The population genetics of pentalonia nigronervosa and p. caladii (hemiptera: aphididae) in Hawaiʻi

Abstract

Viruliferous aphids are among the most troublesome insect pests that impact agriculture worldwide. Their economic importance has led to the application of Integrated Pest Management (IPM) methods that combine cultural, chemical, and biological control strategies. Incorporating IPM for control of aphids in agricultural and conservation systems has made underscored the need for understanding the biology and ecology of aphid species. Population genetics offers tools to understand the biology and ecology of aphids at the molecular level in ways that complement field studies by confirming reproduction strategies, investigating host plant adaptation, determining genetic variation, insecticide resistance, ability to vector plant pathogens and revealing dispersal and geographic range. In this thesis, the genetic diversity and population genetic structure of two Pentalonia aphids, Pentalonia nigronervosa and P. caladii were investigated in Hawaii. Existing microsatellite primers, developed from two related aphid species, Aphis gossypii and Myzus persicae were employed to identify molecular markers for Pentalonia species through cross-species amplification. Genetic analysis showed that population genetic structure exists among and between populations of P. nigronervosa and P. caladii. The inferred genetic differentiation between and within taxa was correlated with host plant differences. In addition, aphid populations were also structured according to island within host plant groups. The observed genetic structuring refutes a commonly held belief that there is no population-based differentiation of parthenogenetic aphids in Hawaii. Pentalonia caladii showed medium population differentiation from P. nigronervosa using F-statistics analysis, an indication of genetically diverging populations. The analysis of genetic variation and structure confirmed that P. nigronervosa and P. caladii are separate and distinct species. Excess in heterozygosity between taxa confirmed that aphids in Hawaii reproduce primarily asexually.