Species Concept Research Articles

The contours of evolution: In defence of Darwin's tree of life paradigm.

Both the concept of a Darwinian tree of life (TOL) and the possibility of its accurate reconstruction have been much criticized. Criticisms mostly revolve around the extensive occurrence of lateral gene transfer (LGT), instances of uptake of complete organisms to become organelles (with the associated subsequent gene transfer to the nucleus), as well as the implications of more subtle aspects of the biological species concept. Here we argue that none of these criticisms are sufficient to abandon the valuable TOL concept and the biological realities it captures. Especially important is the need to conceptually distinguish between organismal trees and gene trees, which necessitates incorporating insights of widely occurring LGT into modern evolutionary theory. We demonstrate that all criticisms, while based on important new findings, do not invalidate the TOL. After considering the implications of these new insights, we find that the contours of evolution are best represented by a TOL.

Distinct taxonomic practices impact patterns of bird endemism in the South American Cerrado savannas

Abstract Identifying endemic species and the areas of endemism delimited by them is central to biogeography. However, the impact of distinct taxonomic approaches on these patterns is often neglected. We investigated how three different taxonomic approaches impact the patterns of bird endemism in the Cerrado. The first two approaches (at species and subspecies levels) were based on traditional taxonomy based on the biological species concept. The third approach was based on a revised alternative taxonomy that sought to identify evolutionarily significant units (ESUs). In this third approach, after identifying the endemic taxa using traditional taxonomy, we revised their validity, removing biologically meaningless entities. We then detected the areas of endemism delimited by these endemic taxa under the three taxonomic approaches. We found that traditional taxonomy at the species level underestimated bird endemism by ignoring some ESUs that were considered subspecies. In contrast, traditional taxonomy at the subspecies level overestimated bird endemism, leading to the recognition of spurious areas of endemism because several of the purported endemic subspecies were taxonomic artefacts. The revised taxonomy provided a more refined picture of patterns of avian endemism in the Cerrado, suggesting that the use of ESUs improves the results of biogeographical analysis.

Keystone species: Ecological architects of biodiversity and stability: Review

This review article delves into the pivotal role of keystone species in shaping and maintaining the balance of ecosystems. Exploring the historical roots of the keystone species concept, this review discusses their ecological significance, mechanisms of influence, and the far-reaching impacts of their presence or absence. Drawing on examples from terrestrial, aquatic, and forest ecosystems, this paper examine the intricate web of interactions that define keystone species. The article also addresses conservation challenges and opportunities, highlighting the importance of protecting these species to ensure the resilience and sustainability of ecosystems.

Discovering unknown Madagascar biodiversity: integrative taxonomy of raft spiders (Pisauridae: Dolomedes).

Madagascar is a global biodiversity hotspot, but its biodiversity continues to be underestimated and understudied. Of raft spiders, genus Dolomedes Latreille, 1804, literature only reports two species on Madagascar. Our single expedition to humid forests of eastern and northern Madagascar, however, yielded a series of Dolomedes exemplars representing both sexes of five morphospecies. To avoid only using morphological diagnostics, we devised and tested an integrative taxonomic model for Dolomedes based on the unified species concept. The model first determines morphospecies within a morphometrics framework, then tests their validity via species delimitation using COI. It then incorporates habitat preferences, geological barriers, and dispersal related traits to form hypotheses about gene flow limitations. Our results reveal four new Dolomedes species that we describe from both sexes as Dolomedes gregoric sp. nov., D. bedjanic sp. nov., D. hydatostella sp. nov., and D. rotundus sp. nov. The range of D. kalanoro Silva & Griswold, 2013, now also known from both sexes, is expanded to eastern Madagascar. By increasing the known raft spider diversity from one valid species to five, our results merely scratch the surface of the true Dolomedes species diversity on Madagascar. Our integrative taxonomic model provides the framework for future revisions of raft spiders anywhere.

