Quantifying island isolation – insights from global patterns of insular plant species richness

Isolation is a driving factor of species richness and other island community attributes. Most empirical studies have investigated the effect of isolation measured as distance to the nearest continent. Here we expanded this perspective by comparing the explanatory power of seventeen isolation metrics in sixty‐eight variations for vascular plant species richness on 453 islands worldwide. Our objectives were to identify ecologically meaningful metrics and to quantify their relative importance for species richness in a globally representative data set. We considered the distances to the nearest mainland and to other islands, stepping stone distances, the area of surrounding landmasses, prevailing wind and ocean currents and climatic similarity between source and target areas. These factors are closely linked to colonization and maintenance of plant species richness on islands. We tested the metrics in spatial multi‐predictor models accounting for area, climate, topography and island geology. Besides area, isolation was the second most important factor determining species richness on the studied islands. A model including the proportion of surrounding land area as the isolation metric had the highest predictive power, explaining 86.1% of the variation. Distances to large islands, stepping stone distances and distances to climatically similar landmasses performed slightly better than distance to the nearest mainland. The effect of isolation was weaker for large islands suggesting that speciation counteracts the negative effect of isolation on immigration on large islands. Continental islands were less affected by isolation than oceanic islands. Our results suggest that a variety of immigration mechanisms influence plant species richness on islands and we show that this can be detected at macro‐scales. Although the distance to the nearest mainland is an adequate and easy‐to‐calculate measure of isolation, accounting for stepping stones, large islands as source landmasses, climatic similarity and the area of surrounding landmasses increases the explanatory power of isolation for species richness.     

Phylogeography of western Palaearctic reptiles – Spatial and temporal speciation patterns

A phylogeographic analysis of eight species complexes of European reptiles was performed using different molecular methods. While mitochondrial genes (mainly cytochrome b sequences) enabled conclusions about phylogeography and differentiation, additional application of bisexually inherited markers provided information about speciation stages. As species with similar distribution patterns in southern and Central Europe were selected, matching phylogeographic patterns are useful for drawing general conclusions:

(1) The species complexes are in different stages of speciation. In some cases, cryptic species were detected.

(2) Highest genetic diversity occurs in southern Europe, the Near East and the Caucasus, regions corresponding with glacial refuges in the Iberian, Apennine and Balkan Peninsulas as well as in Turkey and the Caucasus. Often, several microrefugia must have existed in close neighbourhood. Additional microrefugia were located in southern France and in the Carpathian Basin.

(3) North Africa and the Middle East did not serve as glacial refuges for Central or northern European lineages and are typically inhabited by independent clades.

(4) Evidence for multiple range retractions and expansions, which were postulated for the times of Pleistocene climatic oscillations, could be found in the Balkans, but in Central Europe their traces have been wiped out by the last glacial. Only the Holocene invasion has left imprints in the genomes from this area.

(5) Central and northern Europe were recolonized from Balkan and Pontic refugia in the Holocene.

(6) Groups from the Iberian and Apennine Peninsulas rarely conquered other regions. This limitation can be attributed to the barrier function of the Pyrenees and the Alps.

Biofuels and invasive species from an African perspective – a review

A large number of proposed biofuel crops share the same traits as known invasive plant species, many of which are already present in Africa and include species such as Prosopis glandulosa Torrey (Mimosaceae), P. juliflora (Sw.) DC, Leucaena leucocephala (Lam.) de Wit (Mimosaceae), Azadirachta indica A. Juss. (Meliaceae), and others. In this paper, we mainly assess the impacts of invasive Prosopis species in Africa, particularly in Kenya and South Africa. Introduced Prosopis species have invaded over 4 million hectares in Africa, threatening crop and pasture production, reducing underground water reserves, and displacing native plant and animal species. This has major implications for millions of people who depend on natural resources for their survival. It is therefore suggested that known invasive or potentially invasive plant species not be introduced to countries or regions for biofuel production. If (after a stringent cost–benefit analysis) the introduction of a potentially invasive species is deemed critical for economic development and the benefits clearly outweigh the potential costs, countries should endeavour to abide by the Principles and Criteria for Sustainable Biofuel Production developed by the Roundtable on Sustainable Biofuels.     

