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Date of Award
Doctor of Philosophy (PhD)
Benjamin B. Normark
Joseph S. Elkington
Laura A. Katz
Entomology | Genetics
The pine-needle scale insects; Chionaspis pinifoliae and C. heterophyllae are armored scale insects (Hemiptera: Diaspididae) with extensive native ranges throughout North America. In particular, C. pinifoliae is found on almost every species in the genus Pinus. Both species are economically important pests on pines, and over a century of scientific literature has considered these as only two morphological species. The life history of scale insects suggests they may form strongly structured metapopulations, resulting in high rates of host race formation and possibly speciation. Such newly originated species are likely to be morphologically similar. The geographic distribution and host use of these two species suggests they may represent a group of species that have gone unsampled due to their broad distribution or unrecognized due to their similar morphology.
To explore the potential for species diversity in pine-needle scale insects I collected 366 individual insects from 320 localities across North America, representing 51 host species within the Pinaceae. I estimated species diversity by inferring species boundaries using genealogical concordance across allele genealogies of two nuclear loci and one mitochondrial locus. Using Maximum Likelihood allele genealogies in a majority-rule consensus to assess congruence, I conservatively detect 10 species in this group. However some of these 10 species contain morphological subgroups that conventional taxonomy would recognize as their own species. I explored alternate species delimitations using a range of species delimitation schemes based on genealogical concordance and mitochondrial divergence. I analyzed these delimitation schemes as species in a Bayesian species tree analysis, and infer that a delimitation of 26 species is the optimum scheme. This 26-species scheme also recognizes most of the aforementioned unique morphological subgroups, as species. Additionally, the genetic analyses for the above work occasionally recovered parasitoid sequences, from the 28S D2 and D3 subunits of ribosomal RNA. I included these sequences in a phylogeny of over 500 specimens from 18 of 19 families within the Chalcidoidea. I compared the phylogenetic results against a comprehensive list of parasitoids recorded from C. pinifoliae and C. heterophyllae, and find the 28s sequences indicate the parasitoid diversity utilizing these pine-feeding scale insects is much higher than previously thought.
Gwiazdowski, Rodger A, "Discovery Of Cryptic Species Diversity In North American Pine- Feeding Chionaspis Scale Insects (Hemiptera: Diaspididae)" (2011). Doctoral Dissertations 1896 - February 2014. 292.