Impacts of climate warming and habitat loss on extinctions at species' low-latitude range boundaries

Polewards expansions of species' distributions have been attributed to climate warming, but evidence for climate‐driven local extinctions at warm (low latitude/elevation) boundaries is equivocal. We surveyed the four species of butterflies that reach their southern limits in Britain. We visited 421 sites where the species had been recorded previously to determine whether recent extinctions were primarily due to climate or habitat changes. Coenonympha tullia had become extinct at 52% of study sites and all losses were associated with habitat degradation. Aricia artaxerxes was extinct from 50% of sites, with approximately one‐third to half of extinctions associated with climate‐related factors and the remainder with habitat loss. For Erebia aethiops (extinct from 24% of sites), approximately a quarter of the extinctions were associated with habitat and three‐quarters with climate. For Erebia epiphron, extinctions (37% of sites) were attributed mainly to climate with almost no habitat effects. For the three species affected by climate, range boundaries retracted 70–100 km northwards (A. artaxerxes, E. aethiops) and 130–150 m uphill (E. epiphron) in the sample of sites analysed. These shifts are consistent with estimated latitudinal and elevational temperature shifts of 88 km northwards and 98 m uphill over the 19‐year study period. These results suggest that the southern/warm range margins of some species are as sensitive to climate change as are northern/cool margins. Our data indicate that climate warming has been of comparable importance to habitat loss in driving local extinctions of northern species over the past few decades; future climate warming is likely to jeopardize the long‐term survival of many northern and mountain species.     

Dissolved humic substances – ecological driving forces from the individual to the ecosystem level?

1. This review focuses on direct and indirect interactions between dissolved humic substances (HS) and freshwater organisms and presents novel opinions and hypotheses on their ecological significance. Despite their abundance in freshwaters, the role of HS is still inadequately understood. These substances have been considered too large to be taken up by freshwater organisms. On the contrary, here we present evidence that dissolved HS are indeed taken up and interact directly and/or indirectly with freshwater organisms. 2. We show that dissolved HS exert a mild chemical stress upon aquatic organisms in many ways; they induce molecular chaperones (stress shock proteins), induce and modulate biotransformation enzymes and modulate (mainly inhibiting) the photosynthetic release of oxygen by freshwater plants. Furthermore, they produce an oxidative stress, which may lead to membrane oxidation. HS modulate the multixenobiotic resistance activity and probably other membrane‐bound pumps. This property may lead to the increased bioaccumulation of xenobiotic chemicals. Furthermore, they can modulate the numbers of offspring in a nematode and feminise fish and amphibians. The ecological consequences of this potential remain obscure at present. HS also have the potential to act as chemical attractants (as shown with a nematode). 3. In some macrophytes and algae we show that HS interfere with photosynthesis and growth. For instance, the presence of HS suppresses cyanobacteria more than eukaryotic algae. By applying a quantitative structure activity relationship approach, we show that quinones in the HS interfere with photosynthetic electron transport. We show that even Phragmites leachate can act as a kind of phytotoxin. HS also have the potential to suppress fungal growth, as shown with the water mould Saprolegnia parasitica and force the fungus to respond by spore production. 4. In very soft, humic freshwaters, such as the Rio Negro, Brazil, HS stimulate the uptake of essential ions, such as Na and Ca, at extremely low pH (3.5–4.0) and prevent the ionoregulatory disturbance induced by acid waters, thereby enabling fish to survive in these environments. 5. We discuss whether or not HS are directly utilised by aquatic microorganisms or via exoenzymes, which may be washed in from the terrestrial catchment. There is accumulating evidence that the quality of the HS controls microbial growth. In total, net‐heterotrophy may result from HS‐mediated suppression of primary production by the quinone structures and/or from HS‐mediated support of microbial growth. As there is also evidence that HS have the potential to support photoautotrophic growth and suppress microbial growth, the opposite community effect could result. Consequently, dissolved organic carbon (DOC) has to be chemically characterised, rather than simply measuring bulk DOC concentration. 6. In sum, dissolved HS interact with freshwater organisms in a variety of ways in unenriched humic lakes. In addition to the well known effects of HS on light regime, for example, and the direct and indirect supply with carbon (energy), other interactions may be much more subtle. For instance, HS may induce internal biochemical stress defence systems and have the potential to cause acclimatisation and even adaptation. We are just at the beginning of understanding these interactions between dissolved HS and freshwater organisms.     

Phylogenetics of early branching eudicots: Comparing phylogenetic signal across plastid introns, spacers, and genes

Recent phylogenetic analyses revealed a grade with Ranunculales,Sabiales,Proteales,Trochodendrales,and Buxales as first branching eudicots,with the respective positions of Proteales and Sabiales still ...     

