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opencc-zeroApr 2024View details →

Data from: Genomic landscapes of divergence among island bird populations: evidence of parallel adaptation but at different loci?

When populations colonise new environments they may be exposed to novel selection pressures but also suffer from extensive genetic drift due to founder effects, small population sizes, and limited interpopulation gene flow. Genomic approaches enable us to study how these factors drive divergence, and disentangle neutral effects from differentiation at specific loci due to selection. Here, we investigate patterns of genetic diversity and divergence using whole-genome resequencing (> 22X coverage) in Berthelot's pipit (Anthus berthelotii), a passerine endemic to the islands of three north Atlantic archipelagos. Strong environmental gradients, including in pathogen pressure, across populations in the species range, make it an excellent system in which to explore traits important in adaptation and/or incipient speciation. Firstly, we quantify how genomic divergence accumulates across the speciation continuum, i.e., among Berthelot's pipit populations, between subspecies across archipelagos, and between Berthelot's pipit and its mainland ancestor, the tawny pipit (Anthus campestris). Across these colonisation timeframes (2.1 million – ca. 8,000 years ago), we identify highly differentiated loci within genomic islands of divergence and conclude that the observed distributions align with expectations for non-neutral divergence. Characteristic signatures of selection are identified in loci associated with craniofacial/bone and eye development, metabolism, and immune response between population comparisons. Interestingly, we find limited evidence for repeated divergence of the same loci across the colonisation range but do identify different loci putatively associated with the same biological traits in different populations, likely due to parallel adaptation. Incipient speciation across these island populations, in which founder effects and selective pressures are strong, may therefore be repeatedly associated with morphology, metabolism, and immune defence.

opencc-zeroDec 2021View details →

Rapid evolutionary divergence of a songbird population following recent colonization of an urban area

Colonization of a novel environment by a small group of individuals can lead to rapid evolutionary change, yet evidence of the relative contributions of neutral and selective factors in promoting divergence during the early stages of colonization remain scarce. Here, we use genome-wide SNP data to test the role of neutral and selective forces in driving the divergence of a unique urban population of the Oregon junco (Junco hyemalis oreganus), which became established on the campus of the University of California at San Diego (UCSD) in the early 1980s. Previous studies based on microsatellite loci documented significant genetic differentiation of the urban population as well as divergence in sexual signaling and life-history traits relative to nearby montane populations. However, the geographic origin of the colonization and the factors involved in the onset of the differentiation process remained uncertain. Our genome-wide SNP dataset confirmed the marked genetic differentiation of the UCSD population, and phylogenomic analysis identified the coastal subspecies pinosus from central California as its sister group instead of the neighboring mountain population. Demographic inference based on site frequency spectra recovered a time of separation from pinosus as recent as 20 to 32 generations, and a strong bottleneck at the time of colonization, suggesting a relevant role of founder effects and drift in the genetic differentiation of the UCSD population. However, we also found significant associations between environmental parameters characterizing the urban habitat of UCSD and genome-wide variants linked to functional genes. Some of the identified gene functions, like heavy metal detoxification and high-pitched hearing, have been reported as potentially adaptive in birds inhabiting urban environments. These results suggest that the interplay between founder events and directional selection may result in rapid shifts in both neutral and adaptive loci across the genome, and reveal the UCSD population of juncos as an ongoing case of divergence following the colonization of an anthropic environment.

opencc-zeroApr 2022View details →

Gene expression in male and female sticklebacks from populations with convergent and divergent throat coloration

Understanding of genetic mechanisms underlying variation in sexual dichromatism remains limited, especially for carotenoid-based colors. We addressed this knowledge gap in a gene expression study with threespine stickleback. We compared male and female throat tissues across five populations, including two in which female red coloration has evolved convergently. We found that the expression of individual genes, gene ontologies, and coexpression networks associated with red female color within a population differed between California and British Columbia populations, suggesting differences in underlying mechanisms. Comparing females from each of these populations to females from populations dominated by dull females, we again found extensive expression differences. For each population, genes and networks associated with female red color showed the same patterns for males only inconsistently. The functional roles of genes showing correlated expression with female color are unclear within populations, whereas genes highlighted through inter-population comparisons include some previously suggested to function in carotenoid pathways. Among these, the most consistent patterns involved TTC39B (Tetratricopeptide Repeat Domain 39B), which is within a known red coloration QTL in stickleback and implicated in red coloration in other taxa.

