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147 results for “breadth”

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dryad36/100

Elevational and local climate variability predicts thermal breadth of mountain tropical tadpoles

The climate variability hypothesis posits that increased environmental thermal variation should promote species with broader thermal tolerance breadths, while stable environments should promote thermal specialists. This hypothesis has been tested on large spatial scales, such as latitude and elevation, but less so on smaller scales which reflect the experienced microclimate. Here, we estimated thermal tolerance limits of 75 species of amphibian tadpoles from an aseasonal tropical mountain range of the Ecuadorian Andes, distributed along a 3500 m elevational range, to test the climatic variability hypothesis at a large (elevation) and a small (microhabitat) scales. We show how species from less variable thermal habitats, such as lowlands and those restricted to streams, exhibit narrower thermal tolerance breadths than highland and pond-dwelling species respectively. Interestingly, while broader thermal tolerance breadths at large scales are driven by higher cold tolerance variation (heat-invariant hypothesis), at local scales they are driven by higher heat tolerance variation. This contrasting pattern may result from divergent selection on both thermal limits to face environmental thermal extremes at different scales. Specifically, within the same elevational window, exposure to extreme maximum temperatures could be avoided through habitat shifts from temporary ponds to permanent ponds or streams, while minimum peak temperatures remained invariable between habitats but steadily decreased with elevation. Therefore addressing the effects of habitat conversion is crucial for future research on resilience to climate change.

opencc-zeroMar 2022View details →

dryad36/100

DNA metabarcoding confirms primary targets and breadth of diet for coral reef butterflyfishes

Understanding species-specific resource requirements is paramount in managing and protecting biodiversity in a world where environmental quality is in decline. Dietary data can inform predator–prey relationships and how changes in prey availability impact different species. However, for many coral reef fishes, prey and predatory events can be difficult to observe and identify, both in situ and within examined stomach samples. Here we applied DNA metabarcoding of stomach content samples for eleven Red Sea butterflyfish species to identify the diversity of dietary components that these primarily benthic feeding fish consume across coral reefs. Detections based on 18S and COI sequences from partially digested stomach contents significantly increased the resolution and diversity of the known diet for this group of fish, which included cryptic prey that are difficult to visually document due to soft parts or morphological ambiguity. In addition to scleractinian corals and other Cnidaria, the obligate corallivore species fed on a wide range of benthic organisms, whereas facultative species displayed a broader diet with crustaceans, tunicates, and worms contributing to samples. While a number of individuals contained DNA that could not be confidently identified using this method, the proportion of unidentifiable sequences was relatively low across butterflyfish species. The COI marker identified the importance of soft corals in the diet for two hard coral specialists; Chaetodon melannotus and Chaetodon semilarvatus, with soft coral detected in over half of the individuals and contributing significantly to the number of DNA sequence reads within their gut. Notably, five prey items identified to the species level were detected that are currently not documented in the Red Sea. Our analysis revealed that the diet of different species of butterflyfish significantly overlaps, with all species deriving most of their diet from the phylum Cnidaria (hard and soft coral, anemones) and symbiotic Symbiodiniaceae algae. Furthermore, accumulation curves suggest that all study species may feed on an even greater fraction of the benthos, likely driven by the availability and diversity of each individual/pair's associated territory. This approach increases the known dietary resolution and diversity of these key reef fishes and further enhances our understanding between butterflyfish and benthic organisms.

opencc-zeroSep 2022View details →

dryad36/100

How to cope with drought and not die trying: drought acclimation across tree species with contrasting niche breadth

Worldwide drought events have been reported to cause tree growth decline and mortality, thus altering the carbon (C) balance of forest ecosystems. While most of the attention has been focused on the physiological mechanisms associated with drought-induced tree responses of a few species at specific locations, the ecological attributes of these species, like their niche breadth, may be also important in determining species' sensitivity or resilience to drought. We postulated that wide-niche breadth tree species should be more drought-resilient than narrow-niche breadth species. 2. Using the most severe 2015-2016 El Niño drought event in the last 70 years in Patagonia, we determined pre- and post-drought growth (BAI, basal area increment), C reserves in the form of non-structural carbohydrates (NSCs = starch and soluble sugars), wood isotope (δ13C, iWUE and δ18O) signaling, and xylem anatomy (mean vessel diameter, mvd) in eight angiosperm tree species of contrasting niche breadth across a sharp precipitation gradient in southern Chile. 3. All species responded in unison after the drought with a non-water-conservative response, maintaining BAI and NSCs concentrations, decreasing δ13C, and increasing both mvd and the soluble sugars:NSCs ratio relative to pre-drought time. Contrary to previous results reporting species-specific drought responses, our results show unequivocally a functional coordination of organisms' vital traits associated with a non-water-conservative strategy, and a drought-induced acclimation based on starch conversion into soluble sugars in all of the tree species we examined, regardless of their niche breadth and habitat preference. 4. We state that abiotic drivers such as drought may have selected similar interspecific responses provided that they operate at the community level rather than at the species level. These findings mark the need to revise current views about the ultimate interspecific functional coordination of organisms' vital traits when facing more frequent and intensive drought events.

