CiteULike: cmm's library [1936 articles]

Long-term observation of a pollination network: fluctuation in species and interactions, relative invariance of network structure and implications for estimates of specialization

Petanidou — 2008-05-08T08:04:02-00:00

Ecology Letters, Vol. 11, No. 6. (June 2008), pp. 564-575.

Is the magnitude of pollen limitation in a plant community affected by pollinator visitation and plant species specialisation levels?

Stein Hegland — 2008-06-22T19:09:24-00:00

Oikos, Vol. 117, No. 6. (2008), pp. 883-891.

Pollen limitation on a plant community level has received little attention, although it might show which pollination-related traits may cause pollen limitation to vary among species. To address several central questions in plant reproductive biology, we investigated pollen limitation in 11 plant species, including visitation and specialisation levels of all species. The female reproductive success of most species within the studied plant community was not pollen limited, but a general tradeoff between seed production and seed weight occurred as a response to supplemental pollination. In contrast to general notion, we did not find that less visited species were most pollen limited. Instead, it appears that species with high visitation rates were most pollen limited. Our study provided conflicting evidence to whether specialisation levels may affect the degree of pollen limitation within the study community. We discuss these findings in the context of recent reviews on the occurrence, causes and consequences of pollen limitation in plants. In particular, we propose that, although pollen limitation is an important phenomenon, 1) the majority of species within a plant community may not experience pollen limitation at a given moment, 2) that common notions of which plant species should experience pollen limited reproductive success do not hold true in the studied plant community, and 3) that offspring quality is as likely affected by surplus pollen loads as is the number of offspring.

An emerging synthesis between community ecology and evolutionary biology

Marc Johnson — 2007-04-27T15:03:12-00:00

Trends in Ecology & Evolution, Vol. 22, No. 5. (May 2007), pp. 250-257.

A synthesis between community ecology and evolutionary biology is emerging that identifies how genetic variation and evolution within one species can shape the ecological properties of entire communities and, in turn, how community context can govern evolutionary processes and patterns. This synthesis incorporates research on the ecology and evolution within communities over short timescales (community genetics and diffuse coevolution), as well as macroevolutionary timescales (community phylogenetics and co-diversification of communities). As we discuss here, preliminary evidence supports the hypothesis that there is a dynamic interplay between ecology and evolution within communities, yet researchers have not yet demonstrated convincingly whether, and under what circumstances, it is important for biologists to bridge community ecology and evolutionary biology. Answering this question will have important implications for both basic and applied problems in biology.

Constrained lability in floral evolution: counting convergent origins of hummingbird pollination in Penstemon and Keckiella

Paul Wilson — 2008-02-01T08:56:30-00:00

New Phytologist, Vol. 176, No. 4. (2007), pp. 883-890.

Summary . In the clade of Penstemon and segregate genera, pollination syndromes are well defined among the 284 species. Most display combinations of floral characters associated with pollination by Hymenoptera, the ancestral mode of pollination for this clade. Forty-one species present characters associated with hummingbird pollination, although some of these ornithophiles are also visited by insects. . The ornithophiles are scattered throughout the traditional taxonomy and across phylogenies estimated from nuclear (internal transcribed spacer (ITS)) and chloroplast DNA (trnCD/TL) sequence data. Here, the number of separate origins of ornithophily is estimated, using bootstrap phylogenies and constrained parsimony searches. . Analyses suggest 21 separate origins, with overwhelming support for 10 of these. Because species sampling was incomplete, this is probably an underestimate. . Penstemons therefore show great evolutionary lability with respect to acquiring hummingbird pollination; this syndrome acts as an attractor to which species with large sympetalous nectar-rich flowers have frequently been drawn. By contrast, penstemons have not undergone evolutionary shifts backwards or to other pollination syndromes. Thus, they are an example of both striking evolutionary lability and constrained evolution. New Phytologist (2007) 176: 883-890 c The Authors (2007). Journal compilation c New Phytologist (2007) doi: 10.1111/j.1469-8137.2007.02219.x

Phylomatic: tree assembly for applied phylogenetics

Campbell Webb — 2005-02-23T03:25:00-00:00

Molecular Ecology Notes, Vol. 5, No. 1. (March 2005), pp. 181-183.

Non-random coextinctions in phylogenetically structured mutualistic networks

Enrico Rezende — 2007-08-24T11:04:19-00:00

Nature, Vol. 448, No. 7156., pp. 925-928.

A phylogenetic analysis of the arachnid orders based on morphological characters

Jeffrey Shultz — 2007-06-12T03:20:13-00:00

Zoological Journal of the Linnean Society, Vol. 150, No. 2. (2007), pp. 221-265.