Phylogenetic analyses of the leafhopper tribe Chiasmini Distant, 1908 and delimination of species of the genus Exitianus Ball, 1929 (Hemiptera: Cicadellidae: Deltocephalinae: Chiasmini) in China based on molecular data

Previous phylogenetic analyses of the grass-specialist leafhopper tribe Chiasmini have resolved relationships among genera but have included few representatives of individual genera. Here the phylogeny of 20 Chinese species belonging to 8 chiasmine genera was investigated by combining DNA sequence data from two mitochondrial genes (COI, 16S) and two nuclear genes (H3, 28S). In both maximum likelihood (ML) and Bayesian inference (BI) analyses, relationships among genera were largely consistent with prior analyses, with most members of the tribe placed into two sister clades: (Exitianus + Nephotettix) and the remaining five sampled genera. To examine morphology-based species definitions in the taxonomically difficult genus Exitianus Ball, 1929, one mitochondrial gene (COI) and one nuclear gene (ITS2) were used to infer the phylogenetic relationships and status of two common and widespread species and compare the performance of different molecular species-delimitation methods. These analyses divide the included populations into two well-supported clades corresponding to current morphological species concepts but some inconsistencies occurred under the jMOTU, ABGD and bPTP methods depending on the which gene and analytical parameter values were selected. Considering the variable results yielded by methods employing single loci, the BPP method, which combines data from multiple loci, may be more reliable in Exitianus.

Morphology and Phylogeny Reveal Three New Species of Cytospora Associated with Tree Cankers in China.

Cytospora (Cytosporaceae, Diaporthales) is a fungal genus that usually inhabits plants as endophytes, saprobes, as well as pathogens. Species of this genus are characterized by possessing allantoid hyaline conidia and ascospores. Samples with typical Cytospora canker symptoms on Prunus davidiana, P. padus and Salix sp. were collected in Tibet and Xinjiang, China. Species were identified using both morphological and molecular approaches of combined loci of internal transcribed spacer region rDNA (ITS), the partial actin (act) region, RNA polymerase II second largest subunit (rpb2), the translation elongation factor 1-alpha (tef1) gene and the partial be-ta-tubulin (tub2) gene. Six isolates in the present study formed three distinct clades from previously known species. Cytospora hejingensis sp. nov. from Salix sp., C. jilongensis sp. nov. from P. davidiana and C. kunsensis from P. padus were proposed herein. The current study improves the understanding of species concept in Cytospora.

A decadal study reveals that restoration guided by an umbrella species does not reach target levels

AbstractMaintaining structural and functional elements of ecosystems are essential in order to preserve biodiversity and ecosystem function. As a means of guiding conservation work, the umbrella species concept was developed. In Sweden, one putative umbrella species, the white‐backed woodpecker, has guided conservation and restoration of deciduous forests for two decades.Here, we evaluate the decadal effects of restoration aimed at the white‐backed woodpecker on biodiversity of saproxylic beetles. We compare stands that were restored 12 to 21 years ago to non‐restored stands and historical white‐backed woodpecker habitats acting as restoration target stands.Restored stands contained higher deciduous deadwood volumes than non‐restored stands but lower volumes than restoration target stands. The deadwood in restored stands was concentrated in later decay stages, whereas target stand deadwood was more evenly distributed across decay stages.Restored stands had similar species richness and abundance of most groups of saproxylic beetles compared with non‐restored stands while not reaching the levels of restoration target stands. Species assemblages differed among all stand types with restored stands supporting late decay stage and generalist species while target stands supported more deciduous associated and threatened species.Synthesis and applications: We conclude that after one to two decades, restoration improve stand structure and benefit beetle diversity but that target levels are not yet reached. Thus, only partial restoration is achieved. Our results stress that for restoration to be successful both continuous and repeated restoration efforts are needed and that it is important to identify target levels of important habitat characteristics when assessing restoration outcome.

