Characteristics of introduced Aphididae species, an endemic fly (Anatalanta aptera) and an introduced ground beetle (Merizodus soledadinus) on the Kerguelen Islands

The suite of environments and anthropogenic modifications of sub-Antarctic islands provide key opportunities to improve our understanding of the potential consequences of climate change and biological species invasions on terrestrial ecosystems. The profound impact of human introduced invasive species on indigenous biota, and the facilitation of establishment as a result of changing thermal conditions, has been well documented on the French sub-Antarctic Kerguelen Islands (South Indian Ocean). The present study provides an overview of the vulnerability of sub-Antarctic terrestrial communities with respect to two interacting factors, namely climate change and alien insects. We present datasets assimilated by our teams on the Kerguelen Islands since 1974, coupled with a review of the literature, to evaluate the mechanism and impact of biological invasions in this region. First, we consider recent climatic trends of the Antarctic region, and its potential influence on the establishment, distribution and abundance of alien insects, using as examples one fly and one beetle species. Second, we consider to what extent limited gene pools may restrict alien species' colonisations. Finally, we consider the vulnerability of native communities to aliens using the examples of one beetle, one fly, and five aphid species taking into consideration their additional impact as plant virus vectors. We conclude that the evidence assimilated from the sub-Antarctic islands can be applied to more complex temperate continental systems as well as further developing international guidelines to minimise the impact of alien species.

Silicoflagellates of DSDP Leg 90 sites

Silicoflagellates are described from Sites 588 (middle Eocene), 591 (middle Miocene to lower Pliocene), and 594 (middle Miocene to Quaternary) in the southwest Pacific. At Sites 591 and 594 a detailed silicoflagellate zonation is possible, although there are some obvious differences arising from the latitudinal position of the sites in the silicoflagellate assemblages. Comparison between the sequences recovered at Sites 591 and 206 (Leg 21) revealed two hiatuses in the latter, but helped to establish a zonation for this area from the lower Miocene to the Pleistocene and a correlation to standard nannoplankton zones. The stratigraphic implications of the taxonomy used by various authors and the species concept presented here are discussed in detail. Special reference is made to types described by Ehrenberg and to later synonyma, because the Ehrenberg collection is the base for all subsequent descriptions and evaluations of silicoflagellate taxa. Two new genera (Neonaviculopsis, Paramesocena), two new subspecies (Dictyocha fibula subsp. asymmetrica, Neonaviculopsis neonautica subsp. praenautica), and three new forms (Dictyocha perlaevis f. pentaradiata, Distephanus speculum subsp. speculum f. nonarius, and Mesocena ? hexalitha f. heptalitha) are described from the southwest Pacific Neogene and Pleistocene. Associated sponge spicules were noted and will be described in detail in a later paper, but some are documented on Plate 13.

(Table 2) Rate of reduction in cell size (apical length) and growth rate for seven Fragilariopsis kerguelensis strains sampled during POLARSTERN cruise ANT-XXI/3

The planktonic diatom Fragilariopsis kerguelensis plays an important role in the biogeochemical cycles of the Southern Ocean, where remains of its frustules form the largest deposit of biogenic silica anywhere in the world. We assessed the genetic identity of 26 strains, from cells collected at various sites in the Southern Ocean, using three molecular markers, LSU and ITS rDNA and rbcL. The LSU sequences were identical among the tested strains, ITS sequences were highly similar, and only one base pair difference was detected among the rbcL sequences. These results, together with a large number of successful mating experiments demonstrated that the strains belong to a single biological species. We investigated the mating system and life cycle traits of F. kerguelensis. Cell size diminished gradually in clonal strains. Gamete formation only occurred when strains of opposite mating type - within a cell size range of 7-36 µm - were mixed together. Two binucleate gametes were formed in each gametangium and gamete conjugation produced a zygote that had four nuclei and was surrounded by thin siliceous scales. Two out of the four nuclei subsequently degenerated and the zygote expanded to form an auxospore surrounded by a transverse and a longitudinal perizonium. Staining with the fluorochrome PDMPO provided for the first time a clear demonstration that the longitudinal perizonium is formed after auxospore expansion is complete. Initial cells produced within the mature auxospores were 78-101 µm in length. Various authors have shown that the average valve size of F. kerguelensis varies in sediment samples collected in regions and seasons with different primary production regimes and this parameter has thus been proposed as a biological proxy for palaeo-productivity. A better understanding of the life cycle of F. kerguelensis should help the design of future investigations aimed at testing the link between cell size distribution in the natural environment and the role that environmental factors might have in the regulation of population cell size.

