Ultraviolet and yellow reflectance but not fluorescence is important for visual discrimination of conspecifics by Heliconius erato

Toxic Heliconius butterflies have yellow hindwing bars that – unlike those of their closest relatives – reflect ultraviolet (UV) and long wavelength light, and also fluoresce. The pigment in the yellow scales is 3-hydroxy-DL-kynurenine (3-OHK), which is found in the hair and scales of a variety of animals. In other butterflies like pierids with color schemes characterized by independent sources of variation in UV and human-visible yellow/orange, behavioral experiments have generally implicated the UV component as most relevant to mate choice. This has not been addressed in Heliconius butterflies, where variation exists in analogous color components, but moreover where fluorescence due to 3-OHK could also contribute to yellow wing coloration. In addition, the potential cost due to predator visibility is largely unknown for the analogous well-studied pierid butterfly species. In field studies with butterfly paper models, we show that both UV and 3-OHK yellow act as signals for H. erato when compared with models lacking UV or resembling ancestral Eueides yellow, respectively, but attack rates by birds do not differ significantly between the models. Furthermore, measurement of the quantum yield and reflectance spectra of 3-OHK indicates that fluorescence does not contribute to the visual signal under broad-spectrum illumination. Our results suggest that the use of 3-OHK pigmentation instead of ancestral yellow was driven by sexual selection rather than predation

The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts

We describe the design and data sample from the DEEP2 Galaxy Redshift Survey, the densest and largest precision-redshift survey of galaxies at z ~ 1 completed to date. The survey has conducted a comprehensive census of massive galaxies, their properties, environments, and large-scale structure down to absolute magnitude M_B = -20 at z ~ 1 via ~90 nights of observation on the DEIMOS spectrograph at Keck Observatory. DEEP2 covers an area of 2.8 deg^2 divided into four separate fields, observed to a limiting apparent magnitude of R_AB=24.1. Objects with z < 0.7 are rejected based on BRI photometry in three of the four DEEP2 fields, allowing galaxies with z > 0.7 to be targeted ~2.5 times more efficiently than in a purely magnitude-limited sample. Approximately sixty percent of eligible targets are chosen for spectroscopy, yielding nearly 53,000 spectra and more than 38,000 reliable redshift measurements. Most of the targets which fail to yield secure redshifts are blue objects that lie beyond z ~ 1.45. The DEIMOS 1200-line/mm grating used for the survey delivers high spectral resolution (R~6000), accurate and secure redshifts, and unique internal kinematic information. Extensive ancillary data are available in the DEEP2 fields, particularly in the Extended Groth Strip, which has evolved into one of the richest multiwavelength regions on the sky. DEEP2 surpasses other deep precision-redshift surveys at z ~ 1 in terms of galaxy numbers, redshift accuracy, sample number density, and amount of spectral information. We also provide an overview of the scientific highlights of the DEEP2 survey thus far. This paper is intended as a handbook for users of the DEEP2 Data Release 4, which includes all DEEP2 spectra and redshifts, as well as for the publicly-available DEEP2 DEIMOS data reduction pipelines. [Abridged]Comment: submitted to ApJS; data products available for download at http://deep.berkeley.edu/DR4

The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts

We describe the design and data analysis of the DEEP2 Galaxy Redshift Survey, the densest and largest high-precision redshift survey of galaxies at z approx. 1 completed to date. The survey was designed to conduct a comprehensive census of massive galaxies, their properties, environments, and large-scale structure down to absolute magnitude MB = 20 at z approx. 1 via approx.90 nights of observation on the Keck telescope. The survey covers an area of 2.8 Sq. deg divided into four separate fields observed to a limiting apparent magnitude of R(sub AB) = 24.1. Objects with z approx. 0.7 to be targeted approx. 2.5 times more efficiently than in a purely magnitude-limited sample. Approximately 60% of eligible targets are chosen for spectroscopy, yielding nearly 53,000 spectra and more than 38,000 reliable redshift measurements. Most of the targets that fail to yield secure redshifts are blue objects that lie beyond z approx. 1.45, where the [O ii] 3727 Ang. doublet lies in the infrared. The DEIMOS 1200 line mm(exp 1) grating used for the survey delivers high spectral resolution (R approx. 6000), accurate and secure redshifts, and unique internal kinematic information. Extensive ancillary data are available in the DEEP2 fields, particularly in the Extended Groth Strip, which has evolved into one of the richest multiwavelength regions on the sky. This paper is intended as a handbook for users of the DEEP2 Data Release 4, which includes all DEEP2 spectra and redshifts, as well as for the DEEP2 DEIMOS data reduction pipelines. Extensive details are provided on object selection, mask design, biases in target selection and redshift measurements, the spec2d two-dimensional data-reduction pipeline, the spec1d automated redshift pipeline, and the zspec visual redshift verification process, along with examples of instrumental signatures or other artifacts that in some cases remain after data reduction. Redshift errors and catastrophic failure rates are assessed through more than 2000 objects with duplicate observations. Sky subtraction is essentially photon-limited even under bright OH sky lines; we describe the strategies that permitted this, based on high image stability, accurate wavelength solutions, and powerful B-spline modeling methods. We also investigate the impact of targets that appear to be single objects in ground-based targeting imaging but prove to be composite in Hubble Space Telescope data; they constitute several percent of targets at z approx. 1, approaching approx. 5%-10% at z > 1.5. Summary data are given that demonstrate the superiority of DEEP2 over other deep high-precision redshift surveys at z approx. 1 in terms of redshift accuracy, sample number density, and amount of spectral information. We also provide an overview of the scientific highlights of the DEEP2 survey thus far

