Evolution Of Niche Breadth Research Articles

Genomic factors shape carbon and nitrogen metabolic niche breadth across Saccharomycotina yeasts.

Organisms exhibit extensive variation in ecological niche breadth, from very narrow (specialists) to very broad (generalists). Two general paradigms have been proposed to explain this variation: (i) trade-offs between performance efficiency and breadth and (ii) the joint influence of extrinsic (environmental) and intrinsic (genomic) factors. We assembled genomic, metabolic, and ecological data from nearly all known species of the ancient fungal subphylum Saccharomycotina (1154 yeast strains from 1051 species), grown in 24 different environmental conditions, to examine niche breadth evolution. We found that large differences in the breadth of carbon utilization traits between yeasts stem from intrinsic differences in genes encoding specific metabolic pathways, but we found limited evidence for trade-offs. These comprehensive data argue that intrinsic factors shape niche breadth variation in microbes.

Evolution of realized niche breadth diversity driven by community dynamics.

Why many herbivorous insects are host plant specialists, with non-negligible exceptions, is a conundrum of evolutionary biology, especially because the host plants are not necessarily optimal larval diets. Here, I present a novel model of host plant preference evolution of two insect species. Because habitat preference evolution is contingent upon demographic dynamics, I integrate the evolutionary framework with the modern coexistence theory. The results show that the two insect species can evolve into a habitat specialist and generalist, when they experience both negative and positive frequency-dependent community dynamics. This happens because the joint action of positive and negative frequency dependence creates multiple (up to nine) eco-evolutionary equilibria. Furthermore, initial condition dependence due to positive frequency dependence allows specialization to poor habitats. Thus, evolved habitat preferences do not necessarily correlate with the performances. The model provides explanations for counterintuitive empirical patterns and mechanistic interpretations for phenomenological models of niche breadth evolution.

Thermal niche breadth and their relationship with sturnira bat species diversification

The interaction between climatic conditions and the ability of organisms to maintain homeostasis regulates the distribution of species on the planet. However, its influence on macroevolutionary dynamics is not well understood. It has been suggested that diversification rates will be different in lineages with narrow thermal niches (specialists) to diversification rates in generalist lineages, but the evidence for this is elusive. Here, we tested this hypothesis by using the most diverse (in species richness and geographic range variation) tropical bat genus within the Phyllostomidae family. We estimated the realized thermal niche breadth of Sturnira species from their geographic range and categorized them as generalists, cold specialists, or warm specialists. We compared dynamic evolutionary models that differ in 1) niche breadth evolution, 2) parental niche breadth inheritance, and 3) whether niche breadth evolution is associated with shifts in diversification rates. Our best-performing model indicates that most Sturnira species arose as specialists in warm climates and that over time, their niche breadth broadens, and just a subset of those species becomes specialists in cold environments. We found that the evolution of realized thermal niche breadth causes fluctuations in per-lineage rates of diversification, where warm specialists boast the highest speciation rates. However, we found no evidence of these changes in niche neither triggering nor being a result of speciation events themselves; this suggests that diversification events in Sturnira could instead depend on allopatric speciation processes such as the development of geographic barriers.

Linking changes in individual specialization and population niche of space use across seasons in the great evening bat (Ia io)

BackgroundThe niche breadth of an animal population comprises both within-individual and between-individual variation (individual specialization). Both components can be used to explain changes in population niche breadth, and this has been extensively investigated in dietary niche dimension studies. However, little is known about how changes in food resources or environmental factors across seasons affect changes in individual and population space use within the same population.MethodsIn this study, we used micro-GPS loggers to capture the space use of individuals and of a population of the great evening bat (Ia io) in summer and autumn. We used I. io as a model to investigate how individual spatial niche breadth and spatial individual specialization affect changes in population niche breadth (home range and core area sizes) across seasons. Additionally, we explored the drivers of individual spatial specialization.ResultsWe found that the population home range and the core area of I. io did not increase in autumn when insect resources were reduced. Moreover, I. io showed different specialization strategies in the two seasons: higher spatial individual specialization in summer and lower individual specialization but broader individual niche breadth in autumn. This trade-off may maintain the dynamic stability of the population spatial niche breadth across seasons and facilitate the population response to changes in food resources and environmental factors.ConclusionsLike diet, spatial niche breadth of a population also may be determined by a combination of individual niche breadth and individual specialization. Our work provides new insights into the evolution of niche breadth from the spatial dimension.

