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The genetic identity and conservation status of lake ecotype of brown trout (Salmo trutta) populations in Slovenia's Alpine lakes Bled and Bohinj have been subjected to changes due to historical stocking practices. We aimed to evaluate the genetic differentiation and origins of these populations to advise for correct conservation strategies. Using microsatellite and mitochondrial DNA analysis on 365 trout specimens, we explored the genetic diversity and structure of these populations, comparing them with potential originators. Results revealed distinct genetic profiles between Bled and Bohinj lake trout, with Bohinj lake trout closely aligned with the native Danubian lineage and Bled lake trout showing a hybrid composition, significantly influenced by hatchery-introduced Atlantic lineage strains. The genetic distinction between these populations underscores the complexity of their conservation, showcasing the impact of human-mediated introductions on natural populations. The urgent need for conservation measures to preserve the Bohinj population's native genetic pool is highlighted, underlining the must to prevent the transfer of individuals from Lake Bled or elsewhere and to reconsider stocking practises in order to prevent further genetic dilution of these iconic European lake dwellers. [ABSTRACT FROM AUTHOR]

Improving the understanding of the causes and effects of anthropogenic hybridization is fundamental to ensure species conservation, particularly in the case of hybridization between wild species and their domestic relatives. Knowledge is missing for many species also because of a lack of appropriate tools for hybrid identification. Here, coupling genotype and phenotype analysis, we carried out an extensive investigation of ongoing hybridization in Alpine ibex Capra ibex, a mountain ungulate of conservation concern from a genetic perspective. By genotyping 63 diagnostic and 465 neutral SNPs, 20 suspected hybrids and 126 Alpine ibex without suspicious phenotype, representing 8 populations across a major part of the species distribution, we found evidence for ongoing hybridization between Alpine ibex and domestic goat. We identified different levels of hybridization including backcrosses into both Alpine ibex and domestic goat. Our results suggest a lack of reproductive barriers between the two species and good survival and reproductive success of the hybrids. Hybridization was locally intense, like a hybrid swarm, but not spread across the rest of the species distribution. Most of the hybrids were discovered in two locations in the north‐west of Italy, while random sampling of individuals from different areas did not provide evidence of recent hybridization. Our method, based on amplicon sequencing of 63 diagnostic SNPs specifically developed for this purpose, allowed us to identify hybrids and backcrosses up to the fourth to fifth generations and was suitable for genetic samples of different quality, although with varying levels of certainty regarding the exact number of generations passed since hybridization. Based on the paired analysis of genotype and phenotype, we provide guidelines for the first identification of hybrids in the field and suggest a procedure for the reliable identification of hybrids. [ABSTRACT FROM AUTHOR]

Summary: Hybrid zones provide natural experimental settings to test hypotheses about species divergence. We concentrated on a hybrid swarm in which oil‐collecting bees and flower‐pecking birds act as pollinators of two Calceolaria species. We asked whether both pollinators contributed to flower divergence by differentially promoting prezygotic fitness at the phenotypic extremes that represent parentals.We studied pollinator‐mediated selection on phenotypic traits critical in plant–pollinator mechanical interaction, namely plant height, reward‐to‐stigma distance, and flower shape. We utilised the quantity and quality of pollen deposited as fitness measures and distinguished between the contribution of the two pollinator types.Results showed uni‐ and bivariate disruptive selection for most traits through pollen grains deposited by both pollinators. Bird‐mediated fitness favoured low plants with a long reward‐to‐stigma distance and a straight corolla, while bee‐mediated fitness favoured tall plants with a short reward‐to‐stigma distance and curved corolla. In addition, stabilising selection at one end of the phenotypic range showed a bird‐mediated reproductive asymmetry within the swarm. The disruptive pattern was countered, albeit weakly, by hybrids receiving higher‐quality pollen on the stigmas.Results suggest that pollinator‐mediated selection promotes divergence of integrated flower phenotypes mechanically adjusted either to bees or birds underscoring the importance of pollinator specialisation in diversification. [ABSTRACT FROM AUTHOR]

In this work, we analyzed the morphology and genetic structure of Teucrium montanum, T. capitatum and their hybrid T. × rohlenae from three syntopic populations. A morphometric study showed that the parents and their hybrids exhibited continuous morphological variation, with the hybrid positioned exactly between the parents. Genetic analysis revealed that plants morphologically identified as T. × rohlenae are fertile hybrids that produce hybrid swarms dominated by later-generation hybrids. This suggests that introgression, rather than speciation, is the more likely outcome of hybridization between these plant species. The extent and direction of gene flow between the two species differed markedly between the three syntopic localities. At the Trilj locality, it was clearly unidirectional, with T. capitatum playing the dominant role. At the Sićevo locality, gene flow was slightly asymmetric, favoring the genetic background of T. capitatum, while at the Sliven site, it was completely asymmetric in the opposite direction. The extreme case of unidirectional gene flow was observed at the Trilj locality where plants morphologically identified as T. montanum could not be genetically distinguished from T. capitatum. This suggests that interspecific hybridization occurred long ago, leading to introgression and cryptic hybrids, blurring of species boundaries and generating evolutionary noise. [ABSTRACT FROM AUTHOR]

