Patterns of hybridization in a multispecies hybrid zone in the Ranunculus cantoniensis complex (Ranunculaceae)

Simultaneous hybridizations among three or more parental taxa occur in nature, but these have rarely been analysed. The present study investigates the natural hybridization of diploid members of the Ranunculus cantoniensis complex over a microgeographical area in south‐western China. Sequence information from maternally inherited plastid DNA (trnQ‐rps16 and rpL32‐trnL) and biparentally inherited nuclear ribosomal DNA was used to identify hybrids, and these were further confirmed by a dramatic reduction in pollen viability. The populations from the contact zone contained individuals that had more than two nuclear ribosomal internal transcribed spacer (nrITS) types; in addition, a network analysis revealed the presence of hard conflicts between the nuclear and plastid DNA data. These results prove that R. trigonus and R. silerifolius var. dolicanthus have relatively little reproductive isolation from each other, leading to a high gene flow rate in contact populations. The four investigated species can hybridize with each other in this contact zone, forming seven hybrid types. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174 , 227–239.     

A molecular study of hybridization and homoploid hybrid speciation in Argyranthemum (Asteraceae) on Tenerife,the Canary Islands

Examples of recurrent homoploid hybrid speciation are few. One often‐cited example is Argyranthemum sundingii. This example includes two described species, A. lemsii and A. sundingii, resulting from reciprocal hybridization between A. broussonetii and A. frutescens on Tenerife. The four species and artificial F₁ and F₂ hybrids have previously been investigated morphologically and cytologically. Here, we examine population differentiation based on amplified fragment length polymorphism to get a better understanding of the genetic relationships among the species and the extent of hybridization. We aim to investigate if there is molecular support for treating the hybrid species as one taxon. Seven parental and four hybrid species populations (149 individuals) were analysed and we scored 85 polymorphic markers. A few (2–5) were private to each species but variably present and mostly rare. Our principal coordinate, STRUCTURE and BAPS analyses and AMOVA resulted in a clear separation of the parental species. The hybrid species were genetically less divergent but not identical. Our data indicate that hybridization and introgression are common in all these species on Tenerife and support the hypothesis that homoploid hybrid speciation has occurred repeatedly. Intrinsic post‐zygotic barriers are notoriously weak in Argyranthemum and reproductive isolation and speciation result primarily from strong ecological selection. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 19–31.     

The role of parental and hybrid species in multiple introgression events: evidence of homoploid hybrid speciation in Centaurea (Cardueae,Asteraceae)

Molecular approaches have greatly increased the number of confirmed homoploid hybrids, which suggests that the frequency of this phenomenon was underestimated in the past because it was much more difficult to detect than allopolyploidy. Centaurea is a suitable model group for studying homoploid speciation, as hybridization events have been commonly reported for this genus. Based on this, here we study Centaurea × forsythiana, a naturally occurring homoploid hybrid between two Sardinian endemics, C. horrida and C. filiformis, using a molecular approach involving nuclear and plastid markers, to understand the underlying population dynamics between homoploid hybrids and their parents. Our results confirm that C. × forsythiana is a hybrid between the above‐mentioned species and define the roles of the parents. Plastid markers point towards C. horrida as the maternal progenitor, and nuclear markers reveal that the other parental species, C. filiformis, is itself an old, stabilized homoploid hybrid related to the C. paniculata complex from the Italian mainland. Homoploid hybrid speciation is discussed and C. × forsythiana and C. filiformis are compared with other similar examples. The study confirms the importance of introgression between parental species mediated by hybrids and its potential implications in conservation. Furthermore, it shows how hybridization studies become even more complex when the parents are themselves of probable hybrid origin. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 453–467.     

