Here, both taxa are displayed side by side for comparison: Polyphylla alleni Cazier on the left (photo courtesy of the AMNH), and a probable undescribed species related to P. diffracta on the right. The morphological differences are fairly apparent.
For Polyphylla identification, a combination of diagnostic characters are used with distribution and ecological association sometimes being helpful. In other words, a sand dune obligate will not occur in a montane environment and vice-versa. Sand dune species have evolved a suite of morphological, behavioral, and physiological characters that adapt and restrict them to these environments. To further complicate matters, the dorsal vestiture of psammophilous Polyphylla, that is composed of fine squamae and setae, often in subtle patterns, is subject to abrasion and alteration from sand grains because of the beetle's inherent fossorial behavior. In addition, some populations may exhibit considerable phenotypic variation. Hence, a series of specimens is necessary to adequately assess the possible spectrum of variation.
One of my priorities for this summer is to locate a population of the Polyphylla, sp. aff. diffracta, above right. As stated in a prior post, salient morphological characters of the specimen strongly suggest it is associated with a sand dune environment.
A Google search found photos of a sand dune area east of the specimen's label locality in Navajo County, northcentral Arizona ...
The photo above appears a likely place to begin my search.
© Delbert La Rue 2013. All Rights Reserved.
Photo and additional field data courtesy of Greg Hupé, Nature's Vault.
So what do you think? The pattern of pubescence is different, but I know how variable that can be in this genus. Pronotal shape also seems a little different. I guess it really depends on what is the accepted range of variability in these characters for P. diffracta.
ReplyDeleteGiven that I only have the single male specimen at present, a series of both sexes of adults is needed to verify it's true taxonomic status. However, the morphological distinctions between the two are fairly evident. The current definition of P. diffracta (sensu lato) requires clarification including mtDNA analysis.
ReplyDeleteThanks, Ted, for your comments and input.