Abstract Improving the understanding of the causes and effects of anthropogenic hybridization is fundamental to ensure species conservation, particularly in the case of hybridization between wild species and their domestic relatives. Knowledge is missing for many species also because of a lack of appropriate tools for hybrid identification. Here, coupling genotype and phenotype analysis, we carried out an extensive investigation of ongoing hybridization in Alpine ibex Capra ibex, a mountain ungulate of conservation concern from a genetic perspective. By genotyping 63 diagnostic and 465 neutral SNPs, 20 suspected hybrids and 126 Alpine ibex without suspicious phenotype, representing 8 populations across a major part of the species distribution, we found evidence for ongoing hybridization between Alpine ibex and domestic goat. We identified different levels of hybridization including backcrosses into both Alpine ibex and domestic goat. Our results suggest a lack of reproductive barriers between the two species and good survival and reproductive success of the hybrids. Hybridization was locally intense, like a hybrid swarm, but not spread across the rest of the species distribution. Most of the hybrids were discovered in two locations in the north‐west of Italy, while random sampling of individuals from different areas did not provide evidence of recent hybridization. Our method, based on amplicon sequencing of 63 diagnostic SNPs specifically developed for this purpose, allowed us to identify hybrids and backcrosses up to the fourth to fifth generations and was suitable for genetic samples of different quality, although with varying levels of certainty regarding the exact number of generations passed since hybridization. Based on the paired analysis of genotype and phenotype, we provide guidelines for the first identification of hybrids in the field and suggest a procedure for the reliable identification of hybrids.

Introgressive hybridization may erode phenotypic divergence along environmental gradients, collapsing locally adapted populations into a hybrid swarm. Alternatively, introgression may promote phenotypic divergence by providing variation on which natural selection can act. In freshwater fishes, water flow often selects for divergent morphological traits in lake versus stream habitats. We tested the effects of introgression on lake-stream morphological divergence in the minnow Owens Tui Chub (Siphateles bicolor snyderi), which has been rendered endangered by introgession from the introduced Lahontan Tui Chub (Siphateles bicolor obesa). Using geometric morphometric analysis of 457 individual Tui Chub from thirteen populations, we found that both native and introgressing parent taxa exhibited divergent body and caudal fin shapes in lake versus stream habitats, but their trajectories of divergence were distinct. In contrast, introgressed populations exhibited intermediate body and caudal fin shapes that were not differentiated by habitat type, indicating that introgression has eroded phenotypic divergence along the lentic-lotic gradient throughout the historic range of the Owens Tui Chub. Individuals within hybrid populations were less morphologically variable than those within parent populations, suggesting hybrid adaptation to selective agents other than water flow or loss of variance by drift.

In this work, we analyzed the morphology and genetic structure of Teucrium montanum, T. capitatum and their hybrid T. × rohlenae from three syntopic populations. A morphometric study showed that the parents and their hybrids exhibited continuous morphological variation, with the hybrid positioned exactly between the parents. Genetic analysis revealed that plants morphologically identified as T. × rohlenae are fertile hybrids that produce hybrid swarms dominated by later-generation hybrids. This suggests that introgression, rather than speciation, is the more likely outcome of hybridization between these plant species. The extent and direction of gene flow between the two species differed markedly between the three syntopic localities. At the Trilj locality, it was clearly unidirectional, with T. capitatum playing the dominant role. At the Sićevo locality, gene flow was slightly asymmetric, favoring the genetic background of T. capitatum, while at the Sliven site, it was completely asymmetric in the opposite direction. The extreme case of unidirectional gene flow was observed at the Trilj locality where plants morphologically identified as T. montanum could not be genetically distinguished from T. capitatum. This suggests that interspecific hybridization occurred long ago, leading to introgression and cryptic hybrids, blurring of species boundaries and generating evolutionary noise.

