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291 results for “Ecological diversification”
Ecological diversification preceded geographical expansion during the evolutionary radiation of Cataglyphis desert ants
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Data from: On the causes of rapid diversification in the Páramos: Isolation by ecology and genomic divergence in Espeletia
How diversity arises and what is the relative role of allopatric and ecological divergence are among the most persistent questions in evolution and ecology. Here, we assessed whether ecological divergence has enhanced the diversification of the Neotropical alpine plant complex Espeletia, also known as frailejones. This genus has one of the highest diversification rates ever reported and is distributed in the world's fastest evolving biodiversity hotspot, the Páramo (Neotropical alpine grasslands at elevations of c. 2800–4700 m). Our goal was to determine whether ecology plays a role in divergence within the Espeletia complex by quantifying genome-wide patterns of ecological divergence. We characterized 162 samples of the three most common and contrasting ecotypes (distinct morphotypes occupying particular habitats) co-occurring in six localities in the northern Andes using Genotyping by Sequencing. Contrasting ecotypes were caulescent cloud forest populations, caulescent populations from wind-sheltered and well-irrigated depressions and acaulescent populations from wind-exposed drier slopes. We found high polymorphism with a total of 1,273 single nucleotide polymorphisms (SNPs) that defined the relationships among nine genetic clusters. We quantified allelic associations of these markers with localities and habitats using 18 different general and mixed-effects statistical models that accounted for phylogenetic distance. Despite that these models always yielded more SNPs associated with the localities, markers associated with the habitat types were recovered too. We found strong evidence for isolation-by-distance (IBD) across populations despite rampant gene flow, as expected for plant groups with limited seed dispersal. Contrasts between populations of different habitat types showed that an isolation-by-environment (IBE) trend emerged and masked the IBD signal. Maximum likelihood estimation of the number of migrants per generation (Nem) among ecotypes confirmed the IBE pattern. This result illustrates the importance of mountains' environmental variation at a local scale in generating rapid morphological radiations and maintaining multiple adaptations in a fast-evolving ecosystem like the Páramo.
Data from: Ecological and spatial patterns associated with diversification of the shrub genus Tetraglochin along Southern-Central Andes (Rosaceae)
In addition to the degree of geographical isolation (sympatry, parapatry, allopatry and peripatry), ecology can be an important factor promoting diversification of lineages, both by niche divergence as well as niche conservatism. Tetraglochin is a genus of shrubs with six species distributed along the Southern and Central Andes, from Peru to southern Argentina and central Chile. Although monophyly of the genus as the identity of its species are well established, spatiotemporal framework for its diversification and the potential role of the ecology and geography in the speciation process remain unknown. In the present study we analyzed diversification times and historical biogeography of the genus, and conducted different climatic niche and geographical range comparisons among its species to determine possible patterns associated with speciation. Results support the Pleistocene diversification, early along the Southern Andes and the Patagonian Steppe and subsequently in the Central Andes. Climatic niche divergence did not prove to be a major factor promoting speciation, but rather the phylogenetic niche conservatism. Our analyses also favored the sympatric model of speciation, although patterns from geographical range evolution are difficult to interpret due to the lability on the ancestral distributions, and therefore micro-allopatric or parapatric divergence associated with the glacial-interglacial cycles and climatic oscillations throughout the Quaternary should not be discarded. Other potential factors associated with diversification of Tetraglochin are also discussed.