Developmental instability, hybridization and heterozygosity in stick insects of the genus Bacillus (Insecta; Phasmatodea) with different modes of reproduction

Several genetic factors are assumed to influence developmental instability (DI). One is the level of heterozygosity, with higher levels often being associated with decreased DI; another is genetic incompatibility in hybrids, which in several cases has been shown to increase DI. The genus Bacillus includes species which have both amphigonic heterozygous reproducing populations and homozygous parthenogenetic reproducing populations (B. rossius rossius and B. r. redtenbacheri). Furthermore, Bacillus includes hybrid parthenogenetic species, which have very high levels of almost fixed heterozygosities (B. atticus, B. whitei, B. lynceorum). We investigated the phenotypic variance (σ²p) and the impact of hybridization and level of heterozygosity on DI in females from these populations and species of Bacillus. DI was estimated as fluctuating asymmetry (FA) for three bilateral traits: the labial palpus, the maxillary palpus and the antenna. For the labial palpus and maxillary palpus we found, in general, a lower level of DI in the amphigonic females compared with parthenogenetic counterparts from the same species and with parthenogenetic females from the three hybrid species. A higher DI of the antenna was found in the hybrid species when compared with both parthenogenetic and amphigonic populations of the nonhybrid species, suggesting that the genes controlling antenna development are located on the sex chromosomes. The development of the investigated bilateral characters in the hybrid species seemed to be affected more by factors relating to genetic incompatibilities as a consequence of hybridization than by the stabilizing force of increased heterozygosity. Only few differences in σ²p were observed, supporting the possibility that the observed differences in DI are related mainly to internal genetic factors. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 87 , 249–259.     

Strong genetic structuring without assortative mating or reduced hybrid survival in an onychophoran in the Tallaganda State Forest region,Australia

Genetic studies have revealed a large degree of previously unappreciated diversity in morphologically conserved taxa. To understand the implications of this phenomenon, studies investigating the processes responsible for generating and maintaining functional and neutral diversity within such taxa are needed. With this aim, patterns of differentiation across a contact zone between two catchment‐specific, and genetically and subtly morphologically distinguishable, races of the onychophoran Euperipatoides rowelli Reid, 1996 at the Tallaganda State Forest study system, Australia, were quantified using diagnostic body‐pattern differences, microsatellite markers, and the cytochrome c oxidase subunit I (COI) mitochondrial gene. These data were used to test whether hybridization occurred, and whether the reduced survival of hybrids compared with non‐hybrids and/or assortative mating were potentially important factors in retaining the divergence between these races, which probably arose during isolation in Pleistocene glacial refuges. It was found that hybrids at the focal contact zone do not have reduced embryo‐to‐adult survival compared with non‐hybrids, and that races apparently freely interbreed without substantial assortative mating, consistent with little or no cost to hybridization. Nonetheless, at their respective transect ends the races remain distinct. This phenomenon was attributed to the elevated location of the contact zone, which is likely to make it poor habitat for E. rowelli, and thus may restrict dispersal and gene flow. There was also tentative evidence for a relaxed selection against hybridization in the hybrid zone, and the relative importance of these two explanations will require separate investigation. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 589–602.     

Phylogeography of the genus Dasiphora (Rosaceae) in the Qinghai‐Tibetan Plateau: divergence blurred by expansion

Plateau uprisings and climatic oscillations are considered to have caused extensive allopatric divergences that account for the rich species diversity of the Qinghai‐Tibetan Plateau (QTP). However, secondary contact during range shifts in the Quaternary glacial cycles or inter‐uplift stages may have restored the gene flow between species and so counteracted these divergences, particularly in rapidly‐adapting dominant elements. We tested this hypothesis by determining the phylogeographical history of Dasiphora (Rosaceae), a genus of two species that are widely distributed on the QTP and co‐exist in numerous localities. We sequenced two chloroplast DNA fragments (rbcL, trnT‐L) for 559 individuals from 87 populations. Bayesian methods were used to identify phylogenetic relationships and to estimate divergence times. Demographic histories were inferred using neutrality tests, mismatch distribution analysis, and coalescent simulation. A total of 112 haplotypes that clustered into three major groups were identified. The formation of these groups and their subgroups was dated to between the Pliocene and the late Pleistocene. In addition, we found that some groups underwent multiple extensive expansions. Species‐specific haplotypes were identified for each species, although these haplotypes phylogenetically intermixed. These results suggest that recent plateau uplifts and climatic oscillations might have caused the deep divergences observed within this genus. However, later range expansions probably blurred these divergences and possible species boundaries. Our results shed new light on the complex evolutionary history of the QTP alpine plants. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 777–788.     

