Quantifying uncertainty in the potential distribution of an invasive species: climate and the Argentine ant

Maps of a species' potential range make an important contribution to conservation and invasive species risk analysis. Spatial predictions, however, should be accompanied by an assessment of their uncertainty. Here, we use multimodel inference to generate confidence intervals that incorporate both the uncertainty involved in model selection as well as the error associated with model fitting. In the case of the invasive Argentine ant, we found that it was most likely to occur where the mean daily temperature in mid-winter was 7–14 °C and maximum daily temperatures during the hottest month averaged 19–30 °C. Uninvaded regions vulnerable to future establishment include: southern China, Taiwan, Zimbabwe, central Madagascar, Morocco, high-elevation Ethiopia, Yemen and a number of oceanic islands. Greatest uncertainty exists over predictions for China, north-east India, Angola, Bolivia, Lord Howe Island and New Caledonia. Quantifying the costs of different errors (false negatives vs. false positives) was considered central for connecting modelling to decision-making and management processes.     

Spatio-temporal variability in the photosynthetic characteristics of Zostera tasmanica measured by PAM

Rapid light curves (RLCs), based on pulse amplitude modulated (PAM) fluorometry, were used to investigate the spatio-temporal variability in photosynthesis versus irradiance parameters (α, I_k and P_max) and the F_v/F_m ratio of the seagrass Zostera tasmanica (formerly Heterozostera tasmanica). Spatial variation was examined across scales ranging from within a leaf (cms) to across the bed (ms), using a nested analysis of covariance sampling design. Overall, significant variation was identified at all scales examined, excluding the largest scale (area). Patterns of variability differed among individual parameters; however a high percentage of the variation was consistently assigned to the covariates, age (within and between leaves) for all parameters, except P_max.     

Foraging ecomorphology within North American flycatchers and a test of concordance with southern African species

In both the Old and New Worlds, independent clades of sit-and-wait insectivorous birds have evolved. These independent radiations provide an excellent opportunity to test whether the relationships between morphology and ecology are concordant among different communities of flycatchers. First, with canonical correlation analysis, I test for significant relationships between foraging behavior and morphology in North American (NA) and southern African (SA) flycatcher communities. Second, using ordination and analysis of covariance, I test for concordant ecomorphological relationships between the localities. Also, I accounted for phylogeny to see if observed patterns were adaptive. Morphology predicted the foraging behavior in both NA and SA flycatchers. Smaller bill features and longer legs are related to perching and attacking prey items near or on the ground. Larger bill features and short legs are associated with flycatching behavior and high, open perches. The ANCOVA reveals concordance in their ecomorphological relationships, but only in a single ecomorphological axis. The lack of complete concordance may be due to differences in habitat or broad scale historical influences between NA and SA flycatchers.     

Recent applications of fluorescence correlation spectroscopy in live systems

Fluorescence correlation spectroscopy (FCS) is a widely used technique in biophysics and has helped address many questions in the life sciences. It provides important advantages compared to other fluorescence and biophysical methods. Its single molecule sensitivity allows measuring proteins within biological samples at physiological concentrations without the need of overexpression. It provides quantitative data on concentrations, diffusion coefficients, molecular transport and interactions even in live organisms. And its reliance on simple fluorescence intensity and its fluctuations makes it widely applicable. In this review we focus on applications of FCS in live samples, with an emphasis on work in the last 5 years, in the hope to provide an overview of the present capabilities of FCS to address biologically relevant questions.     

Patterns and processes in plant phylogeography in the Mediterranean Basin. A review

Phylogeography, born to bridge population genetics and phylogenetics in an explicit geographic context, has provided a successful platform for unveiling species evolutionary histories. The Mediterranean Basin, one of the earth's 25 biodiversity hotspots, is known for its complex geological and palaeoclimatic history. Aiming to throw light on the causes and circumstances that underlie such a rich biota, a review of the phylogeographic literature on plant lineages from the Mediterranean Basin is presented focusing on two levels. First, phylogeographic patterns are examined, arranged by potential driving forces such as longitude, latitude – and its interaction with altitude –, straits or glacial refugia. Spatial coincidences in phylogeographic splits are found but, in comparison to other regions such as the Alps or North America, no largely common phylogeographic patterns across species are found in this region. Factors contributing to phylogeographic complexity and scarcity of common patterns include less drastic effects of Pleistocene glaciations than other temperate regions, environmental heterogeneity, the blurring of genetic footprints via admixing over time and, for older lineages, possibly a greater stochasticity due to the accumulation of responses to palaeoclimatic changes. At a second level, processes inferred in phylogeographically framed studies that are potential drivers of evolution are examined. These include gradual range expansion, vicariance, long-distance dispersal, radiations, hybridization and introgression, changes in reproductive system, and determinants of successful colonization. Future phylogeographic studies have a great potential to help explaining biodiversity patterns of plant groups and understanding why the Basin has come to be one of the biodiversity hotspots on earth. This potential is based on the crucial questions that can be addressed when geographic gaps are adequately filled (mainly northern Africa and the eastern part of the region), on the important contribution of younger lineages – for which phylogeographic approaches are most useful – to the whole diversity of the Basin, and on the integration of new methods, particularly those that allow refining the search for spatio-temporal concordance across genealogies.     

