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opencc-zeroSep 2020View details →

Data from: Species richness and redundancy promote persistence of exploited mutualisms in yeast

Mutualisms, or reciprocally beneficial interspecific interactions, constitute the foundation of many ecological communities and agricultural systems. Mutualisms come in different forms, from pairwise interactions to extremely diverse communities, and they are continually challenged with exploitation by non-mutualistic community members (exploiters). Thus, understanding how mutualisms persist remains an essential question in ecology. Theory suggests that high species richness and functional redundancy could promote mutualism persistence in complex mutualistic communities. Using a yeast system (Saccharomyces cerevisiae), we experimentally show that communities with the greatest mutualist richness and functional redundancy are nearly two times more likely to survive exploitation than are simple communities. Persistence increased because diverse communities were better able to mitigate the negative effects of competition with exploiters. Thus, large mutualistic networks may be inherently buffered from exploitation.

opencc-zeroDec 2017View details →

Data from: Unequal contributions of species' persistence and migration on plant communities' response to climate warming throughout forests

Community reshuffling is lagging behind climate warming for many taxa, thereby generating a climatic debt. However, only few studies have attempted to assess the underlying factors that explain this debt. Here I examine how effects of species' migration and persistence on the current climatic debt vary spatially in forest herbaceous communities throughout the French territory. I show that Mediterranean communities are responding to climate warming through both high species' migration and persistence effects, while alpine forest is the only ecosystem where species' migration overtakes species' persistence mechanisms. Such an approach seems promising in assessing the underlying mechanisms of the biodiversity response to climate change locally, and it can be applied for conservation issues to assess biodiversity sensitivity and optimize its management.

opencc-zeroDec 2015View details →

Data from: Long-term persisting hybrid swarm and geographic difference in hybridization pattern: genetic consequences of secondary contact between two Vincetoxicum species (Apocynaceae–Asclepiadoideae)

Background: During glacial periods, glacial advances caused temperate plant extirpation or retreat into localized warmer areas, and subsequent postglacial glacial retreats resulted in range expansions, which facilitated secondary contact of previously allopatric isolated lineages. The evolutionary outcomes of secondary contact, including hybrid zones, dynamic hybrid swarm, and resultant hybrid speciation, depends on the strengths of reproductive barriers that have arisen through epistatic and pleiotropic effects during allopatric isolation. The aim of this study was to demonstrate refugia isolation and subsequent secondary contact between two perennial Asclepioid species and to assess the genetic consequences of the secondary contact. We modeled the range shift of two ecologically distinct Vincetoxicum species using the species distribution model (SDM) and assessed the genetic consequences of secondary contact by combining morphological and genetic approaches. We performed morphometric analysis (592 individuals) and examined 10 nuclear microsatellites (671 individuals) in V. atratum, V. japonicum, and putative hybrid populations. Results: Multivariate analysis, model-based Bayesian analysis, and non-model-based discriminant analysis of principal components confirmed the hybridization between V. atratum and V. japonicum. High pollen fertility and a lack of linkage disequilibrium suggested that the hybrid populations may be self-sustaining and have persisted since V. atratum and V. japonicum came into contact during the post-glacial period. Moreover, our findings show that the pattern of hybridization between V. atratum and V. japonicum is unidirectional and differs among populations. Geographically-isolated hybrid populations exist as genetically distinct hybrid swarms that consist of V. atratum-like genotypes, V. japonicum-like genotypes, or admixed genotypes. In addition, Bayesian-based clustering analysis and coalescent-based estimates of long-term gene flow showed patterns of introgressive hybridization in three morphologically 'pure' V. japonicum populations. Conclusion: In this study, we demonstrated that climatic oscillations during the Quaternary period likely led to species range shift and subsequently secondary contact. Hybrid populations may be self-sustaining and have persisted since V. atratum and V. japonicum came into contact during the post-glacial period. Pattern of hybridization between V. atratum and V. japonicum is unidirectional and differs among populations. We concluded that these differences in the genetic consequences of secondary contact are caused by historical colonization processes and/or natural selection.

opencc-zeroDec 2015View details →

Data from: Tropical rainforests that persisted: inferences from the Quaternary demographic history of eight tree species in the Guiana shield

