eDNA refers to DNA extracted from an environmental sample with the goal of identifying the occurrence of past or current biological communities in aquatic and terrestrial environments. However, there ...is currently a lack of knowledge regarding the soil memory effect and its potential impact on lake sediment eDNA records. To investigate this issue, two contrasted sites located in cultivated environments in France were studied. In the first site, soil samples were collected (n = 30) in plots for which the crop rotation history was documented since 1975. In the second site, samples were collected (n = 40) to compare the abundance of currently observed taxa versus detected taxa in cropland and other land uses. The results showed that the last cultivated crop was detected in 100% of the samples as the most abundant. In addition, weeds were the most abundant taxa identified in both sites. Overall, these results illustrate the potential of eDNA analyses for identifying the recent (< 10 years) land cover history of soils and outline the detection of different taxa in cultivated plots. The capacity of detection of plant species grown on soils delivering sediments to lacustrine systems is promising to improve our understanding of sediment transfer processes over short timescales.
Abstract
Proteins encoded by antigen-processing genes (APGs) provide major histocompatibility complex (MHC) class I (MHC-I) with antigenic peptides. In mammals, polymorphic multigenic MHC-I family is ...served by monomorphic APGs, whereas in certain nonmammalian species both MHC-I and APGs are polymorphic and coevolve within stable haplotypes. Coevolution was suggested as an ancestral gnathostome feature, presumably enabling only a single highly expressed classical MHC-I gene. In this view coevolution, while optimizing some aspects of adaptive immunity, would also limit its flexibility by preventing the expansion of classical MHC-I into a multigene family. However, some nonmammalian taxa, such as salamanders, have multiple highly expressed MHC-I genes, suggesting either that coevolution is relaxed or that it does not prevent the establishment of multigene MHC-I. To distinguish between these two alternatives, we use salamanders (30 species from 16 genera representing six families) to test, within a comparative framework, a major prediction of the coevolution hypothesis: the positive correlation between MHC-I and APG diversity. We found that MHC-I diversity explained both within-individual and species-wide diversity of two APGs, TAP1 and TAP2, supporting their coevolution with MHC-I, whereas no consistent effect was detected for the other three APGs (PSMB8, PSMB9, and TAPBP). Our results imply that although coevolution occurs in salamanders, it does not preclude the expansion of the MHC-I gene family. Contrary to the previous suggestions, nonmammalian vertebrates thus may be able to accommodate diverse selection pressures with flexibility granted by rapid expansion or contraction of the MHC-I family, while retaining the benefits of coevolution between MHC-I and TAPs.
AIM: Speciation can either proceed as gradual divergence, mostly in allopatry or parapatry, or by duplication of chromosome sets: polyploidization. Hybrid‐origin or allopolyploidization is an ...important mechanism of hybrid speciation with strong, although often incomplete, postzygotic reproductive barriers between the polyploid hybrid and its diploid parents. Allopolyploids often present novel phenotypes that exceed the ranges of their ancestral lineages, leading to the hypothesis that niche shifts could be supportive of hybrid speciation. Although polyploidy is phylogenetically widespread in animals, ecological niches of diploid ancestral and derived allopolyploids have been rarely comparatively examined. Here, we do so for five species of Palaearctic green toads (Bufo viridis subgroup), involving three ploidy levels. LOCATION: Central Asia, High Asia. METHODS: We gathered distributional records of genotyped toads, covering the whole range of the five toad species. We then used similarity and equivalency tests and examined whether bioclimatic (Grinellian) niches of allopolyploids are intermediate to those of the extant diploid relatives of their ancestral forms or whether they are transgressive (beyond those of both ancestors). RESULTS: We found evidence for both transgressive and conservative niches in allopolyploids. Allotetraploids (Bufo pewzowi, B. oblongus) showed transgressive niche evolution; they inhabited environments that were harsher (more arid and with colder winters) than both of their parental species. In contrast, the allotriploid B. baturae exhibited a conserved niche, similar to an ancestral lineage that provided two‐thirds of its hybrid genome. For most comparisons, niches of extant diploid ancestral lineages were significantly different from each other. MAIN CONCLUSION: We conclude that allopolyploidization in amphibians leads potentially but not a necessarily to transgressive niche evolution, and may facilitate hybrid speciation by allowing newly formed hybrids to colonize novel habitats and thus escape their parental lineages.
The Himalaya presents an outstanding geologically active orogen and biodiversity hotspot. However, our understanding of the historical biogeography of its fauna is far from comprehensive. Many taxa ...are commonly assumed to have originated from China-Indochina and dispersed westward along the Himalayan chain. Alternatively, the "Tibetan-origin hypothesis" suggests primary diversification of lineages in Paleo-Tibet, and secondary diversification along the slopes of the later uplifted Greater Himalaya. We test these hypotheses in high-mountain megophryid anurans (Scutiger). Extensive sampling from High Asia, and analyses of mitochondrial (2839 bp) and nuclear DNA (2208 bp), using Bayesian and Maximum likelihood phylogenetics, suggest that the Himalayan species form a distinct clade, possibly older than those from the eastern Himalaya-Tibet orogen. While immigration from China-Indochina cannot be excluded, our data may indicate that Himalayan Scutiger originated to the north of the Himalaya by colonization from Paleo-Tibet and then date back to the Oligocene. High intraspecific diversity of Scutiger implies limited migration across mountains and drainages along the Himalaya. While our study strengthens support for a "Tibetan-origin hypothesis", current sampling (10/22 species; 1 revalidated: S. occidentalis) remains insufficient to draw final conclusions on Scutiger but urges comparative phylogeographers to test alternative, geologically supported hypotheses for a true future understanding of Himalayan biogeography.
