Abstract Shell morphology in terrestrial gastropods is widely assumed to reflect climatic adaptation, yet empirical support for body size-climate relationships remains inconsistent across scales. We investigated how shell morphology is associated with large-scale climatic gradients in nine rock-dwelling Pyramidula species across 228 sites in the Western Palearctic. We hypothesised that climatic conditions linked to high solar radiation and low precipitation are associated primarily with shell traits potentially mediating conductive heat exchange with sun-exposed limestone substrates rather than with overall body size. For 519 adult shells, we analysed shell width, height, width/height ratio and a novel composite shell geometry index ( SGI ) using linear mixed-effects models with species and locality as random factors. Shell width showed the strongest and most consistent climatic associations, decreasing with increasing solar radiation and decreasing precipitation. In contrast, shell height and body volume exhibited weak or no independent climatic relationships. The SGI displayed intermediate but consistent responses, particularly to precipitation of the driest month. An additive model combining solar radiation and low precipitation explained nearly 19% of shell width variation. Responses were directionally consistent across species, suggesting shared morphological responses to similar climatic conditions. Observed patterns indicate that shell geometry, particularly shell width, is more closely associated with climatic gradients related to heat and drought stress than is overall body size.
Abstract Understanding how closely related sympatric species achieve coexistence through niche partitioning is a central question in ecology. Lepidopteran larvae provide powerful models for studying niche differentiation owing to their host-plant specificity, diverse feeding strategies, and pronounced morphological adaptations. We investigated the coexistence of two congeneric butterfly larvae, Papilio xuthus Linnaeus, 1767 and P. machaon Linnaeus, 1758, on their shared host plant Dictamnus dasycarpus by integrating field surveys, ultrastructural morphological analyses, and quantitative color measurements. The two species exhibited clear niche differentiation across temporal, spatial, trophic, and defensive dimensions. P. xuthus emerged earlier, fed cryptically on leaves, and possessed mouthparts and crochets suited for horizontal movement. By contrast, P. machaon emerged later, fed openly on flowers and fruits, displayed stronger grasping adaptations, and showed conspicuous coloration consistent with aposematism. These multidimensional differences are consistent with niche partitioning and may facilitate coexistence between the two sympatric congeners, providing an empirical case that advances understanding of niche differentiation and species coexistence.
Abstract Zoraptera represents a species-poor evolutionary lineage of polyneopteran insects with a relict circumtropical distribution. This study presents a comprehensive phylogeny, evolutionary timeline, and historical biogeography of all recognized Zoraptera subfamilies, based on analyses of 18 species representing eight genera using multi-gene datasets from both mitochondrial and nuclear loci. It utilizes 12 polyneopteran fossils as calibration points, including two amber fossils of Zoraptera. The Bayesian time-calibrated molecular phylogenetic tree inferred in BEAST suggests that the major Zoraptera lineages, Zorotypidae and Spiralizoridae, probably originated on the supercontinent Pangaea (~309 Mya). Zorotypinae and Latinozorinae maintained a circumtropical distribution until the Mesozoic/Cenozoic boundary. Subsequently, both subfamilies became extinct in Africa, and Latinozorinae also disappeared in Asia. We estimate that the Spiralizorinae diversified during the Late Triassic period in south-western Gondwana, while the ancestor of Spermozorinae emerged in the eastern Laurasia and remained restricted to present-day Southeast Asia. The current circumtropical distribution reflects a complex evolutionary history marked by significant distributional changes and extinctions, and contributes to our understanding of tropical insect biogeography.