A molecular phylogeny for the pyraloid moths (Lepidoptera: Pyraloidea) and its implications for higher‐level classification

Pyraloidea, one of the largest superfamilies of Lepidoptera, comprise more than 15 684 described species worldwide, including important pests, biological control agents and experimental models. Understanding of pyraloid phylogeny, the basis for a predictive classification, is currently provisional. We present the most detailed molecular estimate of relationships to date across the subfamilies of Pyraloidea, and assess its concordance with previous morphology‐based hypotheses. We sequenced up to five nuclear genes, totalling 6633 bp, in each of 42 pyraloids spanning both families and 18 of the 21 subfamilies, plus up to 14 additional genes, for a total of 14 826 bp, in 21 of those pyraloids plus all 24 outgroups. Maximum likelihood analyses yield trees that, within Pyraloidea, differ little among datasets and character treatments and are strongly supported at all levels of divergence (83% of nodes with bootstrap ≥80%). Subfamily relationships within Pyralidae, all very strongly supported (>90% bootstrap), differ only slightly from a previous morphological analysis, and can be summarized as Galleriinae + Chrysauginae (Phycitinae (Pyralinae + Epipaschiinae)). The main remaining uncertainty involves Chrysauginae, of which the poorly studied Australian genera may constitute the basal elements of Galleriinae + Chrysauginae or even of Pyralidae. In Crambidae the molecular phylogeny is also strongly supported, but conflicts with most previous hypotheses. Among the newly proposed groupings are a ‘wet‐habitat clade’ comprising Acentropinae + Schoenobiinae + Midilinae, and a provisional ‘mustard oil clade’ containing Glaphyriinae, Evergestinae and Noordinae, in which the majority of described larvae feed on Brassicales. Within this clade a previous synonymy of Dichogaminae with the Glaphyriinae is supported. Evergestinae syn. n. and Noordinae syn. n. are here newly synonymized with Glaphyriinae, which appear to be paraphyletic with respect to both. Pyraustinae and Spilomelinae as sampled here are each monophyletic but form a sister group pair. Wurthiinae n. syn. , comprising the single genus Niphopyralis Hampson, which lives in ant nests, are closely related to, apparently subordinate within, and here newly synonymized with, Spilomelinae syn. n.     

Adaptation of Drosophila to a novel laboratory environment reveals temporally heterogeneous trajectories of selected alleles

The genomic basis of adaptation to novel environments is a fundamental problem in evolutionary biology that has gained additional importance in the light of the recent global change discussion. Here, we combined laboratory natural selection (experimental evolution) in Drosophila melanogaster with genome‐wide next generation sequencing of DNA pools (Pool‐Seq) to identify alleles that are favourable in a novel laboratory environment and traced their trajectories during the adaptive process. Already after 15 generations, we identified a pronounced genomic response to selection, with almost 5000 single nucleotide polymorphisms (SNP; genome‐wide false discovery rates < 0.005%) deviating from neutral expectation. Importantly, the evolutionary trajectories of the selected alleles were heterogeneous, with the alleles falling into two distinct classes: (i) alleles that continuously rise in frequency; and (ii) alleles that at first increase rapidly but whose frequencies then reach a plateau. Our data thus suggest that the genomic response to selection can involve a large number of selected SNPs that show unexpectedly complex evolutionary trajectories, possibly due to nonadditive effects.     

Predictive Model of Habitat Suitability for the Marbled Murrelet in Western Washington

Abstract: The marbled murrelet (Brachyramphus marmoratus) is a small Pacific seabird with a breeding range that extends from the Aleutian Islands to central California. Throughout most of its breeding range, it uses mature and old-growth coniferous forests as nesting habitat. Although most murrelets seem to nest within 60 km of the coast, occupied nesting habitat has been identified as far as 84 km from the ocean in Washington state. Due to the extensive inland distances within which birds are known to breed, the area requiring surveys to identify breeding sites can be enormous. Therefore, the standard 2-year survey protocol can be expensive and time-consuming for forest management agencies and companies to administer. We developed a logistic regression model to determine whether a suite of forest structural characteristics could be used to reliably predict occupancy of a forest patch by marbled murrelets. We tested the performance of the final model using cross-validation procedures and a sample of independent sites. We used 50 sites surveyed for marbled murrelets to estimate the model, and 48 independent sites were available to test model performance. All 50 sites were on private forestland owned by Rayonier located in the western lowlands of Olympic Peninsula within the Sitka spruce and western hemlock transition zones. We sampled forest habitat at each site, and we collected information on 15 explanatory variables. The best-fitting logistic regression model contained variables that measured number of canopy layers (P<0.001, approx. F test) and mistletoe (Arceuthobium sp.) abundance (P = 0.031, approx. F test). The model misclassified 2 of 33 (94% correct) unoccupied sites as occupied using a classification cut-off (c) of c=0.25. In the other direction, under cross-validation the final model misclassified 2 of 17 (88% correct) occupied sites as unoccupied. On a test of the model against an independent sample, using a classification cut-off value of c = 0.25, the final model correctly classified 36 of 48 sites (75% correct). The final model misclassified 3 of 31 occupied sites as unoccupied (90% correct). Use of predictive models could greatly reduce the amount of forest that requires surveys by screening out those sites with little probability of use and by focusing remaining effort on higher probability sites, resulting in a higher likelihood of identifying occupied sites and thereby more efficiently conserving marbled murrelet nesting habitat.     

