Asymmetry patterns across the distribution range: does the species matter?

An important question in evolutionary ecology is whether different populations across a species range, from core to periphery, experience different levels of stress. The estimation of developmental instability has been proposed as a useful tool for quantifying the degree of environmental and genetic stress that individuals experience during their development. Fluctuating asymmetry, the unsigned difference between the two sides of a bilaterally symmetrical trait, has been suggested to reflect the levels of developmental instability in a population. As such, it has been proposed as a useful tool for estimating changes in developmental instability and in stress response in populations across a range of environmental conditions. Recent studies focusing mostly on birds have detected increasing fluctuating asymmetry from core to periphery across the distribution range, suggesting that peripheral populations may experience higher levels of environmental and/or genetic stress. Most of these comparisons were done for single taxa across a single gradient. However, different species are predicted to respond differently to environmental shifts across the range. We compared asymmetry patterns in wing morphology in populations of two Euchloe butterfly species across their opposing ranges in Israel. Contrary to the patterns observed in birds across the same gradient, bilateral asymmetry did not increase or shift towards the periphery in either of the butterfly species. If fluctuating asymmetry in these traits reflects levels of stress, these results may partly reflect the fact that the range of these two butterfly species is limited by the distribution of their host plant, rather than by abiotic environmental variables. In addition, developing pierids can diapause during harsh seasons and can persist in resource‐rich patches, thus minimizing the environmental stress perceived by developing individuals. We conclude that accounting for differences in species’ life histories and range‐limiting factors is necessary in order to better predict patterns of developmental instability across spatial and environmental gradients. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 81 , 313–324.     

A quantitative review of pollination syndromes: do floral traits predict effective pollinators?

The idea of pollination syndromes has been largely discussed but no formal quantitative evaluation has yet been conducted across angiosperms. We present the first systematic review of pollination syndromes that quantitatively tests whether the most effective pollinators for a species can be inferred from suites of floral traits for 417 plant species. Our results support the syndrome concept, indicating that convergent floral evolution is driven by adaptation to the most effective pollinator group. The predictability of pollination syndromes is greater in pollinator‐dependent species and in plants from tropical regions. Many plant species also have secondary pollinators that generally correspond to the ancestral pollinators documented in evolutionary studies. We discuss the utility and limitations of pollination syndromes and the role of secondary pollinators to understand floral ecology and evolution.     

Invasion success of alien plants: do habitat affinities in the native distribution range matter?

Aim To assess how habitat affinities in the native distribution range influence the invasion success of 282 central European neophytes (alien plants introduced after ad 1500). Location Czech Republic. Methods Classification trees were used to determine which native habitats donate the most alien species, the correspondence between habitats occupied by species in their native and invaded distribution ranges, and invasion success of species originating from different habitats. Results The species most likely to naturalize in Central Europe are those associated with thermophile woodland fringes in their native range (81%), cultivated areas of gardens and parks (75%) and broad‐leaved deciduous woodlands (72%). The largest proportions of invasive species recruit from those that occur on riverine terraces and eroded slopes, or grow in both deciduous woodland and riverine scrub. When the relative role of habitats in the native range is assessed as a determinant of the probability that a species will become invasive in concert with other factors (the species’ residence time, life history, region of origin), the direct effect of habitat is negligible. However, the effect of native habitats on patterns of invasions observed in central Europe is manifested by large differences in the numbers of species they supply to the invaded region. More than 50 neophytes were recruited from each of the following habitats: dry grasslands, ruderal habitats, deciduous woodland, inland cliffs, rock pavements and outcrops, and tall‐herb fringes and meadows. Main conclusions Casual species recruit from a wider range of habitats in their native range than they occupy in the invaded range; naturalized but not invasive species inhabit a comparable spectrum of habitats in both ranges, and successful invaders occupy a wider range of habitats in the invaded than in the native range. This supports the idea that the invasive phase of the process is associated with changes in biological features that allow for extension of the spectrum of habitats invaded.     

Generalized pollination system: Are floral traits adapted to different pollinators?

