The phylogenetics of Desmognathine salamander populations across the southern Appalachians

Salamanders in the genus Desmognathus (Caudata: Plethodontidae) are distributed along an aquatic to terrestrial habitat gradient in the southern Appalachian Mountains. The spatial distribution of species is believed to have formed as aquatic ancestors displaced lineages by competition and predatory interactions into less optimal terrestrial habitats. Aquatic and terrestrial species may also display different patterns of genetic diversity due to the differing likelihood of gene flow via aquatic corridors. To determine whether phylogenetic patterns were consistent with these hypotheses, we sequenced portions of the cytochrome oxidase I and 12S rRNA genes of the mitochondrial genome from 96 individuals belonging to 10 species in the genus Desmognathus. In addition, we combined our dataset with an earlier published dataset for the 12S rRNA genes. The order of species divergence is consistent with aquatic ancestors having displaced taxa into more terrestrial habitats, but the major lineages within the genus Desmognathus arose suddenly, and therefore, the specific sequence of events is not well resolved. The phylogenetic analyses among species suggest that direct-development and a terrestrial lifestyle are ancestral in the genus Desmognathus, but the degree of adult terrestriallity is labile, with some species having re-invaded terrestrial habitats. We present evidence of a clade of Desmognathus quadramaculatus from North Carolina that is distinct from the D. quadramaculatus/Desmognathus marmoratus clade. Within species, estimates of Tajima's D and Fu and Li's statistics suggest the species experienced population expansions at different times in the past. Current levels of sequence diversity in northern populations, therefore, reflect different arrival times, and hence, differences in the opportunity for among population divergence. The recent arrival of most species over large portions of their geographic ranges suggests that most extant communities have been assembled, a posteriori, by the recent assortment of species along the aquatic to terrestrial gradient according to their ecologies.     

Azospirillum genomes reveal transition of bacteria from aquatic to terrestrial environments

Fossil records indicate that life appeared in marine environments ～3.5 billion years ago (Gyr) and transitioned to terrestrial ecosystems nearly 2.5 Gyr. Sequence analysis suggests that "hydrobacteria" and "terrabacteria" might have diverged as early as 3 Gyr. Bacteria of the genus Azospirillum are associated with roots of terrestrial plants; however, virtually all their close relatives are aquatic. We obtained genome sequences of two Azospirillum species and analyzed their gene origins. While most Azospirillum house-keeping genes have orthologs in its close aquatic relatives, this lineage has obtained nearly half of its genome from terrestrial organisms. The majority of genes encoding functions critical for association with plants are among horizontally transferred genes. Our results show that transition of some aquatic bacteria to terrestrial habitats occurred much later than the suggested initial divergence of hydro- and terrabacterial clades. The birth of the genus Azospirillum approximately coincided with the emergence of vascular plants on land.     

The ontogeny of the olfactory system in ceratophryid frogs (Anura,Ceratophryidae)

The aquatic‐to‐terrestrial shift in the life cycle of most anurans suggests that the differences between the larval and adult morphology of the nose are required for sensory function in two media with different physical characteristics. However, a better controlled test of specialization to medium is to compare adult stages of terrestrial frogs with those that remain fully aquatic as adults. The Ceratophryidae is a monophyletic group of neotropical frogs whose diversification from a common terrestrial ancestor gave rise to both terrestrial (Ceratophrys, Chacophrys) and aquatic (Lepidobatrachus) adults. So, ceratophryids represent an excellent model to analyze the morphology and possible changes related to a secondary aquatic life. We describe the histomorphology of the nose during the ontogeny of the Ceratophryidae, paying particular attention to the condition in adult stages of the recessus olfactorius (a small area of olfactory epithelium that appears to be used for aquatic olfaction) and the eminentia olfactoria (a raised ridge on the floor of the principal cavity correlated with terrestrial olfaction). The species examined (Ceratophrys cranwelli, Chacophrys pierottii, Lepidobatrachus laevis, and L. llanensis) share a common larval olfactory organ composed by the principal cavity, the vomeronasal organ and the lateral appendix. At postmetamorphic stages, ceratophryids present a common morphology of the nose with the principal, middle, and inferior cavities with characteristics similar to other neobatrachians at the end of metamorphosis. However, in advanced adult stages, Lepidobatrachus laevis presents a recessus olfactorius with a heightened (peramorphic) development and a rudimentary (paedomorphic) eminentia olfactoria. Thus, the adult nose in Lepidobatrachus laevis arises from a common developmental ‘terrestrial’ pathway up to postmetamorphic stages, when its ontogeny leads to a distinctive morphology related to the evolutionarily derived, secondarily aquatic life of adults of this lineage.     

