Piebaldism and chromatophore development in reptiles are linked to the tfec gene

Reptiles display great diversity in color and pattern, yet much of what we know about vertebrate coloration comes from classic model species such as the mouse and zebrafish.1,2,3,4 Captive-bred ball pythons (Python regius) exhibit a remarkable degree of color and pattern variation. Despite the wide range of Mendelian color phenotypes available in the pet trade, ball pythons remain an overlooked species in pigmentation research. Here, we investigate the genetic basis of the recessive piebald phenotype, a pattern defect characterized by patches of unpigmented skin (leucoderma). We performed whole-genome sequencing and used a case-control approach to discover a nonsense mutation in the gene encoding the transcription factor tfec, implicating this gene in the leucodermic patches in ball pythons. We functionally validated tfec in a lizard model (Anolis sagrei) using the gene editing CRISPR/Cas9 system and TEM imaging of skin. Our findings show that reading frame mutations in tfec affect coloration and lead to a loss of iridophores in Anolis, indicating that tfec is required for chromatophore development. This study highlights the value of captive-bred ball pythons as a model species for accelerating discoveries on the genetic basis of vertebrate coloration.

Unraveling the mystery of the glacier bear: Genetic population structure of black bears (Ursus americanus) within the range of a rare pelage type

Glacier bears are a rare grey color morph of American black bear (Ursus americanus) found only in northern Southeast Alaska and a small portion of western Canada. We examine contemporary genetic population structure of black bears within the geographic extent of glacier bears and explore how this structure relates to pelage color and landscape features of a recently glaciated and highly fragmented landscape. We used existing radiocollar data to quantify black bear home-range size within the geographic range of glacier bears. The mean home-range size of female black bears in the study area was 13 km2 (n = 11), whereas the home range of a single male was 86.9 km2. We genotyped 284 bears using 21 microsatellites extracted from noninvasively collected hair as well as tissue samples from harvested bears. We found ten populations of black bears in the study area, including several new populations not previously identified, divided largely by geographic features such as glaciers and marine fjords. Glacier bears were assigned to four populations found on the north and east side of Lynn Canal and the north and west side of Glacier Bay with a curious absence in the nonglaciated peninsula between. Lack of genetic relatedness and geographic continuity between black bear populations containing glacier bears suggest a possible unsampled population or an association with ice fields. Further investigation is needed to determine the genetic basis and the adaptive and evolutionary significance of the glacier bear color morph to help focus black bear conservation management to maximize and preserve genetic diversity.

Phenotypic divergence among threespine stickleback that differ in nuptial coloration

By studying systems in their earliest stages of differentiation, we can learn about the evolutionary forces acting within and among populations and how those forces could contribute to reproductive isolation. Such an understanding would help us to better discern and predict how selection leads to the maintenance of multiple morphs within a species, rather than speciation. The postglacial adaptive radiation of the threespine stickleback (Gasterosteus aculeatus) is one of the best-studied cases of evolutionary diversification and rapid, repeated speciation. Following deglaciation, marine stickleback have continually invaded freshwater habitats across the northern hemisphere and established resident populations that diverged innumerable times from their oceanic ancestors. Independent freshwater colonization events have yielded broadly parallel patterns of morphological differences in freshwater and marine stickleback. However, there is also much phenotypic diversity within and among freshwater populations. We studied a lesser-known freshwater "species pair" found in southwest Washington, where male stickleback in numerous locations have lost the ancestral red sexual signal and instead develop black nuptial coloration. We measured phenotypic variation in a suite of traits across sites where red and black stickleback do not overlap in distribution and at one site where they historically co-occurred. We found substantial phenotypic divergence between red and black morphs in noncolor traits including shape and lateral plating, and additionally find evidence that supports the hypothesis of sensory drive as the mechanism responsible for the evolutionary switch in color from red to black. A newly described third "mixed" morph in Connor Creek, Washington, differs in head shape and size from the red and black morphs, and we suggest that their characteristics are most consistent with hybridization between anadromous and freshwater stickleback. These results lay the foundation for future investigation of the underlying genetic basis of this phenotypic divergence as well as the evolutionary processes that may drive, maintain, or limit divergence among morphs.