Data from: Biogeography of scorpions in the Pseudouroctonus minimus complex (Vaejovidae) from south-western North America: implications of ecological specialization for pre-Quaternary diversification
Aim: The aim of this study was to assess the impact of pre-Quaternary tectonics and orogeny relative to that of Pleistocene climate change on diversification within the Pseudouroctonus minimus complex, a group of vaejovid scorpions with stenotopic habitat requirements. Location: South-western North America (United States and Mexico). Methods: Multilocus sequence data (1899 base pairs from two mitochondrial and two nuclear genes) were generated from 65 samples of scorpions in the minimus complex. Phylogeographical structure within the minimus complex was explored using model-based phylogenetic methods and a general mixed Yule coalescent model to identify independent geographical clusters. A time-calibrated multilocus species tree was reconstructed using a multispecies coalescent approach. Ancestral areas were estimated at divergence events across the tree using a probabilistic Bayesian approach. Results: Extensive geographical structure was evident within two well-supported clades. These clades probably diverged over 25 million years ago (Ma), based on estimated mean divergence dates, followed by 14 divergences in the Miocene (25–5 Ma) and 4 divergences in the Pliocene and Pleistocene (< 5 Ma). The ancestral origin of the minimus complex was reconstructed to be across California and the Mexican Highlands. The Chihuahuan Desert was colonized twice from the Mexican Highlands, and one dispersal event occurred from the Mexican Highlands back to California. Main conclusions: Spatial and temporal patterns of evolution in the minimus complex support predictions that stenotopy promoted pre-Quaternary diversification. Miocene and Pliocene geomorphology, perhaps in concert with climate change, induced allopatric divergence across the heterogeneous landscape of south-western North America. Stenotopic scorpions such as the minimus complex provide a model for exploring correlations between Earth history and biological diversification.
Data from: Testing alternative hypotheses for evolutionary diversification in an African songbird: rainforest refugia versus ecological gradients
Geographic isolation in rainforest refugia and local adaptation to ecological gradients may both be important drivers of evolutionary diversification. However, their relative importance and the underlying mechanisms of these processes remain poorly understood because few empirical studies address both putative processes in a single system. A key question is to what extent is divergence in signals that are important in mate and species recognition driven by isolation in rainforest refugia or by divergent selection across ecological gradients? We studied the little greenbul, Andropadus virens, an African songbird, in Cameroon and Uganda, to determine whether refugial isolation or ecological gradients better explain existing song variation. We then tested whether song variation attributable to refugial or ecological divergence was biologically meaningful using reciprocal playback experiments to territorial males. We found that much of the existing song variation can be explained by both geographic isolation and ecological gradients, but that divergence across the gradient, and not geographic isolation, affects male response levels. These data suggest that ecologically divergent traits, independent of historical isolation during glacial cycles, can promote reproductive isolation. Our study provides further support for the importance of ecology in explaining patterns of evolutionary diversification in ecologically diverse regions of the planet.
Data from: Ecological and evolutionary diversification within the genus Carex (Cyperaceae): consequences for community assembly in subarctic fens
The concept of limiting similarity predicts that closely related taxa are less likely to co-occur than expected by chance. The degree to which the phylogenetic relatedness in plant communities is in accord with limiting similarity has been little tested at the scale where the consequences of adaptive differentiation during speciation should be most evident: the scale of neighboring, congeneric plants within a community. To quantify species co-occurrence patterns in relation to environment, we sampled sedge species, their rooting level relative to the water table, and the water pH in 2,124 0.25 m² quadrats distributed across 29 subarctic fens in the central Labrador Peninsula. We estimated phylogenetic relationships using four DNA regions (ETS, ITS, matK, trnL-trnF) for all species of Carex (42), Eriophorum (6), and Trichophorum (2) in the region, of which 21, four, and two, respectively, occurred in the sampled fens. We demonstrate that closely related species of Carex are less likely to co-occur than expected by chance using 1) a probabilistic method to test the significance of pairwise co-occurrence patterns of species, and 2) linear mixed modeling to relate these patterns to phylogenetic relationships and ecological tolerances along gradients of substrate pH and rooting level in relation to the water table. The results also indicate that suites of species with significant mutual pairwise co-occurrence belong to distant lineages within the Cariceae-Dulichieae-Scirpeae clade of Cyperaceae and have stabilizing niche differences. We suggest that niche differentiation during the evolution and diversification of a clade of wetland Carex species over the past few million years, especially during the dynamic glacial cycles of the Pleistocene, has resulted in diverse sedge communities that share space and resources in harsh northern peatland habitats.