opencc-zeroApr 2022View details →

Gene expression plasticity, genetic variation and fatty acid remodelling in divergent populations of a tropical bivalve species: lipid profiles

Ocean warming challenges marine organisms' resilience, especially for species experiencing temperatures close to their upper thermal limits. A potential increase in thermal tolerance might significantly reduce the risk of population decline, which is intrinsically linked to variability in local habitat temperatures. Our goal was to assess the plastic and genetic potential of response to elevated temperatures in a tropical bivalve model, Pinctada margaritifera. We benefit from two ecotypes for which local environmental conditions are characterized by either large diurnal variations in the tide-pools (Marquesas archipelago) or lower mean temperature with stable to moderate seasonal variations (Gambier archipelago). We explored the physiological basis of individual responses to elevated temperature, genetic divergence as well as plasticity and acclimation by combining lipidomic and transcriptomic approaches. We show that P. margaritifera has certain capacities to adjust to long-term elevated temperatures that was thus far largely underestimated. Genetic variation across populations overlaps with gene expression and involves the mitochondrial respiration machinery, a central physiological process that contributes to species thermal sensitivity and their distribution ranges. Our results present evidence for acclimation potential in P. margaritifera and urge for longer term studies to assess populations resilience in face of climate change.

opencc-zeroSep 2022View details →

Genomic variation in the Black-throated Green Warbler (Setophaga virens) suggests divergence in a disjunct Atlantic Coastal Plain population (S. v. waynei)

We used whole-genome resequencing to estimate genetic distinctiveness in the Black-throated Green Warbler (Setophaga virens)—including S. v. waynei—a putative subspecies that occupies a narrow disjunct breeding range along the Atlantic Coastal Plain. Despite detecting low-global differentiation (FST = 0.027) across the entire species, the principal components analysis of genome-wide differences shows the main axis of variation separates S. v. waynei from all other S. v. virens samples. We also estimated a low-migration rate for S. v. waynei, but found them to be most similar to another disjunct population from the Piedmont of North Carolina, and detected evidence of a historical north-to-south geographic dispersal among the entire species. New World wood warblers (family: Parulidae) can exhibit strong phenotypic differences among species, particularly, in song and plumage; however, within-species variation in these warblers—often designated as subspecies—is much more subtle. The existence of several isolated Black-throated Green Warbler populations across its eastern North American breeding range offers an excellent opportunity to further understand the origin, maintenance, and conservation status of subspecific populations. Our results, combined with previously documented ecological and morphological distinctiveness, support that S. v. waynei be considered a distinct and recognized subspecies worthy of targeted conservation efforts.

opencc-zeroOct 2022View details →

G-matrix stability of clinally diverging populations of an annual weed

How phenotypic and genetic divergence among populations is influenced by the genetic architecture of those traits, and how microevolutionary changes in turn affect the within-population patterns of genetic variation, are of major interest to evolutionary biology. Work on Ipomoea hederacea, an annual vine, has found genetic clines in the means of a suite of ecologically important traits, including flowering time, growth rate, seed mass, and corolla width. Here we investigate the genetic (co)variances of these clinally varying traits in two northern range-edge and two central populations of Ipomoea hederacea to evaluate the influence of the genetic architecture on divergence across the range. We find 1) limited evidence for clear differentiation between Northern and Southern populations in the structure of G, suggesting overall stability of G across the range despite mean trait divergence and 2) that the axes of greatest variation (gmax) were unaligned with the axis of greatest multivariate divergence. Together these results indicate the role of the quantitative genetic architecture in constraining evolutionary response and divergence among populations across the geographic range.

opencc-by-4.0Jun 2017View details →

Fig. 2 in Genetic divergence of a newly documented population of the cecidogenous micromoth Eugnosta azapaensis Vargas & Moreira (Lepidoptera: Tortricidae) in the Atacama Desert of northern Chile