New microsatellite loci confirm hybrid origin,parthenogenetic inheritance,and mitotic gene conversion in the gynogenetic Amazon molly (Poecilia formosa)

We describe the first microsatellite loci for the gynogenetic Amazon molly, Poecilia formosa, an all‐female species arisen through hybridization of the bisexual species Poecilia mexicana and Poecilia latipinna. The loci showed one to six alleles and an expected heterozygosity between zero and 0.75. As expected with parthenogenetic inheritance, most loci were either constantly homozygous (five loci) or constantly heterozygous (eight loci). For six loci, both heterozygotes and homozygotes occurred. This and the fact that some loci only showed alleles of one of the ancestral species could indicate genome homogenization through mitotic gene conversion. Our new loci conformed to the hybrid origin of Amazon molly and are also applicable to both ancestral bisexual species.     

Lack of association between winter coat colour and genetic population structure in the Japanese hare,Lepus brachyurus (Lagomorpha: Leporidae)

Seasonal changes in fur colour in some mammalian species have long attracted the attention of biologists, especially in species showing population variation in these seasonal changes. Genetic differences among populations that show differences in seasonal changes in coat colour have been poorly studied. Because the Japanese hare (Lepus brachyurus) has two allopatric morphotypes that show remarkably different coat colours in winter, we examined the population genetic structure of the species using partial sequences of the SRY gene and six autosomal genes: three coat colour‐related genes (ASIP, TYR, and MC1R) and three putatively neutral genes (TSHB, APOB, and SPTBN1). The phylogenetic tree of SRY sequences exhibited two distinct lineages that diverged approsimately 1 Mya. Although the two lineages exhibited a clear allopatric distribution, it was not consistent with the distribution of morphotypes. In addition, six nuclear gene sequences failed to reveal genetic differences between morphotypes. Population network trees for 11 expedient populations divided the populations into four groups. Genetic structure analysis revealed an admixture of four genetic clusters in L. brachyurus, two of which showed large genetic differences. Our results suggest ancient vicariance in L. brachyurus, and we detected no genetic differences between the two morphotypes. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 761–776.     

The modality of nine Triturus newt hybrid zones assessed with nuclear,mitochondrial and morphological data

The shape of hybrid zones provides insight into genetic isolation between the evolutionary lineages involved: the greater the limitation to gene flow, the farther along the unimodal to bimodal continuum. We study hybrid zone modality in a group of closely related species at a variety of levels of genetic divergence. We explore the degree and the geography of hybridization in 12 transects of Triturus newts, for nine of the ten secondary contact zones in Europe, using nuclear and mitochondrial encoded genetic data and morphological characteristics. Species status is verified by examining the correlation between the three marker systems in a geographical context. At 40 allozyme loci, two transects classify as unimodal, three as bimodal and two as intermediate, while the signal for hybridization is weak or absent in five transects. One zone studied in duplicate was classified as intermediate in one region and as bimodal in another region. mtDNA introgression is frequent and extends beyond nuclear introgression in two transects. Morphology provides additional evidence for hybridity, including one transect for which the signal of nuclear gene flow is weak. Compared to simulations allowing panmixia, the observed allozyme transitions at contact zones show a deficit of backcrossing to various degrees. Over all transects, there is a weak negative relationship between the level of hybridization and allozyme genetic distance for species pairs, consistent with Bateson–Dobzhansky–Muller effects. This observation, based upon highly comparable data for a single genus, supports conclusions derived from analyses over a wide variety of other taxa. © 2014 The Authors. Biological Journal of the Linnean Society published by John Wiley & Sons Ltd on behalf of The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 604–622.     

