Low genetic differentiation among reed warbler Acrocephalus scirpaceus populations across Europe

Migratory birds generally have higher dispersal propensity than resident species and are thus expected to show less genetic differentiation. On the other hand, specific migration patterns may promote genetic structure, such as in situations where migratory divides impede random mixing of individuals. Here we investigated population genetic structure and gene flow patterns in a polytypic passerine, the reed warbler Acrocephalus scirpaceus which shows a migratory divide in central Europe. Using ten polymorphic microsatellite loci and extensive sampling we found low but significant overall genetic differentiation (F_ST=0.013, G’_ST=0.078, D=0.063). Hierarchical F‐statistics and barrier analyses showed low but significant genetic differentiation of Iberian populations, and also slight genetic differences across the migratory divide and between subspecies (A. s. scirpaceus and A. s. fuscus). Three individual‐based Bayesian methods, however, inferred a single genetic unit. Our study thus found low levels of genetic differentiation among reed warbler populations but this genetic differentiation was not pronounced enough to detect a clear population structure using the microsatellite data and no prior information on geographic location of the sampled individuals. This result indicates high levels of gene flow and suggests a possibly recent divergence of European populations after a rapid range expansion. Further studies are necessary to assess divergence times and to reveal the evolutionary history of the reed warbler populations.     

Heteropatric speciation in a duck,Anas crecca

Heteropatric differentiation is a mode of speciation with gene flow in which divergence occurs between lineages that are in sympatry and allopatry at different times during cyclic spatial movements. Empirical evidence suggests that heteropatric differentiation may prove to be common among seasonally migratory organisms. We examined genetic differentiation between the sedentary Aleutian Islands population of green‐winged teal (Anas crecca‐nimia) and its close migratory relative, the Eurasian, or Old World (OW), Anas c. crecca population, a portion of which passes through the range of nimia during its seasonal migrations. We also examined its relationship with the parapatric North American, New World (NW), A. c. carolinensis population. Sequence data from eight nuclear introns and the mtDNA control region showed that the nimia‐crecca divergence occurred much more recently than the deeper crecca‐carolinensis split (~83 000 years vs. ~1.1 Myr). Despite considerable spatial overlap between crecca and nimia during seasonal migration, three key predictions of heteropatric differentiation are supported: significant genetic divergence (overall mean Φ_st  = 0.07), low gene flow (2N_em ~ 1.8), and an effective population size in nimia that is not especially low (N_e ~ 80 000 individuals). Similar levels of gene flow have come into nimia from carolinensis, but no detectable nuclear gene flow has gone out of nimia into either OW (crecca) or NW (carolinensis) populations. We infer that adaptations of these populations to local optima in different places (e.g. each matching their reproductive effort to different resource blooms) promote genetic isolation and divergence despite periods of sympatry between them, as the heteropatric model predicts.     

Genetic differentiation across the social transition in a socially polymorphic sweat bee,Halictus rubicundus

Eusociality is widely considered a major evolutionary transition. The socially polymorphic sweat bee Halictus rubicundus, solitary in cooler regions of its Holarctic range and eusocial in warmer parts, is an excellent model organism to address this transition, and specifically the question of whether sociality is associated with a strong barrier to gene flow between phenotypically divergent populations. Mitochondrial DNA (COI) from specimens collected across the British Isles, where both solitary and social phenotypes are represented, displayed limited variation, but placed all specimens in the same European lineage; haplotype network analysis failed to differentiate solitary and social lineages. Microsatellite genetic variability was high and enabled us to quantify genetic differentiation among populations and social phenotypes across Great Britain and Ireland. Results from conceptually different analyses consistently showed greater genetic differentiation between geographically distant populations, independently of their social phenotype, suggesting that the two social forms are not reproductively isolated. A landscape genetic approach revealed significant isolation by distance (Mantel test r = 0.622, P < 0.001). The Irish Sea acts as physical barrier to gene flow (partial Mantel test r = 0.453, P < 0.01), indicating that geography, rather than expression of solitary or social behaviour (partial Mantel test r = −0.238, P = 0.053), had a significant effect on the genetic structure of H. rubicundus across the British Isles. Although we cannot reject the hypothesis of a genetic underpinning to differences in solitary and eusocial phenotypes, our data clearly demonstrate a lack of reproductive isolation between the two social forms.     