Data from: The cryptic origins of evolutionary novelty: 1,000-fold-faster trophic diversification rates without increased ecological opportunity or hybrid swarm
Ecological opportunity is frequently proposed as the sole ingredient for adaptive radiation into novel niches. An additional trigger may be genome-wide hybridization resulting from 'hybrid swarm'. However, these hypotheses have been difficult to test due to the rarity of comparable control environments lacking adaptive radiations. Here I exploit such a pattern in microendemic radiations of Caribbean pupfishes. I show that a sympatric three-species radiation on San Salvador Island, Bahamas diversified 1,445 times faster than neighboring islands in jaw length due to evolution of a novel scale-eating adaptive zone from a generalist ancestral niche. I then sampled 22 generalist populations on seven neighboring islands and measured morphological diversity, stomach content diversity, dietary isotopic diversity, genetic diversity, lake/island areas, macroalgae richness, and Caribbean-wide patterns of gene flow. None of these standard metrics of ecological opportunity or gene flow were associated with adaptive radiation, except for slight increases in macroalgae richness. Thus, exceptional trophic diversification is highly localized despite myriad generalist populations in comparable environmental and genetic backgrounds. This study provides a strong counterexample to the ecological/hybrid-swarm theories of adaptive radiation and suggests that diversification of novel specialists on a sparse fitness landscape is constrained by more than ecological opportunity and gene flow.
Data from: Ecological opportunity and diversification in a continental radiation of birds: climbing adaptations and cladogenesis in the Furnariidae
Ecological theories of adaptive radiation predict that ecological opportunity stimulates cladogenesis through its effects on competitive release and niche expansion. Given that key innovations may confer ecological opportunity, we investigate the effect of the acquisition of climbing adaptations on rates of cladogenesis in a major avian radiation, the Neotropical bird family Furnariidae, using a species-level phylogeny. Morphological specializations for vertical climbing originated in the woodcreepers ca. 23 Mya, well before that adaptation occurred in woodpeckers (Picidae) or in other potential competitors in South America. This suggests that the acquisition of climbing adaptations conferred ample ecological opportunity to early woodcreepers. Nonetheless, we found that increases in speciation rates in Furnariidae did not coincide with the acquisition of climbing adaptations, and that the relationship between the accumulation of climbing adaptations and rates of speciation was negative. In addition, we did not detect a diversity-dependent decline in woodcreeper diversification rates consistent with saturation of the trunk-climbing niche. These findings do not support the hypothesis that ecological opportunity related to trunk-foraging stimulated cladogenesis in this radiation. The negative effect of climbing on diversification may be mediated by an indirect positive effect of climbing on dispersal ability, which may reduce speciation rates over evolutionary time scales.
Data from: Genetic divergence is decoupled from ecological diversification in the Hawaiian Nesosydne planthoppers
Adaptive radiation involves ecological shifts coupled with isolation of gene pools. However, we know little about what drives the initial stages of divergence. We study a system in which ecological diversification is found within a chronologically well-defined geological matrix to provide insight into this enigmatic phase of radiation. We tested the hypothesis that a period of geographic isolation precedes ecological specialization in an adaptive radiation of host-specialized Hawaiian planthoppers. We examined population structure and history using mitochondrial and multiple independent microsatellite loci in a species whose geographic distribution on the island of Hawaii enabled us to observe the chronology of divergence in its very earliest stages. We found that genetic divergence is associated with geographic features but not different plant hosts and that divergence times are very recent and on the same timescales as the dynamic geology of the island. Our results suggest an important role for geography in the dynamics of the early stages of divergence.