Flowers that are pollinated both during the day and at night could exhibit two different groups of pollinators and produce two different sets of attractants and rewards. We explored the patterns of emission of flower scents and production of nectar in the cactus Echinopsis chiloensis ssp. chiloensis, in relation to the patterns of activity of its diurnal and nocturnal pollinators. We measured frequency of flower visitors, analyzed floral scents, measured nectar production and sugar concentration, and performed pollination exclusion experiments. Bees were the main visitors at daytime and hawkmoths at nighttime. Diurnal scents were dominated by several compounds that can attract a wide range of pollinators, whereas nocturnal scents were less diverse and were dominated by (E)-nerolidol, a compound eliciting antennal responses in hawkmoths. Nectar volume and sugar concentration at night were similar to those recorded in hawkmoth-pollinated flowers. Daytime nectar volume was higher than those commonly found in bee-pollinated flowers, but similar to those found in flowers pollinated by several pollinators. Daytime sugar concentration was similar to those recorded in bee-pollinated flowers. Flowers of E. chiloensis ssp. chiloensis seem morphologically adapted to hawkmoth pollination, but diurnal and nocturnal pollinators contribute to similar extents to reproductive success. Additionally, diurnal and nocturnal pollinators showed a synergic effect on the product of fruit set and seed set. The results are discussed in terms of the linkage between floral traits and perception abilities and requirements of pollinators.     

Pollination syndromes in a specialised plant‐pollinator interaction: does floral morphology predict pollinators in Calceolaria?

Pollination syndromes are defined as suites of floral traits evolved in response to selection imposed by a particular group of pollinators (e.g., butterflies, hummingbirds, bats). Although numerous studies demonstrated their occurrence in plants pollinated by radically different pollinators, it is less known whether it is possible to identify them within species pollinated by one functional pollinator group. In such a framework, we expect floral traits to evolve also in response to pollinator subgroups (e.g., species, genera) within that unique functional group. On this, specialised pollination systems represent appropriate case studies to test such expectations. Calceolaria is a highly diversified plant genus pollinated by oil‐collecting bees in genera Centris and Chalepogenus. Variation in floral traits in Calceolaria has recently been suggested to reflect adaptations to pollinator types. However, to date no study has explicitly tested that observation. In this paper, we quantitatively test that hypothesis by evaluating the presence of pollination syndromes within the specialised pollination system formed by several Calceolaria and their insect pollinators. To do so, we use multivariate approaches and explore the structural matching between the morphology of 10 Calceolaria taxa and that of their principal pollinators. Our results identify morphological matching between floral traits related to access to the reward and insect traits involved in oil collection, confirming the presence of pollinator syndromes in Calceolaria. From a general perspective, our findings indicate that the pollination syndrome concept can be also extended to the intra‐pollinator group level.     

Historical colonization of the Mediterranean Sea by Atlantic fishes: do biological traits matter?

Since its opening 5.33 million years ago, the Gibraltar Strait has always contributed to the Mediterranean fauna and flora. Despite the increasing importance of the phenomenon, ecological determinants underlying colonization success of Atlantic fishes in the Mediterranean Sea have been poorly investigated. Here we reconstruct the recent historical colonization of the whole Mediterranean Sea by Atlantic fishes and we aim to determine where Atlantic fishes preferentially establish and whether some biological traits and ecological factors can be correlated to the colonization success (climate match, position in the water column, maximum body length, propagules, confamilial resistance, depth). A database on Atlantic fish species records from 1810 to 2006 was built and the colonization rate of each introduced species was estimated. Analysis of Variance, Chi squared test and logistic regression were used to investigate the relationships between ecological variables and colonization success. In addition, an index of asymmetry was used to analyse the relative colonization on the two sides of the Mediterranean Sea. Overall 48.33% of Atlantic species introduced in the Mediterranean Sea succeeded in colonizing eastwards. We found that habitat depth of Atlantic species is significantly related to their colonization success due to the obstacle of the shallow depth of the Gibraltar Strait (300 m). It also appears that despite the cyclonic general water circulation on the North Western basin, the northern side is more colonized than the southern one: 70.40% of the studied species colonize the northern side, while only 29.62% colonize the southern one. Two hypotheses may explain this trend: the bottom-up process that enhances the colonization success of Atlantic fishes along the Spanish coast of Alboran Sea owning to its high productivity and the intensiveness of the scientific explorations along the northern Mediterranean side. We conclude that crossing the Gibraltar Strait does not guarantee the colonization success and that species life-history and functional traits are poor predictors. Instead we suggest that environmental factors may determine favourable locations for invasive species installation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: J. Cambray.     

Broad geographic covariation between floral traits and the mating system in Camissoniopsis cheiranthifolia (Onagraceae): multiple stable mixed mating systems across the species' range?

Background and Aims

Plants vary widely in the extent to which seeds are produced via self-fertilization vs. outcrossing, and evolutionary change in the mating system is thought to be accompanied by genetic differentiation in a syndrome of floral traits. We quantified the pattern of variation and covariation in floral traits and the proportion of seeds outcrossed (t) to better understand the evolutionary processes involved in mating system differentiation among and within populations of the short-lived Pacific coastal dune endemic Camissoniopsis cheiranthifolia across its geographic range in western North America.

