Changes in selection pressure can facilitate hybridization during biological invasion in a Cuban lizard

Hybridization is among the evolutionary mechanisms most frequently hypothesized to drive the success of invasive species, in part because hybrids are common in invasive populations. One explanation for this pattern is that biological invasions coincide with a change in selection pressures that limit hybridization in the native range. To investigate this possibility, we studied the introduction of the brown anole (Anolis sagrei) in the southeastern United States. We find that native populations are highly genetically structured. In contrast, all invasive populations show evidence of hybridization among native-range lineages. Temporal sampling in the invasive range spanning 15 y showed that invasive genetic structure has stabilized, indicating that large-scale contemporary gene flow is limited among invasive populations and that hybrid ancestry is maintained. Additionally, our results are consistent with hybrid persistence in invasive populations resulting from changes in natural selection that occurred during invasion. Specifically, we identify a large-effect X chromosome locus associated with variation in limb length, a well-known adaptive trait in anoles, and show that this locus is often under selection in the native range, but rarely so in the invasive range. Moreover, we find that the effect size of alleles at this locus on limb length is much reduced in hybrids among divergent lineages, consistent with epistatic interactions. Thus, in the native range, epistasis manifested in hybrids can strengthen extrinsic postmating isolation. Together, our findings show how a change in natural selection can contribute to an increase in hybridization in invasive populations.

Download Full-text

The Simulated Evolution of Biochemical Guilds: Reconciling Gaia Theory and Natural Selection

Artificial Life ◽

10.1162/106454699568791 ◽

1999 ◽

Vol 5 (4) ◽

pp. 291-318 ◽

Cited By ~ 34

Author(s):

Keith Downing ◽

Peter Zvirinsky

Keyword(s):

Natural Selection ◽

Artificial Life ◽

Large Scale ◽

Resource Competition ◽

Nutrient Recycling ◽

Nutrient Ratios ◽

Evolutionary Mechanisms ◽

Life Model ◽

Gaia Theory ◽

Implicit Coordination

Gaia theory, which states that organisms both affect and regulate their environment, poses an interesting problem to Neo-Darwinian evolutionary biologists and provides an exciting set of phenomena for artificial-life investigation. The key challenge is to explain the emergence of biotic communities that are capable, via their implicit coordination, of regulating large-scale biogeochemical factors such as the temperature and chemical composition of the biosphere, but to assume no evolutionary mechanisms beyond contemporary natural selection. Along with providing an introduction to Gaia theory, this article presents simulations of Gaian emergence based on an artificial-life model involving genetic algorithms and guilds of simple metabolizing agents. In these simulations, resource competition leads to guild diversity; the ensemble of guilds then manifests life-sustaining nutrient recycling and exerts distributed control over environmental nutrient ratios. These results illustrate that standard individual-based natural selection is sufficient to explain Gaian self-organization, and they help clarify the relationships between two key metrics of Gaian activity: recycling and regulation.

Download Full-text

Inconclusive evidence of sexual reproduction of invasive Halophila stipulacea: a new field guide to encourage investigation of flower and fruit production throughout its invasive range

Botanica Marina ◽

10.1515/bot-2020-0046 ◽

2020 ◽

Vol 63 (6) ◽

pp. 537-540

Author(s):

Fee O.H. Smulders ◽

Kelcie L. Chiquillo ◽

Demian A. Willette ◽

Paul H. Barber ◽

Marjolijn J.A. Christianen

Keyword(s):

Sexual Reproduction ◽

Clonal Growth ◽

Large Scale ◽

Fruit Production ◽

Morphological Evidence ◽

Invasive Range ◽

Reproductive Structures ◽

Halophila Stipulacea ◽

The Caribbean ◽

Low Rate

AbstractThe dioecious seagrass species Halophila stipulacea reproduces mainly through fast clonal growth, underlying its invasive behavior. Here, we provide morphological evidence to show that the first findings of fruits in the Caribbean were misidentified. Consequently, H. stipulacea reproduction is likely still only asexual in the Caribbean. Therefore, we introduce an identification key of H. stipulacea reproductive structures to encourage careful identification and quantification throughout its invasive range. Until large-scale seed production in invaded habitats is reported, the apparent low rate of sexual reproduction needs to be considered in current studies investigating the invasion capacity of this species.