Plastid DNA sequence data help to clarify phylogenetic relationships and reticulate evolution in Lycoris (Amaryllidaceae)

The temperate East Asian genus Lycoris is a well known lineage of ornamental geophytes consisting of at least 20 species, some of which are thought to be of natural hybrid origin. Previous genetic studies have supported this hypothesis, but these have relied solely on the use of karyology and/or nuclear ribosomal ITS sequences. No plastid DNA data have been available to address interspecific relationships within Lycoris until now. In this study, 500 individuals from 29 populations representing 16 of the 20 published Lycoris spp. were sampled, and DNA sequences were generated for two plastid markers (trnS‐trnfM and trnC‐ycf6). From these data we inferred phylogenetic relationships among the sampled taxa at the species and population levels using concatenated phylogenetic methods. A well resolved and strongly supported phylogenetic reconstruction for Lycoris was obtained. Although the plastid DNA topology differs from that derived previously using ITS, both genomes produce trees that cluster Lycoris spp. into three clades. One of these, containing polyploid taxa such as L. albiflora, L. caldwellii, L. straminea and L. houdyshelii, shows strong evidence of reticulation, and we discuss the identity of potential parents of these allopolyploids. In contrast, we offer evidence that challenges the hypothesis that triploid individuals of L. radiata are the result of hybridization. Instead, they appear to be autotriploids that have arisen in more than one location. By comparing the phylogenetic results obtained using nuclear genomic data to those from the plastid genome, a much clearer picture of the role that hybridization and reticulation have played in the evolution of Lycoris is emerging. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 115–126.     

Populations composed entirely of hybrid colonies: bidirectional hybridization and polyandry in harvester ants

In eusocial Hymenoptera, haplodiploid life cycles, obligate sterile castes, and polyandry may facilitate selection for hybridization. We analyzed a broad hybrid zone between the ecologically distinct seed‐harvester ants Pogonomyrmex occidentalis (Cresson) and Pogonomyrmex maricopa (Wheeler) using mitochondrial (mt)DNA sequence data, eight morphological markers, and 14 random amplified polymorphic DNA (RAPD) markers. Average mtDNA sequence divergence among parental species was 11.34%, indicating secondary contact. RAPD markers were significantly correlated with morphological variation, confirming the interspecific hybrid origin of all morphologically putative hybrid colonies. A morphological hybrid index indicates an abundance of both F₁ hybrids and parental morphotypes within colonies. Individual character frequencies plotted against distance show coincident and concordant clines, suggesting little to no introgression. The structure of the hybrid zone is two‐fold. Within the western region, stark reversals in character frequencies coincide with overt soil differences, indicating a mosaic hybrid zone structure. The eastern region is a riparian habitat where four adjacent populations were composed entirely of hybrid colonies. These habitat associations suggest that hybrid worker genomes permit dispersal into intermediate environments that select against one or both parental species. The present study suggests that, in addition to retaining reproductive compatibility, ecologically distinct species of ants may generate hybrid colonies maintained by environmental selection. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 320–336.     

Morphological and mitochondrial DNA analyses indicate the presence of a hybrid zone between two species of leaf beetle (Coleoptera; Chrysomelidae) in Southern Spain

