Martin Fikáček

Fungus-fungivore associations are central to forest ecosystem functioning where fungi mediate decomposition, provide shelter and nutrition for insects, whereas insects sporocarp-feeding and indirect spore dispersal in turn alter the fungal community assembly. Understanding fungus-fungivore associations based on meta-analysis is at the moment challenging because of unclear species taxonomy, difficulty in identifing samples based on historical descriptions, scarcity of genetic information, and over-simplified interaction records. Meta-analysis is also challenging because of different sampling strategies and definitions of biotic interaction. Here we propose a standardized workflow by integrating morphological identification, molecular data, and host records using a diverse lineage of Taiwanese fungivorous beetles (Erotylinae) as a model group. We found out that genetic divergence was not always accompanied by geographical isolation and morphological differences, i.e., many cryptic lineages. Most Erotylinae were generically monophagous. Further comparative phylogenetic analyses showed that multiple beetle species feed on the same fungal genus, which suggests repeated host shifts rather than co-diversification with the hosts. Our results demonstrate the importance of standardized procedures in studying species-species associations. For example, the interaction records that provide the host spectrum of a particular species can be used for testing the host specializations. Furthermore, the impacts of fungus diversity on beetle diversification can be examined.

Elmidae (riffle beetles) mostly inhabit running waters and are well known as ecological indicators. Originating in the Cretaceous, they are one of the most diverse water beetle families on all continents except Antarctica. Elmids exhibit two distinct adult ecomorphotypes, which have shaped higher classification: fully aquatic Elminae and amphibious Larainae. Recent phylogenetic analyses suggested these ecomorphotypes evolved convergently, but were based on relatively few taxa, largely from the Northern Hemisphere. Using an almost complete dataset for Austral Elmidae, and the most extensive for the family, we reveal at least five independent shifts between lifestyle in riffle beetles, including three in the Southern Hemisphere, these apparently being primarily from laraine to elmine ecomorphotype. One South African laraine lineage represents a new genus and species, Dracolara inexpectata gen et sp. nov., which is described here. Our findings highlight the morphological plasticity of riffle beetles and our limited knowledge of southern African freshwater biodiversity.

We present the most complete synthetic overview of the diversity of the order Coleoptera in Mexico to date. A list of all families known in Mexico is provided, as well as those likely distributed in Mexico but not yet officially recorded, including the number of described species recorded in the country for each. A summary of the state of knowledge for each family is included. Based on our data, Mexican beetles are represented by all four suborders, seven series, 24 superfamilies, and 129 families, plus eight families not yet recorded but probably distributed in the country based on their distribution in neighboring countries. Currently, 21,755 beetle species are recorded from Mexico.

Erichsonius (Sectophilonthus) huisunensis sp. nov. from Taiwan is described and photo-documented in detail, based on adult males, females, and larvae. It differs from other known Erichsonius species by its unusually brightly coloured elytra, but shows affinity to the Oriental group of winged, sparsely punctate smaller species with abdominal segments IV–V widest and with larger eyes. The species is common and widespread in the Central Mountain Range in Taiwan at altitudes 400–1800 m, where it inhabits forest floor and leaf litter. DNA barcodes are provided for the holotype and several paratypes. The late-instar larvae of the new species, associated with adults by DNA barcodes are also described and illustrated. A checklist of Erichsonius species occurring in the Oriental and East-Palaearctic regions, along with their type locality and distribution data, is also provided.

The immature stages of beetles (Coleoptera) remain poorly known, despite their importance for systematics, ecology, and applied research. To address this gap, the Immature Beetles Meeting (IBM) was established in Prague in 2007 and has since been held biennially. Over two decades, IBM has attracted a total of 455 visitors (206 individual participants) from 30 countries and hosted 168 presentations, creating an exclusive platform dedicated to beetle larvae and pupae. Here, we summarize the history, structure, and outcomes of IBM, highlighting its role in fostering collaboration, advancing methods, and promoting the study of beetle immatures within the global research community.

