Allopatric Research Articles

Lineage diversity in a Melanesian lizard radiation (Gekkonidae: Nactus) further highlights exceptional diversity and endemism in eastern Papua New Guinea

AbstractNew Guinea and surrounding islands are home to some of the richest assemblages of insular biodiversity in the world. The key geological drivers of species richness in this region are largely considered to be mountain uplift and development of offshore archipelagos—some of which have accreted onto New Guinea—with the role of mountain uplift and elevational gradients receiving more attention than the role of isolation on islands. Here, we examine the distribution of lineage richness and body-size diversity in a radiation of Melanesian lizards that is almost entirely absent from montane habitats but closely associated with islands—the geckos of the genus Nactus. Our data indicate that eastern New Guinea—centred on the East Papuan Composite Terrane (EPCT)—shows particularly high levels of endemism and body-size diversity and is also inferred to be a source area for multiple independent colonisations elsewhere in New Guinea, the Pacific and Australia. Two Nactus lineages in Australia have closest relatives occurring to the north of New Guinea’s Central Cordillera, suggesting dispersal through this area in the mid-Miocene, possibly via seaways that would have isolated the islands to the east and west of the proto-Papuan region. Syntopic species tend to differ in body length; however, at a phylogenetic scale, this trait appears to be conservative, with small-sized and large-sized species clustered into separate lineages. These data suggest that species richness in Melanesian Nactus is in part explained by morphological diversification enabling the presence of sympatric communities to exist, but to a greater extent by multiple instances of dispersal and extensive allopatric and parapatric speciation, especially in and around the islands of the EPCT.

Molecular phylogenetic relationships among lineages in the genus Carabus (Coleoptera: Carabidae) and radiation of the subgenus Apotomopterus

Abstract The genus Carabus (Coleoptera: Carabidae: Carabinae) is a group of predacious ground beetles found throughout Holarctic temperate zones. The diversification of this group is attributed not only to allopatric speciation but also to diversification in life-history traits and morphological traits that are involved in ecological adaptation and reproductive isolation. Precise phylogenetic reconstruction of Carabus is important to understanding the factors associated with species’ divergence in relation to such character divergence. Here, we analyse the phylogeny of Carabus among higher taxonomic groups and among species of the subgenus Apotomopterus, a hyper-diverse group endemic to East Asia. We used genome-wide sequence data from ultraconserved elements for phylogenetic reconstruction via maximum-likelihood and species-tree reconstruction methods. With regard to the relationships among higher taxonomic groups, the obtained phylogenetic trees resolved two structures with previously unresolved divergence. The subgenus Apotomopterus contained three lineages, i.e. the Vitalisi, Prodigus, and Sauteri groups. It showed diversification of the spinula, a sclerotized male genital structure, and variation in the female elytral notch (preapical emargination). These morphological traits may be involved in copulatory behaviour and potentially affect reproductive isolation, and their character state divergence may have facilitated species divergence of Apotomopterus.

Smaller islands, bigger appetites: evolutionary strategies of insular endemic skinks.

Competitive dietary and morphological divergence among co-occurring species are fundamental aspects of ecological communities, particularly on islands. Cabo Verde (~570 km west of continental Africa) hosts several endemic reptiles descended from common ancestors, with sympatric species exhibiting wide morphological variation and competing for limited resources. To explore the mechanisms of resource partitioning between coexisting species, DNA metabarcoding was used to compare the diets of large and small skinks, Chioninia vaillantii and Chioninia delalandii, in sympatric and allopatric contexts on Fogo Island and in a more competitive context on the small and resource-poor Cima Islet. The morphological variation of all populations was also examined to test the character displacement hypothesis and to compare the effect of different competitive scenarios. Results showed significant differences in diet and linear measurements between species and populations. The two sympatric populations of C. delalandii on Fogo and Cima showed similar changes in head morphology compared to the allopatric population, supporting character displacement. The effect of higher competitive pressure on Cima was evidenced by the increased morphological and dietary variation observed. This study demonstrates how sister species develop dietary adaptations/morphologies to maintain stable coexistence, especially in highly competitive scenarios, providing useful insights for effective conservation strategies.

High-quality genome of a novel Thermosynechococcaceae species from Namibia and characterization of its protein expression patterns at elevated temperatures.

