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opencc-zeroDec 2014View details →

Data from: The importance (or lack thereof) of niche divergence to the maintenance of a northern species complex: the case of the long-toed salamander (Ambystoma macrodactylum Baird)

The relative importance of ecological versus non-ecological factors for the origin and maintenance of species is an open question in evolutionary biology. Young lineages—such as the distinct genetic groups that make up the ranges of many northern species—represent an opportunity to study the importance of ecological divergence during the early stages of diversification. Yet, few studies have examined the extent of niche divergence between lineages in previously glaciated regions and the role of ecology in maintaining the contact zones between them. In this study, we used tests of niche overlap in combination with ecological niche models to explore the extent of niche divergence between lineages of the long-toed salamander (Ambystoma macrodactylum Baird) species complex and to determine whether contact zones correspond to (divergent) niche limits. We found limited evidence for niche divergence between the different long-toed salamander lineages, substantial overlap in the predicted distribution of suitable climatic space for all lineages and range limits that are independent of niche limits. These results raise questions as to the importance of ecological divergence to the development of this widespread species complex and highlight the potential for non-ecological factors to play a more important role in the maintenance of northern taxa.

opencc-zeroDec 2017View details →

Data from: The effect of range overlap on ecological niche divergence depends on spatial scale in monkeyflowers

Patterns of niche divergence and geographical range overlap of closely related species provide insights into the evolutionary dynamics of ecological niches. When ranges overlap, shared selective pressures may preserve niche similarity along coarse‐scale macrohabitat axes (e.g., bioclimates). Alternatively, competitive interactions may drive greater divergence along local‐scale microhabitat axes (e.g., micro‐topographical features). We tested these hypotheses in 16 species pairs of western North American monkeyflowers (Erythranthe and Diplacus, formerly Mimulus) with species' niches, geographic ranges and a robust phylogeny. We found that macrohabitat niche divergence decreased with increasing range overlap, consistent with convergent selection operating at a coarse scale. No significant relationship was detected for microhabitat niches. Additionally, niche divergence was greater for young pairs along all macrohabitat niche axes, but greater for old pairs along one microhabitat axis related to vegetation cover. For a subset of species pairs with partially overlapping ranges, greater microhabitat divergence was detected in sympatry than in allopatry for at least one niche axis for three pairs, consistent with character displacement in sympatry. Thus, coarse‐ and local‐scale niche divergence show dissimilar patterns in relation to range overlap and evolutionary time, perhaps because the relative importance of convergent versus divergent selection depends on spatial scale.

opencc-zeroDec 2012View details →

Data from: Niche divergence by deep-sea octocorals in the genus Callogorgia across the continental slope of the Gulf of Mexico

Environmental variables that are correlated with depth have been suggested to be among the major forces underlying speciation in the deep sea. This study incorporated phylogenetics and ecological niche models (ENM) to examine whether congeneric species of Callogorgia (Octocorallia: Primnoidae) occupy different ecological niches across the continental slope of the Gulf of Mexico (GoM), and whether this niche divergence could be important in the evolution of these closely related species. Callogorgia americana americana, C. americana delta, and C. gracilis were documented at 13 sites in the GoM (250-1000 m) from specimen collections and extensive video observations. On a first order, these species were separated by depth, with C. gracilis occurring at the shallowest sites, C. a. americana at mid-depths, and C. a. delta at the deepest sites. Callogorgia a. delta was associated with areas of increased seep activity whereas C. gracilis and C. a. americana were associated with narrow, yet warmer, temperature ranges and did not occur near cold seeps. ENM background and identity tests revealed little to no overlap in ecological niches between species. Temporal calibration of the phylogeny revealed the formation of the Isthmus of Panama was a vicariance event that may explain some of the patterns of speciation within this genus. These results elucidate the potential mechanisms for speciation in the deep sea, emphasizing both bathymetric speciation and vicariance events in the evolution of a genus across multiple regions.

opencc-zeroDec 2014View details →

Data from: Patterns of trophic niche divergence between invasive and native fishes in wild communities are predictable from mesocosm studies