We studied hybridization between the Black-crested and Tufted titmouse across two geographically distinct transects that differ in the timing of secondary contact by hundreds to thousands of years. We found that hybridization patterns correspond to localized hybrid swarms and that the titmouse hybrid zone is likely slowly expanding over time, a product of short post-natal dispersal distances coupled with weak or absent selection against admixture. We show the southern part of the hybrid zone located in Texas is four times wider than the northern region of hybridization in Oklahoma, which is likely due to geographic differences in hybrid zone age. Despite differences in width, most individuals in both transects are advanced-generation hybrids and backcrosses, suggesting geographically consistent hybridization dynamics. We documented a strong correlation between genotypes and plumage index, suggesting that hybridization has not yet resulted in the decoupling of plumage and genome-wide ancestry as observed in some other avian hybrid zones. Although our results suggest the ongoing expansion of the hybrid zone, the rate of expansion appears to be slow, on the scale of tens of meters a year, and it will likely take hundreds of thousands to millions of years before homogenization of the parental populations. While we did not find support for partial reproductive isolation in the hybrid zone itself, there is the possibility that ecological or sexual selection limits introgression into allopatric regions. Broadly, the results of our study highlight the value of multiple, geographically distant, transects across a hybrid zone for assessing the evolutionary dynamics of hybridizing lineages. [ABSTRACT FROM AUTHOR]

Native to North America, largemouth bass Micropterus salmoides (Lacepède, 1802) were introduced in South Africa in 1928. Florida bass Micropterus floridanus (Lesueur, 1822) were introduced to enhance existing largemouth bass fisheries in 1980. While largemouth bass and Florida bass readily hybridise and produce offspring that are difficult to identify morphologically, confirmation of hybridisation requires genetic analysis. This study sought to understand: (1) the extent to which Florida bass spread within a catchment once introduced; and (2) whether a subset of samples taken from within a catchment accurately characterises hybridisation throughout the catchment. Samples were collected from the Breede River and Kowie River catchments and screened using 38 species-diagnostic single nucleotide polymorphisms to assess hybridisation. Collections from the mainstem of both rivers represented hybrid swarms, and neither pure largemouth bass nor Florida bass were observed. The absence of genetic differentiation among sampling sites suggests that hybridisation will occur throughout systems where both species are present. Hybridisation levels in dams located off the mainstem rivers were significantly variable and represented potential sources for Florida bass alleles observed within rivers. This finding, in conjunction with our limited knowledge of the distributions of the two species, suggests that applying independent management strategies to control and monitor the spread of both species may prove difficult. [ABSTRACT FROM AUTHOR]

Abstract Introgressive hybridization may erode phenotypic divergence along environmental gradients, collapsing locally adapted populations into a hybrid swarm. Alternatively, introgression may promote phenotypic divergence by providing variation on which natural selection can act. In freshwater fishes, water flow often selects for divergent morphological traits in lake versus stream habitats. We tested the effects of introgression on lake–stream morphological divergence in the minnow Owens Tui Chub (Siphateles bicolor snyderi), which has been rendered endangered by introgession from the introduced Lahontan Tui Chub (Siphateles bicolor obesa). Using geometric morphometric analysis of 457 individual Tui Chub from thirteen populations, we found that both native and introgressing parent taxa exhibited divergent body and caudal fin shapes in lake versus stream habitats, but their trajectories of divergence were distinct. In contrast, introgressed populations exhibited intermediate body and caudal fin shapes that were not differentiated by habitat type, indicating that introgression has eroded phenotypic divergence along the lentic–lotic gradient throughout the historic range of the Owens Tui Chub. Individuals within hybrid populations were less morphologically variable than those within parent populations, suggesting hybrid adaptation to selective agents other than water flow or loss of variance by drift.

Hybridization is an evolutionary process with wide‐ranging potential outcomes, from providing populations with important genetic variation for adaptation to being a substantial fitness cost leading to extinction. Here, we focussed on putative hybridization between two morphologically distinct species of New Zealand grasshopper. We collected Phaulacridium marginale and Phaulacridium otagoense specimens from a region where mitochondrial introgression had been detected and where their habitat has been modified by introduced mammals eating the natural vegetation and by the colonization of many non‐native plant species. In contrast to observations in the 1970s, our sampling of wild pairs of grasshoppers in copula provided no evidence of assortative mating with respect to species. Geometric morphometrics on pronotum shape of individuals from areas of sympatry detected phenotypically intermediate specimens (putative hybrids), and the distribution of phenotypes in most areas of sympatry was found to be unimodal. These results suggest that hybridization associated with anthropogenic habitat changes has led to these closely related species forming a hybrid swarm, with random mating. Without evidence of hybrid disadvantage, we suggest a novel hybrid lineage might eventually result from the merging of these two species. [ABSTRACT FROM AUTHOR]