Methods

We quantified corolla width and herkogamy, two traits expected to influence the mating system, for 48 populations sampled in the field and for a sub-sample of 29 populations grown from seed in a glasshouse. We also measured several other floral traits for 9–19 populations, estimated t for 16 populations using seven allozyme polymorphisms, and measured the strength of self-incompatibility for nine populations.

Key Results

Floral morphology and self-incompatibility varied widely but non-randomly, such that populations could be assigned to three phenotypically and geographically divergent groups. Populations spanned the full range of outcrossing (t = 0·001–0·992), which covaried with corolla width, herkogamy and floral life span. Outcrossing also correlated with floral morphology within two populations that exhibited exceptional floral variation.

Conclusions

Populations of C. cheiranthifolia seem to have differentiated into three modal mating systems: (1) predominant outcrossing associated with self-incompatibility and large flowers; (2) moderate selfing associated with large but self-compatible flowers; and (3) higher but not complete selfing associated with small, autogamous, self-compatible flowers. The transition to complete selfing has not occurred even though the species appears to possess the required genetic capacity. We hypothesize that outcrossing populations in this species have evolved to different stable states of mixed mating.     

How do visitation patterns vary among pollinators in relation to floral display and floral design in a generalist pollination system?

Diverse pollinator assemblages may impose complex selection and thus limit specialisation to particular pollinators. Previous work has concentrated on how visitation rates of different pollinators vary in space and time and how pollinators may vary in efficiency. In this study I quantify variation in visitation rates and foraging behaviour of different insect types (1) in space and time and (2) in relation to variation in floral design (flower size and form) and floral display (number of open flowers) for the distylous clonal shrub Jasminum fruticans. Mean visitation rate showed a significant interaction between insect type and population for seven populations in one year, and between insect types and years for a single population over 3 years. There was also a significant interaction between insect type and population for the proportion of flowers visited. In general the number of visits was positively related to the number of open flowers in a patch, but analyses by insect type showed that this was only true for bee flies and butterflies. Short-tongued bees showed a positive relationship between visitation rate and the number of open flowers on the focal stem, and hawkmoths and butterflies made more visits to plants with larger flowers. Hawkmoths were the only insect type to show a positive relation between the number of flowers visited per foraging bout and flower size. The significant differences between different insect types in patterns of variation in visitation rates in response to floral design and display may act to diversify selection on floral traits, and thereby constrain specialisation of the plant to particular pollinators.     

Plant performance and morpho-functional differentiation in response to edaphic variation in Iberian columbines: cues for range distribution?

Aims Experimental studies of the response to environmental variation of closely related taxa are needed to understand the mechanisms underlying phenotypic divergence, habitat segregation and range span within a radiating genus. We explored the magnitude of phenotypic differentiation and adaptive plasticity in relation to edaphic variation and its significance for habitat segregation and range span in Iberian columbines.Methods We performed a common garden experiment varying soil type (calcareous vs. siliceous) and depth (rocky-shallow vs. deep) with two pairs of widespread and narrowly distributed subspecies of Iberian columbines: Aquilegia vulgaris (subspp. vulgaris and nevadensis) and Aquilegia pyrenaica (subspp. pyrenaica and cazorlensis). We compared tolerance to edaphic variation, trait differentiation and adaptive plasticity of 10 morpho-functional traits between species and distribution ranges. Additionally, we obtained estimates of the competitive environment faced by each taxon in two to four populations per taxa.Important findings Results partially support hypotheses of higher competitive ability and tolerance to edaphic variation in widespread than in narrow endemic taxa. At the species level, the widely distributed taxon was the most tolerant to edaphic variation. Within species, no consistent pattern emerged since the population from the most widespread subspecies was the most tolerant in A. vulgaris but not in A. pyrenaica. Columbines were differentiated in many traits at species and range level. However, the pattern of differentiation does not fully support the hypothesis of higher specialization and stress tolerance in narrow endemics. Although plasticity was generally low, the results support the hypothesis of adaptive plasticity in widespread but not in restricted taxa at least at species level. Ecological differences (adaptive plasticity and competitive ability among others) may have contributed to phenotypic divergence and edaphic niche segregation, as well as to differences in range span among columbines.     

Trade-offs and the evolution of virulence of microparasites: do details matter?