Ground-truthing the impact of invasive species: spatio-temporal overlap between native least chub and introduced western mosquitofish

Western mosquitofish (Gambusia affinis) are one of the most destructive introduced species in the American West. The negative impact of introduced species on native taxa depends on their spatio-temporal overlap, which will determine the availability of refugia for native species. Experiments on the mechanisms underlying the interactions between introduced and native species rarely address habitat use, overlap, and refugia because individuals are confined to enclosures. In a previous study we used cages, microcosms, and aquaria to show that mosquitofish could prey on and out-compete native least chub (Iotichthys phlegethontis). In this study, we examined the spatio-temporal overlap between mosquitofish and least chub under natural conditions. We found periods of overlap and partitioning in the seasonal and diel habitat use of these species. Both species used shallow habitats during the day and night throughout the spring when least chub were spawning. Predation by adult mosquitofish on young least chub during the spring likely explains the reduction in least chub recruitment in the presence of mosquitofish. During the summer least chub avoided mosquitofish by exclusively using cooler habitats, or by occupying deeper, cooler habitats during the day when mosquitofish were active, and shallower, warmer habitats at night when mosquitofish were inactive. A shift to cooler habitats in the presence of mosquitofish may result in decreased growth and fecundity of least chub. However, we suggest that a reduction of warm shallow habitat may have a disproportionately greater negative impact on mosquitofish than species native to temperate regions, such as least chub. Habitat manipulations that reduce or eliminate warm habitats may ameliorate the harmful effects of mosquitofish and promote the long-term persistence of native taxa.     

Evidence against the use of surrogates for biomonitoring of Neotropical floodplains

1. Community concordance measures the level of association between the compositional patterns shown by two groups of organisms. If strong community concordance occurs, one group could be used as a surrogate for another in conservation planning and biodiversity monitoring. In this study, we evaluated the variability in the strength of community concordance, the likely mechanisms underlying community concordance and the degree to which one community can predict another in a set of Neotropical floodplain lakes (Upper Paraná River floodplain, Brazil). 2. We used a data set including six aquatic communities: fish, macrophytes, benthic macroinvertebrates, zooplankton, phytoplankton and periphyton. We used Mantel and PROTEST approaches to evaluate the levels of community concordance in up to four sampling periods. Also, we used partial Mantel test and information about biotic interactions to investigate reasons for observed patterns of concordance. Finally, we used co‐correspondence analysis to evaluate the performance of one taxonomic group in predicting the structures of other communities. 3. The levels of community concordance varied over time for almost all cross‐taxa comparisons. Concordance between phytoplankton and periphyton probably resulted from similar responses to environmental gradients, whereas other patterns of concordance were likely generated by interactions among groups. However, the levels of predictability were low, and no particular taxonomic group significantly predicted all other groups. 4. The low and temporally variable levels of community concordance cast doubts on the use of surrogate groups for biodiversity management in Neotropical floodplains.     

Reproductive isolation and phylogenetic divergence in Neurospora: comparing methods of species recognition in a model eukaryote

We critically examined methods for recognizing species in the model filamentous fungal genus Neurospora by comparing traditional biological species recognition (BSR) with more comprehensive applications of both BSR and phylogenetic species recognition (PSR). Comprehensive BSR was applied to a set of 73 individuals by performing extensive crossing experiments and delineating biological species based on patterns of reproductive success. Within what were originally considered two species, N. crassa and N. intermedia, we recognized four reproductively isolated biological species. In a concurrent study (Dettman et al. 2003), we used genealogical concordance of four independent nuclear loci to recognize phylogenetic species in Neurospora. Overall, the groups of individuals identified as species were similar whether recognized by reproductive success or by phylogenetic criteria, and increased genetic distance between parents was associated with decreased reproductive success of crosses, suggesting that PSR using genealogical concordance can be used to reliably recognize species in organisms that are not candidates for BSR. In one case, two phylogenetic species were recognized as a single biological species, indicating that significant phylogenetic divergence preceded the development of reproductive isolation. However, multiple biological species were never recognized as a single phylogenetic species. Each of the putative N. crassa x N. intermedia hybrids included in this study was confidently assigned to a single species, using both PSR and BSR. As such, no evidence for a history of hybridization in nature among Neurospora species was observed. By performing reciprocal mating tests, we found that mating type, parental role, and species identity of parental individuals could all influence the reproductive success of matings. We also observed sympatry-associated sexual dysfunction in interspecific crosses, which was consistent with the existence of reinforcement mechanisms.