Background and Aims Hybridization is increasingly recognized as an integral part of the dynamics of species range expansion and contraction. Thus, it is important to understand the reproductive barriers between co-occurring species. Extending previous studies that argued that the rare Eucalyptus risdonii was expanding into the range of the surrounding E. amygdalina by both seed and pollen dispersal, we here investigate the long-term fitness of both species and their hybrids and whether expansion is continuing. Methods We assessed the survival of phenotypes representing a continuum between the two pure species in a natural hybrid swarm after 29 years, along with seedling recruitment. The performance of pure species as well as of artificial and natural hybrids was also assessed over 28 years in a common garden trial. Key Results In the hybrid zone, E. amygdalina adults showed greater mortality than E. risdonii , and the current seedling cohort is still dominated by E. risdonii phenotypes. Morphologically intermediate individuals appeared to be the least fit. Similar results were observed after growing artificial first-generation and natural hybrids alongside pure species families in a common garden trial. Here, the survival, reproduction, health and growth of the intermediate hybrids were significantly less than those of either pure species, consistent with hybrid inferiority, although this did not manifest until later reproductive ages. Among the variable progeny of natural intermediate hybrids, the most E. risdonii -like phenotypes were the most fit. Conclusions This study contributes to the increasing number of reports of hybrid inferiority in Eucalyptus , suggesting that post-zygotic barriers contribute to the maintenance of species integrity even between closely related species. However, with fitness rapidly recovered following backcrossing, it is argued that hybridization can still be an important evolutionary process, in the present case appearing to contribute to the range expansion of the rare E. risdonii in response to climate change. [ABSTRACT FROM AUTHOR]

Introgressive hybridization may erode phenotypic divergence along environmental gradients, collapsing locally adapted populations into a hybrid swarm. Alternatively, introgression may promote phenotypic divergence by providing variation on which natural selection can act. In freshwater fishes, water flow often selects for divergent morphological traits in lake versus stream habitats. We tested the effects of introgression on lake–stream morphological divergence in the minnow Owens Tui Chub (Siphateles bicolor snyderi), which has been rendered endangered by introgession from the introduced Lahontan Tui Chub (Siphateles bicolor obesa). Using geometric morphometric analysis of 457 individual Tui Chub from thirteen populations, we found that both native and introgressing parent taxa exhibited divergent body and caudal fin shapes in lake versus stream habitats, but their trajectories of divergence were distinct. In contrast, introgressed populations exhibited intermediate body and caudal fin shapes that were not differentiated by habitat type, indicating that introgression has eroded phenotypic divergence along the lentic–lotic gradient throughout the historic range of the Owens Tui Chub. Individuals within hybrid populations were less morphologically variable than those within parent populations, suggesting hybrid adaptation to selective agents other than water flow or loss of variance by drift. [ABSTRACT FROM AUTHOR]

Baltic blue mussels can colonise and dominate habitats with far lower salinity (

The Eurasian Rhamnus cathartica is widespread, common, and naturalized in parts of the northeastern United States. Other nonnative buckthorn species are also present but underreported because intraspecific leaf polymorphisms, hybridization, and imprecise literature descriptions confuse identifications. A study of Rhamnus populations in Tompkins and Onondaga counties in New York and Hartford County in Connecticut provided an opportunity to revisit the literature and to propose identification aids based on infrequently reported fruit stone number and mature fruit pulp color. These characters facilitate inferences of ancestry of apparent hybrids involving R. cathartica, R. davurica, and R. utilis. [ABSTRACT FROM AUTHOR]

Premise of research. Hybridization is a mechanism frequently invoked to account for the spectacular radiations observed in oceanic islands, but, surprisingly, there is little empirical support for its ecological role in island plant radiations. Theory predicts that hybridization should provide individuals with the phenotypic novelty required for habitat shifts, thus promoting conditions for subsequent speciation. In this article, we studied the first stages of this process using two hybridizing species of Dubautia (Asteraceae), the most diversified genus of the Hawaiian silversword radiation. Methodology. Phenotypic and habitat differentiation were investigated in two recently derived species (Dubautia arborea and Dubautia ciliolata) and a hybrid zone. Morphological trait expression and physiological trait expression under field and common garden conditions and microclimatic variation were analyzed to address the patterns of differentiation among parental species and hybrids. Pivotal results. Our analyses showed that parental species occupied contrasting habitats and represented the extremes of phenotypic variation. Conversely, hybrids displayed novel phenotypes outside parental ranges, generating a continuum of intermediate phenotypes in the study system. We also found a strong relationship between morphological and physiological variation and plant performance, which suggests that broad phenotypic variation in hybrids could be favored by the environmental heterogeneity of the hybrid zone. Conclusions. The initial expectations for the ecological role of hybridization in adaptive radiations are confirmed in this Dubautia system, in which hybrids of closely related species display novel morphological and physiological variation associated with the colonization of a new habitat. To understand the evolutionary processes creating an unusual degree of variation within particular lineages, molecular studies revealing cases of hybridization in island radiations should be complemented with ecological studies. © 2013 by The University of Chicago. All rights reserved.

