Clade age and diversification rate variation explain disparity in species richness among water scavenger beetle (Hydrophilidae) lineages

Role of climatic variability in shaping intraspecific variation of thermal tolerance in Mediterranean water beetles

The climatic variability hypothesis (CVH) predicts that organisms in more thermally variable environments have wider thermal breadths and higher thermal plasticity than those from more stable environments. However, due to evolutionary trade-offs, taxa with greater absolute thermal limits may have little plasticity of such limits (trade-off hypothesis). The CVH assumes that climatic variability is the ultimate driver of thermal tolerance variation across latitudinal and altitudinal gradients, but average temperature also varies along such gradients. We explored intraspecific variation of thermal tolerance in three typical Mediterranean saline water beetles (families Hydrophilidae and Dytiscidae). For each species, we compared two populations where the species coexist, with similar annual mean temperature but contrasting thermal variability (continental vs. coastal population). We estimated thermal limits of adults from each population, previously acclimated at 17, 20, or 25 °C. We found species-specific patterns but overall, our results agree with the CVH regarding thermal ranges, which were wider in the continental (more variable) population. In the two hydrophilid species, this came at the cost of losing plasticity of the upper thermal limit in this population, supporting the trade-off hypothesis, but not in the dytiscid one. Our results support the role of local adaptation to thermal variability and trade-offs between basal tolerance and physiological plasticity in shaping thermal tolerance in aquatic ectotherms, but also suggest that intraspecific variation of thermal tolerance does not fit a general pattern among aquatic insects. Overlooking such intraspecific variation could lead to inaccurate predictions of the vulnerability of aquatic insects to global warming.

Larval chaetotaxy and morphometry of Megasternini: Cercyon (Paracercyon) Seidlitz, Cryptopleurum Mulsant and Pelosoma Mulsant (Coleoptera: Hydrophilidae)

The chaetotaxy of the head capsule and head appendages of all the larval instars of Cercyon (Paracercyon) analis and the first and third instars of Cryptopleurum minutum and Pelosoma sp. is described and illustrated for the first time. Morphometric characters derived from the head capsule and mouthparts are also included, together with detailed illustrations of all characters. The morphology and chaetotaxy of these larvae are compared to that of other Megasternini with described larvae. The larval morphology of Megasternini has proven to be very similar, however we provided a group of chaetotaxic characters useful to separate genera. Most of the differences were found in the sensilla of the head capsule, maxilla, and labium, both in size and arrangement, while the chaetotaxy of the antennae and mandibles was strongly conserved.

Ecological Transitions and the Shape of the Decapod Tree of Life

Understanding the processes that shaped the distribution of species richness across the Tree of Life is a central macroevolutionary research agenda. Major ecological innovations, including transitions between habitats, may help to explain the striking asymmetries of diversity that are often observed between sister clades. Here, we test the impact of such transitions on speciation rates across decapod crustaceans, modelling diversification dynamics within a phylogenetic framework. Our results show that, while terrestrial lineages have higher speciation rates than either marine or freshwater lineages, there is no difference between mean speciation rates in marine and freshwater lineages across Decapoda. Partitioning our data by infraorder reveals that those clades with habitat heterogeneity have higher speciation rates in freshwater and terrestrial lineages, with freshwater rates up to 1.5 times faster than marine rates, and terrestrial rates approximately four times faster. This averaging out of marine and freshwater speciation rates results from the varying contributions of different clades to average speciation rates. However, with the exception of Caridea, we find no evidence for any causal relationship between habitat and speciation rate. Our results demonstrate that while statistical generalisations about ecological traits and evolutionary rates are valuable, there are many exceptions. Hence, while freshwater and terrestrial lineages typically speciate faster than their marine relatives, there are many atypically slow freshwater lineages and fast marine lineages across Decapoda. Future work on diversification patterns will benefit from the inclusion of fossil data, as well as additional ecological factors.