Evolutionary dynamics of climatic niche influenced the current geographical distribution of Viperidae (Reptilia: Squamata) worldwide

Abstract An understanding of patterns of climatic niche evolution has important implications for ecological and evolutionary theory and conservation planning. However, despite considerable testing, niche evolution studies continue to focus on clade-wide, homogeneous patterns, without considering the potentially complex dynamics (i.e. phylogenetic non-stationarity) along the evolutionary history of a clade. Here, we examine the dynamics of climatic niche evolution in vipers and discuss its implication for their current patterns of diversity and distribution. We use comparative phylogenetic methods and global-scale datasets, including 210 viper species with phylogenetic and climatic data. We find that climatic niche evolution in Viperidae shows an overall pattern of phylogenetic conservatism, but with different dynamics depending on the niche feature (niche breadth or niche position) and the evolutionary history of particular lineages within the family, thus resulting in phylogenetic non-stationarity. Indeed, we find several shifts in niche breadth evolution that were probably influenced by the main geological and environmental changes experienced during the evolutionary history of the family. These results highlight the importance of considering complex patterns of climatic niche evolution and their role in shaping patterns of diversity and distribution.

Effective specialist or jack of all trades? Experimental evolution of a crop pest in fluctuating and stable environments.

Understanding pest evolution in agricultural systems is crucial for developing effective and innovative pest control strategies. Types of cultivation, such as crop monocultures versus polycultures or crop rotation, may act as a selective pressure on pests' capability to exploit the host's resources. In this study, we examined the herbivorous mite Aceria tosichella (commonly known as wheat curl mite), a widespread wheat pest, to understand how fluctuating versus stable environments influence its niche breadth and ability to utilize different host plant species. We subjected a wheat-bred mite population to replicated experimental evolution in a single-host environment (either wheat or barley), or in an alternation between these two plant species every three mite generations. Next, we tested the fitness of these evolving populations on wheat, barley, and on two other plant species not encountered during experimental evolution, namely rye and smooth brome. Our results revealed that the niche breadth of A.tosichella evolved in response to the level of environmental variability. The fluctuating environment expanded the niche breadth by increasing the mite's ability to utilize different plant species, including novel ones. Such an environment may thus promote flexible host-use generalist phenotypes. However, the niche expansion resulted in some costs expressed as reduced performances on both wheat and barley as compared to specialists. Stable host environments led to specialized phenotypes. The population that evolved in a constant environment consisting of barley increased its fitness on barley without the cost of utilizing wheat. However, the population evolving on wheat did not significantly increase its fitness on wheat, but decreased its performance on barley. Altogether, our results indicated that, depending on the degree of environmental heterogeneity, agricultural systems create different conditions that influence pests' niche breadth evolution, which may in turn affect the ability of pests to persist in such systems.

Niche differentiation and evolution of the wood decay machinery in the invasive fungus Serpula lacrymans

Ecological niche breadth and the mechanisms facilitating its evolution are fundamental to understanding adaptation to changing environments, persistence of generalist and specialist lineages and the formation of new species. Woody substrates are structurally complex resources utilized by organisms with specialized decay machinery. Wood-decaying fungi represent ideal model systems to study evolution of niche breadth, as they vary greatly in their host range and preferred decay stage of the substrate. In order to dissect the genetic basis for niche specialization in the invasive brown rot fungus Serpula lacrymans, we used phenotyping and integrative analysis of phylogenomic and transcriptomic data to compare this species to wild relatives in the Serpulaceae with a range of specialist to generalist decay strategies. Our results indicate specialist species have rewired regulatory networks active during wood decay towards decreased reliance on enzymatic machinery, and therefore nitrogen-intensive decay components. This shift was likely accompanied with adaptation to a narrow tree line habitat and switch to a pioneer decomposer strategy, both requiring rapid colonization of a nitrogen-limited substrate. Among substrate specialists with narrow niches, we also found evidence for pathways facilitating reversal to generalism, highlighting how evolution may move along different axes of niche space.

