Patterns Of Adaptive Radiation Research Articles

Phylogenetic relationships of Cuban and Caribbean Plumeria (Apocynaceae) based on the plastid genome

Abstract Plumeria L. (Apocynaceae) is a Neotropical genus mostly restricted to the Caribbean, which is cultivated in tropical gardens worldwide. Almost all ~27 species are endemic to the Caribbean Islands, except for four (Plumeria inodora Jacq., Plumeria obtusa L., Plumeria pudica Jacq., and Plumeria rubra L.) that are native to Central America and northern South America. Cuba harbours the largest diversity of the genus, with 13 endemic species. We present the first molecular phylogeny of the genus based on the nucleotide sequences of the complete plastid genome. Partial plastid genomes of 11 Plumeria species and one closely related species (Himatanthus sp.) were sequenced using long-PCR and next-generation sequencing. The recovered clades mostly grouped by single islands or closely neighboring islands. The phylogenetic relationships indicate patterns of adaptive radiation, with ecological shifts within these island-based clades and a west-to-east colonization route in the region. Plumeria rubra and Himatanthus sp. were resolved as sister to the rest of the genus. One unexpected finding was that P. pudica, a species restricted to the southern Caribbean Basin mainland, was recovered within the clade containing the Caribbean Island endemics, rendering the endemic group polyphyletic. Our study provides a phylogenetic framework for future studies that will need to include nuclear molecular markers and a more extensive sampling.

The speciation view: Disentangling multiple causes of adaptive and non‐adaptive radiation in terms of speciation

AbstractBiological diversification often includes burst of lineage splitting. Such “radiation” has been known to act as evolutionary arenas with the potential to generate unique phylogenetic clusters and further novel groups. Although these radiations when accompanied by ecological diversification, so‐called “adaptive radiation” have persisted as a central premise in evolutionary biology, the ecological and genetic mechanism of such rapid diversification has remained unclear. There are several critical definitions for the pattern of adaptive radiation, and those provide delimitation of adaptive and non‐adaptive radiation. That being said, only a few studies have provided any clear demarcations in our understanding of the adaptive and non‐adaptive causes of radiation from the mechanism of speciation. Here, we review the current consensus for the causes of adaptive radiation, especially along with the recent theoretical synthesis of “ecological speciation.” Further, we suggest the signature of adaptive and non‐adaptive radiation in the earliest stages of diversification from the viewpoint of speciation. These criteria from the speciation view are useful to find the cases with the signatures of adaptive/non‐adaptive radiation.

Convergent patterns of adaptive radiation between island and mainlandAnolislizards

AbstractUncovering convergent and divergent patterns of diversification is a major goal of evolutionary biology. On four Greater Antillean islands, Anolis lizards have convergently evolved sets of species with similar ecologies and morphologies (ecomorphs). However, it is unclear whether closely related anoles from Central and South America exhibit similar patterns of diversification. We generated an extensive morphological data set to test whether mainland Draconura-clade anoles are assignable to the Caribbean ecomorphs. Based on a new classification framework that accounts for different degrees of morphological support, we found morphological evidence for mainland representatives of all six Caribbean ecomorphs and evidence that many ecomorphs have also evolved repeatedly on the mainland. We also found strong evidence that ground-dwelling anoles from both the Caribbean and the mainland constitute a new and distinct ecomorph class. Beyond the ecomorph concept, we show that the island and mainland anole faunas exhibit exceptional morphological convergence, suggesting that they are more similar than previously understood. However, the island and mainland radiations are not identical, indicating that regional differences and historical contingencies can lead to replicate yet variable radiations. More broadly, our findings suggest that replicated radiations occur beyond island settings more often than previously recognized.

Convergent evolution of tree hydraulic traits in Amazonian habitats: implications for community assemblage and vulnerability to drought.

Amazonian droughts are increasing in frequency and severity. However, little is known about how this may influence species-specific vulnerability to drought across different ecosystem types. We measured 16 functional traits for 16 congeneric species from six families and eight genera restricted to floodplain, swamp, white-sand or plateau forests of Central Amazonia. We investigated whether habitat distributions can be explained by species hydraulic strategies, and if habitat specialists differ in their vulnerability to embolism that would make water transport difficult during drought periods. We found strong functional differences among species. Nonflooded species had higher wood specific gravity and lower stomatal density, whereas flooded species had wider vessels, and higher leaf and xylem hydraulic conductivity. The P50 values (water potential at 50% loss of hydraulic conductivity) of nonflooded species were significantly more negative than flooded species. However, we found no differences in hydraulic safety margin among species, suggesting that all trees may be equally likely to experience hydraulic failure during severe droughts. Water availability imposes a strong selection leading to differentiation of plant hydraulic strategies among species and may underlie patterns of adaptive radiation in many tropical tree genera. Our results have important implications for modeling species distribution and resilience under future climate scenarios.

