Oxythermal habitat as a primary driver of ecological niche and genetic diversity in cisco (Coregonus artedi)

Cisco (Coregonus artedi) are threatened by climate change and lake eutrophication, and their oxythermal habitat can be assessed with TDO3, the water temperature at which dissolved oxygen equals 3 mg L-1. We assessed the influence of TDO3 on cisco habitat use, genetic diversity, diets, and isotopic niche in 32 lakes ranging from oligotrophic to eutrophic. Results showed that as TDO3 increased cisco were captured higher in the water column, in a narrower band, with higher minimum temperatures and lower minimum dissolved oxygen. TDO3 was also negatively related to cisco allelic richness and expected heterozygosity, likely driven by summer kill events. Moreover, TDO3 influenced the isotopic niche of cisco, as fish captured deeper were more depleted in δ13C and more enriched in δ15N compared to epilimnetic baselines. Lastly, cisco in high TDO3 lakes consumed more Daphnia, had fewer empty stomachs, and achieved larger body size. Our work identifies specific characteristics of cisco populations that respond to climate change and eutrophication effects, and provides a framework for understanding responses of other cold-water species at the global scale.

Southward range extension of the goldeye rockfish, Sebastes thompsoni (Actinopterygii: Scorpaeniformes: Scorpaenidae), to northern Taiwan

The goldeye rockfish, Sebastes thompsoni (Jordan et Hubbs, 1925), is known as a typical cold-water species, occurring from southern Hokkaido to Kagoshima. In the presently reported study, a specimen was collected from the local fishery catch off Keelung, northern Taiwan, which represents the first specimen-based record of the genus in Taiwan. Moreover, the new record of Sebastes thompsoni in Taiwan represented the southernmost distribution of the cold-water genus Sebastes in the Northern Hemisphere.

Southward range extension of the goldeye rockfish, Sebastes thompsoni (Actinopterygii: Scorpaeniformes: Scorpaenidae), to northern Taiwan

The goldeye rockfish, Sebastes thompsoni (Jordan et Hubbs, 1925), is known as a typical cold-water species, occurring from southern Hokkaido to Kagoshima. In the presently reported study, a specimen was collected from the local fishery catch off Keelung, northern Taiwan, which represents the first specimen-based record of the genus in Taiwan. Moreover, the new record of Sebastes thompsoni in Taiwan represented the southernmost distribution of the cold-water genus Sebastes in the Northern Hemisphere.

Salinity effects on cultured Neogloboquadrina pachyderma (sinistral) from high latitudes: new paleoenvironmental insights

This study presents culture experiments of the cold water species Neogloboquadrina pachyderma (sinistral) and provides new insights into the incorporation of elements in foraminiferal calcite of common and newly established proxies for paleoenvironmental applications (shell Mg/Ca, Sr/Ca and Na/Ca). Specimens were collected from sea ice during the austral winter in the Antarctic Weddell Sea and subsequently cultured at different salinities and a constant temperature. Incorporation of the fluorescent dye calcein showed new chamber formation in the culture at salinities of 30, 31, and 69. Cultured foraminifers at salinities of 46 to 83 only revealed chamber wall thickening, indicated by the fluorescence of the whole shell. Signs of reproduction and the associated gametogenic calcite were not observed in any of the culture experiments. Trace element analyses were performed using an electron microprobe, which revealed increased shell Mg/Ca, Sr/Ca, and Na/Ca values at higher salinities, with Mg/Ca showing the lowest sensitivity to salinity changes. This study enhances the knowledge about unusually high element concentrations in foraminifera shells from high latitudes. Neogloboquadrina pachyderma appears to be able to calcify in the Antarctic sea ice within brine channels, which have low temperatures and exceptionally high salinities due to ongoing sea ice formation.