Scale‐dependent genetic structure of the Idaho giant salamander (Dicamptodon aterrimus) in stream networks

The network architecture of streams and rivers constrains evolutionary, demographic and ecological processes of freshwater organisms. This consistent architecture also makes stream networks useful for testing general models of population genetic structure and the scaling of gene flow. We examined genetic structure and gene flow in the facultatively paedomorphic Idaho giant salamander, Dicamptodon aterrimus, in stream networks of Idaho and Montana, USA. We used microsatellite data to test population structure models by (i) examining hierarchical partitioning of genetic variation in stream networks; and (ii) testing for genetic isolation by distance along stream corridors vs. overland pathways. Replicated sampling of streams within catchments within three river basins revealed that hierarchical scale had strong effects on genetic structure and gene flow. amova identified significant structure at all hierarchical scales (among streams, among catchments, among basins), but divergence among catchments had the greatest structural influence. Isolation by distance was detected within catchments, and in‐stream distance was a strong predictor of genetic divergence. Patterns of genetic divergence suggest that differentiation among streams within catchments was driven by limited migration, consistent with a stream hierarchy model of population structure. However, there was no evidence of migration among catchments within basins, or among basins, indicating that gene flow only counters the effects of genetic drift at smaller scales (within rather than among catchments). These results show the strong influence of stream networks on population structure and genetic divergence of a salamander, with contrasting effects at different hierarchical scales.     

A genomic assessment of population structure and gene flow in an aquatic salamander identifies the roles of spatial scale,barriers, and river architecture

相似文献   

Low levels of genetic differentiation characterize Australian humpback whale (Megaptera novaeangliae) populations

Humpback whales undertake long‐distance seasonal migrations between low latitude winter breeding grounds and high latitude summer feeding grounds. We report the first in‐depth population genetic study of the humpback whales that migrate to separate winter breeding grounds along the northwestern and northeastern coasts of Australia, but overlap on summer feeding grounds around Antarctica. Weak but significant differentiation between eastern and western Australia was detected across ten microsatellite loci (F_ST = 0.005, P = 0.001; D_EST = 0.031, P = 0.001, n = 364) and mitochondrial control region sequences (F_ST = 0.017 and Φ_ST = 0.069, P = 0.001, n = 364). Bayesian clustering analyses using microsatellite data could not resolve any population structure unless sampling location was provided as a prior. This study supports the emerging evidence that weak genetic differentiation is characteristic among neighboring Southern Hemisphere humpback whale breeding populations. This may be a consequence of relatively high gene flow facilitated by overlapping summer feeding areas in Antarctic waters.     

Flickers of speciation: Sympatric colour morphs of the arc‐eye hawkfish,Paracirrhites arcatus,reveal key elements of divergence with gene flow

One of the primary challenges of evolutionary research is to identify ecological factors that favour reproductive isolation. Therefore, studying partially isolated taxa has the potential to provide novel insight into the mechanisms of evolutionary divergence. Our study utilizes an adaptive colour polymorphism in the arc‐eye hawkfish (Paracirrhites arcatus) to explore the evolution of reproductive barriers in the absence of geographic isolation. Dark and light morphs are ecologically partitioned into basaltic and coral microhabitats a few metres apart. To test whether ecological barriers have reduced gene flow among dark and light phenotypes, we evaluated genetic variation at 30 microsatellite loci and a nuclear exon (Mc1r) associated with melanistic coloration. We report low, but significant microsatellite differentiation among colour morphs and stronger divergence in the coding region of Mc1r indicating signatures of selection. Critically, we observed greater genetic divergence between colour morphs on the same reefs than that between the same morphs in different geographic locations. We hypothesize that adaptation to the contrasting microhabitats is overriding gene flow and is responsible for the partial reproductive isolation observed between sympatric colour morphs. Combined with complementary studies of hawkfish ecology and behaviour, these genetic results indicate an ecological barrier to gene flow initiated by habitat selection and enhanced by assortative mating. Hence, the arc‐eye hawkfish fulfil theoretical expectations for the earliest phase of speciation with gene flow.     