Patterns, processes and conservation management consequences of intraspecific diversity, illustrated by fishes from recently glaciated lakes

Abstract Patterns in phenotypic and genotypic diversity within many species are becoming increasingly apparent, although there remain many species for which such patterns have yet to be described adequately. Fishes from recently glaciated ecosystems are likely to be particularly rich in intraspecific diversity, yet current conservation management strategies are, in many parts of the world, particularly in Europe, conventionally and overwhelmingly focused on species, regardless of competing species concepts, and appropriate policies for managing diversity at a sub‐specific level still have to be developed. Occasional attempts to protect certain vulnerable ecotypes and proposed alternative units of conservation (e.g. ‘Pragmatic Species’ or ‘Evolutionarily Significant Units’) reinforce the conventional primacy of contemporary expressed patterns of variation. Intraspecific phenotypic and genotypic patterns are ultimately the result of complex processes of divergence; conservation approaches that focus on the products of evolution largely ignore the processes that generate and maintain those patterns. Policies that acknowledge the continuation of evolution, the derivation of novel diversity over often very short time spans and the role of environment in initiating and perpetuating these processes are poorly integrated into management strategy. To address possible deficits, where intraspecific diversity is not addressed in management practice, we believe it to be important first to characterize hidden genetic and phenotypic diversity, which may intimate eco‐evolutionary processes, initially among species of high conservation status. A second step should be to use an approach to intraspecific diversity that illuminates the ultimate processes and mechanisms that bring about that diversity, which also concedes the central role of the environment and affords adequate protection to the ecosystems that drive these processes, such as the United Nations Convention on Biological Diversity (CBD) Ecosystems approach.

Redescription and revised genus placement of Oliarus pinicolus Osborn, 1926, with notes on Antillean Pentastirini (Hemiptera: Fulgoromorpha: Cixiidae).

Oliarus pinicolus Osborn, 1926 is a little-known planthopper described from western Cuba on Cuban pine (Pinus cubensis). As part of a review of the sprawling New World cixiid genus Melanoliarus Fennah, 1945, the species is herein redescribed and illustrated for the first time, including the male terminalia. After comparison to similar species in the region, we transfer the species to Nivcentia Holzinger, 2004, as Nivcentia pinicolus comb. nov., based on characteristics of the male terminalia and provide an amended description of the genus. We also designate a lectotype for Oliarus pinicolus to ensure the stability of the species concept described here. A checklist of Antillean Pentastirini is included with taxonomic comments on the species and genera of the region. The pentastirine species of Cuba are illustrated.

Parallels of quantum superposition in ecological models: from counterintuitive patterns to eco-evolutionary interpretations of cryptic species

BackgroundSuperposition, i.e. the ability of a particle (electron, photon) to occur in different states or positions simultaneously, is a hallmark in the subatomic world of quantum mechanics. Although counterintuitive at first sight, the quantum world has potential to inform macro-systems of people and nature. Using time series and spatial analysis of bird, phytoplankton and benthic invertebrate communities, this paper shows that superposition can occur analogously in redundancy analysis (RDA) frequently used by ecologists.ResultsWe show that within individual ecosystems single species can be associated simultaneously with different orthogonal axes in RDA models, which suggests that they operate in more than one niche spaces. We discuss this counterintuitive result in relation to the statistical and mathematical features of RDA and the recognized limitations with current traditional species concepts based on vegetative morphology.ConclusionWe suggest that such “quantum weirdness” in the models is reconcilable with classical ecosystems logic when the focus of research shifts from morphological species to cryptic species that consist of genetically and ecologically differentiated subpopulations. We support our argument with theoretical discussions of eco-evolutionary interpretations that should become testable once suitable data are available.

Evaluating Spatial Coverage of the Greater Sage-Grouse Umbrella to Conserve Sagebrush-Dependent Species Biodiversity within the Wyoming Basins