In the rivers: Multiple adaptive radiations of cyprinid fishes (Labeobarbus) in Ethiopian Highlands

Multiple repeated patterns of adaptive radiation were revealed in cyprinid fish inhabiting the compact geographic region of the Ethiopian Highlands. We found four independently evolved radiations in the evolutionary hexaploid (2n = 150) Labeobarbus lineage based on matrilineal relationships of >800 individuals. Each radiation displayed similar patterns of mouth phenotype diversification, and included ecomorphs/species of the generalized, lipped, scraping (one or two), and large-mouthed (one to three) types. All radiations were detected in geographically isolated rivers, and originated from different ancestral populations. This is the first documented case in which numerous parallel radiations of fishes occurred–via different ways–in a riverine environment. Some radiations are very recent and monophyletic, while others are older and include ecomorphs that originated in separate mini flocks and later combined into one. The diversification bursts among Ethiopian Labeobarbus were detected in the mid-upper reaches of rivers (1050-1550 m above sea level), which likely offer ecological opportunities that include diverse habitats yet poor fauna (i.e. lower competition and relaxed selection). This promising example of parallel evolution of adaptive radiation warrants further investigation.

Dynamic Metasurface Antennas for Higher-order MIMO Systems in Indoor Environments

We propose a MIMO system using a dynamic cavity-backed metasurface antenna (DMA) as a transmit antenna to improve the channel capacity of indoor MIMO channels. The DMA is a printed cavity loaded with tunable metamaterial radiators and fed by radio frequency ports. The DMA can generate radiation patterns that are adaptive to MIMO channels by individual tuning of the metamaterial radiators. In this letter, we study a 4 $\times $ 4 MIMO system operating at 5.9 GHz, consisting of a simulated DMA as transmit antenna and a linear dipole array as receive antenna. Using a ray tracing technique, we simulate indoor MIMO channels and compute MIMO channel capacity at different receiver locations. We demonstrate that the adaptive radiation pattern generated by the DMA can increase the channel capacity. The MIMO system using the DMA can be low cost and low in power consumption, and can find applications where bandwidth, power, and cost represent constraints.

Design of Adaptive Planar Microstrip Patch Array Operating at 28 GHz for 5G Smart Mobile System

Smart antenna system has been studied extensively for the fifth generation of wireless communication systems, because it has made a system better performance of higher capacity and coverage as well as of power-saving. The present paper introduces a design of planar microstrip patch antenna array for a smart mobile system operating at 28 GHz. The present smart antenna has an adaptive radiation pattern that adjusts its main beam automatically to the desired direction by following the signal environment. This is based on the processing of an algorithm called the Least Mean Square (LMS) resulting in a change in the magnitude and phase of the feeding current for each element in the antenna array. From the obtained results, the main beam can be steered 180 degrees in the phi (azimuth) plane at a constant theta (elevation) angle. The planar antenna array was designed and simulated using CST Microwave Studio and MATLAB software that is used to find the required exciting current for each element. It is found that the antenna bandwidth is greater than 1 GHz while its gain is about 21 dB.

The paradox behind the pattern of rapid adaptive radiation: how can the speciation process sustain itself through an early burst?

Rapid adaptive radiation poses a distinct question apart from speciation and adaptation: what happens after one speciation event? That is, how are some lineages able to continue speciating through a rapid burst? This question connects global macroevolutionary patterns to microevolutionary processes. Here we review major features of rapid radiations in nature and their mismatch with theoretical models and what is currently known about speciation mechanisms. Rapid radiations occur on three major diversification axes - species richness, phenotypic disparity, and ecological diversity - with exceptional outliers on each axis. The paradox is that the hallmark early stage of adaptive radiation, a rapid burst of speciation and niche diversification, is contradicted by most existing speciation models which instead predict continuously decelerating speciation rates and niche subdivision through time. Furthermore, while speciation mechanisms such as magic traits, phenotype matching, and physical linkage of co-adapted alleles promote speciation, it is often not discussed how these mechanisms could promote multiple speciation events in rapid succession. Additional mechanisms beyond ecological opportunity are needed to understand how rapid radiations occur. We review the evidence for five emerging theories: 1) the 'transporter' hypothesis: introgression and the ancient origins of adaptive alleles, 2) the 'signal complexity' hypothesis: the dimensionality of sexual traits, 3) the connectivity of fitness landscapes, 4) 'diversity begets diversity', and 5) flexible stem/'plasticity first'. We propose new questions and predictions to guide future work on the mechanisms underlying the rare origins of rapid radiation.

