Contrasting Phenotypic Variability of Life-History Traits of Two Feral Populations of Macrolophus pygmaeus (Hemiptera: Miridae) under Two Alternative Diets

Abstract

Tuta absoluta is a major pest attacking tomato crops. This invasive species emerged in Europe (Spain) in 2006, and 3 years later it spread to Portugal. In 2009/2010, it was recorded for the first time in the Azores archipelago. Macrolophus pygmaeus is a predator widely used as biological control agent against the tomato leaf miner. This study contrasted the life-history traits and population growth parameters of two feral populations of M. pygmaeus, one from Portugal mainland and one from the Azores archipelago. The predators were tested on single prey diet, either of Ephestia kuehniella eggs, a factitious prey used for mass rearing of mirids, or T. absoluta eggs. We predicted that populations would express differences in its phenotypic characteristics, with the Azorean population displaying low performance due to likely low genetic diversity, as expected for insular populations. Our results revealed the inexistence of phenotypic differences in several life history traits, such as immature developmental time, female longevity, males’ body weight and sex ratio. Contrary to our predictions, traits with direct impact on fitness, such as lifetime fertility (95.78 ± 14.23 vs. 61.38 ± 13.52 nymphs), explain better performances for the population of the Azores. Azorean M. pygmaeus females were larger, matured earlier and reproduced at a higher rate for longer periods, than mainland females. Therefore, population growth parameters show a positive advantage for the population of the Azores, fed on T. absoluta (time required for doubling the population Azores, Ek: 8.42 ± 0.50, Ta: 5.76 ± 0.31 and mainland, Ek: 10.88 ± 1.94, Ta: 12.07 ± 3.15). Biological performance of M. pygmaeus was similar when fed with T. absoluta or E. kuehniella that could be beneficial both to optimize mass production of the predator and biological control of the pest. Our results are discussed as well in a fundamental perspective, seeking if differences in biological performance can be explained by lower genetic diversity driven by geographic isolation.