Data from: Feeding ecology is the primary driver of beak shape diversification in waterfowl
The diversity of beak shapes among birds is often assumed to be largely the result of adaptations to different feeding behaviors and diets. However, this assumption has only been tested for a small subset of avian diversity, primarily within the order Passeriformes. Moreover, given the role of the beak in behaviors other than feeding and given that most previously identified beak-feeding associations concern beak size rather than shape, it remains unclear how much of beak shape diversity is explained by feeding ecology and what functional explanations account for these differences in shape. I quantified the association between beak shape and feeding ecology for 42 species in the bird order Anseriformes (waterfowl) using 3D curvature of the upper beak collected from museum specimens and continuous dietary data compiled from the literature. I also tested whether leverage or stress resistance of the beak explains the association between beak shape and feeding ecology. Diet is strongly and significantly correlated with beak shape in waterfowl. An ancestral beak shape reconstruction and the reconstructed diet of the anseriform fossil Presbyornis both support filter-feeding as ancestral for most waterfowl, followed by multiple, significantly convergent transitions from a duck-like beak toward a more goose-like beak. The evolution of a more goose-like beak is associated with increased consumption of leaves, decreased consumption of invertebrates, and an increase in mechanical advantage of the beak. Moreover, no association was identified between size (measured as either beak size or body mass) and feeding ecology nor between size and beak shape. These results demonstrate that feeding ecology has acted as the primary selective force in the diversification of waterfowl beak shapes, including the convergent originations of geese. Thus, rapid and convergent adaptation of the beak to feeding is not limited to passerines nor is it limited to size-correlated shape changes. The positive evolutionary correlation between mechanical advantage and herbivory shows that lever mechanics can explain the functional evolution of the kinetic upper beak in birds. These results also suggest that functions of the beak other than feeding may play a minor role in explaining overall beak shape diversity.
Data from: Intraspecific adaptive radiation: competition, ecological opportunity, and phenotypic diversification within species
Intraspecific variation in resource-use traits can have profound ecological and evolutionary implications. Among the most striking examples are resource polymorphisms, where alternative morphs that utilize different resources evolve within a population. An underappreciated aspect of their evolution is that the same conditions that favor resource polymorphism—competition and ecological opportunity—might foster additional rounds of diversification within already existing morphs. We examined these issues in spadefoot toad tadpoles that develop into either a generalist 'omnivore' or a specialist 'carnivore' morph. Specifically, we assessed the morphological diversity of tadpoles from natural ponds and experimentally induced carnivores reared on alternative diets. We also surveyed natural ponds to determine if the strength of intramorph competition and the diversity and abundance of dietary resources (measures of ecological opportunity) influenced the diversity of within-morph variation. We found that five omnivore and four carnivore types were present in natural ponds; alternative diets led to shape differences, some of which mirrored variation in the wild; and both competition and ecological opportunity were associated with enhanced morphological diversity in natural ponds. Such fine-scale intraspecific variation might represent an underappreciated form of biodiversity and might constitute a crucible of evolutionary innovation and diversification.
Data from: Protein expression parallels thermal tolerance and ecologic changes in the diversification of a diving beetle species complex
Physiological changes associated with evolutionary and ecological processes such as diversification, range expansion or speciation are still incompletely understood, especially for non-model species. Here we study differences in protein expression in response to temperature in a western Mediterranean diving beetle species complex, using two-dimensional differential gel electrophoresis with one Moroccan and one Iberian population each of Agabus ramblae and Agabus brunneus. We identified proteins with significant expression differences after thermal treatments comparing them with a reference EST library generated from one of the species of the complex (A. ramblae). The colonisation during the Middle Pleistocene of the Iberian peninsula by A. ramblae, where maximum temperatures and seasonality are lower than in the ancestral north African range, was associated with changes in the response to 27 °C in proteins related to energy metabolism. The subsequent speciation of A. brunneus from within populations of Iberian A. ramblae was associated with changes in the expression of several stress-related proteins (mostly chaperons) when exposed to 4 °C. These changes are in agreement with the known tolerance to lower temperatures of A. brunneus, which occupies a larger geographical area with a wider range of climatic conditions. In both cases, protein expression changes paralleled the evolution of thermal tolerance and the climatic conditions experienced by the species. However, although the colonisation of the Iberian peninsula did not result in morphological change, the speciation process of A. brunneus within Iberia involved genetic isolation and substantial differences in male genitalia and body size and shape.