Megalopodidae are a relatively small and rare family of phytophagous beetles in the superfamily Chrysomeloidea, whose adults and larvae are fully dependent on host plants. Despite its nearly global distribution, the Chinese fauna significantly contributes to the family's diversity, with the genera Clythraxeloma and Temnaspis accounting for approximately 73% and 45% of their respective global species richness, respectively. However, difficulties in obtaining specimens have continuously hindered molecular systematic research, leaving the phylogenetic relationships within Megalopodidae poorly understood. Here, through extensive fieldwork spanning more than a decade, we obtained 113 samples representing 29 species across three genera (Clythraxeloma, Temnaspis and Zeugophora) within two subfamilies in China, and produced their molecular data of mitochondrial genes (col and cytb) and nuclear rRNA genes (18S and 28S) by Sanger sequencing method. We performed phylogenetic analysis based on these four molecular makers. Our phylogenetic analyses provide strong support for the monophyly of Megalopodidae, including its subfamilies Megalopodinae and Zeugophorinae, as well as the genera Temnaspis and Zeugophora. Clythraxeloma, however, was reconstructed as non-monophyletic. Furthermore, our phylogenetic analyses suggest that Megalopodinae is the sister group to Zeugophorinae. A pronounced evolutionary conservatism in host plant associations was detected in Temnaspis and in Zeugophorinae, indicating that closely related megalopodids tend to utilize congeneric or confamilial host plants. These findings provide critical insights into the evolutionary history and ecological specialization of the phytophagous beetle family Megalopodidae.
Polyclad flatworms are a diverse group of free-living Platyhelminthes, most of which inhabit marine environments. As predators in the marine food web, they play a crucial role in the marine brates in China, and most species were described prior to 1943. In order to update this status, in ing both morphological and molecular data. A total of seven species were described, including was established. Based on the newly supplemented data, we re-evaluate the phylogenetic relationships among relevant families and genera. This study enriches the known diversity of polyclads in Chinese waters, increasing the total number of recorded species to 29, and provides new insights into the refinement of global zoogeographic patterns of polyclads.
The specific nomenclature of the Pleistocene sabre-toothed felid Homotherium in the northern hemisphere has been a matter of contention for over a century up till the present day. Its correct taxonomy and systematics have, however, implications for our understanding of evolutionary patterns and biogeography of the genus. Here, we briefly review the literature and conclude that there existed only one intra-specifically variable species, to be called Homotherium latidens (Owen, 1846). It has priority over the name H. crenatidens (Fabrini,1890). H. latidens had a wide distribution in time and space, i.e. the Early, Middle and Late Pleistocene and the northern hemisphere (Eurasia and North America). The large intra-specific morphological variation over time does not exceed that of a single population of large felines showing sexual dimorphism, supporting the long-term survival of a single species of feline top predator.
The diving beetle genus Allodessus Guignot, 1953 comprises five described species distributed across the Pacific. However, its systematics have long been obscured by uncertain species boundaries and incomplete molecular sampling. One of its members, Allodessus skottsbergi (Zimmerman, 1920), is endemic to Rapa Nui (Easter Island, Chile) and had not been recorded since its description nearly a century ago, prompting assumptions of extinction. Here, we document the rediscovery of A. skottsbergi in ephemeral ponds within the Rano Kau volcano crater and provide the first molecular data for the species. Using low-coverage whole-genome sequencing, we recovered its mitochondrial genome and key nuclear markers, which were integrated into a phylogenetic analysis of Allodessus. Contrary to earlier hypotheses, A. skottsbergi is not the sister lineage to the remaining species; instead, A. megacephalus forms the basal lineage to Allodessus bistrigatus plus A. skottsbergi. Analysis of the mitochondrial cox1 gene revealed negligible genetic divergence among A. bistrigatus, A. oliveri, and A. thienemanni, and morphological re-examination did not identify consistent diagnostic differences, prompting the formal synonymisation of A. oliveri and A. thienemanni under A. bistrigatus. In contrast, A. skottsbergi is supported as a distinct species by its unique morphology, geographic isolation, and genetic divergence. Its rediscovery provides new insight into the evolution and biogeography of Allodessus and underscores the critical conservation importance of temporary pond habitats on Rapa Nui.
An integrative approach based on morphological characteristics and DNA data from the mitochondrial COI gene has revealed five new species of the pill millipede genus Rhopalomeris Verhoeff, 1906 from Thailand: R. muka Sapparojpattana & Likhitrakarn, sp. nov., R. lentiginosa Sapparojpattana & Likhitrakarn, sp. nov., R. dulcia Sapparojpattana & Likhitrakarn, sp. nov., R. punctata Sapparojpattana & Likhitrakarn, sp. nov., and R. verhoeffi Sapparojpattana & Likhitrakarn, sp. nov. The five new species are distinguishable from their congeners by distinctive color patterns and telopod structure. The interspecific genetic divergences between the new species and other Rhopalomeris species ranged from 7.86 to 13.71%. Intraspecific genetic divergences within these five species ranged from 0 to 4.53%, with the highest divergences found in R. carnifex and R. verhoeffi sp. nov. This is consistent with both the wide distribution range and the significant intraspecific morphological variations observed in these latter two species. Furthermore, the taxonomic scope of R. carnifex in Thailand is reviewed, and intraspecific morphological variations within R. carnifex and R. verhoeffi sp. nov. are discussed. A distribution map, morphological illustrations from SEM, and an updated key to all known Rhopalomeris species are also provided.
