Wnt signalling and cancer stem cells

[Abstract] Intracellular signalling mediated by secreted Wnt proteins is essential for the establishment of cell fates and proper tissue patterning during embryo development and for the regulation of tissue homeostasis and stem cell function in adult tissues. Aberrant activation of Wnt signalling pathways has been directly linked to the genesis of different tumours. Here, the components and molecular mechanisms implicated in the transduction of Wnt signal, along with important results supporting a central role for this signalling pathway in stem cell function regulation and carcinogenesis will be briefly reviewed.Ministerio de Ciencia e Innovación; SAF2008-0060

Interspecific Competition for Shelters in Territorial and Gregarious Intertidal Grazers: Consequences for Individual Behaviour

<div><p>Experiments have shown that interspecific interactions within consumer guilds can alter patterns of distribution, abundance and size of species. Plastic behavioural responses can be modulated by agonistic interactions. In many cases, consumers compete for space and shelters, and these interactions change the manner in which they exploit food. This study investigates the consequences of competition in the spatial and temporal organization of behaviour of intertidal grazers, which share algal resources and the use of rock crevices while resting, but exhibit different body sizes, spatial behaviour and foraging modes. We evaluate interaction strength between small gregarious <em>Siphonaria lessoni</em> and the larger territorial keyhole limpet <em>Fissurella crassa</em> and between <em>S. lessoni</em> and the medium-size gregarious chiton <em>Chiton granosus</em>. Using field manipulations and artificial arenas in the laboratory, we tested whether the use of crevices, micro-spatial distribution and activity are modified by the density of conspecifics and the presence of heterospecifics. Our results show that small-scale spatial segregation observed in the field between <em>S. lessoni</em> and <em>C. granosus</em> result from species-specific differences in habitat use. In turn, we found evidence that spatial segregation between <em>F. crassa</em> and <em>S. lessoni</em> results from highly asymmetric interference competition in the use of shelters. The presence of <em>F. crassa</em> reduced the use of crevices and growth rates of <em>S. lessoni.</em> Effects on growth rates are assumed to result from exposure to harsh environmental conditions rather than food limitation. Thus, neither gregarious behaviour nor differences in activity were sufficient to prevent competition with the larger grazer. Our study illustrates the importance of competition for shelters, which results in behavioural changes of the smaller-sized species, and how these plastic responses can translate into differences in growth rates. Use of shelters can thus be modulated by environmental conditions in a species-specific as well as an interactive manner within consumers’ guilds.</p> </div

Roadsides and gardens facilitate the expansion of non-native clonal succulent plants to wetlands in the coastal fringe of the Atacama Desert

Urban habitats such as coastal road verges can host a wide range of non-native plant species, which can increase urban biodiversity but also have the potential to impact natural ecosystems. However, the mechanism through which these novel habitats facilitate alien species establishment/invasion in arid coastal systems is not well known. Here, we assessed the potential of roadsides and gardens to facilitate the spread of non-native clonal succulent species to coastal natural ecosystems. We surveyed urban habitats and rural wetlands located from 18°S to 23°S, in the coastal fringe of the Atacama Desert in northern Chile. Using generalized mixed linear models (GLMMs), we explored the effects of habitat extent and distance to urban sources as the main factors contributing to non-native species propagation. Non-native-to-native species spatial association were also examined. We found the occurrences of Sesuvium portulacastrum were higher in roadsides and gardens located from 18°S to 22°S, followed by Malephora crocea, Carpobrotus edulis and Mesembryanthemum (Aptenia) × vascosilvae. S. portulacastrum, followed by C. edulis and, to a lesser extent, M. × vascosilvae, were recorded in urban and rural crypto-wetlands. Increase in species occurrences with built habitat perimeter and a linear reduction by distance to urban sources were detected. Positive association of S. portulacastrum and M. crocea with the native Heliotropium curassavicum was recorded. These results highlight the importance of the coastal landscape composition (diversity and extent of habitat types) and configuration (distance from built to natural habitats) in the process of non-native plant species’ expansion. Given many coastal ecosystems are already damaged by different human-derived impacts, planting non-native succulents in urban habitats should be carefully managed to balance the services/disservices they provide/provoke to urban and natural habitats

Facilitative Effect of a Generalist Herbivore on the Recovery of a Perennial Alga: Consequences for Persistence at the Edge of Their Geographic Range.