Upslope movements and large scale expansions: the taxonomy and biogeography of the Coenonympha arcania –C. d arwiniana –C. gardetta butterfly species complex

Sibling species groups are suitable models for the understanding of inter‐ and intraspecific processes in taxonomy and biogeography. We analysed 262 individuals from the Alps of the Coenonympha arcania/gardetta species complex by allozyme electrophoresis. These taxa showed high variance amongst populations (F_ST: 0.391) and strong intertaxon genetic differentiation (F_CT: 0.376). Although morphologically similar, Coenonympha gardetta and Coenonympha arcania clearly differ in their genetic characteristics; the morphologically intermediate taxa Coenonympha darwiniana darwiniana and Coenonympha darwiniana macromma are genetically well distinguished from each other and the two other taxa. Coenonympha arcania and C. d. macromma most probably share a common ancestor and evolved by cladogenesis, whereas the taxonomic situation of C. d. darwiniana is still unresolved: This taxon might be the result of hybridization between C. arcania and C. gardetta or it might have a common ancestor together with C. gardetta. We suggest species rank for all four taxa. The distribution of genetic diversity of these populations and the differentiation amongst populations suggest rather different biogeographical scenarios: C. arcania most probably is of Mediterranean origin with postglacial range expansion northwards; C. gardetta survived the last ice age in peripheral refugia of the Alps and has spread all over this high mountain system in the postglacial; C. darwiniana and C. macromma survived the Würm in geographic proximity to their actual distribution areas and only have performed moderate uphill translocations during postglacial warming. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 159 , 890–904.     

Long-term persistence of aspen – a key host for many threatened species – is endangered in old-growth conservation areas in Finland

Large, dead and dying European aspens (Populus tremula L.) host many threatened species in Fennoscandian boreal forests. Large aspen trees have mostly disappeared and are being harvested from the managed forests that cover 95% of the forest area in Finland. Due to the small area protected (4.1%), the aspen-associated species may encounter major difficulties in the protected areas if aspen trees disappear due to natural forest succession. The availability of aspens was assessed in the old-growth conservation area network in eastern Finland. We mapped all the living and dead aspens in 15 protected old-growth forests. The total number of counted trees was 32 903 individuals. Current amounts of living (2.7 m³/ha) and especially dead aspens (2.8 m³/ha) in the protected areas were higher than in the surrounding managed forests (1.1 and 0.1 m³/ha for living and dead trees, respectively). However, while saplings (dbh<5 cm) occur in most of the areas (12 individuals/ha on average) they survive poorly and young aspen cohorts (5 cm <dbh<15 cm) are lacking or are very rare. The most likely reason for the poor sapling survival is high browsing pressure by the mammalian herbivores, especially the moose. The moose population has increased many times in Finland during the past decades. The poor regeneration of aspens implies that the value of the old-growth conservation areas for aspen-associated species will face a serious bottleneck within a few decades when the currently middle-aged tree cohorts disappear. If the current high browsing pressure and lack of natural disturbances continue the obligatory aspen-associated species may disappear both locally and regionally from the network of the protected areas.     

Phylogenetic species recognition and species concepts in fungi

The operational species concept, i.e., the one used to recognize species, is contrasted to the theoretical species concept. A phylogenetic approach to recognize fungal species based on concordance of multiple gene genealogies is compared to those based on morphology and reproductive behavior. Examples where Phylogenetic Species Recognition has been applied to fungi are reviewed and concerns regarding Phylogenetic Species Recognition are discussed.     

Racial differences in subcutaneous fat patterns in children aged 7–15 years

In a stratified random sample of 278 children aged 7–15 years of an entire biracial community, skinfold measurements were taken on six standard body sites. We found that white children had generally thicker skinfolds than blacks for the same body weight, with a consistent exception: the subscapular skinfold was relatively thicker in blacks. It is suggested that this racial difference in distribution of fat may manifest a genetic adaptive trait developed under circumstances demanding both a caloric reserve and facilitation of convective heat loss in tropical climates.     

On the integrated frameworks of species concepts: Mayden’s hierarchy of species concepts and de Queiroz’s unified concept of species

Richard L. Mayden and Kevin de Queiroz have devised and developed ‘a hierarchy of species concepts’ and ‘a unified species concept’, respectively. Although their integrated frameworks of species concepts are rather different as to how to integrate the diverse modern concepts of species, the end result is that they are likely to agree on species recognition in nature, because they virtually share the same major components (i.e. evolutionary or lineage concept of species; same way of delimiting species), and have the same important consequences. Both the hierarchical and unified frameworks, however, are interpreted to have shortcoming regarding the way of integrating the modern species concepts. I reformulate these ideas into a framework of species concepts as follows: It treats the idea of species as population‐level evolutionary lineages (sensu Wiley 1978 ) as the concept for species category, and it adopts the contingent biological properties of species (e.g. internal reproductive isolation, diagnosability, monophyly) as operational criteria in delimiting species. I also suggest that existing and revised versions of the integrated framework of species concepts all are not new species concepts, but versions of the evolutionary species concept, because they treat the evolutionary (or lineage) species concept as the concept for species category.     