Premise of research. Hybridization is a mechanism frequently invoked to account for the spectacular radiations observed in oceanic islands, but, surprisingly, there is little empirical support for its ecological role in island plant radiations. Theory predicts that hybridization should provide individuals with the phenotypic novelty required for habitat shifts, thus promoting conditions for subsequent speciation. In this article, we studied the first stages of this process using two hybridizing species of Dubautia (Asteraceae), the most diversified genus of the Hawaiian silversword radiation. Methodology. Phenotypic and habitat differentiation were investigated in two recently derived species (Dubautia arborea and Dubautia ciliolata) and a hybrid zone. Morphological trait expression and physiological trait expression under field and common garden conditions and microclimatic variation were analyzed to address the patterns of differentiation among parental species and hybrids. Pivotal results. Our analyses showed that parental species occupied contrasting habitats and represented the extremes of phenotypic variation. Conversely, hybrids displayed novel phenotypes outside parental ranges, generating a continuum of intermediate phenotypes in the study system. We also found a strong relationship between morphological and physiological variation and plant performance, which suggests that broad phenotypic variation in hybrids could be favored by the environmental heterogeneity of the hybrid zone. Conclusions. The initial expectations for the ecological role of hybridization in adaptive radiations are confirmed in this Dubautia system, in which hybrids of closely related species display novel morphological and physiological variation associated with the colonization of a new habitat. To understand the evolutionary processes creating an unusual degree of variation within particular lineages, molecular studies revealing cases of hybridization in island radiations should be complemented with ecological studies. © 2013 by The University of Chicago. All rights reserved.

The adaptive radiation of cichlid fishes in East African Lake Malawi encompasses over 500 species that are believed to have evolved within the last 800,000 years from a common founder population. It has been proposed that hybridization between ancestral lineages can provide the genetic raw material to fuel such exceptionally high diversification rates, and evidence for this has recently been presented for the Lake Victoria region cichlid superflock. Here, we report that Lake Malawi cichlid genomes also show evidence of hybridization between two lineages that split 3–4 Ma, today represented by Lake Victoria cichlids and the riverine Astatotilapia sp. "ruaha blue." The two ancestries in Malawi cichlid genomes are present in large blocks of several kilobases, but there is little variation in this pattern between Malawi cichlid species, suggesting that the large-scale mosaic structure of the genomes was largely established prior to the radiation. Nevertheless, tens of thousands of polymorphic variants apparently derived from the hybridization are interspersed in the genomes. These loci show a striking excess of differentiation across ecological subgroups in the Lake Malawi cichlid assemblage, and parental alleles sort differentially into benthic and pelagic Malawi cichlid lineages, consistent with strong differential selection on these loci during species divergence. Furthermore, these loci are enriched for genes involved in immune response and vision, including opsin genes previously identified as important for speciation. Our results reinforce the role of ancestral hybridization in explosive diversification by demonstrating its significance in one of the largest recent vertebrate adaptive radiations. [ABSTRACT FROM AUTHOR]

Most species and therefore most hybrid zones have historically been defined using phenotypic characters. However, both speciation and hybridization can occur with negligible morphological differentiation. Recently developed genomic tools provide the means to better understand cryptic speciation and hybridization. The Northwestern Crow (Corvus caurinus) and American Crow (Corvus brachyrhynchos) are continuously distributed sister taxa that lack reliable traditional characters for identification. In this first population genomic study of Northwestern and American crows, we use genomic SNPs (nuDNA) and mtDNA to investigate the degree of genetic differentiation between these crows and the extent to which they may hybridize. Our results indicate that American and Northwestern crows have distinct evolutionary histories, supported by two nuDNA ancestry clusters and two 1.1%‐divergent mtDNA clades dating to the late Pleistocene, when glacial advances may have isolated crow populations in separate refugia. We document extensive hybridization, with geographic overlap of mtDNA clades and admixture of nuDNA across >900 km of western Washington and western British Columbia. This broad hybrid zone consists of late‐generation hybrids and backcrosses, but not recent (e.g., F1) hybrids. Nuclear DNA and mtDNA clines had concordant widths and were both centred in southwestern British Columbia, farther north than previously postulated. Overall, our results suggest a history of reticulate evolution in American and Northwestern crows, perhaps due to recurring neutral expansion(s) from Pleistocene glacial refugia followed by lineage fusion(s). However, we do not rule out a contributing role for more recent potential drivers of hybridization, such as expansion into human‐modified habitats. [ABSTRACT FROM AUTHOR]

