Abstract: The syenitic rocks of South Rallier du Baty Intrusive Complex (SRBIC) represent intrusions into the oceanic plateau basalts of the south-western Kerguelen Islands. The SRBIC was previously interpreted as a typical ring complex due to magma emplacement with cauldron subsidence. Our new structural and geochronological data reveal that it is a laccolith built between 11.6 and 7.9 Ma by successive injections of magma sheets around the crust–mantle boundary, with an average injection rate between 0.8 and 1.4 × 10−4 km3/year. These results establish strong similarities between the SRBIC, the only recorded example of a felsic laccolith in an oceanic intraplate setting, and many continental plutons emplaced in various geodynamic setting. The SRBIC thus has the characteristics of a continental plutonic complex emplaced in an oceanic plateau crust. We postulate the critical parameter relevant to causing such similarities and plutonic magmatism is crustal thickness.

Abstract: Contents 66 I. 67 II. 68 III. 69 IV. 70 V. 73 VI. 75 VII. 77 78 References 78 Summary Recent decades have seen declines of entire plant clades while other clades persist despite changing environments. We suggest that one reason why some clades persist is that species within these clades use similar habitats, because such similarity may increase the degree of co-occurrence of species within clades. Traditionally, co-occurrence among clade members has been suggested to be disadvantageous because of increased competition and enemy pressure. Here, we hypothesize that increased co-occurrence among clade members promotes mutualist exchange, niche expansion or hybridization, thereby helping species avoid population decline from environmental change. We review the literature and analyse published data for hundreds of plant clades (genera) within a well-studied region and find major differences in the degree to which species within clades occupy similar habitats. We tentatively show that, in clades for which species occupy similar habitats, species tend to exhibit increased co-occurrence, mutualism, niche expansion, and hybridization – and rarely decline. Consistently, throughout the geological past, clades whose species occupied similar habitats often persisted through long time-spans. Overall, for many plant species, the occupation of similar habitats among fellow clade members apparently reduced their vulnerability to environmental change. Future research should identify when and how this previously unrecognized eco-evolutionary feedback operates.

Abstract: Historical patterns of dispersal and population isolation are key components shaping contemporary genetic diversity across landscapes and require explicit consideration when examining the relative role of different factors in driving the evolution of host specificity in parasitic organisms. In this study, we investigate the worldwide colonization history of a common ectoparasite of seabirds, the tick Ixodes uriae. This tick has a circumpolar distribution across both hemispheres but has repeatedly formed host-specific races within different regions. By combining mitochondrial and nuclear data, we infer how this species spread to its present-day distribution and how the colonization process may have affected the geographic and host-associated structure of this tick within regions. We demonstrate that I. uriae is highly structured at a global scale and isolates into four genetic groups that correspond to well-defined geographical regions. Molecular dating suggests that the diversification of I. uriae began in the early Miocene (22 Myr) and that this tick colonized most of the southern hemisphere before moving into northern latitudes via two independent routes. However, no relationship between the degree of host race divergence and colonization history was evident, supporting previous hypotheses that host specialization evolves relatively rapidly in this parasite, but does not typically lead to speciation. We discuss the possible historical and contemporary mechanisms of large-scale dispersal for this ectoparasite and how its biological characteristics may condition current patterns of genetic diversity. More generally, our results illustrate how combining broad-scale sampling and modern molecular tools can help disentangle complex patterns of diversification in widespread parasites.

Abstract: Abstract Aim Despite an improved understanding of Southern Hemisphere plant biogeography, the origins and evolution of sub?Antarctic floras remain poorly studied. Here, we investigate the historical biogeography of sub?Antarctic representatives of the genus Ranunculus. We aimed to establish when and from where the sub?Antarctic ranunculi originated as well as to examine the extent to which ecomorphological traits explain contemporary biogeographical patterns. Location Southern temperate and sub?Antarctic zones. Methods We first estimated a dated phylogeny for Ranunculus using combined chloroplast and nuclear data for 53 accessions; divergence times were inferred based on three temporal calibrations. We then used non?parametric multidimensional scaling to evaluate the ecomorphological diversity of 67 austral ranunculi representing a combination of sub?Antarctic species and those restricted to lower latitude landmasses. Results Phylogenetic analyses indicated that several Ranunculus lineages have colonized the sub?Antarctic islands. Divergence time estimates suggest recent arrival from source areas in Australia, New Zealand or South America. Species exhibiting two distinct ecomorphological trait combinations occur in both sub?Antarctic and lower latitude habitats; the proportions of each combination differed significantly between these areas. Main conclusions Ranunculus has colonized the sub?Antarctic on several occasions, most often arriving from the lower latitude landmasses prior to the Last Glacial Maximum. Taken together our analyses suggest that chance effects are likely to have influenced species arrival. However, following arrival trait?environment interactions appear to have been important for the subsequent establishment and persistence of ranunculi in sub?Antarctic habitats.

Abstract: Abstract Variation in oxidative stress markers in natural populations may provide a useful background for understanding variation in life history strategies. In this study, we seek to evaluate patterns of variation in levels of reactive oxygen metabolites (markers of oxidative damage), serum antioxidant capacity, and serum concentration of thiols (antioxidants endogenously synthesized) in nestling and breeding blue petrels (Halobaena caerulea) and in breeding Antarctic prions (Pachyptila desolata). Male and female prions and nestling petrels did not differ in any of the oxidative stress markers. The serum antioxidant capacity positively correlated with the sample time in nestling blue petrels. Breeding petrels with higher body condition index had higher serum antioxidant capacity and circulating thiols. Finally, both seabird species showed lower levels of reactive oxygen metabolites and higher levels of serum antioxidant capacity than previously studied bird species.