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Showing papers by "Jonathan B. Losos published in 2013"


Journal ArticleDOI
19 Jul 2013-Science
TL;DR: For example, this paper showed that diversification on similar Simpsonian landscapes leads to striking convergence of entire faunas on four islands in the Caribbean Anolis lizards, indicating that the adaptive landscape may give rise to predictable evolutionary patterns in nature, that adaptive peaks may be stable over macroevolutionary time and that available geographic area influences the ability of lineages to discover new adaptive peaks.
Abstract: G. G. Simpson, one of the chief architects of evolutionary biology’s modern synthesis, proposed that diversification occurs on a macroevolutionary adaptive landscape, but landscape models are seldom used to study adaptive divergence in large radiations. We show that for Caribbean Anolis lizards, diversification on similar Simpsonian landscapes leads to striking convergence of entire faunas on four islands. Parallel radiations unfolding at large temporal scales shed light on the process of adaptive diversification, indicating that the adaptive landscape may give rise to predictable evolutionary patterns in nature, that adaptive peaks may be stable over macroevolutionary time, and that available geographic area influences the ability of lineages to discover new adaptive peaks.

372 citations


01 Jan 2013
TL;DR: For Caribbean Anolis lizards, diversification on similar Simpsonian landscapes leads to striking convergence of entire faunas on four islands, indicating that the adaptive landscape may give rise to predictable evolutionary patterns in nature, that adaptive peaks may be stable over macroevolutionary time, and that available geographic area influences the ability of lineages to discover new adaptive peaks.

302 citations


Journal ArticleDOI
TL;DR: A novel application of structural equation modelling is used to quantify the contributions of ecological and geographical isolation to spatial genetic divergence in 17 species of Anolis lizards, suggesting that despite the proposed ubiquity of ecological divergence, non-ecological factors play the dominant role in the evolution of spatial genetic separation.
Abstract: Investigating the properties of ecological landscapes that influence gene flow among populations can provide key insights into the earliest stages of biological divergence. Both ecological and geographical factors can reduce gene flow, which can lead to population divergence, but we know little of the relative strengths of these phenomena in nature. Here, we use a novel application of structural equation modelling to quantify the contributions of ecological and geographical isolation to spatial genetic divergence in 17 species of Anolis lizards. Our comparative analysis shows that although both processes contributed significantly, geographical isolation explained substantially more genetic divergence than ecological isolation (36.3 vs. 17.9% of variance respectively), suggesting that despite the proposed ubiquity of ecological divergence, non-ecological factors play the dominant role in the evolution of spatial genetic divergence.

237 citations


Journal ArticleDOI
TL;DR: It is suggested that the rise in esteem of ECD has outpaced available data and that more complete, rather than simply more, case studies are needed.
Abstract: Ecological character displacement (ECD), the evolutionary divergence of competing species, has oscillated wildly in scientific opinion. Initially thought to play a central role in community assembly and adaptive radiation, ECD recovered from a 1980s nadir to present-day prominence on the strength of many case studies compiled in several influential reviews. However, we reviewed recent studies and found that only nine of 144 cases are strong examples that have ruled out alternative explanations for an ECD-like pattern. We suggest that the rise in esteem of ECD has outpaced available data and that more complete, rather than simply more, case studies are needed. Recent years have revealed that evolutionary change can be observed as it occurs, opening the door to experimental field studies as a new approach to studying ECD.

167 citations


Journal ArticleDOI
TL;DR: New theoretical and conceptual frameworks are required for evolutionary biology to capitalize on the wealth of data now becoming available from the study of genomes, phenotypes, and organisms in their natural environments.
Abstract: New theoretical and conceptual frameworks are required for evolutionary biology to capitalize on the wealth of data now becoming available from the study of genomes, phenotypes, and organisms - including humans - in their natural environments.

137 citations



Journal ArticleDOI
TL;DR: Using geometric morphometric analysis of head shape for 50 Anolis species, it is shown that two clades have converged on extreme levels of sexual dimorphism through similar, male‐specific changes in facial morphology.
Abstract: Studies integrating evolutionary and developmental analyses of morphological variation are of growing interest to biologists as they promise to shed fresh light on the mechanisms of morphological diversification. Sexually dimorphic traits tend to be incredibly divergent across taxa. Such diversification must arise through evolutionary modifications to sex differences during development. Nevertheless, few studies of dimorphism have attempted to synthesize evolutionary and developmental perspectives. Using geometric morphometric analysis of head shape for 50 Anolis species, we show that two clades have converged on extreme levels of sexual dimorphism through similar, male-specific changes in facial morphology. In both clades, males have evolved highly elongate faces whereas females retain faces of more moderate proportion. This convergence is accomplished using distinct developmental mechanisms; one clade evolved extreme dimorphism through the exaggeration of a widely shared, potentially ancestral, developmental strategy whereas the other clade evolved a novel developmental strategy not observed elsewhere in the genus. Together, our analyses indicate that both shared and derived features of development contribute to macroevolutionary patterns of morphological diversity among Anolis lizards.