Around the world in 170 million years

Paleontology![Figure][1] Dinosaurs followed a classic pattern of adaptive radiation as they spread across the planet. CREDIT: JULIUS T. CSOTONYI Dinosaurs were the dominant vertebrate on the planet for more than 170 million years. During that time, they dispersed and diversified into the

Noise emissions sources direction-finding in the process of their background air threats detection in radars with phased antenna array

We analyze two options of combined systems for spatial signal processing in radars with phased antenna array, where the detection of noiseless point targets with background noise emissions is accompanied by the direction finding of their sources. In the first option the direction finding of noise emissions is based on the shape analysis of the adaptive radiation pattern of the phased antenna array, formed during the adaptive target finding with background noise emissions. In the second option the bearing angles are determined on the basis of maxima of “spectral functions” of different evaluations of correlation matrix, formed on the basis of input readings. An example how to build such a combined system for spatial signal processing based on general adaptive grid filter is presented. It is shown that the effect of simultaneous target finding in external noise background and direction finding of their sources is achieved by single utilization of the most complex tuning operation of the adaptive grid filter. This operation is same for both of these tasks, and it is easier comparing to solving these two problems separately.

Lineage Diversity and Size Disparity in Musteloidea: Testing Patterns of Adaptive Radiation Using Molecular and Fossil-Based Methods.

Adaptive radiation is hypothesized to be a primary mechanism that drives the remarkable species diversity and morphological disparity across the Tree of Life. Tests for adaptive radiation in extant taxa are traditionally estimated from calibrated molecular phylogenies with little input from extinct taxa. With 85 putative species in 33 genera and over 400 described extinct species, the carnivoran superfamily Musteloidea is a prime candidate to investigate patterns of adaptive radiation using both extant- and fossil-based macroevolutionary methods. The species diversity and equally impressive ecological and phenotypic diversity found across Musteloidea is often attributed to two adaptive radiations coinciding with two major climate events, the Eocene-Oligocene transition and the Mid-Miocene Climate Transition. Here, we compiled a novel time-scaled phylogeny for 88% of extant musteloids and used it as a framework for testing the predictions of adaptive radiation hypotheses with respect to rates of lineage diversification and phenotypic evolution. Contrary to expectations, we found no evidence for rapid bursts of lineage diversification at the origin of Musteloidea, and further analyses of lineage diversification rates using molecular and fossil-based methods did not find associations between rates of lineage diversification and the Eocene-Oligocene transition or Mid-Miocene Climate Transition as previously hypothesized. Rather, we found support for decoupled diversification dynamics driven by increased clade carrying capacity in the branches leading to a subclade of elongate mustelids. Supporting decoupled diversification dynamics between the subclade of elongate mustelids and the ancestral musteloid regime is our finding of increased rates of body length evolution, but not body mass evolution, within the decoupled mustelid subclade. The lack of correspondence in rates of body mass and length evolution suggest that phenotypic evolutionary rates under a single morphological metric, even one as influential as mass, may not capture the evolution of diversity in clades that exhibit elongate body shapes. The discordance in evolutionary rates between body length and body mass along with evidence of decoupled diversification dynamics suggests that body elongation might be an innovation for the exploitation of novel Mid-Miocene resources, resulting in the radiation of some musteloids.

Patterns of morphological diversification of mainlandAnolislizards from northwestern South America

Anolis lizards are one of the most diverse vertebrate genera and are the classic example of adaptive radiation and convergent evolution. Anoles exhibit great morphological diversity produced by the ecological opportunity to exploit several arboreal niches. Anole radiation in the Caribbean islands is well studied, but the mainland radiation is less understood. We used a large morphological data set and a molecular phylogeny to describe the morphological diversification of anoles from northwestern South America, a region with the highest anole diversity on a mainland. We describe morphological diversity as summarized by ten morphotypes, defined mainly by body size, limb proportions, and subdigital lamellae. We show that some morphotypes are limited to forested lowlands and others to Andean highlands; by contrast, Anolis assemblages from tropical rainforests are comprised of the same four morphotypes. We demonstrate that morphological diversification followed a pattern of adaptive radiation across a landscape of adaptive peaks. Our results are consistent with the most recent hypothesis of convergence stated for Caribbean radiation, and demonstrate convergence between mainland morphotypes and Caribbean ecomorphs, which suggests that common processes are driving both radiations. © 2015 The Linnean Society of London

From dinosaurs to modern bird diversity: extending the time scale of adaptive radiation.