How Quaternary climatic and geological disturbances influenced the composition of Neotropical forests is hotly debated. Rainfall and temperature changes during and/or immediately after the last glacial maximum (LGM) are thought to have strongly affected the geographical distribution and local abundance of tree species. The paucity of the fossil records in Neotropical forests prevents a direct reconstruction of such processes. To describe community-level historical trends in forest composition, we turned therefore to inferential methods based on the reconstruction of past demographic changes. In particular, we modelled the history of rainforests in the eastern Guiana Shield over a timescale of several thousand generations, through the application of approximate Bayesian computation and maximum-likelihood methods to diversity data at nuclear and chloroplast loci in eight species or subspecies of rainforest trees. Depending on the species and on the method applied, we detected population contraction, expansion or stability, with a general trend in favour of stability or expansion, with changes presumably having occurred during or after the LGM. These findings suggest that Guiana Shield rainforests have globally persisted, while expanding, through the Quaternary, but that different species have experienced different demographic events, with a trend towards the increase in frequency of light-demanding, disturbance-associated species.

opencc-zeroDec 2017View details →

Data from: Persistence at the final stage of volcanic island ontogeny: abiotic predictors explain native plant species richness on 111 remote Pacific atolls

Aim: The final island ontogeny of the General Dynamic Model (GDM) (i.e. before island submergence) in tropical oceans corresponds to the coral atoll stage. Here, we examined whether the species richness of native vascular plants (indigenous and endemic species) on atolls is controlled by spatial and/or physical processes. We also predicted that atolls strongly affected by anthropogenic disturbance would have lower native species richness than predicted by spatial and physical processes. Location: Marshall Islands, Kiribati Islands, Nauru, Niue, Johnston, Cook Islands, French Polynesia and Pitcairn Islands (Pacific Ocean). Taxon: Native vascular plants Methods: We used stepwise regression to test the relative influence of five biogeographic variables on native species richness. Relationships were assessed for the full set of 111 Pacific coral atolls, as well as for atoll subsets ranging from 9 to 45 atolls. An index of human impact was then estimated, and residuals in the regression model predicting species richness from biogeographic variables were compared with the level of human impact. Results: A regression model including atoll area, highest atoll elevation, the stepping stone distances from the nearest raised atoll and volcanic island explained native species richness on the 111 Pacific coral atolls. Regression models for different archipelagos and atoll subsets were also significant. Endemic species richness was significantly linked with highest atoll elevation and the stepping stone distances from the nearest raised atoll. Residuals in the biogeographic regression model were barely related to human impact across the 111 atolls but were significantly related to human impact in the Kiribati atolls. Main conclusions: Native species richness on atolls is mainly controlled by physical and spatial characteristics. However, anthropogenic disturbances have altered the predicted pattern of native species richness leading to a lower model fit in some atoll subsets.

opencc-zeroDec 2018View details →

Data from: Persistently rare species experience stronger negative frequency dependence than common species: a statistical attractor that is hard to avoid

Aim: Why are so many species rare, yet persistent? Possibly, rare species experience strong negative frequency dependence (NFD, i.e. strong intraspecific competition relative to interspecific competition), which both makes them rare and buffers them against extinction. A second, not mutually exclusive, possibility is that rare species that experience weak NFD go extinct quickly due to demographic and environmental stochasticity. Both possibilities predict that persistent rare species will experience stronger NFD than common ones. Yenni et al. (2017) confirmed this prediction in a range of mostly-terrestrial communities. Here we test that prediction in lake zooplankton, and explore its theoretical basis. Location: 53 temperate lakes Time period: 1970-2011 Major taxa studied: Cladocerans, copepods Methods: We used long-term time series data to estimate the covariance between strength of NFD and mean frequency (relative abundance) for crustacean zooplankton. We used a randomization test to ask whether the covariance between NFD and mean frequency is stronger than expected, given sampling error. We also calculated the covariance between NFD and mean frequency in simulated communities from three different ecological models. Results: Rare species experience significantly stronger NFD than common species in over half of the communities. The distribution of associations between NFD and rarity is skewed towards weak associations, which always occur in communities with high evenness. All three theoretical models reproduce these empirical results, even though they are based on different mechanisms (demographic or environmental stochasticity, and mathematical constraints on possible NFD-frequency relationships). Main conclusions: Rare species typically experience stronger NFD than common ones because there are many different ecological scenarios in which they will do so, and only a few scenarios in which they won't. Like several other macroecological patterns, the tendency for rare species to experience stronger NFD than common ones is a "statistical attractor" that is hard to avoid.

opencc-zeroJul 2019View details →

Data from: The potential importance of unburned islands as refugia for the persistence of wildlife species in fire-prone ecosystems