opencc-zeroJul 2021View details →

dryad36/100

Invader abundance and contraction of niche breadth during replacement of a native gammarid amphipod

The introduction of non-native species to new locations is a growing global phenomenon with major negative effects on native species and biodiversity. Such introductions potentially bring competitors into contact leading to partial or total species replacements. This creates an opportunity to study novel species interactions as they occur, with the potential to address the strength of inter- and intraspecific interactions, most notably competition. Such potential has often not been realized, however, due to the difficulties inherent in detecting rapid and spatially expansive species interactions under natural field conditions. The invasive amphipod crustacean Gammarus pulex has replaced a native species, Gammarus duebeni celticus, in river and lake systems across Europe. This replacement process is at least partially driven by differential parasitism, cannibalism and intraguild predation, but the role of interspecific competition has yet to be resolved. Here, we examine how abundance of an invasive species may affect spatial niche breadth of a native congeneric species. We base our analyses of niche breadth on ordination and factor analysis of biological community and physical parameters, respectively, constituting a summative, multidimensional approach to niche breadth along environmental gradients. Results derived from biological and environmental niche criteria were consistent, although interspecific effects were stronger using the biological niche approach. We show that the niche breadth of the native species is constrained as abundance of the invader increases, but the converse effect does not occur. We conclude that the interaction between invasive G. pulex and native G. d. celticus under natural conditions is consistent with strong interspecific competition whereby a native, weaker competitor is replaced by a superior invasive competitor. This study indicates a strong role of interspecific competition, alongside other known interactions such as differential intraguild predation, in rapid and expansive species replacements following biological invasions.

opencc-zeroDec 2022View details →

dryad36/100

The impact of dietary breadth on bumblebee colony fitness

The current decline of pollinators may disrupt ecosystems and ecosystem services with potentially harmful effects on nature and human society. While the importance of habitat loss and fragmentation, pollution and increased disease risk in driving pollinator decline has been clearly demonstrated, the impact of resource diversity is less well understood. In this study, we investigated the effect of pollen diversity and composition on reproductive success and fitness of Bombus terrestris colonies. We asked the question whether a higher plant diversity results in a more diverse diet, lower pathogen incidence and a higher colony fitness. To answer these questions, colonies of lab-reared bumblebees were placed in species-poor heathland and species-rich semi-natural grasslands that strongly differed in plant community composition and diversity. We examined pollen loads on the bodies of foragers and identified the plant taxa present in the realized diet via DNA metabarcoding of the ITS2 marker. Liquid chromatography-mass spectrometry (LC-MS) was used to compare peptide composition of pollen samples from both habitats. Colony fitness was assessed by counting the number of sexuals produced by the colony at the end of its cycle. At the same time, colonies were examined for parasite incidence. Pollen composition and diversity on pollinators' bodies differed significantly between bees foraging in grasslands and heathlands. Concomitantly, peptide composition differed significantly between pollen samples from grasslands and heathlands. Colonies developed significantly better in heathland sites than in grasslands. In addition, colony fitness was only weakly related to pollen diversity and effects in some cases depended on the habitat where the bees were foraging. Pathogen incidence was very low and not affected by habitat. Overall, our results indicate that plant diversity is not necessarily a good predictor of colony fitness, and that vegetation composition and associated differences in both the quantity and quality of pollen are more important than pollen diversity per se.

opencc-zeroFeb 2023View details →

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Data for: Recent range shifts of moths, butterflies, and birds are driven by the breadth of their climatic niche

Species are altering their ranges as a response to climate change, but the magnitude and direction of observed range shifts vary considerably among species. The ability to persist in current areas and colonize new areas plays a crucial role in determining which species will thrive and which decline as climate change progresses. Several studies have sought to identify characteristics, such as morphological and life-history traits, that could explain differences in the capability of species to shift their ranges together with a changing climate. These characteristics have explained variation in range shifts only sporadically, thus offering an uncertain tool for discerning responses among species. As long-term selection to past climates have shaped species' tolerances, metrics describing species' contemporary climatic niches may provide an alternative means for understanding responses to on-going climate change. Species that occur in a broader range of climatic conditions may hold greater tolerance to climatic variability and could therefore more readily maintain their historical ranges, while species with more narrow tolerances may only persist if they are able to shift in space to track their climatic niche. Here, we provide a first-filter test of the effect of climatic niche dimensions on shifts in the leading range edges in three relatively well-dispersing species groups. Based on the realized changes in the northern range edges of 383 moth, butterfly, and bird species across a boreal 1100 km latitudinal gradient over c. 20 years, we show that while most morphological or life-history traits were not strongly connected with range shifts, moths and birds occupying a narrower thermal niche and butterflies occupying a broader moisture niche across their European distribution show stronger shifts towards the north. Our results indicate that the climatic niche may be important for predicting responses under climate change and as such warrants further investigation of potential mechanistic underpinnings.