Download Full-text

Genome size correlates with reproductive fitness in seed beetles

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.1421 ◽

2015 ◽

Vol 282 (1815) ◽

pp. 20151421 ◽

Cited By ~ 14

Author(s):

Göran Arnqvist ◽

Ahmed Sayadi ◽

Elina Immonen ◽

Cosima Hotzy ◽

Daniel Rankin ◽

...

Keyword(s):

Life History ◽

Natural Selection ◽

Genome Size ◽

Evolutionary Biology ◽

Large Scale ◽

Life History Traits ◽

Single Species ◽

Reproductive Fitness ◽

Correlated Evolution ◽

Seed Beetles

The ultimate cause of genome size (GS) evolution in eukaryotes remains a major and unresolved puzzle in evolutionary biology. Large-scale comparative studies have failed to find consistent correlations between GS and organismal properties, resulting in the ‘ C -value paradox’. Current hypotheses for the evolution of GS are based either on the balance between mutational events and drift or on natural selection acting upon standing genetic variation in GS. It is, however, currently very difficult to evaluate the role of selection because within-species studies that relate variation in life-history traits to variation in GS are very rare. Here, we report phylogenetic comparative analyses of GS evolution in seed beetles at two distinct taxonomic scales, which combines replicated estimation of GS with experimental assays of life-history traits and reproductive fitness. GS showed rapid and bidirectional evolution across species, but did not show correlated evolution with any of several indices of the relative importance of genetic drift. Within a single species, GS varied by 4–5% across populations and showed positive correlated evolution with independent estimates of male and female reproductive fitness. Collectively, the phylogenetic pattern of GS diversification across and within species in conjunction with the pattern of correlated evolution between GS and fitness provide novel support for the tenet that natural selection plays a key role in shaping GS evolution.

Download Full-text

K2 space photometry reveals rotational modulation and stellar pulsations in chemically peculiar A and B stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833037 ◽

2018 ◽

Vol 616 ◽

pp. A77 ◽

Cited By ~ 17

Author(s):

D. M. Bowman ◽

B. Buysschaert ◽

C. Neiner ◽

P. I. Pápics ◽

M. E. Oksala ◽

...

Keyword(s):

Magnetic Field ◽

Large Scale ◽

Intrinsic Variability ◽

B Stars ◽

Pulsating Stars ◽

Chemically Peculiar ◽

Large Scale Magnetic Field ◽

Peculiar Stars ◽

Show Evidence ◽

Chemically Peculiar Stars

Context. The physics of magnetic hot stars and how a large-scale magnetic field affects their interior properties is largely unknown. Few studies have combined high-quality observations and modelling of magnetic pulsating stars, known as magneto-asteroseismology, primarily because of the dearth of detected pulsations in stars with a confirmed and well-characterised large-scale magnetic field. Aims. We aim to characterise observational signatures of rotation and pulsation in chemically peculiar candidate magnetic stars using photometry from the K2 space mission. Thus, we identify the best candidate targets for ground-based, optical spectropolarimetric follow-up observations to confirm the presence of a large-scale magnetic field. Methods. We employed customised reduction and detrending tools to process the K2 photometry into optimised light curves for a variability analysis. We searched for the periodic photometric signatures of rotational modulation caused by surface abundance inhomogeneities in 56 chemically peculiar A and B stars. Furthermore, we searched for intrinsic variability caused by pulsations (coherent or otherwise) in the amplitude spectra of these stars. Results. The rotation periods of 38 chemically peculiar stars are determined, 16 of which are the first determination of the rotation period in the literature. We confirm the discovery of high-overtone roAp pulsation modes in HD 177765 and find an additional 3 Ap and Bp stars that show evidence of high-overtone pressure modes found in roAp stars in the form of possible Nyquist alias frequencies in their amplitude spectra. Furthermore, we find 6 chemically peculiar stars that show evidence of intrinsic variability caused by gravity or pressure pulsation modes. Conclusions. The discovery of pulsations in a non-negligible fraction of chemically peculiar stars make these stars high-priority targets for spectropolarimetric campaigns to confirm the presence of their expected large-scale magnetic field. The ultimate goal is to perform magneto-asteroseismology and probe the interior physics of magnetic pulsating stars.