Traditional species classification and identification based solely on shell morphology encounter significant challenges in freshwater mussels due to morphological variation and convergence. As a freshwater mussel genus endemic to China, Acuticosta (Bivalvia: Unionidae) has not been systematically revised due to the lack of molecular data. Moreover, the considerable phenotypic variation among individuals further complicates species taxonomy. This study conducted the most comprehensive sampling of Acuticosta to date in China, and the preliminary analyses challenged the monophyly of this genus. Integrating mitochondrial genomics, shell morphology, and soft-body anatomical evidence, we proposed a new genus, Pseudoacuticosta gen. nov., and supported the reclassification of three species originally belonging to Acuticosta: Pseudoacuticosta retiaria gen. & comb. nov., Inversidens trisulcata comb. nov., and Inversidens sichuanica comb. nov. Meanwhile, we identified various phenotypes that complicate species identification in Acuticosta chinensis and Acuticosta ovata, and provided updated DNA barcode data. This study highlights the potential utility of soft-tissue anatomical characteristics for genus-level classification within this taxonomic group. Furthermore, our findings underscore that integrative taxonomy, based on molecular phylogenetics, can effectively resolve issues arising from phenotypic variation and historical classification ambiguities.
This study investigates the osteometric differences between the Sardinian pine marten (Martes martes latinorum) and its continental counterpart (Martes martes martes), focusing on both cranial and postcranial skeletal elements. According to the island rule, small mammals on islands tend to increase in size. The Sardinian pine marten exhibits an increase in skull size (+12% in both sexes) compared to European subspecies, while its overall body mass shows a smaller increase (+9%). Analysis of the masticatory apparatus suggests hypertrophy of the temporalis and masseter muscles, reflected in a more robust zygomatic arch and a narrower postorbital constriction (-3.5% in males,-2.9% in females), suggesting a dietary shift toward increased meat consumption. The cranial capacity of Sardinian pine martens (22.85 cm(3) in males, 21.48 cm(3) in females) remains relatively large, possibly due to the cognitive demands associated with predation. Limb bones are longer in Sardinian females (+5.8%) but show negligible difference in males (< 1%) compared to the European subspecies. This study provides the first comprehensive osteological analysis of M. m. latinorum, demonstrating that the Sardinian marten population forms a distinct insular cluster, as also confirmed by genetic data. Historical and archeological evidence suggests that the Sardinian pine marten was introduced during the Neolithic (approximately 8,000 years ago). Therefore, the observed skeletal modifications, including the increased size of the skull, occurred in a relatively short evolutionary timescale.
The genus Diplocladon Gorham, 1883 (Coleoptera: Rhagophthalmidae) is a fascinating group of paedomorphic beetles, and holds potential as an ideal bioindicator for biodiversity conservation. Despite its ecological significance, the species diversity within this genus has remained poorly understood because of their cryptic habitats and challenges in species delimitations. In the present study, we integrate various methodological approaches including morphology, mitochondrial genome-based phylogeny and model-based species delimitations (bPTP, mPTP, GMYC, and BPP), as well as tests for gene flow (based on the genome-wide single nucleotide polymorphisms, or SNPs), to thoroughly elucidate the species diversity of Diplocladon, based on a total of 53 specimens of Diplocladon assembled predominantly by passive collecting methods (flight interception trap and Malaise trap) from southern China. As a result, a total of 13 species are recognized from China, including nine new species, D. nigripes sp. nov., D. robustum sp. nov., D. nanlingense sp. nov., D. leigongshanense sp. nov., D. dinghuense sp. nov., D. hainanense sp. nov., D. zhuhaiense sp. nov., D. lutianense sp. nov. and D. jiulianshanense sp. nov. Our findings significantly enrich the species diversity of Diplocladon, and highlight the necessity of employing passive collecting methods and integrative taxonomy to uncover species diversity among taxa occurring in a limited range and facing challenges in resolving morphological ambiguities presented by paedomorphic beetles like Diplocladon.