opencc-zeroFeb 2023View details →

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Data from: The role of niche breadth in oak phylogeography: Quercus glaucoides as a study case

The amount of genetic diversity and its distribution among populations has been associated to species' attributes such as mating system, dispersal ability and geographic range size. Another attribute that could contribute to explain intraspecific phylogeographic patterns is niche breadth, but this relationship barely has been tested. Here, we studied a Mexican oak (Quercus glaucoides) with a comparatively narrow climatic niche breadth. Genetic diversity and structure were assessed, as well as historical demography dynamics and connectivity. Then, we tested for a general correlation of genetic diversity and structure with niche breadth, using our data and previous results from other co-distributed Mexican oaks with variable niche breadths. Methods Descriptors of genetic diversity and structure were obtained from 21 Q. glaucoides populations using chloroplast DNA (cpDNA) and nuclear microsatellites (nSSRs). Historical demography dynamics were inferred with approximate Bayesian computation (ABC) and past potential distribution models. To test for an association between niche breadth and phylogeographic patterns, we used genetic diversity and differentiation values of Q. glaucoides plus those previously published for other ten species. Niche breadth was estimated for all species and linear regressions were performed. Results Genetic diversity calculated from nSSRs (HO= 0.539; HE= 0.714) was among the lowest, and cpDNA differentiation (NST= 0.88) was the highest so far obtained for comparable Mexican oaks. Moderate changes in demographic size and distribution shifts throughout the last glacial cycle were inferred, explaining some of the observed genetic patterns. A positive correlation of HO and a negative correlation of NST with niche breadth were detected across species. Main conclusions Distinct phylogeographic patterns in Q. glaucoides could be explained because a narrower niche may cause lower historical effective population sizes and more fragmented distributions in comparison to species with a wider niche breadth, even with similar range sizes.

opencc-zeroMar 2023View details →

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Dispersal ability and niche breadth influence interspecific variation in spider abundance and occupancy

The relationship between species local abundance and their regional distribution (occupancy) is one of the most extensively recognised and investigated patterns in ecology. While exceptions exist, the generally held model is that locally abundant species also tend to be more widespread geographically. However, there is only a limited understanding of both the mechanisms driving this relationship, and their scale dependency. Here we use occupancy and abundance data for 123 species of spider from across the Canary Islands to understand how both dispersal ability and niche breadth might mediate variation among species for local abundance and occupancy. We test the predictions that (i) dispersal ability explains variation among species for both abundance and occupancy, and (ii) species with a higher degree of habitat specialisation, reflecting more limited niche breadth, will have both higher occupancy and abundance. We find no evidence within habitat patches for an effect of dispersal ability on either local abundance or site occupancy, while across all patches species with higher dispersal ability tend to occupy more sites. Species largely restricted to laurel forests have higher abundance than species with broader niche breadth, but similar occupancy. The study revealed that dispersal ability and niche breadth were significant predictors of the abundance-occupancy relationship, highlighting the importance of both factors for understating patterns of abundance and occupancy among spider species.

opencc-zeroApr 2023View details →

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Niche breadth explains the range size of European-centred butterflies, but dispersal ability does not

Aim: The breadth of ecological niches and dispersal abilities have long been discussed as important determinants of species' range sizes. However, studies directly comparing the relative effects of both factors are rare, taxonomically biased and revealed inconsistent results. Location: Europe. Time period: Cenozoic. Major taxa: Butterflies, Lepidoptera. Methods: We relate climate, diet, and habitat niche breadth and two indicators of dispersal ability, wingspan and a dispersal tendency index, to the global range size of 369 European-centred butterfly species. The relative effects of these five predictors and their variation across the butterfly phylogeny were assessed by means of phylogenetic generalized least squares models and phylogenetically weighted regressions, respectively. Results: Climate niche breadth was the most important single predictor, followed by habitat and diet niche breadth, while dispersal tendency and wingspan showed no relation to species' range size. All predictors together explained 59% of the variation in butterfly range size. However, the effects of each predictor varied considerably across families and genera. Main conclusions: Range sizes of European-centred butterflies are strongly correlated with ecological niche breadth but apparently independent of dispersal ability. The magnitude of range size – niche breadth relationships is not stationary across the phylogeny and is often negatively correlated across the different dimensions of the ecological niche. This variation limits the generalizability of range size–trait relationships across broad taxonomic groups.

opencc-zeroMay 2023View details →

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