Flightless insects distributed on islands are often characterized by dynamic evolutionary patterns, high endemism, and complex biogeographic histories, imposing challenges for integrative systematics. In this study, we explore the evolutionary history and biogeography of moss‐inhabiting flea beetles from the genus Ivalia in the Taiwan‐Ryukyu archipelago. Using phylogenomic data from 1649 ddRAD‐sequenced nuclear loci with 50,461 single‐nucleotide polymorphisms, we uncovered a complex biogeographic history shaped by Late Miocene vicariance and subsequent Pliocene dispersal events from Taiwan. Our results suggest that Ivalia populations on Amamioshima and Taiwan originated through vicariance from a Miocene continental ancestor, whereas other Ryukyu populations represent more recent colonizations from Taiwan. Within Taiwan, we identify an extensive species radiation – the Ivalia uenoi complex – characterized by high species diversity and endemism. Within this complex, we found striking mitonuclear discordance, likely driven by repeated mitochondrial introgression. This discordance led to erroneous species delimitations based on mitochondrial DNA barcoding. In contrast, species delimitation based on nuclear markers was congruent with putative species assignments based on rough morphological examinations. Moreover, we found signs of nuclear introgression events in the ancient history of the Taiwanese Ivalia . Our findings highlight Ivalia as a compelling case of island radiation shaped by dynamic evolutionary processes and underscore the critical role of integrative taxonomic frameworks in insect systematics.

We provide a taxonomic description of the larva of the rove beetle Tolmerinus fratrumelliotorum Rougemont, 2017, identified through DNA barcoding. This is the first larval description for Anisolinina, the only subtribe whose sister group within the tribe Staphylinini remains unclear. While most phylogenetic hypotheses, especially molecular-based, suggest sister group relationships between Anisolinina and Staphylinina, conflicts remain, particularly when adult morphology is used for phylogeny reconstruction. Our attempt to use larval morphology for phylogeny reconstruction neither revealed a sister group for Anisolinina, nor unique synapomorphies for this subtribe. However, by mapping larval characters on the reference tree of Staphylinini, i.e., a phylogeny firmly established by phylogenomics in agreement with the adult morphology, we found unique larval synapomorphies to support the tribe Staphylinini and informal clade Staphylinini propria. We review all phylogenetic hypotheses ever proposed for a sister group of Anisolinina and discuss potential reasons for the poor phylogenetic signal in the larval characters alone. We stress some opportunities and challenges of using larval characters in phylogeny reconstructions.

The Asian-endemic genus Peltocercyon d'Orchymont, 1925 (Coleoptera: Hydrophilidae: Sphaeridiinae: Megasternini) is revised and redefined based on morphological characters and DNA data (five nuclear and three mitochondrial fragments). The metaventrite, with complete femoral lines crossing the arcuate ridges, is confirmed as the best diagnostic character for Peltocercyon in contrast to the morphology of the prosternum and mesoventrite which vary within the genus. DNA data reveal that Peltocercyon contains two separate lineages and that aedeagal morphology is more phylogenetically informative than external characters. A total of 17 species are recognized, of which nine are newly described: Peltocercyon basirugosus sp. nov. (China: Hainan, Yunnan; Laos: Bolikhamsai, Phongsaly Luang Prabang), P. carnarius sp. nov. (Indonesia: West Sumatra; Philippines: Mindanao; Malaysia: Sabah, Sarawak), P. kouwenkaii sp. nov. (China: Xizang), P. latifossus sp. nov. (Indonesia: Sumba), P. maculipennis sp. nov. (China: Taiwan, Sichuan, Chongqing, Guizhou and Guangxi; Laos: Houaphanh; Vietnam: Tam Dao; India: Arunachal Pradesh), P. medogensis sp. nov. (China: Xizang), P. rugosipennis sp. nov. (China: Xizang), P. splendidus sp. nov. (China: Xizang, Yunnan, Sichuan, Shaanxi, Hubei; India: Arunachal Pradesh), P. taylorae sp. nov. (China: Yunnan; Laos: Houaphanh, Phongsaly; India: Arunachal Pradesh). Three species are transferred to Peltocercyon from Cercyon Leach, 1817: Peltocercyon vagus (Sharp, 1884), comb. nov., P. vividus (d'Orchymont, 1925), comb. nov., and P. sanaii (Hoshina, 2008), comb. nov. Peltocercyon coomani d'Orchymont, 1925 is newly recorded from China, Laos, Thailand and Malaysia, P. lunulatus (Gemminger & Harold, 1868) from China, Laos, Malaysia, Cambodia and Myanmar, and P. vividus for Malaysia, Thailand and Indonesia. The closely related species P. maculipennis sp. nov., P. medogensis sp. nov., P. splendidus sp. nov. and P. taylorae sp. nov. are treated as the P. splendidus group. The Japanese and Far East species P. vagus (Sharp, 1884), P. subopacipennis (Nakane, 1965), P. sanaii (Hoshina, 2008), P. shigehisai Hoshina, 2018 and P. ohoni Hoshina, 2021 are treated as the P. vagus group, both groups being based on elytral sculpture, aedeagal morphology and distribution. Members of the P. vagus group are not treated taxonomically in detail due to limited material available. Diagnostic characters of all species and species groups are illustrated by photographs and SEM micrographs and an identification key and distribution maps of all species are provided. All known Peltocercyon inhabit decaying organic material; we provide the first hypothesis on the evolution of their habitat preferences.