Ancient relicts or recent immigrants? Different dating strategies alter diversification scenarios of New Zealand aquatic beetles (Coleoptera: Hydrophilidae: Berosus)

Dated species-level phylogenies are crucial for understanding the origin and evolutionary history of modern faunas, yet difficult to obtain due to the frequent absence of suitable age calibrations at species level. Substitution rates of related or more inclusive clades are often used to overcome this limitation but the accuracy of this approach remains untested. We compared tree dating based on substitution rates with analyses implementing fossil data by direct node-dating and indirect root-age constraints for the New Zealand endemic Berosus water beetles (Coleoptera: Hydrophilidae). The analysis based solely on substitution rates indicated a Miocene colonization of New Zealand and Pleistocene origin of species. By contrast, all analyses that implemented fossil data resulted in significantly older age estimates, indicating an ancient early Cenozoic origin of the New Zealand clade, diversification of species during or after the Oligocene transgression and Miocene-Pliocene origin of within-species population structure. Rate-calibrated time trees were incongruent with recently published Coleoptera time trees, the fossil record of Berosus and the distribution of outgroup species. Strong variation of substitution rates among Coleoptera lineages, as well as among lineages within the family Hydrophilidae, was identified as the principal reason for low accuracy of rate-calibrated analyses, resulting in underestimated node ages in Berosus. We provide evidence that Oligocene to Pliocene events, rather than the Pleistocene Glacial cycles, played an essential role in the formation of the modern New Zealand insect fauna.

Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records

This study summarizes available data on karyotypes of water scavenger beetles (Coleoptera: Hydrophiloidea: Hydrophilidae), based on newly acquired data of 23 genera and 64 species. We combine these data with previously published data, which we review. In total, karyotypes are available for 33 genera and 95 species, covering all subfamilies and tribes. Available data indicate that most groups of the Hydrophilidae are diploid and sexually reproducing, with XY (♂) and XX (♀) sex chromosomes; the Y chromosome is always minute and does not recombine with X during meiosis. Exceptions are known in Anacaena, with parthenogenetic diploid or triploid populations in some species and sex chromosomes fused with autosomes in others. The diploid number of chromosomes is 2n = 18 in the subfamilies Acidocerinae, Chaetarthriinae, Enochrinae and Hydrophilinae. Variations are known in species of Anacaena and Berosus (both usually with 2n = 18) and in Hydrochara and Hydrophilus with an increased number of chromosomes (2n = 30). The number of chromosomes is increased in the subfamily Cylominae (2n = 24–30) and in all subclades of the subfamily Sphaeridiinae (2n = 22–32). We summarize protocols for obtaining chromosome slides used for this study and provide step-by-step guidelines to facilitate future cytogenetic studies.

The Acidocerinae (Coleoptera, Hydrophilidae): taxonomy, classification, and catalog of species

The cosmopolitan subfamily Acidocerinae (Coleoptera: Hydrophilidae) is one of the largest and most taxonomically challenging lineages of water scavenger beetles. Recent phylogenetic studies have substantially advanced our understanding of acidocerine relationships but also illuminated the twin challenges of poorly delineated generic concepts and a classification broadly incompatible with the phylogeny. Here, these two challenges are addressed by providing a comprehensive synthesis and taxonomic tools for the Acidocerinae, including (1) a brief history and the current state of acidocerine classification, (2) a review of acidocerine ecology and collection methods, (3) the current knowledge of larval and fossil acidocerines, (4) a morphological primer on characters of taxonomic and systematic importance within the lineage, (5) a key to the world genera of Acidocerinae, (6) diagnoses, habitus, and aedeagal images, distribution maps, and summary of knowledge for each of the 23 extant genera in the subfamily, and (7) a complete annotated taxonomic catalog including the published distributions, synonyms, and references for all described 541 acidocerine species recognized as of 1 April 2021. The following nomenclatural acts are proposed to bring the phylogeny and classification into alignment: Colossochares gen. nov. is established to accommodate two African species previously described as Helochares (s. str.); Novochares gen. nov. is newly established to accommodate 15 Neotropical species previously included in Helochares (s. str.); the remaining Helochares subgenera Helocharimorphus Kuwert syn. nov. and Hydrobaticus MacLeay syn. nov. are synonymized with Helochares Mulsant. Peltochares Régimbart sensu nov. is redefined to include eight Old World species previously included in Helochares (s. str.). A lectotype is designated for Peltochares conspicuus Régimbart, the type species of the genus. The taxonomic and morphological circumscription of Helochares sensu nov. is narrowed and redefined.