Eco-cultural landscapes are assumed to be favorable environments for the persistence of biodiversity, but global change may affect differently their terrestrial and aquatic components. Few long-term ...studies have examined how multiple, global change stressors may affect wetland biodiversity in such environments. Facultative paedomorphosis is a spectacular example of intra-specific variation, in which biphasic (metamorphosing) amphibians coexist with fully aquatic conspecifics that do not metamorphose (paedomorphs). Paedomorphosis is seriously threatened by global change stressors, but it is unknown to what extent traditional management will allow its long-term persistence. Here, we tested the effects of alien species introductions while taking into account land use and climate changes on the distribution of two polymorphic newt species (Ichthyosaura alpestris and Lissotriton graecus) in Montenegro by using a 68-yr data set and Bayesian mixed models integrating complex spatial and temporal structures. We found that, despite the persistence of natural landscapes, metamorphs dramatically declined and paedomorphs were nearly extirpated, losing 99.9% of their aquatic area of occupancy and all the major populations. Fish introduction was the main determinant of decline for both phenotypes. Climate and the presence of crayfish further contributed to the decline of metamorphs, which started later and was less dramatic than that of paedomorphs. The near extinction of paedomorphosis on a country-wide scale shows how invasive species determine broad-scale impacts, which can be even stronger than other global change stressors, and underlines the need for immediate management actions to avoid the extinction of a unique developmental process, paedomorphosis.
Landscape-level thresholds and newt conservation Denoël, Mathieu; Ficetola, G. Francesco
Ecological applications,
2007, 20070101, January 2007, 2007-Jan, 2007-01-00, Letnik:
17, Številka:
1
Journal Article, Web Resource
Recenzirano
Odprti dostop
Ecological thresholds are defined as points or zones at which a rapid change occurs from one ecological condition to another. The existence of thresholds in species-habitat relationships has ...important implications for management, but the lack of concordance across studies and the wide range of methods used make generalizations difficult. We used two different statistical methods to test for the existence of thresholds for both individual species and the whole community, using three newt species as models. Based on a sample of 371 ponds, we found significant thresholds for both landscape configuration and composition. These were for the relationships between distance to forest and occurrence of Triturus alpestris and T. helveticus, and forest and crop cover and T. helveticus. Variability in the location of thresholds observed for the different species in this study caution against their use at the community level. Future studies should be based on the identification and assessment of thresholds for targeted species. Thresholds can be a useful concept from which tools may be developed to focus conservation effort for threatened species and their habitats.
Pesticides and other chemicals often have detrimental effects at environmental concentrations. Many amphibian species are particularly threatened because of their susceptibility but also because ...wetlands are often polluted. Behavioral assessments of toxicity have the advantage of showing sublethal effects but quantitative measures at varied scales of integrations are rarely considered together. In this study, we aimed at showing that these behavioral endpoints could be differently affected across time and concentrations, and be biomarkers of toxicity. To this end, we tested the effects of an organochlorine pesticide (endosulfan) on amphibians during a standard 96 h test. We evaluated possible lag effects in continuing the analyses after removal of the pesticide. The study was based on 240 tadpoles (4 pesticide treatments: 0.4, 3, 22, and 282 μg/l, 1 control and 1 solvent-control). Abnormal behaviors such as lying and swirling rapidly were exhibited only in the presence of the pesticide. Essential functions such as breathing and feeding were deeply affected by the pesticide: contaminated tadpoles breathed and fed less than control tadpoles. They also moved less and occupied a more central position in the aquariums in the presence of the pesticide. A higher mortality was only found at the highest concentration. These results suggest that endosulfan is toxic to amphibians at environmental concentrations. Behavioral markers showed potential as early warning systems. They should thus be used in complement to other markers to detect sublethal effects only a few days after application of the pesticide and at concentrations where mortality does not occur.
Populations of large mammals have declined at alarming rates, especially in areas with intensified land use where species can only persist in small habitat fragments. To support conservation ...planning, we developed habitat suitability models for the Walia ibex (
Capra walie
), an endangered wild goat endemic to the Simen Mountains, Ethiopia. We calibrated several models that differ in statistical properties to estimate the spatial extent of suitable habitats of the Walia ibex in the Simen Mountains, as well as in other parts of the Ethiopian highlands to assess potentially suitable areas outside the current distribution range of the species. We further addressed the potential consequences of future climate change using a climate model with four emission scenarios. Model projections estimated the potential suitable habitat under current climate to 501–672 km
2
in Simen and 6,251–7,732 km
2
in other Ethiopian mountains. Under projected climate change by 2,080, the suitable habitat became larger in Simen but smaller in other parts of Ethiopia. The projected expansion in Simen is contrary to the general expectation of shrinking suitable habitats for high-elevation species under climate warming and may partly be due to the ruggedness of these particular mountains. The Walia ibex has a wide altitudinal range and is able to exploit very steep slopes, allowing it to track the expected vegetation shift to higher altitudes. However, this potential positive impact may not last long under continued climate warming, as the species will not have much more new space left to colonize. Our study indicates that the current distribution range can be substantially increased by reintroducing and/or translocating the species to other areas with suitable habitat. Indeed, to increase the viability and prospects for survival of this flagship species, we strongly recommend human-assisted reintroduction to other Ethiopian mountains. Emulating the successful reintroduction of the Alpine ibex that has spread from a single mountain in Italy to its historical ranges of the Alps in Europe might contribute to saving the Walia ibex from extinction.
PDF
