Evidence Of Niche Conservatism Research Articles

Evidence for niche conservatism in alpine beetles under a climate‐driven species pump model

AbstractAimPast glacial cycles have generated lineage diversity in alpine habitats, acting as a climate‐driven species pump. It is not clear how much this process contributes to ecological diversification of alpine species. To examine this problem, we test patterns of genetic and phenotypic divergence in two co‐distributed species complexes of flightless alpine ground beetles. Greater differentiation in functional traits would indicate that ecological selection is an outcome of oscillating climate change, whereas greater differentiation in non‐ecological traits would indicate niche conservatism.LocationThe Cascades Range and Trinity Mountains of western North America.TaxonNebria paradisiandN.vandykeispecies complexes (Insecta: Coleoptera: Carabidae: Nebriinae).MethodsWe generated genome‐wide single nucleotide polymorphism data and mitochondrial sequence data, as well as morphological and physiological data, to compare populations spanning the range of both species. Phylogenetic and population genetic analyses were used to infer relationships among taxa and populations in each species complex, as well as historical demography. Support vector machines were used to test for classification of taxa and populations based on ecomorphological, ecophysiological and male reproductive traits. Mantel tests were then used to assess associations between phenotypic and genetic divergence among populations.ResultsTheN.vandykeiandN.paradisispecies complexes are each comprised of genetically distinctive populations exhibiting long‐term demographic declines. Each phylogeny supports multiple monophyletic groups with geographical cohesion. By examining phenotypic traits among populations in both species’ complexes, we show that reproductive trait divergence can discriminate species and population status more effectively than ecomorphological or ecophysiological traits. Reproductive and genetic divergence are significantly correlated in theN.vandykeispecies complex.Main ConclusionsWe found limited evidence of ecological selection acting on functional traits. Instead, reproductive and genetic divergence evolved among isolated populations in both species complexes, suggesting niche conservatism may be a common outcome in alpine species diversification.

Evidence of Constrained Divergence and Conservatism in Climatic Niches of the Temperate Maples (Acer L.)

Research highlights: The availability of global distribution data and new, fossil-calibrated phylogenies has made it possible to compare the climatic niches of the temperate maple (Acer L.) taxa and assess phylogenetic and continental patterns in niche overlap. Background and Objectives: The maples have radiated from East Asia into two other temperate continental bioregions, North America and Eurasia (Europe and West Asia), over a roughly 60-million-year period. During this time, the Earth’s climate experienced pronounced cooling and drying, culminating in cyclic periods of widespread temperate glaciation in the Pliocene to Pleistocene. The objective of this study is to use newly available data to model the climatic niches of 60% of the temperate maples and assess patterns of niche divergence, constraint, and conservatism in the genus’s radiation out of East Asia. Materials and Methods: I assembled global occurrence data and associated climatic information for 71 maple taxa, including all species endemic to temperate North America and Eurasia and their closely related East Asian congeners. I constructed Maxent niche models for all taxa and compared the climatic niches of 184 taxa pairs and assessed phylogenetic signal in key niche axes for each taxon and in niche overlap at the continental and global scale. Results: Maxent models define a fundamental climatic niche for temperate maples and suggest that drought-intolerant taxa have been lost from the Eurasian maple flora, with little continental difference in temperature optima or breadth. Niche axes and niche overlap show minimal evidence of phylogenetic signal, suggesting adaptive evolution. Pairwise niche comparisons reveal infrequent niche overlap continentally and globally, even among sister pairs, with few taxa pairs sharing ecological niche space, providing evidence for constrained divergence within the genus’s fundamental climatic niche. Evidence of niche conservatism is limited to three somewhat geographically isolated regions of high maple diversity (western North America, the Caucasus, and Japan). Conclusions: Over 60 million years of hemispheric radiation on a cooling and drying planet, the maple genus experienced divergent, though constrained, climatic niche evolution. High climatic niche diversity across spatial and phylogenetic scales along with very limited niche overlap or conservatism suggests that the radiation of the genus has largely been one of adaptive diversification.