Thermophilic cyanobacteria thrive in extreme environments, making their thermoresistant enzymes valuable for industrial applications. Common habitats include hot springs, which act as evolutionary accelerators for speciation due to geographical isolation. The family Thermosynechococcaceae comprises thermophilic cyanobacteria known for their ability to thrive in high-temperature environments. These bacteria are notable for their photosynthetic capabilities, significantly contributing to primary production in extreme habitats. Members of Thermosynechococcaceae exhibit unique adaptations that allow them to perform photosynthesis efficiently at elevated temperatures, making them subjects of interest for studies on microbial ecology, evolution, and potential biotechnological applications. In this study, the genome of a thermophilic cyanobacterium, isolated from a hot spring near Okahandja in Namibia, was sequenced using a PacBio Sequel IIe long-read platform. Cultivations were performed at elevated temperatures of 40, 50, and 55°C, followed by proteome analyses based on the annotated genome. Phylogenetic investigations, informed by the 16S rRNA gene and aligned nucleotide identity (ANI), suggest that the novel cyanobacterium is a member of the family Thermosynechococcaceae. Furthermore, the new species was assigned to a separate branch, potentially representing a novel genus. Whole-genome alignments supported this finding, revealing few conserved regions and multiple genetic rearrangement events. Additionally, 129 proteins were identified as differentially expressed in a temperature-dependent manner. The results of this study broaden our understanding of cyanobacterial adaptation to extreme environments, providing a novel high-quality genome of Thermosynechococcaceae cyanobacterium sp. Okahandja and several promising candidate proteins for expression and characterization studies.

Coping with climate change: A livelihood vulnerability and adaptation analysis in Gaibandha, Rangpur, Bangladesh

AbstractThis study aimed to assess the impact of climate change using the Livelihood Vulnerability Index (LVI) and the adaptation strategies of communities, as measured by the Adaptation Strategy Index (ASI), among 120 households across six villages in Fulchari and Shaghata Upazilas of Gaibandha district in northern Bangladesh. The findings highlight changing climatic patterns and show that while respondents are generally aware of the impacts of climate change, there are notable knowledge gaps. Galna Adarshapara was identified as the most vulnerable village according to the LVI, indicating its high susceptibility in areas such as socio‐demographic profile, food security, health, natural hazards, and climate sensitivity. Factors contributing to this vulnerability include geographical isolation, limited education, underdeveloped infrastructure, inadequate health facilities, and a lack of alternative income sources during extreme events. However, coping mechanisms such as irrigation, crop diversification, and the use of double‐platform tube wells are commonly employed to address these climatic impacts. To enhance resilience, it is crucial to implement policy initiatives and institutional arrangements that support local communities in improving their living conditions and adapting to climate change challenges.

Comparative analysis reveals assortative mate preferences in darters independent of sympatry and sex.

A preference for mating with conspecifics over heterospecifics is fundamental to the maintenance of species diversity in sexually reproducing organisms. This type of positive assortative preference results in sexual isolation, and a reduction in gene flow between species due to differences in mate choice. The proximate and ultimate causes of sexual isolation therefore constitute active areas of research in evolutionary biology. Sexual isolation is often stronger between closely related sympatric species as compared to allopatric species because of processes such as reinforcement. In addition, traditional theories of sexual selection suggest that because reproduction is more costly to females, they should be the choosier sex and play a more central role in sexual isolation. We conducted a comparative analysis of assortative mate preferences in males and females of sympatric and allopatric species pairs of darters (fish genus Etheostoma). We performed a meta-analysis of 17 studies, encompassing 21 species, in which assortative preference was measured when fish were (in most cases) allowed only visual information. As expected, we found stronger preferences for conspecifics over heterospecifics across studies and species. However, we did not find an effect of sympatry or sex on the strength of preference for conspecifics, but rather remarkable variation across species. We offer several testable hypotheses to explain the variation we observed in the strength of assortative preference.

