Showing papers by "Jonathan B. Losos published in 2014"
TL;DR: On small islands in Florida, it is found that the lizard Anolis carolinensis moved to higher perches following invasion by Anolis sagrei and, in response, adaptively evolved larger toepads after only 20 generations, illustrating that interspecific interactions between closely related species can drive evolutionary change on observable time scales.
Abstract: In recent years, biologists have increasingly recognized that evolutionary change can occur rapidly when natural selection is strong; thus, real-time studies of evolution can be used to test classic evolutionary hypotheses directly. One such hypothesis is that negative interactions between closely related species can drive phenotypic divergence. Such divergence is thought to be ubiquitous, though well-documented cases are surprisingly rare. On small islands in Florida, we found that the lizard Anolis carolinensis moved to higher perches following invasion by Anolis sagrei and, in response, adaptively evolved larger toepads after only 20 generations. These results illustrate that interspecific interactions between closely related species can drive evolutionary change on observable time scales.
264 citations
TL;DR: As anole colonizations have increased, islands impoverished in native species have gained the most exotic species, the past influence of speciation on island biogeography has been obscured, and the species–area relationship has strengthened while the species-isolation relationship has weakened.
Abstract: For centuries, biogeographers have examined the factors that produce patterns of biodiversity across regions. The study of islands has proved particularly fruitful and has led to the theory that geographic area and isolation influence species colonization, extinction and speciation such that larger islands have more species and isolated islands have fewer species (that is, positive species-area and negative species-isolation relationships). However, experimental tests of this theory have been limited, owing to the difficulty in experimental manipulation of islands at the scales at which speciation and long-distance colonization are relevant. Here we have used the human-aided transport of exotic anole lizards among Caribbean islands as such a test at an appropriate scale. In accord with theory, as anole colonizations have increased, islands impoverished in native species have gained the most exotic species, the past influence of speciation on island biogeography has been obscured, and the species-area relationship has strengthened while the species-isolation relationship has weakened. Moreover, anole biogeography increasingly reflects anthropogenic rather than geographic processes. Unlike the island biogeography of the past that was determined by geographic area and isolation, in the Anthropocene--an epoch proposed for the present time interval--island biogeography is dominated by the economic isolation of human populations.
194 citations
TL;DR: It is found that cold tolerance evolves considerably faster than heat tolerance, a difference that results because behavioural thermoregulation more effectively shields these organisms from selection on upper than lower temperature tolerances.
Abstract: Understanding how quickly physiological traits evolve is a topic of great interest, particularly in the context of how organisms can adapt in response to climate warming. Adjustment to novel thermal habitats may occur either through behavioural adjustments, physiological adaptation or both. Here, we test whether rates of evolution differ among physiological traits in the cybotoids, a clade of tropical Anolis lizards distributed in markedly different thermal environments on the Caribbean island of Hispaniola. We find that cold tolerance evolves considerably faster than heat tolerance, a difference that results because behavioural thermoregulation more effectively shields these organisms from selection on upper than lower temperature tolerances. Specifically, because lizards in very different environments behaviourally thermoregulate during the day to similar body temperatures, divergent selection on body temperature and heat tolerance is precluded, whereas night-time temperatures can only be partially buffered by behaviour, thereby exposing organisms to selection on cold tolerance. We discuss how exposure to selection on physiology influences divergence among tropical organisms and its implications for adaptive evolutionary response to climate warming.
166 citations
TL;DR: Toepad size and claw length and height are tightly correlated with each other and with perch height, suggesting that the adhesive toepad and gripping claw have co-evolved to accommodate different habitats.
59 citations
TL;DR: It is found that male brown anoles dramatically decreased the amplitude of their head-bob displays in the presence of a predatory lizard, resulting in less conspicuous signals, which may be safer for the signaling individuals but also reduce the distance from which potential mates or competitors can detect them.
Abstract: Communication often is a major component of social interactions. Signaling individuals are faced with the challenge of capturing the attention of intended receivers while limiting eavesdropping by potential predators. We conducted an experiment in nature to evaluate the hypothesis that prey species can modulate the physical properties of movement-based displays in response to the presence of predators. We found that male brown anoles dramatically decreased the amplitude of their head-bob displays in the presence of a predatory lizard, resulting in less conspicuous signals. Although less conspicuous signals may be safer for the signaling individuals, they also reduce the distance from which potential mates or competitors can detect them, which might affect the territory size and reproductive success of signaling males.
49 citations
TL;DR: It is found that species in dry environments have fewer, larger scales than species in humid environments, consistent with the hypothesis that scales reduce evaporative water loss through the skin.
Abstract: Lizard scales vary in size, shape and texture among and within species. The overall function of scales in squamates is attributed to protection against abrasion, solar radiation and water loss. We quantified scale number of Anolis lizards across a large sample of species (142 species) and examined whether this variation was related either to structural or to climatic habitat diversity. We found that species in dry environments have fewer, larger scales than species in humid environments. This is consistent with the hypothesis that scales reduce evaporative water loss through the skin. In addition, scale number varied among groups of ecomorphs and was correlated with aspects of the structural microhabitat (i.e. perch height and perch diameter). This was unexpected because ecomorph groups are based on morphological features related to locomotion in different structural microhabitats. Body scales are not likely to play an important role in locomotion in Anolis lizards. The observed variation may relate to other features of the ecomorph niche and more work is needed to understand the putative adaptive basis of these patterns. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 570‐579.
35 citations
TL;DR: The analyses herein reveal that sex-specific regulation of the oestrogen pathway underlies evolution of this exaggerated male phenotype, rather than the androgen or insulin growth factor pathways that have long been considered the primary regulators of male-biased dimorphism among vertebrates.
Abstract: Sexual dimorphisms vary widely among species. This variation must arise through sex-specific evolutionary modifications to developmental processes. Anolis lizards vary extensively in their expression of cranial dimorphism. Compared with other Anolis species, members of the carolinensis clade have evolved relatively high levels of cranial dimorphism; males of this clade have exceptionally long faces relative to conspecific females. Developmentally, this facial length dimorphism arises through an evolutionarily novel, clade-specific strategy. Our analyses herein reveal that sex-specific regulation of the oestrogen pathway underlies evolution of this exaggerated male phenotype, rather than the androgen or insulin growth factor pathways that have long been considered the primary regulators of male-biased dimorphism among vertebrates. Our results suggest greater intricacy in the genetic mechanisms that underlie sexual dimorphisms than previously appreciated.
31 citations
TL;DR: Far from being a survivor from the ‘Age of Dinosaurs’, an old, ill-adapted species that has managed to persist, unchanged, in its antipodean hideaway, the tuatara is a model of evolutionary adaptation, a thoroughly modern species well adapted to its current conditions, or at least to the conditions it experienced up to the arrival of humans, rats, cats and dogs.
Abstract: Oh, tuatara, why do we love you so?In 2003 I had the thrill of a lifetime, getting to stay for five days on Stephens Island, where toots (as I was told they are called by a mischievous Australian) ...
31 citations
TL;DR: The hypothesis of overwater dispersal as the explanation for the occurrence of anole and sole vertebrate described from Mexican amber remains the most robust hypothesis.
14 citations