Benthic moss pillars in Antarctic lakes

Unique pillar-like colonies of aquatic mosses, rising from cyanobacterial and algal mats, have been discovered in some freshwater lakes in the vicinity of Syowa Station (69°00′S, 39°35′E), continental Antarctica. These moss pillars are about 40 cm in diameter and up to 60 cm high and occur at the lake bottoms mainly between 3 and 5 m depth. The primary component is a species of Leptobryum, a genus unknown in the continental Antarctic terrestrial bryoflora and as an aquatic genus elsewhere in the world. Bryum pseudotriquetrum is often an associated species. In longitudinal section the pillars reveal several whitish layers formed by mineral sediment and dead cyanobacteria. It is speculated that the biomass of aquatic mosses at the bottom of many Antarctic lakes is considerably greater than that previously estimated. Accepted: 11 April 1999     

Molecular phylogenetic analysis of the genus Strongyloides and related nematodes

Strongyloides spp., parasitic nematodes of humans and many other terrestrial vertebrates, display an unusual heterogonic lifecycle involving alternating parasitic and free-living adult reproductive stages. A number of other genera have similar lifecycles, but their relationships to Strongyloides have not been clarified. We have inferred a phylogeny of 12 species of Strongyloides, Parastrongyloides, Rhabdias and Rhabditophanes using small subunit ribosomal RNA gene (SSU rDNA) sequences. The lineage leading to Strongyloides appears to have arisen within parasites of terrestrial invertebrates. Inferred lifecycle evolution was particularly dynamic within these nematodes. Importantly, the free-living Rhabditophanes sp. KR3021 is placed within a clade of parasitic taxa, suggesting that this species may represent a reversion to a non-parasitic lifecycle. Species within the genus Strongyloides are very closely related, despite the disparity of host species parasitised. The highly pathogenic human parasite Strongyloides fuelleborni kelleyi is not supported as a subspecies of the primate parasite S. fuelleborni fuelleborni, but is most likely derived from a local zoonotic source.     

Widespread and persistent invasions of terrestrial habitats coincident with larval feeding behavior transitions during snail-killing fly evolution (Diptera: Sciomyzidae)