Cuticle Hydrocarbons Show Plastic Variation under Desiccation in Saline Aquatic Beetles

In the context of aridification in Mediterranean regions, desiccation resistance and physiological plasticity will be key traits for the persistence of aquatic insects exposed to increasing desiccation stress. Control of cuticular transpiration through changes in the quantity and composition of epicuticular hydrocarbons (CHCs) is one of the main mechanisms of desiccation resistance in insects, but it remains largely unexplored in aquatic ones. We studied acclimation responses to desiccation in adults of two endemic water beetles from distant lineages living in Mediterranean intermittent saline streams: Enochrus jesusarribasi (Hydrophilidae) and Nebrioporus baeticus (Dytiscidae). Cuticular water loss and CHC composition were measured in specimens exposed to a prior non-lethal desiccation stress, allowed to recover and exposed to a subsequent desiccation treatment. E. jesusarribasi showed a beneficial acclimation response to desiccation: pre-desiccated individuals reduced cuticular water loss rate in a subsequent exposure by increasing the relative abundance of cuticular methyl-branched compounds, longer chain alkanes and branched alkanes. In contrast, N. baeticus lacked acclimation capacity for controlling water loss and therefore may have a lower physiological capacity to cope with increasing aridity. These results are relevant to understanding biochemical adaptations to drought stress in inland waters in an evolutionary and ecological context.

Going underwater: multiple origins and functional morphology of piercing-sucking feeding and tracheal system adaptations in water scavenger beetle larvae (Coleoptera: Hydrophiloidea)

Larvae of water scavenger beetles (Coleoptera: Hydrophiloidea) are adapted to a wide variety of aquatic habitats, but little is known about functional and evolutionary aspects of these adaptations. We review the functional morphology and evolution of feeding strategies of larvae of the families Hydrophilidae and Epimetopidae based on a detailed scanning electron microscope (SEM) analysis, analysis of video records of feeding behaviour and observations of living larvae. There are two main types of feeding mechanisms: chewing and piercing-sucking. The character mapping using the latest phylogenetic hypothesis for Hydrophiloidea infers the chewing system as the ancestral condition. The piercing-sucking mechanism evolved at least four times independently: once in Epimetopidae (Epimetopus) and three times in Hydrophilidae (Berosini: Berosus + Hemiosus; Laccobiini: Laccobius group; Hydrobiusini: Hybogralius). The piercing-sucking apparatus allows underwater extra-oral digestion and decreases the dependence of larvae on an aerial environment. A detailed study of the tracheal morphology of the piercing-sucking lineages reveals four independent origins of the apneustic respiratory system, all of them nested within lineages with piercing-sucking mouthparts. We conclude that piercing-sucking mouthparts represent a key innovation, which allows for the subsequent adaptation of the tracheal system, influences the diversification dynamics of the lineages and allows the shift to new adaptive zones.

Machine learning approaches identify male body size as the most accurate predictor of species richness

BACKGROUND

A major challenge in biodiversity science is to understand the factors contributing to the variability of species richness -the number of different species in a community or region - among comparable taxonomic lineages. Multiple biotic and abiotic factors have been hypothesized to have an effect on species richness and have been used as its predictors, but identifying accurate predictors is not straightforward. Spiders are a highly diverse group, with some 48,000 species in 120 families; yet nearly 75% of all species are found within just the ten most speciose families. Here we use a Random Forest machine learning algorithm to test the predictive power of different variables hypothesized to affect species richness of spider genera.