Data from: Diversification rates of the "Old Endemic" murine rodents of Luzon Island, Philippines are inconsistent with incumbency effects and ecological opportunity
Diversity-dependent cladogenesis occurs when a colonizing lineage exhibits increasing interspecific competition as it ecologically diversifies. Repeated colonization of a region by closely related taxa may cause similar effects as species within each lineage compete with one another. This may be particularly relevant for secondary colonists, which could experience limited diversification due to competition with earlier, incumbent colonists over evolutionary time. We tested the hypothesis that an incumbent lineage may diminish the diversification of secondary colonists in two speciose clades of Philippine "Old Endemic" murine rodents—Phloeomyini and Chrotomyini—on the relatively old oceanic island of Luzon. Although phylogenetic analyses confirm the independent, non-contemporaneous colonization of Luzon by the ancestors of these two clades, we found no support for arrested diversification in either. Rather, it appears that diversification of both clades resulted from constant-rate processes that were either uniform or favored the secondary colonists (Chrotomyini), depending on the method used. Our results suggest that ecological incumbency has not played an important role in determining lineage diversification among Luzon murines, despite sympatric occurrence by constituent species within each lineage, and a substantial head start for the primary colonists.
Data from: When are adaptive radiations replicated in areas? Ecological opportunity and unexceptional diversification in West Indian dipsadine snakes (Colubridae: Alsophiini)
AIM: We examine diversification in Caribbean alsophiine snakes and hypothesize that, given ecological opportunity presented by colonizing the West Indies, alsophiines should show the signature of an early burst of diversification and associated low-within clade ecological and morphological disparification. We also test if changes in morphology or ecology are associated with changes in diversification rate, as trait-dependent diversification is hypothesized to affect historical inferences of diversification and disparification. Finally, as replicated radiations are found across the West Indies in the anoles, we test for significant differences in ecological and morphological assemblages and rates among the major island groups. LOCATION: The West Indies. METHODS: A time-calibrated phylogeny produced from six genes using relaxed clock methods in BEAST was constructed to examine ancestral area using LAGRANGE. Maximum body size and ecological niche were scored for all species in the phylogeny, and comparative phylogenetic methods in R using GEIGER, LASER, APE and our own code were used to examine diversification through time, disparification and trait-dependent diversification from this dated phylogeny. RESULTS: The pattern of species diversification did not differ significantly from the Yule model of diversification. Morphology and ecology fit a Brownian and white noise model of diversification, respectively. Although not significantly different, morphological disparification was lower than the Brownian null model, whereas ecological disparification was significantly greater than the null. Trait-dependent diversification analyses suggested that the constant null models provided the best fit to these data. There was no significant signal of rate variation among the major island groups for size, but moderate evidence for niche. MAIN CONCLUSIONS: Although ecological opportunity was similarly present for alsophiines as it was for anoles, the snakes fail to show an early burst of speciation. Potential reasons for this include the young age of the group, and staggered diversification due to waiting times between island colonization. In turn, ecological and morphological disparity do not necessarily follow predictable patterns related to species diversification. Thus, the presence of ecological opportunity alone is not necessarily sufficient to trigger replicated adaptive radiations in areas.