ABSTRACT: BACKGROUND: Transitions in habitats and feeding behaviors were fundamental to the diversification of life on Earth. There is ongoing debate regarding the typical directionality of transitions between aquatic and terrestrial habitats and the mechanisms responsible for the preponderance of terrestrial to aquatic transitions. Snail-killing flies (Diptera: Sciomyzidae) represent an excellent model system to study such transitions because their larvae display a range of feeding behaviors, being predators, parasitoids or saprophages of a variety of mollusks in freshwater, shoreline and dry terrestrial habitats. The remarkable genus Tetanocera (Tetanocerini) occupies five larval feeding groups and all of the habitat types mentioned above. This study has four principal objectives: (i) construct a robust estimate of phylogeny for Tetanocera and Tetanocerini, (ii) estimate the evolutionary transitions in larval feeding behaviors and habitats, (iii) test the monophyly of feeding groups and (iv) identify mechanisms underlying sciomyzid habitat and feeding behavior evolution. RESULTS: Bayesian inference and maximum likelihood analyses of molecular data provided strong support that the Sciomyzini, Tetanocerini and Tetanocera are monophyletic. However, the monophyly of many behavioral groupings was rejected via phylogenetic constraint analyses. We determined that (i) the ancestral sciomyzid lineage was terrestrial, (ii) there was a single terrestrial to aquatic habitat transition early in the evolution of the Tetanocerini and (iii) there were at least 10 independent aquatic to terrestrial habitat transitions and at least 15 feeding behavior transitions during tetanocerine phylogenesis. The ancestor of Tetanocera was aquatic with five lineages making independent transitions to terrestrial habitats and seven making independent transitions in feeding behaviors. CONCLUSIONS: The preponderance of aquatic to terrestrial transitions in sciomyzids goes against the trend generally observed across eukaryotes. Damp shoreline habitats are likely transitional where larvae can change habitat but still have similar prey available. Transitioning from aquatic to terrestrial habitats is likely easier than the reverse for sciomyzids because morphological characters associated with air-breathing while under the water's surface are lost rather than gained, and sciomyzids originated and diversified during a general drying period in Earth's history. Our results imply that any animal lineage having aquatic and terrestrial members, respiring the same way in both habitats and having the same type of food available in both habitats could show a similar pattern of multiple independent habitat transitions coincident with changes in behavioral and morphological traits.     

Morphological integration and ontogenetic niche shift: a study of crested newt limbs

This study deals with the ontogenetic and evolutionary aspects of integration patterns in the limbs of crested newt species, which, like most amphibians, have a biphasic life history with two morphologically distinct stages (larval vs. juvenile and adult) that occupy different environments (aquatic vs. terrestrial). We analyzed the structure and pattern of correlation between limb skeletal elements at three ontogenetic stages (larval, juvenile, and adult) of four closely related species that differ in their preferences of aquatic habitats (more terrestrial and more aquatic). We found dynamic changes in the pattern of morphological integration between successive ontogenetic stages, as well as changes over the course of crested newt phylogeny. Generally, equivalent ontogenetic stages of different species of crested newts show higher concordance in the correlation pattern than successive ontogenetic stages within species. Among species, two opposing correlation patterns were observed: in more terrestrial species, homologous limb elements are less correlated and within-limb elements are more correlated; in aquatic species, the reverse pattern occurs. These results indicate that the function seems to be the covariance-generating factor, which has shaped the patterns of morphological integration of crested newt limbs.     

Biomechanics on the half shell: functional performance influences patterns of morphological variation in the emydid turtle carapace

This study uses the carapace of emydid turtles to address hypothesized differences between terrestrial and aquatic species. Geometric morphometrics are used to quantify shell shape, and performance is estimated for two shell functions: shell strength and hydrodynamics. Aquatic turtle shells differ in shape from terrestrial turtle shells and are characterized by lower frontal areas and presumably lower drag. Terrestrial turtle shells are stronger than those of aquatic turtles; many-to-one mapping of morphology to function does not entirely mitigate a functional trade-off between mechanical strength and hydrodynamic performance. Furthermore, areas of morphospace characterized by exceptionally poor performance in either of the functions are not occupied by any emydid species. Though aquatic and terrestrial species show no significant differences in the rate of morphological evolution, aquatic species show a higher lineage density, indicative of a greater amount of convergence in their evolutionary history. The techniques employed in this study, including the modeling of theoretical shapes to assess performance in unoccupied areas of morphospace, suggest a framework for future studies of morphological variation.     