The complex taxonomy and biogeography of the highly polytypic and widespread gentle monkey Cercopithecus mitis continue to be debated. Tanzania and Kenya, together, support eight of the currently recognized 17 subspecies of C. mitis. This paper reviews the taxonomy of the eight subspecies of C. mitis recognized for Kenya and Tanzania and presents an overview of their geographic distribution and pelage coloration and pattern. This paper also describes a new, endemic, subspecies of C. mitis for Tanzania, offers two hypotheses for its origin and phylogenetic affinities, and assesses its conservation status and conservation needs. Cercopithecus mitis in the Lake Manyara-Ngorongoro Region of central north Tanzania (i.e., the "Manyara Population") has often been referred to as "C. m. stuhlmanni x C. m. albogularis hybrids" and as representative of a "hybrid swarm." To better understand the taxonomic and conservation status of this population, four field surveys totaling 25 days were undertaken in southwest Kenya and central north Tanzania. The aim was to determine the geographic distribution of this population and to obtain detailed descriptions and photographs of as many individuals as possible. In addition, the literature was searched, and 88 C. mitis specimen skins were directly examined at four museums. We found no evidence to support the contention that C. mitis of the Lake Manyara-Ngorongoro Region are hybrids or represent a hybrid swarm. The Manyara C. mitis is geographically isolated from other C. mitis by >90 km of semi-arid habitat, is phenotypically distinct from other C. mitis, and presents little intrapopulation variation. As such, the diagnosable phenotypic characters of this population appear to be fixed, genetic, and heritable. In this paper we describe a new subspecies of C. mitis, the "Manyara monkey." The holotype, an adult female skin at the Natural History Museum, London, was collected by B. Cooper in 1937 at the north end of Lake Manyara. Two paratopotypes are also designated. This Cercopithecus mitis ssp. nov. is endemic to central north Tanzania. The known geographic distribution extends from the Ngorongoro Conservation Area southwards through Lake Manyara National Park to the Nou Catchment Forest Reserve and Ufiome Forest Reserve. The known geographic distribution is c. 1,480 km², while the probable geographic distribution is c. 5,865 km². This monkey occupies various types of forest from 960 m asl to at least 2,550 m asl, while the probable upper limit is c. 3,260 m asl. Mean annual rainfall across the known and probable geographic distribution ranges from c. 500 mm to c. 1,200 mm. Cercopithecus mitis ssp. nov. appears to represent a relic population. We put forth two hypotheses for its origin. Hypothesis I: It represents a now isolated section of a phenotypic cline that once extended across the Eastern Rift Valley. Hypothesis II: It is a close relative of C. m. opisthostictus and, thereby, is a relic of dispersal from the Congo Basin/Upper Zambezi Basin to the Lake Manyara-Ngorongoro Region. Additional biogeographical research and, particularly, deep molecular research are required to further our understanding of the taxonomy and evolutionary history of C. mitis. Although c. 60% (c. 3,500 km²) of the probable geographic distribution of this C. mitis ssp. nov. lies within six protected areas, the future of this monkey is uncertain due to threats associated with the region's rapidly increasing human population, particularly the degradation, loss, and fragmentation of forest. When assessed in 2016 as C. mitis ssp. nov. for the IUCN Red List of Threatened Species, the threat category designated was Endangered. Conservation priorities for this new subspecies include the effective management of the six protected areas in which it occurs and the restoration and protection of the wildlife corridors of the Lake Manyara-Ngorongoro Region. [ABSTRACT FROM AUTHOR]

Three Diorhabda spp. tamarisk beetles (Coleoptera: Chrysomelidae) were established in Texas from 2003 to 2010 for biological control of tamarisk (Tamarix spp.): Mediterranean tamarisk beetles, D. elongata (Brullé) from Greece, also established in New Mexico; subtropical tamarisk beetles, D. sublineata (Lucas) from Tunisia; and larger tamarisk beetles, D. carinata (Faldermann) from Uzbekistan. More than one million tamarisk beetles were released at 99 sites. Species establishment success ranged from 52 to 83%. All three species now co-occur in New Mexico with the northern tamarisk beetles, D. carinulata (Desbrochers). A phenotypic hybrid scoring system was developed to assess Diorhabda phenotype distributions and character mixing in hybrid zones. Widespread field populations of bispecific hybrid phenotypes for D. carinata/D. elongata and D. sublineata/D. elongata rapidly appeared following contact of parental species. Initial distributions and dispersal of Diorhabda spp. and hybrids are mapped for Texas, New Mexico, Oklahoma, and Kansas, where they produced large-scale tamarisk defoliation and localized dieback for 3–4 yr. However, populations subsequently severely declined, now producing only isolated defoliation and allowing tamarisk to recover. Diorhabda sublineata and D. elongata temporarily produced nontarget spillover defoliation of ornamental athel, Tamarix aphylla (L.) Karst, along the Rio Grande. Hybrid phenotypes were generally bimodally distributed, indicating some degree of reproductive isolation. Additional diagnostic phenotypic characters in males allowed more precise hybrid scoring. Character mixing in some hybrid populations approached or reached that of a hybrid swarm. The significance of hybridization for tamarisk biocontrol is discussed. [ABSTRACT FROM AUTHOR]