The Jarman-Bell principle is considered a general concept in ecology, stating that larger-bodied ungulates tend to eat lower-quality forage (i.e. less digestible graminoids), whereas smaller-bodied ungulates tend to eat higher-quality forage (i.e. highly digestible browse and herbaceous forbs). This contributes to dietary niche segregation among sympatric ungulates of different body sizes. However, it is unclear whether this concept applies to forest-dwelling ungulates in subtropical regions. Therefore, to determine the interspecific relationships regarding dietary niche among the sympatric sambars (largest body size), muntjacs (smallest body size), and Formosan serows (intermediate body size) in the subtropical montane cloud forest of Yushan National Park (Taiwan), we investigated their seasonal diet through microscopic analysis of feces. We found that the proportions of graminoids were higher in sambar feces than in muntjac and serow feces, supporting the Jarman-Bell principle. The proportions of dicot leaves were highest in serow feces, followed by muntjac and sambar feces, which deviated from the Jarman-Bell principle. This may have been caused by the tree-climbing behavior of serows, which allows them access to the abundant leaves of higher trees that sambar and muntjacs cannot access. To the best of our knowledge, our findings are the first to suggest that unique behavioral traits, such as tree climbing, cause unique dietary partitioning of ungulates in subtropical zones.
A medium-sized canid from the late Early Pleistocene fissure-filling locality of Kaiafas (Peloponnesus, Greece) is described here for the first time. The specimen comprises a partial skull and an associated mandible. The canid is identified as Canis mosbachensis. Some of the key characters are the following: the frontal sinus is large, and expands caudally towards the frontoparietal suture, though it does not reach it. The nasal bones do not extend beyond the frontomaxillary suture. The principal cusp of the lower third premolar lies below the principal cusps of the lower second and fourth premolars. The ratio of lower carnassial (= first molar) talonid length to lower carnassial length is 27%. The mesial edge of the lower carnassial paraconid is inclined distally and is curved. There is a small accessory cuspid between the lower carnassial metaconid and the entoconid. The lower second molar protoconid is larger than the metaconid and the talonid is relatively small. The estimated body mass of the Kaiafas canid is approximately 17 to 18 kg. The results of this study support the southward extension of C. mosbachensis into the Mediterranean, reinforcing the species' wide geographic range.
Hydrothermal vents and other chemosynthetic ecosystems are island-like oases in the deep ocean where microbial primary production supports an unusually high biomass. The small lepetelloidean family Pyropeltidae, with its sole genus Pyropelta containing about 10 described species, specialises in these systems. In the northwestern Pacific two species have been named around Japan, but their ranges have remained uncertain as shells of Pyropelta are typically corroded and difficult to identify morphologically. Here, we collected Pyropelta from three vents and two seeps in the northwestern Pacific, and assess the distribution of each species using molecular barcoding of the mitochondrial cytochrome c oxidase subunit I (COI) gene. As a result, we greatly extend the known distribution ranges of the two known northwestern Pacific species P. yamato and P. ryukyuensis. A lineage found in the Off Hatsushima seep in Sagami Bay was genetically distinct from the two described species and is named as Pyropelta artemis sp. nov. This new species inhabits a variety of substrates including tubes of siboglinid polychaetes as well as snail and mussel shells, and is noteworthy in displaying a great variability in its shell form because the aperture is constricted by substrate morphology. Our findings show that pyropeltids can also `shape-shift' according to the substrate like many other limpet-formed gastropods, which excludes shell shape as a broadly useful taxonomic character in this family.
