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opencc-zeroDec 2012View details →

Data from: Examining the full effects of landscape heterogeneity on spatial genetic variation: a multiple matrix regression approach for quantifying geographic and ecological isolation

Understanding the effects of landscape heterogeneity on spatial genetic variation is a primary goal of landscape genetics. Ecological and geographic variables can contribute to genetic structure through geographic isolation, in which geographic barriers and distances restrict gene flow, and ecological isolation, in which gene flow among populations inhabiting different environments is limited by selection against dispersers moving between them. Although methods have been developed to study geographic isolation in detail, ecological isolation has received much less attention, partly because disentangling the effects of these mechanisms is inherently difficult. Here, I describe a novel approach for quantifying the effects of geographic and ecological isolation using multiple matrix regression with randomization. I explored the parameter space over which this method is effective using a series of individual-based simulations and found that it accurately describes the effects of geographic and ecological isolation over a wide range of conditions. I also applied this method to a set of real-world datasets to show that ecological isolation is an often overlooked but important contributor to patterns of spatial genetic variation and to demonstrate how this analysis can provide new insights into how landscapes contribute to the evolution of genetic variation in nature.

Data from: Forest trees in human modified landscapes: ecological and genetic drivers of recruitment failure in Dysoxylum malabaricum (Meliaceae)

Tropical agro-forest landscapes are global priority areas for biodiversity conservation. Little is known about the ability of these landscapes to sustain large late successional forest trees upon which much forest biodiversity depends. These landscapes are subject to fragmentation and additional habitat degradation which may limit tree recruitment and thus compromise numerous ecosystem services including carbon storage and timber production. Dysoxylum malabaricum is a large canopy tree species in the Meliaceae, a family including many important tropical timber trees. This species is found in highly fragmented forest patches within a complex agro-forest landscape of the Western Ghats biodiversity hot spot, South India. In this paper we combined a molecular assessment of inbreeding with ecological and demographic data to explore the multiple threats to recruitment of this tree species. An evaluation of inbreeding, using eleven microsatellite loci in 297 nursery-reared seedlings collected form low and high density forest patches embedded in an agro-forest matrix, shows that mating between related individuals in low density patches leads to reduced seedling performance. By quantifying habitat degradation and tree recruitment within these forest patches we show that increasing canopy openness and the increased abundance of pioneer tree species lead to a general decline in the suitability of forest patches for the recruitment of D. malabaricum. We conclude that elevated inbreeding due to reduced adult tree density coupled with increased degradation of forest patches, limit the recruitment of this rare late successional tree species. Management strategies which maintain canopy cover and enhance local densities of adult trees in agro-forest mosaics will be required to ensure D. malabaricum persists in these landscapes. Our study highlights the need for a holistic understanding of the incipient processes that threaten populations of many important and rare tropical tree species in human dominated agro-forest landscapes.

Data from: Resource allocation during ontogeny is influenced by genetic, developmental, and ecological factors in the horned beetle, Onthophagus taurus

Resource allocation trade-offs arise when developing organs are in competition for a limited pool of resources to sustain growth and differentiation. Such competition may constrain the maximal size to which structures can grow and may force a situation in which the evolutionary elaboration of one structure may only be possible at the expense of another. However, recent studies have called into question both the consistency and evolutionary importance of resource allocation trade-offs. This study focuses on a well-described trade-off between the horns and eyes of Onthophagus beetles and assesses the degree to which it is influenced by genetic, developmental and ecological conditions. Contrary to expectations, we observed that trade-off signatures (i) were mostly absent within natural populations, (ii) mostly failed to match naturally evolved divergences in horn investment among populations, (iii) were subject to differential changes in F1 populations derived from divergent field populations and (iv) remained largely unaffected by developmental genetic manipulations of horn investment. Collectively, our results demonstrate that populations subject to different ecological conditions exhibit different patterns of, and differential plasticity in, resource allocation. Further, variation in ecological conditions, rather than canalized developmental mechanisms, may determine whether and to what degree morphological structures engage in resource allocation trade-offs.

opencc-zeroDec 2016View details →

Data from: Population genetic and field ecological analyses return similar estimates of dispersal over space and time in an endangered amphibian