Intraspecific differentiation: Implications for niche and distribution modelling

AbstractAimMounting evidence suggests that failure of species distribution models to integrate local adaptation hinders our ability to predict distribution ranges, raising the question of whether modelling should be performed at the level of species (clade models) or intraspecific lineages (subclade models), characterized by the restricted availability of occurrence points. While Ensembles of Small Models (ESMs) offer an attractive framework for small datasets, their evaluation remains critical. We address these issues in the case of very small datasets inherent to subclade models and discuss which modelling strategy should be applied based on niche overlap among lineages.LocationSweden.TaxonMosses.MethodsEnsembles of Small Models were evaluated by null models built from randomly sampled presence points. We compared the extent of suitable area predicted by the projections of clade and subclade models. Niche overlap was quantified using Schoener's D and Hellinger'sImetrics, and the significance of these metrics in terms of niche conservatism or divergence was assessed by similarity tests.ResultsWe introduced a simple procedure for evaluating ESMs based on the pooling of the statistics used to assess model accuracy from the replicates. Despite fairly high AUC and TSS values, 2 of the 23 subclade models did not perform better than null models and should be discarded. Combined predictions from subclade models contributed, on average, five times more than clade models to the total suitable area predicted by the combination of subclade and clade models. The D and I metrics averaged 0.45 and 0.71, with evidence for niche conservatism in half of the species and no signal for niche divergence.Main conclusionsIn addition to the assessment of ESM accuracy based on the simple procedure described here, we recommend that ESMs should be systematically evaluated against null models. Lumping or splitting occurrence data at the intraspecific level substantially impacted model projections. Given the poor performance of models based on small datasets, even when employing ESMs, we pragmatically suggest that, in the absence of evidence for niche divergence during diversification of closely related intraspecific lineages, SDMs should be based on all available occurrence data at the species level.

A comparative analysis reveals little evidence for niche conservatism in aquatic macrophytes among four areas on two continents

One of the most intriguing questions in current ecology is the extent to which the ecological niches of species are conserved in space and time. Niche conservatism has mostly been studied using coarse‐scale data of species' distributions, although it is at the local habitat scales where species' responses to ecological variables primarily take place. We investigated the extent to which niches of aquatic macrophytes are conserved among four study regions (i.e. Finland, Sweden and the US states of Minnesota and Wisconsin) on two continents (i.e. Europe and North America) using data for 11 species common to all the four study areas. We studied how ecological variables (i.e. local, climate and spatial variables) explain variation in the distributions of these common species in the four areas using species distribution modelling. In addition, we examined whether species' niche parameters vary among the study regions. Our results revealed large variation in both species' responses to the studied ecological variables and in species' niche parameters among the areas. We found little evidence for niche conservatism in aquatic macrophytes, though local environmental conditions among the studied areas were largely similar. This suggests that niche shifts, rather than different environmental conditions, were responsible for variable responses of aquatic macrophytes to local ecological variables. Local habitat niches of aquatic macrophytes are mainly driven by variations in local environmental conditions, whereas their climate niches are more or less conserved among regions. This highlights the need to study niche conservatism using local‐scale data to better understand whether species' niches are conserved, because different niches (e.g. local versus climate) operating at various scales may show different degrees of conservatism. The extent to which species' niches are truly conserved has wide practical implications, including for instance, predicting changes in species' distributions in response to global change.

Analysing patterns of spatial and niche overlap among species at multiple resolutions

AbstractAimAnalyses of spatial overlap in species distributions are frequently used to test a range of ecological and evolutionary hypotheses, from the role of competition in community assembly to the geography of speciation. Most studies quantify overlap at one spatial resolution. Here we explore the effects of measuring spatial and niche overlap patterns for the same clade (Banksia) at multiple resolutions.LocationAustralia.MethodsWe quantify overlap among species using broad overlap of species range polygons, proximity of occurrence points and co‐occurrence within small survey plots. We compare overlap patterns with null models using age–range correlations and the frequency of sympatric sister species. We then use similar methods to examine patterns of overlap in environmental niche dimensions.ResultsBanksia species show a wide range of overlap values based on range polygons and point proximities, but very low levels of co‐occurrence at the local scale. Intercepts of age–range correlations point to higher levels of overlap among recently diverged species than expected. However, comparing the frequency of sympatric sister species with an evolutionary null model supports a prevailing allopatric mode of speciation. In many cases, niche overlap between species exceeds that expected from phylogenetic relatedness or spatial overlap alone.Main conclusionsPatterns of broad geographical overlap among Banksia species support a predominantly allopatric mode of speciation, combined with post‐speciation range drift. There is more evidence for niche conservatism than for rapid niche divergence among closely related species. This pattern is consistent with broad‐scale geomorphic and landscape complexity as a driver of plant speciation in south‐west Australia. It is less consistent with finer‐scale mechanisms of species divergence such as fire mosaics, or with ecological divergence in sympatry. Analysis of species overlap patterns at different resolutions is a useful approach for revealing the multiple ecological and historical factors that influence species distributions.