The problem of mediocre generalists: population genetics and eco-evolutionary perspectives on host breadth evolution in pathogens.

Many of our theories for the generation and maintenance of diversity in nature depend on the existence of specialist biotic interactions which, in host–pathogen systems, also shape cross-species disease emergence. As such, niche breadth evolution, especially in host–parasite systems, remains a central focus in ecology and evolution. The predominant explanation for the existence of specialization in the literature is that niche breadth is constrained by trade-offs, such that a generalist is less fit on any particular environment than a given specialist. This trade-off theory has been used to predict niche breadth (co)evolution in both population genetics and eco-evolutionary models, with the different modelling methods providing separate, complementary insights. However, trade-offs may be far from universal, so population genetics theory has also proposed alternate mechanisms for costly generalism, including mutation accumulation. However, these mechanisms have yet to be integrated into eco-evolutionary models in order to understand how the mechanism of costly generalism alters the biological and ecological circumstances predicted to maintain specialism. In this review, we outline how population genetics and eco-evolutionary models based on trade-offs have provided insights for parasite niche breadth evolution and argue that the population genetics-derived mutation accumulation theory needs to be better integrated into eco-evolutionary theory.

Experimental evolution for niche breadth in bacteriophage T4 highlights the importance of structural genes.

Ecologists have long studied the evolution of niche breadth, including how variability in environments can drive the evolution of specialism and generalism. This concept is of particular interest in viruses, where niche breadth evolution may explain viral disease emergence, or underlie the potential for therapeutic measures like phage therapy. Despite the significance and potential applications of virus–host interactions, the genetic determinants of niche breadth evolution remain underexplored in many bacteriophages. In this study, we present the results of an evolution experiment with a model bacteriophage system, Escherichia virus T4, in several host environments: exposure to Escherichia coli C, exposure to E. coli K‐12, and exposure to both E. coli C and E. coli K‐12. This experimental framework allowed us to investigate the phenotypic and molecular manifestations of niche breadth evolution. First, we show that selection on different hosts led to measurable changes in phage productivity in all experimental populations. Second, whole—genome sequencing of experimental populations revealed signatures of selection. Finally, clear and consistent patterns emerged across the host environments, especially the presence of new mutations in phage structural genes—genes encoding proteins that provide morphological and biophysical integrity to a virus. A comparison of mutations found across functional gene categories revealed that structural genes acquired significantly more mutations than other categories. Our findings suggest that structural genes are central determinants in bacteriophage niche breadth.

Asexual parasites and their extraordinary host ranges.

In diverse parasite taxa, from scale insects to root-knot nematodes, asexual lineages have exceptionally large host ranges, larger than those of their sexual relatives. Phylogenetic comparative studies of parasite taxa indicate that increases in host range and geographic range increase the probability of establishment of asexual lineages. At first pass, this convergence of traits appears counter-intuitive: intimate, antagonistic association with an enormous range of host taxa correlates with asexual reproduction, which should limit genetic variation within populations. Why would narrow host ranges favor sexual parasites and large host ranges favor asexual parasites? To take on this problem I link theory on ecological specialization to the two predominant hypotheses for the evolution of sex. I argue that both hypotheses predict a positive association between host range and the probability of invasion of asexual parasites, mediated either by variation in population size or in the strength of antagonistic coevolution. I also review hypotheses on colonization and the evolution of niche breadth in asexual lineages. I emphasize parasite taxa, with their diversity of reproductive modes and ecological strategies, as valuable assets in the hunt for solutions to the classic problems of the evolution of sex and geographic parthenogenesis.

Using niche breadth theory to explain generalization in mutualisms.