Host-driven phenotypic and phenological differentiation in sympatric races of a parasitic plant

Host specificity is a key factor influencing the ecology and evolutionary diversification of parasitic organisms. Host specialisation and geographic isolation are known to lead to the genetic differentiation of allopatric races in parasitic plants. However, how divergence can co-occur in sympatry remains largely unknown. We investigated phenological and phenotypic differentiation and potential reproductive isolation among three sympatric genetic races of Cytinus hypocistis (Cytinaceae) - an extreme endophytic holoparasite with a high degree of host specialisation. We compared spatio-temporal variations in flowering phenology, flower production, floral longevity, floral rewards, and morphology, and conducted inter-race pollinations among three races parasitising Cistus ladanifer, C. salviifolius, and Halimium halimifolium (Cistaceae) in six co-occurring populations. We found that host-defined genetic races differed significantly across multiple phenotypic and phenological aspects – a phenomenon previously overlooked due to the plants’ cryptic morphology. The race parasitising H. halimifolium showed earlier blooming, higher floral display, longer flowers, and higher pollen production and nectar concentration; the race on C. salviifolius showed later flowering, significantly lower floral display and smaller flowers with lower floral rewards; the race on C. ladanifer had intermediate characteristics. Genetic races were interfertile yet may remain differentiated by restricted gene flow and host-driven selection pressures. Together, our data point to a rare case of sympatric divergent evolution hiding in plain sight: apparently morphologically similar co-occurring parasite races can be genetically, phenotypically, and phenologically distinct. This hitherto unreported example of host-driven sympatric diversification challenges how species concepts are applied to cryptic parasitic plant races.

Multiple origins of freshwater invasion and parental care reflecting ancient vicariances in the bivalve family Cyrenidae (Mollusca)

Habitat transitions in living organisms are key innovations often coupled with species diversification after their successful adaptation to new environment. The Cyrenidae is among the most well-known heterodont bivalve groups that have successfully invaded freshwater systems from brackish water environments and display diverse lineage-specific developmental modes. Phylogenetic and molecular clock-based divergence time analyses using 12 complete mitochondrial genome sequences suggest that Cyrenidae species independently colonized freshwater habitats during three distinct spatial and geological periods: one from the American continents approximately in the Early Jurassic and the two others from Australasian/East Asian continents in the Early/Middle Cretaceous and the Paleogene-Neogene boundary, respectively. This study provides significant insight into the temporal and spatial patterns of multiple freshwater invasions, aligning with ancient vicariance events inferred from different geological timelines of plate tectonics. Additionally, mitogenome phylogeny confirms the earlier hypothesis of the repeated parallel evolution of parental care system within this bivalve group.

Phylogeny, historical biogeography and climate niche differentiation in extant species of Ceratophryidae (Anura, Hyloidea) frogs in South America

Ceratophryidae is a family of frogs containing twelve extant species distributed in South America. Several studies have been carried out concerning the systematics, morphology, karyotypes, and behaviour within this monophyletic family. However, little is known about the historical biogeography and the divergence in time of this group. Here, we present an updated phylogeny, along with a calibrated chronogram, to analyse the historical biogeographical pattern and climate niche differentiation among extant species of Ceratophryidae (Anura: Hyloidea) frogs in South America. A phylogeny based on morphological and genetic data was obtained from 256 morphological characters, six mitochondrial and eight nuclear genes for up to a total of 8428 characters in the homological matrix. Our results indicate that the genus Ceratophrys is sister to the clade Chacophrys + Lepidobatrachus. The divergence of the crown group of Ceratophryidae is estimated to have occurred 19.2 Ma at the beginning of the Miocene, with recent cladogenetic events related to the late Miocene (10.18–13.70 Ma) and the Pliocene (~5.3–2.6 Ma). Moreover, the Cerrado region is estimated to be the ancestral area of the family, as well for the genera Chacophrys and Lepidobatrachus. In addition, temperature seasonality and annual precipitation play a major role in the niche differentiation of extant species within Ceratophryidae. In conclusion, our data suggest multiple dispersal and vicariance events originating from the Cerrado region in the early Miocene, and recognize the role of the environment in the differentiation of the ecological niches among extant species of this family in South America. Ceratophryidae is hypothesized to have originated in the semi-arid Cerrado region in the early Miocene (~19.2 million years ago), from where species have diversified by independent dispersal and vicariance events across other South American regions. Ceratophrys frogs are phylogenetically recovered as the sister taxon to the clade comprising Chacophrys and Lepidobatrachus. Three lineages of Lepidobatrachus and four lineages from Ceratophrys diverged in the Pliocene, around 5.3 to 2.6 million years ago. Niche differentiation among extant species of Ceratophryidae appears to reflect roles for temperature seasonality and annual precipitation.

