Back to basics: using colour polymorphisms to study evolutionary processes

Abstract

Here, I suggest that colour polymorphic study systems have been underutilized to answer general questions about evolutionary processes, such as morph frequency dynamics between generations and population divergence in morph frequencies. Colour polymorphisms can be used to study fundamental evolutionary processes like frequency-dependent selection, gene flow, recombination and correlational selection for adaptive character combinations. However, many previous studies of colour polymorphism often suffer from weak connections to population genetic theory. I argue that too much focus has been directed towards noticeable visual traits (colour) at the expense of understanding the evolutionary processes shaping genetic variation and covariation associated with polymorphisms in general. There is thus no need for a specific evolutionary theory for colour polymorphisms beyond the general theory of the maintenance of polymorphisms in spatially or temporally variable environments or through positive or negative frequencydependent selection. I outline an integrative research programme incorporating these processes and suggest some fruitful avenues in future investigations of colour polymorphisms.

Dispatches from the neighborhood watch: Using citizen science and field survey data to document color morph frequency in space and time

“…The study of color polymorphisms has a long history in evolutionary biology and despite the modern availability of tools to investigate traits that cannot be readily assessed visually, we argue that studies of color polymorphism are still quite valuable in advancing our understanding of fundamental evolutionary processes (Svensson, ). Furthermore, since studies of color polymorphism can, with care, take advantage of the growing data availability from citizen science efforts, we believe such studies have a bright future.…”

Eco‐evolutionary dynamics of sexual selection and sexual conflict

“…Finally, researchers can also study sexually selected and visible genetic phenotypic polymorphisms, such as colour polymorphisms in males and/or females. Such morphs can be used as "genetic markers" for suites of other fitness-related traits that are involved in sexual selection or sexual conflict (Le Rouzic et al, 2015;Svensson, 2017;Svensson et al, 2005;Takahashi et al, 2014). Such polymorphic systems can also be used to investigate links between sexual selection, sexual conflict and evolutionary rescue in changing environments (Candolin & Heuschele, 2008;Kirkpatrick & Peischl, 2013;Svensson & Connallon, 2018).…”

“…The evolution of female polymorphism and other female defence traits against male mating harassment is therefore potentially an interesting example of how evolutionary rescue through female traits can counteract the expected decrease in population fitness due to sexual conflict (Svensson & Connallon, 2018). Whether sexually selected colour polymorphisms in general increase or decrease population fitness have recently been subject to some discussion and controversy (Bolton, Rollins, & Griffith, 2015;Forsman, 2016;Svensson, 2017).…”

Do group dynamics affect colour morph clines during a range shift?

“…Many species exhibit conspicuous colour polymorphisms, in which individuals within an interbreeding population exhibit alternative colours, which are often associated with alternative social, reproductive and ecological strategies (Sinervo & Lively, ; McKinnon & Pierotti, ; Svensson, in press). These alternative types, segregating within populations, are often highly differentiated from each other along multiple trait axes and thus represent alternatively co‐adapted trait complexes within an interbreeding population (Sinervo & Svensson, ; Lancaster et al ., ; Svensson, in press).…”