RESULTS

We test the predictive power of 22 variables from spiders' morphological, genetic, geographic, ecological and behavioral landscapes on species richness of 45 genera selected to represent the phylogenetic and biological breath of Araneae. Among the variables, Random Forest analyses find body size (specifically, minimum male body size) to best predict species richness. Multiple Correspondence analysis confirms this outcome through a negative relationship between male body size and species richness. Multiple Correspondence analyses furthermore establish that geographic distribution of congeneric species is positively associated with genus diversity, and that genera from phylogenetically older lineages are species poorer. Of the spider-specific traits, neither the presence of ballooning behavior, nor sexual size dimorphism, can predict species richness.

CONCLUSIONS

We show that machine learning analyses can be used in deciphering the factors associated with diversity patterns. Since no spider-specific biology could predict species richness, but the biologically universal body size did, we believe these conclusions are worthy of broader biological testing. Future work on other groups of organisms will establish whether the detected associations of species richness with small body size and wide geographic ranges hold more broadly.

Animal bioturbation preserved in Pleistocene magadiite at Lake Magadi, Kenya Rift Valley, and its implications for the depositional environment of bedded magadiite

Magadiite, a rare hydrous sodium-silicate mineral [NaSi₇O₁₃(OH)₃·4(H₂O)], was discovered about 50 years ago in sediments around Lake Magadi, a hypersaline alkaline lake fed by hot springs in the semi-arid southern Kenya Rift Valley. Today this harsh lacustrine environment excludes most organisms except microbial extremophiles, a few invertebrates (mostly insects), highly adapted fish (Alcolapia sp.), and birds including flamingos. Burrows discovered in outcrops of the High Magadi Beds (~25–9 ka) that predate the modern saline (trona) pan show that beetles and other invertebrates inhabit this extreme environment when conditions become more favourable. Burrows (cm-scale) preserved in magadiite in the High Magadi Beds are filled with mud, silt and sand from overlying sediments. Their stratigraphic context reveals upward-shallowing cycles from mud to interlaminated mud-magadiite to magadiite in dm-scale units. The burrows were formed when the lake floor became fresher and oxygenated, after a period when magadiite precipitated in shallow saline waters. The burrows, probably produced by beetles, show that trace fossils can provide evidence for short-term (possibly years to decades) changes in the contemporary environment that might not otherwise be recognised or preserved physically or chemically in the sediment record.

Phylogeny, systematics and rarity assessment of New Zealand endemic Saphydrus beetles and related enigmatic larvae (Coleoptera : Hydrophilidae : Cylominae)

The New Zealand endemic beetle genus Saphydrus Sharp, 1884 (Coleoptera:Hydrophilidae:Cylominae) is studied in order to understand its phylogenetic position, species-level systematics, biology and distribution, and to reveal reasons for its rarity. The first complete genus-level phylogeny of Cylominae based on two mitochondrial (cox1, 16S) and two nuclear genes (18S, 28S) covering 18 of 19 genera of the subfamily reveals Saphydrus as an isolated lineage situated in a clade with Cylorygmus (South America), Relictorygmus (South Africa) and Eurygmus (Australia). DNA is used to associate two larval morphotypes with Saphydrus: one of them represents the larvae of S. suffusus Sharp, 1884; the other, characterised by unique characters of the head and prothorax morphology, is revealed as sister but not closely related to Saphydrus. It is described here as Enigmahydrus, gen. nov. with a single species, E. larvalis, sp. nov., whose adult stage remains unknown. Saphydrus includes five species, two of which (S. moeldnerae, sp. nov. and S. tanemahuta, sp. nov.) are described as new. Larvae of Enigmahydrus larvalis and Saphydrus suffusus are described and illustrated in detail based on DNA-identified specimens. Candidate larvae for Saphydrus obesus Sharp, 1884 and S. tanemahuta are illustrated and diagnosed. Specimen data are used to evaluate the range, altitudinal distribution, seasonality and population dynamics over time for all species. Strongly seasonal occurrence of adults combined with other factors (winter occurrence in S. obesus, occurrence at high altitudes in S. tanemahuta) is hypothesised as the primary reason of the rarity for Saphydrus species. By contrast, Enigmahydrus larvalis underwent a strong decline in population number and size since the 1970s and is currently known from a single, locally limited population; we propose the ‘nationally threatened’ status for this species. http://zoobank.org/urn:lsid:zoobank.org:pub:28D87163-29E8-418C-9380-262D3038023A

