Cryptic diversity and multiple origins of the widespread mayfly species group Baetis rhodani (Ephemeroptera: Baetidae) on northwestern Mediterranean islands.
ABSTRACT: How the often highly endemic biodiversity of islands originated has been debated for decades, and it remains a fervid research ground. Here, using mitochondrial and nuclear gene sequence analyses, we investigate the diversity, phylogenetic relationships, and evolutionary history of the mayfly Baetis gr. rhodani on the three largest northwestern Mediterranean islands (Sardinia, Corsica, Elba). We identify three distinct, largely co-distributed, and deeply differentiated lineages, with divergences tentatively dated back to the Eocene-Oligocene transition. Bayesian population structure analyses reveal a lack of gene exchange between them, even at sites where they are syntopic, indicating that these lineages belong to three putative species. Their phylogenetic relationships with continental relatives, together with the dating estimates, support a role for three processes contributing to this diversity: (1) vicariance, primed by microplate disjunction and oceanic transgression; (2) dispersal from the continent; and (3) speciation within the island group. Thus, our results do not point toward a prevailing role for any of the previously invoked processes. Rather, they suggest that a variety of processes equally contributed to shape the diverse and endemic biota of this group of islands.
Project description:A detailed description of the larvae of Baetis (Baetis) cypronyx <b>sp. n.</b>, a representative of the <i>Baetis alpinus</i> species-group within the mayfly family Baetidae, is provided, including a differential diagnosis with regard to closely related species of the group, especially <i>Baetis melanonyx</i> (Pictet, 1843) and <i>Baetis baroukianus</i> Thomas & Dia, 1984. The new species is mainly distinguished by mouthparts (i.e. the shape and setation of labrum, maxillary and labial palps, details of paraglossae and mandibular incisors), setation of legs and abdominal terga, and length of paracercus. All available data on the biology of this putative endemic species of Cyprus are summarized. Annotated distributional data of the 33 species of Baetidae so far recorded from the Mediterranean islands are given, including new records and also including first data from Malta.
Project description:The taxonomy and systematics of the genus <i>Baetis</i> Leach (Ephemeroptera: Baetidae) in Israel is clarified for the first time as part of an ongoing comprehensive survey of the Israeli mayfly fauna. Six clearly defined species are currently recognized in Israel, four of which are described here as new to science. The validity of all species is supported by a molecular analysis of the mitochondrial COI gene. A key for the identification of the Israeli species based on the nymphal stage is provided, as well as data on their distribution patterns and ecology. The local fauna represents four Palearctic species groups, three of which reach their limit of distribution range in Israel. <i>Baetis</i> species typically inhabit lotic, pristine habitats in northern Israel, with few exceptions for some species that can be found in the Dead Sea area or in ephemeral ponds.
Project description:OBJECTIVE:Species of the Baetis rhodani group are among the most widespread mayflies of the Palearctic region. However, frequent occurrence of morphologically cryptic species complicates the identification of sympatric species. Here, we proposed and tested a method for the fast, accurate, and cost-effective assignment of a large number of individuals to their putative species, based on high resolution melting profiles of a standard mitochondrial gene fragment. We tested this method using a system of three recently identified cryptic species inhabiting the Tyrrhenian Islands (western Mediterranean basin). RESULTS:Highly species-specific high resolution melting profiles were obtained, allowing the unequivocal attribution of each individual to the respective species. This assay provides a convenient and easily customizable alternative to traditional barcoding approaches, provided that the mayfly taxa occurring within the geographic area of interest have been previously identified and their high resolution melting profiles assessed.
Project description:Background:The Mediterranean basin is known to be the cradle of many endemic species. Within mayflies (Insecta, Ephemeroptera), North African species belonging to the family Baetidae remain poorly known and, traditionally, affinities to European fauna were proposed. Recent studies, based on molecular reconstructions, showed closer relationships to Mediterranean islands fauna. New information:Baetidae were sampled from North-West Algerian wadis (Tafna basin) and involved in COI barcoding reconstructions. Seven species were identified. The subgenus Rhodobaetis is represented by Baetis atlanticus known previously from Macaronesian islands, Europe and Morocco and the Maghrebian endemic Baetis sinespinosus. Specimens, previously identified as Cloeon cf. dipterum, correspond to Cloeon peregrinator and, until now, only reported from Macaronesia. Besides the confirmation of endemicity of some species, such as Procloen stagnicola and B. sinespinosus, our molecular study showed quite original results for relationships between European, insular and Algerian species. Baetis maurus stood out as a North African endemic sister clade to an Iberian clade. Furthermore, we found clear interspecific distances between Algerian and European clades for A. cf. sinaica and B. cf. pavidus, suggesting the presence of cryptic species in Algeria. However, additional studies are needed, as, for the moment, no clear morphological characters were found to separate the different clades and support them as valid species.