The explosive growth of empirical population genetics has seen a proliferation of analytical methods leading to a steady increase in our ability to accurately measure key population parameters, including genetic isolation, effective population size, and gene flow in natural systems. Assuming they yield similar results, population genetic methods offer an attractive complement to, or replacement of, traditional field ecological studies. However, empirical assessments of the concordance between direct field ecological and indirect population genetic studies of the same populations are uncommon in the literature. In this study, we investigate genetic isolation, rates of dispersal, and population sizes for the endangered California tiger salamander, Ambystoma californiense, across multiple breeding seasons in an intact vernal pool network. We then compare our molecular results to a previously published study based on multi-year, mark-recapture data from the same breeding sites. We found that field and genetic estimates of population size were only weakly correlated, but dispersal rates were remarkably congruent across studies and methods. In fact, dispersal probability functions derived from genetic data and traditional field ecological data were a significant match, suggesting that either method can be used effectively to assess population connectivity. These results provide one of the first explicit tests of the correspondence between landscape genetic and field ecological approaches to measuring functional population connectivity and suggest that even single-year genetic samples can return biologically meaningful estimates of natural dispersal and gene flow.

Data from: The role of geography and ecology in shaping repeated patterns of morphological and genetic differentiation between European minnows (Phoxinus phoxinus) from the Pyrenees and the Alps

Neutral and selective processes can drive repeated patterns of evolution in different groups of populations experiencing similar ecological gradients. In this paper, we used a combination of nuclear and mitochondrial DNA markers, as well as geometric morphometrics, to investigate repeated patterns of morphological and genetic divergence of European minnows in two mountain ranges: the Pyrenees and the Alps. European minnows (Phoxinus phoxinus) are cyprinid fish inhabiting most freshwater bodies in Europe, including those in different mountain ranges that could act as major geographical barriers to gene flow. We explored patterns of P. phoxinus phenotypic and genetic diversification along a gradient of altitude common to the two mountain ranges, and tested for isolation by distance (IBD), isolation by environment (IBE) and isolation by adaptation (IBA). The results indicated that populations from the Pyrenees and the Alps belong to two well differentiated, reciprocally monophyletic mtDNA lineages. Substantial genetic differentiation due to geographical isolation within and between populations from the Pyrenees and the Alps was also found using rapidly evolving AFLPs markers (isolation by distance or IBD), as well as morphological differences between mountain ranges. Also, morphology varied strongly with elevation and so did genetic differentiation to a lower extent. Despite moderate evidence for IBE and IBA, and therefore of repeated evolution, substantial population heterogeneity was found at the genetic level, suggesting that selection and population specific genetic drift act in concert to affect genetic divergence.

Data from: Ecological opportunities and specializations shaped genetic divergence in a highly mobile marine top predator

Environmental conditions can shape genetic and morphological divergence. Release of new habitats during historical environmental changes was a major driver of evolutionary diversification. Here, forces shaping population structure and ecotype differentiation ('pelagic' and 'coastal') of bottlenose dolphins in the North-east Atlantic were investigated using complementary evolutionary and ecological approaches. Inference of population demographic history using approximate Bayesian computation indicated that coastal populations were likely founded by the Atlantic pelagic population after the Last Glacial Maxima probably as a result of newly available coastal ecological niches. Pelagic dolphins from the Atlantic and the Mediterranean Sea likely diverged during a period of high productivity in the Mediterranean Sea. Genetic differentiation between coastal and pelagic ecotypes may be maintained by niche specializations, as indicated by stable isotope and stomach content analyses, and social behaviour. The two ecotypes were only weakly morphologically segregated in contrast to other parts of the World Ocean. This may be linked to weak contrasts between coastal and pelagic habitats and/or a relatively recent divergence. We suggest that ecological opportunity to specialize is a major driver of genetic and morphological divergence. Combining genetic, ecological and morphological approaches is essential to understanding the population structure of mobile and cryptic species.

opencc-zeroDec 2012View details →

Data from: Parallel tagged next-generation sequencing on pooled samples – a new approach for population genetics in ecology and conservation