The persistence of wildlife species in fire-prone ecosystems is under increasing pressure from global change, including alterations in fire regimes caused by climate change. However, unburned islands might act to mitigate negative effects of fire on wildlife populations by providing habitat in which species can survive and recolonize burned areas. Nevertheless, the characteristics of unburned islands and their role as potential refugia for the post-fire population dynamics of wildlife species remain poorly understood. We used a newly developed unburned island database of the north-western United States from 1984–2014 to assess the post-fire response of the greater sage-grouse (Centrocercus urophasianus), a large gallinaceous bird inhabiting the sagebrush ecosystems of North America, in which wildfires are common. Specifically, we tested whether pre- and post-fire male attendance trends at mating locations (leks) differed between burned and unburned areas, and to what extent post-fire habitat composition at multiple scales could explain such trends. Using time-series of male counts at leks together with spatially-explicit fire history information, we modelled whether male attendance was negatively affected by fire events. Results revealed that burned leks often exhibit sustained decline in male attendance, whereas leks within unburned islands or >1.5 km away from fire perimeters tend to show stable or increasing trends. Analyses of post-fire habitat composition further revealed that sagebrush vegetation height within 0.8 km around leks, as well elevation within 0.8km, 6.4km, and 18 km around leks, had a positive effect on male attendance trends. Moreover, the proportion of the landscape with cheatgrass (Bromus tectorum) cover >8% had negative effects on male attendance trends within 0.8 km, 6.4 km, and 18 km of leks, respectively. Our results indicate that maintaining areas of unburned vegetation within and outside fire perimeters may be crucial for sustaining sage-grouse populations following wildfire, and requires more attention in wildlife management.

FIGURE 16 in Two new species of Colubotelson Nicholls, 1944 in Tasmania's Lake Pedder: persistence of Phreatoicidae (Crustacea, Isopoda) in therein

FIGURE 16. Colubotelson pedderensis sp. nov. Paratype male (QVM:10:51202), pleopods, light micrographs in ventral view: A, I; B–D, II with SEM enlargements of appendix masculina and distal tip; E, III with enlargement of setae on exopod distal article; F–G, IV–V. Scale bar 1.0 mm.

FIGURE 15 in Two new species of Colubotelson Nicholls, 1944 in Tasmania's Lake Pedder: persistence of Phreatoicidae (Crustacea, Isopoda) in therein

FIGURE 15. Colubotelson pedderensis sp. nov. Paratype male (QVM:10:51202), mouthparts. A–D, maxillula: ventral view, enlargement of lateral and medial lobe, lateral lobe, medial view. E–F, maxilla: medial and ventral views. G–I, maxilliped: ventral view, medial view of endite, enlargement of endite distal tip setae. Scale bars 0.5 mm.

FIGURE 14 in Two new species of Colubotelson Nicholls, 1944 in Tasmania's Lake Pedder: persistence of Phreatoicidae (Crustacea, Isopoda) in therein

FIGURE 14. Colubotelson pedderensis sp. nov. Paratype male (QVM:10:51202), anterior mouthparts. A, labrum, anterior view, small globular objects are epizoic peritrichs. Scale bar 1 mm. B–D, left mandible medial view, palp distal articles with enlargement of setae (scale bar 0.05 mm), and ventral view of distal gnathal margin. E–F, right mandible, dorsal view and medial view of incisor and spine row. A, B, E scale bars 0.5 mm.

FIGURE 13 in Two new species of Colubotelson Nicholls, 1944 in Tasmania's Lake Pedder: persistence of Phreatoicidae (Crustacea, Isopoda) in therein

FIGURE 13. Colubotelson pedderensis sp. nov. Paratype male (QVM:10:51202). A–B, pereopod V, lateral view, with enlargement of dactylus and propodus, medial view. C, pereopod VII, segments distal to merus lost, lateral view. D, penes, posterior view. E, antennula, in situ, with enlargement of distal tip. F, antenna, in situ, with enlargement of distal tip. Scale bars: A, C, F 1.0 mm; D, E 0.5 mm.

FIGURE 12 in Two new species of Colubotelson Nicholls, 1944 in Tasmania's Lake Pedder: persistence of Phreatoicidae (Crustacea, Isopoda) in therein

FIGURE 12. Colubotelson pedderensis sp. nov. Paratype male (QVM:10:51202), pereopods. A–D, pereopod I, lateral view, with enlargements of dactylus and palm, and setation of palm, lateral and medial views. E–F, pereopod II, lateral view, with enlargement of dactylus, propodus and carpus. G–H, pereopod IV, lateral view, with enlargement of dactylus, propodus and carpus. Small globular objects are epizoic peritrichs. Scale bars 1.0 mm.

