rules give very versatile dynamics. However, for a larger number of local populations the dynamics are similar irrespective of the dispersal rule. For example, for the parameter values yielding stable or periodic dynamics in a single population, the dynamics do not change when the patches are coupled with dispersal. High intensity of dispersal does not guarantee synchrony between local populations. The level of synchrony depends also on dispersal rule, the number of local populations, and the intrinsic rate of increase. In our study, the effects of density-independent and density-dependent dispersal rules do not show any consistent difference. The results call for caution when drawing general conclusions from models of only two interacting populations and question the applicability of a large number of theoretical papers dealing with two local populations.     

Density‐dependent fitness,not dispersal movements,drives temporal variation in spatial genetic structure in dark‐eyed juncos (Junco hyemalis)

Some studies have found that dispersal rates and distances increase with density, indicating that density‐dependent dispersal likely affects spatial genetic structure. In an 11‐year mark–recapture study on a passerine, the dark‐eyed junco, we tested whether density affected dispersal distance and/or fine‐scale spatial genetic structure. Contrary to expectations, we found no effect of predispersal density on dispersal distance or the proportion of locally produced juveniles returning to the population from which they hatched. However, even though density did not affect dispersal distance or natal return rates, we found that density still did affect spatial genetic structure. We found significant positive spatial genetic structure at low densities of (postdispersal) adults but not at high densities. In years with high postdispersal (adult) densities that also had high predispersal (juvenile) densities in the previous year, we found negative spatial genetic structure, indicating high levels of dispersal. We found that density also affected fitness of recruits, and fitness of immigrants, potentially linking these population parameters with the spatial genetic structure detected. Immigrants and recruits rarely nested in low postdispersal density years. In contrast, in years with high postdispersal density, recruits were common and immigrants had equal success to local birds, so novel genotypes diluted the gene pool and effectively eliminated positive spatial genetic structure. In relation to fine‐scale spatial genetic structure, fitness of immigrants and new recruits is poorly understood compared to dispersal movements, but we conclude that it can have implications for the spatial distribution of genotypes in populations.     

Evidence for fine-scale habitat specialisation in an invasive weed

Aims As an exotic species colonises a new continent, it must overcome enormous environmental variation in its introduced range. Local adaptation of introduced species has frequently been observed at the continent scale, particularly in response to latitudinal climatic variation. However, significant environmental heterogeneity can also exist at the landscape scale. A small number of studies have provided evidence that introduced species may also be capable of phenotypic and genetic differentiation at much smaller spatial scales. For example, previously we found US agricultural and non-agricultural populations of Sorghum halepense (Johnsongrass) to be phenotypically and genetically distinct. In this study, we investigated whether this phenotypic differentiation of agricultural and non-agricultural populations of S. halepense is the result of fine-scale local specialisation.Methods We surveyed a nationally collected S. halepense germplasm panel and also collected neighbouring agricultural and non-agricultural sub-populations of S. halepense at four sites throughout Western Virginia, USA, raising seedlings in common conditions mimicking both agricultural and non-agricultural habitats.Important findings At the national scale, we found evidence of habitat differentiation but not specialisation. However, at the local scale, we found evidence of specialisation in two of the four local populations to non-agricultural habitat, but no evidence of specialisation to agricultural habitat. These results show that local specialisation is a possible, but not guaranteed consequence of kilometre-scale habitat heterogeneity in invasive species. This finding contributes to a growing awareness of the importance of fine-scale local adaptation in the ecology and management of introduced and weedy species.     

Biogeographic scenarios for the diversification of a widespread Neotropical species,Glossophaga soricina (Chiroptera: Phyllostomidae)

In order to contribute to the understanding of the effect of geological and climatic changes on species diversification in the Neotropics, we employed molecular techniques to study the population dynamics of the glossophagine bat Glossophaga soricina, a widespread species in the Neotropical region. We aimed to assess the dispersal and distribution of mtDNA lineages of G. soricina and evaluate the possible effect of vicariant events in the population history and dynamics. Glossophaga soricina presented two main highly supported mtDNA lineages, which diverged between ～2.4 and 5 million years ago, probably following a vicariant event caused by the Andes final uplift. The lower sea level during Pleistocene glaciations also made possible the occupation of Jamaica after an event of dispersion over the Caribbean Sea, although past climatic fluctuations had little effect over population dynamics of G. soricina. Our results corroborate the idea that the Andes uplift played an important role in the evolution of Neotropical biodiversity. In this context we suggest that geographic events causing large scale environmental disjunction, such as the uplift of mountains, are more likely to restrict gene flow amongst populations of tolerant species with broad geographic range than local climate driven environmental changes.     