Morphological evidence for resolving relationships among arachnid orders was surveyed and assembled in a matrix comprising 59 euchelicerate genera (41 extant, 18 fossil) and 202 binary and unordered multistate characters. Parsimony analysis of extant genera recovered a monophyletic Arachnida with the topology (Palpigradi (Acaromorpha (Tetrapulmonata (Haplocnemata, Stomothecata nom. nov.)))), with Acaromorpha containing Ricinulei and Acari, Tetrapulmonata containing Araneae and Pedipalpi (Amblypygi, Uropygi), Haplocnemata (Pseudoscorpiones, Solifugae) and Stomothecata (Scorpiones, Opiliones). However, nodal support and results from exploratory implied weights analysis indicated that relationships among the five clades were effectively unresolved. Analysis of extant and fossil genera recovered a clade, Pantetrapulmonata nom nov., with the topology (Trigonotarbida (Araneae (Haptopoda (Pedipalpi)))). Arachnida was recovered as monophyletic with the internal relationships (Stomothecata (Palpigradi, Acaromorpha (Haplocnemata, Pantetrapulmonata))). Nodal support and exploratory implied weights indicated that relationships among these five clades were effectively unresolved. Thus, some interordinal relationships were strongly and/or consistently supported by morphology, but arachnid phylogeny is unresolved at its deepest levels. Alternative hypotheses proposed in the recent literature were evaluated by constraining analyses to recover hypothesized clades, an exercise that often resulted in the collapse of otherwise well-supported clades. These results suggest that attempts to resolve specific nodes based on individual characters, lists of similarities, evolutionary scenarios, etc., are problematic, as they ignore broader impacts on homoplasy and analytical effects on non-target nodes. c 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 150, 221-265.

The impact of herbivore-plant coevolution on plant community structure

Judith Becerra — 2007-05-16T02:19:04-00:00

PNAS, Vol. 104, No. 18. (1 May 2007), pp. 7483-7488.

Coevolutionary theory proposes that the diversity of chemical structures found in plants is, in large part, the result of selection by herbivores. Because herbivores often feed on chemically similar plants, they should impose selective pressures on plants to diverge chemically or bias community assembly toward chemical divergence. Using a coevolved interaction between a group of chrysomelid beetles and their host plants, I tested whether coexisting plants of the Mexican tropical dry forest tend to be chemically more dissimilar than random. Results show that some of the communities are chemically overdispersed and that overdispersion is related to the tightness of the interaction between plants and herbivores and the spatial scale at which communities are measured. As coevolutionary specialization increases and spatial scale decreases, communities tend to be more chemically dissimilar. At fairly local scales and where herbivores have tight, one-to-one interactions with plants, communities have a strong pattern of chemical disparity. 10.1073/pnas.0608253104

Butterfly seed predation: effects of landscape characteristics, plant ploidy level and population structure

Leena Arvanitis — 2007-05-14T16:17:21-00:00

Oecologia, Vol. 152, No. 2. (4 May 2007), pp. 275-285.

Abstract Polyploidization has been suggested as one of the most common mechanisms for plant diversification. It is often associated with changes in several morphological, phenological and ecological plant traits, and therefore has the potential to alter insect–plant interactions. Nevertheless, studies evaluating the effect of plant polyploidy on interspecific interactions are still few. We investigated pre-dispersal seed predation by the butterfly Anthocharis cardamines in 195 populations of two ploidy levels of the herb Cardamine pratensis (tetraploid ssp. pratensis, 2n = 30 vs. octoploid ssp. paludosa, 2n = 56–64). We asked if differences in incidence and intensity of predation among populations were related to landscape characteristics, plant ploidy level and population structure. The incidence of the seed predator increased with increasing plant population size and decreasing distance to nearest population occupied by A. cardamines. The intensity of predation decreased with increasing plant population size and was not affected by isolation. Probability of attack decreased with increasing shading, and intensity of predation was higher in grazed than in non-grazed habitats. The attack intensity increased with increasing mean flower number of plant population, but was not affected by flowering phenology. Individuals in tetraploid populations suffered on average from higher levels of seed predation, had higher mean flower number, were less shaded and occurred more often in grazed habitats than octoploid populations. When accounting for differences in habitat preferences between ploidy levels there was no longer a difference in intensity of predation, suggesting that the observed differences in attack rates among populations of the two ploidy levels are mediated by the habitat. Overall, our results suggest that polyploidization is associated with differentiation in habitat preferences and phenotypic traits leading to differences in interspecific interaction among plant populations. This, in turn, may facilitate further divergence of ploidy levels.

Evolution of Duplicate Gene Expression in Polyploid and Hybrid Plants

Keith Adams — 2007-04-25T18:49:47-00:00

J Hered, Vol. 98, No. 2. (1 March 2007), pp. 136-141.

Allopolyploidy is a prominent mode of speciation in flowering plants. On allopolyploidy, genomic changes can take place, including chromosomal rearrangement and changes in gene expression; these processes continue over evolutionary time. Recent studies of gene expression in polyploid and hybrid plants, reviewed here, have examined expression in natural polyploids and synthetic neopolyploids as well as in diploid and F1 hybrids. Considerable changes in gene expression have been observed in allopolyploids, including up- or downregulation of expression in the polyploids compared with their parents, unequal expression of duplicated genes, and silencing of one copy. Genes in a variety of functional categories show altered expression, and the patterns vary considerably by gene. Some changes seem to be stochastic, whereas others are repeatable. Gene expression changes can be organ specific. Reciprocal silencing of duplicates in different organs has been observed, suggesting subfunctionalization and long-term retention of duplicates. It has become clear that hybridization has a much greater effect than chromosome doubling on gene expression in allopolyploids. Diploid and triploid F1 hybrids can show alterations of expression levels compared with their parents. Parent-of-origin effects on gene expression have been examined, and loss of gene imprinting has been shown. Some gene expression changes in polyploids and hybrids can be correlated with phenotypic effects. Demonstrated mechanisms of gene expression changes include DNA methylation, histone modifications, and antisense RNA. Several hypotheses have been proposed for why gene expression is altered in allopolyploids and hybrids. 10.1093/jhered/esl061

Phylogeny and classification of Muscini (Diptera, Muscidae)

Silvio Nihei — 2007-04-06T22:08:00-00:00

Zoological Journal of the Linnean Society, Vol. 149, No. 4. (April 2007), pp. 493-532.

Geographical variation in floral traits of the tree tobacco in relation to its hummingbird pollinator fauna

Julieta Nattero — 2007-03-24T18:43:56-00:00

Biological Journal of the Linnean Society, Vol. 90, No. 4. (April 2007), pp. 657-667.

A comprehensive phylogeny of the bumble bees (Bombus)

SA Cameron — 2007-04-24T19:57:43-00:00

Biological Journal of the Linnean Society, Vol. 91, No. 1. (2007), pp. 161-188.

Bumble bees (Bombus Latreille) occupy a wide diversity of habitats, from alpine meadows to lowland tropical forest, yet they appear to be similar in morphology throughout their range, suggesting that behavioural adaptations play a more important role in colonizing diverse habitats. Notwithstanding their structural homogeneity, bumble bees exhibit striking inter- and intraspecific variation in colour pattern, purportedly the outcome of mimetic evolution. A robust phylogeny of Bombus would provide the framework for elucidating the history of their wide biogeographical distribution and the evolution of behavioural and morphological adaptations, including colour pattern. However, morphological studies of bumble bees have discovered too few phylogenetically informative characters to reconstruct a robust phylogeny. Using DNA sequence data, we report the first nearly complete species phylogeny of bumble bees, including most of the 250 known species from the 38 currently recognized subgenera. Bayesian analysis of nuclear (opsin, EF-1alpha, arginine kinase, PEPCK) and mitochondrial (16S) sequences results in a highly resolved and strongly supported phylogeny from base to tips, with clear-cut support for monophyly of most of the conventional morphology-based subgenera. Most subgenera fall into two distinct clades (short-faced and long-faced) associated broadly with differences in head morphology. Within the short-faced clade is a diverse New World clade, which includes nearly one-quarter of the currently recognized subgenera, many of which are restricted to higher elevations of Central and South America. The comprehensive phylogeny provides a firm foundation for reclassification and for evaluating character evolution in the bumble bees. c 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 161-188.

On nestedness analyses: rethinking matrix temperature and anti-nestedness

Mario Almeida-Neto — 2007-04-03T20:37:01-00:00

Oikos, Vol. 116, No. 4. (2007), pp. 716-722.

The analysis of nested structures in sets of species assemblages across different sites or in networks of interspecific interactions has become common practice in ecological studies. Although new analyses and metrics have been proposed, few studies have scrutinized the concepts that subtend nestedness analysis. We note two important conceptual problems that can lead to terminological inconsistencies and flawed interpretations. First, the thermodynamic analogy that underlies the most common metric of nestedness, matrix temperature, is flawed and has led some authors to incorrect interpretations. Second, the term "anti-nestedness" is a potential source of confusion and inconsistencies. We review four concepts for anti-nestedness and examine how distinct they are. "Anti-nested" matrices, i.e. less nested than expected by chance, may result from different ecological processes and show distinct structural patterns. Thus, there is no single unequivocal opposite of nestedness to be represented as "anti-nestedness". A more profitable approach is to designate and test each distinct non-nested pattern according to its specific assumptions and mechanistic hypotheses.

Evolution and the latitudinal diversity gradient: speciation, extinction and biogeography

Mittelbach — 2007-03-14T13:45:13-00:00

Ecology Letters, Vol. 10, No. 4. (April 2007), pp. 315-331.

Pollination and other ecosystem services produced by mobile organisms: a conceptual framework for the effects of land-use change

Kremen — 2007-03-14T13:45:13-00:00

Ecology Letters, Vol. 10, No. 4. (April 2007), pp. 299-314.

Molecular phylogeny and biogeography of an ancient Holarctic lineage of mygalomorph spiders (Araneae: Antrodiaetidae: Antrodiaetus).

Brent E Hendrixson — 2006-12-06T18:51:43-00:00

Mol Phylogenet Evol (27 September 2006)

The mygalomorph spider genera Antrodiaetus and Atypoides (Antrodiaetidae) belong to an ancient lineage that has persisted since at least the Cretaceous. These spiders display a classic disjunct Holarctic distribution with species in the eastern Palaearctic plus the western and eastern Nearctic. Prior phylogenetic analyses of this group have been proposed on the basis of morphology, but lack strong support and independent corroboration. Here we present the first phylogenetic analysis of species-level relationships based on molecular data obtained from the mitochondrial (cytochrome c oxidase subunit I) and nuclear (18S and 28S rRNA) genomes. Analyses corroborate earlier findings that Atypoides forms a paraphyletic grade with respect to Antrodiaetus, and consequently, that genus is formally synonymized under Antrodiaetus. In addition, our results support the relatively early divergence of Antrodiaetus roretzi. Antrodiaetus pacificus is "paraphyletic" with respect to the A. lincolnianus group and is likely an assemblage of numerous species. The final topology based on a combined molecular dataset, in conjunction with two different molecular dating techniques (penalized likelihood plus a Bayesian approach) and ancestral distribution reconstructions, was used to infer the historical biogeography of these spiders. Trans-Beringian and trans-Atlantic routes appear to account for the present-day distribution of Antrodiaetus in Japan and North America. Future studies on Antrodiaetus phylogeny will be used to address questions regarding morphological stasis and the evolution of quantitative morphological characters.

M. A. McPeek and J. M. Brown, Species Richness among Animal Taxa

2007-03-09T20:46:49-00:00

From the Cover: Compensatory dynamics are rare in natural ecological communities

JE Houlahan — 2007-02-27T19:47:40-00:00

PNAS, Vol. 104, No. 9. (27 February 2007), pp. 3273-3277.

In population ecology, there has been a fundamental controversy about the relative importance of competition-driven (density-dependent) population regulation vs. abiotic influences such as temperature and precipitation. The same issue arises at the community level; are population sizes driven primarily by changes in the abundances of cooccurring competitors (i.e., compensatory dynamics), or do most species have a common response to environmental factors? Competitive interactions have had a central place in ecological theory, dating back to Gleason, Volterra, Hutchison and MacArthur, and, more recently, Hubbell's influential unified neutral theory of biodiversity and biogeography. If competitive interactions are important in driving year-to-year fluctuations in abundance, then changes in the abundance of one species should generally be accompanied by compensatory changes in the abundances of others. Thus, one necessary consequence of strong compensatory forces is that, on average, species within communities will covary negatively. Here we use measures of community covariance to assess the prevalence of negative covariance in 41 natural communities comprising different taxa at a range of spatial scales. We found that species in natural communities tended to covary positively rather than negatively, the opposite of what would be expected if compensatory dynamics were important. These findings suggest that abiotic factors such as temperature and precipitation are more important than competitive interactions in driving year-to-year fluctuations in species abundance within communities. 10.1073/pnas.0603798104

The Agricultural Matrix and a Future Paradigm for Conservation

John Vandermeer — 2007-02-12T00:57:49-00:00

Conservation Biology, Vol. 21, No. 1. (February 2007), pp. 274-277.

Effect of Human Disturbance on Bee Communities in a Forested Ecosystem

Rachael Winfree — 2007-02-12T00:57:53-00:00

Conservation Biology, Vol. 21, No. 1. (February 2007), pp. 213-223.

Genome size and recombination in angiosperms: a second look

J Ross-Ibarra — 2007-02-18T06:12:02-00:00

Journal of Evolutionary Biology, Vol. 20, No. 2. (2007), pp. 800-806.

Abstract Despite dramatic differences in genome size - and thus space for recombination to occur - previous workers found no correlation between recombination rate and genome size in flowering plants. Here I re-investigate these claims using phylogenetic comparative methods to test a large data set of recombination data in angiosperms. I show that genome size is significantly correlated with recombination rate across a wide sampling of species and that change in genome size explains a meaningful proportion (~20%) of variation in recombination rate. I show that the strength of this correlation is comparable with that of several characters previously linked to evolutionary change in recombination rate, but argue that consideration of processes of genome size change likely make the observed correlation a conservative estimate. And finally, although I find that recombination rate increases less than proportionally to change in genome size, several mechanistic and theoretical arguments suggest that this result is not unexpected.

Schmeissneria: A missing link to angiosperms?

Xin Wang — 2007-02-07T20:46:38-00:00

BMC Evolutionary Biology, Vol. 7 (07 February 2007), 14.

Polyploidy and self-compatibility: is there an association?

Barbara Mable — 2007-02-08T23:28:22-00:00

New Phytologist, Vol. 162, No. 3. (2004), pp. 803-811.

Summary . Researchers have hypothesized that self-compatibility (SC) should be more common in polyploid taxa than their diploid counterparts because of selection for reproductive assurance and/or the expected decline in inbreeding depression associated with having 'extra' gene copies. Support for this view has come from an observed breakdown of self-incompatibility (SI) in some species with a gametophytic system (GSI). The purpose of this research was to assess the strength of this relationship across a wider array of SI systems. . A large database, of diploid chromosome numbers, ploidy levels, and types of SI system, was assembled for angiosperm species and used to test for an association between ploidy and SC. . No strong association was found between SC and polyploidy at the level of species or families, and there was no evidence that those having a functional SI system also had fewer polyploid taxa or that most polyploids experience a breakdown in SI. . These results challenge the assumption that self-fertilization is strongly associated with polyploidy and suggest directions for further research on the evolution of polyploidy in relation to SI. cNew Phytologist (2004) doi: 10.1111/j.1469-8137.2004.01055.x

Agri-environment schemes as a tool for reversing declining populations of grassland waders: Mixed benefits from Environmentally Sensitive Areas in England

Andy Wilson — 2007-02-01T01:07:35-00:00

Biological Conservation, Vol. 136, No. 1. (April 2007), pp. 128-135.

Agri-environment schemes (AES) are a key tool in attempts to reverse long-term declines in farmland biodiversity within the European Union (EU). Approximately 20% of EU farmland is under AES agreement, at a cost of over [euro]24 billion between 1994 and 2003. Despite this huge investment, few studies have investigated the effectiveness of schemes and those studies that do exist have often been inadequately designed or analysed. In southern England, repeat censuses of lowland breeding waders provide a rare opportunity to evaluate effectiveness of the Environmentally Sensitive Areas scheme (ESA), an AES designed with broad environmental objectives, including the maintenance or enhancement of the populations of these birds. The censuses provide a quasi-experimental approach, allowing a comparison to be made of breeding population trends of three species, Lapwing, Redshank and Snipe, on scheme and non-scheme land. The results show mixed success. For all three species, population trends were most favourable (increasing or declining less rapidly) in the more expensive ESA options aimed at enhancing habitat; the less expensive, habitat maintenance options, appear to have little benefit for Lapwing and Snipe, although Redshank has benefited. The results also show the increasing importance of nature reserves for these species in southern England. We suggest that although AES can result in significant benefits, especially when monetary investment is high, delivery of biodiversity targets are by no means guaranteed.

Evaluating cost-effectiveness of conservation management actions in an agricultural landscape on a regional scale

Annelie Holzkamper — 2007-02-01T01:07:35-00:00

Biological Conservation, Vol. 136, No. 1. (April 2007), pp. 117-127.

Agricultural landscapes are the dominating landscape types in many parts of the world. Land-use intensification and spatial homogeneity are major threats to biodiversity in these landscapes. Thus cost-effective strategies for species conservation in large-scale agricultural landscapes are required. Spatial optimisation methods can be applied to identify the most effective allocation of a given budget for conservation. However, the optimisation of spatial land-use patterns in real landscapes on a large spatial scale is often limited by computational power. In this paper, we present a simplifying methodology for analysing cost-effectiveness of management actions on a regional scale. A spatially explicit optimisation approach is employed to identify optimum agricultural land-use patterns with respect to an ecological-economic goal function. Based on the optimisation results for small scale landscape samples we derive a target- and site-specific cost-benefit function that can be applied to predict ecological improvement as a function of costs and local conditions on a large spatial scale. Thus, it is possible to identify areas where management actions for ecological improvement are most efficient with respect to a certain conservation goal. The fitted function is validated independently. In a case study, we analyse cost-effectiveness of management actions to enhance habitat suitability for three different target species. The approach is flexible and could be applied to a variety of other landscape planning problems dealing with the effective allocation of management measures.

From selection to complementarity: shifts in the causes of biodiversity–productivity relationships in a long-term biodiversity experiment

Joseph Fargione — 2007-02-01T01:05:18-00:00

Proceedings of the Royal Society B: Biological Sciences, Vol. 274 (2007), pp. 871-876.

In a 10-year (1996–2005) biodiversity experiment, the mechanisms underlying the increasingly positive effect of biodiversity on plant biomass production shifted from sampling to complementarity over time. The effect of diversity on plant biomass was associated primarily with the accumulation of higher total plant nitrogen pools (Ngm−2) and secondarily with more efficient N use at higher diversity. The accumulation of N in living plant biomass was significantly increased by the presence of legumes, C4 grasses, and their combined presence. Thus, these results provide clear evidence for the increasing effects of complementarity through time and suggest a mechanism whereby diversity increases complementarity through the increased input and retention of N, a commonly limiting nutrient.

Macroevolution of plant defense strategies

Anurag Agrawal — 2007-01-27T20:49:42-00:00

Trends in Ecology & Evolution, Vol. 22, No. 2. (February 2007), pp. 103-109.

Theories of plant defense expression are typically based on the concepts of tradeoffs among traits and of phylogenetic conservatism within clades. Here, I review recent developments in phylogenetic approaches to understanding the evolution of plant defense strategies and plant-herbivore coevolutionary interactions. I focus particularly on multivariate defense against insect herbivores, which is the simultaneous deployment of multiple traits, often arranged as convergently evolved defense syndromes. Answering many of the outstanding questions in the biology of plant defense will require generating broad hypotheses that can be explicitly tested by using comparative approaches and interpreting phylogenetic patterns. The comparative approach has wide-spread potential to reinvigorate tests of classic hypotheses about the evolution of interspecific interactions.

Floral Conservatism in Neotropical Malpighiaceae

William Anderson — 2007-01-27T20:49:04-00:00

Biotropica, Vol. 11, No. 3. (1979), pp. 219-223.

Over 950 species of Malpighiaceae grow in a variety of neotropical habitats and have evolved great diversity in habit, fruit, pollen, and chromosome number. Their flowers, in contrast, tend to be very similar in general architecture, especially in those aspects concerned with the attraction, orientation, and reward of pollinators. The flowers are visited only by Hymenoptera, principally female anthophorid bees and trigonid bees. The anthophorids collect oil from the calyx glands, mix it with pollen, and use the mixture as food for their larvae. The trigonids collect pollen. The usual character-syndrome of the flower seems to be related to and maintained by pollination by oil-bees, and was probably ancestral in the family. Pollination by pollen-collecting bees is probably secondary in many genera and has shifted to primary importance in groups that have lost the calyx glands. Other families such as Polemoniaceae, which have evolved very diverse flowers, reward pollinators with a sugary nectar that attracts a variety of secondary pollinators. This faunal diversity provides a bridge between one character-syndrome in the flowers and another. The specialized rewards and resulting lack of diversity in pollinators in neotropical Malpighiaceae explain why the flowers have remained so conservative in spite of the evolution of great diversity in other aspects of the phenotype. Calyx glands seem to have been lost in most paleotropical lines in the absence of oil-bees, but field observations on the pollination of those plants are practically nonexistent.

BIOONE Online Journals - PHYLOGENY, CONCERTED CONVERGENCE, AND PHYLOGENETIC NICHE CONSERVATISM IN THE CORE LILIALES: INSIGHTS FROM rbcL AND ndhF SEQUENCE DATA

2007-01-27T20:46:04-00:00

Diversity in agricultural and forest entomology

Watt — 2007-01-25T23:16:06-00:00

Agricultural and Forest Entomology, Vol. 9, No. 1. (February 2007), pp. 1-1.

Linkage Rules for Plant–Pollinator Networks: Trait Complementarity or Exploitation Barriers?

Luis Santamaría — 2007-01-24T01:24:52-00:00

PLoS Biology, Vol. 5, No. 2. (1 February 2007), e31.

Recent attempts to examine the biological processes responsible for the general characteristics of mutualistic networks focus on two types of explanations: nonmatching biological attributes of species that prevent the occurrence of certain interactions (“forbidden links”), arising from trait complementarity in mutualist networks (as compared to barriers to exploitation in antagonistic ones), and random interactions among individuals that are proportional to their abundances in the observed community (“neutrality hypothesis”). We explored the consequences that simple linkage rules based on the first two hypotheses (complementarity of traits versus barriers to exploitation) had on the topology of plant–pollination networks. Independent of the linkage rules used, the inclusion of a small set of traits (two to four) sufficed to account for the complex topological patterns observed in real-world networks. Optimal performance was achieved by a “mixed model” that combined rules that link plants and pollinators whose trait ranges overlap (“complementarity models”) and rules that link pollinators to flowers whose traits are below a pollinator-specific barrier value (“barrier models”). Deterrence of floral parasites (barrier model) is therefore at least as important as increasing pollination efficiency (complementarity model) in the evolutionary shaping of plant–pollinator networks.

Rapid evolution of flowering time by an annual plant in response to a climate fluctuation

Steven Franks — 2007-01-23T19:28:38-00:00

PNAS, Vol. 104, No. 4. (23 January 2007), pp. 1278-1282.

Ongoing climate change has affected the ecological dynamics of many species and is expected to impose natural selection on ecologically important traits. Droughts and other anticipated changes in precipitation may be particularly potent selective factors, especially in arid regions. Here we demonstrate the evolutionary response of an annual plant, Brassica rapa, to a recent climate fluctuation resulting in a multiyear drought. Ancestral (predrought) genotypes were recovered from stored seed and raised under a set of common environments with descendant (postdrought) genotypes and with ancestorxdescendant hybrids. As predicted, the abbreviated growing seasons caused by drought led to the evolution of earlier onset of flowering. Descendants bloomed earlier than ancestors, advancing first flowering by 1.9 days in one study population and 8.6 days in another. The intermediate flowering time of ancestorxdescendant hybrids supports an additive genetic basis for divergence. Experiments confirmed that summer drought selected for early flowering, that flowering time was heritable, and that selection intensities in the field were more than sufficient to account for the observed evolutionary change. Natural selection for drought escape thus appears to have caused adaptive evolution in just a few generations. A systematic effort to collect and store propagules from suitable species would provide biologists with materials to detect and elucidate the genetic basis of further evolutionary shifts driven by climate change. 10.1073/pnas.0608379104

beetles

Vamosi — 2007-01-19T23:29:55-00:00

diversity and Distribution

Farmland Biodiversity and the Footprint of Agriculture

SJ Butler — 2007-01-19T19:21:09-00:00

Science, Vol. 315, No. 5810. (19 January 2007), pp. 381-384.

Sustainable development requires the reconciliation of demands for biodiversity conservation and increased agricultural production. Assessing the impact of novel farming practices on biodiversity and ecosystem services is fundamental to this process. Using farmland birds as a model system, we present a generic risk assessment framework that accurately predicts each species' current conservation status and population growth rate associated with past changes in agriculture. We demonstrate its value by assessing the potential impact on biodiversity of two controversial land uses, genetically modified herbicide-tolerant crops and agri-environment schemes. This framework can be used to guide policy and land management decisions and to assess progress toward sustainability targets. 10.1126/science.1136607

Learning in the context of sexual behaviour in insects

Reuven Dukas — 2007-01-18T23:16:42-00:00

Animal Biology (formerly Netherlands Journal of Zoology), Vol. V56, No. 2. (26 April 2006), pp. 125-141.

Learning in insects: From behaviour to brain

Hans Smid — 2007-01-18T23:16:13-00:00

Animal Biology (formerly Netherlands Journal of Zoology), Vol. V56, No. 2. (26 April 2006), pp. 121-124.

A climate-change risk analysis for world ecosystems

Marko Scholze — 2007-01-18T23:15:14-00:00

PNAS, Vol. 103, No. 35. (29 August 2006), pp. 13116-13120.

We quantify the risks of climate-induced changes in key ecosystem processes during the 21st century by forcing a dynamic global vegetation model with multiple scenarios from 16 climate models and mapping the proportions of model runs showing forest/nonforest shifts or exceedance of natural variability in wildfire frequency and freshwater supply. Our analysis does not assign probabilities to scenarios or weights to models. Instead, we consider distribution of outcomes within three sets of model runs grouped by the amount of global warming they simulate: <2degreesC (including simulations in which atmospheric composition is held constant, i.e., in which the only climate change is due to greenhouse gases already emitted), 2-3degreesC, and >3degreesC. High risk of forest loss is shown for Eurasia, eastern China, Canada, Central America, and Amazonia, with forest extensions into the Arctic and semiarid savannas; more frequent wildfire in Amazonia, the far north, and many semiarid regions; more runoff north of 50degreesN and in tropical Africa and northwestern South America; and less runoff in West Africa, Central America, southern Europe, and the eastern U.S. Substantially larger areas are affected for global warming >3degreesC than for <2degreesC; some features appear only at higher warming levels. A land carbon sink of approx1 Pg of C per yr is simulated for the late 20th century, but for >3degreesC this sink converts to a carbon source during the 21st century (implying a positive climate feedback) in 44% of cases. The risks continue increasing over the following 200 years, even with atmospheric composition held constant. 10.1073/pnas.0601816103

Microarthropods Mediate Sperm Transfer in Mosses

Nils Cronberg — 2007-01-18T22:55:18-00:00

Science, Vol. 313, No. 5791. (1 September 2006), 1255.

Among flowering plants, animals commonly act as pollinators. We showed that fertile moss shoots attract springtails and mites, which in turn carry moss sperm, thereby enhancing the fertilization process. Previously, fertilization of mosses was thought to depend on the capacity of individual sperm to swim through a continuous water layer. The role of microarthropods in moss fertilization resembles the role of animals as pollinators of flowering plants but may be evolutionarily much older because of the antiquity of the organism groups involved. 10.1126/science.1128707

Corridors Increase Plant Species Richness at Large Scales

Ellen Damschen — 2007-01-18T22:53:18-00:00

Science, Vol. 313, No. 5791. (1 September 2006), pp. 1284-1286.

Habitat fragmentation is one of the largest threats to biodiversity. Landscape corridors, which are hypothesized to reduce the negative consequences of fragmentation, have become common features of ecological management plans worldwide. Despite their popularity, there is little evidence documenting the effectiveness of corridors in preserving biodiversity at large scales. Using a large-scale replicated experiment, we showed that habitat patches connected by corridors retain more native plant species than do isolated patches, that this difference increases over time, and that corridors do not promote invasion by exotic species. Our results support the use of corridors in biodiversity conservation. 10.1126/science.1130098

A total evidence assessment of the phylogeny of North American euctenizine trapdoor spiders (Araneae, Mygalomorphae, Cyrtaucheniidae) using Bayesian inference

Jason Bond — 2007-01-18T22:44:07-00:00

Molecular Phylogenetics and Evolution, Vol. 41, No. 1. (October 2006), pp. 70-85.

North American trapdoor spiders of the subfamily Euctenizinae (Cyrtaucheniidae) are among the most diverse mygalomorph spiders (trapdoor spiders, tarantulas, and their relatives) on the continent in terms of species numbers and ecological habits. We present a generic level phylogenetic study of the subfamily based on a total evidence approach. Our dataset comprises ~3.7 kb of molecular characters (18S and 28S rRNA gene sequences) and 71 morphological characters scored for 32 taxa. When analyzed independently, these data sets, particularly the morphology, depict very different views of mygalomorph and euctenizine relationships, albeit with weak support. However, when these data are combined we recover a tree topology that is supported by high posterior probability for most nodes. The combined data recover a phylogenetic pattern for euctenizines different than previously published and indicate the presence of a narrowly endemic new genus from central California. While euctenizine monophyly is unequivocal, the monophyly of a number of other mygalomorph groups is questionable (e.g., Cyrtaucheniidae, Mecicobothriodina, Rastelloidina). This non-monophyly is noteworthy, as our analysis represents the first employing a total evidence approach for mygalomorphs, a group known to be morphologically conservative.

Conservatism of ecological niche characteristics in North American plant species over the Pleistocene-to-Recent transition

Martinez-Meyer — 2006-09-08T08:30:30-00:00

Journal of Biogeography, Vol. 33, No. 10. (October 2006), pp. 1779-1789.

Declines in forage availability for bumblebees at a national scale

Claire Carvell — 2007-01-18T21:45:10-00:00

Biological Conservation, Vol. 132, No. 4. (October 2006), pp. 481-489.

We assessed national scale changes in the forage plants of bumblebees in Britain, as a means of providing quantitative evidence for the likely principal cause of declines in bumblebee species. We quantified the relative value of native and long-established plant species as forage (nectar and pollen) resources for bumblebees by collating visitation data from 14 field sites across Britain. Twentieth Century changes in range and frequency of these forage plants were assessed using data from the New Atlas of the British and Irish Flora (1930-1969 to 1987-1999) and the Countryside Surveys of Britain (1978-1998). Forage plants declined in both large-scale range and local-scale frequency between the two survey periods. These changes were of greater magnitude than changes in other native plant species, reflecting serious reductions in quality of foraging habitats for bees as well as a general decline in insect-pollinated plants. Seventy-six percent of forage plants declined in frequency within 1-km squares, including those (e.g. Trifolium pratense) of particular value for threatened bumblebee species. We consider how our findings relate to other recorded changes in the British flora, how they may help to explain declines in bumblebees and how they could contribute to a conservation strategy.

MACROEVOLUTIONARY DATA SUGGEST A ROLE FOR REINFORCEMENT IN POLLINATION SYSTEM SHIFTS

Timotheüs van der Niet — 2007-01-18T21:40:29-00:00

Evolution, Vol. 60 (2006), pp. 1596-1601.

