revision of chiggers of the minuta species-group (Acari: Trombiculidae:
Neotrombicula Hirst, 1925) using multivariate morphometrics
and P.B. Klimov
Systematic Parasitology, 77
(1): 55-69 (2010).
S U M M A R Y
revise chiggers belonging to the minuta-species
Neotrombicula Hirst, 1925) from the
Palaearctic using size-free multivariate morphometrics. This approach
allowed us to resolve several diagnostic problems. We show that the
Neotrombicula scrupulosa Kudryashova,
1993 forms three spatially and ecologically isolated groups different
from each other in size or shape (morphometric property) only:
specimens from the Caucasus are distinct from those from Asia in shape,
whereas the Asian specimens from plains and mountains are different
from each other in size. We developed a multivariate classification
model to separate three closely related species: N.
scrupulosa, N. lubrica Kudryashova, 1993 and N.
minuta Schluger, 1966. This model is based on five shape
variables selected from an initial 17 variables by a best subset
analysis using a custom size-correction subroutine. The variable
selection procedure slightly improved the predictive power of the
model, suggesting that it not only removed redundancy but also reduced
"noise" in the dataset. The overall classification accuracy of this
model is 96.2, 96.2 and 95.5%, as estimated by internal validation,
external validation and jackknife statistics, respectively. Our
analyses resulted in one new synonymy: N. dimidiata
Stekolnikov, 1995 is considered to be a synonym of N. lubrica.
N. scrupulosa and N. lubrica
are recorded from new localities. A key to species of the
minuta-group incorporating results from
our multivariate analyses is presented.