Modelling of Nutrient Emissions in River Systems – MONERIS – Methods and Background

MONERIS is a semi‐empirical, conceptual model, which has gained international acceptance as a robust meso‐ to macro scale model for nutrient emissions. MONERIS is used to calculate nitrogen (N) and phosphorus (P) emissions into surface waters, in‐stream retention, and resulting loads, on a river catchment scale. This paper provides the first (i) comprehensive overview of the model structure (both the original elements and the new additions), (ii) depiction of the algorithms used for all pathways, and for retention in surface waters, and (iii) illustration of the monthly disaggregation of emissions and the implementation of measures. The model can be used for different climatic conditions, long term historical studies, and for future development scenarios. The minimum validated spatial resolution is 50 km², with a temporal resolution of yearly or monthly time steps. The model considers seven emission pathways (atmospheric deposition on surface waters, overland flow, erosion, tile drainage, groundwater, emissions from sealed urban areas, and point sources), and six emission sources (natural background, fertilizer application, nitrogen atmospheric deposition on arable land and other areas, urban sources, and point sources); and these are calculated separately for different land‐uses. The pathway and source‐related approach is a prerequisite for the implementation of measures to reduce non‐point and point‐source emissions. Therefore, we have modified MONERIS by the addition of a “management alternative” tool which can identify the potential effectiveness of nutrient reduction measures. MONERIS is an appropriate tool for addressing the scientific and political aspects of river basin management in support of a good surface water quality. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

–SH and S–S involvement in Chlamydomonas mating

Reagents that block or cross-link sulfhydryl (–SH) groups and those that reduce disulfide (S–S) bonds have been tested for their effects on mating in Chlamydomonas reinhardii. Wild-type (wt) gametes of mating type + (mt⁺) and mt^?, and a fusion-defective mt^? mutant, gam-11, were studied. Differential sensitivities of mt⁺ vs mt^? and of wt mt^? vs gam-11 mt^? were analyzed. Concentrations of reagents that did not disrupt flagellar agglutination, the first stage of the mating reaction, were generally used. Pretreatment of mt⁺ gametes with the membrane permeable –SH reducing agent dithiothreitol (DTT) inhibits flagellar sexual signaling at concentrations that do not inhibit any part of the mating reaction of mt^? gametes. Wt mt^? is more sensitive than wt mt⁺ to inhibition by low concentrations of p-chloromercuribenzoate sulfonate (pCMBS), an organic mercurial. The membrane-impermeable reducing agent, reduced glutathione (GSH), also preferentially inhibits wt mt^?. Gam-11 mt^?, a fusion-defective mutant, which has been used to study the sensitivity of the adhesion of the plasma membrane-associated mating structures, is less sensitive to GSH and pCMBS inhibition that is wt mt^?. DDT and pCMBS cause an increase in mating structure adhesion in pretreated gam-11. The differential inhibition of pair and group formation during gam-11 × wt mt⁺ matings has suggested a possible mechanism for mating structure adhesion.     

Testing population differentiation in plant species – how important are environmental maternal effects

The maternal environment may contribute to population differentiation in offspring traits if growing conditions of mother plants are different. However, the magnitude of such environmental maternal effects compared with genetic differentiation is often not clear. We tested the importance of environmental maternal effects by comparing population differentiation in parental seed directly collected in the field and in F₁ seed grown under homogeneous conditions. The F₁ seeds were obtained by random crosses within populations. We used five populations in each of four plant species to analyse seed mass and growth chamber germination of both generations at the same time. In two species, we additionally tested offspring performance in the field. We found a significant population differentiation in all species and for nearly all measured traits. Population‐by‐generation interactions indicating environmental maternal effects were significant for germination (three species) and for seed mass (two species) but not for growth and reproduction. The significant interaction was partly due to a reduction of among‐population differentiation from the parental to the F₁ generation that can be explained by a decrease of maternal provisioning effects. However, in some species by trait combinations a change in population ranking and not a decrease of variation was responsible for significant population‐by‐generation interactions indicating environmental maternal effects beyond maternal provisioning. Fitting of seed mass as covariate was not successful in reducing environmental maternal effects on population differentiation in germination. We discuss alternative methods to account for environmental maternal effects in studies on genetic differentiation among populations.