Biodiversity is threatened due to land-use change, overexploitation, pollution, and anthropogenic climate change, altering ecosystem functioning around the globe. Protecting areas rich in biodiversity is often difficult without fully understanding and mapping species’ ecological niche requirements. As a result, the umbrella species concept is often applied, whereby conservation of a surrogate species is used to indirectly protect species that occupy similar ecological communities. One such species is the greater sage-grouse (Centrocercus urophasianus), which has been used as an umbrella to conserve other species within the sagebrush (Artemisia spp.) ecosystem. Sagebrush-steppe ecosystems within the United States have experienced drastic loss, fragmentation, and degradation of remaining habitat, threatening sagebrush-dependent fauna, resulting in west-wide conservation efforts to protect sage-grouse habitats, and presumably other sagebrush wildlife. We evaluated the effectiveness of the greater sage-grouse umbrella to conserve biodiversity using data-driven spatial occupancy and abundance models for seven sagebrush-dependent (obligate or associated) species across the greater Wyoming Basins Ecoregional Assessment (WBEA) area (345,300 km2) and assessed overlap with predicted sage-grouse occurrence. Predicted sage-grouse habitat from empirical models only partially (39–58%) captured habitats identified by predicted occurrence models for three sagebrush-obligate songbirds and 60% of biodiversity hotspots (richness of 4–6 species). Sage-grouse priority areas for conservation only captured 59% of model-predicted sage-grouse habitat, and only slightly fewer (56%) biodiversity hotspots. We suggest that the greater sage-grouse habitats may be partially effective as an umbrella for the conservation of sagebrush-dependent species within the sagebrush biome, and management actions aiming to conserve biodiversity should directly consider the explicit mapping of resource requirements for other taxonomic groups.

A review of the woody bamboos (Poaceae: Bambusoideae: Bambuseae) of Trinidad and Tobago

Trinidad and Tobago are important islands to Neotropical woody bamboo taxonomy. Trinidad is a type locality for two widely applied names with poorly defined species concepts: Arthrostylidium pubescens and A. excelsum, and two potentially endemic species: Chusquea cylindrica and Rhipidocladum prestoei. Few resources exist for the islands to adequately identify all the woody bamboo species that putatively grow there. The serialized vascular flora of Trinidad and Tobago (1928–1992), for instance, lacks a treatment for Poaceae. Moreover, the most speciose native genus, Arthrostylidium, is only partially revised, with the emphasis on the South American species and not those of the West Indies. Our objective is to critically review the woody bamboos of Trinidad and Tobago, clarify which species are or have been known from the islands, and provide an identification key, species accounts and distribution maps for the revised list of taxa. We conducted fieldwork campaigns in 2021–2023, and reviewed herbarium specimens and human observation records of woody bamboos from the islands. Newly collected specimens were vouchered and all woody bamboo records were georeferenced and plotted using QGIS. We confirmed two species of native woody bamboo and four species of introduced woody bamboo were extant on Trinidad. An additional three Western Hemisphere species have historic records of occurrence on the islands. Native species diversity correlated well with previously identified floristic hotspots. One introduced species, Bambusa vulgaris, is common on both islands. To the best of our knowledge, there are currently no native woody bamboo species present on Tobago, however, A. pubescens appears to have been growing along the Main Ridge in the past. The historic presence of some species not currently found may be the result of dynamic and/or stochastic colonization events among the islands and mainland South America.

A lineage perspective on hominin taxonomy and evolution.

An uncritical reliance on the phylogenetic species concept has led paleoanthropologists to become increasingly typological in their delimitation of new species in the hominin fossil record. As a practical matter, this approach identifies species as diagnosably distinct groups of fossils that share a unique suite of morphological characters but, ontologically, a species is a metapopulation lineage segment that extends from initial divergence to eventual extinction or subsequent speciation. Working from first principles of species concept theory, it is clear that a reliance on morphological diagnosabilty will systematically overestimate species diversity in the fossil record; because morphology can evolve within a lineage segment, it follows that early and late populations of the same species can be diagnosably distinct from each other. We suggest that a combination of morphology and chronology provides a more robust test of the single-species null hypothesis than morphology alone.

