Measurement of Sexual Isolation and Selective Mating

Simulating natural conditions in the laboratory poses one of the most significant challenges to behavioral studies. Some authors have argued that laboratory "choice" experiments reflect mate choice in nature more accurately than "no-choice" experiments. A recent choice experiment study questioned the conclusions of several earlier studies by failing to detect a published difference in sexual isolation between populations of Drosophila pseudoobscura, and suggested their result was more robust because of the more realistic design. Here, we re-examine the methods and analyses of this recent study, and we find there was indeed a difference in sexual isolation between populations of D. pseudoobscura. We also conduct a more rigorously controlled choice experiment and, in agreement with previous studies, note that D. pseudoobscura females from populations sympatric to their sibling species, D. persimilis, exhibit greater sexual isolation than those from allopatric populations. Our results confirm the existence of a geographic pattern in sexual isolation in D. pseudoobscura, and we discuss differences in experimental designs in light of the biology of this species.

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“…They then calculated a ''joint isolation index'' for both sexes and both species (Merrell, 1950) to measure sexual isolation:…”

Section: Reanalysis Of Anderson and Kim (2005) Resultsmentioning

confidence: 99%

Simulating Natural Conditions in the Laboratory: A Re-Examination of Sexual Isolation between Sympatric and Allopatric Populations of Drosophila pseudoobscura and D. persimilis

Noor

Ortiz‐Barrientos

2006

Behav Genet

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“…A major criticism of the joint isolation index (I) is its poor statistical estimation properties due to uncorrected marginal effects (Merrell 1950;Gilbert and Starmer 1985;Rolán-Alvarez and Caballero 2000). Rolán-Alvarez and Caballero (2000) defined a new index, I PSI , using a pair sexual isolation (PSI) statistic which estimates mate choice coefficients for each type of mating pair.…”

Section: Statistical Analyzes Of Mating Behaviormentioning

confidence: 99%

“…We first tested for random mating between the strains using a 2 9 2 contingency Chi-square test. We calculated two kinds of isolation index: I, the joint isolation index (Merrell 1950;Malogolowkin-Cohen et al 1965) and I PSI , the isolation index utilizing the PSI coefficients of Rolán-Alvarez and Caballero (2000). We have indicated values of the isolation indices that differ significantly from zero using the standard error derived by Malogolowkin-Cohen et al (1965), and values of I PSI that differ significantly from zero using the JMATING software of Carvajal-Rodriguez and Rolán-Alvarez (2006).…”

Section: Sexual Isolation Between Geographic Strains Of D Pseudoobscuramentioning

confidence: 99%

Sexual isolation between North American and Bogota strains of Drosophila pseudoobscura

et al. 2011

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Sexual isolation, the reduced ability of organisms of different species to successfully mate, is one of the reproductive barriers that prevent gene flow between different taxa. Various species-specific signals during courtship are attributed to the sexual isolation between them. Drosophila pseudoobscura has been widely used to study the behavioral and genetic mechanisms underlying selection for sexual isolation, as a model system for speciation. D. pseudoobscura and its sibling species, D. persmilis, live together in many locations but are reproductively isolated from one another. North American geographic strains of D. pseudoobscura from the American West mate at random. Several decades ago, D. pseudoobscura was collected in the vicinity of Bogota, Colombia, and later named the subspecies D. pseudoobscura bogotana. Nearly 5,000 matings were observed in this study. We analyzed mating behavior and cuticular hydrocarbon profiles as well as courtship within and between North American and Bogota strains of D. pseudoobscura. Here we report for the first time that Bogota strains of D. pseudoobscura do show statistically significant sexual isolation from North American strains. In addition, there are quantitative variations in cuticular hydrocarbons as well as in courtship behavior between Bogota and North American strains, and females of both North American and Bogota strains show strong preference for North American strain males having high mating propensities, suggesting that the Bogota strains are at an early stage that could lead to a separate species.

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“…In analogy with the 'isolation estimate', 'female mating ratio', and 'male mating ratio' of Merrell (1950), we have compared the following regression lines: (1) homogamic and heterogamic matings (in this special case, N is always 30, for all the assayed relative frequencies), (2) matings of females of both types in competition, (3) matings of males of both types. Tables 1 to 8 give also, in C, the K coefficients for males and for females, with their standard errors (SEM), calculated according to Petit and Ehrman (1968).…”

Section: Resultsmentioning

confidence: 99%