Next-generation sequencing (NGS) on pooled samples has already been broadly applied in human medical diagnostics and plant and animal breeding. However, thus far it has been only sparingly employed in ecology and conservation, where it may serve as a useful diagnostic tool for rapid assessment of species genetic diversity and structure at the population level. Here we undertake a comprehensive evaluation of the accuracy, practicality and limitations of parallel tagged amplicon NGS on pooled population samples for estimating species population diversity and structure. We obtained 16S and Cyt b data from 20 populations of Leiopelma hochstetteri, a frog species of conservation concern in New Zealand, using two approaches – parallel tagged NGS on pooled population samples and individual Sanger sequenced samples. Data from each approach were then used to estimate two standard population genetic parameters, nucleotide diversity (π) and population differentiation (FST), that enable population genetic inference in a species conservation context. We found a positive correlation between our two approaches for population genetic estimates, showing that the pooled population NGS approach is a reliable, rapid and appropriate method for population genetic inference in an ecological and conservation context. Our experimental design also allowed us to identify both the strengths and weaknesses of the pooled population NGS approach and outline some guidelines and suggestions that might be considered when planning future projects.

opencc-zeroDec 2011View details →

Data from: Genetic divergence is decoupled from ecological diversification in the Hawaiian Nesosydne planthoppers

Adaptive radiation involves ecological shifts coupled with isolation of gene pools. However, we know little about what drives the initial stages of divergence. We study a system in which ecological diversification is found within a chronologically well-defined geological matrix to provide insight into this enigmatic phase of radiation. We tested the hypothesis that a period of geographic isolation precedes ecological specialization in an adaptive radiation of host-specialized Hawaiian planthoppers. We examined population structure and history using mitochondrial and multiple independent microsatellite loci in a species whose geographic distribution on the island of Hawaii enabled us to observe the chronology of divergence in its very earliest stages. We found that genetic divergence is associated with geographic features but not different plant hosts and that divergence times are very recent and on the same timescales as the dynamic geology of the island. Our results suggest an important role for geography in the dynamics of the early stages of divergence.

Data from: Genetics, morphology and ecology reveal a cryptic pika lineage in the Sikkim Himalaya

Asian pika species are morphologically ∼similar and have overlapping ranges. This leads to uncertainty and species misidentification in the field. Phylogenetic analyses of such misidentified samples leads to taxonomic ambiguity. The ecology of many pika species remains understudied, particularly in the Himalaya, where sympatric species could be separated by elevation and/or substrate. We sampled, measured, and acquired genetic data from pikas in the Sikkim Himalaya. Our analyses revealed a cryptic lineage, Ochotona sikimaria, previously reported as a subspecies of O. thibetana. The results support the elevation of this lineage to the species level, as it is genetically divergent from O. thibetana, as well as sister species, O. cansus (endemic to central China) and O. curzoniae (endemic to the Tibetan plateau). The Sikkim lineage diverged from its sister species' about 1.7–0.8 myr ago, coincident with uplift events in the Himalaya. Our results add to the recent spate of cryptic diversity identified from the eastern Himalaya and highlight the need for further study within the Ochotonidae.

opencc-zeroDec 2016View details →

Data from: The genetic architecture of ecological adaptation: intraspecific variation in host plant use by the lepidopteran crop pest Chloridea virescens

Intraspecific variation in ecologically important traits is a cornerstone of Darwin's theory of evolution by natural selection. The evolution and maintenance of this variation depends on genetic architecture, which in turn determines responses to natural selection. Some models suggest that traits with complex architectures are less likely to respond to selection than those with simple architectures, yet rapid divergence has been observed in such traits. The simultaneous evolutionary lability and genetic complexity of host plant use in the Lepidopteran subfamily Heliothinae suggest that architecture may not constrain ecological adaptation in this group. Here we investigate the response of Chloridea virescens, a generalist that feeds on diverse plant species, to selection for performance on a novel host, Physalis angulata (Solanaceae). P. angulata is the preferred host of Chloridea subflexa, a narrow specialist on the genus Physalis. In previous experiments, we found that the performance of C. subflexa on P. angulata depends on many loci of small effect distributed throughout the genome, but whether the same architecture would be involved in the generalist's adoption of P. angulata was unknown. Here we report a rapid response to selection in C. virescens for performance on P. angulata, and establish that the genetic architecture of intraspecific variation is quite similar to that of the interspecific differences in terms of the number, distribution, and effect sizes of the QTL involved. We discuss the impact of genetic architecture on the ability of Heliothine moths to respond to varying ecological selection pressures.