Warming induces synchrony and destabilizes experimental pond zooplankton metacommunities

The spatial insurance hypothesis predicts that intermediate rates of dispersal between patches in a metacommunity allow species to track favourable conditions, preserving diversity and stabilizing biomass at local and regional scales. However, theory is unclear as to whether dispersal will provide spatial insurance when environmental conditions are changing directionally. In particular, increased temperatures as a result of climate change are expected to cause synchronous growth or decline across species and communities, and this has the potential to erode the stabilizing compensatory dynamics facilitated by dispersal. Here we report on an experimental test of how dispersal affects the diversity and stability of metacommunities under warming using replicate two‐patch pond zooplankton metacommunities. Initial differences in local community composition and abiotic conditions were established by seeding each patch in the metacommunities with plankton and sediment from one of two natural ponds that differed in water chemistry and species composition. We exposed metacommunities to a 2°C increase in average ambient temperature, crossed with three rates of dispersal (none, intermediate, high). In ambient conditions, intermediate dispersal rates preserved diversity and stabilized metacommunities by promoting spatially asynchronous fluctuations in biomass, especially between local populations of the dominant genus, Ceriodaphnia. However, warming synchronized their populations so that these effects of dispersal were lost. Furthermore, because the stabilizing effect of dispersal was primarily due to asynchronous fluctuations between populations of a single genus, metacommunity biomass was stabilized, but dispersal did not stabilize local community biomass. Our results show that dispersal can preserve diversity and provide stability to metacommunities, but also show that this benefit can be eroded when warming is directional and synchronous across patches of a metacommunity, as is expected with climate warming.     

Beta diversity of rock-restricted cichlid fishes in Lake Malawi: importance of environmental and spatial factors

The rock-restricted cichlid fish assemblages of Lake Malawi exhibit high spatial diversity in their species composition and relative abundance. However the extent to which this is due to the effects of local environmental differences, dispersal limitation of constituent taxa, and the assignment of allopatric populations to species is uncertain. We examined the factors associated with diversity within an assemblage from the north-western shores, encompassing a spatial scale of 170 km. For both the whole assemblage, and all constituent species-complexes, spatial variance in community structure was significantly dependent upon both geographic distances between locations and local habitat variables. Pronounced effects of distance indicate limited dispersal, but our results also show that that the spatial variance explained by geographic distance alone was strongly linked to proportion of allopatric populations within a species-complex with species status. Thus, the taxonomic status of allopatric populations underlies, at least partially, the biogeographical structure of this assemblage. Substrate composition and habitat depth were also significant determinants of community structure, although spatial variance attributed to these variables was less than that associated with distance alone. Substantial unexplained variance may be a consequence of the effects of unmeasured habitat variables, high ecological similarity between co-occurring species, stochastic influences on population abundance, and the effects of local adaptation. Despite low spatial variance explained by the assessed environmental variables, significant environmental influence on cichlid assemblage structure across a wide spatial scale indicates that even slight future environmental changes may have the capacity to significantly alter species composition.     

Genetic structure and seed-mediated dispersal rates of an endangered shrub in a fragmented landscape: a case study for Juniperus communis in northwestern Europe

Background

Population extinction risk in a fragmented landscape is related to the differential ability of the species to spread its genes across the landscape. The impact of landscape fragmentation on plant population dynamics will therefore vary across different spatial scales. We quantified successful seed-mediated dispersal of the dioecious shrub Juniperus communis in a fragmented landscape across northwestern Europe by using amplified fragment length polymorphism (AFLP) markers. Furthermore we investigated the genetic diversity and structure on two spatial scales: across northwestern Europe and across Flanders (northern Belgium). We also studied whether seed viability and populations size were correlated with genetic diversity.

Results

Unexpectedly, estimated seed-mediated dispersal rates were quite high and ranged between 3% and 14%. No population differentiation and no spatial genetic structure were detected on the local, Flemish scale. A significant low to moderate genetic differentiation between populations was detected at the regional, northwest European scale (PhiPT = 0.10). In general, geographically nearby populations were also genetically related. High levels of within-population genetic diversity were detected but no correlation was found between any genetic diversity parameter and population size or seed viability.

Conclusions

In northwestern Europe, landscape fragmentation has lead to a weak isolation-by-distance pattern but not to genetic impoverishment of common juniper. Substantial rates of successful migration by seed-mediated gene flow indicate a high dispersal ability which could enable Juniperus communis to naturally colonize suitable habitats. However, it is not clear whether the observed levels of migration will suffice to counterbalance the effects of genetic drift in small populations on the long run.     

Using phylogeographic approaches to analyse the dispersal history,velocity and direction of viral lineages — Application to rabies virus spread in Iran

Recent years have seen the extensive use of phylogeographic approaches to unveil the dispersal history of virus epidemics. Spatially explicit reconstructions of viral spread represent valuable sources of lineage movement data that can be exploited to investigate the impact of underlying environmental layers on the dispersal of pathogens. Here, we performed phylogeographic inference and applied different post hoc approaches to analyse a new and comprehensive data set of viral genomes to elucidate the dispersal history and dynamics of rabies virus (RABV) in Iran, which have remained largely unknown. We first analysed the association between environmental factors and variations in dispersal velocity among lineages. Second, we present, test and apply a new approach to study the link between environmental conditions and the dispersal direction of lineages. The statistical performance (power of detection, false‐positive rate) of this new method was assessed using simulations. We performed phylogeographic analyses of RABV genomes, allowing us to describe the large diversity of RABV in Iran and to confirm the cocirculation of several clades in the country. Overall, we estimate a relatively high lineage dispersal velocity, similar to previous estimates for dog rabies virus spread in northern Africa. Finally, we highlight a tendency for RABV lineages to spread in accessible areas associated with high human population density. Our analytical workflow illustrates how phylogeographic approaches can be used to investigate the impact of environmental factors on several aspects of viral dispersal dynamics.