Positive correlation between vegetation dissimilarity and genetic differentiation of Carex sempervirens

Synthesizing genetic data at population level and vegetation data at community level may give insight into how ecological and evolutionary processes associated with different vegetation influence genetic diversity and differentiation of plant populations. We correlated population genetic patterns of Carex sempervirens with community vegetation patterns in abandoned subalpine grassland in the Swiss Alps. Within-population genetic diversity (percentage of polymorphic bands and Nei's gene diversity) of C. sempervirens was not significantly correlated with plant richness, evenness or Shannon's diversity index (Pearson correlation coefficient |r|<0.32, P>0.10). However, the genetic distance (F_ST) between C. sempervirens populations was significantly positively correlated with the vegetation dissimilarity between communities (Mantel's r=0.23, P<0.01). The correlation between the population genetic differentiation and the vegetation dissimilarity was not due to the parallel effects of geographic isolation or site conditions, because F_ST was not correlated with the geographic distance or the pairwise differences in any of the measured site condition parameters. One likely mechanism is that different plant communities were associated with different selective forces, which, in turn, influenced the genetic differentiation between C. sempervirens populations. Another possibility is that the vegetation heterogeneity (dissimilarity) generated ecological barriers against gene flow and thus enhanced the genetic differentiation between C. sempervirens populations.     

Genetic differentiation that is exceptionally high and unexpectedly sensitive to geographic distance in the absence of gene flow: Insights from the genus Eranthis in East Asian regions

Genetic differentiation between populations is determined by various factors, including gene flow, selection, mutation, and genetic drift. Among these, gene flow is known to counter genetic differentiation. The genus Eranthis, an early flowering perennial herb, can serve as a good model to study genetic differentiation and gene flow due to its easily detectable population characteristics and known reproductive strategies, which can be associated with gene flow patterns. Eranthis populations are typically small and geographically separated from the others. Moreover, previous studies and our own observations suggest that seed and pollen dispersal between Eranthis populations is highly unlikely and therefore, currently, gene flow may not be probable in this genus. Based on these premises, we hypothesized that the genetic differentiation between the Eranthis populations would be significant, and that the genetic differentiation would not sensitively reflect geographic distance in the absence of gene flow. To test these hypotheses, genetic differentiation, genetic distance, isolation by distance, historical gene flow, and bottlenecks were analyzed in four species of this genus. Genetic differentiation was significantly high, and in many cases, extremely high. Moreover, genetic differentiation and geographic distance were positively correlated in most cases. We provide possible explanations for these observations. First, we suggest that the combination of the marker type used in our study (chloroplast microsatellites), genetic drift, and possibly selection might have resulted in the extremely high genetic differentiation observed herein. Additionally, we provide the possibility that genetic distance reflects geographic distance through historical gene flow, or adaptation in the absence of historical gene flow. Nevertheless, our explanations can be more rigorously examined and further refined through additional observations and various population genetic analyses. In particular, we suggest that other accessible populations of the genus Eranthis should be included in future studies to better characterize the intriguing population dynamics of this genus.     

Genetic variation and population structure of swimming crab (Portunus trituberculatus) inferred from mitochondrial control region

Genetic variation and population structure in Portunus trituberculatus along the coast of China were revealed according to 617 bp of mitochondrial DNA control region. 90 polymorphic sites defined 53 distinct haplotypes, showing a moderately high diversity among 72 individuals sampled from eight localities. Neighbor-joining tree, statistics analyses of gene flow and genetic differentiation index indicated two populations from Beihai and Laizhou had differentiated. The population from Yingkou, Dandong, Laizhou and Beihai had smaller genetic diversity compared to that from Ningbo, Lianyungang, Qingdao and Japan according to the genetic distance. And mantel test showed significant positive correlation between genetic distance and geographic distance for P. trituberculatus. TCS parsimony network suggested that all the animals sampled were probably the result of recent divergence from a common ancestral haplotype but for Laizhou population. Moreover, the haplotype distribution appeared to correlate with a recent colonization followed by localized genetic differentiation. Mismatch distribution results suggested that Ningbo, Yingkou, Qingdao, Lianyungang and Japan populations, particularly Dandong population had experienced a sudden demographic or spatial expansion. The Pleistocene glaciations might contribute to this process.     