Beetle superfamilies Histeroidea and Hydrophiloidea form a well‐supported monophylum with c. 9000 described species, but the relationships among the families remain unresolved, hindering the studies of the early evolution of the group. This study presents the first genomic data for all modern families, including the first genomes for Synteliidae, Sphaeritidae, Georissidae and Epimetopidae. Using datasets of 4215, 1100 and 709 protein‐coding genes, we reconstructed the relationships among the families, reconfirmed the Early Triassic split of Hydrophiloidea and Histeroidea, and revealed the Early to Middle Jurassic origin of modern families. All datasets and analytical methods revealed the same topology for Hydrophiloidea. The superfamily consists of two main clades: the helophorid lineage (Georissidae + Helophoridae + Hydrochidae) and the hydrophilid lineage (Epimetopidae + Spercheidae + Hydrophilidae), with Helophoridae + Hydrochidae and Spercheidae + Hydrophilidae as strongly supported clades; the riparian Georissidae and Epimetopidae form early branching clades in each lineage. In Histeroidea, we detected a significant conflict in phylogenetic signal, indicating a more complex and dynamic molecular evolution than in Hydrophiloidea: our analyses reject Synteliidae as sister to Histeridae but are not decisive on whether Synteliidae are sister to Sphaeritidae or to all other Histeroidea. The reconstruction of habitat preferences indicated that ancestral Hydrophiloidea inhabited moist substrates at the sides of lakes or rivers but were not aquatic. Aquatic habitats were colonized twice independently: once by Helophoridae + Hydrochidae and once by an ancestor of Spercheidae + Hydrophilidae. We discuss the evidence for and against this novel Riparian Ancestor Hypothesis in detail.

We document two profoundly different specialized swimming modes in two ancient lineages of water scavenger beetles (Hydrophilidae): (i) the upside-down swimming using middle legs in the species-poor Amphiops and (ii) the dorsal-up swimming using middle and hind legs in the species-diverse lineage of all other actively swimming taxa, including Berosus analysed here. Both lineages share a unique modification of the mesofurca supporting the leg swimming movements, indicating a single origin of swimming. By behavioural experiments and biomechanical analyses, we reveal that the swimming of Amphiops is optimized for high manoeuvrability, whereas that of Berosus for speed and acceleration. Both swimming modes differ in the form of the meso- and metathoracic skeleton and leg musculature, excluding the possibility that one is derived from the other. Behavioural experiments indicate that both modes are adaptive morpho-functional peaks and that intermediate modes are suboptimal. This aligns with the phylogeny-based model comparison that indicates that both swimming modes have evolved from an ancestral swimming lost in modern beetles. The multi-method approach helps us to reconstruct ancient behaviour and identify trade-offs that shaped the evolution of lifestyles in Mesozoic aquatic beetles.