Number Of Independent Lineages Research Articles

To the Land and Beyond: Crab Microbiomes as a Paradigm for the Evolution of Terrestrialization.

The transition to terrestrial environments by formerly aquatic species has occurred repeatedly in many animal phyla and lead to the vast diversity of extant terrestrial species. The differences between aquatic and terrestrial habitats are enormous and involved remarkable morphological and physiological changes. Convergent evolution of various traits is evident among phylogenetically distant taxa, but almost no information is available about the role of symbiotic microbiota in such transition. Here, we suggest that intertidal and terrestrial brachyuran crabs are a perfect model to study the evolutionary pathways and the ecological role of animal-microbiome symbioses, since their transition to land is happening right now, through a number of independent lineages. The microorganisms colonizing the gut of intertidal and terrestrial crabs are expected to play a major role to conquer the land, by reducing water losses and permitting the utilization of novel food sources. Indeed, it has been shown that the microbiomes hosted in the digestive system of terrestrial isopods has been critical to digest plant items, but nothing is known about the microbiomes present in the gut of truly terrestrial crabs. Other important physiological regulations that could be facilitated by microbiomes are nitrogen excretion and osmoregulation in the new environment. We also advocate for advances in comparative and functional genomics to uncover physiological aspects of these ongoing evolutionary processes. We think that the multidisciplinary study of microorganisms associated with terrestrial crabs will shed a completely new light on the biological and physiological processes involved in the sea-land transition.

Taxonomy and biogeography of Niphargus steueri (Crustacea: Amphipoda)

Niphargus steueri (Niphargidae) comprises a complex of four subspecies (N. s. steueri, N. s. kolombatovici, N. s. subtypicus, and N. s. liburnicus), the morphology and distribution of which have been poorly known until now. New diagnostic characters of the species and its four subspecies are presented and illustrated. The species is distributed along the major part of the Dinaric Karst, between Slovenia in the northwest and Bosnia and Herzegovina in the southeast. The distribution of the four subspecies approximately resembles the distribution of the evolutionary lineages of the subterranean amphibian Proteus anguinus and the Dinaric lineage of the cave shrimp Troglocaris agg. anophthalmus. Niphargus s. steueri is restricted to the Istran Peninsula; N. s. subtypicus is distributed in southeast Slovenia and northwest Croatia; N. s. liburnicus is known from two disjunctive localities, one on the island of Krk (Croatia) and the other in Gorizia (Italy); and N. s. kolombatovici is restricted to Dalmacija and Herzegovina. The somewhat variable putative synapomorphies of N. steueri probably suggest that the group is old and that the present distribution pattern is a result of historical events, possibly events in the Miocene Dinaride Lake system. Two populations of N. s. kolombatovici and one population of N. s. subtypicus deviate from the general distributional pattern and may belong to cryptic taxa that cannot be distinguished on the basis of morphology. Both hypotheses corroborate with the estimated times of divergence and with the number of independent lineages in the similarly distributed but unrelated stygobionts Proteus and Troglocaris.

PSEUDOFILAMENTOUS GREEN ALGAE FORM INDEPENDENT CHLOROPHYTE AND STREPTOPHYTE LINEAGES

The pseudofilamentous condition in green algae has been characterized as the formation of a linear array of autospores. Although it is likely that this characterization will be found to be an over‐simplification, it serves as a logical starting point for a study of diversity among pseudofilamentous taxa. Therefore, given that molecular phylogenetic analyses have revealed that coccoid, autospore‐formers are found in a number of independent green algal lineages, it is reasonable to expect that pseudofilamentous taxa are likely to be found in a number of distinct lineages. In order to test this hypothesis, data from the nuclear‐encoded 18S r RNA gene were collected from several pseudofilamentous, green algal genera (Geminella, Gloeotila, Hazenia, Interfilum, Microspora, and Sphaeroplea) and incorporated into an 18S rRNA database of chlorobiont taxa. Results from phylogenetic analyses of these data support (1) an alliance of Interfilum, two Geminella isolates, and Klebsormidium within the streptophyte lineage, (2) an alliance of two Geminella isolates and Microspora as a sister group to the ulvophycean/chlorophycean/trebouxiophycean clade or as a sister group to trebouxiophycean taxa, (3) an alliance of Hazenia with ulotrichalean taxa, (4) of Gloeotila with trebouxiophycean taxa and (5) an alliance of Sphaeroplea with chlorophycean taxa. These data confirm that the filamentous condition has evolved in a number of independent lineages. Moreover, these data further illustrate that the extent of molecular variability within the green algae is far from fully appreciated.

Growth Form, Branching Pattern, and Perichaetial Position in Mosses: Cladocarpy and Pleurocarpy Redefined

The terminology for growth form, branching pattern, and position of the perichaetia has been inconsistently used in the literature. This terminology, used for the structural organi- zation in Bryopsida, is reviewed, classified, and redefined. The following interpretations are pro- posed 1) Growth form is differentiated from life form. 2) Direction of growth does not necessarily infer perichaetial position, for there are prostrate acrocarps or erect pleurocarps. Pseudo-pleu- rocarpy is not considered a formal perichaetial position. 3) Cladocarpy is distinct from acrocarpy or pleurocarpy, and defined as perichaetia terminal on lateral branches with juvenile leaf devel- opment similar to that on vegetative branches. The perichaetial branches have lateral primordia that potentially develop subperichaetial branches. Cladocarpy is interpreted as functional pleu- rocarpy that has evolved in a number of independent lineages. 4) Pleurocarpy is defined as perichaetia terminal on lateral innovations that appear sessile and swollen along the supporting axes. The juvenile leaves are morphologically different from those of the vegetative branches. The perichaetial innovations lack lateral branch primordia and thus do not produce subperichaetial branches. These innovations may represent a type of heterochrony-a paedomorphosis in branch development. Pleurocarpy is restricted to the Hypnales, Hookeriales, and Leucodontales, including the Spiridentaceae and Racopilicaneae.