Reproductive Isolation Research Articles

Phase separation of S-RNase promotes self-incompatibility in Petunia hybrida.

Self-incompatibility (SI) is an intraspecific reproductive barrier widely present in angiosperms. The SI system with the broadest occurrence in angiosperms is based on an S-RNase linked to a cluster of multiple S-locus F-box (SLF) genes found in the Solanaceae, Plantaginaceae, Rosaceae, and Rutaceae. Recent studies reveal that non-self S-RNase is degraded by the Skip Cullin F-box (SCF)SLF-mediated ubiquitin-proteasome system in a collaborative manner in Petunia, but how self-RNase functions largely remains mysterious. Here, we show that S-RNases form S-RNase condensates (SRCs) in the self-pollen tube cytoplasm through phase separation and the disruption of SRC formation breaks SI in self-incompatible Petunia hybrida. We further find that the pistil SI factors of a small asparagine-rich protein HT-B and thioredoxin h together with a reduced state of the pollen tube all promote the expansion of SRCs, which then sequester several actin-binding proteins, including the actin polymerization factor PhABRACL, the actin polymerization activity of which is reduced by S-RNase in vitro. Meanwhile, we find that S-RNase variants lacking condensation ability fail to recruit PhABRACL and are unable to induce actin foci formation required for pollen tube growth inhibition. Taken together, our results demonstrate that phase separation of S-RNase promotes SI response in P. hybrida, revealing a new mode of S-RNase action.

Local adaptation and reproductive isolation: when does speciation start?

Abstract The speciation process often takes a long time. The speciation continuum framework has been useful to reconstruct the evolutionary processes that result in the formation of new species but defining when this continuum starts is far from trivial. Although a panmictic population is often considered the initial condition of speciation, this is unrealistic for almost all species. Local or divergent adaptation are viewed by many researchers as processes that shape intraspecific diversity and thus are not part of speciation. We propose that speciation starts when reproductive isolation becomes greater than zero, arguing in favour of the alternative view that local adaptation necessarily involves some reproductive isolation, independently of whether it results in the completion of speciation. Given that local adaptation is widespread, the consequence is that most species are constantly in the process of speciating. The process of speciation is best represented as the formation of separate subnetworks, defined by reproductive isolation, within extended and fluid spatial networks of populations.

Speciation across life and the origins of biodiversity patterns

Abstract Speciation is the original source of all species richness. Here, I address two questions: (i) what might typical speciation look like across life? and (ii) how has speciation led to the diversity of life we see today? What is ‘typical’ depends on the richness of different groups. In groups associated with host organisms (which may dominate numerically), the processes of co-speciation and host switching are crucial. Among free-living organisms, allopatric speciation, ecological divergence, and prezygotic isolation appear widely important. Yet, the processes by which species become allopatric (and initially split) remain highly unclear. Among macroscopic organisms, the processes underlying the speciation of cryptic insect lineages may predominate, and are briefly reviewed here. Analyses of diversification rates among clades can illuminate the factors that drive speciation and species richness, and I review the advantages and disadvantages of different methods for estimating diversification rates. Patterns of species richness among named clades are generally related to variation in diversification rates, and specific types of ecological variables seem to underlie variation in diversification rates at different scales. Nevertheless, many richness patterns are unrelated to diversification rates and may be related to the time available for speciation instead, including richness among regions, clades, and traits.

Host-specific monogeneans parasitizing freshwater fish: The ecology and evolution of host-parasite associations.

Monogenea (Platyhelminthes), mainly gill and fin ectoparasites of fish, are often recognized as host specific and morphologically and ecologically diverse. These parasites exhibit high species diversity at the level of host species or individual fish specimens. Using case studies, especially those widely performed in Dactylogyrus parasitizing cyprinoid fish, this article presents current knowledge on the ecology and evolution of congeneric gill monogeneans. The important aspects of the ecology of congeneric monogeneans are highlighted, in particular: host specificity expressed at several host levels (from strict specificity to phylogenetic specificity), microhabitat specificity expressed by restricted positions on fish gills to facilitate intraspecific mating, and the link between microhabitat preference and morphological adaptation (i.e., sclerotized structures of the haptor) or reproductive isolation. From the evolutionary perspective, this study focused on the processes of the speciation and diversification of congeneric monogeneans, highlighting the role of host switch as the most prominent coevolutionary event, accompanied in some cases mostly by intrahost speciation or cospeciation, as revealed by cophylogenetic studies. Here, important knowledge on evolutionary patterns of host specificity, microhabitat specificity, and morphological adaptation is presented. Host-specific monogeneans may represent an important tool for studying the historical biogeography of their hosts. Specifically, in the case of freshwater fish hosts exhibiting disjunctive distribution, they reflect both historical and contemporary contacts. The role of host-specific congeneric monogeneans in revealing historical intercontinental and intracontinental contacts between freshwater fish is highlighted. Finally, the importance of the role of genetic coadaptation, limiting the presence of host-specific monogeneans in hybrid fish, is emphasized.