For a mutualism to remain evolutionarily stable, theory predicts that mutualists should limit their associations to high-quality partners. However, most mutualists either simultaneously or sequentially associate with multiple partners that confer the same type of reward. By viewing mutualisms through the lens of niche breadth evolution, we outline how the environment shapes partner availability and relative quality, and ultimately a focal mutualist's partner breadth. We argue that mutualists that associate with multiple partners may have a selective advantage compared to specialists for many reasons, including sampling, complementarity, and portfolio effects, as well as the possibility that broad partner breadth increases breadth along other niche axes. Furthermore, selection for narrow partner breadth is unlikely to be strong when the environment erodes variation in partner quality, reduces the costs of interacting with low-quality partners, spatially structures partner communities, or decreases the strength of mutualism. Thus, we should not be surprised that most mutualists have broad partner breadth, even if it allows for ineffective partners to persist.

Evolution of Ecological Niche Breadth

How ecological niche breadth evolves is central to adaptation and speciation and has been a topic of perennial interest. Niche breadth evolution research has occurred within environmental, ecological, evolutionary, and biogeographical contexts, and although some generalities have emerged, critical knowledge gaps exist. Performance breadth trade-offs, although long invoked, may not be common determinants of niche breadth evolution or limits. Niche breadth can expand or contract from specialist or generalist lineages, and so specialization need not be an evolutionary dead end. Whether niche breadth determines diversification and distribution breadth and how niche breadth is partitioned among individuals and populations within a species are important but particularly understudied topics. Molecular genetic and phylogenetic techniques have greatly expanded understanding of niche breadth evolution, but field studies of how niche breadth evolves are essential for providing mechanistic details and allowing the development of comprehensive theory and improved prediction of biological responses under global change.

Linking Life-History Traits, Ecology, and Niche Breadth Evolution in North American Eriogonoids (Polygonaceae)

Macroevolutionary and microevolutionary studies provide complementary explanations of the processes shaping the evolution of niche breadth. Macroevolutionary approaches scrutinize factors such as the temporal and spatial environmental heterogeneities that drive differentiation among species. Microevolutionary studies, in contrast, focus on the processes that affect intraspecific variability. We combine these perspectives by using macroevolutionary models in a comparative study of intraspecific variability. We address potential differences in rates of evolution of niche breadth and position in annual and perennial plants of the Eriogonoideae subfamily of the Polygonaceae. We anticipated higher rates of evolution in annuals than in perennials owing to differences in generation time that are paralleled by rates of molecular evolution. Instead, we found that perennial eriogonoid species present greater environmental tolerance (wider climate niche) than annual species. Niche breadth of perennial species has evolved two to four times faster than in annuals, while niche optimum has diversified more rapidly among annual species than among perennials. Niche breadth and average elevation of species are correlated. Moreover, niche breadth increases more rapidly with mean species elevation in perennials than in annuals. Our results suggest that both environmental gradients and life-history strategy influence rates and patterns of niche breadth evolution.

Use of an Exotic Host Plant Affects Mate Choice in an Insect Herbivore

The colonization of exotic plants by herbivorous insects has provided opportunities for investigating causes and consequences of the evolution of niche breadth. The butterfly Lycaeides melissa utilizes exotic alfalfa, Medicago sativa, which is a relatively poor larval resource, and previous studies have found that caterpillars that consume M. sativa develop into smaller and less fecund adults. Here we investigate the effect of smaller female body size on male mate preference, a previously unexplored consequence of novel host use. Smaller females, which developed on the exotic host, were less likely to be visited by males. This result was confirmed with a second set of choice tests involving females reared on a single plant species, thus ruling out host-specific confounding factors. We suggest that an effect on mate choice be considered part of the complex suite of factors determining persistence of herbivorous insects following colonization of new habitats or resources.

Host range evolution is not driven by the optimization of larval performance: the case of Lycaeides melissa (Lepidoptera: Lycaenidae) and the colonization of alfalfa