(Table 1) Individual codes, haplotype codes, GenBank accession numbers for DNA sequences and sample locality of the analysed Betamorpha fusiformis specimens from the ANDEEP III expedition

Based on our current knowledge about population genetics, phylogeography and speciation, we begin to understand that the deep sea harbours more species than suggested in the past. Deep-sea soft-sediment environment in particular hosts a diverse and highly endemic invertebrate fauna. Very little is known about evolutionary processes that generate this remarkable species richness, the genetic variability and spatial distribution of deep-sea animals. In this study, phylogeographic patterns and the genetic variability among eight populations of the abundant and widespread deep-sea isopod morphospecies Betamorpha fusiformis [Barnard, K.H., 1920. Contributions to the crustacean fauna of South Africa. 6. Further additions to the list of marine isopods. Annals of the South African Museum 17, 319-438] were examined. A fragment of the mitochondrial 16S rRNA gene of 50 specimens and the complete nuclear 18S rRNA gene of 7 specimens were sequenced. The molecular data reveal high levels of genetic variability of both genes between populations, giving evidence for distinct monophyletic groups of haplotypes with average p-distances ranging from 0.0470 to 0.1440 (d-distances: 0.0592-0.2850) of the 16S rDNA, and 18S rDNA p-distances ranging between 0.0032 and 0.0174 (d-distances: 0.0033-0.0195). Intermediate values are absent. Our results show that widely distributed benthic deep-sea organisms of a homogeneous phenotype can be differentiated into genetically highly divergent populations. Sympatry of some genotypes indicates the existence of cryptic speciation. Flocks of closely related but genetically distinct species probably exist in other widespread benthic deep-sea asellotes and other Peracarida. Based on existing data we hypothesize that many widespread morphospecies are complexes of cryptic biological species (patchwork hypothesis).

(Supplementary Material 2) Landmark coordinates of the analyzed specimens with associated metadata

The use of planktonic foraminifera in paleoceanographic studies relies on the assumption that morphospecies represent biological species with ecological preferences that are stable through time and space. However, genetic surveys unveiled a considerable level of diversity in most morphospecies of planktonic foraminifera. This diversity is significant for paleoceanographic applications because cryptic species were shown to display distinct ecological preferences that could potentially help refine paleoceanographic proxies. Subtle morphological differences between cryptic species of planktonic foraminifera have been reported, but so far their applicability within paleoceanographic studies remains largely unexplored. Here we show how information on genetic diversity can be transferred to paleoceanography using Globorotalia inflata as a case study. The two cryptic species of G. inflata are separated by the Brazil-Malvinas Confluence (BMC), a major oceanographic feature in the South Atlantic. Based on this observation, we developed a morphological model of cryptic species detection in core top material. The application of the cryptic species detection model to Holocene samples implies latitudinal oscillations in the position of the confluence that are largely consistent with reconstructions obtained from stable isotope data. We show that the occurrence of cryptic species in G. inflata, can be detected in the fossil record and used to trace the migration of the BMC. Since a similar degree of morphological separation as in G. inflata has been reported from other species of planktonic foraminifera, the approach presented in this study can potentially yield a wealth of new paleoceanographical proxies.

Seawater carbonate chemistry and biological processes during experiments with four species of marine diatoms

The effect of pCO2 on carbon acquisition and intracellular assimilation was investigated in the three bloom-forming diatom species, Eucampia zodiacus (Ehrenberg), Skeletonema costatum (Greville) Cleve, Thalassionema nitzschioides (Grunow) Mereschkowsky and the non-bloom-forming Thalassiosira pseudonana (Hust.) Hasle and Heimdal. In vivo activities of carbonic anhydrase (CA), photosynthetic O2 evolution, CO2 and HCO3? uptake rates were measured by membrane-inlet mass spectrometry (MIMS) in cells acclimated to pCO2 levels of 370 and 800 ?atm. To investigate whether the cells operate a C4-like pathway, activities of ribulose-1,5-bisphosphate carboxylase (RubisCO) and phosphoenolpyruvate carboxylase (PEPC) were measured at the mentioned pCO2 levels and a lower pCO2 level of 50 ?atm. In the bloom-forming species, extracellular CA activities strongly increased with decreasing CO2 supply while constantly low activities were obtained for T. pseudonana. Half-saturation concentrations (K1/2) for photosynthetic O2 evolution decreased with decreasing CO2 supply in the two bloom-forming species S. costatum and T. nitzschioides, but not in T. pseudonana and E. zodiacus. With the exception of S. costatum, maximum rates (Vmax) of photosynthesis remained constant in all investigated diatom species. Independent of the pCO2 level, PEPC activities were significantly lower than those for RubisCO, averaging generally less than 3%. All examined diatom species operate highly efficient CCMs under ambient and high pCO2, but differ strongly in the degree of regulation of individual components of the CCM such as Ci uptake kinetics and extracellular CA activities. The present data do not suggest C4 metabolism in the investigated species.

(Table 1) Species richness and diversity of tundra plants in herbivore exclosure and control plots near Barrow, Alaska

To determine the role lemmings play in structuring plant communities and their contribution to the 'greening of the Arctic', we measured plant cover and biomass in 50 + year old lemming exclosures and control plots in the coastal tundra near Barrow, Alaska. The response of plant functional types to herbivore exclusion varied among land cover types. In general, the abundance of lichens and bryophytes increased with the exclusion of lemmings, whereas graminoids decreased, although the magnitude of these responses varied among land cover types. These results suggest that sustained lemming activity promotes a higher biomass of vascular plant functional types than would be expected without their presence and highlights the importance of considering herbivory when interpreting patterns of greening in the Arctic. In light of the rapid environmental change ongoing in the Arctic and the potential regional to global implications of this change, further exploration regarding the long-term influence of arvicoline rodents on ecosystem function (e.g. carbon and energy balance) should be considered a research priority.