Fig. 2. Median joining network of the haplotypes of the DNA barcode fragment (658 bp) of the cytochrome c oxidase subunit I (COI) gene of Eugnosta azapaensis from Azapa (white) and Chaca (black) valleys, Atacama Desert of northern Chile. H1, H2, H3, H4 haplotypes; circles proportional to the frequency of the respective haplotype; numbers between circles indicates variable sites; gray triangle a median vector.

opencc-by-4.0Jun 2017View details →

Fig. 1 in Genetic divergence of a newly documented population of the cecidogenous micromoth Eugnosta azapaensis Vargas & Moreira (Lepidoptera: Tortricidae) in the Atacama Desert of northern Chile

Fig. 1. The study area in South America (left) and the sampling sites (right) of Eugnosta azapaensis in the Atacama Desert of northern Chile. The type locality Azapa Valley (black circle) and the newly documented locality Chaca Valley (black triangle).

FIGURE 5 in Population level genetic divergence and phylogenetic placement of Mexican shortfin mollies (Mollienesia: Poecilia: Poeciliidae)

FIGURE 5 | Cytochrome b (1,140 bp) mitochondrial gene Bayesian phylogeny, parsimony haplotype network, and sampling distribution of Atlantic taxa Poecilia limantouri (Turqouise-North of the Trans Mexican Volcanic Belt, forest green-South of the Trans Mexican Belt), P. sulphuraria/P. thermalis (yellow-South of the Isthmus of Tehuantepec), and P. mexicana (baby blue-North of the Trans Mexican Volcanic Belt, light green-South of the Trans Mexican Volcanic Belt, purple-North of the Isthmus of Tehuantepec, orange-South of the Isthmus of Tehuantepec) across geographic barriers along the Atlantic coast of Mexico. The phylogeny has Bayesian posterior values followed by bootstrap values with asterisks representing support of 95% or above. The Parsimony network values correspond to the haplotype values and are colored according by geographic locations separated by barriers; circle sizes correspond to the number of individuals with that haplotype (larger circles reflect more individuals), and black circles indicate unsampled haplotypes. The capital letters at the end of each sample represents the state of origin in Mexico, from North to South: NVL = Nuevo Leon, T = Tamaulipas, V = Veracruz, H = Hidalgo, Tb = Tabasco, C = Chiapas.

FIGURE 3 in Population level genetic divergence and phylogenetic placement of Mexican shortfin mollies (Mollienesia: Poecilia: Poeciliidae)

FIGURE 3 | Cytochrome b (1,140 bp) mitochondrial gene Bayesian phylogeny, parsimony haplotype network, and sampling distribution of Poecilia sphenops (aqua-Atlantic North of the Trans Mexican Volcanic Belt, pink- Balsas River Drainage, purple- Atlantic North of the Isthmus of Tehuantepec, red- Pacific North of the Isthmus of Tehuantepec, orange- Atlantic South of the Isthmus of Tehuantepec, and yellow- Pacific South of the Trans Mexican Volcanic Belt) across geographic barriers along the coasts of Mexico. The phylogeny has Bayesian posterior values followed by bootstrap values with asterisks representing support of 95% or above. The Parsimony network values correspond to the haplotype values and are colored according by geographic locations separated by barriers; circle sizes correspond to the number of individuals with that haplotype (larger circles reflect more individuals), and black circles indicate unsampled haplotypes. The capital letters at the end of each sample represents the state of origin in Mexico, from North to South: V = Veracruz, H = Hidalgo, M = Michoacan, G = Guerrero, O = Oaxaca, C = Chiapas.