Geographic genetic variation in the Coral Hawkfish, Cirrhitichthys oxycephalus (Cirrhitidae), in relation to biogeographic barriers across the Tropical Indo-Pacific

The Tropical Indo-Pacific (TIP) includes about two thirds of the world’s tropical oceans and harbors an enormous number of marine species. The distributions of those species within the region is affected by habitat discontinuities and oceanographic features. As well as many smaller ones, the TIP contains seven large recognized biogeographic barriers that separate the Red Sea and Indian Ocean, the Indian from the Pacific Ocean, the central and eastern Pacific, the Hawaiian archipelago, the Marquesas and Easter Islands. We examined the genetic structuring of populations of Cirrhitichthys oxycephalus, a small cryptic species of reef fish, across its geographic range, which spans the longitudinal limits of the TIP. We assessed geographic variation in the mitochondrial cytb gene and the nuclear RAG1 gene, using 166 samples collected in 46 localities from the western to eastern edges of the TIP. Sequences from cytb show three well-structured groups that are separated by large genetic distances (1.58–2.96%): two in the Tropical Eastern Pacific (TEP), one at Clipperton Atoll another occupying the rest of that region and the third that ranges across the remainder of the TIP, from the central Pacific to the Red Sea and South Africa. These results indicate that the ~4,000 km wide Eastern Pacific Barrier between the central and eastern Pacific is an efficient barrier separating the two main groups. Further, the ~950 km of open ocean that isolates Clipperton Atoll from the rest of the TEP is also an effective barrier. Contrary to many other cases, various major and minor barriers from the Central Indo-Pacific to the Red Sea are not effective against dispersal by C. oxycephalus, although this species has not colonized the Hawiian islands and Easter Island. The nuclear gene partially supports the genetic structure evident in cytb, although all haplotypes are geographically mixed.

Phylogeography and species distribution modeling unveil unnoticed Pliocene diversity: the case of a montane Iberian bush-cricket, Antaxius spinibrachius (Orthoptera: Tettigoniidae)

Abstract The geographic distribution and systematics of many groups of insects are still understudied across large geographic areas of the Iberian Peninsula. This lack of knowledge and the fact that many species have a complex evolutionary history due to the existence of “refugia within refugia” have hindered the taxonomic description of the true biodiversity in the Iberian Peninsula. Here, we discuss the evolutionary history of a flightless Iberian bush-cricket Antaxius spinibrachius (Fischer, 1853) using 1 nuclear and 2 mitochondrial markers. We applied species distribution modeling to design sampling strategies in climatically favorable areas and to detect missing isolated populations or unknown lineages. Following the species distribution modeled using all of the presence records available, we discovered 4 new isolated populations in Sierra Madrona, Serra de São Mamede, Sierra de Montánchez, and Sierra de la Demanda. Phylogenetic analyses recovered 2 major Pliocene lineages with a north–south geographic speciation pattern in the Iberian Peninsula. This north–south vicariant event split the common ancestor of these species on either side of the Tagus Valley, probably associated with the Pliocene climate change and the reorganization of paleobasins of the western Iberian Peninsula during the Miocene–Pliocene. We described the southern Iberian Plateau lineage of Antaxius as a new species of bush-cricket based on phylogenetic and morphological evidence, Antaxius oretanus sp. nov. We assessed the conservation status of the new species as “VU B2ab(iii,v)” under the IUCN criteria.

Ontogeny, not prey availability, underlies allopatric venom variability in insular and mainland populations of Vipera ammodytes