Evidence of niche conservatism and host fidelity in the polar shrimp Lebbeus kiae n. sp. (Decapoda: Caridea: Thoridae) from the Ross Sea, Antarctica

We report a remarkable case of ‘bipolarism’, where two different polar species, namely Lebbeus polaris in the northern hemisphere and Lebbeus kiae n. sp., here described from the Southern Ocean, have been found to share similar ecologies. Despite the great geographical distance between the two species, both show high host fidelity in associations with two congeneric sea anemones: Bolocera tuediae and Bolocera kerguelensis, respectively. A close molecular phylogenetic relationship between the two Lebbeus species is indicated by COI data, which clearly show them as sister clades with respect to other congeners as well as a plurality of other Antarctic species. This is the first reported case of a defensive association in the Southern Ocean involving shrimps and sea anemones. The distribution of the new species, limited to seamount systems off the Ross Sea, may be the result of a specific colonisation/speciation event in the past, although more molecular data are needed to unravel the phylogenetic relationships within the genus Lebbeus. Despite this uncertainty, the persistence of ecological traits, i.e., the defensive association with sea anemones, indicates the presence of niche conservatism in this clade of shrimps.

Volatile compound diversity and conserved alarm behaviour in Triatoma dimidiata.

BackgroundTriatoma dimidiata (Latreille) is a key vector complex of Trypanosoma cruzi, etiologic agent of Chagas disease, as it spans North, Central, and South America. Although morphological and genetic studies clearly indicate existence of at least five clades within the species, there has been no robust or systematic revision, or appropriate nomenclature change for species within the complex. Three of the clades (haplogroups) are distributed in Mexico, and recent evidence attests to dispersal of clades across previously “presumed” monotypic geographic regions. Evidence of niche conservatism among sister species of this complex suggests that geographic dispersal is possible for non-sympatric populations, although no information is available on the behavioural aspects of potential interclade interactions, for instance whether differentiation of chemical signaling or response to these signals could impede communication among the haplogroups.MethodsVolatiles emitted by disturbed bugs, Brindley’s (BGs), and metasternal (MGs) glands were identified using solid-phase micro-extraction (SPME) and gas chromatography coupled mass spectrometry (GC-MS). Volatile compounds emitted by BGs and MGs, and those secreted by disturbed nymphs and adults, of the three Mexican T. dimidiata haplogroups were tested for avoidance behaviour by conspecific nymphs and adults using an olfactometer.ResultsTriatoma dimidiata haplogroups all have three age-related alarm responses: absence of response by early stage nymphs, stage-specific response by 4-5th stage nymphs, and a shared 4-5th nymph and adult response to adult compounds. Disturbed bugs released 15 to 24 compounds depending on the haplogroup, among which were three pyrazines, the first report of these organoleptics in Triatominae. Isobutyric acid from BGs was the most abundant molecule in the response in all haplogroups, in addition to 15 (h1) to 21 (h2 and h3) MG compounds. Avoidance behaviour of disturbed bugs and volatiles emitted by BGs were haplogroup specific, while those from the MG were not.ConclusionsDiscriminant and cluster analysis of BG + MG compounds indicate significant separation among the three haplogroups, while alarm response compounds were similar between h2 and h3, both distinct from h1. This latter haplogroup is ancestral phylogenetically to the other two. Our results suggest that alarm responses are a conserved behaviour in the Triatoma dimidiata complex.

Fig-Frugivore Interactions Follow a Constrained Brownian Motion Model of Evolution in an Important Bird Area, West Africa

Understanding how ecosystems function is critical in order to shed light on processes that lead to species coexistence. Ficus species provide highly specialized niches for frugivores in tropical forests, but little is known about how Ficus-hugivore interactions evolve over time. Here we applied three approaches to investigate these interactions based on key parameters. We tested for a model of evolution that could explain interaction patterns, evaluated the phylogenetic signal, and assessed the evolutionary rate of niches generated by Ficus species. We showed that interactions are best explained by a Brownian motion model, indicating a random walk. However, the signal observed is lower than expected under this model, and at the same time the evolutionary rate provides evidence for niche conservatism. Such findings are incompatible with an unbounded Brownian process. We therefore propose that a random walk constrained by ecological forces towards a stabilizing selection could better explain fig-frugivore i...