Data from: Comparative multi-locus phylogeography of two Palaearctic spruce bark beetles: influence of contrasting ecological strategies on genetic variation

While phylogeographic patterns of organisms are often interpreted through past environmental disturbances, mediated by climate changes, and geographic barriers, they may also be strongly influenced by species-specific traits. To investigate the impact of such traits, we focused on two Eurasian spruce bark beetles that share a similar geographic distribution, but differ in their ecology and reproduction. Ips typographus is an aggressive tree-killing species characterized by strong dispersal, whereas Dendroctonus micans is a discrete inbreeding species (sib mating is the rule), parasite of living trees and a poor disperser. We compared genetic variation between the two species over both beetles' entire range in Eurasia with five independent gene fragments, to evaluate whether their intrinsic differences could have an influence over their phylogeographic patterns. We highlighted widely divergent patterns of genetic variation for the two species and argue that the difference is indeed largely compatible with their contrasting dispersal strategies and modes of reproduction. In addition, genetic structure in I. typographus divides European populations in a northern and a southern group, as was previously observed for its host plant, and suggests past allopatric divergence. A long divergence time was estimated between East Asian and other populations of both species, indicating their long-standing presence in Eurasia, prior to the last glacial maximum. Finally, the strong population structure observed in D. micans for the mitochondrial locus provides insights into the recent colonization history of this species, from its native European range to regions where it was recently introduced.

opencc-zeroDec 2018View details →

Data from: The spatial ecology of sex ratios in a dioecious plant: relations between ramet and genet sex ratios

1. In clonal dioecious plants, the frequency and spatial distribution of flowering ramets contains information on the underlying genet sex ratio. These measures can also provide insight on potential ecological mechanisms causing variation and bias in sex ratios among populations. 2. We used a novel likelihood-based approach and spatial clustering model to estimate the genet sex ratios from flowering ramet data collected from 32 populations of dioecious Thalictrum pubescens, a clonal species from eastern N. America that occupies moist wetland and forested environments. We investigated sex ratios of seed families, clone size, patterns of flowering and plant height to determine potential causes of sex ratio bias. 3. Flowering ramet sex ratios varied considerably among populations but were significantly male-biased. Seed families grown to flowering also exhibited the same degree of male bias. Both models predicted close correspondence between ramet and genet sex ratios. The likelihood model revealed that gender differences in ramet production could not account for biased sex ratios. The spatial clustering model indicated that ramets were significantly clustered at two spatial scales and estimated similar cluster sizes and densities for both sexes. There was no evidence for spatial segregation of the sexes. Both sexes were equally likely to flower in consecutive years and repeated bouts of flowering had no effect on ramet height. 4. Synthesis. Our analyses suggest that the widespread occurrence of male-biased sex ratios in T. pubescens is unlikely to result from sexual differences in clonal growth or habitat preferences. The bias appears to become established early in the life cycle, perhaps at the seed stage as consequence of local resource competition.

Data from: Genetic differentiation within multiple common grassland plants supports seed transfer zones for ecological restoration

Ecological restoration of grasslands is increasingly based on regional seeds derived from predefined seed transfer zones. However, the degree and spatial pattern of genetic differentiation among provenances of different seed transfer zones is largely unknown. We assessed the genetic differentiation among eight out of 22 German seed transfer zones for seven common grassland species (Arrhenatherum elatius, Centaurea jacea, Daucus carota, Galium album, Hypochaeris radicata, Knautia arvensis and Lychnis flos-cuculi) using AFLP markers. We analysed genetic population structure with AMOVA and Bayesian cluster analysis and tested for isolation by distance and isolation by environment. In all of the investigated species, almost all pairs of provenances were genetically differentiated. Bayesian cluster analysis revealed species-specific numbers and spatial patterns of gene pools, with between two (Arrhenatherum) and eight clusters (Lychnis). Most investigated seed transfer zones represented a unique gene pool in the majority of the species. We found isolation by distance in four species, isolation by environment, driven by climatic seasonality, in three species, and a lack of both in three species. Thus, the observed genetic differentiation appears to be caused by both neutral and adaptive processes. Synthesis and applications. Our study shows that grassland plants are indeed strongly genetically differentiated across Germany supporting the strategy of seed transfer zones for ecological restoration. Although the predefined seed transfer zones are unlikely to match the exact genetic structure of many species, they serve their purpose by capturing a substantial amount of intraspecific genetic variation across species.

opencc-zeroJul 2019View details →

Data from: An ecological history of the relict genetic lineage of Arabidopsis thaliana