Clade-age-dependent diversification under high species turnover shapes species richness disparities among tropical rainforest lineages of Bulbophyllum (Orchidaceae)

Background

Tropical rainforests (TRFs) harbour almost half of the world’s vascular plant species diversity while covering only about 6–7% of land. However, why species richness varies amongst the Earth’s major TRF regions remains poorly understood. Here we investigate the evolutionary processes shaping continental species richness disparities of the pantropical, epiphytic and mostly TRF-dwelling orchid mega-genus Bulbophyllum (c. 1948 spp. in total) using diversification analyses based on a time-calibrated molecular phylogeny (including c. 45–50% spp. each from Madagascar, Africa, Neotropics, and 8.4% from the Asia-Pacific region), coupled with ecological niche modelling (ENM) of geographic distributions under present and past (Last Glacial Maximum; LGM) conditions.

Results

Our results suggest an early-to-late Miocene scenario of ‘out-of-Asia-Pacific’ origin and progressive, dispersal-mediated diversification in Madagascar, Africa and the Neotropics, respectively. Species richness disparities amongst these four TRF lineages are best explained by a time-for-speciation (i.e. clade age) effect rather than differences in net diversification or diversity-dependent diversification due to present or past spatial-bioclimatic limits. For each well-sampled lineage (Madagascar, Africa, Neotropics), we inferred high rates of speciation and extinction over time (i.e. high species turnover), yet with the origin of most extant species falling into the Quaternary. In contrast to predictions of classical ‘glacial refuge’ theories, all four lineages experienced dramatic range expansions during the LGM.

Conclusions

As the Madagascan, African and Neotropical lineages display constant-rate evolution since their origin (early-to-mid-Miocene), Quaternary environmental change might be a less important cause of their high species turnover than intrinsic features generally conferring rapid population turnover in tropical orchids (e.g., epiphytism, specialization on pollinators and mycorrhizal fungi, wind dispersal). Nonetheless, climate-induced range fluctuations during the Quaternary could still have played an influential role in the origination and extinction of Bulbophyllum species in those three, if not in all four TRF regions.

Electronic supplementary material

The online version of this article (10.1186/s12862-019-1416-1) contains supplementary material, which is available to authorized users.

Water Beetles as Models in Ecology and Evolution

Beetles have colonized water many times during their history, with some of these events involving extensive evolutionary radiations and multiple transitions between land and water. With over 13,000 described species, they are one of the most diverse macroinvertebrate groups in most nonmarine aquatic habitats and occur on all continents except Antarctica. A combination of wide geographical and ecological range and relatively accessible taxonomy makes these insects an excellent model system for addressing a variety of questions in ecology and evolution. Work on water beetles has recently made important contributions to fields as diverse as DNA taxonomy, macroecology, historical biogeography, sexual selection, and conservation biology, as well as predicting organismal responses to global change. Aquatic beetles have some of the best resolved phylogenies of any comparably diverse insect group, and this, coupled with recent advances in taxonomic and ecological knowledge, is likely to drive an expansion of studies in the future.

Systematics of Clupeiformes and testing for ecological limits on species richness in a trans-marine/freshwater clade