Next-generation sequencing (NGS) enables the use invertebrate-derived DNA (iDNA) metabarcoding to enhance wildlife survey efficiency and coverage. However, this approach remains relatively new in Malaysia, and a precise DNA marker suited for the tropical rainforest climate of Southeast Asia has yet to be established. Hematophagous (blood-feeding) leeches inhabit various ecosystems, including tropical rainforests, providing a promising pilot target. Here, we used three primer pairs targeting the cytochrome c oxidase (Col), and the 16S and 12S ribosomal DNA loci in over 300 individual leeches collected from forests in central Peninsular Malaysia. We obtained 95 amplicon sequence variants (ASvs) for Cm, 81 ASvs for 16S, and 46 ASvs for 12S. We identified 42 vertebrate species, including greater mousedeer (Tragulus napu), Sunda pangolin (Manis javanica), Asian elephant (Elephas maximus), red junglefowl (Gallus gallus), and Malayan field rat (Rattus tiomanicus). Additionally, several amphibian and reptile species were also detected, such as Blyth's river frog (Limnonectes blythii), field frog (Fejervarya limnocharis) and many-lined sun skink (Eutropis multifasciata). The 16S locus identified the highest number of species (28), followed by 12S (25 species) and Cm (19 species). Our findings thus support the use of these loci as a complementary suite of DNA markers to enhance wildlife monitoring. Although traditional methods such as camera trapping can detect a larger number of wildlife species, these are considerably more time-and labour-intensive compared to DNA metabarcoding. The application of iDNA metabarcoding is highly recommended as a complementary approach to traditional surveys, particularly in dense tropical forests, to improve wildlife inventory efforts.
The genus Diplocladon Gorham, 1883 (Coleoptera: Rhagophthalmidae) is a fascinating group of paedomorphic beetles, and holds potential as an ideal bioindicator for biodiversity conservation. Despite its ecological significance, the species diversity within this genus has remained poorly understood because of their cryptic habitats and challenges in species delimitations. In the present study, we integrate various methodological approaches including morphology, mitochondrial genome-based phylogeny and model-based species delimitations (bPTP, mPTP, GMYC, and BPP), as well as tests for gene flow (based on the genome-wide single nucleotide polymorphisms, or SNPs), to thoroughly elucidate the species diversity of Diplocladon, based on a total of 53 specimens of Diplocladon assembled predominantly by passive collecting methods (flight interception trap and Malaise trap) from southern China. As a result, a total of 13 species are recognized from China, including nine new species, D. nigripes sp. nov, D. robustum sp. nov, D. nanlingense sp. nov, D. leigongshanense sp. nov, D. dinghuense sp. nov, D. hainanense sp. nov, D. zhuhaiense sp. nov, D. lutianense sp. nov. and D. jiulianshanense sp. nov. Our findings significantly enrich the species diversity of Diplocladon, and highlight the necessity of employing passive collecting methods and integrative taxonomy to uncover species diversity among taxa occurring in a limited range and facing challenges in resolving morphological ambiguities presented by paedomorphic beetles like Diplocladon.
Exceeding half a thousand species worldwide, Cheilosia Meigen, 1822 is the largest genus of Syrphidae (hoverflies) in the Iberian Peninsula, which, in turn, is a biodiversity hotspot in Europe. Apart from its remarkable alpha diversity, Cheilosia includes many species with high levels of morphological variability, leading to a complex taxonomy. The rather-inconspicuous, small-sized Cheilosia mutabilis (Fallén, 1817) and Cheilosia urbana (Meigen, 1822) are a good example of this complexity and an integrated approach (morphology + DNA ) was here followed to assess their morphological variability in Iberian populations. After fieldwork in several Spanish localities and revision of entomological collections, 230+ specimens were examined of four taxa, including a species new to science with distinctive morphology. The new species originates mainly from Sierra Nevada (Granada, southern Spain) and is allied with C. urbana . A detailed new species description is provided with drawings of the male genitalia and an account of morphological variation. The morphological variability of C. mutabilis and C. urbana were assessed against molecular data. As a result, a list of variable characters for each species was produced. In addition, Cheilosia psilophthalma Becker, 1894 was reported for the first time from the Iberian Peninsula. DNA of all four taxa was studied based on the 5’ end of the cytochrome c oxydase subunit I gene ( COI-5 ’), with sequences produced from Iberian material of three species, to explore species concepts and phylogenetic relationships. This paper represents a substantial advance in the taxonomy and systematics of the variable C. mutabilis and C. urbana , but also prompts the need of further investigations in a wider geographic frame to explore the entire morphological and genetic variability of these species.