The combination of extensive population sampling with whole-genome sequencing in the annual plant Arabidopsis thaliana has recently allowed the identification of a genetically differentiated relict lineage. The most important nuclei of relict A. thaliana is found in the Iberian Peninsula and North Africa, although relict accessions have also been found scattered across Atlantic oceanic islands, eastern Mediterranean Basin, South and East Africa and China. We hypothesised that relict A. thaliana long survived and adapted to a wide array of environments in the Iberian Peninsula and North Africa due to the fact that the region repeatedly acted as glacial refugia. Given the lack of evidence to support this hypothesis, we addressed this issue by studying the ecological history of Iberian and North African relict A. thaliana. To this end, we analysed the relationship between the current habitat suitability of relict A. thaliana, estimated with species distribution models, and the vegetation dynamics in the region over the last millennia using pollen fossil data from sediment cores and reconstructions of past distribution ranges of the most important tree species occurring in the region. Overall, our results indicated that a higher current habitat suitability of relict A. thaliana was correlated with more stable vegetation dynamics since the Last Glacial Maximum and during the Holocene. Given that relict A. thaliana is known to harbour genetic variation specific to its relict nature, we also evaluated the differentiation between relict and non-relict A. thaliana accessions at the functional genetic level for the known flowering genes, CRY2 and TSF. Genomic surveys detected the existence of haplogroups of these genes occurring at very high frequency only among relict accessions. Overall, our study reinforced the relict character of this lineage thought to be at the base of the species' early history. We stress the need to sample in depth other geographic areas harbouring relict A. thaliana and conduct further functional genetic analyses between relict and non-relict accessions to keep disentangling the evolutionary trajectory of this annual plant.

Data from: Ecological resistance surfaces predict fine scale genetic differentiation in a terrestrial woodland salamander

Landscape genetics has seen tremendous advances since its introduction, but parameterization and optimization of resistance surfaces still poses significant challenges. Despite increased availability and resolution of spatial data, few studies have integrated empirical data to directly represent ecological processes as genetic resistance surfaces. In our study, we determine the landscape and ecological factors affecting gene flow in the western slimy salamander (Plethodon albagula). We used field data to derive resistance surfaces representing salamander abundance and rate of water loss through combinations of canopy cover, topographic wetness, topographic position, solar exposure, and distance from ravine. These ecologically-explicit composite surfaces directly represent an ecological process or physiological limitation of our organism. Using generalized linear mixed effects models, we optimized resistance using a non-linear optimization algorithm to minimize model AIC. We found clear support for the resistance surface representing the rate of water loss experienced by adult salamanders in the summer. Resistance was lowest at intermediate levels of water loss and higher when the rate of water loss was predicted to be low or high. This pattern may arise from the compensatory movement behavior of salamanders through suboptimal habitat, but also reflects the physiological limitations of salamanders and their sensitivity to extreme environmental conditions. Our study demonstrates that composite representations of ecologically-explicit processes can provide novel insight and can better explain genetic differentiation than ecologically-implicit landscape resistance surfaces. Additionally, our study underscores the fact that spatial estimates of habitat suitability or abundance may not serve as adequate proxies for describing gene flow, as predicted abundance was a poor predictor of genetic differentiation.

Data from: Genetic evidence for ecological divergence in kokanee salmon

The evolution of locally adapted phenotypes among populations that experience divergent selective pressures is a central mechanism for generating and maintaining biodiversity. Recently, the advent of high-throughput DNA sequencing technology has provided tools for investigating the genetic basis of this process in natural populations of non-model organisms. Kokanee, the freshwater form of sockeye salmon (Oncorhynchus nerka), occurs as two reproductive ecotypes, which differ in spawning habitat (tributaries vs. shorelines), however outside of the spawning season the two ecotypes co-occur in many lakes and lack diagnostic morphological characteristics. We used restriction site associated DNA (RAD) sequencing to identify 6,145 SNPs and genotype kokanee from multiple spawning sites in Okanagan Lake (British Columbia, Canada). Outlier tests revealed 18 loci putatively under divergent selection between ecotypes, all of which exhibited temporally stable allele frequencies within ecotypes. Six outliers were annotated to sequences in the NCBI database, two of which matched genes associated with early development. There was no evidence for neutral genetic differentiation, however, outlier loci demonstrated significant structure with respect to ecotype and had high assignment accuracy in mixed composition simulations. The absence of neutral structure combined with a small number of highly divergent outlier loci is consistent with theoretical predictions for the early stages of ecological divergence. These outlier loci were then applied to a realistic fisheries scenario in which additional RAD sequencing was used to genotype kokanee collected by trawl in Okanagan Lake, providing preliminary evidence that this approach may be an effective tool for conservation and management.