Steinernema yirgalemense (Steinernematidae) to control Phlyctinus callosus and Phlyctinus xerophilus (Curculionidae)

Summary Considerable progress has been made in the surveying, taxonomy, screening, mass production and formulation of entomopathogenic nematodes (EPN) and their associated symbiotic bacteria in South Africa. Steinernema yirgalemense isolate 157-C is one of the most promising native EPN candidates with regards to virulence, its broad insect-host spectrum, and can be readily mass-produced and formulated into a commercial product. The banded fruit weevils, Phlyctinus callosus sensu stricto and Phlyctinus xerophilus, previously grouped together under the Phlyctinus callosus sensu lato species concept, are native entimine weevils of economic importance to deciduous fruit, grapevine and berries in the Western Cape province of South Africa. This study investigated potential differences in baseline susceptibility of larvae and pupae of the two weevil species to S. yirgalemense in laboratory screenings. The test arena used was 24-well bioassay plates, with an inoculation concentration of 200 infective juveniles (IJ) insect−1 for larvae and 100 IJ insect−1 for pupae. Infection was determined 48 h and 96 h after inoculation. Field-efficacy of S. yirgalemense, applied at a concentration of 60 IJ cm−2, against larvae of the two weevil species was determined in an ecologically relevant semi-field trial. In all cases in vitro mass-produced IJ of S. yirgalemense were used. No baseline differential susceptibility between P. callosus and P. xerophilus larvae was obtained in laboratory screenings. Phlyctinus pupae were approximately twice as susceptible compared to larvae, with significant differences between bioassay batches. Approximately 45% control of P. xerophilus larvae was obtained after 96 h of exposure to S. yirgalemense in the field, differing significantly from the control and P. callosus treatment. Low levels of Phlyctinus larval infection by native EPN (confirmed as Heterorhabditis bacteriophora from one P. xerophilus cadaver) occurred in both control and EPN treatment groups under field conditions.

Screening of among seventeen sunflowers (Helianthus annuus L.) genotypes for oil content and the first flowering day using random amplified polymorphic DNA markers

Background Sunflower refers to the tribe Helianthus, subtribe Helianthinae, and family Asteraceae, which collectively contains 20 genera and 400 species. An important oilseed crop that yields edible oil is Helianthus annuus L. Objective The primary goal of the current study was to assess the genetic diversity of 17 genotypes of sunflower (Helianthus annuus L) To measure the oil content during the initial flowering period and to reach the highest percentage of oil can be obtained from the first flowering day. Materials and methods Five RAPD (random amplified polymorphic DNA) primers were used to detect the genetic diversity of the 17 sunflower hybrid genotypes obtained from Spain. Phylogenetic relationships of 17 sunflower genotypes were determined using three replications and 6 m lines on August 15, 2019, at the National Research Centre farm in Nubaria as part of a donation from the German corporation (strobe), Spain. To analyze the genetic diversity and phylogenetic linkages in sunflower germplasm, DNA fingerprinting and the Random Amplified Polymorphic DNA (RAPD) molecular marker approach were also used. Results and conclusion The oil content of 17 sunflower genotypes (Helianthus annuus L.) was assessed, with values ranging from 46 to 50%, with the highest values falling into five genotypes. However, the two genotypes were found to have the lowest oil percentage (46%). The early age and oil percentage differed among the varieties. In the Tornado and Elves genotypes, the longest and shortest days were 59 and 47, respectively. The means and standard errors for all statistical data are reported. Statistical significance was evaluated using the LSD. P values were considered statistically significant at P less than or equal to 0.05. According to the findings, RAPD primers generated 49 bands with a size range of 0.1–3 kb and an 87.75% polymorphism percentage. For RAPD, 43 polymorphic bands with distinct bands were observed. Morphological features and RAPD analysis separated the UPGMA Dendrogram into three groups. Jaccard’s coefficient was used to analyze the genetic similarity matrix, and a morphological study revealed that Tornado and Elvas, both from Spain, shared the most genetic similarity (0.970). RAPD analysis and morphological features are useful in identifying genetic variants. Conclusion, according to our findings, Helianthus annuus L. has a significant variation ratio. Indicating substantial diversity across the 17 sunflower genotypes, the genetic similarity index calculated using pooled data from RAPD markers showed an extensive range from 0.645 to 0.986. This study may be a reference for future research on Helianthus annuus L. and may support breeding initiatives and species concepts.

