scholarly journals Wild snapdragon plant pedigree sheds light on limited connectivity enhanced by higher migrant reproductive success in a fragmented landscape

2021 ◽  
Vol 1 ◽  
pp. 145
Author(s):  
Laura Gervais ◽  
Pierick Mouginot ◽  
Anais Gibert ◽  
Oceane Salles ◽  
Mathieu Latutrie ◽  
...  

Background: In contrast with historical knowledge, a recent view posits that a non-negligible proportion of populations might respond positively to habitat fragmentation. Populations might thrive in a fragmented landscape if functional connectivity, i.e., the net flow of individuals or their genes moving among suitable habitat patches, is not restricted. Alternatively, functional connectivity might be typically limited but enhanced by a higher reproductive success of migrants. Methods: We tested for this hypothesis in wild snapdragon plants inhabiting six patches separated by seawater in a fragmented Mediterranean scrubland landscape. We reconstructed their pedigree by using a parentage assignment method based on microsatellite genetic markers. We then estimated functional connectivity and the reproductive success of plants resulting from between-patch dispersal events. Results: We found that wild snapdragon plants thrived in this fragmented landscape, although functional connectivity between habitat patches was weak (i.e. 2.9%). The progeny resulting from between-patch dispersal events had a higher reproductive success than residents. Conclusion: Our findings expose a remarkable aspect of fragmented landscapes, where weak functional connectivity was enhanced by higher reproductive success after migration. This process might have the potential to compensate at least partly the negative impact of fragmentation.

2016 ◽  
Vol 22 (2) ◽  
pp. 120-137 ◽  
Author(s):  
Jasmeet P. Hayes ◽  
Erin D. Bigler ◽  
Mieke Verfaellie

AbstractObjectives:Recent advances in neuroimaging methodologies sensitive to axonal injury have made it possible to assess in vivo the extent of traumatic brain injury (TBI) -related disruption in neural structures and their connections. The objective of this paper is to review studies examining connectivity in TBI with an emphasis on structural and functional MRI methods that have proven to be valuable in uncovering neural abnormalities associated with this condition.Methods:We review studies that have examined white matter integrity in TBI of varying etiology and levels of severity, and consider how findings at different times post-injury may inform underlying mechanisms of post-injury progression and recovery. Moreover, in light of recent advances in neuroimaging methods to study the functional connectivity among brain regions that form integrated networks, we review TBI studies that use resting-state functional connectivity MRI methodology to examine neural networks disrupted by putative axonal injury.Results:The findings suggest that TBI is associated with altered structural and functional connectivity, characterized by decreased integrity of white matter pathways and imbalance and inefficiency of functional networks. These structural and functional alterations are often associated with neurocognitive dysfunction and poor functional outcomes.Conclusions:TBI has a negative impact on distributed brain networks that lead to behavioral disturbance. (JINS, 2016,22, 120–137)


1995 ◽  
Vol 73 (S1) ◽  
pp. 1334-1342 ◽  
Author(s):  
David Malloch

Heteroxenous (multiple host) life histories are characteristic of many groups of parasitic protista and animals, including Zoomastigina, Apicomplexa, Mesozoa, Platyhelminthes, Nematoda, Acanthocephala, Pentastomida, and Arthropoda. Parasitic fungi, including the Chytridiomycota and the Dikaryomycota (ascomycetes and basidiomycetes), may also have heteroxenous life histories and have many features in common with parasites from other groups. In spite of many conceptual similarities, the study of parasitic fungi has occurred in isolation, resulting in the creation of a separate vocabulary and literature. Many of the concepts developed by zoologists are useful to mycologists and allow examination of parasitic fungi from new perspectives. These new perspectives reveal that heteroxenous fungi are not only similar to heteroxenous protistans and animals but that they also have unique characteristics of their own. Chief among these is a high level of endocyclic asexual reproduction, a phenomenon promoting exponential increases of infections in definitive host populations. Heteroxeny appears to have a number of benefits including (i) increased lifetime reproductive success, (ii) increased transmission efficiency (iii) enhanced effectiveness in colonizing ephemeral or periodically appearing hosts and hosts occurring in low population densities, (iv) maintenance or enhancement of overdispersed frequency distributions in host populations, and (v) enhancement of genetic exchange through multiple dispersal events. Key words: fungi, heteroxenous, parasite, life histories.


