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Biological systematics provides taxonomic information and expertise for biogeography and biological invasion research and management. However, the systematic classification of most taxa, including some alien and invasive species, relies only on morphology. This applies for example to Sertularella tongensis Stechow, 1919 (Cnidaria: Sertulariidae), an alien hydrozoan recently reported in the Mediterranean. Its genus affiliation is still unclear and controversial. Historically, it has been assigned to several existing genera. However, molecular data (COI, 16S, 18S, 28S) provided here do not support these previous assignments. Instead, integrative analyses combining morphological and molecular data support reassigning this species to a new genus, Bicaularia gen. nov. A biogeographic review revealed that this species is widely distributed in the mid- and low-latitude waters of the Indo-Pacific region, and is spreading to some tropical and temperate regions including the Mediterranean and Caribbean Seas, as well as Korea and Japan. This expansion may be attributable to human activity such as shipping through the Suez and the Panama Canals. However, the new record attached to a floating Sargassum algal fragment in the surface water of the open Pacific, might suggest a neglected cryptic spread pathway with the assistance of floating biological organisms. Our findings shed light on the complexity of the phylogeny and spread pathway of the investigated hydrozoan species. We regard the fine systematics as the first step towards future global sampling for molecular studies aiming to elucidate the origins and pathways for alien and invasive species. : pub: 45AB0849-1E3B-477FB643-1B3B4603C1FF [ABSTRACT FROM AUTHOR]

Soil fungi play an important role in promoting nutrient cycling and maintaining ecosystem stability. Yet, there has been little understanding of how fungal co-occurrence networks differ along elevational climate gradients, a topic of interest to both macroecology and climate change studies. Based on high-throughput sequencing technology, we investigated the trend in co-occurrence network structure of soil fungal communities at 11 elevation levels along a 2300 m elevation gradient on Mt. Norikura, Japan, and identified the keystone taxa in the network, hypothesizing a progressive decline in network connectivity with elevation due to decreased plant diversity and enhanced environmental stress caused by changes in climate and soil characteristics. Our results demonstrated that network-level topological features such as network size, average degree, clustering coefficient, and modularity decreased significantly with increasing elevation, indicating that the fungal OTUs at low elevation were more closely associated and the network structure was more compact at low elevations. This conclusion was verified by the negative correlation between positive cohesion, negative cohesion and elevation. Moreover, the negative/positive cohesion ratio reached its peak value in mid-elevations with moderate environmental stress, indicating that the fungal community structure in mid-elevations was more stable than that at other elevations. We also found that the keystone taxa were more abundant at lower elevations. Furthermore, statistical analysis revealed that against a background of uniform geology, climate may play a dominant role in determining the properties and intensity of soil fungal networks, and significantly affect the abundance distribution of keystone taxa. These findings enhance understanding of the pattern and mechanism of the fungal community co-occurrence network along elevation, as well as the responses of microorganisms to climate change on a vertical scale in montane ecosystems. IMPORTANCE: Exploration of the elevational distribution of microbial networks and their driving factors and mechanisms may provide opportunities for predicting potential impacts of environmental changes, on ecosystem functions and biogeographic patterns at a broad scale. Although many studies have explored patterns of fungal community diversity and composition along various environmental gradients, it is unclear how the topological structure of co-occurrence networks shifts along elevational temperature gradients. In this study, we found that the connectivity of the fungal community decreased with increasing elevation and that climate was the dominant factor regulating co-occurrence patterns, apparently acting indirectly through soil characteristics. Our results also suggest that higher elevations on mountains have fewer keystone taxa than low elevations. These patterns may be related to the decrease of plant diversity and the increase of environmental stress along elevation gradients., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2021 Elsevier B.V. All rights reserved.)