Extreme Heterogeneity in Sex Chromosome Differentiation and Dosage Compensation in Livebearers

Once recombination is halted between the X and Y chromosomes, sex chromosomes begin to differentiate and transition to heteromorphism. While there is a remarkable variation across clades in the degree of sex chromosome divergence, far less is known about the variation in sex chromosome differentiation within clades. Here, we combined whole-genome and transcriptome sequencing data to characterize the structure and conservation of sex chromosome systems across Poeciliidae, the livebearing clade that includes guppies. We found that the Poecilia reticulata XY system is much older than previously thought, being shared not only with its sister species, Poecilia wingei, but also with Poecilia picta, which diverged roughly 20 million years ago. Despite the shared ancestry, we uncovered an extreme heterogeneity across these species in the proportion of the sex chromosome with suppressed recombination, and the degree of Y chromosome decay. The sex chromosomes in P. reticulata and P. wingei are largely homomorphic, with recombination in the former persisting over a substantial fraction. However, the sex chromosomes in P. picta are completely nonrecombining and strikingly heteromorphic. Remarkably, the profound degradation of the ancestral Y chromosome in P. picta is counterbalanced by the evolution of functional chromosome-wide dosage compensation in this species, which has not been previously observed in teleost fish. Our results offer important insight into the initial stages of sex chromosome evolution and dosage compensation

Opsin Gene Expression As Proportion of Total Opsin Expression

This file is a csv that has the level of expression of each of the 9 opsins measured as a proportion of total opsin expression. These numbers are for each individual along with information on the sex, standard length (SL), population (AHP- Aripo High Predation, ALP- Aripo Low Predation, MHP- Marianne High Predation, MLP- Marianne Low Predation), Watershed, Predation regime, Day of collection and Time of day collected (1- 07:30, 2- 10:30, 3- 13:30, 4- 16:30)

Stats in R

This file has all stats run on this project and utilizes the data sets also available in Dryad

Light Measures

This is a csv file of the measures of lambda p50 for each population measured on each of the 3 days

Trinidad Environmental Parameters

This is a csv file that has the raw environmental parameters measured for each of the populations on each of the 3 days. These include: Temperature (C), Conductivity, Dissolved Oxygen (DO), pH, Total Dissolved Oxygen (TDS), Salinity, and Resistivit

Data from: Beauty in the eyes of the beholders: color vision is tuned to mate preference in the Trinidadian guppy (Poecilia reticulata)

A broad range of animals use visual signals to assess potential mates, and the theory of sensory exploitation suggests variation in visual systems drives mate preference variation due to sensory bias. Trinidadian guppies (Poecilia reticulata), a classic system for studies of the evolution of female mate choice, provide a unique opportunity to test this theory by looking for co-variation in visual tuning, light environment, and mate preferences. Female preference co-evolves with male coloration, such that guppy females from ‘low predation’ environments have stronger preferences for males with more orange/red coloration than do females from ‘high predation’ environments. Here we show that color vision also varies across populations, with ‘low’ predation guppies investing more of their color vision to detect red/orange coloration. In independently colonized watersheds, guppies expressed higher levels of both LWS-1 and LWS-3 (the most abundant LWS opsins) in ‘low predation’ populations than ‘high predation’ populations at a time that corresponds to differences in cone cell abundance. We also observed that the frequency of a coding polymorphism differed between high and low predation populations. Together this shows that the variation underlying preference could be explained by simple changes in expression and coding of opsins, providing important candidate genes to investigate the genetic basis of variation in this model system

Gene Expression Relative to Average Housekeeping

This file is a cvs that has the level of expression of each of the 9 opsins, 1 rhodopsin and 3 housekeeping genes measured relative to the average of the 3 housekeeping genes (Bactin, COI, and MyosinHC). These numbers are for each individual along with information on the sex, standard length (SL), population (AHP- Aripo High Predation, ALP- Aripo Low Predation, MHP- Marianne High Predation, MLP- Marianne Low Predation), Watershed, Predation regime, Day of collection and Time of day collected (1- 07:30, 2- 10:30, 3- 13:30, 4- 16:30)

Developmental plasticity in vision and behavior may help guppies overcome increased turbidity.

Increasing turbidity in streams and rivers near human activity is cause for environmental concern, as the ability of aquatic organisms to use visual information declines. To investigate how some organisms might be able to developmentally compensate for increasing turbidity, we reared guppies (Poecilia reticulata) in either clear or turbid water. We assessed the effects of developmental treatments on adult behavior and aspects of the visual system by testing fish from both developmental treatments in turbid and clear water. We found a strong interactive effect of rearing and assay conditions: fish reared in clear water tended to decrease activity in turbid water, whereas fish reared in turbid water tended to increase activity in turbid water. Guppies from all treatments decreased activity when exposed to a predator. To measure plasticity in the visual system, we quantified treatment differences in opsin gene expression of individuals. We detected a shift from mid-wave-sensitive opsins to long wave-sensitive opsins for guppies reared in turbid water. Since long-wavelength sensitivity is important in motion detection, this shift likely allows guppies to salvage motion-detecting abilities when visual information is obscured in turbid water. Our results demonstrate the importance of developmental plasticity in responses of organisms to rapidly changing environments

Developmental plasticity in vision and behavior may help guppies overcome increased turbidity.

Increasing turbidity in streams and rivers near human activity is cause for environmental concern, as the ability of aquatic organisms to use visual information declines. To investigate how some organisms might be able to developmentally compensate for increasing turbidity, we reared guppies (Poecilia reticulata) in either clear or turbid water. We assessed the effects of developmental treatments on adult behavior and aspects of the visual system by testing fish from both developmental treatments in turbid and clear water. We found a strong interactive effect of rearing and assay conditions: fish reared in clear water tended to decrease activity in turbid water, whereas fish reared in turbid water tended to increase activity in turbid water. Guppies from all treatments decreased activity when exposed to a predator. To measure plasticity in the visual system, we quantified treatment differences in opsin gene expression of individuals. We detected a shift from mid-wave-sensitive opsins to long wave-sensitive opsins for guppies reared in turbid water. Since long-wavelength sensitivity is important in motion detection, this shift likely allows guppies to salvage motion-detecting abilities when visual information is obscured in turbid water. Our results demonstrate the importance of developmental plasticity in responses of organisms to rapidly changing environments