The present study reports a case where the survey of morphological and mitochondrial DNA variation among populations of a species complex of leaf beetle, the Gonioctena variabilis complex, has lead to the identification of a hybrid zone between two species of the complex in Southern Spain. The complex is divided into four species distributed around the western Mediterranean region. The four species, G. variabilis, Gonioctena aegrota, Gonioctena gobanzi, and Gonioctena pseudogobanzi, are traditionally determined by differences in the morphology of the male genitalia (aedeagus). To gain insight into the history of the speciation process within this species complex, we sampled populations in Portugal, Spain, Southern France, and Northern Italy. We sequenced a portion of the mitochondrial control region of each individual collected. A haplotype network of these sequences was found to comprise four distinct groups of sequence types, separated by a relatively large number of mutations. Moreover, in most of the samples for which morphological and molecular variation is available, there is a one‐to‐one correspondence between haplotype group, defined by mitochondrial sequence variation, and morphological groups defined on the basis of the aedeagus, showing evidence of four historically independent evolutionary units. This supports the use of the aedeagus morphology as a taxonomically informative trait in this species complex and a recent taxonomic revision upgrading four formerly subspecies, corresponding to the evolutionary units identified in the present study, to species status. However, some of the individuals from our samples in Southern Spain, morphologically identified as G. aegrota, were found to possess mitochondrial sequences typical of G. pseudogobanzi. The opposite case was also found. This suggests the presence of a zone of contact and hybridization between G. aegrota and G. pseudogobanzi. The location of this hybrid zone appears to be unusual. We identify historical scenarios that may explain our observations. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94 , 105–114.     

Physiological implications of genomic state in parthenogenetic lizards of reciprocal hybrid origin

Parthenogenesis often evolves in association with hybridization, but the associated ecological consequences are poorly understood. The Australian gecko Heteronotia binoei is unusual because triploid parthenogenesis evolved through reciprocal crosses between two sexual lineages, resulting in four possible cytonuclear genotypes. In this species complex, we compared the performance of these parthenogenetic genotypes with their sexual progenitors for a suite of physiological traits (metabolic rate, thermal tolerance, locomotor performance, and in vitro activity and gene sequence divergence of a cytonuclear metabolic pathway, cytochrome C oxidase). Mass‐specific metabolic rate scaled differently with body mass for parthenogens and sexuals, while heat tolerance provided the only evidence for cytonuclear incompatibility in hybrid parthenogens. The most prominent phenotypic effects were attributable to nuclear genome dosage. Overall, our results suggest that the hybrid/polyploidy origin of parthenogenetic H. binoei has had surprisingly few negative fitness consequences and may have produced a broader overall niche for the species.     

Functional rare males in diploid parthenogenetic Artemia

Functional males that are produced occasionally in some asexual taxa – called ‘rare males’ – raise considerable evolutionary interest, as they might be involved in the origin of new parthenogenetic lineages. Diploid parthenogenetic Artemia produce rare males, which may retain the ability to mate with females of related sexual lineages. Here, we (i) describe the frequency of male progeny in populations of diploid parthenogenetic Artemia, (ii) characterize rare males morphologically, (iii) assess their reproductive role, using cross‐mating experiments with sexual females of related species from Central Asia and characterize the F1 hybrid offspring viability and (iv) confirm genetically both the identity and functionality of rare males using DNA barcoding and microsatellite loci. Our result suggests that these males may have an evolutionary role through genetic exchange with related sexual species and that diploid parthenogenetic Artemia is a good model system to investigate the evolutionary transitions between sexual species and parthenogenetic strains.     

Evidence for a multi‐peak adaptive landscape in the evolution of trophic morphology in terapontid fishes

Using the Australian marine‐freshwater terapontid fishes as a model system, we examined the role of dietary phenotypic optima in an adaptive macro‐evolutionary landscape. Comparative modelling relying on both a priori and data‐driven identification of selective regimes suggested multi‐peak models as best describing much of the dietary phenotypic landscape of terapontids. Both approaches identified common phenotypic optima for different lineages of marine and freshwater herbivores, and minimal differentiation between carnivores and omnivores, irrespective of their phylogenetic relationships, as the model best describing morphological evolution. Significant correlations also existed between these phenotypic axes and proportions of non‐animal dietary items in species’ diets. While simulation results provided evidence for a multi‐peak adaptive landscape in the evolution of trophic morphology in terapontids, they could not rule out chance convergence in these adaptive peaks. However, they do provide scope for identifying areas for more detailed, functionally specific study of phenotypic convergence in herbivorous terapontid trophic habits. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 623–634.     