Allopatric populations living under distinct ecological conditions are excellent systems to infer factors underlying intraspecific venom variation. The venom composition of two populations of Vipera ammodytes, insular with a diet based on ectotherms and mainland with a diet based on ectotherms and endotherms, was compared considering the sex and age of individuals. Ten toxin families, dominated by PLA2, svMP, svSP, and DI, were identified through a bottom-up approach. The venom profiles of adult females and males were similar. Results from 58 individual SDS-PAGE profiles and venom pool analysis revealed significant differences between juveniles compared to subadults and adults. Two venom phenotypes were identified: a juvenile svMP-dominated and KUN-lacking phenotype and an adult PLA2/svMP-balanced and KUN-containing phenotype. Despite differences in prey availability (and, therefore, diet) between populations, no significant differences in venom composition were found. As the populations are geographically isolated, the lack of venom diversification could be explained by insufficient time for natural selection and/or genetic drift to act on the venom composition of island vipers. However, substantial differences in proteomes were observed when compared to venoms from geographically distant populations inhabiting different conditions. These findings highlight the need to consider ecological and evolutionary processes when studying venom variability. SignificanceThis study provides the first comprehensive analysis of the venom composition of two allopatric populations of Vipera ammodytes, living under similar abiotic (climate) but distinct biotic (prey availability) conditions. The ontogenetic changes in venom composition, coupled with the lack of differences between sex and between populations, shed light on the main determinants of venom evolution in this medically important snake. Seven new proteomes may facilitate future comparative studies of snake venom evolution. This study highlights the importance of considering ecological and evolutionary factors to understand snake venom variation.

A maritime location reduced palynofloral turnover and extirpation across the end Cretaceous boundary interval on the west coast of Canada

A well-preserved suite of ∼163 spore-pollen taxa from a recently discovered K/Pg interval within the maritime Oyster Bay Formation, Vancouver Island, British Columbia, Canada, reveals a pattern of floral turnover across the boundary event with local extirpations of ∼15 % of Cretaceous taxa. Along the margin of the eastern North Pacific, a shift occurred in near-coastal vegetation composition from uppermost Cretaceous diverse fern and bryophyte-dominated communities to Danian conifer-dominated forests with a fern understory. The ‘fern spore spike’ common in other K/Pg records was not detected within the sandstone to mudstone sequence. Spore-pollen assemblages preserved herein align with those of the Continental Margin floristic province. Palm pollen is noteworthy in the studied sections including Arecipites spp. (aff. Arecaceae), Spinizonocolpites spp. (aff. Nypa) and Pandaniidites typicus (aff. Pandanus) suggesting a warm, frost-free, sub-tropical climate prevailed across the K/Pg interval. The presence of numerous endemic spore-pollen taxa is indicative of geographic isolation from the North American Western Interior. Maritime climate buffering along the west coast of North America contributed to microrefugia permitting greater stability in terrestrial plant communities than in continental regions.

Cross-Disciplinary Rapid Scoping Review of Structural Racial and Caste Discrimination Associated with Population Health Disparities in the 21st Century

A cross-disciplinary rapid scoping review was carried out, generally following the PRISMA-SCR protocol to examine historical racial and caste-based discrimination as structural determinants of health disparities in the 21st century. We selected 48 peer-reviewed full-text articles available from the University of Memphis Libraries database search, focusing on three selected case-study countries: the United States (US), Canada, and Nepal. The authors read each article, extracted highlights, and tabulated the thematic contents on structural health disparities attributed to racism or casteism. The results link historical racism/casteism to health disparities occurring in Black and African American, Native American, and other ethnic groups in the US; in Indigenous peoples and other visible minorities in Canada; and in the Dalits of Nepal, a population racialized by caste, grounded on at least four foundational theories explaining structural determinants of health disparities. The evidence from the literature indicates that genetic variations and biological differences (e.g., disease prevalence) occur within and between races/castes for various reasons (e.g., random gene mutations, geographic isolation, and endogamy). However, historical races/castes as socio-cultural constructs have no inherently exclusive basis of biological differences. Disregarding genetic discrimination based on pseudo-scientific theories, genetic testing is a valuable scientific means to achieve the better health of the populations. Epigenetic changes (e.g., weathering—the early aging of racialized women) due to the DNA methylation of genes among racialized populations are markers of intergenerational trauma due to racial/caste discrimination. Likewise, chronic stresses resulting from intergenerational racial/caste discrimination cause an “allostatic load”, characterized by an imbalance of neuronal and hormonal dysfunction, leading to occurrences of chronic diseases (e.g., hypertension, diabetes, and mental health) at disproportionate rates among racialized populations. Major areas identified for reparative policy changes and interventions for eliminating the health impacts of racism/casteism include areas of issues on health disparity research, organizational structures, programs and processes, racial justice in population health, cultural trauma, equitable healthcare system, and genetic discrimination.

The role of mate competition in speciation and divergence: a systematic review.

