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In temperate rainforests on Chiloé Island in southern Chile (42°S), most canopy trees bear fleshy, avian‐dispersed propagules, whereas emergent tree species have dry, wind‐borne propagules. In the present study, the following hypothesis was tested: regardless of species, fleshy propagules are deposited in greater numbers in canopy gaps and in forest margins and hence have a more heterogeneous seed shadow than wind‐dispersed propagules. To test this hypothesis, the seed rains of these two types of propagules were compared in the following forest habitats: (i) tree‐fall gaps (edges and centre); (ii) forest margins with adjacent pastures; and (iii) under closed canopy (forest interior). Seed collectors (30‐cm diameter) were placed in two (15 and 100 ha) remnant forest patches (n = 60–100 seed collectors per patch) distributed in the four habitats. Seeds were retrieved monthly from each collector during two reproductive seasons (1996, 1997). In both years, the seed rain was numerically dominated by two species with dry propagules (Laureliopsis philippiana and Nothofagus nitida) and three species with fleshy fruits (Drimys winteri, Amomyrtus luma, and Amomyrtus meli). The seed shadows of the two species with dry, wind‐dispersed seeds differed markedly. Seeds of L. philippiana were deposited predominantly in canopy openings, whereas N. nitida seeds fell almost entirely in the forest interior. The fleshy‐fruited species, Drimys and Amomyrtus spp., had similar seed deposition patterns in the various habitats studied, but the between‐year differences in seed rain were greater in Drimys winteri than in Amomyrtus spp. Although no more than 10% of fleshy‐fruited propagules reached the margins of the patch, approximately 7% of these were carried there by birds. Every year, canopy gaps (pooling data from edges and centres) concentrated approximately 60% of the total seed rain of both propagule types in both forest patches. Forest margins received less than 20% of the total seed rain, which was largely dominated by fleshy‐fruited species. Seed shadows were a species‐specific attribute rather than a trait associated with propagule type and dispersal mode. 相似文献
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Mairi Sime Amanda C. Allan Paul Chapman Charlotte Fieldhouse Gerard M.P. Giblin Mark P. Healy Millard H. Lambert Lisa M. Leesnitzer Ann Lewis Raymond V. Merrihew Richard A. Rutter Rosemary Sasse Barry G. Shearer Timothy M. Willson Robert X. Xu David J. Virley 《Bioorganic & medicinal chemistry letters》2013,23(4):1143
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Stephen J. Willson 《Bulletin of mathematical biology》2013,75(10):1840-1878
Trees are commonly utilized to describe the evolutionary history of a collection of biological species, in which case the trees are called phylogenetic trees. Often these are reconstructed from data by making use of distances between extant species corresponding to the leaves of the tree. Because of increased recognition of the possibility of hybridization events, more attention is being given to the use of phylogenetic networks that are not necessarily trees. This paper describes the reconstruction of certain such networks from the tree-average distances between the leaves. For a certain class of phylogenetic networks, a polynomial-time method is presented to reconstruct the network from the tree-average distances. The method is proved to work if there is a single reticulation cycle. 相似文献
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Edmond M. Linossi Indu R. Chandrashekaran Tatiana B. Kolesnik James M. Murphy Andrew I. Webb Tracy A. Willson Lukasz Kedzierski Alex N. Bullock Jeffrey J. Babon Raymond S. Norton Nicos A. Nicola Sandra E. Nicholson 《PloS one》2013,8(8)
Suppressor of Cytokine Signaling (SOCS)5 is thought to act as a tumour suppressor through negative regulation of JAK/STAT and epidermal growth factor (EGF) signaling. However, the mechanism/s by which SOCS5 acts on these two distinct pathways is unclear. We show for the first time that SOCS5 can interact directly with JAK via a unique, conserved region in its N-terminus, which we have termed the JAK interaction region (JIR). Co-expression of SOCS5 was able to specifically reduce JAK1 and JAK2 (but not JAK3 or TYK2) autophosphorylation and this function required both the conserved JIR and additional sequences within the long SOCS5 N-terminal region. We further demonstrate that SOCS5 can directly inhibit JAK1 kinase activity, although its mechanism of action appears distinct from that of SOCS1 and SOCS3. In addition, we identify phosphoTyr317 in Shc-1 as a high-affinity substrate for the SOCS5-SH2 domain and suggest that SOCS5 may negatively regulate EGF and growth factor-driven Shc-1 signaling by binding to this site. These findings suggest that different domains in SOCS5 contribute to two distinct mechanisms for regulation of cytokine and growth factor signaling. 相似文献