From microcosm to macrocosm: adaptive radiation of Darwin’s finches

Abstract In this Perspective we show the value of studying living organisms in the field to understand their history. Darwin’s finches are an iconic example of the early stages of speciation in a young adaptive radiation that produced 18 species in little more than a million years. The question they pose is how and why so many species originated and diversified rapidly. A long-term study of four species of finches on the small island of Daphne Major, combined with genomic investigations, provide some answers in terms of extrinsic and intrinsic factors. Beak size and shape, as well as body size, are key heritable features involved in both ecological and reproductive isolation, and their evolution by natural selection was caused by competitor species during prolonged droughts. Introgressive hybridization of related species is rare but recurring, apparently widespread, increases genetic variation, and does not incur a fitness cost. Hybridization can produce a new species. We use a phylogeny based on whole genome sequences of the four finches to infer morphological transitions in their radiation. Several lines of evidence indicate that some species are missing from the early phase of the radiation due to extinction. Combining these results, we re-cast the classical allopatry-then-sympatry theory of adaptive radiation as a competition-selection-hybridization process that generates a diversity of species.

A microbial perspective on speciation

Abstract Understanding what a microbial species is and the process of speciation in microbes has been and still is a puzzle with many challenges. But there is now emerging consensus that speciation in microbes does follow certain rules and limitations. Just like in macrobes, it can be driven by divergent natural selection and is maintained by barriers to gene flow, either genetic or ecological in nature. However, whether microbial speciation mirrors that of sexually reproducing eukaryotes is up for debate, as extensive horizontal gene flow can blur patterns and processes. Here, I provide intriguing examples of speciation in bacteria, viruses, and yeast, which are arguably similar to what we see in eukaryotes. I synthesize recent insights from microbial evolutionary genomics, which may mitigate the traditional view that microbes are ‘messy’ and do not fit eukaryotic species concepts and speciation models. Finally, I highlight the benefits of microbial experimental evolution to answer fundamental questions in speciation research (especially why, how, and when speciation occurs). Speciation research with microbes, as opposed to the organisms traditionally used in this field, may suffer less from observational bias and the experimental control we have over selection types, gene flow, and reproductive modes in microbial systems may allow us to determine the mechanisms and timing of ecological divergence, reproductive isolation, and speciation.

Meiotic deviations and endoreplication lead to diploid oocytes in female hybrids between bighead catfish (Clarias macrocephalus) and North African catfish (Clarias gariepinus).

Reproductive isolation and hybrid sterility are mechanisms that maintain the genetic integrity of species and prevent the introgression of heterospecific genes. However, crosses of closely related species can lead to complex evolution, such as the formation of all-female lineages that reproduce clonally. Bighead catfish (Clarias macrocephalus) and North African catfish (C. gariepinus) diverged 40 million years ago. They are cultivated and hybridized in Thailand for human consumption. Male hybrids are sterile due to genome-wide chromosome asynapsis during meiosis. Although female hybrids are sometimes fertile, their chromosome configuration during meiosis has not yet been studied. We analyzed meiosis in the hybrid female catfish at pachytene (synaptonemal complexes) and diplotene (lampbrush chromosomes), using immunostaining to detect chromosome pairing and double-stranded break formation, and FISH with species-specific satellite DNAs to distinguish the parental chromosomes. More than 95% of oocytes exhibited chromosome asynapsis in female hybrid catfish; however, they were able to progress to the diplotene stage and form mature eggs. The remaining oocytes underwent premeiotic endoreplication, followed by synapsis and crossing over between sister chromosomes, similar to known clonal lineages in fish and reptiles. The occurrence of clonal reproduction in female hybrid catfish suggests a unique model for studying gametogenic alterations caused by hybridization and their potential for asexual reproduction. Our results further support the view that clonal reproduction in certain hybrid animals relies on intrinsic mechanisms of sexually reproducing parental species, given their multiple independent origins with the same mechanism.

