Morphological variation and mating compatibility within the mealybugs Pseudococcus calceolariae and P. similans (Hemiptera: Pseudococcidae), and a new synonymy

Abstract

Summary A laboratory study of isolines of Pseudococcus calceolariae (Maskell) and P. similans (Lidgett) collected from Hawke's Bay and Auckland, two widely separated regions in the North Island of New Zealand, threw doubt on the validity of the defining characters of these species. For P. similans, the number and position of oral rim tubular ducts varied widely and sometimes fell outside the defined limits for the species, and characteristic ‘stout abdominal setae’ were lost in the F1 generation. The morphological characters that separate one species from the other were manipulated by changing the temperature at which the mealybugs developed, such that cohorts of F1 sisters reared in the laboratory contained phenotypes of both P. calceolariae and P. similans. No impediments were found to breeding among populations of P. calceolariae and P. similans from Hawke's Bay and Auckland. All combinations of crosses between virgin females and males produced viable progeny. Those reared at 16°C laid more eggs than those reared at 23°C. The data did not suggest the existence of cryptic or sibling species, and contrasted with experiments elsewhere which quite clearly showed species incompatibility of closely related mealybugs. Examination of 160 ‘wild’ specimens of P. calceolariae from New Zealand, Australia and California (U.S.A.) and P. similans from New Zealand and Australia showed a morphological continuum from one species to the other. It is concluded that P. calceolariae and P. similans merely represent the phenotypic extremes of one widely polymorphic species, with the morphological characters of individual adults determined by the microenvironment in which they developed. Pseudococcus calceolariae is thus the senior synonym of P. similans.

Influence of different plants substrates on development and reproduction for laboratory rearing of Pseudococcus calceolariae (Maskell) (Hemiptera: Pseudococcidae)

“…The morphological analysis revealed that the phenotype of P. calceolariae used in this study corresponds to the most common one present in Australia and new Zealand, as the four parameters measured were well within the range reported for this phenotype (Cox, 1987;Williams, 1985), and were different from the phenotype described originally as P. similans and later synonymized with P. calceolariae (Charles et al, 2000) (Table 1).…”

“…For identification of the phenotype, the following characters were determined according to Charles et al (2000): length of tibia plus tarsus of hindlegs, combined length of trochanter and femur of hindlegs, ratio hind tibia:tarsus and number of oral rim tubular ducts. Distances were measured by calibrating digital photographs taken at a magnification of 20x (Micropublisher 3.3 RTV, Qimaging, Burnaby, BC, Canada) with a known standard (100 um = 252 pixels), using the software Image J 1.40 (http://rsb.info.nih.…”

Evidence for Gene Flow between Two Sympatric Mealybug Species (Insecta; Coccoidea; Pseudococcidae)

“…Among the scale insects (Coccoidea), laboratory-induced inter-species hybrids have been observed in the mealybug family (Pseudococcidae) [19], [20], [21], [22], [48].…”

Phylogenetic analysis of mealybugs (Hemiptera: Coccoidea: Pseudococcidae) based on DNA sequences from three nuclear genes, and a review of the higher classification

“…Efforts to generate phylogenetic hypotheses for the family are confounded by a paucity of useful morphological characters in adult females as a result of reduction (Ferris, 1950; Cox, 1987), substantial intraspecific polymorphism in some species (Danzig, 1980; Cox, 1987), and environmental influences on morphology affecting character states of the wax ducts and pores (Cox, 1983; Charles et al ., 2000), as well as other features deemed useful in identification. Also, significant electrophoretic differences have been detected among collections of mealybugs which were considered to be one species based on morphology (Nur, 1977).…”