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Ethan J. Royal Daniel U. Greene Darren A. Miller John D. Willson 《The Journal of wildlife management》2022,86(3):e22199
Longleaf pine (Pinus palustris) savanna characterized by open-canopy, diverse herbaceous vegetation, and high amounts of bare soil once covered much of the southeastern United States Coastal Plain. The unique structural and vegetative conditions of this ecosystem support endemic reptiles and amphibians that have declined as longleaf pine forests have been lost or degraded. Private working pine (Pinus spp.) forests managed for timber production now occur throughout the southeastern United States and have replaced much of the historical longleaf pine savanna. The examination of herpetofaunal (reptile, amphibian) communities in private working loblolly pine (P. taeda) landscapes, particularly in the western Gulf Coastal Plain is lacking. Using repeated field surveys and hierarchical community occupancy models, we examined occupancy and species richness of herpetofauna across 81 sites spanning gradients of management practices, vegetative conditions, and soil composition in northwestern Louisiana, USA, 2017–2019. Young pine stands (<6 yr) exhibited structural characteristics most similar to mature longleaf pine reference sites (>30 yr), while mid-aged stands (13–26 yr) often featured closed canopy and dense midstory. Vegetation conditions varied widely depending on landscape characteristics and site-specific disturbance regimes. We documented 43 species of herpetofauna, including 9 open-pine-associated species. Occupancy of open-pine-associated herpetofauna was positively associated with open-canopy and understory conditions, and sandy soil area. Sites providing open-canopy conditions were often occupied by open-pine-associated species regardless of overstory type and disturbance method. Overall richness of herpetofauna was greatest at sites with moderate canopy cover outside of sandy soil regions. Working pine landscapes in the western Gulf Coastal Plain can support diverse herpetofaunal assemblages, including open-pine-associated species, when management practices maintain open-canopy conditions on sandy, upland soils. More broadly, our results provide insight into how forest management practices affect herpetofauna and may guide practices that can contribute to conservation value of working pine forests. 相似文献
8.
Bobette R. Dickerson Mary F. Willson Paul Bentzen Thomas P. Quinn 《Animal behaviour》2004,68(2):381-385
Driven by competition and mate choice, size-assortative mating has been seen in many organisms. The breeding system of salmonid fish, Oncorhynchus spp., has been extensively investigated and many examples of size-assortative mating have been found. However, assortative mating is not always observed and many reported examples involved cases with a large dichotomy in size classes or were conducted in artificial arenas where other factors influencing mate choice and competition were controlled. This study investigated size-assortative mating in a population of naturally reproducing pink salmon, O. gorbuscha. We made direct observations of courtship behaviour over 3 years on fish of known sizes. To determine the extent to which these observations corresponded to reproductive success, we assessed the parentage of the offspring produced by the fish in the first 2 years of the study using DNA fingerprinting. Size-assortative mating was not seen in the behavioural observations. Parentage results showed that our measure of dominance (proximity of males to ripe females) corresponded with successful matings, suggesting that the fish that we observed as dominant were in fact involved in more matings or more successful matings. We also saw no size-assortative mating in male and female pairs that produced adult offspring. We are not suggesting that the processes that can lead to size-assortative mating are not occurring, but that many other factors, such as female ripeness, male availability, predation threat and changing environmental conditions, may minimize the importance or mask the occurrence of size-assortative mating under natural conditions. 相似文献
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JF Yuan SJ Zhang O Jafer RA Furlong OE Chausiaux CA Sargent GH Zhang NA Affara 《BMC microbiology》2009,9(1):246