Are mimics monophyletic? The necessity of phylogenetic hypothesis tests in character evolution

<p>Abstract</p> <p>Background</p> <p>The processes governing the origin and maintenance of mimetic phenotypes can only be understood in a phylogenetic framework. Phylogenetic estimates of evolutionary relationships can provide a context for analyses of character evolution; however, when phylogenetic estimates conflict, rigorous analyses of alternative evolutionary histories are necessary to determine the likelihood of a specific history giving rise to the observed pattern of diversity. The polyphenic butterfly <it>Limenitis arthemis </it>provides a case in point. This species is comprised of three lineages, two of which are mimetic and one of which is non-mimetic. Conflicting estimates of the relationships among these three lineages requires direct evaluation of the alternative hypotheses of mimicry evolution.</p> <p>Results</p> <p>Using a coalescent framework, we found support for a sister-taxon relationship between the non-mimetic <it>L. a. arthemis </it>and the mimetic <it>L. a. astyanax</it>, congruent with the previous hypothesis that the non-mimetic form of <it>L. a. arthemis </it>was derived from a mimetic ancestor. We found no support for a mimetic clade (<it>L. a. astyanax </it>+ <it>L. a. arizonensis</it>) despite analyzing numerous models of population structure.</p> <p>Conclusions</p> <p>These results provide the foundation for future studies of mimicry, which should integrate phylogenetic and developmental analyses of wing pattern formation. We propose future analyses of character evolution accommodate conflicting phylogenetic estimates by explicitly testing alternative evolutionary hypotheses.</p

Temporal Gene Expression Variation Associated with Eyespot Size Plasticity in Bicyclus anynana

Seasonal polyphenism demonstrates an organism\u27s ability to respond to predictable environmental variation with alternative phenotypes, each presumably better suited to its respective environment. However, the molecular mechanisms linking environmental variation to alternative phenotypes via shifts in development remain relatively unknown. Here we investigate temporal gene expression variation in the seasonally polyphenic butterfly Bicyclus anynana. This species shows drastic changes in eyespot size depending on the temperature experienced during larval development. The wet season form (larvae reared over 24°C) has large ventral wing eyespots while the dry season form (larvae reared under 19°C) has much smaller eyespots. We compared the expression of three proteins, Notch, Engrailed, and Distal-less, in the future eyespot centers of the two forms to determine if eyespot size variation is associated with heterochronic shifts in the onset of their expression. For two of these proteins, Notch and Engrailed, expression in eyespot centers occurred earlier in dry season than in wet season larvae, while Distal-less showed no temporal difference between the two forms. These results suggest that differences between dry and wet season adult wings could be due to a delay in the onset of expression of these eyespot-associated genes. Early in eyespot development, Notch and Engrailed may be functioning as repressors rather than activators of the eyespot gene network. Alternatively, temporal variation in the onset of early expressed genes between forms may have no functional consequences to eyespot size regulation and may indicate the presence of an \u27hourglass\u27 model of development in butterfly eyespots. © 2013 Oliver et al

Estimating the annual distribution of monarch butterflies in Canada over 16 years using citizen science data

Monarch butterflies (Danaus plexippus, Linnaeus, 1758) are comprised of two migratory populations separated by the Rocky Mountains and are renowned for their long-distance movements among the United States, Canada, and Mexico. Both populations have declined over several decades across North America prompting all three countries to evaluate conservation efforts. Monitoring monarch distribution and abundance is a necessary aspect of ongoing management in Canada where they are a species at risk. We used presence-only data from two citizen science data sets to estimate the annual breeding distribution of monarch butterflies in Canada between 2000 and 2015. Monarch breeding distribution in Canada varied widely among years owing to natural variation, and when considering the upper 95% of the probability of occurrence, the annual mean breeding distribution in Canada was 484 943 km(2) (min: 173 449 km(2); max: 1 425 835 km(2)). The area of occurrence was approximately an order of magnitude larger in eastern Canada than in western Canada. Habitat restoration for monarch butterflies in Canada should prioritize productive habitats in southern Ontario where monarchs occur annually and, therefore, likely contribute most to the long-term viability of monarchs in eastern North America. Overall, our assessment sets the geographic context to develop successful management strategies for monarchs in Canada.Liber Ero Postdoctoral Fellowship; University Research Chair from the University of GuelphOpen access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Differential Expression of Ecdysone Receptor Leads to Variation in Phenotypic Plasticity across Serial Homologs

Bodies are often made of repeated units, or serial homologs, that develop using the same core gene regulatory network. Local inputs and modifications to this network allow serial homologs to evolve different morphologies, but currently we do not understand which modifications allow these repeated traits to evolve different levels of phenotypic plasticity. Here we describe variation in phenotypic plasticity across serial homologous eyespots of the butterfly Bicyclus anynana, hypothesized to be under selection for similar or different functions in the wet and dry seasonal forms. Specifically, we document the presence of eyespot size and scale brightness plasticity in hindwing eyespots hypothesized to vary in function across seasons, and reduced size plasticity and absence of brightness plasticity in forewing eyespots hypothesized to have the same function across seasons. By exploring the molecular and physiological causes of this variation in plasticity across fore and hindwing serial homologs we discover that: 1) temperature experienced during the wandering stages of larval development alters titers of an ecdysteroid hormone, 20-hydroxyecdysone (20E), in the hemolymph of wet and dry seasonal forms at that stage; 2) the 20E receptor (EcR) is differentially expressed in the forewing and hindwing eyespot centers of both seasonal forms during this critical developmental stage; and 3) manipulations of EcR signaling disproportionately affected hindwing eyespots relative to forewing eyespots. We propose that differential EcR expression across forewing and hindwing eyespots at a critical stage of development explains the variation in levels of phenotypic plasticity across these serial homologues. This finding provides a novel signaling pathway, 20E, and a novel molecular candidate, EcR, for the regulation of levels of phenotypic plasticity across body parts or serial homologs