Project description:BACKGROUND:Many species contain evolutionarily distinct groups that are genetically highly differentiated but morphologically difficult to distinguish (i.e., cryptic species). The presence of cryptic species poses significant challenges for the accurate assessment of biodiversity and, if unrecognized, may lead to erroneous inferences in many fields of biological research and conservation. RESULTS:We tested for cryptic genetic variation within the broadly distributed alpine mayfly Baetis alpinus across several major European drainages in the central Alps. Bayesian clustering and multivariate analyses of nuclear microsatellite loci, combined with phylogenetic analyses of mitochondrial DNA, were used to assess population genetic structure and diversity. We identified two genetically highly differentiated lineages (A and B) that had no obvious differences in regional distribution patterns, and occurred in local sympatry. Furthermore, the two lineages differed in relative abundance, overall levels of genetic diversity as well as patterns of population structure: lineage A was abundant, widely distributed and had a higher level of genetic variation, whereas lineage B was less abundant, more prevalent in spring-fed tributaries than glacier-fed streams and restricted to high elevations. Subsequent morphological analyses revealed that traits previously acknowledged as intraspecific variation of B. alpinus in fact segregated these two lineages. CONCLUSIONS:Taken together, our findings indicate that even common and apparently ecologically well-studied species may consist of reproductively isolated units, with distinct evolutionary histories and likely different ecology and evolutionary potential. These findings emphasize the need to investigate hidden diversity even in well-known species to allow for appropriate assessment of biological diversity and conservation measures.
Project description:BACKGROUND:Baetis harrisoni Barnard is a mayfly frequently encountered in river studies across Africa, but the external morphological features used for identifying nymphs have been observed to vary subtly between different geographic locations. It has been associated with a wide range of ecological conditions, including pH extremes of pH 2.9-10.0 in polluted waters. We present a molecular study of the genetic variation within B. harrisoni across 21 rivers in its distribution range in southern Africa. RESULTS:Four gene regions were examined, two mitochondrial (cytochrome c oxidase subunit I [COI] and small subunit ribosomal 16S rDNA [16S]) and two nuclear (elongation factor 1 alpha [EF1?] and phosphoenolpyruvate carboxykinase [PEPCK]). Bayesian and parsimony approaches to phylogeny reconstruction resulted in five well-supported major lineages, which were confirmed using a general mixed Yule-coalescent (GMYC) model. Results from the EF1? gene were significantly incongruent with both mitochondrial and nuclear (PEPCK) results, possibly due to incomplete lineage sorting of the EF1? gene. Mean between-clade distance estimated using the COI and PEPCK data was found to be an order of magnitude greater than the within-clade distance and comparable to that previously reported for other recognised Baetis species. Analysis of the Isolation by Distance (IBD) between all samples showed a small but significant effect of IBD. Within each lineage the contribution of IBD was minimal. Tentative dating analyses using an uncorrelated log-normal relaxed clock and two published estimates of COI mutation rates suggest that diversification within the group occurred throughout the Pliocene and mid-Miocene (~2.4-11.5 mya). CONCLUSIONS:The distinct lineages of B. harrisoni correspond to categorical environmental variation, with two lineages comprising samples from streams that flow through acidic Table Mountain Sandstone and three lineages with samples from neutral-to-alkaline streams found within eastern South Africa, Malawi and Zambia. The results of this study suggest that B. harrisoni as it is currently recognised is not a single species with a wide geographic range and pH-tolerance, but may comprise up to five species under the phylogenetic species concept, each with limited pH-tolerances, and that the B. harrisoni species group is thus in need of taxonomic review.
