Caenorhabditis nematodes colonize ephemeral resource patches in neotropical forests.

Factors shaping the distribution and abundance of species include life-history traits, population structure, and stochastic colonization-extinction dynamics. Field studies of model species groups help reveal the roles of these factors. Species of Caenorhabditis nematodes are highly divergent at the sequence level but exhibit highly conserved morphological uniformity, and many of these species live in sympatry on microbe-rich patches of rotten material. Here, we use field experiments and large-scale opportunistic collections to investigate species composition, abundance, and colonization efficiency of Caenorhabditis in two of the world's best studied lowland tropical field sites: Barro Colorado Island in Panamá and La Selva in Sarapiquí, Costa Rica. We observed seven species of Caenorhabditis, four of them known only from these collections. While these localities contain species from many parts of the phylogeny, both localities were dominated by globally distributed androdiecious species. We found that Caenorhabditis were able to colonize baits accessible only by phoresy, preferring to colonize baits making direct contact with the ground. We estimate founder numbers per colonization event to be low.

Geographical structure of genetic diversity in Loudetia simplex (Poaceae) in Madagascar and South Africa

Ecologically dominant species are primary determinants of ecosystem function, especially in grassy ecosystems, but the history and biology of grassy ecosystems in Madagascar are poorly understood compared to those of Africa. Loudetia simplex is a C4 perennial grass that is adapted to fire and common to dominant across Africa. It is also widespread across central Madagascar in what are often thought to be human-derived grasslands, leading us to question how recently L. simplex arrived and how it spread across Madagascar. To address this, we collected population genetic data for 11 nuclear and 11 plastid microsatellite loci, newly developed for this study, for > 200 accessions from 78 populations of L. simplex, primarily from Madagascar and South Africa. Malagasy and African populations are genetically differentiated and harbour distinct plastid lineages. We demonstrate distinct geographically clustered diploid, tetraploid and hexaploid groups. The Malagasy hexaploid populations cluster into northern and southern types. In South Africa, diploid populations in the Drakensberg are distinct from tetraploid populations in north-eastern South Africa. Different genetic clusters are associated with significantly different precipitation and temperature. We conclude that L. simplex is native to both Madagascar and South Africa, probably with a single colonization event from Africa to Madagascar followed by pre-human diversification of L. simplex populations in Madagascar.

Settlement and Migration

Beginning with the colonization event in 1788 and then moving through the arrival of free settlers in the nineteenth century, this chapter considers how the British and then colonial governments sutured themselves into the space that became Australia. It explores key cultural and political events that created a sense of belonging for non-Indigenous peoples at this time. The chapter then explains how policies and practices that marked out the limits of migrant belonging have worked, focusing on the migration of groups who were understood as marginal to the nation. Again, emphasis is placed on the range of ideas, events, demands, and desires about migration that complicated policies and practices that clearly sought to produce a white Australia. Lastly, the analysis in this chapter locates migration in relation to the spatial, focusing on how migration and settlement practices were shaped in terms of political and everyday understandings of Australia in relation to: first, other countries in the region, especially Asia; second, the ‘mother country’, the United Kingdom; and finally, the Indigenous peoples within the country.

Integrative taxonomic revision of the woodlouse-hunter spider genus Dysdera (Araneae: Dysderidae) in the Madeira archipelago with notes on its conservation status

Dysdera is a highly speciose genus of mid-sized, nocturnal hunting spiders, mostly circumscribed to the Mediterranean. The genus managed to colonize all Macaronesian archipelagos, and underwent major diversification in the Canary Islands. Here, we report on an independent diversification event on the Madeira archipelago. Based on the integration of morphological and molecular evidence, we describe 8 new species to science, Dysdera dissimilis sp. nov., Dysdera exigua sp. nov., Dysdera isambertoi sp. nov., Dysdera precaria sp. nov., Dysdera recondita sp. nov., Dysdera sandrae sp. nov., Dysdera teixeirai sp. nov., Dysdera titanica sp. nov. and redescribe Dysdera coiffaiti, Dysdera diversa and Dysdera portisancti. We synonymize Dysdera longibulbis and Dysdera vandeli under D. coiffaiti and D. diversa, respectively. Additionally, we use a multilocus target gene phylogeny to support a single colonization event of the archipelago followed by in situ diversification. We further discuss the discovered diversity patterns and their drivers. We conclude to that many of the species inhabit disturbed or fragile habitats and should be considered of high conservation concern.

Low genetic divergence and variation in coastal dune populations of the widespread terrestrial orchid Epipactis helleborine

Reconstructing the early history of species divergence and quantifying the level of standing genetic variation in diverging populations are central to our understanding of ecotype formation and ultimately speciation. In this study, we used single nucleotide polymorphisms to reconstruct the evolutionary history of species divergence in coastal dune populations of the widespread terrestrial orchid Epipactis helleborine and to investigate the level of standing genetic variation in 29 coastal dune populations in a fragmented dune landscape along the Belgian and French coast. Additionally, we used seed introduction experiments to assess the potential for gene flow into existing populations after long-distance seed dispersal and the ability to colonize vacant sites. Our results showed that coastal dune populations diverged only recently from inland populations, went through a significant bottleneck and were most probably the result of a single colonization event. Current levels of population genetic diversity are low and not related to population size or spatial isolation. The sampled dune populations also showed little genetic differentiation, and no apparent spatial genetic structure was observed. Seed introduction experiments showed that seeds of coastal dune populations germinated easily in both occupied and unoccupied sites in dune habitat, indicating that the availability of suitable mycorrhizal fungi is not limiting the distribution of coastal dune populations and that gene flow through seeds has probably contributed to the observed low levels of genetic differentiation. Overall, these results are consistent with a process of genetic divergence after a single, recent colonization event, followed by extensive gene flow among populations.