Download Full-text

May the (selective) force be with you: Spatial sorting and natural selection exert opposing forces on limb length in an invasive amphibian

Journal of Evolutionary Biology ◽

10.1111/jeb.13504 ◽

2019 ◽

Vol 32 (9) ◽

pp. 994-1001 ◽

Cited By ~ 1

Author(s):

Gregory S. Clarke ◽

Richard Shine ◽

Benjamin L. Phillips

Keyword(s):

Natural Selection ◽

Limb Length ◽

Selective Force ◽

Spatial Sorting

Download Full-text

Variability in the Power Spectrum of Solar Five-Minute Oscillations

International Astronomical Union Colloquium ◽

10.1017/s0252921100095749 ◽

1983 ◽

Vol 66 ◽

pp. 411-425

Author(s):

Frank Hill ◽

Juri Toomre ◽

Laurence J. November

Keyword(s):

Large Scale ◽

Solar Rotation ◽

Temporal Frequency ◽

Power Spectra ◽

Giant Cells ◽

Spectral Lines ◽

Data Sets ◽

Data Set ◽

Temporal Sampling ◽

Velocity Changes

AbstractTwo-dimensional power spectra of solar five-minute oscillations display prominent ridge structures in (k, ω) space, where k is the horizontal wavenumber and ω is the temporal frequency. The positions of these ridges in k and ω can be used to probe temperature and velocity structures in the subphotosphere. We have been carrying out a continuing program of observations of five-minute oscillations with the diode array instrument on the vacuum tower telescope at Sacramento Peak Observatory (SPO). We have sought to establish whether power spectra taken on separate days show shifts in ridge locations; these may arise from different velocity and temperature patterns having been brought into our sampling region by solar rotation. Power spectra have been obtained for six days of observations of Doppler velocities using the Mg I λ5173 and Fe I λ5434 spectral lines. Each data set covers 8 to 11 hr in time and samples a region 256″ × 1024″ in spatial extent, with a spatial resolution of 2″ and temporal sampling of 65 s. We have detected shifts in ridge locations between certain data sets which are statistically significant. The character of these displacements when analyzed in terms of eastward and westward propagating waves implies that changes have occurred in both temperature and horizontal velocity fields underlying our observing window. We estimate the magnitude of the velocity changes to be on the order of 100 m s -1; we may be detecting the effects of large-scale convection akin to giant cells.

Download Full-text

Impact of Model Resolution on Tropical Cyclone Simulation Using the HighResMIP–PRIMAVERA Multimodel Ensemble

Journal of Climate ◽

10.1175/jcli-d-19-0639.1 ◽

2020 ◽

Vol 33 (7) ◽

pp. 2557-2583 ◽

Cited By ~ 15

Author(s):

Malcolm John Roberts ◽

Joanne Camp ◽

Jon Seddon ◽

Pier Luigi Vidale ◽

Kevin Hodges ◽

...

Keyword(s):