Competition for mates can play a critical role in determining reproductive success, shaping phenotypic variation within populations, and influencing divergence. Yet, studies of the role of sexual selection in divergence and speciation have focused disproportionately on mate choice. Here, we synthesize the literature on how mate competition may contribute to speciation and integrate concepts from work on sexual selection within populations - mating systems, ecology, and mate choice. Using this synthesis, we generate testable predictions for how mate competition may contribute to divergence. Then, we identify the extent of existing support for these predictions in the literature with a systematic review of the consequences of mate competition for population divergence across a range of evolutionary, ecological, and geographic contexts. We broadly evaluate current evidence, identify gaps in available data and hypotheses that need testing, and outline promising directions for future work. A major finding is that mate competition may commonly facilitate further divergence after initial divergence has occurred, e.g., upon secondary contact and between allopatric populations. Importantly, current hypotheses for how mate competition contributes to divergence do not fully explain observed patterns. While results from many studies fit predictions of negative frequency dependent selection, agonistic character displacement, and ecological selection, results from ~30% studies did not fit existing conceptual models. This review identifies future research aims for scenarios in which mate competition is likely important but has been understudied, including how ecological context and interactions between mate choice and mate competition can facilitate or hinder divergence and speciation.

HIV/AIDS in Papua New Guinea: A Comprehensive Review

This comprehensive review examines the HIV/AIDS epidemic in Papua New Guinea (PNG), a country characterized by its unique cultural and geographical context. Although the global HIV/AIDS crisis began in the early 1980s, PNG’s first case was not recorded until 1987. Since then, the epidemic has significantly impacted the nation, evolving into a critical public health challenge. This review explores the historical context, epidemiology, socioeconomic impacts, and public health responses to HIV/AIDS in PNG. The epidemiological analysis highlights the generalized nature of the epidemic in PNG, with heterosexual transmission being the predominant mode. Key populations, such as sex workers and men who have sex with men (MSM), are disproportionately affected due to social stigma, discrimination, and limited access to healthcare. Regional disparities in prevalence are also notable, with urban areas and certain provinces, particularly in the Highlands region, experiencing higher burdens of the disease. The socioeconomic impacts of HIV/AIDS in PNG are profound, straining the already limited healthcare infrastructure and exacerbating poverty, especially in rural areas. The review discusses how cultural factors, including traditional beliefs, polygamy, and the practice of bride price, contribute to the spread of HIV and hinder public health interventions. Stigma and discrimination further complicate efforts to manage the epidemic, often deterring individuals from seeking testing and treatment. Public health responses in PNG have included preventive campaigns, expanded testing and counseling services, and the introduction of Antiretroviral Therapy (ART) programs. Community-based approaches, such as peer education and support groups, have also played a crucial role in combating the epidemic. Despite these efforts, challenges remain, including geographic isolation, cultural barriers, and limited resources. The review concludes with future directions and recommendations for strengthening PNG’s healthcare infrastructure, addressing stigma and discrimination, enhancing prevention strategies, and investing in research and surveillance. These measures are essential for controlling the HIV/AIDS epidemic and improving the overall health and well-being of the population in Papua New Guinea. Keywords: HIV/AIDS, Papua New Guinea, epidemiology, public health, Antiretroviral Therapy (ART).

Machine learning in geography education: Evaluating student performance in rural china

The disparity in the development and application of educational resources between urban and rural areas is pronounced, with rural students often encountering significant challenges in acquiring geographic knowledge and developing spatial cognitive skills due to their geographical isolation and limited access to educational resources. This study aims to investigate the effectiveness of geography education resource development in rural areas by examining the influence of various educational resource characteristics on students' scores in geography education. Through the application of data analysis and machine learning predictive methods, this research explores the impact of 13 variables, including gender, age, parental education level, family background, internet accessibility, outdoor practical activities, and family outdoor travel frequency. These factors were modeled and assessed using a range of machine learning algorithms. The findings reveal differential impacts of these characteristics on students' scores in geography education, with models such as Random Forest and XGBoost demonstrating superior performance in predicting scores in geography courses. This research provides empirical data and a scientific framework to support the optimization of geography education resources in rural areas, offering theoretical and practical insights for advancing educational equity and fostering local socioeconomic development.

Influence of geographic isolation and the environment on gene flow among phenotypically diverse lizards.