Evaluating within-population variability in behavior and demography for the adaptive potential of a dispersal-limited species to climate change

Multiple pathways exist for species to respond to changing climates. However, responses of dispersal‐limited species will be more strongly tied to ability to adapt within existing populations as rates of environmental change will likely exceed movement rates. Here, we assess adaptive capacity in Plethodon cinereus, a dispersal‐limited woodland salamander. We quantify plasticity in behavior and variation in demography to observed variation in environmental variables over a 5‐year period. We found strong evidence that temperature and rainfall influence P. cinereus surface presence, indicating changes in climate are likely to affect seasonal activity patterns. We also found that warmer summer temperatures reduced individual growth rates into the autumn, which is likely to have negative demographic consequences. Reduced growth rates may delay reproductive maturity and lead to reductions in size‐specific fecundity, potentially reducing population‐level persistence. To better understand within‐population variability in responses, we examined differences between two common color morphs. Previous evidence suggests that the color polymorphism may be linked to physiological differences in heat and moisture tolerance. We found only moderate support for morph‐specific differences for the relationship between individual growth and temperature. Measuring environmental sensitivity to climatic variability is the first step in predicting species' responses to climate change. Our results suggest phenological shifts and changes in growth rates are likely responses under scenarios where further warming occurs, and we discuss possible adaptive strategies for resulting selective pressures.

How Far Can the Red Palm Weevil (Coleoptera: Curculionidae) Fly?: Computerized Flight Mill Studies With Field-Captured Weevils

Adult Rhynchophorus ferrugineus (Olivier) captured in pheromone-baited traps in commercial date palm orchards in the Al Ahsaa Directorate, Kingdom of Saudi Arabia, were used in computerized flight mill studies to determine the flight characteristics of this highly invasive and destructive palm pest. Flight mill studies were run at three different time periods, winter (December), spring (March), and summer (May). Of the 192 weevils tethered to flight mills ∼30% failed to fly > 1 km. Of those weevils flying > 1 km (n = 139), 55% flew > 10 km, and of these flyers 5% flew > 50 km in 24 h. Flying weevils exhibited an average weight loss of 20-30% and nonflying control weevils lost ∼9-13% body weight in 24 h. Male and female weevils flying in summer (average laboratory temperature was ∼27°C) flew the longest average distances (∼25-35 km), exhibited highest weight reductions (∼30%), and greatest mortality rates (∼80%). Consequently, time of year not weevil sex or color morph had a consistent and significant effect on flight activity, weight loss, and survivorship rates. Flight activity was predominantly diurnal commencing around 5:00 a.m. and peaking between 9-11:00 a.m. before tapering off. The distribution of flight distances combined across season and sex was mesokurtic (i.e., normally distributed).

Comparison of the potential rate of population increase of brown and green color morphs of Sitobion avenae (Homoptera: Aphididae) on barley infected and uninfected with Barley yellow dwarf virus

Life tables of brown and green color morphs of the English grain aphid, Sitobion avenae (Fabricius) reared on barley under laboratory conditions at 20 ± 1°C, 65% ± 5% relative humidity and a photoperiod of 16 : 8 h (L : D) were compared. The plants were either: (i) infected with the Barley yellow dwarf virus (BYDV); (ii) not infected with virus but previously infested with aphids; or (iii) healthy barley plants, which were not previously infested with aphids. Generally, both color morphs of S. avenae performed significantly better when fed on BYDV-infected plants than on plants that were virus free but had either not been or had been previously infested with aphids. Furthermore, when fed on BYDV-infected plants, green S. avenae developed significantly faster and had a significantly shorter reproductive period than the brown color morph. There were no significant differences in this respect between the two color morphs of S. avenae when they were reared on virus-free plants that either had been or not been previously infested with aphids. These results indicate that barley infected with BYDV is a more favorable host plant than uninfected barley for both the color morphs of S. avenae tested, particularly the green color morph.