1. Ecological theory attempts to predict how impacts for native species arise from biological invasions. A fundamental question centres on the feeding interactions of invasive and native species: whether invasion will result in increased interspecific competition, which would result in negative consequences for the competing species, or trophic niche divergence, which would facilitate the invader's integration into the community and their coexistence with native species. 2. Here, the feeding interactions of a highly invasive fish, topmouth gudgeon Pseudorasbora parva, with three native and functionally similar fishes were studied to determine whether patterns of either niche overlap or divergence detected in mesocosm experiments were apparent between the species at larger spatial scales. Using stable isotope analysis, their feeding relationships were assessed initially in the mesocosms (1000 L) and then in small ponds (<400 m2) and large ponds (>600 m2). 3. In the mesocosms, a consistent pattern of trophic niche divergence was evident between the sympatric fishes, with niches shifting further apart in isotopic space than suggested in allopatry, revealing that sharing of food resources was limited. Sympatric P. parva also had a smaller niche than their allopatric populations. 4. In eight small ponds where P. parva had coexisted for several years with at least one of the fish species used in the mesocosms, strong patterns of niche differentiation were also apparent, with P. parva always at a lower trophic position than the other fishes, as also occurred in the mesocosms. Where these fishes were sympatric within more complex fish communities in the large ponds, similar patterns were also apparent, with strong evidence of trophic niche differentiation. 5. Aspects of the ecological impacts of P. parva invasion for native communities in larger ponds were consistent with those in the mesocosm experiments. Their invasion resulted in divergence in trophic niches, partly due to their reduced niche widths when in sympatry with other species, facilitating their coexistence in invaded ecosystems. Our study highlights the utility of controlled mesocosm studies for predicting the trophic relationships that can develop from introductions of non-native species into more complex ecosystems and at larger spatial scales.

opencc-zeroDec 2014View details →

Data from: Ecological explanations to island gigantism: dietary niche divergence, predation and size in an endemic lizard

Although rapid evolution of body size on islands has long been known, the ecological mechanisms behind this island phenomenon remain poorly understood. Diet is an important selective pressure for morphological divergence. Here we investigate if selection for novel diets has contributed to the multiple independent cases of island gigantism in the Skyros wall lizard (Podarcis gaigeae) and if diet, predation, or both factors best explain island gigantism. We combined data on body size, shape, bite force, and realized and available diets to address this. Several lines of evidence suggest that diet has contributed to the island gigantism. The larger islet lizards have relatively wider heads and higher bite performance in relation to mainland lizards than would be expected from size differences alone. The proportions of consumed and available hard prey are higher on islets than mainland localities, and lizard body size is significantly correlated with the proportion of hard prey. Furthermore, the main axis of divergence in head shape is significantly correlated with dietary divergence. Finally, a model with only diet and one including diet and predation regime explain body size divergence equally well. Our results suggest that diet is an important ecological factor behind insular body size divergence, but could be consistent with an additional role for predation.

opencc-zeroDec 2010View details →

Data from: Environmental niche divergence between genetically distant lineages of an endangered water beetle

Historically, there has been considerable disagreement between researchers about the criteria used to discriminate among species. Decisions based on traditional morphological and genetic data alone can be potentially problematic, especially if the hypotheses are contradictory. Today, taxonomy is integrating new methods from different disciplines that study species' limits and evolution; this diverse range of evidence aids researchers in the recognition of species. Differences in niche characteristics could become a new and useful criterion in helping to decide the status of conflicting taxonomical entities. Ochthebius glaber (family Hydraenidae) is an endangered water beetle typical from southeast Iberian hypersaline streams that shows three clear discrete genetic units within its distribution range. However, there is no evidence to date that these lineages of O. glaber exhibit any adaptive morphological or ecological divergence. Using a modelling approach directed to generate niche representation from distributional data, we found a significant environmental niche divergence for allopatric lineages of O. glaber that followed an aridity gradient. Although we can not conclude firmly at present that the separate populations of O. glaber studied represent separate, reproductively isolated species, this study complements and supports previous phylogeographic analyses through the inclusion of measures of another form of evolutionary change; in this case, ecological diversification. Despite the existence of some methodological limitations, also discussed in this work, we emphasise the importance of recent conceptual advances that allow taxonomy to improve species delimitation practices through the integration of theory and methods from disciplines that study the origin and evolution of species.

Figure 3 in Diverging structures, perch heights, temperatures, and levels of sunlight of spatial niche dimensions ease the syntopic life of Tropidurus hispidus and Tropidurus semitaeniatus (Squamata: Tropiduridae)

Figure 3. Correlations of distance from the nearest potential shelter (cm) with (a) snout-vent length (mm) and (b) body mass (g) of Tropidurus semitaeniatus. The straight and the curved lines represent, respectively, linear and quadratic models.

Figure 1 in Diverging structures, perch heights, temperatures, and levels of sunlight of spatial niche dimensions ease the syntopic life of Tropidurus hispidus and Tropidurus semitaeniatus (Squamata: Tropiduridae)

Figure 1. Ordination by non-metric multidimensional scaling comparing proportions of leaf litter, sand, vegetation, and rock between (a) Tropidurus semitaeniatus (×) and environmental availability (∆) (stress = 0.1534), and (b) Tropidurus hispidus (○) and environmental availability (∆) (stress = 0.0877). Proximity and distance between points indicates, respectively, similarity or dissimilarity.