Environmental Niche Modeling Reveals Climatic Differences among Breeding Ranges of Orchard Oriole Subspecies

Environmental niche parameters of breeding ranges for two subspecies in the Orchard Oriole complex (Icterus spurius spurius and I. s. fuertesi) were characterized via ecological niche modeling. Niche models formulated from museum specimen collections largely agree with published breeding ranges of both taxa. Furthermore, our findings identify likely suitable habitat of migratory double breeding in I. s. spurius. Models successfully identify suitable habitat as illustrated by threshold dependent and independent statistical tests and overlap very little in geographic space. Principal component analysis (PCA) identifies two axes explaining 99.0% of variation in the climate data and reveals that each breeding range exhibits unique ecological characteristics, as they occur in nonoverlapping PCA space. Multivariate analysis of variance (MANOVA) identifies significant differences along both axes (PC1, P , 0.0001; PC2, P , 0.0001). A newly formulated metric for niche similarity (I) agrees with PCA and ENM results and, further, indicates that environmental niche differences are more likely a result of differences in habitat availability than habitat preference. Our results may indicate rapid change in environmental niche within the Orchard Oriole group as these taxa have been diverging for approximately 200,000 y. The Orchard Oriole group provides an example of niche lability that contrasts with evidence of niche conservatism between many other Mexican species pairs.

Ecological niche conservatism in North American freshwater fishes

There are many hypotheses of relationships, and also of speciation processes, in North American freshwater fishes, although, to date, there have been no direct tests of whether there is evidence of ecological niche conservatism. In the present study, ecological niche modeling is used to look for evidence of ecological niche conservatism in six clades of freshwater fishes: the starheaded topminnows, sand darters, black basses, Notropis rubellus species group, Notropis longirostris species group, and the Hybopsis amblops species group. This is achieved by evaluating the reciprocal predictivity of distributional predictions based on ecological niche models developed for each individual taxon in a clade under the assumption that high reciprical predictivity between sister species can be taken as evidence of niche conservatism. Omission percentages, total and average commission, and the area under the curve in a receiver operating characteristic analysis, where calculated, are used to evaluate predictive ability. Occurrence data for each species were subset into a training and independent validation data set where possible. Across all clades and species, models predicted the validation data for a given species well. Ecological niche conservatism was found generally across the starheaded topminnows, the sand darters, and the N. longirostris species group. There was some inter-predictivity within the N. rubellus group, but almost no inter-predictivity within the black basses, indicating a lack of conservatism. These results demonstrate that ecological niches generally act as stable constraints on freshwater fish distributions in North America.

Community Assembly, Niche Conservatism, and Adaptive Evolution in Changing Environments

The widespread correspondence between phenotypic variation and environmental conditions, the “fit” of organisms to their environment, reflects the adaptive value of plant functional traits. Several processes contribute to these patterns: plasticity, ecological sorting, and adaptive evolution. This article addresses the importance of ecological sorting processes (community assembly, migration, habitat tracking, etc.) as primary causes of functional trait distributions at the local and landscape level. In relatively saturated communities, plants will establish and regenerate in environments to which they are well adapted, so their distributions, and the distributions of associated functional traits, will reflect the distribution of optimal or near‐optimal environmental conditions in space and time. The predicted evolutionary corollary of this process is that traits related to habitat occupancy, e.g., environmental tolerances, will be under stabilizing selection. This process contributes to the widely observed pattern of phylogenetic niche conservatism, i.e., ecological and phenotypic similarities of closely related species. Evidence for niche conservatism in plants is reviewed. Based on Jackson and Overpeck’s concept of the realized environment, I propose three scenarios in which a species’ distributional responses to environmental conditions will lead to a “mismatch” between its environmental tolerances and the environments it occupies, thus creating opportunities for adaptive evolution: (1) the colonization of “environmental islands” (habitats that are discontinuous in niche space) that require large adaptive shifts in tolerance of one or more environmental factors; (2) the persistence of “trailing‐edge” populations in species tracking changing climate, if barriers to dispersal of competitors prevent competitive exclusion in the deteriorating conditions; and (3) responses to changes in the realized environment in multidimensional niche space, in which species are predicted to track environmental factors for which they exhibit narrow tolerances and exhibit adaptive evolutionary response along axes where they exhibit greater niche breadth. These three scenarios provide a conceptual framework that emphasizes the role of ecological sorting processes and stabilizing selection as the context for understanding opportunities for adaptive evolution in heterogeneous and changing environments.