Genetic differentiation and history of populations of the Italian treefrog Hyla intermedia: lack of concordance between mitochondrial and nuclear markers

The genetic differentiation among 33 populations of the Italian treefrog, Hyla intermedia (Anura: Hylidae), was investigated using both biparentally (23 allozyme loci) and maternally (partial mitochondrial cytochrome b gene) inherited markers. Two main population groups were evidenced by both markers, located north and south of the northern Apennines. However, the pattern of differentiation between these two groups was much less pronounced at allozymes than at mtDNA, leading to gene flow estimates that were 25 times lower at mitochondrial than at nuclear level. Also, the mtDNA divergence between the two groups was particularly marked for two cospecific lineages of anuran amphibians (the P-distance being on average 9.04%), while their average genetic distance at allozymes was comparatively low (D _NEI = 0.07). This contrasting pattern of nuclear versus mitochondrial genetic variation is discussed in the context of: (1) marker specific selection, (2) secondary contact and sex-biased gene flow and (3) ancestral polymorphism and colonization from north to south. Finally we emphasize how, for population genetic studies, the use of multiple markers having distinct evolutionary properties can help unravel the existence of more complex evolutionary histories.     

Dispersal and population structure of the rufous bettong,Aepyprymnus rufescens (Marsupialia: Potoroidae)

Abstract Many species of herbivorous mammals declined to extinction following European settlement of inland Australia. The rufous bettong, Aepyprymnus rufescens (a macropodoid marsupial), is ecologically similar to many of these species. We used analysis of microsatellite markers to determine dispersal patterns and mating system characteristics in a cluster of local populations of A. rufescens, with the aim of gaining a better understanding of regional population dynamics in such species. Particularly, we asked whether the rufous bettong showed source‐sink dynamics, as Morton (1990) hypothesized that many mammals may have been made vulnerable to extinction through such processes. We compared populations separated by distances of up to 12 km, and detected significant genetic differentiation among local populations (F_ST = 0.016). Females displayed greater genetic structuring than males, suggesting that females dispersed over shorter distances or less frequently than males. Geographic distance was weakly related to genetic distance between populations suggesting some gene flow at this scale, and paternity assignment indicated that dispersal can occur over distances of up to 6.5 km. Our study populations varied widely in density, but density did not explain the pattern of genetic differentiation observed. These findings of significant structure among populations, some influence of distance on genetic divergence and that density explains little of the divergence among populations, suggested that source‐sink dynamics did not play a large role among these populations. Variance in male mating success was low (maximum assigned paternity for an individual male was 14% of offspring). While data on multiple maternity were limited, roughly half of repeat maternity was assigned to the same male, suggesting that the mating system of the rufous bettong is not purely promiscuous.     

GENETIC DIVERGENCE IN PERIPHERALLY ISOLATED POPULATIONS OF CHAFFINCHES IN THE ATLANTIC ISLANDS

Peripherally isolated populations of common chaffinches (Fringilla coelebs) in the Canaries, Madeira, and Azores were compared genetically with their putative ancestral stock in Iberia and Morocco, and with a population of blue chaffinches (F. teydea) from Tenerife, using protein electrophoresis of 42 loci. The continental populations are only weakly differentiated genetically (F_ST = 0.092), despite distinctive subspecific differences in plumage and morphometrics between Iberia and Morocco populations. Estimated levels of gene flow among continental populations are high enough to account for their relative genetic homogeneity, and it is unlikely that homogenizing selection is operating to mimic the effects of gene flow. In contrast, the Atlantic island populations are well differentiated genetically (F_ST = 0.321), and have diverged considerably from their continental conspecifics. The development of significant genetic differentiation within the Canaries but not the Azores likely results from smaller population sizes, very restricted gene flow, and enhanced random drift in the former populations. There is no convincing evidence in support of stronger directional selection acting on genotypes or phenotypes to reduce within-population variability in Canaries populations as proposed by Grant (1979), although other tenets of his model of island evolution are supported by our analysis. Although genetic variability is reduced in four of the Canaries populations, only the Hierro population appears to have encountered a severe bottleneck. Yet it has not differentiated markedly from the La Palma population to which it is subspecifically allied. We conclude that gradual divergence in isolated populations of small to moderate size is the most plausible explanation for the evolution of intraspecific and interspecific diversity in Atlantic island chaffinches.     