73 citations


Journal ArticleDOI
TL;DR: It is found that thermal biology exhibits more divergence among recently diverged Anolis taxa than does morphology; and diversification of thermal biology among all species often follows diversification in morphology, remarkably consistent with predictions made by anole biologists in the 1960s and 1970s.
Abstract: Species-rich adaptive radiations typically diversify along several distinct ecological axes, each characterized by morphological, physiological, and behavioral adaptations. We test here whether different types of adaptive traits share similar patterns of evolution within a radiation by investigating patterns of evolution of morphological traits associated with microhabitat specialization and of physiological traits associated with thermal biology in Anolis lizards. Previous studies of anoles suggest that close relatives share the same "structural niche" (i.e., use the same types of perches) and are similar in body size and shape, but live in different "climatic niches" (i.e., use habitats with different insolation and temperature profiles). Because morphology is closely tied to structural niche and field active body temperatures are tied to climatic niches in Anolis, we expected phylogenetic analyses to show that morphology is more evolutionarily conservative than thermal physiology. In support of this hypothesis, we find (1) that thermal biology exhibits more divergence among recently diverged Anolis taxa than does morphology; and (2) diversification of thermal biology among all species often follows diversification in morphology. These conclusions are remarkably consistent with predictions made by anole biologists in the 1960s and 1970s.

62 citations


Journal ArticleDOI
TL;DR: These results suggest that, rather than act as mutually exclusive alternatives, multiple dimensions of the ecological niche, including climatic limits, biotic interactions and dispersal capacity, interact to shape species distributions and that local interactions can influence the broad-scale geography of species in a predictable way.
Abstract: Aim To test the role of climate, dispersal limitation and biotic interactions in limiting species’ distributions within an island adaptive radiation by integrating species traits, phylogeny and estimates of dispersal cost into climate-based species distribution models. Location Hispaniola. Methods Focusing on 26 species of Anolis lizards, we used multivariate adaptive regression splines to evaluate the contribution of climate, species interactions, phylogenetic history and dispersal limitation to species distributional limits. For each species, we mapped the morphological similarity of congenerics using traits of known ecological import and predicted that species would be less likely to occur in climatically suitable areas if they were inhabited by ecologically similar species. Dispersal limitation was incorporated by generating spatially explicit estimates of dispersal cost, based on inferred habitat suitability. We compared models including morphological similarity, dispersal cost, phylogeny and climate with climate-only models. Results were evaluated against a null model that conserved the spatial structure of species occurrences. Results Climate had a dominant role in shaping species distributions. However, for over one-third of species we also found evidence consistent with supplemental effects of species interactions, i.e. ecological niche incumbency. These species were less likely to occur in climatically suitable areas inhabited by a morphologically similar species. Dispersal limitation also supplemented climatic limits in most species. These results were robust to co-variation with phylogeny and to comparison with our null model. Conclusions These results suggest that, rather than act as mutually exclusive alternatives, multiple dimensions of the ecological niche, including climatic limits, biotic interactions and dispersal capacity, interact to shape species distributions and that local interactions can influence the broad-scale geography of species in a predictable way.

37 citations


Journal ArticleDOI
TL;DR: Phenotypic variation in Anolis lizards is found to be adaptive as confirmed by convergence in populations occurring in similar habitats in different mountain ranges.
Abstract: results to patterns observed at a deeper, macroevolutionary level. We tested whether evolution is a deterministic process with similar outcomes during different stages of the adaptive radiation of Anolis lizards. Using a clade of terrestrial–scansorial lizards in the genus Anolis, we inferred the adaptive basis of spatial variation among contemporary populations and tested whether axes of phenotypic differentiation among them mirror known axes of diversification at deeper levels of the anole radiation. Nonparallel change associated with genetic divergence explains the vast majority of geographic variation. However, we found phenotypic variation to be adaptive as confirmed by convergence in populations occurring in similar habitats in different mountain ranges. Morphological diversification among populations recurs deterministically along two axes of diversification previously identified in the anole radiation, but the characters involved differ from those involved in adaptation at higher levels of anole phylogeny.