Evolutionary history of a secondary terrestrial Australian diving beetle (Coleoptera,Dytiscidae) reveals a lineage of high morphological and ecological plasticity

The evolution of a secondary terrestrial lifestyle in diving beetles (Coleoptera: Dytiscidae) has never been analysed in a phylogenetic framework before. Here we study Terradessus caecus Watts, a terrestrial species of the subfamily Hydroporinae endemic to Australia. We infer its phylogenetic placement using Bayesian inference and maximum‐likelihood methods based on a multilocus molecular dataset. We also investigate the divergence time estimates of this lineage using a Bayesian relaxed clock approach. Finally, we infer ancestral ecological preferences using a likelihood approach. We recover T. caecus nested in the genus Paroster Sharp with strong support. Therefore, we establish a synonymy for both species of Terradessus with Paroster: Paroster caecus (Watts) n.comb . and Paroster anophthalmus (Brancucci & Monteith) n.comb . Paroster is an endemic Australian genus that has a remarkable number of subterranean species in underground aquifers with highly derived morphologies. Our results highlight one of the most remarkable radiations of aquatic beetles with independent ecological pathways likely linked to palaeoclimatic disruptions in the Neogene. Paroster caecus (Watts) n.comb . originated from a mid‐Miocene split following the onset of an aridification episode that has been ongoing to the present day. The deep changes in ecological communities in association with the drying‐out of palaeodrainage systems might have pushed this lineage to colonize a new niche in terrestrial habitats.     

Aquatic adaptations in a Neotropical coral snake: A study of morphological convergence

Micrurus surinamensis is an aquatic member of the genus Micrurus. This species is known for its highly specialized venom and distinctive diet, mostly made of aquatic vertebrates. Here, we explore both external (head and body) and skull shape morphologies in M. surinamensis, comparing it with two terrestrial species of the genus (M. lemniscatus and M. spixii) and to aquatic and terrestrial species of distantly related groups. We use both traditional and geometric morphometrics to determine whether the presence of similar traits in head shape morphology is rather the result of adaptive convergences between M. surinamensis and other aquatic species, or whether it is the product of phylogenetic conservatism within the genus. Results from both traditional and geometric morphometrics show that M. surinamensis can be considered convergent with aquatic species, mainly in the skull shape. Micrurus surinamensis differs from the two terrestrial species of Micrurus by having a wider head, smaller distance between nostrils, and a long tail. Geometric morphometric analysis shows that despite having an extremely conserved skull and mandible shape, M. surinamensis shows a longer supratemporal and quadrate bones than in terrestrial Micrurus, indicating a larger gape for this species. A more kinetic skull combined with a larger gape would allow M. surinamensis to feed on fish, which represent larger and wider prey that contrast with the elongate prey, which compose the main diet of species in the genus Micrurus. Our results illustrate the importance of both phylogenetic conservatism and adaptation in shaping species morphology.     

Systematics and biology of the endemic water scavenger beetles of Hawaii (Coleoptera: Hydrophilidae, Hydrophilini)

Abstract.  Recent field surveys in the Hawaiian Islands have revealed an adaptive radiation of endemic water scavenger beetles (Coleoptera: Hydrophilidae). Phylogenetic analysis based on 55 adult morphological characters affirms that this endemic hydrophilid fauna is a monophyletic clade that incorporates the first well-supported transformation from an aquatic to terrestrial way of life within any lineage of the subfamily Hydrophilinae. The clade is prescribed to the genus Limnoxenus Motschulsky, where described members were previously placed. Five new species are described: L. waialeale sp.n. (Kauai), L. kauaiensis sp.n. (Kauai), L. oahuensis sp.n. (Oahu), L. punctatostriatus sp.n. (Kauai) and L. namolokama sp.n. (Kauai). Lectotypes are designated for the two previously described species L. semicylindricus (Eschscholtz) and L. nesiticus (Sharp). The Hawaiian lineage is a component of a larger clade that also includes the remaining four species of Limnoxenus from Europe, South Africa, and Australia, plus the monotypic genera Limnocyclus Balfour-Browne of New Caledonia and Hydramara Knisch of South America. The majority of the Hawaiian species exhibit vestigial wings, an extremely unusual condition in aquatic beetles. No other island-endemic members of the Hydrophilinae are known to be flightless, suggesting insularity per se is not responsible for this condition. L. nesiticus of Oahu has not been collected during the past 106 years, suggesting that it has been lost to anthropogenically mediated extinction.     