Thick regoliths and the geological history of climate

<p>The weathering of continental silicate rocks is a main sink of CO<sub>2</sub> at the geological timescale. As it is dependent on the climatic conditions (more weathering in a warmer world), the silicate weathering acts as a negative feedback on the carbon cycle, limiting the amplitude of past climatic changes.</p><p>Many contributions have shown that silicate weathering efficiency (the « weatherability ») is strongly correlated to the physical erosion. Because of this tight link, many works have focused on the role of mountain ranges in the climatic evolution, because those areas are characterized by intense physical denudation, thus potentially boosting chemical weathering. Simply speaking, periods of active mountain building are suspected to generate cold conditions.</p><p>Conversely, little attention has been paid to the role of large and flat continental areas. Due to the lack of physical erosion in those flat areas, the weathering processes will generate thick regoliths, progressively shielding the bedrock and ultimately decreasing the weatherability. Periods of limited mountain building activity might generate very high CO<sub>2</sub> level and warm climatic episodes.</p><p>However, this simple scheme, defining two extreme poles for the surficial Earth system (one mountainous and cold, the other flat and warm) raises several questions:</p><ul><li>the two modes (mountainous and flat) generally co-exist. Their relative role in the control of the climate is probably dependent on the continental configuration, and on the location of tectonically active and non-active areas in latitude and longitude.</li> <li>the dynamics of the thick regolith is not well constrained. How long does it take to generate thick regoliths? What is the response time of thick regoliths to a perturbation?</li> <li>what about the horizontal transfer of sediments? Recent works have shown that sediments are exported from mountain ranges and weathered in plains at the feet of the mountains. How can we incorporate this into numerical models? </li> </ul><p>We will explore the role of the regolith thickness with the spatially-resolved GEOCLIM model. We will focus on the consequences of the colonization of the continents by vascular land plants over the course of the Devonian. This event is suspected to have impacted the weatherability of all the continental surfaces in the same direction (increase in weatherability). We will show that the way atmospheric CO<sub>2</sub> is responding is depending on the initial state of the weathering system, prior to the colonization event. We will also explore the response time of the regolith cover to the global environmental change. We show that short glacial events can be generated in the direct vicinity of the colonization event, if the response time of the regolith layer is long and the colonization is fast. This cold overshoot disappears when the colonization time is assumed to be long (10 Myr), and the continental configuration becomes a critical factor impacting the CO<sub>2</sub> evolution.</p>

Molecular identity of Nemoura lacustris (Plecoptera: Nemouridae) throughout its distributional range

The recent report of Nemoura lacustris Pictet, 1865 in Great Britain has raised doubts on its identity, given the isolation with respect to the Mediterranean and continental populations of this species. Using molecular analyses, we tested if populations from the United Kingdom and the Iberian Peninsula were conspecific and tested the hypotheses of a recent colonization event versus a more ancient origin for the British populations. Phylogenetic analysis of the mitochondrial marker COI allowed us to conclude that the United Kingdom specimens morphologically ascribed to N. lacustris were conspecific with populations from France and the Iberian Peninsula. Based on the genetic divergence of the two reciprocally monophyletic clades from the Iberian Peninsula and Great Britain/France, respectively, the present distribution of N. lacustris can be postulated as a relatively recent dispersal or introduction into Great Britain from France. Finally, we note the isolated position displayed by N. lacustris in the phylogenetic tree of Nemoura species based on COI sequences, as the sister to all included species of the genus. This isolated position corresponds with the specific morphology of N. lacustris genitalia and requires additional studies to ascertain clearer generic boundaries within the Nemouridae.-

Zoogeography of Elasmobranchs in the Colombian Pacific Ocean and Caribbean Sea

ABSTRACT In order to investigate zoogeographical patterns of the marine elasmobranch species of Colombia, species richness of the Pacific and Caribbean and their subareas (Coastal Pacific, Oceanic Pacific, Coastal Caribbean, Oceanic Caribbean) was analyzed. The areas shared 10 families, 10 genera and 16 species of sharks, and eight families, three genera and four species of batoids. Carcharhinidae had the highest contribution to shark richness, whereas Rajidae and Urotrygonidae had the greatest contribution to batoid richness in the Caribbean and Pacific, respectively. Most elasmobranchs were associated with benthic and coastal habitats. The similarity analysis allowed the identification of five groups of families, which characterize the elasmobranch richness in both areas. Beta diversity indicated that most species turnover occurred between the Coastal Pacific and the two Caribbean subareas. The difference in species richness and composition between areas may be due to vicariant events such as the emergence of the Isthmus of Panama. It is unlikely that the Colombian elasmobranch diversity originated from a single colonization event. Local diversification/speciation, dispersal from the non-tropical regions of the Americas, a Pacific dispersion and an Atlantic dispersion are origin possibilities without any of them excluding the others.