Temporal Gene Expression Variation Associated with Eyespot Size Plasticity in Bicyclus anynana

Seasonal polyphenism demonstrates an organism's ability to respond to predictable environmental variation with alternative phenotypes, each presumably better suited to its respective environment. However, the molecular mechanisms linking environmental variation to alternative phenotypes via shifts in development remain relatively unknown. Here we investigate temporal gene expression variation in the seasonally polyphenic butterfly Bicyclus anynana. This species shows drastic changes in eyespot size depending on the temperature experienced during larval development. The wet season form (larvae reared over 24 degrees C) has large ventral wing eyespots while the dry season form (larvae reared under 19 degrees C) has much smaller eyespots. We compared the expression of three proteins, Notch, Engrailed, and Distal-less, in the future eyespot centers of the two forms to determine if eyespot size variation is associated with heterochronic shifts in the onset of their expression. For two of these proteins, Notch and Engrailed, expression in eyespot centers occurred earlier in dry season than in wet season larvae, while Distal-less showed no temporal difference between the two forms. These results suggest that differences between dry and wet season adult wings could be due to a delay in the onset of expression of these eyespot-associated genes. Early in eyespot development, Notch and Engrailed may be functioning as repressors rather than activators of the eyespot gene network. Alternatively, temporal variation in the onset of early expressed genes between forms may have no functional consequences to eyespot size regulation and may indicate the presence of an 'hourglass' model of development in butterfly eyespots

Eyespots deflect predator attack increasing fitness and promoting the evolution of phenotypic plasticity

Some eyespots are thought to deflect attack away from the vulnerable body, yet there is limited empirical evidence for this function and its adaptive advantage. Here, we demonstrate the conspicuous ventral hindwing eyespots found on Bicyclus anynana butterflies protect against invertebrate predators, specifically praying mantids. Wet season (WS) butterflies with larger, brighter eyespots were easier for mantids to detect, but more difficult to capture compared to dry season (DS) butterflies with small, dull eyespots. Mantids attacked the wing eyespots of WS butterflies more frequently resulting in greater butterfly survival and reproductive success. With a reciprocal eyespot transplant, we demonstrated the fitness benefits of eyespots were independent of butterfly behaviour. Regardless of whether the butterfly was WS or DS, large marginal eyespots pasted on the hindwings increased butterfly survival and successful oviposition during predation encounters. In previous studies, DS B. anynana experienced delayed detection by vertebrate predators, but both forms suffered low survival once detected. Our results suggest predator abundance, identity and phenology may all be important selective forces for B. anynana. Thus, reciprocal selection between invertebrate and vertebrate predators across seasons may contribute to the evolution of the B. anynana polyphenism.This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by the Royal Society. The published article can be found at: http://rspb.royalsocietypublishing.org/.Keywords: adaptive coloration, wing patterns, visual signallin

Warning and Deception: Chemical, Behavioral, and Phylogenetic Studies of Aposematic Coloration and Mimicry

The study of aposematic coloration and mimicry has a long and distinguished history, and has stimulated scientific inquiry in areas as diverse as chemistry, evolution, ecology, and behavior. Yet, many questions regarding signal function and ecological dynamics remain unknown. This dissertation attempts to address some of these questions about how a visual warning signal functions and how the environment changes its efficacy. First, I evaluated the role of luminance contrast in aposematic signaling using milkweed bugs as model prey and Chinese mantids as model predators. Predators learned to avoid unpalatable prey sooner and remembered to avoid unpalatable prey for longer when the prey had higher luminance contrast with the background. These results help define what makes a visual signal conspicuous and designate the importance of high luminance contrast in the efficacy of a warning color signal. Another important characteristic of warning coloration is the reason for the advertisement. I was able to identify and quantify the toxic compounds in both the host plant and the viceroy butterfly, a putative aposematic insect. These results provide a chemical mechanism for previous research that demonstrated that the viceroy was unpalatable to avian predators. Next, I was able to test the role of geographic variation in host plant and viceroy chemical defense and how that variation compared with the local abundance of a mimicry co-model of the viceroy, the queen butterfly. The results indicated the viceroy was more chemically defended and more unpalatable in locations where the queen was at low abundances. This result suggests that mimicry evolves in a geographic mosaic of co-evolution. Finally, I used molecular phylogenetic approaches to reconstruct and test the evolution of mimicry in the North American admiral butterflies (Limenitis: Nymphalidae). One species, L. arthemis, evolved the black, pipevine swallowtail mimetic form but later reverted to the white-banded ancestral form. This character reversion is strongly correlated with the geographic absence of the model species and its host plant, not the mimics host plant distribution. These results support the idea that loss of model in a geographic area is not an evolutionary stopping point for a Batesian mimic

A new parasitoid of Danaus gilippus thersippus (Nymphalidae: Danainae) in southeastern Arizona

Volume: 59Start Page: 118End Page: 11

color pattern evolution

Multiple approaches to stud