Figure 4 in Diverging structures, perch heights, temperatures, and levels of sunlight of spatial niche dimensions ease the syntopic life of Tropidurus hispidus and Tropidurus semitaeniatus (Squamata: Tropiduridae)

Figure 4. Differences in distances from nearest potential shelters (cm, log) among types of shelter for Tropidurus semitaeniatus. The mean distance was longer from vegetation than from rock shelters. Upwards, the horizontal lines of the boxplots represent the minimum range, first quartile, median, third quartile, and maximum range. The unit of the original measurement scale is presented for the logarithmic values of the vertical axis.

Figure 2 in Diverging structures, perch heights, temperatures, and levels of sunlight of spatial niche dimensions ease the syntopic life of Tropidurus hispidus and Tropidurus semitaeniatus (Squamata: Tropiduridae)

Figure 2. Ordination by non-metric multidimensional scaling comparing proportions of shade, filtered sunlight, and full sunlight, air temperatures and substrate temperatures between (a) Tropidurus hispidus (○) and T. semitaeniatus (×) (stress = 0.1785), (b) T. hispidus (○) and environmental availability (∆) (stress = 0.1004), and (C) T. semitaeniatus (×) and that available in the environment (∆) (stress = 0.2534). Proximity and distance between points indicates, respectively, similarity or dissimilarity.

Figure 5 in Diverging structures, perch heights, temperatures, and levels of sunlight of spatial niche dimensions ease the syntopic life of Tropidurus hispidus and Tropidurus semitaeniatus (Squamata: Tropiduridae)

Figure 5. Frequency distribution (horizontal axis; in %) of perch heights (vertical axes; in cm) used by Tropidurus hispidus and Tropidurus semitaeniatus.

opennotspecifiedSep 2023View details →

Fig. 4 a–c in The roles of niche divergence, dispersal, and geology on the diversification of Neotropical true frogs from the Rana palmipes species group (Amphibia, Anura, Ranidae) during the Great American Biotic Interchange

Fig. 4 a–c Predicted niche occupancies (PNO) with horizontal axes representing the occupancy profiles of predictors for species (represented by different lines), and vertical axes representing the predicted suitability (Maxent "raw probabilities"). d–f Reconstruction of niche evolution based on maximum likelihood for mean tolerances obtained

opennotspecifiedSep 2023View details →

Fig. 2 in The roles of niche divergence, dispersal, and geology on the diversification of Neotropical true frogs from the Rana palmipes species group (Amphibia, Anura, Ranidae) during the Great American Biotic Interchange

Fig. 2 Best fit-model of ancestral area estimation for the Rana palmipes species group. a Geographical delimitation of the areas used to estimate ancestral areas and b ancestral areas estimated for the Rana palmipes species group (Ranidae). Arrows represent jump

opennotspecifiedSep 2023View details →

Fig. 3 in The roles of niche divergence, dispersal, and geology on the diversification of Neotropical true frogs from the Rana palmipes species group (Amphibia, Anura, Ranidae) during the Great American Biotic Interchange

Fig. 3 Age-range correlation (ARC) between node age and D index. a Phylogenetic tree and nodes compared. b Correlation plot between node age and D index, each point corresponding to a specific node in the phylogenetic tree (r.2 = 0.035, P = 0.7, intercept = 0.097, slope = 0.002)

Fig. 2 in Divergent evolution of mitogenomics in Cetartiodactyla niche adaptation

Fig. 2 The relative synonymous codon usage (RSCU) of Babyrousa babyrussa (a), Cephalorhynchus commersonii (b), Stenella clymene (c), and Stenella frontalis (d). Codon families are plotted on the X axis

Fig. 7 in Divergent evolution of mitogenomics in Cetartiodactyla niche adaptation

Fig. 7 Comparisons of ω values among 34 Cetartiodactyla species of different niches, based on 13 protein-coding genes (PCGs) and each PCG. CL, low-altitude; CM, marine; CH, high-altitude

Fig. 8 in Divergent evolution of mitogenomics in Cetartiodactyla niche adaptation

Fig. 8 Phylogenetic independent contrast analysis between different niches and root-to-tip ω values (Log10-transformed) of 13 PCGs dataset in 34 Cetartiodactyla species

Fig. 5 in Divergent evolution of mitogenomics in Cetartiodactyla niche adaptation

Fig. 5 Estimates of divergence time of Cetartiodactyla species with three fossil calibration points inferred from an analysis of 34 complete mitogenomes

Fig. 1 in Divergent evolution of mitogenomics in Cetartiodactyla niche adaptation

Fig. 1 Gene maps of mitogenome of Babyrousa babyrussa (a), Cephalorhynchus commersonii (b), Stenella clymene (c), and Stenella frontalis (d). The genes outside the circle are transcribed clockwise, while the genes inside are transcribed counterclockwise

Fig. 6 in Divergent evolution of mitogenomics in Cetartiodactyla niche adaptation

Fig. 6 Boxplot of molecular evolution rate (ω) of ND6 gene from 34 Cetartiodactyla species mitogenomes