What explains why some groups of organisms, like birds, are so species rich? And what explains their extraordinary ecological diversity, ranging from large, flightless birds to small migratory species that fly thousand of kilometers every year? These and similar questions have spurred great interest in adaptive radiation, the diversification of ecological traits in a rapidly speciating group of organisms. Although the initial formulation of modern concepts of adaptive radiation arose from consideration of the fossil record, rigorous attempts to identify adaptive radiation in the fossil record are still uncommon. Moreover, most studies of adaptive radiation concern groups that are less than 50 million years old. Thus, it is unclear how important adaptive radiation is over temporal scales that span much larger portions of the history of life. In this issue, Benson et al. test the idea of a “deep-time” adaptive radiation in dinosaurs, compiling and using one of the most comprehensive phylogenetic and body-size datasets for fossils. Using recent phylogenetic statistical methods, they find that in most clades of dinosaurs there is a strong signal of an “early burst” in body-size evolution, a predicted pattern of adaptive radiation in which rapid trait evolution happens early in a group's history and then slows down. They also find that body-size evolution did not slow down in the lineage leading to birds, hinting at why birds survived to the present day and diversified. This paper represents one of the most convincing attempts at understanding deep-time adaptive radiations.

Ecological variation in South American geophagine cichlids arose during an early burst of adaptive morphological and functional evolution

Diversity and disparity are unequally distributed both phylogenetically and geographically. This uneven distribution may be owing to differences in diversification rates between clades resulting from processes such as adaptive radiation. We examined the rate and distribution of evolution in feeding biomechanics in the extremely diverse and continentally distributed South American geophagine cichlids. Evolutionary patterns in multivariate functional morphospace were examined using a phylomorphospace approach, disparity-through-time analyses and by comparing Brownian motion (BM) and adaptive peak evolutionary models using maximum likelihood. The most species-rich and functionally disparate clade (CAS) expanded more efficiently in morphospace and evolved more rapidly compared with both BM expectations and its sister clade (GGD). Members of the CAS clade also exhibited an early burst in functional evolution that corresponds to the development of modern ecological roles and may have been related to the colonization of a novel adaptive peak characterized by fast oral jaw mechanics. Furthermore, reduced ecological opportunity following this early burst may have restricted functional evolution in the GGD clade, which is less species-rich and more ecologically specialized. Patterns of evolution in ecologically important functional traits are consistent with a pattern of adaptive radiation within the most diverse clade of Geophagini.

Adaptive radiation and diversification in gall‐inducing insects in the Indian subcontinent: search for a pattern

The most striking behaviour among gall-inducing insects is that a majority of them are specialist organisms that display a high level of fidelity to their host plants. In a context of discussing species diversity among and richness of gall-inducing insects, this paper attempts to discuss the patterns of adaptive radiation evident in different gall-inducing insects of the Indian subcontinent, which is characterized by profound geological, vegetation, and climatic variations. As a case study, in this paper I have analyzed and discussed patterns of adaptive radiation apparent in gall-inducing Cecidomyiidae on Indian Anacardiaceae with a particular reference to Mangifera indica. The possible absence of resistance-breaking genes in Indian Cecidomyiidae on different Anacardiaceae and M. indica explains why these elements have not radiated and diversified as aggressively as the gall-inducing Eulophidae have done on different Eucalyptus taxa introduced into India as commercial plantation crops. Alternatively, the host-plant populations are, in high likelihood, restricting the gene flow between specific gall-midge populations, through their secondary chemistry because, the host-plant mediated impediments on the breeding behaviours impact on the radiation of gall-inducing insects. A significant majority of Indian gall-inducing insects show features of conservative diversification, and based on available evidence their conservative diversification appears to be strongly plant mediated. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Mechanisms of Speciation

Mechanisms of Speciation

A Phenotypic Point of View of the Adaptive Radiation of Crested Newts (Triturus cristatus Superspecies, Caudata, Amphibia).

The divergence in phenotype and habitat preference within the crested newt Triturus cristatus superspecies, examined across different ontogenetic stages, provides an excellent setting to explore the pattern of adaptive radiation. The crested newts form a well-supported monophyletic clade for which at least the full mitochondrial DNA phylogeny is resolved. Here we summarise studies that explored the variation in morphological (larval and adult body form, limb skeleton, and skull shape) and other phenotypic traits (early life history, developmental sequences, larval growth rate, and sexual dimorphism) to infer the magnitude and direction of evolutionary changes in crested newts. The phenotypic traits show a high level of concordance in the pattern of variation; there is a cline-like variation, from T. dobrogicus, via T. cristatus, T. carnifex, and T. macedonicus to the T. karelinii group. This pattern matches the cline of ecological preferences; T. dobrogicus is relatively aquatic, followed by T. cristatus. T. macedonicus, T. carnifex, and the T. karelinii group are relatively terrestrial. The observed pattern indicates that phenotypic diversification in crested newts emerged due to an evolutionary switch in ecological preferences. Furthermore, the pattern indicates that heterochronic changes, or changes in the timing and rate of development, underlie the observed phenotypic evolutionary diversification.