Understanding the impacts of consumers on the abundance, growth rate, recovery and persistence of their resources across their distributional range can shed light on the role of trophic interactions in determining species range shifts. Here, we examined if consumptive effects of the intertidal grazer Scurria viridula positively influences the abundance and recovery from disturbances of the alga Mazzaella laminarioides at the edge of its geographic distributions in northern-central Chilean rocky shores. Through field experiments conducted at a site in the region where M. laminarioides overlaps with the polar range edge of S. viridula, we estimated the effects of grazing on different life stages of M. laminarioides. We also used long-term abundance surveys conducted across ~700 km of the shore to evaluate co-occurrence patterns of the study species across their range overlap. We found that S. viridula had positive net effects on M. laminarioides by increasing its cover and re-growth from perennial basal crusts. Probability of occurrence of M. laminarioides increased significantly with increasing density of S. viridula across the range overlap. The negative effect of S. viridula on the percentage cover of opportunistic green algae-shown to compete for space with corticated algae-suggests that competitive release may be part of the mechanism driving the positive effect of the limpet on the abundance and recovery from disturbance of M. laminarioides. We suggest that grazer populations contribute to enhance the abundance of M. laminarioides, facilitating its recolonization and persistence at its distributional range edge. Our study highlights that indirect facilitation can determine the recovery and persistence of a resource at the limit of its distribution, and may well contribute to the ecological mechanisms governing species distributions and range shifts

Data from: Heterogeneity of ecological patterns, processes and funding of marine manipulative field experiments conducted in Southeastern Pacific coastal ecosystems

Ecological manipulative experiments conducted in marine coastal ecosystems have substantially improved ecological theory during the last decades, and have provided useful knowledge for the management and conservation of coastal ecosystems. Although different studies report global trends in ecological patterns worldwide, Southeastern Pacific coastal ecosystems have been poorly considered. Given that the SE Pacific coast encompasses diverse coastal ecosystems, consideration of studies conducted along this range can shed light on the heterogeneity of processes regulating coastal communities. We reviewed the biotic interactions and habitat type considered, as well as the complexity in terms of spatial and temporal extent of manipulative field experimental studies conducted along the SE Pacific coast from 0°S to 56° S (Ecuador to Chile). We test the effect of funding reported by different studies as a main factor limiting experimental complexity. From field ecological studies published from 1970 to 2016, we found that 81 studies were truly manipulative, in which one or multiple factors were “manipulated”. Around 77% of these studies were located between 21°S to 40°S, and conducted in intertidal rocky habitats. An increase in experimental studies was observed between 2010 and 2015, especially focused on herbivore-alga interactions, although we found that both the temporal and spatial extent of these studies have shown a decrease in recent decades. Funding grant amount reported had a positive effect on elapsed time of field experiments, but no effect was observed on spatial extent or in the biotic interactions considered. Elapsed time of experiments was different among the main biotic interactions considered i.e. herbivory, predation, and competition. We suggest that to further progress in applied ecological knowledge, it will be necessary to consider pollution and urbanization processes explicitly using a field experimental framework. This information could improve our understanding of how ecosystems present along the SE Pacific coast respond to climate change and increased levels of human interventions

Nested ANOVA on average growth rate of individuals present in each arena under the different treatments in field experiments.

<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0046205#pone-0046205-t002" target="_blank">Table 2</a> for clarification of abbreviations.</p><p>Since planned contrasts are not orthogonal, p-values were adjusted using the Dunn-Sidák correction. Significant values at α<0.05 are presented in bold face.</p

Appendix A. Experimental designs.

Experimental designs

Percentage of individuals (%) observed to perform different behavioural responses to interspecific “encounters” in outdoor aquaria at ECIM.

<p>Arrows indicate the heterospecific with which target species encounters.</p><p><b>S</b> = <i>Siphonaria lessoni</i>; <b>F</b> =  <i>Fissurella crassa</i>; <b>C</b> = <i>Chiton granosus</i>.</p