Fuel-Reduction Treatment Effects on Avian Community Structure and Diversity

Abstract: We assessed responses of the breeding bird community to mechanical thinning and prescribed surface fire, alone and in combination, between 2000 and 2006 in ponderosa pine (Pinus ponderosa) forests in northern Arizona, USA. Fuel-reduction treatments did not affect species richness or evenness, and effects on density of 5 commonly detected species varied among species. Populations of some species, such as the western bluebird (Sialia mexicana), increased following burning treatments, whereas others, such as the mountain chickadee (Poecile gambeli), decreased in response to thinning treatments. Our results also identified a temporal response component, where avian community composition and structure changed synchronously on all treatments over time. Given the modest effects these small-scale fuel-reduction treatments had on avian composition and the specific density responses of particular species, our results suggest that land managers should consider implementing prescribed surface fire after thinning projects, where appropriate.     

Vegetative morphology and trait correlations in 54 species of Commelinaceae

The morphospace of 54 species of Commelinaceae from nine genera was examined with simultaneous attention to constraints, adaptive hypotheses and relatedness. Eleven morphological traits, including leaf length and width, angle between the leaves and internode distances, were measured for each species and analysed by principal components analysis and nested analysis of variance. The results revealed a significant signal of relatedness in vegetative morphology; genus explained 20–50% of the variance in a single trait. The relationships between some traits are consistent with adaptive explanations. The findings are consistent with the prediction that evolution for optimal phyllotaxis should be relaxed as self‐shading decreases, and that light availability governs leaf size and branching patterns. Constraints potentially explain some trait correlations, and support was found for the hypothesis that structural constraints govern leaf size and internode size correlations. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 257–268.     

Arthropod community diversity and trophic structure: a comparison between extremes of plant stress

Abstract.  1. Previous studies have shown that plant stress and plant vigour impact the preference and performance of many insect species. Global climate-change scenarios suggest that some regions such as continental interiors may become increasingly subject to severe drought. In combination, these two issues suggest that drought-driven plant stress may impact insect communities on a landscape scale. While there have been many population studies relating plant stress to the life history of individual herbivore species, far less is known about how plant stress affects entire communities.
2. To study the effect of plant stress on arthropod communities, arthropods were sampled from the canopies of pinyon pines ( Pinus edulis ) growing at sites with a history of chronically high environmental stress (e.g. lower water potentials, soil moisture, and reduced growth rates), and those growing under more favourable conditions. Sampling in these environments yielded >59 000 arthropods, representing 287 species from 14 orders and 80 families, and revealed three major community patterns.
3. First, chronic stress significantly altered community composition. Second, trees growing under high stress supported about 1/10th the number of arthropods, and roughly half the species as trees growing under more favourable conditions. Third, of the 33 abundant herbivore species that exhibited a significantly skewed distribution towards either high- or low-stress trees, 73% were skewed with higher numbers on low-stress trees.
4. The pattern of potentially reduced arthropod diversity and abundance on stressed pines observed in this study may further compound the loss of species resulting from the recent, landscape-scale drought-induced mortality of pines in the southwestern USA.     

Isolation and characterization of polymorphic microsatellite loci in the boll weevil,Anthonomus grandis Boheman (Coleoptera: Curculionidae)

The boll weevil (Anthonomus grandis Boheman) is a major insect pest of cotton in North America. Dispersal activity poses a threat to ongoing eradication efforts in the US, but little is known about the frequency of long‐distance migration. Nuclear molecular markers are needed to assess gene flow in relation to geographical distance. A biotin‐enrichment strategy was employed to develop microsatellite markers for the boll weevil. Of 23 loci isolated, 14 were polymorphic with three to 10 alleles per locus. Twelve of the polymorphic loci showed Mendelian inheritance and are likely to be useful in population genetics studies.