High sexual display trait diversity without measured genetic divergence in a montane hybrid zone involving young species (Habronattus americanus subgroup, Araneae: Salticidae)

Abstract Genetic introgression, allele exchange across species boundaries, is a commonly recognized feature of animal evolution. Under such a paradigm, contemporary contact zones provide first-hand insight into the geographic, phenotypic, and genetic details of introgression. Also, when mate choice phenotypes are conspicuous and variable in hybrids, contact zones provide potential insight into how sexual selection interacts with species boundary maintenance, particularly when postzygotic reproductive isolation is weak. The Habronattus americanus subgroup includes several recently evolved jumping spider species, with an estimated age of about 200,000 yr, and substantial evidence for hybridization and introgression. We explored a contact zone involving H. americanus (Keyserling, 1885) and H. kubai (Griswold, 1979) on Mount Shasta, CA, in alpine habitats that would have been unavailable (under ice) at the Last Glacial Maximum. We characterized morphological diversity within the contact zone, including the fine-scale geographic distribution of hybrid and parental individuals, and assessed genetic variation using ddRADseq data. Combined results indicate a lack of measured genomic differentiation between specimens with distinct morphologies, including individuals with phenotypes of the parental species. We identified a diverse array of hybrid morphologies, with phenotypic evidence for backcrossing, essentially forming a phenotypic bridge between parental taxa. The study area is characterized by more hybrid than parental individuals, with a significantly larger number of red-palped morphologies than white- and/or yellow-palped morphologies; the novel, white-palped phenotype is perhaps transgressive. Overall, these results contribute to a better understanding of the expected ebb and flow of lineage interactions during the early stages of speciation.

Adolescent girls' sexual and reproductive health information needs and barriers in Cape Town.

The sexual and reproductive health (SRH) information needs of adolescent girls in developing countries are not being met. The study explored the sexual and reproductive health information needs, information-seeking behaviour and barriers among adolescent girls in the Western Cape, South Africa. The study was conducted in the South eastern sub district of Cape Town metropole. The study was conducted at one of the high schools in a highly populated area in the Cape Town metropole. Semi-structured interviews were conducted with 17 adolescent girls aged 16-17 years, who were recruited using purposive sampling techniques. The interviews were audio recorded and transcribed verbatim. Data were analysed using an inductive thematic analysis framework. Three themes emerged from the data: (1) adolescent girls exhibit limited awareness and comprehension of sexual and reproductive health; (2) the information-seeking behaviours of adolescent girls regarding sexual and reproductive health and (3) barriers to seeking information. The establishment of primary healthcare facilities that are friendly to adolescents, combined with impactful reproductive health education and improved parent-adolescent girl relations, is crucial for promoting sexual and reproductive health among adolescent girls. The study offered valuable insights into the SRH information needs, information-seeking behaviour and barriers faced by adolescent girls in accessing SRH information sources and services. These barriers include lack of knowledge about SRH and contraception, challenges within family dynamics, difficulties accessing friendly healthcare services and encountering negative attitudes from healthcare professionals.

Variable success in linking micro- and macroevolution

Abstract Attempts to predict macroevolution from microevolution, and microevolution from macroevolution, when natural selection is the main cause have met with varying success. Explanations for failure are numerous, but the reasons are uncertain even when a link is found. Here, I discuss possible explanations for outcomes of three efforts and ways to test them. First, quantitative genetic variation within populations often predicts directions of species divergence with surprising accuracy. Natural selection probably contributes to this pattern, but the evidence suggests that even long-term phenotypic evolution is influenced by enduring genetic biases. Second, the rate of evolution of reproductive isolation repeatedly fails to predict species diversification rates for unknown reasons. Suspicion falls on the influence of ecological and population demographic processes that might play a dominant role in the net rate of accumulation of species, an idea as yet little tested. Third, macroevolutionary patterns in the distribution of phenotypes of species in clades can in principle predict selection coefficients in diverging populations. I use the concept of adaptive landscape to suggest why the macroevolutionary signal of divergent selection is strongest at the time of splitting and why little information about selection coefficients from phylogenetic methods remains in the long run. Estimating adaptive landscapes from first principles would facilitate further efforts to link microevolution and macroevolution.