The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts

We describe the design and data analysis of the DEEP2 Galaxy Redshift Survey, the densest and largest high-precision redshift survey of galaxies at z ~ 1 completed to date. The survey was designed to conduct a comprehensive census of massive galaxies, their properties, environments, and large-scale structure down to absolute magnitude M_B = −20 at z ~ 1 via ~90 nights of observation on the Keck telescope. The survey covers an area of 2.8 deg^2 divided into four separate fields observed to a limiting apparent magnitude of R_(AB) = 24.1. Objects with z ≾0.7 are readily identifiable using BRI photometry and rejected in three of the four DEEP2 fields, allowing galaxies with z > 0.7 to be targeted ~2.5 times more efficiently than in a purely magnitude-limited sample. Approximately 60% of eligible targets are chosen for spectroscopy, yielding nearly 53,000 spectra and more than 38,000 reliable redshift measurements. Most of the targets that fail to yield secure redshifts are blue objects that lie beyond z ~ 1.45, where the [O ii] 3727 Å doublet lies in the infrared. The DEIMOS 1200 line mm^(−1) grating used for the survey delivers high spectral resolution (R ~ 6000), accurate and secure redshifts, and unique internal kinematic information. Extensive ancillary data are available in the DEEP2 fields, particularly in the Extended Groth Strip, which has evolved into one of the richest multiwavelength regions on the sky. This paper is intended as a handbook for users of the DEEP2 Data Release 4, which includes all DEEP2 spectra and redshifts, as well as for the DEEP2 DEIMOS data reduction pipelines. Extensive details are provided on object selection, mask design, biases in target selection and redshift measurements, the spec2d two-dimensional data-reduction pipeline, the spec1d automated redshift pipeline, and the zspec visual redshift verification process, along with examples of instrumental signatures or other artifacts that in some cases remain after data reduction. Redshift errors and catastrophic failure rates are assessed through more than 2000 objects with duplicate observations. Sky subtraction is essentially photon-limited even under bright OH sky lines; we describe the strategies that permitted this, based on high image stability, accurate wavelength solutions, and powerful B-spline modeling methods. We also investigate the impact of targets that appear to be single objects in ground-based targeting imaging but prove to be composite in Hubble Space Telescope data; they constitute several percent of targets at z ~ 1, approaching ~5%–10% at z > 1.5. Summary data are given that demonstrate the superiority of DEEP2 over other deep high-precision redshift surveys at z ~ 1 in terms of redshift accuracy, sample number density, and amount of spectral information. We also provide an overview of the scientific highlights of the DEEP2 survey thus far

True UV color vision in a female butterfly with two UV opsins

In true color vision, animals discriminate between light wavelengths, regardless of intensity, using at least two photoreceptors with different spectral sensitivity peaks. Heliconius butterflies have duplicate UV opsin genes, which encode ultraviolet and violet photoreceptors, respectively. In Heliconius erato, only females express the ultraviolet photoreceptor, suggesting females (but not males) can discriminate between UV wavelengths. We tested the ability of H. erato, and two species lacking the violet receptor, Heliconius melpomene and Eueides isabella, to discriminate between 380 and 390 nm, and between 400 and 436 nm, after being trained to associate each stimulus with a sugar reward. We found that only H. erato females have color vision in the UV range. Across species, both sexes show color vision in the blue range. Models of H. erato color vision suggest that females have an advantage over males in discriminating the inner UV-yellow corollas of Psiguria flowers from their outer orange petals. Moreover, previous models ( McCulloch et al., 2017) suggested that H. erato males have an advantage over females in discriminating Heliconius 3-hydroxykynurenine (3-OHK) yellow wing coloration from non-3-OHK yellow wing coloration found in other heliconiines. These results provide some of the first behavioral evidence for female H. erato UV color discrimination in the context of foraging, lending support to the hypothesis ( Briscoe et al., 2010) that the duplicated UV opsin genes function together in UV color vision. Taken together, the sexually dimorphic visual system of H. erato appears to have been shaped by both sexual selection and sex-specific natural selection