Trifoliellum bioblitzii, a new genus of trichomycete from mayfly nymphs in Nova Scotia, Canada

Trichomycetes are an ecological group of fungi and protists that colonize the gut lining of invertebrates in aquatic and moist terrestrial habitats. The diversity of this group appears to be high with many new species discovered each year. A new genus of fungal trichomycete, Trifoliellum (Harpellales), is described here with the type species T. bioblitzii. This genus is characterized by having unique, trefoil-shaped asexual spores (trichospores). Another new species, Legeriosimilis halifaxensis, also is described from the same mayfly host, Eurylophella temporalis, collected from the same site near Halifax, Nova Scotia.     

澜沧江两条支流捕食线虫真菌水陆分布差异及关联性

为探究微生物在流域中的水、陆分布差异和相互关系,对澜沧江两条支流捕食线虫真菌多样性水陆分布进行了调查研究。在枯水期,以澜沧江一级支流沘江和黑惠江为研究区域,系统布设12个采样点(水流交汇点),每个采样点采集水、陆对称样品各5份,共采集土样120份。结合传统分离纯化、形态学及分子生物学方法筛选和鉴定菌株,按照《Nematode-Trapping Fungi》进行分类,共获得2属13种88株捕食线虫真菌;其中,陆地样品中共分离到2属11种45株,水体底泥中分离出1属10种43株,检出率分别为41.67%和53.33%。结果表明,澜沧江两条支流捕食线虫真菌在物种、属、群落结构3个层面上均存在水陆差异,也相互联系;陆地土壤可能是流域内捕食线虫真菌多样性的源,水流是其重要的传播因子。在流域生态系统内,水陆间的扩散限制和水流的连通性都是维持微生物物种多样性的重要机制。     

Morphology and biology of the flower‐visiting water scavenger beetle genus Rygmodus (Coleoptera: Hydrophilidae)

Hydrophilidae (water scavenger beetles) is well known as an aquatic beetle family; however, it contains ca. 1,000 secondarily terrestrial species derived from aquatic ancestors. The New Zealand endemic genus Rygmodus White is a member of the hydrophilid subfamily Cylominae, which is the early‐diverging taxon of the largest terrestrial lineage (Cylominae + Sphaeridiinae) within the Hydrophilidae. In this paper we report that Rygmodus beetles are pollen‐feeding flower visitors as adults, but aquatic predators as larvae. Based on analyses of gut contents and a summary of collecting records reported on museum specimen labels, adult Rygmodus beetles are generalists feeding on pollen of at least 13 plant families. Rygmodus adult mouthparts differ from those of other (saprophagous) hydrophilid beetles in having the simple scoop‐like apex and mola with roughly denticulate surface, resembling the morphology found in pollen‐feeding staphylinid beetles. Larvae were found along the sides of streams, under stones and in algal mats and water‐soaked moss; one collected larval specimen was identified using DNA barcoding of two molecular markers, mitochondrial cytochrome oxidase 1 (cox1) and nuclear histone 3 (H3). Larvae of two species, Rygmodus modestus and Rygmodus sp., are described in detail and illustrated; they closely resemble ambush‐type predatory larvae of the hydrophilid tribe Hydrophilini in the head morphology. Rygmodus is the only known hydrophilid beetle with adults and larvae inhabiting different environments.     

Coevolution of the glucose dehydrogenase gene and the ejaculatory duct in the genus Drosophila

The glucose dehydrogenase gene (Gld) in Drosophila melanogaster exhibits a unique spatial and temporal pattern of expression. GLD expression switches from a non-sex-limited state at the pupal stage to a male-limited state at the adult stage. At the adult stage, the enzyme is restricted to the ejaculatory duct. Within the genus Drosophila, the ejaculatory duct has undergone a simple morphological divergence. In order to determine whether correlated changes in GLD expression had occurred, GLD activity during the pupal and adult stages was determined for several Drosophila species. It was found that virtually all of the species exhibit pupal GLD activity, whereas only those species with an expanded ejaculatory duct express male-limited GLD. The results of interspecific genital imaginal disc transplantation experiments indicate that the expanded morphology and GLD expression do not require any species- or sex-specific diffusible factors. An apparent regulatory polymorphism exists within the D. takahashii species with respect to male-limited GLD expression.      