Abstract: In the Ryukyu Archipelago, Japan, Goniurosaurus geckos are currently divided into six allopatric taxa among nearby islands. Recent studies suggested the occurrence of large genetic divergence within a single island and the possible non‐monophyly of a few taxa, but their species delimitation is not well resolved. We investigated the taxonomic relationships between the possibly geographically overlapped, highly diverged entities as well as other island populations via dense sampling. Our mitochondrial and nuclear DNA analyses showed that the two genetic groups were distributed in parapatry within Okinawajima Island and that they were hybridizing in narrow area around the contact zone. Geohistorical evidence suggests that the restricted gene flow has been caused by some intrinsic isolation mechanisms. Thus, we conclude that the two lineages represent full species. Mitochondrial analysis also showed that the genetic differences among other island populations were comparable to those between these species, thereby suggesting the presence of seven full species, including one unnamed taxon. We also discuss the possible cause of this divergence and why it has occurred at such a fine geographic scale. [ABSTRACT FROM AUTHOR]

Hybrid populations and introgressive hybridization remain poorly documented in pathogenic micro-organisms, as such that genetic exchange has been argued to play a minor role in their evolution. Recent work demonstrated the existence of hybrid microsatellite profiles in Trypanosoma congolense, a parasitic protozoan with detrimental effects on livestock productivity in sub-Saharan Africa. Here, we present the first population genomic study of T. congolense, revealing a remarkable number of single nucleotide polymorphisms ( SNPs), small insertions/deletions (indels) and gene deletions among 56 parasite genomes from ten African countries. One group of parasites from Zambia was particularly diverse, displaying a substantial number of heterozygous SNP and indel sites compared to T. congolense parasites from the nine other sub-Saharan countries. Genomewide 5-kb phylogenetic analyses based on phased SNP data revealed that these parasites were the product of hybridization between phylogenetically distinct T. congolense lineages. Other parasites within the same region in Zambia presented a mosaic of haplotypic ancestry and genetic variability, indicating that hybrid parasites persisted and recombined beyond the initial hybridization event. Our observations challenge traditional views of trypanosome population biology and encourage future research on the role of hybridization in spreading genes for drug resistance, pathogenicity and virulence. [ABSTRACT FROM AUTHOR]

Background: Especially on islands closer to the mainland, such as the Canary Islands, different lineages that originated by multiple colonization events could have merged by hybridization, which then could have promoted radiation events (Herben et al., J Ecol 93: 572-575, 2005; Saunders and Gibson, J Ecol 93: 649-652, 2005; Caujapé-Castells, Jesters, red queens, boomerangs and surfers: a molecular outlook on the diversity of the Canarian endemic flora, 2011). This is an alternative to the scenario where evolution is mostly driven by drift (Silvertown, J Ecol 92: 168-173, 2004; Silvertown et al., J Ecol 93: 653-657, 2005). In the former case hybridization should be reflected in the genetic structure and diversity patterns of island species. In the present work we investigate Micromeria from the Canary Islands by extensively studying their phylogeographic pattern based on 15 microsatellite loci and 945 samples. These results are interpreted according to the hypotheses outlined above. Results: Genetic structure assessment allowed us to genetically differentiate most Micromeria species and supported their current classification. We found that populations on younger islands were significantly more genetically diverse and less differentiated than those on older islands. Moreover, we found that genetic distance on younger islands was in accordance with an isolation-by-distance pattern, while on the older islands this was not the case. We also found evidence of introgression among species and islands. Conclusions: These results are congruent with a scenario of multiple colonizations during the expansion onto new islands. Hybridization contributes to the grouping of multiple lineages into highly diverse populations. Thus, in our case, islands receive several colonization events from different sources, which are combined into sink populations. This mechanism is in accordance with the surfing syngameon hypothesis. Contrary to the surfing syngameon current form, our results may reflect a slightly different effect: hybridization might always be related to colonization within the archipelago as well, making initial genetic diversity to be high to begin with. Thus the emergence of new islands promotes multiple colonization events, contributing to the establishment of hybrid swarms that may enhance adaptive ability and radiation events. With time, population sizes grow and niches start to fill. Consequently, gene-flow is not as effective at maintaining the species syngameon, which allows genetic differentiation and reproductive isolation to be established between species. This process contributes to an even further decrease in gene-flow between species. [ABSTRACT FROM AUTHOR]