Assessing fall armyworm (Spodoptera frugiperda) allochronic behavior as a predictor of local strain composition in United States populations.

The fall armyworm, Spodoptera frugiperda (J.E. Smith), is comprised of two genetically distinct strains that are morphologically identical yet exhibit differences in their behavior and physiology (C-strain and R-strain). Evidence of ongoing genetic differentiation between strains highlights the importance of considering strain identity in research and management of fall armyworm populations, but the logistical and technical burden of genotyping limits strain-specific applications. Controlled experiments with laboratory colonies have shown that the strains engage in allochronic ("allo" - different, "chronic" - time) mating behavior, with C-strain mating early in the evening (0-5 hours after sunset) and R-strain mating late in the evening (5-10 hours after sunset). Using temporal field collections and genotype data, we show that strain-specific variation in allochronic male mating behavior occurs across Texas and Florida fall armyworm populations, both of which act as primary source populations for annual migrations of this pest into the continental United States. Time of capture in pheromone traps was significantly different between strains in both Texas and Florida, with the R-strain males consistently being collected in the traps late in the night. The C-strain males were generally captured earlier in the night than their R-strain counterparts, though there was notable variation in the timing between nights and across locations. Allochronic behavior in field populations is consistent with previous laboratory studies reporting differences in the timing of mating between the strains, however increased variability in behavior within and across native populations was observed. Although allochronic behavior in local populations may partially contribute to reproductive isolation between the strains, the behavior is not consistent enough to serve as a complete reproductive barrier. Furthermore, the observed variability in behavior both within and between independent sampling events, especially in the C-strain, poses a challenge to the development of models that utilize time of capture as a predictive phenotype for monitoring strain identity in local populations.

Ancient Endemic or Recent Invader? Phylogenetic Position and the Probable Origin of the Ccladoceran Diaphanosoma macedonicum (Diplostraca, Sididae) from the Ancient Lakes in the Balkans.

Ancient lakes contain unique and very vulnerable fauna. Determining and understanding the origin of such biodiversity is a key factor in promoting conservation and management actions in some of the most singular ecosystems on the planet. Lake Ohrid in the Balkans is known as a natural laboratory for speciation, containing a high number of endemic species. However, the identity and origin of the planktonic cladoceran Diaphanosoma is uncertain. Representatives of the genus were long considered to have invaded the lake, but recent morphological studies have suggested that they belonged to the endemic taxon in the Balkans, D. macedonicum. Here, phylogenetic methods based on two mitochondrial gene fragments (COI and 16S) were used to identify Diaphanosoma specimens from the ancient Lake Ohrid and Lake Prespa in the Balkans and compare them with other species in Europe, including those living in nearby water bodies. Molecular evidence showed that D. macedonicum was constrained to the ancient lakes Ohrid, Prespa, and Mikri Prespa, which suggests reproductive isolation within the lakes. Phylogenetic analyses supported previous morphological assessments and situated D. macedonicum within the D. mongolianum species group, which contains three sibling species (D. mongolianum, D. lacustris, and D. macedonicum). Nuclear markers are needed to study intraspecific gene flow in these organisms and discard a potential formation of hybrids.

Beyond extinction: Uncovering morphological aspects of the last typotherid population (Mesotherium cristatum) and the unexpected body mass decrease

We present a detailed analysis of the craniomandibular and dental remains of Mesotherium cristatum, the quaternary mesotheriid typotherid notoungulate, from Corralito, Santa María Department, Cordoba Province. This population represents the final lineage of Typotheria during middle Pleistocene, Post-Ensenadan Age (>220 ± 13 ka). We compared these new craniomandibular and postcranial samples from Corralito with those from Toscas del Río de La Plata, as well as other localities in the province of Buenos Aires dating to the Ensenadan Age 1.98–0.4 Ma). Our investigation reveals a substantial decline in the size and body mass of the last known population of M. cristatum during the Bonaeran Age period, before its extinction. This occurrence, hitherto unrecorded in any prior South American Land Mammal Age leading up to extinction, might be attributed to the climatic and abiotic changes of the Pleistocene. These changes notably caused a marked reduction in the paleobiogeographical distribution area ofM. cristatum during the Middle Pleistocene. This size and body mass reduction, possibly an outcome of compelled reproductive isolation, is situated against the context of global cooling and heightened predatory pressures. Moreover, our analysis unveiled distinctive taxonomic attributes specific to this taxon, we compare dental size and find a preliminary evidence of an accelerated tooth replacement pattern. Furthermore, we have effectively updated the faunal composition information of the Corralito deposit, elucidating previous biostratigraphic inferences that had led to the belief of Corralito being an Ensenadan Age site. This adjustment impacts the first appearance datum (FAD) of the Neolicaphrium recens proterotheriid litoptern, younger than previously estimated and revised Bonaerian-Lujanian. Finally, this study provides insights into the biological analysis of the iconic species M. cristatum, prevalent in the South American quaternary of the Pampean region. It unreveils new faunal features specific to the Pampean region, shedding light particularly on the lesser-explored western area. These findinngs provide crucial insight into the ever-evolving ecosystem dynamics during the Middle Pleistocene.