Aquatic protostelids – a study from northeastern Germany

A survey of protostelids in ponds of northeastern Germany showed a high degree of similarity between the species assemblages from submerged aquatic and terrestrial litter. Twelve species were recovered from 115 samples. A statistical analysis of species accumulation curves indicated that 90 % of the total diversity was recovered for both aquatic and terrestrial litter. All of the more common species were observed in both aquatic and terrestrial samples. However, 24 % of all cultures from terrestrial samples were positive for protostelids, compared with only 12 % for aquatic samples. An additional 20 samples collected from the water column did not yield any protostelids. The study indicates that vegetative stages of most protostelids seem to be able to survive and probably multiply on litter submerged in fresh water, but do not live as plankton. Most probably, submerged substrata are sinks for protostelid populations.     

A combination of molecular and morphological approaches resolves species in the taxonomically difficult genus Procladius Skuse (Diptera: Chironomidae) despite high intra-specific morphological variation

Molecular approaches for identifying aquatic macroinvertebrate species are increasingly being used but there is ongoing debate about the number of DNA markers needed to differentiate species accurately. Here, we use two mitochondrial genes (cytochrome oxidase I, cytochrome b) and a nuclear gene (carbamoylphosphate synthetase) to differentiate species variation within the taxonomically challenging chironomid genus Procladius from southern Australia, a genus which is important for pollution monitoring. The mitochondrial genes indicated cryptic species that were subsequently linked to morphological variation at the larval and pupal stage. Two species previously described based on morphological criteria were linked to molecular markers, and there was evidence for additional cryptic species. Each genetic marker provided different information, highlighting the importance of considering multiple genes when dissecting taxonomically difficult groups, particularly those used in pollution monitoring.     

A molecular biological approach to the phylogenetic position of the genus Hyperamoeba

In 1923 Alexeieff described a new amoebic species within a new genus and named it Hyperamoeba flagellata. This amoeba exhibits three life cycle stages, an amoeboid trophozoite, a flagellated stage, and a cyst-like the heteroloboseans, the mastigamoebae, and several slime moulds. Since then more strains have been isolated and relationships to the protostelids and cercomonads and to the myxogastrid plasmodial slime moulds have been suggested. However, up to now the classification and phylogenetic position of the hyperamoebae has remained unclear. The aim of our study was to make an approach to the phylogeny of the genus Hyperamoeba with combined morphological and molecular biological data. Since 1988 we have isolated and collected Hyperamoeba-like strains from different aquatic and terrestrial sources. The 18S rDNA-sequences of 8 new Hyperamoeba strains isolated from various habitats were analysed and a cluster analysis was performed including all other available hyperamoebae. Altogether, the results of our study corroborate the relatedness of Hyperamoeba to various slime moulds. However, the hyperamoebae do not seem to be a monophyletic group, clearly putting the validity of the genus Hyperamoeba into question.     

Global diversity of oribatids (Oribatida: Acari: Arachnida)

Oribatid mites are primarily terrestrial. Only about 90 species (less than 1% of all known oribatid species) from 10 genera are truly aquatic, with reproduction and all stages of their life cycle living in freshwater. Adaptation to aquatic conditions evolved independently in different taxa. However, many terrestrial species can also be found in aquatic habitats, either as chance stragglers from the surrounding habitats, or from periodic or unpredictable floodings, where they can survive for long periods. In spite of their low species richness aquatic oribatids can be very abundant in different freshwater habitats as in lentic (pools, lakes, water-filled microhabitats) or flowing waters (springs, rivers, streams), mainly on submerged plants. The heavily sclerotized exoskeletons of several species enables subfossil or fossil preservation in lakes or bog sediments. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment