Phenotypic selection exerted by a seed predator is replicated in space and time and among prey species

Although consistent phenotypic selection arising from biotic interactions is thought to be the primary cause of adaptive diversification, studies documenting such selection are relatively few. Here we analyze 12 episodes of phenotypic selection exerted by a predispersal seed predator, the red crossbill (Loxia curvirostra complex), on five species of pines (Pinus). We find that even though the intensity of selection for some traits increased with the strength of the interaction (i.e., proportion of seeds eaten), the relative strength of selection exerted by crossbills on cone and seed traits is replicated across space and time and among species. Such selection (1) can account for repeated patterns of conifer cone evolution and escalation in seed defenses with time and (2) suggests that variation in selection is less the result of variation intrinsic to pairwise biotic interactions than, for example, variation in relative densities of the interacting species, community context, and abiotic factorsNational Science Foundation (DEB-0212271 and DEB-0344503), the Robert B. Berry Endowed Chair, and the Ministry of Science and Innovation of Spain (CGL2010- 15687) for financial support for our researc

Forest and cone structure influence where crossbills forage in a managed Scots pine forest

The structure of forests is a fundamental attribute that impacts biodiversity and ecosystem services and in turn is influenced by natural disturbances and management practices. Here, we examine spatial variation in the interaction between a specialized predispersal seed predator, common crossbills (Loxia curvirostra), and Scots pine (Pinus sylvestris) in relation to forest structure and tree features in a managed Mediterranean forest. Crossbills preferred to forage in pine stands that were more open, which correspond to older stands or regeneration stands with scattered old seed trees. More open older stands with larger trees tend to produce more cones that are attractive to crossbills, although their use was also consistent with crossbills reducing their risk of predation. Within these patches, crossbills selectively foraged on trees having many small, thin-scaled cones, which require less effort and time to extract the seeds. Crossbills were apparently limited to only a very small subset of the closed Scots pine cones because they have relatively small and ineffective bills for foraging on Scots pine. Given that crossbills foraged on only a small subset of the cones within more open stands, a management strategy that would aid common crossbills is to thin middle-aged stands. This would accelerate the development of older stand structure, which would benefit crossbills by increasing the occurrence of suitably open woodlands, benefit other species that rely on older more open stand structure, and potentially decrease the vulnerability of the forest to fire and droughtWe thank C. Ferrini, E. García and P. Acebes for field assistance, P. Edelaar and R. Summers for helpful comments on the manuscript, and Centro de Montes y Aserradero de Valsaín (Organismo Autónomo de Parques Nacionales) for providing information and the LiDAR data. The REMEDINAL 3-CM research network (S2013/mae-2719) partially funded this research. ETM was supported by “Convenio Comunidad de Madrid y Universidad Autónoma de Madrid en Línea 3: Excelencia del Profesorado Universitario” during the writing and publication process

Transcriptome sequencing in an ecologically important tree species: assembly, annotation, and marker discovery

<p>Abstract</p> <p>Background</p> <p>Massively parallel sequencing of cDNA is now an efficient route for generating enormous sequence collections that represent expressed genes. This approach provides a valuable starting point for characterizing functional genetic variation in non-model organisms, especially where whole genome sequencing efforts are currently cost and time prohibitive. The large and complex genomes of pines (<it>Pinus </it>spp.) have hindered the development of genomic resources, despite the ecological and economical importance of the group. While most genomic studies have focused on a single species (<it>P. taeda</it>), genomic level resources for other pines are insufficiently developed to facilitate ecological genomic research. Lodgepole pine (<it>P. contorta</it>) is an ecologically important foundation species of montane forest ecosystems and exhibits substantial adaptive variation across its range in western North America. Here we describe a sequencing study of expressed genes from <it>P. contorta</it>, including their assembly and annotation, and their potential for molecular marker development to support population and association genetic studies.</p> <p>Results</p> <p>We obtained 586,732 sequencing reads from a 454 GS XLR70 Titanium pyrosequencer (mean length: 306 base pairs). A combination of reference-based and <it>de novo </it>assemblies yielded 63,657 contigs, with 239,793 reads remaining as singletons. Based on sequence similarity with known proteins, these sequences represent approximately 17,000 unique genes, many of which are well covered by contig sequences. This sequence collection also included a surprisingly large number of retrotransposon sequences, suggesting that they are highly transcriptionally active in the tissues we sampled. We located and characterized thousands of simple sequence repeats and single nucleotide polymorphisms as potential molecular markers in our assembled and annotated sequences. High quality PCR primers were designed for a substantial number of the SSR loci, and a large number of these were amplified successfully in initial screening.</p> <p>Conclusions</p> <p>This sequence collection represents a major genomic resource for <it>P. contorta</it>, and the large number of genetic markers characterized should contribute to future research in this and other pines. Our results illustrate the utility of next generation sequencing as a basis for marker development and population genomics in non-model species.</p

Survival and population size of a resident bird species are declining as temperature increases

Summary 1. A large number of migratory bird species appear to be declining as the result of climate change, but whether resident bird species have or will be adversely affected by climate change is less clear. We focus on the South Hills crossbill (Loxia curvirostra complex), which is endemic to about 70 km 2 of Rocky Mountain lodgepole pine (Pinus contorta latifolia) forest in southern Idaho, USA. 2. Our results indicate that the South Hills crossbill has declined by over 60% between 2003 and 2008, and that decreasing adult survival drives this population decline. 3. We evaluated the relative support for multiple hypotheses linking crossbill survival to climate, an ectoparasitic mite (scaly-leg mites Knemidokoptes jamaicensis), and the recent emergence of West Nile virus. Changes in adult apparent survival rate were closely associated with average spring and annual temperatures, and with high temperatures ( ‡32°C) during summer, which have increased during the last decade. In contrast, there was little evidence that scaly-leg mites or West Nile virus contributed to recent declines in adult survival. 4. The most probable mechanism causing the decline in adult survival and population size is a decrease in the availability of their primary food resource, seeds in serotinous pine cones. Cone production has declined with increasing annual temperatures, and these cones appear to be prematurely opening owing to increasingly hot summer conditions releasing their seeds and reducing the carrying capacity for crossbills later in the year. 5. In light of regional climate change forecasts, which include an increase in both annual temperature and hot days (&gt;32°C), and the likely disappearance of lodgepole pine from southern Idaho by the end of this century, additional research is needed to determine how to maintain lodgepole pine forests and their supply of seeds to conserve one of the few bird species endemic to the continental United States

Do foraging methods in winter affect morphology during growth in juvenile snow geese?

Physical exertion during growth can affect ultimate size and density of skeletal structures. Such changes from different exercise regimes may explain morphological differences between groups, such as those exhibited by lesser snow geese (Chen caerulescens caerulescens; hereafter snow geese) foraging in southwest Louisiana. In rice-prairie habitats (hereafter rice-prairies), snow geese bite off or graze aboveground vegetation, whereas they dig or grub for subterranean plant parts in adjacent coastal marshes. Grubbing involves considerably more muscular exertion than does grazing. Thus, we hypothesized that rates of bone formation and growth would be lower for juveniles wintering in rice-prairies than those in coastal marshes, resulting in smaller bill and skull features at adulthood. First, we tested this exertion hypothesis by measuring bills, skulls, and associated musculature from arrival to departure (November-February) in both habitats in southwest Louisiana, using both banded birds and collected specimens. Second, we used the morphological data to test an alternative hypothesis, which states that smaller bill dimensions in rice-prairies evolved because of hybridization with Ross's geese (C.rossii). Under the exertion hypothesis, we predicted that bill and skull bones of juveniles would grow at different rates between habitats. However, we found that bill and skull bones of juveniles grew similarly between habitats, thus failing to support the exertion hypothesis. Morphometrics were more likely to differ by sex or change with sampling date than to differ by habitat. We predicted that significant, consistent skewness toward smaller birds could indicate hybridization with Ross's geese, but no skewness was observed in our morphological data, which fails to support the hybridization hypothesis. Further research is needed to clarify whether snow geese wintering in Louisiana represent a single polymorphic population that segregates into individually preferred habitats, which we believe at present to be more likely as an explanation than two ecologically and spatially distinct morphotypes.Canadian Wildlife Service, Louisiana Department of Wildlife and Fisheries (LDWF), Delta Waterfowl Foundation, Rockefeller Scholarship Program, USGS-Louisiana Cooperative Fish and Wildlife Research Unit, Graduate School; Agricultural Center, School of Renewable Natural Resources at Louisiana State UniversityPeer Reviewe

DOES NICHE DIVERGENCE ACCOMPANY ALLOPATRIC DIVERGENCE IN APHELOCOMA JAYS AS PREDICTED UNDER ECOLOGICAL SPECIATION?: INSIGHTS FROM TESTS WITH NICHE MODELS

The role of ecology in the origin of species has been the subject of long-standing interest to evolutionary biologists. New sources of spatially explicit ecological data allow for large-scale tests of whether speciation is associated with niche divergence or whether closely related species tend to be similar ecologically (niche conservatism). Because of the confounding effects of spatial autocorrelation of environmental variables, we generate null expectations for niche divergence for both an ecological-niche modeling and a multivariate approach to address the question: do allopatrically distributed taxa occupy similar niches? In a classic system for the study of niche evolution—the Aphelocoma jays—we show that there is little evidence for niche divergence among Mexican Jay ( A. ultramarina ) lineages in the process of speciation, contrary to previous results. In contrast, Aphelocoma species that exist in partial sympatry in some regions show evidence for niche divergence. Our approach is widely applicable to the many cases of allopatric lineages in the beginning stages of speciation. These results do not support an ecological speciation model for Mexican Jay lineages because, in most cases, the allopatric environments they occupy are not significantly more divergent than expected under a null model.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78650/1/j.1558-5646.2009.00900.x.pd

Molecular and cellular mechanisms underlying the evolution of form and function in the amniote jaw.

The amniote jaw complex is a remarkable amalgamation of derivatives from distinct embryonic cell lineages. During development, the cells in these lineages experience concerted movements, migrations, and signaling interactions that take them from their initial origins to their final destinations and imbue their derivatives with aspects of form including their axial orientation, anatomical identity, size, and shape. Perturbations along the way can produce defects and disease, but also generate the variation necessary for jaw evolution and adaptation. We focus on molecular and cellular mechanisms that regulate form in the amniote jaw complex, and that enable structural and functional integration. Special emphasis is placed on the role of cranial neural crest mesenchyme (NCM) during the species-specific patterning of bone, cartilage, tendon, muscle, and other jaw tissues. We also address the effects of biomechanical forces during jaw development and discuss ways in which certain molecular and cellular responses add adaptive and evolutionary plasticity to jaw morphology. Overall, we highlight how variation in molecular and cellular programs can promote the phenomenal diversity and functional morphology achieved during amniote jaw evolution or lead to the range of jaw defects and disease that affect the human condition

Diversity of floral visitors to sympatric Lithophragma species differing in floral morphology

Most coevolving relationships between pairs of species are embedded in a broader multispecific interaction network. The mutualistic interaction between Lithophragma parviflorum (Saxifragaceae) and its pollinating floral parasite Greya politella (Lepidoptera, Prodoxidae) occurs in some communities as a pairwise set apart from most other interactions in those communities. In other communities, however, this pair of species occurs with congeners and with other floral visitors to Lithophragma. We analyzed local and geographic differences in the network formed by interactions between Lithophragma plants and Greya moths in communities containing two Lithophragma species, two Greya species, and floral visitors other than Greya that visit Lithophragma flowers. Our goal was to evaluate if non-Greya visitors were common, if visitor assembly differs between Lithophragma species and populations and if these visitors act as effective pollinators. Sympatric populations of L. heterophyllum and L. parviflorum differ in floral traits that may affect assemblies of floral visitors. Visitation rates by non-Greya floral visitors were low, and the asymptotic number of visitor species was less than 20 species in all populations. Lithophragma species shared some of the visitors, with visitor assemblages differing between sites more for L. heterophyllum than for L. parviflorum. Pollination efficacy experiments showed that most visitors were poor pollinators. Single visits to flowers by this assemblage of species resulted in significantly higher seed set in Lithophragma heterophyllum (30.6 ± 3.9 SE) than in L. parviflorum (4.7 ± 3.4 SE). This difference was consistent between sites, suggesting that these visitors provide a better fit to the floral morphology of L. heterophyllum. Overall, none of the non-Greya visitors appears to be either sufficiently common or efficient as a pollinator to impose strong selection on any of these four Lithophragma populations in comparison with Greya, which occurs within almost all populations of these species throughout their geographic ranges