• Background and Aims The extent to which hybridization leads to gene flow between plant species depends on the structure of hybrid populations. However, if this varies between locations, species barriers might prove permeable in some locations but not in others. To assess possible variation in hybrid population structure, the magnitude and direction of natural hybridization between two Chinese endemic species, Rhododendron spiciferum and Rhododendron spinuliferum, were evaluated. • Methods Thirteen nuclear microsatellite markers were employed to characterize 566 individuals collected from 15 non-allopatric populations and nine allopatric parental populations. Chloroplast DNA (cpDNA) sequences were obtained from a subset of samples. Genetic structure and direction of gene flow was determined using a combination of STRUCTURE and NEWHYBRIDS analysis. • Key Results Nuclear analysis revealed that parental taxa formed two genetically distinct clusters and hybrids shared the genetic background of both parents and did not form a separate genetic lineage. Overall, hybrid swarms were dominated by early- and later-generation hybrids, with a significantly higher proportion of hybrids (59·6 %) possessing >50 % R. spiciferum-like nuclear germplasm. The cpDNA analysis further indicated that a significantly greater proportion of hybrids (61·1 %) possessed the R. spiciferum cpDNA haplotype. • Conclusions Gene flow between R. spiciferum and R. spinuliferum was found to be bidirectional in 14 of the 15 hybrid swarms and asymmetrical in six hybrid swarms. Asymmetrical gene flow was evident for only nuclear DNA (nDNA) in two populations, for only cpDNA in three populations, and for both nDNA and cpDNA in one population. Collectively, the variation in genetic structure found among the 15 hybrid swarms suggests that introgression rather than hybrid speciation is a more likely outcome of hybridization between these hybridizing taxa. [ABSTRACT FROM AUTHOR]

Cambodia is known to harbour three distinct species of Southeast Asian leaf turtles ( Cyclemys spp.), which are heavily traded and common in seizures of wildlife. Confiscated leaf turtles are often released to natural habitats. Thus, an exact knowledge of the distribution of the individual species is of great importance to avoid the introduction of non-native turtles, posing the risk of competition and hybridization. In this study, we examine a recently discovered leaf turtle population from Phnom Kulen National Park using external morphology, 17 unlinked microsatellite loci and the mitochondrial cytochrome b gene. Leaf turtles from the Phnom Kulen National Park morphologically resemble C. oldhamii, but harbour mitochondrial haplotypes of C. atripons. With respect to microsatellite loci, the turtles are distinct from C. atripons. Unfortunately no material of C. oldhamii was available from Cambodia. We propose that the Phnom Kulen population represents either a natural hybrid swarm of C. atripons and C. oldhamii or a distinct undescribed species with introgressed mitochondria of C. atripons. This underlines that genetic differentiation of wild leaf turtle populations in Cambodia is complex and suggests that this differentiation pattern becomes increasingly threatened by translocations of confiscated individuals. For drawing a definite conclusion about the taxonomic status of the Phnom Kulen population, denser sampling of other Cambodian leaf turtle populations would be required, in particular of C. oldhamii. [ABSTRACT FROM AUTHOR]

Diversification in Amelanchier tetraploid apomicts differs from that of diploid sexuals and produces groups that are taxonomically difficult. Apomixis facilitates expansion of ecologically successful genotypes into numerous, narrowly distributed, and often minimally distinct microspecies. Residual sexuality in tetraploids creates hybrid swarms and intergradation of taxa. This gene flow is evident in DNA sequences from nuclear and chloroplast regions that record mostly allotetraploid, convoluted histories. Ongoing apomixis in successful tetraploid genotypes fosters their expansion into geographically widespread phenotypic clusters.We delimit such clusters as species and deny species status to microspecies.We demonstrate polyploid complexity and our approach to species delimitation in three taxa of Amelanchier. The tetraploid microspecies A. 'rubra' of southeastern Maine, while morphologically distinct, hybridizes with sympatric congeners. Eastern North American A. bartramiana contains diploids and polyploids (tetraploids and a few triploids) that are sometimes morphologically semi-cryptic. We group all ploidy levels in the A. bartramiana agamic complex and recognize as a species the diploid ( A. bartramiana). The tetraploid is not given species status because it intergrades extensively with tetraploid congeners, as exemplified by the nothospecies named here, A. × neglecta. Western North American A. cusickii is tetraploid, mostly distinct morphologically and ecologically, distinct genetically, and merits species status. [ABSTRACT FROM AUTHOR]

The morphological traits and genetic backgrounds of hybrid individuals in a hybrid zone reflect the history of that zone. In the hybrid zone between Rhododendron japonoheptamerum var. hondoense (RJH) and R. japonoheptamerum var. kyomaruense (RJK), flower morphological traits that can be used to distinguish the two varieties were measured and leaves were sampled for DNA extraction. Reference populations consisting of pure RJH and RJK were also used. Genotype data for individuals were obtained by the multiplexed ISSR genotyping by sequencing (MIG-seq) method. RJH and RJK in the reference populations were morphologically and genetically clearly differentiated. In the hybrid zone studied, although there were morphologically pure RJH and RJK, and hybrids between them, most individuals, including those that were morphologically pure, had ancestries from both RJH and RJK. There were no significant correlations between morphological traits and the proportion of ancestry within an individual. These results suggest that this hybrid zone originated from the hybridization between the RJH and RJK in the past. The result of model comparison among population demographic models also supported this hypothesis, and the time when the hybrid zone was established was estimated to be 410,000 years ago. It is considered that accumulation of recombinations subsequent to the formation of the hybrid zone contributed to the inconsistency between the morphological traits and the fraction of each ancestral genome within an individual. [ABSTRACT FROM AUTHOR]