Evolution of putative barrier loci at an intermediate stage of speciation with gene flow in campions (Silene)

Understanding the origin of new species is a central goal in evolutionary biology. Diverging lineages often evolve highly heterogeneous patterns of genetic differentiation; however, the underlying mechanisms are not well understood. We investigated evolutionary processes governing genetic differentiation between the hybridizing campions Silene dioica (L.) Clairv. and S. latifolia Poiret. Demographic modelling indicated that the two species diverged with gene flow. The best‐supported scenario with heterogeneity in both migration rate and effective population size suggested that a small proportion of the loci evolved without gene flow. Differentiation (F _ST) and sequence divergence (d _XY) were correlated and both tended to peak in the middle of most linkage groups, consistent with reduced gene flow at highly differentiated loci. Highly differentiated loci further exhibited signatures of selection. In between‐species population pairs, isolation by distance was stronger for genomic regions with low between‐species differentiation than for highly differentiated regions that may contain barrier loci. Moreover, differentiation landscapes within and between species were only weakly correlated, suggesting that linked selection due to shared recombination and gene density landscapes is not the dominant determinant of genetic differentiation in these lineages. Instead, our results suggest that divergent selection shaped the genomic landscape of differentiation between the two Silene species, consistent with predictions for speciation in the face of gene flow.     

Stark sexual display divergence among jumping spider populations in the face of gene flow

Gene flow can inhibit evolutionary divergence by eroding genetic differences between populations. A current aim in speciation research is to identify conditions in which selection overcomes this process. We focused on a state of limited differentiation, asking whether selection enables divergence with gene flow in a set of Habronattus americanus jumping spider populations that exhibit three distinct male sexual display morphs. We found that each population is at high frequency or fixed for a single morph. These strong phenotypic differences contrast with low divergence at 210 AFLP markers, suggesting selection has driven or maintains morph divergence. Coinciding patterns of isolation by distance and ‘isolation by phenotype’ (i.e. increased genetic divergence among phenotypically contrasting populations) across the study area support several alternative demographic hypotheses for display divergence, each of which entails gene flow. Display‐associated structure appears broadly distributed across the genome and the markers producing this pattern do not stand out from background levels of differentiation. Overall, the results suggest selection can promote stark sexual display divergence in the face of gene flow among closely related populations.     

地理因素对箭竹复合体遗传多样性与遗传分化的影响

地理因素对植物天然居群的物种分布和种内分化具有重要影响。该研究通过对箭竹复合体内39个居群的14对SSR数据进行深入分析,旨在揭示重要地理因素(如海拔、纬度、地理距离)对该复合体内遗传多样性和遗传分化式样的影响。结果表明:(1)糙花箭竹亚支系遗传多样性最高(H_e=0.50),而团竹亚支系的遗传多样性最低(H_e=0.33)。(2)遗传多样性与纬度、海拔在A、B两个支系水平呈显著正相关关系,但在亚支系水平,遗传多样性的变化趋势呈现出更为复杂的局面,部分支系表现为负相关关系,推测纬度和海拔对箭竹复合体内遗传多样性水平具有一定影响,但也需重视其他进化因素的作用。(3)Mantel检验显示,仅在团竹亚支系中检测出较弱的正相关关系,表明地理距离不是影响箭竹复合体内遗传分化的主导因素,后续需结合基因流检测推断杂交事件对其遗传分化的影响。     

LIFE-HISTORY VARIATION AND COMPARATIVE PHYLOGEOGRAPHY OF DARTERS (PISCES: PERCIDAE) FROM THE NORTH AMERICAN CENTRAL HIGHLANDS

Phylogeography seeks to evaluate the relationship between genetic variation and geographic distribution of a species to examine the influence of historical events on divergence. Congruent phylogeographic patterns in codistributed species indicate historical association of the taxa being compared, and the uniform action of biogeographic events in shaping genetic variation. We sought to evaluate the congruence of patterns of genetic variation of five closely related fish species across a well-defined biogeographic boundary. We gathered allozymic and mitochondrial DNA (mtDNA) sequence data for five species of darters (Percidae: Etheostomatini) from populations distributed among biogeographic regions in the Ozark and Ouachita highlands of the south-central United States. Comparisons among species revealed noncongruence in the magnitude of genetic divergence in both allozymes and mtDNA sequences. We hypothesized that noncongruence resulted, in part, from differences in life histories of the species in our comparison. To address this hypothesis, we evaluated the association between gene flow (measured by N_em) and variation in body size and fecundity variables because they have been shown to influence gene flow in fishes. Correlation analysis revealed an association between gene flow and fecundity (r = 0.88), but not with body size (r = 0.36) or reproductive investment per individual (r = –0.23). The result was similar when independent contrasts of the original variables were used in correlation analyses. Phylogeographic analysis of mtDNA sequence data indicated the importance of history, evident in gene trees of Percina nasuta and Percina phoxocephala. Divergence rates between these two taxa may differ because of historically persistent differences in population sizes, reflected in present-day abundance and fecundity differences. Conversely, Percina caprodes showed little evidence of divergence in mtDNA sequences and yielded the highest mean N_em values from allozyme data. Comparisons among closely related, codistributed taxa may help discriminate among the possibilities for noncongruence in biogeographic studies by allowing evaluation of the influence of life history on patterns of gene flow.     