Reproductive isolation can evolve either as a by-product of divergent selection or through reinforcement. We used the Cape flora of South Africa, known for its high level of pollination specialization, as a model system to test the potential role of shifts in pollination system in the speciation process. Comparative analysis of 41 sister-species pairs (representing Geraniaceae, Iridaceae, and Orchidaceae) for which complete pollinator, edaphic, and distribution data are available showed that for sister species with overlapping distribution ranges, pollination system shifts are significantly associated with edaphic shifts. In contrast, there is no significant association between pollination system shifts and edaphic shifts for allopatric sister species. These results are interpreted as evidence for reinforcement.

Shaping global environmental decisions using socio-ecological models

Heather Tallis — 2007-01-18T20:49:28-00:00

Trends in Ecology & Evolution, Vol. 21, No. 10. (October 2006), pp. 562-568.

One of the most ambitious ecological studies of the past few decades was the Millennium Ecosystem Assessment (MA), which examined the consequences of ecosystem change for human well-being. The MA developed global ecological scenarios as a process to inform policy options, despite enormous uncertainties. These scenarios were based on an interlocking suite of models that forecast the future. Following the recent completion and publication of the MA, there is now movement towards making the value of ecosystem services an integral part of key policy decisions. Here, we review the MA approach and suggest areas where immediate progress can be made to increase the likelihood that decision-makers will embrace the vision of assessments such as the MA.

Pathways to mutualism breakdown

Joel Sachs — 2007-01-18T20:47:16-00:00

Trends in Ecology & Evolution, Vol. 21, No. 10. (October 2006), pp. 585-592.

Mutualisms are ubiquitous in nature despite the widely held view that they are unstable interactions. Models predict that mutualists might often evolve into parasites, can abandon their partners to live autonomously and are also vulnerable to extinction. Yet a basic empirical question, whether mutualisms commonly break down, has been mostly overlooked. As we discuss here, recent progress in molecular systematics helps address this question. Newly constructed phylogenies reveal that parasites as well as autonomous (non-mutualist) taxa are nested within ancestrally mutualistic clades. Although models have focused on the propensity of mutualism to become parasitic, such shifts appear relatively rarely. By contrast, diverse systems exhibit reversions to autonomy, and this might be a common and unexplored endpoint to mutualism.

Emergent neutrality

Robert Holt — 2007-01-18T20:33:13-00:00

Trends in Ecology & Evolution, Vol. 21, No. 10. (October 2006), pp. 531-533.

Community ecology is in a current state of creative ferment, stimulated by the development of neutral models of community organization. Here, I reflect on recent papers by Scheffer and van Nes, and by Gravel et al., which illuminate how neutrality can emerge from ecological and evolutionary processes, thus suggesting ways to unify neutral and niche perspectives.

Wild bee species increase tomato production and respond differently to surrounding land use in Northern California

Sarah Greenleaf — 2007-01-18T20:22:10-00:00

Biological Conservation, Vol. 133, No. 1. (November 2006), pp. 81-87.

Pollination provided by bees enhances the production of many crops. However, the contribution of wild bees remains unmeasured for many crops, and the effects of anthropogenic change on many bee species are unstudied. We experimentally investigated how pollination by wild bees affects tomato production in northern California. We found that wild bees substantially increase the production of field-grown tomato, a crop generally considered self-pollinating. Surveys of the bee community on 14 organic fields that varied in proximity to natural habitat showed that the primary bee visitors, Anthophora urbana Cresson and Bombus vosnesenskii Radoszkowski, were affected differently by land management practices. B. vosnesenskii was found primarily on farms proximate to natural habitats, but neither proximity to natural habitat nor tomato floral abundance, temperature, or year explained variation in the visitation rates of A. urbana. Natural habitat appears to increase B. vosnesenskii populations and should be preserved near farms. Additional research is needed to determine how to maintain A. urbana. Species-specific differences in dependency on natural habitats underscore the importance of considering the natural histories of individual bee species when projecting population trends of pollinators and designing management plans for pollination services. Thus, to maintain an entire bee community, multiple approaches, including maintaining natural habitat, should be implemented.

Natural Selection on Erysimum mediohispanicum Flower Shape: Insights into the Evolution of Zygomorphy

José Gómez — 2007-01-18T20:19:31-00:00

The American Naturalist, Vol. 168 (2006), pp. 531-545.

Paleontological and phylogenetic studies have shown that floral zygomorphy (bilateral symmetry) has evolved independently in several plant groups from actinomorphic (radially symmetric) ancestors as a consequence of strong selection exerted by specialized pollinators. Most studies focused on unraveling the developmental genetics of flower symmetry, but little is known about the adaptive significance of intraspecific flower shape variation under natural conditions. We provide the first evidence for natural selection favoring zygomorphy in a wild population of Erysimum mediohispanicum (Brassicaceae), a plant showing extensive continuous variation in flower shape, ranging from actinomorphic to zygomorphic flowers. By using geometric morphometric tools to describe flower shape, we demonstrate that plants bearing zygomorphic flowers received more pollinator visits and had the highest fitness, measured not only by the number of seeds produced per plant but also by the number of seeds surviving to the juvenile stage. This study provides strong evidence for the existence of significant fitness differences associated with floral shape variation in E. mediohispanicum, thus illuminating a pathway for the evolution of zygomorphy in natural populations.

Impact of Criticism of Null-Hypothesis Significance Testing on Statistical Reporting Practices in Conservation Biology

Fiona Fidler — 2006-09-23T20:41:50-00:00

Conservation Biology, Vol. 20, No. 5. (October 2006), pp. 1539-1544.