Lizards in the genus Anolis comprise hundreds of species that display a wide range of phenotypic variation closely related to their environment. One example is the Guadeloupean anole (Anolis marmoratus ssp.) that display extreme phenotypic variation, primarily in adult male color and pattern, with twelve described subspecies on the archipelago. Here we examine the relationship between phenotypic and genetic divergence among five subspecies on the two main islands and test the role of geographic isolation and the environment in reducing gene flow. We also examined two offshore island populations to assess the impact of complete geographic isolation on gene flow. We analyzed color phenotypes by measuring spectral reflectance and genomic diversity using SNPs. Genetic divergence was correlated with dorsolateral head and body color phenotypes, and slope and geographic distance were nearly equivalent at explaining this divergence. There was minimal genome-wide divergence at neutral loci among phenotypically disparate subspecies on the two main islands and their differentiation is consistent with a model of divergence with gene flow. Our spatial visualization of gene flow showed an impact of environmental features consistent with a hypothesis of ecologically driven divergence. Nonetheless, subspecies on the two main islands remain interconnected by substantial gene flow and their phenotypic variation is likely maintained at selection-gene flow equilibrium by divergent selection at loci associated with their color phenotypes. Greater isolation, such as inhabiting a remote island, may be required for reducing gene flow. Our findings highlight the role of the environment, adaptation, and geographic isolation on gene flow.

Plant species diversification in the Himalaya-Hengduan Mountains region: an example from an endemic lineage of Pedicularis (Orobanchaceae) in the role of floral specializations and rapid range expansions.

The c. 270 endemic species of Pedicularis in the Himalaya-Hengduan Mountains (HHM) region exhibit high diversity in geographic distribution, elevational range and floral morphology. Many of these, including the species with the longest corolla tubes and beaked galeas, are monophyletic and represent a putative in situ radiation. In this study, we focus on the representative Clade 3 within the HHM region. We integrate the plastid phylogeny of this clade with environmental data and species distributions to infer environmental correlates of species diversity. We estimate macroevolutionary rates and reconstructed ancestral states for geographic ranges and corolla traits, and analyse patterns of range overlap and niche evolution to assess drivers of diversification in the HHM region. Our results show that the region from northwest Yunnan to southwest Sichuan is the centre of diversity for this clade of Pedicularis. Rates of diversification are associated with precipitation and multiple environmental factors. Multiple range expansions from the Sanjiang (Three Parallel Rivers) region, followed by allopatric speciation across the HHM region, contributed to early rapid diversification. Corolla traits are not significantly associated with species diversification. This study highlights the importance of integrated evidence for understanding species diversification dynamics and contributes to our understanding of the origins of the remarkable richness of plant species in the HHM region.

A sex chromosome polymorphism maintains divergent plumage phenotypes between extensively hybridizing yellowhammers (Emberiza citrinella) and pine buntings (E. leucocephalos).

Under allopatric speciation, populations of a species become isolated by a geographic barrier and develop reproductive isolation through genetic differentiation. When populations meet in secondary contact, the strength of evolved reproductive barriers determines the extent of hybridization and whether the populations will continue to diverge or merge together. The yellowhammer (Emberiza citrinella) and pine bunting (E. leucocephalos) are avian sister species that diverged in allopatry on either side of Eurasia during the Pleistocene glaciations. Though they differ greatly in plumage and form distinct genetic clusters in allopatry, these taxa show negligible mitochondrial DNA differentiation and hybridize extensively where they overlap in central Siberia, lending uncertainty to the state of reproductive isolation in the system. To assess the strength of reproductive barriers between taxa, we examined genomic differentiation across the system. We found that extensive admixture has occurred in sympatry, indicating that reproductive barriers between taxa are weak. We also identified a putative Z chromosome inversion region that underlies plumage variation in the system, with the 'pine bunting' haplotype showing dominance over the 'yellowhammer' haplotype. Our results suggest that yellowhammers and pine buntings are currently at a crossroads and that evolutionary forces may push this system towards either continued differentiation or population merging. However, even if these taxa merge, recombination suppression between putative chromosome Z inversion haplotypes may maintain divergent plumage phenotypes within the system. In this way, our findings highlight the important role hybridization plays in increasing the genetic and phenotypic variation as well as the evolvability of a system.