Data from: Leapfrogging the Mexican highlands: influence of biogeographical and ecological factors on the diversification of highland species
In order to understand the processes that generate and maintain diversity, it is important to disentangle the roles of ecology and geography in speciation. We investigated the biogeographical and ecological factors that influenced the diversification of tree frogs (genus Sarcohyla) in the Mexican highlands, a region with high levels of endemism. Using single nucleotide polymorphism data for 58 samples, we found support for seven distinct genetic clusters within the Sarcohyla bistincta species complex, corresponding to Sarcohyla calthula, Sarcohyla pentheter and five populations within S. bistincta. A species tree analysis using the multispecies coalescent model did not support the monophyly of the five S. bistincta populations. We used niche modelling to calculate the ecological overlap among lineages; we found a degree of overlapping for most of the lineages, suggesting that ecological differentiation did not play a key role in their genetic divergence. Speciation and population structure in the complex have been shaped primarily by geological events, landscape modifications and climate changes during the Pleistocene. We discuss the relevance of genetic diversity for inferring the degree of species threats and recovery for conservation assessments.
Fig. 2 in Climatic Niche Conservatism and Ecological Diversification in the Holarctic Cold-Dwelling Butterfly Genus Erebia
Fig. 2. Illustrative figures of European and Asian mountains (panels A, B) and ancestral reconstruction of climatic traits (panels C–G) for species-specific average values of WorldClim variables.The ancestral reconstructions are based on OU model of evolution in the butterfly genus Erebia.
Fig. 3 in Climatic Niche Conservatism and Ecological Diversification in the Holarctic Cold-Dwelling Butterfly Genus Erebia
Fig. 3. The relationships between climatic and elevation niche widths and niche position along the gradient of conditions occupied by the butterfly genus Erebia. The points correspond to the niche width (y-axis) and average value of a climate variable or elevation for individual species (x-axis).The best fit of generalized additive models (GAM) is shown by lines (separately for species of the European and the Asian clade). Statistical significance of the model fit is also shown. edf denotes the estimated degrees of freedom, which indicates the complexity of the nonlinear relationship (edf = 1 corresponds to a linear relationship).
Fig. 1 in Climatic Niche Conservatism and Ecological Diversification in the Holarctic Cold-Dwelling Butterfly Genus Erebia
Fig. 1. Phylogenetic relationships and divergence time estimates for the butterfly genus Erebia. The European clade diversified mainly in Europe, the Asian clade in Asia, although the geographic distribution of several species is not restricted to a single region (see Supp Fig. 3 [online only]). The full biogeographic reconstruction is shown in the Supp Figs. 3–5 (online only). Climatic PCA displays the distribution-based climatic data for all species of the European and the Asian clades.The polygons show the full extent of the conditions occupied by each clade (dotted lines) and the core 50% of the climatic niche (solid lines). The inset shows the correlation of individual bioclimatic variables with the first and second PCA axes.The bioclimatic variables (bio1, bio4, bio12, and bio15) displayed significant phylogenetic signal (Table 3).The European clade inhabits warmer, more humid, and less seasonal climate compared to the Asian clade.
Figure 9 in Is mimicry a diversification-driver in ants? Biogeography, ecology, ethology, genetics and morphology define a second West-Palaearctic Colobopsis species (Hymenoptera: Formicidae)
Figure 9. Above: distribution map of Colobopsis samples examined – countries where Colobopsis presence is known from the literature are highlighted in grey. Below: approximate distributions of other Camponotini (Camponotus barbaricus, of C. micans and of C. ruber) which resemble that of CSL Colobopsis.
Figure 10. Colobopsis imitans. A, B, E in Is mimicry a diversification-driver in ants? Biogeography, ecology, ethology, genetics and morphology define a second West-Palaearctic Colobopsis species (Hymenoptera: Formicidae)
Figure 10. Colobopsis imitans. A, B, E, worker (holotypus); C, D, F, G, soldier (specimen from the type locality). Scale bars: 0.5 mm. Pictures also available on AntWeb.org database, specimen codes: ANTWEB1041481 and ANTWEB1041482.
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