True UV color vision in a female butterfly with two UV opsins

In true color vision, animals discriminate between light wavelengths, regardless of intensity, using at least two photoreceptors with different spectral sensitivity peaks. Heliconius butterflies have duplicate UV opsin genes, which encode ultraviolet and violet photoreceptors, respectively. In Heliconius erato, only females express the ultraviolet photoreceptor, suggesting females (but not males) can discriminate between UV wavelengths. We tested the ability of H. erato, and two species lacking the violet receptor, Heliconius melpomene and Eueides isabella, to discriminate between 380 and 390 nm, and between 400 and 436 nm, after being trained to associate each stimulus with a sugar reward. We found that only H. erato females have color vision in the UV range. Across species, both sexes show color vision in the blue range. Models of H. erato color vision suggest that females have an advantage over males in discriminating the inner UV-yellow corollas of Psiguria flowers from their outer orange petals. Moreover, previous models ( McCulloch et al., 2017) suggested that H. erato males have an advantage over females in discriminating Heliconius 3-hydroxykynurenine (3-OHK) yellow wing coloration from non-3-OHK yellow wing coloration found in other heliconiines. These results provide some of the first behavioral evidence for female H. erato UV color discrimination in the context of foraging, lending support to the hypothesis ( Briscoe et al., 2010) that the duplicated UV opsin genes function together in UV color vision. Taken together, the sexually dimorphic visual system of H. erato appears to have been shaped by both sexual selection and sex-specific natural selection

Data from: Warning signals are seductive: relative contributions of color and pattern to predator avoidance and mate attraction in Heliconius butterflies

Visual signaling in animals can serve many uses, including predator deterrence and mate attraction. In many cases, signals used to advertise unprofitability to predators are also used for intraspecific communication. Although aposematism and mate choice are significant forces driving the evolution of many animal phenotypes, the interplay between relevant visual signals remains little explored. Here, we address this question in the aposematic passion-vine butterfly Heliconius erato by using color- and pattern-manipulated models to test the contributions of different visual features to both mate choice and warning coloration. We found that the relative effectiveness of a model at escaping predation was correlated with its effectiveness at inducing mating behavior, and in both cases wing color was more predictive of presumptive fitness benefits than wing pattern. Overall, however, a combination of the natural (local) color and pattern was most successful for both predator deterrence and mate attraction. By exploring the relative contributions of color versus pattern composition in predation and mate preference studies, we have shown how both natural and sexual selection may work in parallel to drive the evolution of specific animal color patterns

Warning signals are seductive: Relative contributions of color and pattern to predator avoidance and mate attraction in Heliconius butterflies

Visual signaling in animals can serve many uses, including predator deterrence and mate attraction. In many cases, signals used to advertise unprofitability to predators are also used for intraspecific communication. Although aposematism and mate choice are significant forces driving the evolution of many animal phenotypes, the interplay between relevant visual signals remains little explored. Here, we address this question in the aposematic passion-vine butterfly Heliconius erato by using color- and pattern-manipulated models to test the contributions of different visual features to both mate choice and warning coloration. We found that the relative effectiveness of a model at escaping predation was correlated with its effectiveness at inducing mating behavior, and in both cases wing color was more predictive of presumptive fitness benefits than wing pattern. Overall, however, a combination of the natural (local) color and pattern was most successful for both predator deterrence and mate attraction. By exploring the relative contributions of color versus pattern composition in predation and mate preference studies, we have shown how both natural and sexual selection may work in parallel to drive the evolution of specific animal color patterns

Data from: Complex dynamics underlie the evolution of imperfect wing pattern convergence in butterflies

Adaptive radiation is characterized by rapid diversification that is strongly associated with ecological specialization. However, understanding the evolutionary mechanisms fueling adaptive diversification requires a detailed knowledge of how natural selection acts at multiple life-history stages. Butterflies within the genus Adelpha represent one of the largest and most diverse butterfly lineages in the Neotropics. Although Adelpha species feed on an extraordinary diversity of larval hosts, convergent evolution is widespread in this group suggesting that selection for mimicry may contribute to adaptive divergence among species. To investigate this hypothesis, we conducted predation studies in Costa Rica using artificial butterfly facsimiles. Specifically, we predicted that non-toxic, palatable Adelpha species that do not feed on host plants in the family Rubiaceae would benefit from sharing a locally convergent wing pattern with the presumably toxic Rubiaceae-feeding species via reduced predation. Contrary to expectations, we found that the presumed mimic was attacked significantly more than its locally convergent model, at a frequency paralleling attack rates on both novel and palatable prey. Although these data reveal the first evidence for protection from avian predators by the supposed toxic, Rubiaceae-feeding Adelpha species, we conclude that imprecise mimetic patterns have high costs for Batesian mimics in the tropics