Models of the within-host dynamics of parasites have been used to consider the evolution of microparasites causing acute infections in vertebrate hosts. In this paper, we use these models to examine how the level of virulence to which a parasite evolves, depends on factors such as the relationship between parasite density and its rate of transmission from infected hosts, and the mechanism of parasite-induced pathogenesis. We show that changes in the terms describing transmissibility and pathogenesis may lead to dramatic differences in the level of virulence to which a parasite evolves. This suggests that no single factor is likely to be responsible for the differences in virulence of different parasites, and that understanding of the evolution of virulence of parasites will require a detailed quantitative understanding of the interaction between the parasite and its host.     

Variance partitioning of deconstructed periphyton communities: does the use of biological traits matter?

The use of species traits offers a promising approach to the understanding of the main processes underlying metacommunity patterns. We analyzed samples of periphytic algae in 30 environments of the Upper Paraná River floodplain in southeastern Brazil, to test the hypotheses that variation in species composition of algal groups with low dispersal abilities would be mainly explained by spatial variables; on the other hand, algal groups with higher dispersal abilities would be better explained by environmental variables. The variation in community structure was mainly correlated with environmental variables. This result is in line with a growing body of evidence indicating a predominant role of species-sorting processes. The more-refined prediction that the spatial variables would gradually become more important across a gradient of adherence or size was, however, not supported by our analyses. Also, the large unexplained variation suggested that these periphytic communities were assembled by idiosyncratic events, or that other variables that are often neglected in studies of aquatic metacommunities needed to be included.     

Do molecular markers reflect patterns of differentiation in adaptive traits of conifers?

We have examined patterns of variation of several kinds of molecular markers (isozymes, RFLPs of ribosomal DNA and anonymous low-copy number DNA, RAPDs and microsatellites) and an adaptive trait [date of bud set in Scots pine (Pinus sylvestris L.)]. The study included Finnish Scots pine populations (from latitude 60°N to 70°N) which experience a steep climatic gradient. Common garden experiments show that these populations are adapted to the location of their origin and genetically differentiated in adaptive quantitative traits, e.g. the date of bud set in first-year seedlings. In the northernmost population, bud set took place about 21 days earlier than in the southernmost population. Of the total variation in bud set, 36.4% was found among the populations. All molecular markers showed high levels of within-population variation, while differentiation among populations was low. Among all the studied markers, microsatellites were the most variable (H_e=0.77). Differences between populations were small, G_ST was less than 0.02. Our study suggests that molecular markers may be poor predictors of the population differentiation of quantitative traits in Scots pine, as exemplified here by bud-set date.     

To whom do national days matter? A comparison of national belonging across generations and ethnic groups in the Netherlands

This paper studies to what extent participating in days for national commemoration and celebration is associated with feelings of national belonging, and to what extent this is comparable across generations and ethnic groups. Utilizing data from a national survey (N = 4,505), three major national days in the Netherlands are examined. We find that whereas participation in Queen's Day is associated with national belonging for all generations, for Remembrance Day this holds only for the generation born between 1945 and 1955, and for Liberation Day for the generations born after 1955. Moreover, for citizens with a non-Western origin, participating in national days is associated with national belonging more strongly than for citizens with a native Dutch or other Western background. These findings highlight the importance of paying attention to potential group differences in the association between participation in national days and feelings of national belonging.     

Is the variation of floral elaiophore size in two species of Stigmaphyllon (Malpighiaceae) dependent on interaction with pollinators?

Background: Intraspecific variations in floral traits of species over its geographic range can be associated with differences in pollinator assemblages and/or with environmental conditions.

Aims: We evaluated the area of elaiophores in different populations of Stigmaphyllon bonariense (n = 9) and S. jatrophifolium (n = 6), and we hypothesised a marked reduction in their size towards their southern limits of distribution, associated with different oil-collecting bee assemblages.

Methods: Area of elaiophores was calculated and we carried out linear correlations with floral size, pollinators, visitation rate and pollinator size along the latitudinal gradient of the plants’ distributions. Moreover, we examined the relative size relationships using allometric analyses, to verify this reduction.

Results: Floral elaiophore area decreased with latitude. However, for S. bonariense we observed an allometric reduction in elaiophore area with respect to floral size, while for S. jatrophifolium an isometric reduction was found. In both species, pollinator richness and visitation rate did not diminish with latitude, but pollinator size for S. bonariense varied.

Conclusions: Our results show a reduction in the size of elaiophores in both species along their distribution range, with dissimilar tendencies, suggesting that these species may have different selection pressures that cause variation of their phenotypic traits.     