Project description:This study investigates genetic diversity in three species of Ephemeroptera, one eurytopic and therefore widespread (<i>Afroptilum sudafricanum</i>) and two stenotopic and thus endemic (<i>Demoreptus natalensis</i> and <i>Demoreptus capensis</i>) species, all of which co-occur in the southern Great Escarpment, South Africa. Mitochondrial DNA was analysed to compare the genetic diversity between the habitat generalist and the two habitat specialists. <i>Afroptilum sudafricanum</i> showed no indication of population genetic structure due to geographic location, while both <i>Demoreptus</i> species revealed clear genetic differentiation between geographic localities and catchments, evident from phylogenetic analyses and high F<sub>ST</sub> values from AMOVA. In addition, the phylogenetic analyses indicate some deeper haplotype divergences within <i>A. sudafricanum</i> and <i>Demoreptus</i> that merit taxonomic attention. These results give important insight into evolutionary processes occurring through habitat specialisation and population isolation. Further research and sampling across a wider geographic setting that includes both major mountain blocks of the Escarpment and lowland non-Escarpment sites will allow for refined understanding of biodiversity and associated habitat preferences, and illuminate comparative inferences into gene flow and cryptic speciation.
Project description:The genus Cymbalcloeon gen. nov. (Ephemeroptera: Baetidae) is established for a new species Cymbalcloeon sartorii sp. nov. from Thailand, based on larval stage. This genus is unique among all of the Baetidae by the presence of three pairs of single gills on segments V-VII, ventrally oriented to cover the sterna VI-IX. Cymbalcloeon sartorii gen. nov. et sp. nov. presents unique or rare morphological characters such as a deeply concave margin between the prostheca and mola, without setae; a very large subtriangular process of the left mandible; a maxillary palp segment II with scarce and very long setae; almost completely fused labial palp segments II and III with numerous very long setae; elongate tarsal claw with two rows of teeth; a shagreen surface of the terga and paraproct; and a very reduced body size. The gills of the new genus move very quickly during respiration and present a near-synchronous protraction. Due to the very derived larval morphological character and the unknown imaginal stage, the exact phylogenetic position of the genus remains unclear; it most certainly belongs to the concept of Anteropatellata and is possibly closely related to the genus Baetopus.
Project description:The Drosophila genome encodes three BEN-solo proteins including Insensitive (Insv), Elba1 and Elba2 that possess activities in transcriptional repression and chromatin insulation. A fourth protein-Elba3-bridges Elba1 and Elba2 to form an ELBA complex. Here, we report comprehensive investigation of these proteins in Drosophila embryos. We assess common and distinct binding sites for Insv and ELBA and their genetic interdependencies. While Elba1 and Elba2 binding generally requires the ELBA complex, Elba3 can associate with chromatin independently of Elba1 and Elba2. We further demonstrate that ELBA collaborates with other insulators to regulate developmental patterning. Finally, we find that adjacent gene pairs separated by an ELBA bound sequence become less differentially expressed in ELBA mutants. Transgenic reporters confirm the insulating activity of ELBA- and Insv-bound sites. These findings define ELBA and Insv as general insulator proteins in Drosophila and demonstrate the functional importance of insulators to partition transcription units.
Project description:Seepage of methane (CH4) on land and in the sea may significantly affect Earth's biogeochemical cycles. However processes of CH4 generation and consumption, both abiotic and microbial, are not always clear. We provide new geochemical and isotope data to evaluate if a recently discovered CH4 seepage from the shallow seafloor close to the Island of Elba (Tuscany) and two small islands nearby are derived from abiogenic or biogenic sources and whether carbonate encrusted vents are the result of microbial or abiotic processes. Emission of gas bubbles (predominantly CH4) from unlithified sands was observed at seven spots in an area of 100 m2 at Pomonte (Island of Elba), with a total rate of 234 ml m-2 d-1. The measured carbon isotope values of CH4 of around -18‰ (VPDB) in combination with the measured ?2H value of -120‰ (VSMOW) and the inverse correlation of ?13C-value with carbon number of hydrocarbon gases are characteristic for sites of CH4 formation through abiogenic processes, specifically abiogenic formation of CH4 via reduction of CO2 by H2. The H2 for methanogenesis likely derives from ophiolitic host rock within the Ligurian accretionary prism. The lack of hydrothermal activity allows CH4 gas to become decoupled from the stagnant aqueous phase. Hence no hyperalkaline fluid is currently released at the vent sites. Within the seep area a decrease in porewater sulphate concentrations by ca. 5 mmol/l relative to seawater and a concomitant increase in sulphide and dissolved inorganic carbon (DIC) indicate substantial activity of sulphate-dependent anaerobic oxidation of methane (AOM). In absence of any other dissimilatory pathway, the ?13C-values between -17 and -5‰ in dissolved inorganic carbon and aragonite cements suggest that the inorganic carbon is largely derived from CH4. The formation of seep carbonates is thus microbially induced via anaerobic oxidation of abiotic CH4.