Assisted Reproduction for a Same-Sex Couple: Interdisciplinary Preclinical Active Learning Module Combining Case-Based Small Group Discussion and Patient Panel.

Physicians often feel they are not equipped to serve the lesbian, gay, bisexual, and queer (LGBTQ) community, but integrating education that incorporates LGBTQ content and perspective into an already-condensed medical school curriculum is challenging. We developed a preclinical active learning module on assisted reproductive technologies (ART) in LGBTQ care, integrating clinical and basic science content with patient perspective. We created a module that combined a case-based small group discussion with a patient panel. We developed a case for discussion in collaboration with a female cis-gender same-sex couple who conceived through ART. A patient panel with the same couple followed the discussion. All first-year medical students attended both parts of the module. Prior to participation, students learned reproductive endocrinology and genetics concepts through lectures. After the module, students voluntarily completed an anonymous survey to evaluate self-perceived changes in familiarity and confidence with LGBTQ patients and satisfaction with the module. Of the 126 students who attended, 72 (57%) completed the survey. Of these, 69 (95.8%) felt the module gave them better perspectives on LGBTQ patient experiences, and 66 to 69 (92-96%) agreed the small group discussion achieved its learning objectives on LGBTQ health barriers and the application of ART. Students valued the patient panel (84.7%) and cited a better understanding of reproductive barriers for LGBTQ patients as its most valuable point. A preclerkship module combining a case-based small group discussion and patient panel on ART delivered in the context of a real-life LGBTQ patient experience provided an opportunity for the students to integrate basic science and clinical science knowledge to reflect on the healthcare needs of this patient population. Creating the case in collaboration with the same-sex couple and having them present their own experience provided an authentic perspective to students on reproductive healthcare issues and how they impact members of the LGBTQ community.

Multiple amino acid changes are responsible for the shift of tuning breadth along the evolutionary trajectory of a moth pheromone receptor.

Sex pheromone recognition is essential for mating in many insects and plays a major role in maintaining reproductive barriers. A previous study from our lab reported the evolutionary history of the pheromone receptor OR5 in Spodoptera moths. Using heterologous expression in Xenopus oocytes and site-directed mutagenesis, we found that eight amino acid substitutions were sufficient to recapitulate the evolution from an ancestral broadly-tuned to a highly specific receptor. Here, we confirmed this result using expression in Drosophila olfactory neurons. This further confirmed that multiple amino acid changes explain the shift in tuning breadth of Spodoptera OR5 during evolution.

Protective Measures for Dalian Spotted Seal Reserve

Dalian Spotted Seal Reserve is one of the eight harbor seal breeding areas in the world. Leopard seals in the Liaodong Bay breeding area lack genetic gene exchange with other breeding areas in the world, and there is a phenomenon of reproductive isolation. They belong to a branch of the world's independently evolved leopard seals and have their own unique genetics, so are of high conservation value in this regard. This paper highlights the benefits that aquaculture and captive breeding bring to protected areas. The focus of aquatic products is mainly on the bottom-sown varieties. There is a foundation for artificial breeding, and what people need to do is to continue to expand the number and scope when there is sufficient funding. At the same time, this paper will clarify the relationship between them, and explain the measures and development of seal protection from the biological and economic perspectives. Both focus studies could help further protect seals.

A comprehensive evolutionary scenario for the origin and neofunctionalization of the Drosophila speciation gene Odysseus (OdsH).