ABSTRACT Clupeiformes (herring, sardines, shad, anchovies and allies) are a globally distributed clade with nearly 400 marine, freshwater, and diadromous species. Although best known as filter feeding fishes that form large schools, this group occupies a diverse array of trophic guilds and habitats. Theory suggests that species richness in clades is modulated by ecological limits, which results in diversity-dependent clade growth, a pattern that most clades exhibit. As a trans-marine/freshwater clade that has undergone repeated transitions between marine and freshwaters, Clupeiformes are an excellent system for investigating the interplay between ecological diversity and macroevolutionary dynamics. In this study we review the systematics of Clupeiformes and explore discordance in phylogenetic relationships and divergence times between mitochondrial and nuclear loci. We then use comparative methods to test whether ecological limits regulate diversity in Clupeiformes. We find discordance in phylogenetic relationships at various taxonomic scales, but also considerable agreement between genomes. Our results suggest that trans-marine/freshwater clades are able to circumvent ecological limits on clade growth at regional, but not on local scales. Our study demonstrates that phylogenies are a critical link between ecology and macroevolutionary dynamics, and suggests habitat transitions can play a key role in shaping diversity patterns, particularly in the neotropics.

Tempo and rates of diversification in the South American cichlid genus Apistogramma (Teleostei: Perciformes: Cichlidae)

Evaluating biodiversity and understanding the processes involved in diversification are noticeable conservation issues in fishes subject to large, sometimes illegal, ornamental trade purposes. Here, the diversity and evolutionary history of the Neotropical dwarf cichlid genus Apistogramma from several South American countries are investigated. Mitochondrial and nuclear markers are used to infer phylogenetic relationships between 31 genetically identified species. The monophyly of Apistogramma is suggested, and Apistogramma species are distributed into four clades, corresponding to three morphological lineages. Divergence times estimated with the Yule process and an uncorrelated lognormal clock dated the Apistogramma origin to the beginning of the Eocene (≈ 50 Myr) suggesting that diversification might be related to marine incursions. Our molecular dating also suggests that the Quaternary glacial cycles coincide with the phases leading to Apistogramma speciation. These past events did not influence diversification rates in the speciose genus Apistogramma, since diversification appeared low and constant through time. Further characterization of processes involved in recent Apistogramma diversity will be necessary.

Disentangling geographical, biotic, and abiotic drivers of plant diversity in neotropical Ruellia (Acanthaceae)

It has long been hypothesized that biotic interactions are important drivers of biodiversity evolution, yet such interactions have been relatively less studied than abiotic factors owing to the inherent complexity in and the number of types of such interactions. Amongst the most prominent of biotic interactions worldwide are those between plants and pollinators. In the Neotropics, the most biodiverse region on Earth, hummingbird and bee pollination have contributed substantially to plant fitness. Using comparative methods, we test the macroevolutionary consequences of bird and bee pollination within a species rich lineage of flowering plants: Ruellia. We additionally explore impacts of species occupancy of ever-wet rainforests vs. dry ecosystems including cerrado and seasonally dry tropical forests. We compared outcomes based on two different methods of model selection: a traditional approach that utilizes a series of transitive likelihood ratio tests as well as a weighted model averaging approach. Analyses yield evidence for increased net diversification rates among Neotropical Ruellia (compared to Paleotropical lineages) as well as among hummingbird-adapted species. In contrast, we recovered no evidence of higher diversification rates among either bee- or non-bee-adapted lineages and no evidence for higher rates among wet or dry habitat lineages. Understanding fully the factors that have contributed to biases in biodiversity across the planet will ultimately depend upon incorporating knowledge of biotic interactions as well as connecting microevolutionary processes to macroevolutionary patterns.

A major shift in diversification rate helps explain macroevolutionary patterns in primate species diversity

Primates represent one of the most species rich, wide ranging, and ecologically diverse clades of mammals. What major macroevolutionary factors have driven their diversification and contributed to the modern distribution of primate species remains widely debated. We employed phylogenetic comparative methods to examine the role of clade age and evolutionary rate heterogeneity in the modern distribution of species diversity of Primates. Primate diversification has accelerated since its origin, with decreased extinction leading to a shift to even higher evolutionary rates in the most species rich family (Cercopithecidae). Older primate clades tended to be more diverse, however a shift in evolutionary rate was necessary to adequately explain the imbalance in species diversity. Species richness was also poorly explained by geographic distribution, especially once clade age and evolutionary rate shifts were accounted for, and may relate instead to other ecological factors. The global distribution of primate species diversity appears to have been strongly impacted by heterogeneity in evolutionary rates.