The vertebrate skull integrates vital functions such as feeding, brain protection and sensory perception, making it a key structure for studying morphological evolution. Using micro-computed tomography and geometric morphometrics, we examined skull shape variation in the salamander genus Triturus , focusing on five (sub)species within the recently revised T. marmoratus species group (marbled and pygmy newts). Results were compared with the sister T. cristatus species group (crested newts) which comprises eight species, including a recent diversification within T. carnifex documented by molecular data. The two groups, which diverged approximately 28 million years ago, take opposite positions over a shape gradient, from broad skulls with posteriorly positioned jaws to narrower, elongated skulls with more anteriorly positioned jaw articulations, respectively. Both groups exhibit comparable levels of morphological variation (disparity) in skull shape. In the T. cristatus species group, skull shape changes are paralleled by changes in axial morphology (with a vertebral count ranging from 13 to 17) whereas species of the T. marmoratus group have a uniform count of 12 trunk vertebrae. The subspecies Triturus m. marmoratus stands out from other taxa in its group in jaw articulation and pterygoid placement, and vomerine tooth row lengths – features that suggest functional differences in feeding mechanics or diet. Further research on the function morphology of feeding, feeding regimes and phenology of taxa may help to uncover drivers of morphological divergence.
Iceland is the westernmost stronghold of European flora and fauna in the North Atlantic and provides a model system for studying post-glacial colonisation. We conducted quantitative sampling of terrestrial gastropods at 97 natural sites in Iceland between 2016 and 2024, documenting 29 species. Local diversity ranged from zero to 14 species (10 excluding slugs), with an average of five species (four excluding slugs). Of the species recorded, Carychium tridentatum (Risso, 1826), Euconulus alderi (Gray, 1840), Vertigo lilljeborgi (Westerlund, 1871) and V. substriata (Jeffreys, 1833) are new to Iceland and all occur in minerotrophic fens along the south coast. Their distribution is highly localised, with C. tridentatum and V. lilljeborgi occurring at only one and two sites respectively. Their absence in similar habitats in the north, except for a single record of V. lilljeborgi , suggests a climate-driven limitation. Phylogenetic reconstruction and haplotype networks based on mitochondrial DNA confirm their European origin and are consistent with previously studied species. Genetic similarities between Icelandic populations and those from the British Isles and mainland Europe support the hypothesis of natural dispersal via migratory birds. Our results emphasise the role of climate and habitat heterogeneity in shaping the Icelandic gastropod fauna, while suggesting that most species arrived postglacially through passive dispersal mechanisms. This study expands the knowledge of Icelandic biodiversity and underscores the importance of wetlands as refugia for rare species in this extreme environment.
Detecting plankton community responses to a changing ocean environment requires knowledge of the diversity and distribution of species. Hyperiid amphipods are an important component of pelagic food webs as prey and as commensals and parasitoids of gelatinous zooplankton, but their species and genetic diversity remains incompletely known. Using mitochondrial cytochrome c oxidase subunit 1 ( CO1 ) gene sequences, we assessed the genetic diversity of hyperiids collected along a meridional transect from 39 °N to 45 °S in the Atlantic Ocean in order to evaluate the congruence of genetic clades with morphologically-identified species, examine phylogeographic patterns within broadly-distributed species, and to contribute vouchered DNA barcodes into the public domain. CO1 sequences were obtained from 273 specimens representing 63 morphologically-identified hyperiid species belonging to 34 genera and 16 families, including sequences from 26 species with no prior reports in publicly-available databases. We recovered substantial amounts of genetic variation within nine nominal species, which were composed of two to four clades with 11–36% average sequence divergence between clades (range 10–45%). These are probably distinct or unrecognized biological species, however, additional sampling of morphological and/or genomic diversity is necessary to confirm this. Additionally, we examined the geographic distribution of genetic variation within Lycaea pulex, Phronimopsis spinifera, Phrosina semilunata, Tryphana malmii , and Vibilia armata , all species with broad or disjunct distributions across the Atlantic Ocean. We found that these species are composed of lineages with apparent geographic specializations to tropical, subtropical or temperate waters, suggesting more restricted biogeographic distributions than described for the inclusive morphospecies. This new collection of CO1 barcodes furthers our understanding of the diversity and distribution of hyperiids in the Atlantic Ocean and will support future research on this ecologically significant plankton group.