34 citations


Journal ArticleDOI
TL;DR: This study reports on the origins of a shared design of a territorial display among Anolis species of lizards from two island radiations in the Caribbean and shows how adaptation to common environmental variables can drive the evolution of adaptive, convergent signals in distantly related species.

Journal ArticleDOI
TL;DR: Anolis lizards exhibit a remarkable degree of diversity in the shape, colour, pattern and size of their dewlaps as discussed by the authors, which has been reported in one species, Anolis lineatus, and then on only one of the two islands from which it occurs.
Abstract: Anolis lizards exhibit a remarkable degree of diversity in the shape, colour, pattern and size of their dewlaps. Asymmetry, where one side of the dewlap differs in pattern or colour from the other, has only been reported in one species, Anolis lineatus, and then on only one of the two islands from which it occurs. Given the importance of the dewlap in intra- and interspecific signalling, we expanded on previous work by (1) investigating whether the reported asymmetry actually occurs and, if so, whether it occurs on animals from both Aruba and Curacao; (2) examining whether populations differ in other aspects of their morphology or ecology; and (3) resolving the evolutionary relationships and the history of the two populations. We confirmed the presence of the asymmetrical dewlap on Curacao and found that the asymmetry extends to populations on Aruba as well. Animals on Curacao were smaller overall than populations from Aruba with relatively shorter metatarsals, radii, and tibias but relatively deeper heads, longer jaws, and wider and more numerous toepads on fore and hind feet. Habitat use did not differ significantly between the islands. We found populations on Aruba and Curacao to be reciprocally monophyletic with an early Pleistocene divergence of populations on the two islands. Neutrality tests indicate that neither population has seen any recent reduction in population size, making it unlikely that the asymmetry is a result of founder effects or is some other consequence of reduced genetic variation. A variety of factors likely account for the remarkable and unique dewlap morphology exhibited by this species, although more detailed field studies are required to test these hypotheses. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110, 409–426.

Journal ArticleDOI
08 Mar 2013-Science
TL;DR: It is read with deep concern of plans to drastically reduce the role of scientific research at one of the world's greatest museums of natural history, Chicago's Field Museum, and urged the Museum's authorities and supporters to find a way to prevent such a calamity.
Abstract: Great natural history museums are among the world's premier institutions of scientific research, training, and education. The research produced by these museums, based on their collections of biological, geological, and anthropological specimens, has been of incalculable importance in formulating and testing the most fundamental theories and principles of these and related disciplines. In the biological sciences, for instance, contributions from past curators of these collections form the pillars of modern evolutionary biology [e.g., ([ 1 ][1]–[ 3 ][2])]. We therefore read with deep concern of plans to drastically reduce the role of scientific research at one of the world's greatest museums of natural history, Chicago's Field Museum ("Budget crunch to shrink science programs at Chicago's Field Museum," V. Morell, News & Analysis, 4 January, p. [19][3]). The collections of the Field Museum are an irreplaceable scientific resource, and the scientists who care for, augment, and make them available for study by others are also renowned contributors to science in their own right. Their loss would be a blow not just to the Museum, but to the scientific enterprise as a whole. In making the bequest that endowed the Smithsonian, James Smithson epitomized what has become the mission of modern natural history museums: They are institutions for "the increase and diffusion of knowledge" ([ 4 ][4]). Many science museums can mount exhibits for the diffusion of knowledge, but only museums such as the Field, with its collections and scientists, can contribute so much to its increase. For the Field Museum to abandon this duty would be unconscionable. We urge the Museum's authorities and supporters to find a way to prevent such a calamity. 1. [↵][5]1. E. Mayr , Systematics and the Origin of Species (Columbia Univ. Press, New York, 1942). 2. 1. G. G. Simpson , Tempo and Mode in Evolution (Columbia Univ. Press, New York, 1944). 3. [↵][6]1. B. Rensch , Neuere Probleme der Abstammungslehre (Enke, Stuttgart, 1947). 4. [↵][7]1. J. Smithson , "James Smithson makes his will" (1826); [http://siarchives.si.edu/collections/siris\_sic\_638][8]. [1]: #ref-1 [2]: #ref-3 [3]: http://www.sciencemag.org/content/339/6115/19.full [4]: #ref-4 [5]: #xref-ref-1-1 "View reference 1 in text" [6]: #xref-ref-3-1 "View reference 3 in text" [7]: #xref-ref-4-1 "View reference 4 in text" [8]: http://siarchives.si.edu/collections/siris_sic_638