Beyond Animal Charisma: A Sociological Approach to Charismatic Species

Abstract Sociologists have been debating the nature of charisma since the discipline’s inception. Recent debates in the sociology of charisma concern the role of social interaction and the place of organisations in the generation of charisma. As these debates have developed, the interdisciplinary field of conservation has begun to debate the concept of charismatic species. To date, literature from the conservation sciences has identified those species most likely to be identified as charismatic and those variables most frequently associated with charismatic species. However, little theorising has been done on the causes of charisma in charismatic species. This article uses the case of charismatic species to outline sociological arguments about charisma more generally. This theoretical exercise advances the literature in both sociology and conservation in several ways. For sociologists, the case of charismatic species shows that seemingly competitive models of charisma are in fact complementary. For those interested in the uses of charismatic species for conservation, this article demystifies charismatic species, demonstrating the ways in which they are historically and socially constructed.

An appraisal of taxonomic issues in Lower to mid-Cretaceous mesorbitolinids (larger benthic foraminifera)

Species differentiation within the genus Mesorbitolina Schroeder 1962 is primarily based on the general structure of the megalospheric embryo and its biometrics. The taxonomy of three taxa, namely Mesorbitolina texana (Roemer 1849), Mesorbitolina subconcava (Leymerie 1878) and Mesorbitolina pervia (Douglass 1960) is complicated due to differing species concepts between authors, and, in the case of the first two named, by missing type designations in the original descriptions as well as disagreements with respect to their type-localities. Herein, it is demonstrated that M. pervia is the junior synonym of Mesorbitolina birmanica (Sahni 1937) due to priority reasons, both taxa characterized by a similar-sized plano-convex protoconch. Some concepts of M. texana and M. subconcava can also be placed in M. birmanica, but not those as defined by lectotypes. Published data for M. birmanica suggest a late Aptian (late Gargasian) to early (? late) Albian age and a cosmopolitan distribution. Mesorbitolina texana appears slightly earlier in the late Aptian persisting into the middle Albian, and a distribution ranging from the southern USA to the Middle East.

Fusarium species causing root rot and wilt in tomato in Brazil

AbstractA high frequency of plants showing symptoms of wilting and root rot has been observed in tomato‐producing areas in Santarém and Belterra, Pará, Brazil. These plants showed symptoms ranging from yellowing to wilting, with roots displaying reduced development and darkening of the xylem. Four fungal isolates, derived from a collection of 12 obtained from symptomatic plants, were chosen for identification using both morphological and phylogenetic species concepts. To determine the identity of the fungi, DNA was extracted and used in PCR reactions. PCR products were sequenced from the TEF‐1α and RBP2 regions and compared with sequences in GenBank using BLASTn. Based on the phylogenetic analyses, the isolates were identified as Fusarium falciforme and Fusarium suttonianum, belonging to the species complex Fusarium solani – (FSSC), and Fusarium triseptatum, belonging to the species complex Fusarium oxysporum – (FOSC). The fourth isolate, COUFPI 295, grouped within a clade of F. kalimantanense and F. sangayamense from FOSC. The fulfilment of Koch's postulates confirmed that all isolates induced symptoms of root rot and concomitant reduction in root mass, leading to observable wilting symptoms. This is the first report of F. suttonianum, F. falciforme and F. triseptatum causing root rot and wilt in tomato plants in Brazil.

Cladistic species definitions can lead to under-representation of biodiversity from adaptive radiations

Abstract Many species are paraphyletic, but current taxonomic practices often do not recognize this, and attempts are made to apply a monophyletic species concept. While allowing the recognition of ecomorphologically equivalent, or even phenotypically indistinguishable allopatric, taxa as species, this often leads to combining distinctive local forms (such as cave-adapted populations) or even whole adaptive radiations (often in lakes) with widespread paraphyletic species to force species monophyly. It is suggested that this has negative consequences for our documentation and understanding of biodiversity, as well as for conservation, through issues such as lack of IUCN red-listing.

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.