Unexpected hybridization patterns in Near Eastern terrapins (Mauremys caspica,M. rivulata) indicate ancient gene flow across the Fertile Crescent

Recent studies indicate that hybridization in animals occurs more frequently than previously thought and that it may play an important evolutionary role. Chelonians are capable of extensive hybridization, raising the question how chelonian species evolve and maintain genetic integrity despite hybridization. Here, we use two sister species with parapatric distribution, Mauremys caspica and M. rivulata, as our model. These taxa are estimated to have diverged some 5.3–7.0 million years ago. Using rangewide sampling and 13 unlinked polymorphic microsatellite markers, five nuclear loci and one mitochondrial gene, we show that hybridization is rare along the contact zone of the two species in Turkey. However, we discovered an unexpected hybrid swarm in the southern Levant that has been hitherto identified with M. rivulata. This hybrid swarm is separated from the inland species M. caspica by a 700‐km‐wide distribution gap corresponding to the Syrian Desert. Ecological palaeomodelling suggests that during more humid climatic episodes in the Last Glacial Maximum and mid‐Holocene, the current contact zone extended into the southern Levant, facilitating the establishment of the now isolated hybrid swarm. Our results support that there is not necessarily a general hybridization pattern in a given species couple and that the extent of gene flow may differ considerably in different parts of the distribution range. Moreover, our results highlight that studies on hybridization should not focus only on extant contact and hybrid zones, but should use rangewide sampling to detect signals of ancient hybridization that might otherwise be missed.     

Unravelling the stylar polymorphism in Melochia (Malvaceae): reciprocity and ancillary characters

Heterostyly is a genetic polymorphism in which plant populations possess two (distyly) or three (tristyly) morphs with flowers differing reciprocally in stigma and anther height. Sex organ deployment has been described as being highly variable among and within species of several distylous taxa belonging to different taxonomic groups. However, the number of studies considering within‐species disparities is still limited. For a better overview of the existing amount of variation that can occur within and between heterostylous species, we sampled 46 populations of six Melochia spp., a style‐polymorphic genus in Cuba. We characterized the floral morphology in all populations and described a set of ancillary characters per species. All of these Melochia spp. are distylous, except for the monomorphic M. nodiflora. The S‐morph produces fewer, larger pollen than L‐morphs, and has verrucose ornamentation. The L‐morph produces reticulate pollen and has larger stigmatic papillae than the S‐morph. The monomorphic M. nodiflora shows ancillary characteristics that are similar to the L‐morph individuals in the related species. As expected, there are differences in ancillary characters among species and also dissimilarities in reciprocity among and within species of Melochia. Our results highlight the importance of considering intraspecific variation in the morphometric characterization of heterostylous taxa. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 147–158.     

Patterns of cryptic hybridization revealed using an integrative approach: a case study on genets (Carnivora, Viverridae, Genetta spp.) from the southern African subregion