FIGURE 4 in Population level genetic divergence and phylogenetic placement of Mexican shortfin mollies (Mollienesia: Poecilia: Poeciliidae)

FIGURE 4 | Cytochrome b (1,140 bp) mitochondrial gene Bayesian phylogeny, parsimony haplotype network, and sampling distribution of the Pacific sister taxa Poecilia butleri (blue-North of the Trans Mexican Volcanic Belt) and P. nelsoni (lime green-South of the Trans Mexican Volcanic Belt, pink- Balsas River Drainage, red- North of the Isthmus of Tehuantepec, and yellow- South of the Trans Mexican Volcanic Belt) across geographic barriers along the coast of Mexico. The phylogeny has Bayesian posterior values followed by bootstrap values with asterisks representing support of 95% or above. The Parsimony network values correspond to the haplotype values and are colored according by geographic locations separated by barriers; circle sizes correspond to the number of individuals with that haplotype (larger circles reflect more individuals), and black cirles indicate unsampled haplotypes. The capital letters at the end of each sample represents the state of origin in Mexico, from North to South: S = Sinaloa, N = Nayarit, J = Jalisco, Cl = Colima, M = Michoacan, G = Guerrero, O = Oaxaca, C = Chiapas.

FIGURE 1 in Population level genetic divergence and phylogenetic placement of Mexican shortfin mollies (Mollienesia: Poecilia: Poeciliidae)

FIGURE 1 | Sampling localities of species in the subgenus Mollienesia in Mexico and the main physiographic barriers throughout the country. The main physiographic barriers in Mexico from north to south are Northwestern Plains and Sierras, Sierra Madre Occidental, Sierra Madre Oriental, Gulf Coast Plain, Trans Mexican Volcanic Belt, Balsas Depression, Sierra Madre del Sur, Isthmus of Tehuantepec, and Sierra Madre de Chiapas.

FIGURE 2 in Population level genetic divergence and phylogenetic placement of Mexican shortfin mollies (Mollienesia: Poecilia: Poeciliidae)

FIGURE 2 | Bayesian tree from the MrBayes partitioned analysis of Poecilia spp. for two mitochondrial genes (Cyt b and ND2, 2187 base pairs) and one nuclear (RAG1, 1561 base pairs) rooted with other poeciliid outgroups. Species names in black pertain to species outside of Mexico and species names in red are species found within Mexico. Species labels represent slope: (A) = Atlantic, (P) = Pacific, and (B) = Bi-coastal. Nodal support shown (left to right; respectively): Bayesian Posterior Probabilities followed by RAxML bootstrap support values. Asterisks denote nodal support of 95% or above for the two methods, and a single asterisk at a node indicates support values of 95% or above for both methods. Nodes with no values present either had low values or were of little interest for this study. The capital letters at the end of each sample represents the state of origin in Mexico, from North to South: T = Tamaulipas, NVL = Nuevo León, V = Veracruz, H = Hidalgo, M = Michoacan, G = Guerrero, O = Oaxaca, Tb = Tabasco, C = Chiapas.

opencc-by-4.0Jun 2011View details →

Fig. 3 in Pleistocene karyotypic divergence in Hoplias malabaricus (Bloch, 1794) (Teleostei: Erythrinidae) populations in southeastern Brazil

Fig. 3. Variable Ag-NOR patterns in populations of H. malabaricus from middle rio Doce lakes. A-1, A-2, and B1, B-2 male and female NORs.

opencc-by-4.0Jun 2011View details →

Fig. 4 in Pleistocene karyotypic divergence in Hoplias malabaricus (Bloch, 1794) (Teleostei: Erythrinidae) populations in southeastern Brazil

Fig. 4. Patterns of GC-rich regions in H. malabaricus from middle rio Doce lakes. A - karyomorph B male, B - karyomorph B female, and C - karyomorph A.

opencc-zeroOct 2021View details →

Data and code for: Plastic and quantitative genetic divergence mirror environmental gradients among wild, fragmented populations of Impatiens capensis