Biodiversity of Indian Rotifers (Rotifera) with remarks on biogeography and richness in diverse ecosystems

We assess biodiversity status of Rotifera known from India to-date based on our studies from various regions of this country and evaluation of other viable records, and highlight notable features of biogeography and richness. The Indian fauna reveals 434 valid species belonging to 68 genera and 25 families and thus indicates the most biodiverse Rotifera vis-àvis south and Southeast Asia, and records ~25% and ~41% species of global and regional biogeographic interest. It depicts the littoral-periphytic nature, broadly tropical character, the limited reports of cold-water species from the sub-Himalayan and Himalayan latitudes, paucity of the endemics and Bdelloids, and cryptic diversity awaits analyses. The richest diversity and distinct biogeographic identity of Rotifera of Northeast India (NEI) is attributed to location of this region in the ‘Himalayan and Indo-Burmese’ biodiversity hot-spots, ‘Assam gateway’ – the biogeographic corridor, and the ‘Rotiferologist effect’. Regional disparity and spatial heterogeneity of biodiversity elsewhere from India are attributed to the limited sampling, inadequate collections from diverse ecosystems, unidentified species, and paucity of attention on smaller species. The biodiverse rotifer assemblages of the floodplain lakes including Deepor Beel and Loktak Lake, the two Ramsar sites and globally megadiverse ecosystems, are hypothesized to habitat diversity of these ecotones, while ‘Rotifera paradox’ depict speciose constellations per sample. The species-rich small floodplain and urban wetlands focus interest on rotifer diversity in small water bodies. We estimate more diverse Indian Rotifera following analyses of collections from underexplored and unexplored regions and ecosystems, and the bdelloid and sessile rotifers using integrative taxonomic approaches.

Biogeography of intertidal and subtidal native and invasive barnacles in Korea in relation to oceanographic current ecoregions and global climatic changes

The coastline of the Korean Peninsula is influenced by three major oceanographic ecoregions, including the estuarine Yellow Sea ecoregion on the west coast, the warmer and saline East China Sea ecoregion on the south coast, and the cold East Sea ecoregion on the east coast. The influence of these marine ecoregions on the distribution of intertidal barnacles has not been extensively studied. The present study examines the biogeography of thoracican barnacles from intertidal and shallow subtidal zones, along the coasts of Korea. Twenty-one species in seven families were identified, including three species of coral-associated barnacles. Species composition varied significantly in the three marine ecoregions. Multivariate analysis showed barnacle assemblages were significant among the three ecoregions, although there are large overlaps of clusters between the Yellow Sea and East China Sea ecoregions. The estuarine species, Fistulobalanus albicostatus, occurred mainly in the Yellow Sea ecoregion; warm-water species, Tetraclita japonica, and sponge inhabiting barnacles Euacasta dofleini were observed in the East China Sea ecoregion; and cold-water species, Balanus rostratus and Perforatus perforatus, were found in the East Sea ecoregion. Four invasive barnacle species were recorded and the European barnacle Perforatus perforatus expanded its range northward from its recorded distribution nine years earlier. The cold-water species, Chthamalus dalli and Semibalanus cariosus, previously recorded in the East Sea ecoregion, were absent in the present survey. A trend of increasing seawater temperatures in Korean waters may have a significant impact on the distribution of cold-water species and enhance the northward invasion of P. perforatus.

Contrasting species functional trait structuring of subarctic versus subtropical copepod communities

ABSTRACTClassic niche theory assumes that species-level functional traits affect species relative fitness and thus community structuring, but empirical tests of this assumption are scarce. Moreover, recent evidence shows increasing functional over-redundancy towards the tropics, suggesting that the extent to which functional traits confer species’ fitness and thus impact community structuring differs across latitudes. Here, we develop a new method: comparing the frequencies of trait categories in the species-rank abundance distributions of local communities versus their frequencies in the regional average species pool. We contrasted subarctic versus subtropical copepod communities for six important traits. In subarctic communities, medium-sized and cold-water species are selected to dominate, thus traits affect relative fitness as predicted by classic niche theory. In subtropical communities, most species are small and warm-water, but these categories are not selected to dominate, suggesting that greater diversity towards the tropics results from lesser trait-based fitness differences allowing more species to coexist.