SEASONAL WATER STRESS TOLERANCE AND HABITAT ASSOCIATIONS WITHIN FOUR NEOTROPICAL TREE GENERA

We investigated the relationship between habitat association and physiological performance in four congeneric species pairs exhibiting contrasting distributions between seasonally flooded and terra firme habitats in lowland tropical rain forests of French Guiana, including Virola and Iryanthera (Myristicaceae), Symphonia (Clusiaceae), and Eperua (Caesalpiniaceae). We analyzed 10-year data sets of mapped and measured saplings (stems >150 cm in height and <10 cm diameter at breast height [dbh]) and trees (stems > or =10 cm dbh) across 37.5 ha of permanent plots covering a 300-ha zone, within which seasonally flooded areas (where the water table never descends below 1 m) have been mapped. Additionally, we tested the response of growth, survival, and leaf functional traits of these species to drought and flood stress in a controlled experiment. We tested for habitat preference using a modification of the torus translation method. Strong contrasting associations of the species pairs of Iryanthera, Virola, and Symphonia were observed at the sapling stage, and these associations strengthened for the tree stage. Neither species of Eperua was significantly associated with flooded habitats at the sapling stage, but E. falcata was significantly and positively associated with flooded forests at the tree stage, and trees of E. grandiflora were found almost exclusively in nonflooded habitats. Differential performance provided limited explanatory support for the observed habitat associations, with only congeners of Iryanthera exhibiting divergent sapling survival and tree growth. Seedlings of species associated with flooded forest tended to have higher photosynthetic capacity than their congeners at field capacity. In addition, they tended to have the largest reductions in leaf gas exchange and growth rate in response to experimental drought stress and the least reductions in response to experimental inundation. The corroboration of habitat association with differences in functional traits and, to a lesser extent, measures of performance provides an explanation for the regional coexistence of these species pairs. We suggest that specialization to seasonally flooded habitats may explain patterns of adaptive radiation in many tropical tree genera and thereby provide a substantial contribution to regional tree diversity.

Dynamic patterns of adaptive radiation

Adaptive radiation is defined as the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage. When it occurs, adaptive radiation typically follows the colonization of a new environment or the establishment of a "key innovation," which opens new ecological niches and/or new paths for evolution. Here, we take advantage of recent developments in speciation theory and modern computing power to build and explore a large-scale, stochastic, spatially explicit, individual-based model of adaptive radiation driven by adaptation to multidimensional ecological niches. We are able to model evolutionary dynamics of populations with hundreds of thousands of sexual diploid individuals over a time span of 100,000 generations assuming realistic mutation rates and allowing for genetic variation in a large number of both selected and neutral loci. Our results provide theoretical support and explanation for a number of empirical patterns including "area effect," "overshooting effect," and "least action effect," as well as for the idea of a "porous genome." Our findings suggest that the genetic architecture of traits involved in the most spectacular radiations might be rather simple. We show that a great majority of speciation events are concentrated early in the phylogeny. Our results emphasize the importance of ecological opportunity and genetic constraints in controlling the dynamics of adaptive radiation.

GEOGRAPHICAL CONTEXT OF SPECIATION IN A RADIATION OF HAWAIIAN TETRAGNATHA SPIDERS (ARANEAE, TETRAGNATHIDAE)

Abstract Adaptive radiation involves the diversification of species each adapted to exploit different ecological roles. I have studied a radiation of spiders in the genus Tetragnatha (Tetragnathidae) in the Hawaiian Islands to elucidate processes involved in such diversification. The temporal framework of the Hawaiian Islands allows examination of the changing pattern of adaptive radiation over time, as lineages have generally progressed down the island chain from older to younger islands. Species of Tetragnatha in the spiny-leg clade on any one island are typically most closely related to others on the same island, and the same set of ecological forms (ecomorphs) has evolved repeatedly on different islands. These results indicate that adaptive radiation frequently involves ecological divergence between sister taxa to allow multiple close relatives to co-occur in the same habitat. The current study examines the geographical context within which these species arose. I focus on a clade of 5 species that occ...