Premise of the study: Habitat fragmentation generates molecular genetic divergence among isolated populations but few studies have assessed phenotypic divergence and fitness in populations where the genetic consequences of habitat fragmentation are known. Phenotypic divergence could reflect plasticity, local adaptation, and/or genetic drift. Methods: We examined patterns and potential drivers of phenotypic divergence among 12 populations of jewelweed (Impatiens capensis Meerb.) that show strong molecular genetic signals of isolation and drift among fragmented habitats. We measured morphological and reproductive traits in both maternal plants within natural populations and their self-fertilized progeny grown together in a common garden. We also quantified environmental divergence between home sites and the common garden. Key results: Populations with less molecular genetic variation expressed less maternal phenotypic variation. Progeny in the common garden converged in phenotypes relative to their wild mothers but retained among-population differences in morphology, survival, and reproduction. Among-population phenotypic variance was 3-10x greater in home sites than in the common garden for 6 of 7 morphological traits measured. Patterns of phenotypic divergence paralleled environmental gradients in ways suggestive of adaptation. Progeny resembled their mothers less as the environmental distance between their home site and the common garden increased. Conclusions: Despite strong molecular signatures of isolation and drift, phenotypic differences among these Impatiens populations appear to reflect both adaptive quantitative genetic divergence and plasticity. Quantifying the extent of local adaptation and plasticity and how these covary with molecular and phenotypic variation help us predict when populations may lose their adaptive capacity.

opencc-zeroJan 2023View details →

Phenotypic divergence of traits that mediate antagonistic and mutualistic interactions between island and continental populations of the tropical plant, Tribulus cistoides (Zygophyllaceae)

Premise: Island systems have long served as a model for evolutionary processes due to their unique species interactions. Many studies of the evolution of species interactions on islands have focused on endemic taxa. Fewer studies have focused on how antagonistic and mutualistic interactions shape the phenotypic divergence of widespread non-endemic species living on island populations. Methods: We used the widespread plant Tribulus cistoides (Zygophyllaceae) to test phenotypic divergence in traits that mediate antagonistic interactions with vertebrate granivores (birds) and mutualistic interactions with pollinators and how this is explained by bioclimatic variables. We used both herbarium specimens and field-collected samples to compare phenotypic divergence between continental and island populations. Results: Fruits from island populations were larger than on continents, but the presence of lower spines on mericarps was lower on islands. The presence of spines was largely explained by environmental variation among islands. Petal length was on average 9% smaller on island than continental populations, an effect that was especially accentuated on the Galápagos Islands. Conclusions: Tribulus cistoides exhibits phenotypic divergence between island and continental habitats for antagonistic traits (seed defence) and mutualistic traits (floral traits). Further, the evolution of phenotypic traits that mediate antagonistic and mutualistic interactions depended on the abiotic characteristics of specific islands. This study shows the potential of using a combination of herbarium and field samples for comparative studies on a globally distributed species to test phenotypic divergence on island habitats.

opencc-zeroJan 2023View details →

Whole genome demographic models indicate divergent effective population size histories shape contemporary genetic diversity gradients in a montane bumble bee

Understanding historical range shifts and population size variation provides important context for interpreting contemporary genetic diversity. Methods to predict changes in species distributions and model changes in effective population size (Ne) using whole genomes make it feasible to examine how temporal dynamics influence diversity across populations. We investigate Ne variation and climate-associated range shifts to examine the origins of a previously observed latitudinal heterozygosity gradient in the bumble bee Bombus vancouverensis Cresson (Hymenoptera: Apidae: Bombus Latreille) in western North America. We analyze whole genomes from a latitude-elevation cline using sequentially Markovian coalescent models of Ne through time to test whether relatively low diversity in southern high-elevation populations is a result of long-term differences in Ne. We use Maxent models of the species range over the last 130,000 years to evaluate range shifts and stability. Ne fluctuates with climate across populations, but more genetically diverse northern populations have maintained greater Ne over the late Pleistocene and experienced larger expansions with climatically favorable time periods. Northern populations also experienced larger bottlenecks during the last glacial period which matched the loss of range area near these sites, however, bottlenecks were not sufficient to erode diversity maintained during periods of large Ne. A genome sampled from an island population indicated a severe postglacial bottleneck, indicating that large recent post-glacial declines are detectable if they have occurred. Genetic diversity was not related to niche stability or glacial-period bottleneck size. Instead, spatial expansions and increased connectivity during favorable climates likely maintain diversity in the north while restriction to high elevations maintains relatively low diversity despite greater stability in southern regions. Results suggest genetic diversity gradients reflect long-term differences in Ne dynamics and also emphasize the unique effects of isolation on insular habitats for bumble bees. Patterns are discussed in the context of conservation under climate change.