Genetic population structure of spotted seatrout Cynoscion nebulosus along the south‐eastern U.S.A.

Analyses of the genetic population structure of spotted seatrout Cynoscion nebulosus along the south‐eastern U.S. coast using 13 microsatellites suggest significant population differentiation between fish in North Carolina (NC) compared with South Carolina (SC) and Georgia (GA), with New River, NC, serving as an area of integration between northern and southern C. nebulosus. Although there is a significant break in gene flow between these areas, the overall pattern throughout the sampling range represents a gradient in genetic diversification with the degree of geographic separation. Latitudinal distance and estuarine density appear to be main drivers in the genetic differentiation of C. nebulosus along the south‐eastern U.S. coast. The isolation‐by‐distance gene‐flow pattern creates fine‐scale differences in the genetic composition of proximal estuaries and dictates that stocking must be confined to within 100 km of the location of broodstock collection in order to maintain the natural gradient of genetic variation along the south‐eastern U.S. coast.     

Small-scale population divergence is driven by local larval environment in a temperate amphibian

Genomic variation within and among populations is shaped by the interplay between natural selection and the effects of genetic drift and gene flow. Adaptive divergence can be found in small-scale natural systems even when population sizes are small, and the potential for gene flow is high, suggesting that local environments exert selection pressures strong enough to counteract the opposing effects of drift and gene flow. Here, we investigated genomic differentiation in nine moor frog (Rana arvalis) populations in a small-scale network of local wetlands using 16,707 ddRAD-seq SNPs, relating levels of differentiation with local environments, as well as with properties of the surrounding landscape. We characterized population structure and differentiation, and partitioned the effects of geographic distance, local larval environment, and landscape features on total genomic variation. We also conducted gene–environment association studies using univariate and multivariate approaches. We found small-scale population structure corresponding to 6–8 clusters. Local larval environment was the most influential component explaining 2.3% of the total genetic variation followed by landscape features (1.8%) and geographic distance (0.8%), indicative of isolation-by-environment, -by-landscape, and -by-distance, respectively. We identified 1000 potential candidate SNPs putatively under divergent selection mediated by the local larval environment. The candidate SNPs were involved in, among other biological functions, immune system function and development. Our results suggest that small-scale environmental differences can exert selection pressures strong enough to counteract homogenizing effects of gene flow and drift in this small-scale system, leading to observable population differentiation.Subject terms: Genetic variation, Ecological genetics     

Genetic drift drives evolution in the bird‐pollinated,terrestrial island endemic Grevillea georgeana (Proteaceae)

Plant species distributed across terrestrial islands can show significant genetic divergence among populations if seed and pollen dispersal are restricted. We assessed the genetic connectivity between populations of Grevillea georgeana, restricted to seven disjunct inselbergs in semi‐arid Western Australia. The phylogeographical pattern and population genetics of populations were determined using sequence data from two plastid DNA intergenic spacers and ten nuclear microsatellite loci. The plastid DNA markers indicated high genetic differentiation among the majority of populations. Haplotypes were restricted to individual inselbergs, with the exception of two that were shared among three isolated populations that formed part of an elongated greenstone belt and that may be connected via inaccessible populations of G. georgeana. There was also strong differentiation within some of the populations, suggesting long‐term isolation and persistence of G. georgeana on these terrestrial islands. Overall, the genetic patterns suggest limited seed dispersal, with differentiation in the plastid DNA genome being driven by genetic drift. In contrast, pollen movement, although generally restricted, may occur between neighbouring populations, resulting in a pattern of isolation by distance in the nuclear markers. This potential for limited or no seed dispersal, but connectivity via pollen flow, should be considered, given that many of the inselbergs are under consideration for resource development. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178 , 155–168.