FIGURE 18 in Two new species of Colubotelson Nicholls, 1944 in Tasmania's Lake Pedder: persistence of Phreatoicidae (Crustacea, Isopoda) in therein

FIGURE 18. Colubotelson pedderensis sp. nov. Paratype female (QVM:10:51203). A–B, pereopod I, with enlargement of palm. C, pereopod II, lateral view. D, pereopod VII, lateral view. E–H, pleotelson: lateral view, uropod, dorsal view, posterior margin. Scale bars 1 mm.

FIGURE 10 in Two new species of Colubotelson Nicholls, 1944 in Tasmania's Lake Pedder: persistence of Phreatoicidae (Crustacea, Isopoda) in therein

FIGURE 10. Colubotelson pedderensis sp. nov. Lateral views, with enlargements of anterior and posterior parts of the body. A–C, holotype male (QVM:10:51201). E–F, paratype male (QVM:10:51204). Scale bars 5.0 mm.

FIGURE 11 in Two new species of Colubotelson Nicholls, 1944 in Tasmania's Lake Pedder: persistence of Phreatoicidae (Crustacea, Isopoda) in therein

FIGURE 11. Colubotelson pedderensis sp. nov. Paratype male (QVM:10:51202), pleotelson and uropods. A, right lateral view. B, posterior margin and apex, lateral view. C, dorsal view. D, posterior apex and posterolateral lobes, dorsal view. E, ventral margin anterior to uropods, distally denticulate robust setae. F, medial view of ventral margin, showing group of medial group of small distally denticulate robust setae. G, posterior margin of pleotelson, ventral view. H, distal group of robust setae on ventral margin of uropodal protopod. I, left uropod, lateral view. Small globular objects are epizoic peritrichs. Scale bar 1.0 mm.

FIGURE 17 in Two new species of Colubotelson Nicholls, 1944 in Tasmania's Lake Pedder: persistence of Phreatoicidae (Crustacea, Isopoda) in therein

FIGURE 17. Colubotelson pedderensis sp. nov. Paratype female (QVM:10:51203), head. A, lateral view. B, dorsal view. C–D, antennula with enlargement of distal tip. E–F, mandibular palp with enlargement of denticulate seta on palp article 3. G, ventral view. Scale bar 1 mm.

FIGURE 9 in Two new species of Colubotelson Nicholls, 1944 in Tasmania's Lake Pedder: persistence of Phreatoicidae (Crustacea, Isopoda) in therein

FIGURE 9. Colubotelson edgarensis sp. nov. Paratype female, (QVM:10:51199), pereopods (A–D) and pleotelson (E–I). A, C, pereopod II, lateral view. B, D, pereopod IV, lateral view. E, right lateral view. F, uropod, lateral view. G, ventral margin anterior to uropods, medial view, showing posterior group of 3 distally denticulate setae. H–I, posterior margin and apex, lateral and dorsal views. Scale bars 1.0 mm.

FIGURE 5 in Two new species of Colubotelson Nicholls, 1944 in Tasmania's Lake Pedder: persistence of Phreatoicidae (Crustacea, Isopoda) in therein

FIGURE 5. Colubotelson edgarensis sp. nov. Paratype male (QVM:10:51198), mouthparts. A–D, left mandible. A, dorsal view. B, lacinia and spine row. C, medial view. E, right mandible, gnathal margin, dorsal view. F, paragnaths, ventral view. G–I, maxillula, ventral view, enlargement of gnathal margin, and medial view of lateral lobe. Scale bars 0.2 mm.

FIGURE 4 in Two new species of Colubotelson Nicholls, 1944 in Tasmania's Lake Pedder: persistence of Phreatoicidae (Crustacea, Isopoda) in therein

FIGURE 4. Colubotelson edgarensis sp. nov. Paratype male (QVM:10:51198), pereopods. A, C, D, pereopod I, lateral view, with enlargements of dactylus and palm, and setation of palm. B, pereopod II, lateral view. E–F, pereopod IV, lateral view, with enlargement of dactylus, propodus and carpus. G, pereopod V, lateral view. H, pereopod VII, medial view. I, penes, posterior view. Scale bars 1.0 mm.

FIGURE 2 in Two new species of Colubotelson Nicholls, 1944 in Tasmania's Lake Pedder: persistence of Phreatoicidae (Crustacea, Isopoda) in therein

FIGURE 2. Colubotelson edgarensis sp. nov. A–C, holotype male (QVM:10:51197), left lateral view, with enlargements of head and pleotelson. D, paratype male (QVM:10:51200), right lateral view, SEM. Scale bar 1.0 mm.