Does size really matter? A comparative study on floral traits in orchids with two different pollination strategies

• The lock and key hypothesis assumes that male and female genitalia match in a unique system to prevent interspecific crosses. This hypothesis is largely investigated in animals, while there is a distinct lack of studies on plants. Nevertheless, we expect the lock and key hypothesis could apply to plants with complex floral morphologies, such as orchids.
• Here we apply a comparative approach to examine the variation of floral functional traits in food‐ and sex‐deceptive orchids. To understand if a specific deception strategy is related to a specific variation in floral traits evaluated the variation in sterile and fertile traits among species and subsequently examined the correlations between male and female reproductive organs of the same species with the aim of investigating the role of the lock and key hypothesis in deceptive orchids.
• Our results show that the functional morphology of fertile traits plays a pivotal role in limiting gene flow in species that grow in sympatry. In particular, it was observed that the Reproductive Standardisation Index (RSI) is significantly different in the two pollination strategies and that the correlation between pollinarium length and stigmatic cavity length is stronger in food‐deceptive species when compared to the sex‐deceptive species.
• These results reveal that the lock and key hypothesis contributes to maintain boundaries in plants with very complex floral morphology.

     

Pleiotropic effects of statins: do they matter?

Treatment with the 3-hydroxy-3-methylglutaryl coenyzme A reductase inhibitors (or statins) reduces the risk for cardiovascular events across a broad spectrum of patient profiles, as evidenced by both primary prevention and secondary prevention trials. Improved survival by way of reduced deaths from coronary heart disease was also reported with these agents, which are primarily indicated for substantial reduction in LDL-cholesterol levels. However, the statins are extremely complex drugs and exhibit a wide variety of vascular effects that may or may not be dependent on their lipid-modifying properties. These so-called pleiotropic effects include alterations of endothelial function, inflammation, coagulation, and plaque stability. The relative contribution of the nonlipid effects of statin therapy to the well-documented clinical benefits is currently under intense investigation.     

The role of outcrops in the diversity of Patagonian vegetation: Relicts of glacial palaeofloras?

Outcrops around the world enhance biodiversity as they provide heterogeneous environments and varied habitats for species with different requirements than those living in the surroundings, and in this way they increase alpha and beta diversity. We studied the floristic composition of the vegetation of rock outcrops in northwestern Patagonia, Argentina, and compared them to the surrounding matrix of shrubland and steppe. For this we sampled 50 outcrops and 50 matrix plots close to them, identified all the species present, and analyzed their floristic composition with Detrended Correspondence Analysis (DCA). We also analyzed the floras of the north and south faces of the outcrops. The resulting ordinations were related to geographic gradients of the region. The proportions of alien to native species, different life forms, and phylogenetic groups of the outcrop floras were compared to the matrix with G-tests. Our results showed similar dominant families, life form proportions and percentage of alien species in the outcrops and the surrounding matrix. However, species composition of the outcrops was markedly different. North Patagonian outcrops present several taxa not found in the matrix, especially in their southern, less insolated walls. The previously recorded distribution of most of these exclusive species is found in colder areas further south. Thus, we hypothesize that outcrops could be acting as relicts of cold-adapted glacial paleofloras that were probably more extended during glacial times and retreated south after the last glacial maximum.     

Trade-offs in the vertical distribution of zooplankton: ideal free distribution with costs?

Zooplankton vertical migratory patterns are a classic example of optimal habitat choice. We hypothesize that zooplankton distribute themselves vertically in the water column according to an ideal free distribution (IFD) with costs such as to optimize their fitness. In lakes with a deep-water chlorophyll maximum, zooplankton are faced with a trade-off, either experiencing high food (high reproductive potential) but low temperature (slow development) in the hypolimnion or high temperature and low food in the epilimnion. Thus, in the absence of fish predation (e.g. at night) they should allocate the time spent in the different habitats according to fitness gain dependent on the temperature gradient and distribution of food. We tested this hypothesis with a Daphnia hyalina x galeata clone in large indoor columns (Plön Plankton Towers) and with a dynamic energy budget model. In the tower experiments, we simulated a deep-water algal maximum below the thermocline with epilimnetic/hypolimnetic temperature differences of 2, 5 and 10 degrees C. Experimental data supported the model. We found a significantly larger proportion of daphniids in the hypolimnion when the temperature difference was smaller. Our results are consistent with the concept of IFD with costs originally developed for stream fishes. This concept can be applied to predict the vertical distribution of zooplankton in habitats where fish predation is of minor importance.