1999 ◽  
Vol 89 (6) ◽  
pp. 523-531 ◽  
Author(s):  
K.A. Joyce ◽  
J.M. Holland ◽  
C.P. Doncaster

AbstractIn the fragmented landscape of arable farmland, hedgerows and other non-crop habitats provide refuges of food and shelter for invertebrates, and corridors through which they can move to other habitats. Their role as corridors is likely to depend on their connectivity, both to each other and to other patches of suitable habitat. The effects of connectivity on the carabid beetle Nebria brevicollis (Fabricius) were analysed by observing movement between hedgerow intersections (nodes) and the linear section of the hedgerow, and across gaps in the hedgerow. Capture–mark–recapture of N. brevicollis revealed a uniformly higher activity at hedgerow nodes than at mid-section strips of comparable area. This is consistent with previous studies of hedgerow fauna including butterflies, plants and birds. Gaps in the hedgerows typically measured 7–9 m and functioned as a passage between fields for farm machinery. These were readily crossed by N. brevicollis as was the hedge bottom. Some movement along the hedgerow was found indicating their use as a corridor.


2021 ◽  
Vol 288 (1961) ◽  
Author(s):  
Carl Tamario ◽  
Erik Degerman ◽  
Daniela Polic ◽  
Petter Tibblin ◽  
Anders Forsman

Ecological theory postulates that the size and isolation of habitat patches impact the colonization/extinction dynamics that determine community species richness and population persistence. Given the key role of lotic habitats for life-history completion in rheophilic fish, evaluating how the distribution of swift-flowing habitats affects the abundance and dynamics of subpopulations is essential. Using extensive electrofishing data, we show that merging island biogeography with meta-population theory, where lotic habitats are considered as islands in a lentic matrix, can explain spatio-temporal variation in occurrence and density of brown trout ( Salmo trutta ). Subpopulations in larger and less isolated lotic habitat patches had higher average densities and smaller between-year density fluctuations. Larger lotic habitat patches also had a lower predicted risk of excessive zero-catches, indicative of lower extinction risk. Trout density further increased with distance from the edge of adjacent lentic habitats with predator ( Esox lucius ) presence, suggesting that edge- and matrix-related mortality contributes to the observed patterns. These results can inform the prioritization of sites for habitat restoration, dam removal and reintroduction by highlighting the role of suitable habitat size and connectivity in population abundance and stability for riverine fish populations.


eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Lauren N Booth ◽  
Travis J Maures ◽  
Robin W Yeo ◽  
Cindy Tantilert ◽  
Anne Brunet

Sexual interactions have a potent influence on health in several species, including mammals. Previous work in C. elegans identified strategies used by males to accelerate the demise of the opposite sex (hermaphrodites). But whether hermaphrodites evolved counter-strategies against males remains unknown. Here we discover that young C. elegans hermaphrodites are remarkably resistant to brief sexual encounters with males, whereas older hermaphrodites succumb prematurely. Surprisingly, it is not their youthfulness that protects young hermaphrodites, but the fact that they have self-sperm. The beneficial effect of self-sperm is mediated by a sperm-sensing pathway acting on the soma rather than by fertilization. Activation of this pathway in females triggers protection from the negative impact of males. Interestingly, the role of self-sperm in protecting against the detrimental effects of males evolved independently in hermaphroditic nematodes. Endogenous strategies to delay the negative effect of mating may represent a key evolutionary innovation to maximize reproductive success.


2017 ◽  
Author(s):  
Mara Ines Espinosa Herazo ◽  
Nicolas Gouin ◽  
Francisco Antonio Squeo Porcile ◽  
David López Aspe ◽  
Angéline Bertin

