Abstract:Myrmecia israeliensis has been traditionally considered as a green coccoid free-living microalga. This microalga was previously suggested as the primary phycobiont in the lichens Placidium spp., Heteroplacidium spp., and Psora decipiens. However, due to the absence of ITS rDNA sequences (barcode information) published along with these investigations, the symbiotic nature of M. israeliensis might be confirmed by using the DNA barcoding and different microscopic examinations both in the symbiotic state and in culture. The aim of this study was to settle the presence of M. israeliensis as the primary microalga in squamulose lichens growing in terricolous communities (Psora spp., Placidium spp. and Claviscidium spp.) in 32 localities within European and Canary Island ecosystems by using both molecular and ultrastructural techniques. The lichen-forming fungi were identified using ITS rDNA as a barcode, and in the case of P. decipiens specimens, the mycobiont analyses showed an unexpected variability. Phycobiont phylogenetic analyses were made using both chloroplast (LSU rDNA) and nuclear (ITS rDNA) molecular markers. Our results proved that M. israeliensis is the primary symbiotic microalga in all the chosen and analyzed lichens. In addition, fluorescence microscopy, transmission electron microscopy and scanning electron techniques were used to characterize M. israeliensis. Finally, the presence of this microalga in lichen thalli was verified using different microscopic observations. A combination of different techniques, both molecular and microscopic, allowed for the accurate identification of this symbiotic microalga, beforehand mainly known as free living. Here, we suggest the combination of these techniques to prevent incorrect identification in microalgal lichen studies.

We performed a comparison of molecular and morphological diversity in a freshwater colonial genus Synura (Chrysophyceae, Stramenopiles), using the island of Newfoundland (Canada) as a case study. We examined the morphological species diversity in collections from 79 localities, and compared these findings to diversity based on molecular characters for 150 strains isolated from the same sites. Of 27 species or species‐level lineages identified, only one third was recorded by both molecular and morphological techniques, showing both approaches are complementary in estimating species diversity within this genus. Eight taxa, each representing young evolutionary lineages, were recovered only by sequencing of isolated colonies, whereas ten species were recovered only microscopically. Our complex investigation, involving both morphological and molecular examinations, indicates that our knowledge of Synura diversity is still poor, limited only to a few well‐studied areas. We revealed considerable cryptic diversity within the core S. petersenii and S. leptorrhabda lineages. We further resolved the phylogenetic position of two previously described taxa, S. kristiansenii and S. petersenii f. praefracta, propose species‐level status for S. petersenii f. praefracta, and describe three new species, S. vinlandica, S. fluviatilis, and S. cornuta. Our findings add to the growing body of literature detailing distribution patterns observed in the genus, ranging from cosmopolitan species, to highly restricted taxa, to species such as S. hibernica found along coastal regions on multiple continents. Finally, our study illustrates the usefulness of combining detailed morphological information with gene sequence data to examine species diversity within chrysophyte algae.

A high degree of morphological variability is expressed between the ornately sculptured siliceous scales formed by species in the chrysophycean genus, Synura. In this study, we aimed to uncover the general principles and trends underlying the evolution of scale morphology in this genus. We assessed the relationships among thirty extant Synura species using a robust molecular analysis that included six genes, coupled with morphological characterization of the species‐specific scales. The analysis was further enriched with addition of morphological information from fossil specimens and by including the unique modern species, Synura punctulosa. We inferred the phylogenetic position of the morphologically unique S. punctulosa, to be an ancient Synura lineage related to S. splendida in the section Curtispinae. Some morphological traits, including development of a keel or a labyrinth ribbing pattern on the scale, appeared once in evolution, whereas other structures, such as a hexagonal meshwork pattern, originated independently several times over geologic time. We further uncovered numerous construction principles governing scale morphology and evolution, as follows: (i) scale roundness and pore diameter decreased during evolution; (ii) elongated scales became strengthened by a higher number of struts or ribs; (iii) as a consequence of scale biogenesis, scales with spines possessed smaller basal holes than scales with a keel and; and (iv) the keel area was proportional to scale area, indicating its potential value in strengthening the scale against breakage.

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