Is the switch to an ectomycorrhizal state an evolutionary key innovation in mushroom-forming fungi? A case study in the Tricholomatineae (Agaricales)

Although fungi are one of the most diverse groups of organisms, little is known about the processes that shape their high taxonomic diversity. This study focuses on evolution of ectomycorrhizal (ECM) mushroom-forming fungi, symbiotic associates of many trees and shrubs, in the suborder Tricholomatineae of the Agaricales. We used the BiSSE model and BAMM to test the hypothesis that the ECM habit represents an evolutionary key innovation that allowed the colonization of new niches followed by an increase in diversification rate. Ancestral state reconstruction (ASR) supports the ancestor of the Tricholomatineae as non-ECM. We detected two diversification rate increases in the genus Tricholoma and the Rhodopolioid clade of the genus Entoloma. However, no increases in diversification were detected in the four other ECM clades of Tricholomatineae. We suggest that diversification of Tricholoma was not only due to the evolution of the ECM lifestyle, but also to the expansion and dominance of its main hosts and ability to associate with a variety of hosts. Diversification in the Rhodopolioid clade could be due to the unique combination of spore morphology and ECM habit. The spore morphology may represent an exaptation that aided spore dispersal and colonization. This is the first study to investigate rate shifts across a phylogeny that contains both non-ECM and ECM lineages.

New records of Helophoridae, Hydrochidae, and Hydrophilidae (Coleoptera) from New Brunswick, Canada

The following three species of Helophoridae are newly recorded for New Brunswick, Canada: Helophorus (Kyphohelophorus) turberculatus Gyllenhal, Helophorus (Rhopaleloporus) oblongus LeConte, Helophorus (Rhopaleloporus) marginicollis Smetana. Hydrochussubcupreus Randall, family Hydrochidae, and the following 15 species of Hydrophilidae are newly reported for the province: Berosusfraternus LeConte, Berosusperegrinus (Herbst), Berosussayi Hansen, Paracymusdespectus (LeConte), Chaetarthriaatra (LeConte), Cymbiodytaacuminata Fall, Cymbiodytablanchardi Horn, Cymbiodytaminima Notman, Enochrus (Lumetus) hamiltoni Horn, Enochrus (Methydrus) consors (LeConte), Enochrus (Methydrus) consortus Green, Enochrus (Methydrus) pygmaeusnebulosus (Say), Cercyon (Cercyon) cinctus Smetana, Cercyon (Cercyon) herceusfrigidus Smetana, Cercyon (Dicyrtocercyon) ustulatus (Preyssler).

Protosternini (Coleoptera : Hydrophilidae) corroborated as monophyletic and its larva described for the first time: a review of the myrmecophilous genus Sphaerocetum

The genus Sphaerocetum Fikáček, 2010 is reviewed on the basis of specimens collected from mixed ant nests shared by Camponotus Mayr, 1861 and Crematogaster Lund, 1831 ants in Peninsular Malaysia. Two new species, S. arboreum, sp. nov. and S. hortulanum, sp. nov., are described. A larva of S. arboreum was collected in the same nest as the adults, implying that it is likely that the entire life cycle takes place inside the ant nest; its association with adults was confirmed by cox1 sequences. It is described in detail and represents the first known larva of the tribe Protosternini. Fragments of four genes (cox1, cox2, 18S and 28S) were amplified for S. arboreum and combined with previously generated data in order to test the position of the genus within the subfamily Sphaeridiinae. The analyses revealed Sphaerocetum as a sister taxon to Protosternum Sharp, 1890, corroborating the monophyly of the tribe Protosternini. Bayesian analysis revealed an alternative hypothesis of the phylogenetic position of the tribe, indicating that Protosternini is a sister-group to Omicrini. This position is supported by the chaetotaxy of the maxillary stipes of the larva, which lacks the increased number of stout setae on the inner face present in all other Sphaeridiinae larvae except Omicrini.