Connectivity between populations plays a key role in the long-term persistence of species in fragmented habitats. It is an issue of concern for the preservation of biodiversity in drylands since landscapes in water limited environments are characterized by low habitat cover, high habitat fragmentation and harsh matrices, and are being rapidly degraded at the global scale. In this study, we modelled landscape connectivity between the 11 remnant coastal and Andean populations of the guanaco Lama guanicoe, an emblematic herbivore indigenous to South America, in Chile's arid Norte Chico. We first produced a habitat surface model to derive a regional surface resistance map; and we then used circuit theory to map functional connectivity, investigate the degree of isolation of the populations, and identify those that most contribute to the network patch connectivity. Predicted suitable habitat for L. guanicoe represented about 25% of the study region (i.e. 29,173 km2), and was heterogeneously distributed along a continuous stretch along the Andes, and discontinuous patches along the coast. As a result, we found that high connectivity current flows in the mid and high Andes formed a wide continuous connectivity corridor enabling connectivity between all the high Andean populations. Coastal populations, in contrast, were predicted to be more isolated. They only connect to medium and high altitude populations, and for two of them, animal movement was linked to the effectiveness of wildlife crossings. Based on the degree of connectivity, population size, and local threats, the coastal and the northernmost populations were identified as being most vulnerable, while the Andean populations appeared to be least at risk, even when located near areas of mining activity. Collectively, our results suggest that functional connectivity is an issue of concern for L. guanicoe in Chile’s Norte Chico, and that future conservation and management plans should adopt a landscape strategy aiming at conserving the functional connectivity between the coastal and Andean populations, and at protecting the habitat patches likely to act as stepping stones within the connectivity network.


2007 ◽  
Vol 362 (1479) ◽  
pp. 461-472 ◽  
Author(s):  
Julian D Olden

Abstract In landscape ecology, substantial theoretical progress has been made in understanding how critical threshold levels of habitat loss may result in sudden changes in landscape connectivity to animal movement. Empirical evidence for such thresholds in real systems, however, remains scarce. Streambed landscapes provide a strong testing ground for studying critical thresholds because organisms are faced with substantial environmental heterogeneity while attempting to overcome the physical force of water. In this study, I report on the results from a series of experiments investigating the influence of habitat abundance and current velocity on the movement dynamics of two stream herbivores (caddisfly larva Agapetus boulderensis and snail Physa sp.) that differ substantially in how they perceive landscape structure. Specifically, I ask whether critical thresholds to herbivore movement exist in streambed landscapes. By exploiting the pattern recognition capabilities of artificial neural networks, I found that the rate, sinuosity and directionality of movement by Agapetus and Physa varied nonlinearly according to the abundance of habitat patches, current velocity and habitat–current interaction. Both the study organisms exhibited threshold responses to habitat abundance, yet the location and slope of these thresholds differed between species and with respect to different current velocities. These results suggest that a critical threshold in functional connectivity (i.e. the connection of habitat patches by dispersal) is not an inherent property of the landscape, but in fact emerges from the interplay of species' interactions with landscape structure. Moreover, current velocity interacted with habitat abundance to elicit strong upstream-oriented movement for both the species. This suggests that dispersing individuals may be polarized in the upstream direction and therefore functional connectivity is not equal in all directions. Such results highlight the need for future research addressing the sources of variability of critical threshold effects in ecological phenomena.


Ecology ◽  
2021 ◽  
Author(s):  
Jani Heino ◽  
Luis Mauricio Bini

In the last two decades, community ecology has matured to consider biotic communities as a product of both local and regional processes. Therefore, local communities are currently thought to be connected by the dispersal of organisms, thereby forming a metacommunity. A metacommunity is organized by multiple processes, including environmental filtering, biotic interactions, dispersal, and ecological drift. Thus, spatial variations in local diversity (i.e., alpha diversity) and community composition (i.e., beta diversity) result from the relative roles of these major processes. In turn, these processes are mediated by organisms’ characteristics, environmental heterogeneity, and the connectivity between localities in a metacommunity. For a given environmental gradient, the role of environmental filtering is likely to be dependent on the dispersal rates shown by organisms. Unsuitable habitat patches (i.e., sinks), in terms of biotic and abiotic characteristics, may be occupied by different species due to high dispersal rates from suitable habitat patches (i.e., sources). Thus, mass effects occur when species are established at localities where their populations cannot be self-maintained. Even though it may be difficult to prove the action of mass effects per se, given the complex interactions between different mechanisms shaping biotic communities, there is some empirical evidence supporting their importance in nature. In addition, high dispersal rates that lead to mass effects may have important implications for biomonitoring and biodiversity conservation. This is because species occurring at sites beyond their niche requirements may provide false information about a site’s ecological quality or result in misleading plans to conserve species at sites where they cannot persist in the absence of continuous influx of propagules.


Ecology ◽  
2010 ◽  
Vol 91 (11) ◽  
pp. 3332-3342 ◽  
Author(s):  
Katrine Turgeon ◽  
Audrey Robillard ◽  
Jacinthe Grégoire ◽  
Vanessa Duclos ◽  
Donald L. Kramer

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