Data from: Ecological and genetic determinants of plasmid distribution in Escherichia coli

Bacterial plasmids are important carriers of virulence and antibiotic resistance genes. Nevertheless, little is known of the determinants of plasmid distribution in bacterial populations. Here the factors affecting the diversity and distribution of the large plasmids of Escherichia coli were explored in cattle grazing on semi-natural grassland, a set of populations with low frequencies of antibiotic resistance genes. Critically, the population genetic structure of bacterial hosts was chararacterized. This revealed structured E. coli populations with high diversity between sites and individuals but low diversity within cattle hosts. Plasmid profiles, however, varied considerably within the same E. coli genotype. Both ecological and genetic factors affected plasmid distribution: plasmid profiles were affected by site, E. coli diversity, E. coli genotype and the presence of other large plasmids. Notably 3/26 E. coli serotypes accounted for half the observed plasmid-free isolates indicating that within species variation can substantially affect carriage of the major conjugative plasmids. The observed population structure suggest that most of the opportunities for within species plasmid transfer occur between different individuals of the same genotype and support recent experimental work indicating that plasmid–host coevolution, and epistatic interactions on fitness costs are likely to be important in determining occupancy.

Data from: Novel concordance between geographic, environmental and genetic structure in the ecological generalist prickly sculpin (Cottus asper) in California

Ecological generalists may contain a wealth of information concerning diversity, ecology, and geographic connectivity throughout their range. We explored these ideas in prickly sculpin (Cottus asper), a small generalist freshwater fish species where coastal forms have potentially undergone radiations into inland lacustrine and riverine environments. Using a 962bp cytochrome b mtDNA marker and 11 microsatellites, we estimated diversity, divergence times, gene flow, and structure among populations at 43 locations throughout California. We then incorporated genetic and GIS data into ecological niche models to assess ecological conditions within identified groups. Though not reciprocally monophyletic, unique mtDNA haplotypes, microsatellite clustering, and measures of isolation by distance (Coastal: r = 0.960, P < 0.001; Inland: r = 0.277, P = 0.148) suggest 2 novel taxonomic groups, Coastal and Inland (constrained to Great Central Valley). Divergence estimates of 41–191 kya combined with the regional biogeographic history suggest geographic barriers are absent between groups since divergence, but ecological niche modeling revealed significant environmental differences (t = 10.84, P < 0.001). Introgressed individuals were also discovered between groups in an ecologically and geographically intermediate region. Population structure was limited, predominately found in tributaries of the San Joaquin basin in the Inland group. Overall, C. asper exhibited substantial genetic diversity, despite its ecological generality, reflecting California's historically unique and complex hydrology. More broadly, this study illustrates variable environments within the range of a generalist species may mask genetic divergences and should not be overlooked in biodiversity assessments.

Data from: Spatial and ecological population genetic structures within two island-endemic Aeonium species of different niche width

The Crassulacean genus Aeonium is a well-known example for plant species radiation on oceanic archipelagos. However, while allopatric speciation among islands is documented for this genus, the role of intra-island speciation due to population divergence by topographical isolation or ecological heterogeneity has not yet been addressed. The aim of this study was to investigate intraspecific genetic structures and to identify spatial and ecological drivers of genetic population differentiation on the island scale. We analyzed inter simple sequence repeat variation within two island-endemic Aeonium species of La Palma: one widespread generalist that covers a large variety of different habitat types (Ae. davidbramwellii) and one narrow ecological specialist (Ae. nobile), in order to assess evolutionary potentials on this island. Gene pool differentiation and genetic diversity patterns were associated with major landscape structures in both species, with phylogeographic implications. However, overall levels of genetic differentiation were low. For the generalist species, outlier loci detection and loci–environment correlation approaches indicated moderate signatures of divergent selection pressures linked to temperature and precipitation variables, while the specialist species missed such patterns. Our data point to incipient differentiation among populations, emphasizing that ecological heterogeneity and topographical structuring within the small scales of an island can foster evolutionary processes. Very likely, such processes have contributed to the radiation of Aeonium on the Canary Islands. There is also support for different evolutionary mechanisms between generalist and specialist species.