Tropical Cyclone ◽

Large Scale ◽

Northwestern Pacific ◽

Model Resolution ◽

Enhanced Resolution ◽

Systematic Improvement ◽

Ensemble Mean ◽

Show Evidence ◽

Storm Frequency ◽

The Impact

AbstractA multimodel, multiresolution set of simulations over the period 1950–2014 using a common forcing protocol from CMIP6 HighResMIP have been completed by six modeling groups. Analysis of tropical cyclone performance using two different tracking algorithms suggests that enhanced resolution toward 25 km typically leads to more frequent and stronger tropical cyclones, together with improvements in spatial distribution and storm structure. Both of these factors reduce typical GCM biases seen at lower resolution. Using single ensemble members of each model, there is little evidence of systematic improvement in interannual variability in either storm frequency or accumulated cyclone energy as compared with observations when resolution is increased. Changes in the relationships between large-scale drivers of climate variability and tropical cyclone variability in the Atlantic Ocean are also not robust to model resolution. However, using a larger ensemble of simulations (of up to 14 members) with one model at different resolutions does show evidence of increased skill at higher resolution. The ensemble mean correlation of Atlantic interannual tropical cyclone variability increases from ~0.5 to ~0.65 when resolution increases from 250 to 100 km. In the northwestern Pacific Ocean the skill keeps increasing with 50-km resolution to 0.7. These calculations also suggest that more than six members are required to adequately distinguish the impact of resolution within the forced signal from the weather noise.

Download Full-text

Cometary evolution and cryovolcanism 1This article is part of a Special issue that honours the work of Dr. Donald M. Hunten FRSC who passed away in December 2010 after a very illustrious career.

Canadian Journal of Physics ◽

10.1139/p11-123 ◽

2012 ◽

Vol 90 (8) ◽

pp. 807-815 ◽

Cited By ~ 3

Author(s):

Michael J.S. Belton

Keyword(s):

Spatial Distribution ◽

Production Rate ◽

Large Scale ◽

Special Issue ◽

Apparent Absence ◽

Cometary Nuclei ◽

Evolutionary Hypothesis ◽

Wide Range ◽

Show Evidence ◽

Cometary Activity

Recent space observations of cometary nuclei show evidence of internal (cryovolcanic) activity while retaining aspects of their primitive origins. Using discoveries made during the two most recent cometary encounters: EPOXI at 103P/Hartley 2 and Stardust-NExT at 9P/Tempel 1, we test a hypothesis for their physical evolution, which, if true, could provide a unified basis for understanding the relative ages of their surfaces and the causes of a wide range of cometary activity. We show: (i) that the categorization of 103P/Hartley 2 as hyperactive is not a reflection of the extent of activity over the surface of the nucleus for which we find a normal H2O production rate; (ii) that the heterogeneous spatial distribution of CO2 and H2O in the inner comae of 9P/Tempel 1 and 103P/Hartley 2 is best explained by processes associated with cometary activity rather than the presence of primitive compositional heterogeneities in the nucleus; and (iii) that most of the quasi-circular depressions seen on the surface of 9P/Tempel are the result of outburst activity. The apparent absence of circular depressions and large scale layering on 103P/Hartley 2 present a challenge to the evolutionary hypothesis although the small size of its nucleus may ultimately provide an explanation.

Download Full-text

Repeated modification of early limb morphogenesis programmes underlies the convergence of relative limb length in Anolis lizards

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2011.0840 ◽

2011 ◽

Vol 279 (1729) ◽

pp. 739-748 ◽

Cited By ~ 41

Author(s):

Thomas J. Sanger ◽

Liam J. Revell ◽

Jeremy J. Gibson-Brown ◽

Jonathan B. Losos

Keyword(s):

Natural Selection ◽

Developmental Trajectories ◽

Limb Length ◽

Long Bone ◽

Length Variation ◽

Developmental Processes ◽

Independent Evolution ◽

Limb Morphogenesis ◽

Habitat Specialists ◽

Phenotypic Convergence

The independent evolution of similar morphologies has long been a subject of considerable interest to biologists. Does phenotypic convergence reflect the primacy of natural selection, or does development set the course of evolution by channelling variation in certain directions? Here, we examine the ontogenetic origins of relative limb length variation among Anolis lizard habitat specialists to address whether convergent phenotypes have arisen through convergent developmental trajectories. Despite the numerous developmental processes that could potentially contribute to variation in adult limb length, our analyses reveal that, in Anolis lizards, such variation is repeatedly the result of changes occurring very early in development, prior to formation of the cartilaginous long bone anlagen.

Download Full-text