Herbivorous insects that have recently incorporated novel hosts into their diet provide unique opportunities for understanding factors that promote or constrain the evolution of niche breadth. Lycaeides melissa has colonized both cultivated and feral alfalfa (Medicago sativa) throughout much of North America within the past 200 years. We investigated the quality of the novel host as a resource for juvenile development, and asked if the novel host is a preferred host for oviposition relative to a native host (Astragalus canadensis). Larval-performance and oviposition-preference were examined using L. melissa individuals from a population associated with both M. sativa and A. canadensis, and oviposition-preference was also examined in another population associated exclusively with M. sativa. In addition, we investigated the effects of M. sativa and A. canadensis flowers on both preference and performance. Only one of the hosts, M. sativa, has flowers that are accessible to nectaring butterflies, and we hypothesized that the presence of flowers could affect female behavior. We find that the novel host is a relatively poor larval resource: adults that were reared as larvae on M. sativa were roughly one-third the size of adults that were reared on the native host, A. canadensis. The native host, Astragalus canadensis, is the preferred host in choice experiments involving only foliage. However, when flowers were included in preference assays, the native and novel hosts received similar numbers of eggs. Thus, the presence of flowers on hosts in the field might influence the utilization of a novel and inferior larval resource. These results are consistent with a model in which host shifts are driven by adult behavior that does not directly optimize larval performance.

DETECTING ECOLOGICAL TRADE-OFFS USING SELECTION EXPERIMENTS

Theories of the evolution of niche breadth usually depend on the assumption that genotypes that are well adapted to exploit one habitat or resource are not well adapted to others. Such “trade-offs” are often apparent in interspecific comparisons, but have been harder to document at the within-population level. Selection experiments provide a promising means for detecting within-population trade-offs: if selection for adaptation to one environment (e.g., diet, host, temperature) reproducibly lowers fitness in another, trade-offs are the likeliest explanation. Here, I describe strategies for using selection experiments to detect ecological trade-offs and discuss some of the ambiguities that can arise in interpreting the results of such experiments. I also review two sets of studies that found evidence for trade-offs using selection experiments.

Matings Systems and the Evolution of Niche Breadth.

Several theoretical studies of niche breadth evolution have shown that niche breadth expansion can only occur under a limited set of conditions. These studies have assumed that mating pairs form at random within spatial subpopulations. I show here that nonrandom mating within spatial subpopulations can greatly alter niche breadth evolution. Niche breadth expansion is restricted by assortative mating but is permitted by sexual selection. When new populations are formed by a single pulse of immigrants, the ability to persist in novel but similar environments is enhanced by sexual selection. When new populations receive a constant stream of immigrants, sexual selection allows the evolution of increased niche breadth even when the novel environment is very different from the ancestral environment. These results suggest that species lineages that exhibit sexual selection will have broader niches than species lineages that mate randomly or assortatively.

Matings Systems and the Evolution of Niche Breadth

Matings Systems and the Evolution of Niche Breadth

The Red Queen Beats the Jack-Of-All-Trades: The Limitations on the Evolution of Phenotypic Plasticity and Niche Breadth

The evolution of niche breadth or phenotypic plasticity is often assumed to be limited by negative genetic correlations among fitness in different environments, but these trade-offs are rarely observed. Many other constraints can reduce the mean niche breadth of species. This article discusses one of these limitations-that species with broader niche breadths can have a slower rate of evolutionary response. Species with narrower niche breadths have higher probabilities of fixing beneficial alleles, taking less time to do so; they have fewer deleterious alleles drifting to fixation (a lighter drift load) and a lower frequency of deleterious alleles at mutation-selection equilibrium (a lighter mutation load). These patterns are true even with no correlation at all between fitness in different environments; no trade-offs are assumed. Furthermore, niche breadth is likely to evolve to be more narrow, because of the association between location and alleles favored in local habitats for individuals with reduced migration, assortative mating, or habitat selection. The evolution of niche breadth and plasticity is not a simple function of the fitness in different environments; understanding niche breadth evolution requires consideration of the limitations of the evolutionary process per se.

Evolution of Niche Breadth in Populations of Ants

Both the mean forager size and the variability in forager size within colonies of ants are positively correlated with niche breadth on two dimensions-size of foraging area and diet. In colonies that feed on seeds, absolute size of the foragers is related to the size of seeds taken; in colonies that feed on insects, absolute size of the foragers is related to foraging distance. The percent variation in forager size is best correlated, for all colony types, with size of the foraging area. In island communities with fewer ant species, the mean forager size is smaller and the coefficient of variation in forager size greater. The presence of slaves was found to increase both the range of foraging temperatures and the variety of foods utilized by slave-making colonies.