Odysseus (OdsH) was the first speciation gene described in Drosophila related to hybrid sterility in offspring of mating between Drosophila mauritiana and Drosophila simulans. Its origin is attributed to the duplication of the gene unc-4 in the subgenus Sophophora. By using a much larger sample of Drosophilidae species, we showed that contrary to what has been previously proposed, OdsH origin occurred 62 MYA. Evolutionary rates, expression, and transcription factor-binding sites of OdsH evidence that it may have rapidly experienced neofunctionalization in male sexual functions. Furthermore, the analysis of the OdsH peptide allowed the identification of mutations of D. mauritiana that could result in incompatibility in hybrids. In order to find if OdsH could be related to hybrid sterility, beyond Sophophora, we explored the expression of OdsH in Drosophila arizonae and Drosophila mojavensis, a pair of sister species with incomplete reproductive isolation. Our data indicated that OdsH expression is not atypical in their male-sterile hybrids. In conclusion, we have proposed that the origin of OdsH occurred earlier than previously proposed, followed by neofunctionalization. Our results also suggested that its role as a speciation gene might be restricted to D. mauritiana and D. simulans.

An experimental test of the evolutionary consequences of sympatry in Drosophila subquinaria.

Prezygotic isolation is often stronger between sympatric as opposed to allopatric taxa, but the underlying cause can be difficult to infer from comparative studies alone. Experimental evolution, where evolutionary responses to treatments manipulating the presence/absence of heterospecific individuals are tracked, can provide a powerful complementary approach. We used experimental evolution to investigate a naturally occurring pattern of reproductive character displacement in the mushroom-feeding fly, Drosophila subquinaria. In nature, female D. subquinaria from populations sympatric with the closely related Drosophila recens discriminate more strongly against heterospecific males than do females from allopatric populations. Starting with 16 replicate allopatric populations of D. subquinaria, we manipulated the presence/absence of D. recens during mating (experimental sympatry vs. control) and, when present, we allowed hybrids to live or kill them each generation. Across 12 generations, heterospecific offspring production from no-choice mating trials between D. subquinaria females and D. recens males declined in both experimental sympatry treatments relative to the control, suggesting increased sexual isolation. Male cuticular hydrocarbon profiles also evolved, but only in the hybrids killed treatment. Our results strongly imply that the existing reproductive character displacement in wild D. subquinaria populations was an evolutionary response to selection arising from secondary contact with D. recens.

Synthesis and Scope of the Role of Postmating Prezygotic Isolation in Speciation.

How barriers to gene flow arise and are maintained are key questions in evolutionary biology. Speciation research has mainly focused on barriers that occur either before mating or after zygote formation. In comparison, postmating prezygotic (PMPZ) isolation-a barrier that acts after gamete release but before zygote formation-is less frequently investigated but may hold a unique role in generating biodiversity. Here we discuss the distinctive features of PMPZ isolation, including the primary drivers and molecular mechanisms underpinning PMPZ isolation. We then present the first comprehensive survey of PMPZ isolation research, revealing that it is a widespread form of prezygotic isolation across eukaryotes. The survey also exposes obstacles in studying PMPZ isolation, in part attributable to the challenges involved in directly measuring PMPZ isolation and uncovering its causal mechanisms. Finally, we identify outstanding knowledge gaps and provide recommendations for improving future research on PMPZ isolation. This will allow us to better understand the nature of this often-neglected reproductive barrier and its contribution to speciation.

Maintenance of species boundaries amid hybridization in two island gingers with similar ecological niches.

Understanding species boundaries maintenance in the face of hybridization/introgression is an intriguing yet complex topic in evolutionary biology. The underlying mechanisms, however, remain elusive. To address this, we propose to investigate the role of climatic shifts in shaping genetic structure and influencing species boundaries. We combine multilocus genetic data and species distribution modeling to explore how past and current climatic shifts affect the genetic structure and demographic history of two Taiwan endemic gingers, Zingiber pleiostachyum and Z. shuanglongense. We identified a well-delimited genetic structure with evidence of admixture, indicating incomplete reproductive isolation between the two gingers. This is likely due to secondary contact and range overlap during the last glacial maximum, leading to sporadic instances of hybridization. Niche overlap tests based on climate and soil data indicate that these two gingers occupy similar but nonidentical ecological niches. Furthermore, we found that the considerable differences in their current geographic distribution and altitude preferences might have resulted from different seed dispersal capabilities and competitive exclusion due to their similar niche preferences. Our results reveal a model where altitudinal differentiation and dispersal strategy synergistically reinforce the species divergence, thereby illuminating the importance of these factors in shaping and maintaining the island's biodiversity.