Recent years have seen the development of molecular‐based methodologies to investigate hybridization and its impact on the evolutionary process. However, morphological characterization of hybrid zones has only scantily been considered, especially in zootaxa. Thus, the level of congruence between molecular and morphological characters when attempting to detect hybrids remains a poorly tackled area. The genets (genus Genetta) provide an ideal case study for further investigation of the respective contribution of morphology and DNA in hybrid zone characterization because (1) their morphology has recently been exhaustively explored and (2) the existence of hybrid zones in southern Africa was proposed in the literature. We assessed levels of hybridization among the southern African genets, and questioned the role of ecological factors on the hybridization patterns detected. We used an integrative approach involving nine discrete morphological characters and a diagnostic discriminant function, geometric morphometrics and sequences of cytochrome b including collection specimens. The combination of independent materials allowed us to accurately reassess the level of hybridization in southern African genets, and revealed cryptic, interspecific gene flows. Morphology unambiguously detected a low number of G. maculata × G. tigrina hybrids and rejected the hypothesis of a large intergradation zone in KwaZulu‐Natal, thus supporting the species status of the two genets. Cytochrome b analyses revealed: (1) cryptic, massive hybridization between G. tigrina and the sympatric G. felina, and (2) a trace of reticulation (one sequence) between G. tigrina and the allopatric G. genetta. The type specimen of G. mossambica Matschie, 1902 is considered to be a morphological hybrid between G. maculata and G. angolensis. Remarkably, the morphological approaches (discrete characters and morphometrics) proved complementary to conclusions derived from cytochrome b sequences. Whilst morphometrics was generally unable to accurately identify all putative hybrids, this approach revealed diagnostic cranial shape differences between recognized species as well as the cryptic G. ‘letabae’ (included in the super‐species G. maculata). Morphometrics also confirmed the diagnostic value and age dependency of discrete characters. Our integrative approach appeared necessary to the detection of cryptic hybridizations and to the comprehensive characterization of hybrid zones. The recurrent detection of hybrids exhibiting tigrina‐like coat patterns may suggest (1) asymmetric hybridization of G. tigrina males to females of other species and (2) positive selection for tigrina‐like phenotype in South African habitats, but these hypotheses will have to be further tested using other sources of evidence. Despite the precise mosaic of hybrid zones identified in southern African genets, the environmental factors that shape patterns of distribution of hybrids remain unclear. Nevertheless, in the light of our range reassessment, it appears that seasonality of precipitation and periods of annual frost may play stringent roles in the distribution of genets. The complementarity of our results based on morphology and molecules is regarded as encouraging for the further development of integrative approaches in order to better understand the complex phenomena that underlie hybridization processes. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 86 , 11–33.     

The influence of tectonics,sea‐level changes and dispersal on migration and diversification of Isonandreae (Sapotaceae)

Internal transcribed spacer (ITS) ribosomal DNA sequence data were generated for 80 of the c. 200 species of Isonandreae and were added to data from African and Neotropical representatives in subfamily Sapotoideae and outgroups in Sapotaceae. Bayesian dating and ancestral area reconstruction indicated that Isonandreae are derived from within an African grade. Multiple Australasian species or lineages are derived from Sundanian lineages in South‐East Asia with stem ages originating from the late Oligocene. Sri Lankan and Indian lineages are also derived from Sundanian lineages. Our results are consistent with migration from Africa into Sundania followed by numerous over‐water dispersal events across Wallace's Line into Australasia and migration from Sundania to the Indian subcontinent. Pleistocene speciation indicates that sea‐level changes during that epoch could have been responsible for some species diversification in Sundania. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174 , 130–140.     

Parallel evolution of flower reduction in two alpine Soldanella species (Primulaceae)

The European endemic Soldanella has traditionally been divided into two morphologically well‐defined sections. Section Tubiflores contains two species growing in high‐elevation habitats, whereas most of the 14 species of section Soldanella inhabit montane forests. Section Tubiflores has a reduced floral morphology compared with section Soldanella. A previous phylogenetic study based on internal transcribed spacer (ITS) and AFLP data has revealed that, although the genus Soldanella itself is monophyletic, both sections are paraphyletic. Soldanella alpina (section Soldanella) forms a clade with S. minima and S. pusilla (section Tubiflores), and the grouping of S. alpina with S. pusilla has been hypothesized to be the result of hybridization between S. pusilla and an unidentified species of section Soldanella. We re‐examined the phylogenetic relationships among the above species using additional sequence data (plastid DNA) and increasing the sample for ITS and AFLP data. Our new data confirmed that S. alpina is most closely related to S. pusilla. However, our data do not provide any evidence in support of the hypothesis that S. alpina is a hybrid species. In consequence, we consider it likely that the two species of section Tubiflores originated independently. The reduced floral morphology of these two alpine species is probably evidence for increased levels of self‐pollination, ensuring reproductive success in a high‐altitude habitat. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 409–422.