Journal ArticleDOI
TL;DR: ‘Sibling species’, an old term that has fallen out of use, refers to closely related species that are so similar that it is hard to tell them apart, and how such differences evolve is an active area of research.
Abstract: ‘Sibling species’, an old term that has fallen out of use, refers to closely related species that are so similar that it is hard to tell them apart. The existence of such species raises the obvious question: How do the animals themselves tell one another apart? And indeed, this is an active area of research (Tibbetts & Dale 2007; Uy et al. 2009). Usually, the species differ in one or more traits (i.e. species recognition signals) detectable with the sensory modalities upon which they rely (e.g. raptors use visual signals, frogs use sound and electric fish use different patterns of electric discharge). A more general question concerns how such differences evolve. Over the last decade, it has become increasingly evident that mating signals can evolve under simultaneous selection for two functions (Fleishman et al. 2009): (i) eliciting attention (i.e. detectability); and (ii) species identification (i.e. distinguishing conspecifics from non-conspecifics). Historically, species recognition has attracted a significant amount of research from evolutionary biologists based on the assumption that if hybrids suffer reduced fitness or cannot be produced at all, then natural selection should favour individuals bearing traits that prevent such matings. This idea—confusingly termed either reinforcement or reproductive character displacement—had a rocky time in the evolutionary literature for many years, though now it is widely accepted (Servedio & Noor 2003; Rundle and Nosil, 2005; Pfennig & Pfennig 2009). Near the dawn of the era of molecular ecology, one of the first studies to employ molecular tools to study the evolution of species recognition signals was Webster & Burns’ (1973) study of the evolution of dewlap colour in Anolis lizards. Anoles possess a retractable flap of skin under the throat, termed as dewlap, that is used in courtship, aggressive interactions and even encounters with predators (reviewed in Losos 2009). Anoles can be found in communities of as many as 15 species, and sympatric species never have identical dewlaps, leading to the hypothesis that the dewlap is used in species identification (Rand & Williams 1970). Webster and Burns studied a highly unusual pattern of dewlap distribution in the Hispaniolan bark anole, Anolis brevirostris, along a transect on the western coast of Haiti (Fig. 1). Starting in the south, the lizards have a white dewlap. Then, abruptly the dewlaps become intensely orange; moving northwards, the intensity and size of the orange spot diminishes until it has almost disappeared, whereupon again there is an abrupt transition back to intense orange coloration that characterizes the northernmost populations. Using the tools of the day, Webster and Burns employed starch-gel electrophoresis to examine six geographically varying protein loci. Analysis of these data yielded three important discoveries. First, the populations sorted into three groups: the white-dewlapped forms in the south, the orange-dewlapped forms in the north and a third, intervening form that exhibited clinal variation in the proportion of white vs. orange in the dewlap. Second, at the point of contact between the groups in both the north and the south, adjacent populations did not share alleles at several loci. Third, within the middle, clinally varying group, populations showed little genetic differentiation despite the differences in dewlap colour among populations. Webster and Burns concluded that they were dealing not with a single species, but three—subsequently, the middle populations were described as A. caudalis and the northern ones as A. websteri. More importantly, what had seemingly been an incoherent pattern of geographic variation in dewlap colour variation now had a clear explanation. The apposition of orange vs. white at both ends of A. caudalis’s range is most parsimoniously explained as the result of selection for differences in species recognition signals in sympatry. The fact that A. caudalis maintains the clinal variation in the face of possibly strong ongoing gene flow, as evidenced by the lack of genetic differentiation among populations, was interpreted as powerful evidence for ongoing natural selection favouring dewlap colour differences at the contact zones with the other species. Given this provocative pattern and the great interest in evolutionary reinforcement, it is surprising that this example has not been subject to further investigation as molecular tools have developed over the past four decades. Undoubtedly, the transect’s occurrence in Haiti, a notoriously difficult place for fieldwork, has been a factor. Finally, however, this case study has come under further scrutiny. On a trip in Haiti that was no doubt a story in itself, Lambert et al. revisited Webster and Burns’ transect Correspondence: Jonathan B. Losos, Fax: 617 496 9026; E-mail: jlosos@oeb.harvard.edu